/************************************************* * Exim - an Internet mail transport agent * *************************************************/ /* Copyright (c) University of Cambridge 1995 - 2019 */ /* See the file NOTICE for conditions of use and distribution. */ /* Portions Copyright (c) The OpenSSL Project 1999 */ /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL library. It is #included into the tls.c file when that library is used. The code herein is based on a patch that was originally contributed by Steve Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara. No cryptographic code is included in Exim. All this module does is to call functions from the OpenSSL library. */ /* Heading stuff */ #include #include #include #include #ifndef OPENSSL_NO_ECDH # include #endif #ifndef DISABLE_OCSP # include #endif #ifdef SUPPORT_DANE # include "danessl.h" #endif #ifndef DISABLE_OCSP # define EXIM_OCSP_SKEW_SECONDS (300L) # define EXIM_OCSP_MAX_AGE (-1L) #endif #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT) # define EXIM_HAVE_OPENSSL_TLSEXT #endif #if OPENSSL_VERSION_NUMBER >= 0x00908000L # define EXIM_HAVE_RSA_GENKEY_EX #endif #if OPENSSL_VERSION_NUMBER >= 0x10100000L # define EXIM_HAVE_OCSP_RESP_COUNT # define OPENSSL_AUTO_SHA256 #else # define EXIM_HAVE_EPHEM_RSA_KEX # define EXIM_HAVE_RAND_PSEUDO #endif #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256) # define EXIM_HAVE_SHA256 #endif /* X509_check_host provides sane certificate hostname checking, but was added to OpenSSL late, after other projects forked off the code-base. So in addition to guarding against the base version number, beware that LibreSSL does not (at this time) support this function. If LibreSSL gains a different API, perhaps via libtls, then we'll probably opt to disentangle and ask a LibreSSL user to provide glue for a third crypto provider for libtls instead of continuing to tie the OpenSSL glue into even twistier knots. If LibreSSL gains the same API, we can just change this guard and punt the issue for a while longer. */ #ifndef LIBRESSL_VERSION_NUMBER # if OPENSSL_VERSION_NUMBER >= 0x010100000L # define EXIM_HAVE_OPENSSL_CHECKHOST # define EXIM_HAVE_OPENSSL_DH_BITS # define EXIM_HAVE_OPENSSL_TLS_METHOD # define EXIM_HAVE_OPENSSL_KEYLOG # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID # define EXIM_HAVE_SESSION_TICKET # define EXIM_HAVE_OPESSL_TRACE # define EXIM_HAVE_OPESSL_GET0_SERIAL # ifndef DISABLE_OCSP # define EXIM_HAVE_OCSP # endif # else # define EXIM_NEED_OPENSSL_INIT # endif # if OPENSSL_VERSION_NUMBER >= 0x010000000L \ && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L # define EXIM_HAVE_OPENSSL_CHECKHOST # endif #endif #if !defined(LIBRESSL_VERSION_NUMBER) \ || LIBRESSL_VERSION_NUMBER >= 0x20010000L # if !defined(OPENSSL_NO_ECDH) # if OPENSSL_VERSION_NUMBER >= 0x0090800fL # define EXIM_HAVE_ECDH # endif # if OPENSSL_VERSION_NUMBER >= 0x10002000L # define EXIM_HAVE_OPENSSL_EC_NIST2NID # endif # endif #endif #ifndef LIBRESSL_VERSION_NUMBER # if OPENSSL_VERSION_NUMBER >= 0x010101000L # define OPENSSL_HAVE_KEYLOG_CB # define OPENSSL_HAVE_NUM_TICKETS # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME # else # define OPENSSL_BAD_SRVR_OURCERT # endif #endif #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP) # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile" # define DISABLE_OCSP #endif #ifdef EXPERIMENTAL_TLS_RESUME # if OPENSSL_VERSION_NUMBER < 0x0101010L # error OpenSSL version too old for session-resumption # endif #endif #ifdef EXIM_HAVE_OPENSSL_CHECKHOST # include #endif #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID # define SSL_CIPHER_get_id(c) (c->id) # endif # ifndef MACRO_PREDEF # include "tls-cipher-stdname.c" # endif #endif /************************************************* * OpenSSL option parse * *************************************************/ typedef struct exim_openssl_option { uschar *name; long value; } exim_openssl_option; /* We could use a macro to expand, but we need the ifdef and not all the options document which version they were introduced in. Policylet: include all options unless explicitly for DTLS, let the administrator choose which to apply. This list is current as of: ==> 1.1.1c <== XXX could we autobuild this list, as with predefined-macros? Seems just parsing ssl.h for SSL_OP_.* would be enough (except to exclude DTLS). Also allow a numeric literal? */ static exim_openssl_option exim_openssl_options[] = { /* KEEP SORTED ALPHABETICALLY! */ #ifdef SSL_OP_ALL { US"all", (long) SSL_OP_ALL }, #endif #ifdef SSL_OP_ALLOW_NO_DHE_KEX { US"allow_no_dhe_kex", SSL_OP_ALLOW_NO_DHE_KEX }, #endif #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION }, #endif #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE }, #endif #ifdef SSL_OP_CRYPTOPRO_TLSEXT_BUG { US"cryptopro_tlsext_bug", SSL_OP_CRYPTOPRO_TLSEXT_BUG }, #endif #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS }, #endif #ifdef SSL_OP_ENABLE_MIDDLEBOX_COMPAT { US"enable_middlebox_compat", SSL_OP_ENABLE_MIDDLEBOX_COMPAT }, #endif #ifdef SSL_OP_EPHEMERAL_RSA { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA }, #endif #ifdef SSL_OP_LEGACY_SERVER_CONNECT { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT }, #endif #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER }, #endif #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG }, #endif #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING }, #endif #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG }, #endif #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG }, #endif #ifdef SSL_OP_NO_ANTI_REPLAY { US"no_anti_replay", SSL_OP_NO_ANTI_REPLAY }, #endif #ifdef SSL_OP_NO_COMPRESSION { US"no_compression", SSL_OP_NO_COMPRESSION }, #endif #ifdef SSL_OP_NO_ENCRYPT_THEN_MAC { US"no_encrypt_then_mac", SSL_OP_NO_ENCRYPT_THEN_MAC }, #endif #ifdef SSL_OP_NO_RENEGOTIATION { US"no_renegotiation", SSL_OP_NO_RENEGOTIATION }, #endif #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION }, #endif #ifdef SSL_OP_NO_SSLv2 { US"no_sslv2", SSL_OP_NO_SSLv2 }, #endif #ifdef SSL_OP_NO_SSLv3 { US"no_sslv3", SSL_OP_NO_SSLv3 }, #endif #ifdef SSL_OP_NO_TICKET { US"no_ticket", SSL_OP_NO_TICKET }, #endif #ifdef SSL_OP_NO_TLSv1 { US"no_tlsv1", SSL_OP_NO_TLSv1 }, #endif #ifdef SSL_OP_NO_TLSv1_1 #if SSL_OP_NO_TLSv1_1 == 0x00000400L /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */ #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring #else { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 }, #endif #endif #ifdef SSL_OP_NO_TLSv1_2 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 }, #endif #ifdef SSL_OP_NO_TLSv1_3 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 }, #endif #ifdef SSL_OP_PRIORITIZE_CHACHA { US"prioritize_chacha", SSL_OP_PRIORITIZE_CHACHA }, #endif #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG }, #endif #ifdef SSL_OP_SINGLE_DH_USE { US"single_dh_use", SSL_OP_SINGLE_DH_USE }, #endif #ifdef SSL_OP_SINGLE_ECDH_USE { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE }, #endif #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG }, #endif #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG }, #endif #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG }, #endif #ifdef SSL_OP_TLS_D5_BUG { US"tls_d5_bug", SSL_OP_TLS_D5_BUG }, #endif #ifdef SSL_OP_TLS_ROLLBACK_BUG { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG }, #endif #ifdef SSL_OP_TLSEXT_PADDING { US"tlsext_padding", SSL_OP_TLSEXT_PADDING }, #endif }; #ifndef MACRO_PREDEF static int exim_openssl_options_size = nelem(exim_openssl_options); #endif #ifdef MACRO_PREDEF void options_tls(void) { uschar buf[64]; for (struct exim_openssl_option * o = exim_openssl_options; o < exim_openssl_options + nelem(exim_openssl_options); o++) { /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */ spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name); builtin_macro_create(buf); } # ifdef EXPERIMENTAL_TLS_RESUME builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING ); # endif # ifdef SSL_OP_NO_TLSv1_3 builtin_macro_create(US"_HAVE_TLS1_3"); # endif # ifdef OPENSSL_BAD_SRVR_OURCERT builtin_macro_create(US"_TLS_BAD_MULTICERT_IN_OURCERT"); # endif # ifdef EXIM_HAVE_OCSP builtin_macro_create(US"_HAVE_TLS_OCSP"); builtin_macro_create(US"_HAVE_TLS_OCSP_LIST"); # endif } #else /******************************************************************************/ /* Structure for collecting random data for seeding. */ typedef struct randstuff { struct timeval tv; pid_t p; } randstuff; /* Local static variables */ static BOOL client_verify_callback_called = FALSE; static BOOL server_verify_callback_called = FALSE; static const uschar *sid_ctx = US"exim"; /* We have three different contexts to care about. Simple case: client, `client_ctx` As a client, we can be doing a callout or cut-through delivery while receiving a message. So we have a client context, which should have options initialised from the SMTP Transport. We may also concurrently want to make TLS connections to utility daemons, so client-contexts are allocated and passed around in call args rather than using a gobal. Server: There are two cases: with and without ServerNameIndication from the client. Given TLS SNI, we can be using different keys, certs and various other configuration settings, because they're re-expanded with $tls_sni set. This allows vhosting with TLS. This SNI is sent in the handshake. A client might not send SNI, so we need a fallback, and an initial setup too. So as a server, we start out using `server_ctx`. If SNI is sent by the client, then we as server, mid-negotiation, try to clone `server_sni` from `server_ctx` and then initialise settings by re-expanding configuration. */ typedef struct { SSL_CTX * ctx; SSL * ssl; gstring * corked; } exim_openssl_client_tls_ctx; static SSL_CTX *server_ctx = NULL; static SSL *server_ssl = NULL; #ifdef EXIM_HAVE_OPENSSL_TLSEXT static SSL_CTX *server_sni = NULL; #endif static char ssl_errstring[256]; static int ssl_session_timeout = 7200; /* Two hours */ static BOOL client_verify_optional = FALSE; static BOOL server_verify_optional = FALSE; static BOOL reexpand_tls_files_for_sni = FALSE; typedef struct ocsp_resp { struct ocsp_resp * next; OCSP_RESPONSE * resp; } ocsp_resplist; typedef struct tls_ext_ctx_cb { tls_support * tlsp; uschar *certificate; uschar *privatekey; BOOL is_server; #ifndef DISABLE_OCSP STACK_OF(X509) *verify_stack; /* chain for verifying the proof */ union { struct { uschar *file; const uschar *file_expanded; ocsp_resplist *olist; } server; struct { X509_STORE *verify_store; /* non-null if status requested */ BOOL verify_required; } client; } u_ocsp; #endif uschar *dhparam; /* these are cached from first expand */ uschar *server_cipher_list; /* only passed down to tls_error: */ host_item *host; const uschar * verify_cert_hostnames; #ifndef DISABLE_EVENT uschar * event_action; #endif } tls_ext_ctx_cb; /* should figure out a cleanup of API to handle state preserved per implementation, for various reasons, which can be void * in the APIs. For now, we hack around it. */ tls_ext_ctx_cb *client_static_cbinfo = NULL; /*XXX should not use static; multiple concurrent clients! */ tls_ext_ctx_cb *server_static_cbinfo = NULL; static int setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr ); /* Callbacks */ #ifdef EXIM_HAVE_OPENSSL_TLSEXT static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg); #endif #ifndef DISABLE_OCSP static int tls_server_stapling_cb(SSL *s, void *arg); #endif /* Daemon-called, before every connection, key create/rotate */ #ifdef EXPERIMENTAL_TLS_RESUME static void tk_init(void); static int tls_exdata_idx = -1; #endif void tls_daemon_init(void) { #ifdef EXPERIMENTAL_TLS_RESUME tk_init(); #endif return; } /************************************************* * Handle TLS error * *************************************************/ /* Called from lots of places when errors occur before actually starting to do the TLS handshake, that is, while the session is still in clear. Always returns DEFER for a server and FAIL for a client so that most calls can use "return tls_error(...)" to do this processing and then give an appropriate return. A single function is used for both server and client, because it is called from some shared functions. Argument: prefix text to include in the logged error host NULL if setting up a server; the connected host if setting up a client msg error message or NULL if we should ask OpenSSL errstr pointer to output error message Returns: OK/DEFER/FAIL */ static int tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr) { if (!msg) { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); msg = US ssl_errstring; } msg = string_sprintf("(%s): %s", prefix, msg); DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg); if (errstr) *errstr = msg; return host ? FAIL : DEFER; } /************************************************* * Callback to generate RSA key * *************************************************/ /* Arguments: s SSL connection (not used) export not used keylength keylength Returns: pointer to generated key */ static RSA * rsa_callback(SSL *s, int export, int keylength) { RSA *rsa_key; #ifdef EXIM_HAVE_RSA_GENKEY_EX BIGNUM *bn = BN_new(); #endif export = export; /* Shut picky compilers up */ DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); #ifdef EXIM_HAVE_RSA_GENKEY_EX if ( !BN_set_word(bn, (unsigned long)RSA_F4) || !(rsa_key = RSA_new()) || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL) ) #else if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL))) #endif { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", ssl_errstring); return NULL; } return rsa_key; } /* Extreme debug #ifndef DISABLE_OCSP void x509_store_dump_cert_s_names(X509_STORE * store) { STACK_OF(X509_OBJECT) * roots= store->objs; static uschar name[256]; for (int i= 0; i < sk_X509_OBJECT_num(roots); i++) { X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i); if(tmp_obj->type == X509_LU_X509) { X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509); if (X509_NAME_oneline(sn, CS name, sizeof(name))) { name[sizeof(name)-1] = '\0'; debug_printf(" %s\n", name); } } } } #endif */ #ifndef DISABLE_EVENT static int verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn, BOOL *calledp, const BOOL *optionalp, const uschar * what) { uschar * ev; uschar * yield; X509 * old_cert; ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action; if (ev) { DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth); old_cert = tlsp->peercert; tlsp->peercert = X509_dup(cert); /* NB we do not bother setting peerdn */ if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth)))) { log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: " "depth=%d cert=%s: %s", tlsp == &tls_out ? deliver_host_address : sender_host_address, what, depth, dn, yield); *calledp = TRUE; if (!*optionalp) { if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */ return 1; /* reject (leaving peercert set) */ } DEBUG(D_tls) debug_printf("Event-action verify failure overridden " "(host in tls_try_verify_hosts)\n"); tlsp->verify_override = TRUE; } X509_free(tlsp->peercert); tlsp->peercert = old_cert; } return 0; } #endif /************************************************* * Callback for verification * *************************************************/ /* The SSL library does certificate verification if set up to do so. This callback has the current yes/no state is in "state". If verification succeeded, we set the certificate-verified flag. If verification failed, what happens depends on whether the client is required to present a verifiable certificate or not. If verification is optional, we change the state to yes, but still log the verification error. For some reason (it really would help to have proper documentation of OpenSSL), this callback function then gets called again, this time with state = 1. We must take care not to set the private verified flag on the second time through. Note: this function is not called if the client fails to present a certificate when asked. We get here only if a certificate has been received. Handling of optional verification for this case is done when requesting SSL to verify, by setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. May be called multiple times for different issues with a certificate, even for a given "depth" in the certificate chain. Arguments: preverify_ok current yes/no state as 1/0 x509ctx certificate information. tlsp per-direction (client vs. server) support data calledp has-been-called flag optionalp verification-is-optional flag Returns: 0 if verification should fail, otherwise 1 */ static int verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx, tls_support * tlsp, BOOL * calledp, BOOL * optionalp) { X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx); int depth = X509_STORE_CTX_get_error_depth(x509ctx); uschar dn[256]; if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn))) { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error", tlsp == &tls_out ? deliver_host_address : sender_host_address); return 0; } dn[sizeof(dn)-1] = '\0'; tlsp->verify_override = FALSE; if (preverify_ok == 0) { uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])", *verify_mode, sender_host_address) : US""; log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s", tlsp == &tls_out ? deliver_host_address : sender_host_address, extra, depth, X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn); *calledp = TRUE; if (!*optionalp) { if (!tlsp->peercert) tlsp->peercert = X509_dup(cert); /* record failing cert */ return 0; /* reject */ } DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " "tls_try_verify_hosts)\n"); tlsp->verify_override = TRUE; } else if (depth != 0) { DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn); #ifndef DISABLE_OCSP if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store) { /* client, wanting stapling */ /* Add the server cert's signing chain as the one for the verification of the OCSP stapled information. */ if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store, cert)) ERR_clear_error(); sk_X509_push(client_static_cbinfo->verify_stack, cert); } #endif #ifndef DISABLE_EVENT if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL")) return 0; /* reject, with peercert set */ #endif } else { const uschar * verify_cert_hostnames; if ( tlsp == &tls_out && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames))) /* client, wanting hostname check */ { #ifdef EXIM_HAVE_OPENSSL_CHECKHOST # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0 # endif # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0 # endif int sep = 0; const uschar * list = verify_cert_hostnames; uschar * name; int rc; while ((name = string_nextinlist(&list, &sep, NULL, 0))) if ((rc = X509_check_host(cert, CCS name, 0, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS, NULL))) { if (rc < 0) { log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error", tlsp == &tls_out ? deliver_host_address : sender_host_address); name = NULL; } break; } if (!name) #else if (!tls_is_name_for_cert(verify_cert_hostnames, cert)) #endif { uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])", *verify_mode, sender_host_address) : US""; log_write(0, LOG_MAIN, "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"", tlsp == &tls_out ? deliver_host_address : sender_host_address, extra, dn, verify_cert_hostnames); *calledp = TRUE; if (!*optionalp) { if (!tlsp->peercert) tlsp->peercert = X509_dup(cert); /* record failing cert */ return 0; /* reject */ } DEBUG(D_tls) debug_printf("SSL verify name failure overridden (host in " "tls_try_verify_hosts)\n"); tlsp->verify_override = TRUE; } } #ifndef DISABLE_EVENT if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL")) return 0; /* reject, with peercert set */ #endif DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n", *calledp ? "" : " authenticated", dn); *calledp = TRUE; } return 1; /* accept, at least for this level */ } static int verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx) { return verify_callback(preverify_ok, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional); } static int verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx) { return verify_callback(preverify_ok, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional); } #ifdef SUPPORT_DANE /* This gets called *by* the dane library verify callback, which interposes itself. */ static int verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx) { X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx); uschar dn[256]; int depth = X509_STORE_CTX_get_error_depth(x509ctx); #ifndef DISABLE_EVENT BOOL dummy_called, optional = FALSE; #endif if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn))) { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error", deliver_host_address); return 0; } dn[sizeof(dn)-1] = '\0'; DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n", preverify_ok ? "ok":"BAD", depth, dn); #ifndef DISABLE_EVENT if (verify_event(&tls_out, cert, depth, dn, &dummy_called, &optional, US"DANE")) return 0; /* reject, with peercert set */ #endif if (preverify_ok == 1) { tls_out.dane_verified = TRUE; #ifndef DISABLE_OCSP if (client_static_cbinfo->u_ocsp.client.verify_store) { /* client, wanting stapling */ /* Add the server cert's signing chain as the one for the verification of the OCSP stapled information. */ if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store, cert)) ERR_clear_error(); sk_X509_push(client_static_cbinfo->verify_stack, cert); } #endif } else { int err = X509_STORE_CTX_get_error(x509ctx); DEBUG(D_tls) debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err)); if (err == X509_V_ERR_APPLICATION_VERIFICATION) preverify_ok = 1; } return preverify_ok; } #endif /*SUPPORT_DANE*/ /************************************************* * Information callback * *************************************************/ /* The SSL library functions call this from time to time to indicate what they are doing. We copy the string to the debugging output when TLS debugging has been requested. Arguments: s the SSL connection where ret Returns: nothing */ static void info_callback(SSL *s, int where, int ret) { DEBUG(D_tls) { const uschar * str; if (where & SSL_ST_CONNECT) str = US"SSL_connect"; else if (where & SSL_ST_ACCEPT) str = US"SSL_accept"; else str = US"SSL info (undefined)"; if (where & SSL_CB_LOOP) debug_printf("%s: %s\n", str, SSL_state_string_long(s)); else if (where & SSL_CB_ALERT) debug_printf("SSL3 alert %s:%s:%s\n", str = where & SSL_CB_READ ? US"read" : US"write", SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret)); else if (where & SSL_CB_EXIT) if (ret == 0) debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s)); else if (ret < 0) debug_printf("%s: error in %s\n", str, SSL_state_string_long(s)); else if (where & SSL_CB_HANDSHAKE_START) debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s)); else if (where & SSL_CB_HANDSHAKE_DONE) debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s)); } } #ifdef OPENSSL_HAVE_KEYLOG_CB static void keylog_callback(const SSL *ssl, const char *line) { char * filename; FILE * fp; DEBUG(D_tls) debug_printf("%.200s\n", line); if (!(filename = getenv("SSLKEYLOGFILE"))) return; if (!(fp = fopen(filename, "a"))) return; fprintf(fp, "%s\n", line); fclose(fp); } #endif #ifdef EXPERIMENTAL_TLS_RESUME /* Manage the keysets used for encrypting the session tickets, on the server. */ typedef struct { /* Session ticket encryption key */ uschar name[16]; const EVP_CIPHER * aes_cipher; uschar aes_key[32]; /* size needed depends on cipher. aes_128 implies 128/8 = 16? */ const EVP_MD * hmac_hash; uschar hmac_key[16]; time_t renew; time_t expire; } exim_stek; static exim_stek exim_tk; /* current key */ static exim_stek exim_tk_old; /* previous key */ static void tk_init(void) { time_t t = time(NULL); if (exim_tk.name[0]) { if (exim_tk.renew >= t) return; exim_tk_old = exim_tk; } if (f.running_in_test_harness) ssl_session_timeout = 6; DEBUG(D_tls) debug_printf("OpenSSL: %s STEK\n", exim_tk.name[0] ? "rotating" : "creating"); if (RAND_bytes(exim_tk.aes_key, sizeof(exim_tk.aes_key)) <= 0) return; if (RAND_bytes(exim_tk.hmac_key, sizeof(exim_tk.hmac_key)) <= 0) return; if (RAND_bytes(exim_tk.name+1, sizeof(exim_tk.name)-1) <= 0) return; exim_tk.name[0] = 'E'; exim_tk.aes_cipher = EVP_aes_256_cbc(); exim_tk.hmac_hash = EVP_sha256(); exim_tk.expire = t + ssl_session_timeout; exim_tk.renew = t + ssl_session_timeout/2; } static exim_stek * tk_current(void) { if (!exim_tk.name[0]) return NULL; return &exim_tk; } static exim_stek * tk_find(const uschar * name) { return memcmp(name, exim_tk.name, sizeof(exim_tk.name)) == 0 ? &exim_tk : memcmp(name, exim_tk_old.name, sizeof(exim_tk_old.name)) == 0 ? &exim_tk_old : NULL; } /* Callback for session tickets, on server */ static int ticket_key_callback(SSL * ssl, uschar key_name[16], uschar * iv, EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int enc) { tls_support * tlsp = server_static_cbinfo->tlsp; exim_stek * key; if (enc) { DEBUG(D_tls) debug_printf("ticket_key_callback: create new session\n"); tlsp->resumption |= RESUME_CLIENT_REQUESTED; if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0) return -1; /* insufficient random */ if (!(key = tk_current())) /* current key doesn't exist or isn't valid */ return 0; /* key couldn't be created */ memcpy(key_name, key->name, 16); DEBUG(D_tls) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - time(NULL)); /*XXX will want these dependent on the ssl session strength */ HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key), key->hmac_hash, NULL); EVP_EncryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv); DEBUG(D_tls) debug_printf("ticket created\n"); return 1; } else { time_t now = time(NULL); DEBUG(D_tls) debug_printf("ticket_key_callback: retrieve session\n"); tlsp->resumption |= RESUME_CLIENT_SUGGESTED; if (!(key = tk_find(key_name)) || key->expire < now) { DEBUG(D_tls) { debug_printf("ticket not usable (%s)\n", key ? "expired" : "not found"); if (key) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - now); } return 0; } HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key), key->hmac_hash, NULL); EVP_DecryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv); DEBUG(D_tls) debug_printf("ticket usable, STEK expire " TIME_T_FMT "\n", key->expire - now); /* The ticket lifetime and renewal are the same as the STEK lifetime and renewal, which is overenthusiastic. A factor of, say, 3x longer STEK would be better. To do that we'd have to encode ticket lifetime in the name as we don't yet see the restored session. Could check posthandshake for TLS1.3 and trigger a new ticket then, but cannot do that for TLS1.2 */ return key->renew < now ? 2 : 1; } } #endif /************************************************* * Initialize for DH * *************************************************/ /* If dhparam is set, expand it, and load up the parameters for DH encryption. Arguments: sctx The current SSL CTX (inbound or outbound) dhparam DH parameter file or fixed parameter identity string host connected host, if client; NULL if server errstr error string pointer Returns: TRUE if OK (nothing to set up, or setup worked) */ static BOOL init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr) { BIO *bio; DH *dh; uschar *dhexpanded; const char *pem; int dh_bitsize; if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr)) return FALSE; if (!dhexpanded || !*dhexpanded) bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1); else if (dhexpanded[0] == '/') { if (!(bio = BIO_new_file(CS dhexpanded, "r"))) { tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), host, US strerror(errno), errstr); return FALSE; } } else { if (Ustrcmp(dhexpanded, "none") == 0) { DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); return TRUE; } if (!(pem = std_dh_prime_named(dhexpanded))) { tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded), host, US strerror(errno), errstr); return FALSE; } bio = BIO_new_mem_buf(CS pem, -1); } if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL))) { BIO_free(bio); tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded), host, NULL, errstr); return FALSE; } /* note: our default limit of 2236 is not a multiple of 8; the limit comes from * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with * 2236. But older OpenSSL can only report in bytes (octets), not bits. * If someone wants to dance at the edge, then they can raise the limit or use * current libraries. */ #ifdef EXIM_HAVE_OPENSSL_DH_BITS /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */ dh_bitsize = DH_bits(dh); #else dh_bitsize = 8 * DH_size(dh); #endif /* Even if it is larger, we silently return success rather than cause things * to fail out, so that a too-large DH will not knock out all TLS; it's a * debatable choice. */ if (dh_bitsize > tls_dh_max_bits) { DEBUG(D_tls) debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n", dh_bitsize, tls_dh_max_bits); } else { SSL_CTX_set_tmp_dh(sctx, dh); DEBUG(D_tls) debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n", dhexpanded ? dhexpanded : US"default", dh_bitsize); } DH_free(dh); BIO_free(bio); return TRUE; } /************************************************* * Initialize for ECDH * *************************************************/ /* Load parameters for ECDH encryption. For now, we stick to NIST P-256 because: it's simple and easy to configure; it avoids any patent issues that might bite redistributors; despite events in the news and concerns over curve choices, we're not cryptographers, we're not pretending to be, and this is "good enough" to be better than no support, protecting against most adversaries. Given another year or two, there might be sufficient clarity about a "right" way forward to let us make an informed decision, instead of a knee-jerk reaction. Longer-term, we should look at supporting both various named curves and external files generated with "openssl ecparam", much as we do for init_dh(). We should also support "none" as a value, to explicitly avoid initialisation. Patches welcome. Arguments: sctx The current SSL CTX (inbound or outbound) host connected host, if client; NULL if server errstr error string pointer Returns: TRUE if OK (nothing to set up, or setup worked) */ static BOOL init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr) { #ifdef OPENSSL_NO_ECDH return TRUE; #else EC_KEY * ecdh; uschar * exp_curve; int nid; BOOL rv; if (host) /* No ECDH setup for clients, only for servers */ return TRUE; # ifndef EXIM_HAVE_ECDH DEBUG(D_tls) debug_printf("No OpenSSL API to define ECDH parameters, skipping\n"); return TRUE; # else if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr)) return FALSE; if (!exp_curve || !*exp_curve) return TRUE; /* "auto" needs to be handled carefully. * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO) * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b */ if (Ustrcmp(exp_curve, "auto") == 0) { #if OPENSSL_VERSION_NUMBER < 0x10002000L DEBUG(D_tls) debug_printf( "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n"); exp_curve = US"prime256v1"; #else # if defined SSL_CTRL_SET_ECDH_AUTO DEBUG(D_tls) debug_printf( "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n"); SSL_CTX_set_ecdh_auto(sctx, 1); return TRUE; # else DEBUG(D_tls) debug_printf( "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n"); return TRUE; # endif #endif } DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve); if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef # endif ) { tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve), host, NULL, errstr); return FALSE; } if (!(ecdh = EC_KEY_new_by_curve_name(nid))) { tls_error(US"Unable to create ec curve", host, NULL, errstr); return FALSE; } /* The "tmp" in the name here refers to setting a temporary key not to the stability of the interface. */ if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0)) tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr); else DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve); EC_KEY_free(ecdh); return !rv; # endif /*EXIM_HAVE_ECDH*/ #endif /*OPENSSL_NO_ECDH*/ } #ifndef DISABLE_OCSP /************************************************* * Load OCSP information into state * *************************************************/ /* Called to load the server OCSP response from the given file into memory, once caller has determined this is needed. Checks validity. Debugs a message if invalid. ASSUMES: single response, for single cert. Arguments: sctx the SSL_CTX* to update cbinfo various parts of session state filename the filename putatively holding an OCSP response is_pem file is PEM format; otherwise is DER */ static void ocsp_load_response(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, const uschar * filename, BOOL is_pem) { BIO * bio; OCSP_RESPONSE * resp; OCSP_BASICRESP * basic_response; OCSP_SINGLERESP * single_response; ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd; STACK_OF(X509) * sk; unsigned long verify_flags; int status, reason, i; DEBUG(D_tls) debug_printf("tls_ocsp_file (%s) '%s'\n", is_pem ? "PEM" : "DER", filename); if (!(bio = BIO_new_file(CS filename, "rb"))) { DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n", filename); return; } if (is_pem) { uschar * data, * freep; char * dummy; long len; if (!PEM_read_bio(bio, &dummy, &dummy, &data, &len)) { DEBUG(D_tls) debug_printf("Failed to read PEM file \"%s\"\n", filename); return; } debug_printf("read pem file\n"); freep = data; resp = d2i_OCSP_RESPONSE(NULL, CUSS &data, len); OPENSSL_free(freep); } else resp = d2i_OCSP_RESPONSE_bio(bio, NULL); BIO_free(bio); if (!resp) { DEBUG(D_tls) debug_printf("Error reading OCSP response.\n"); return; } if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL) { DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n", OCSP_response_status_str(status), status); goto bad; } #ifdef notdef { BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE); OCSP_RESPONSE_print(bp, resp, 0); /* extreme debug: stapling content */ BIO_free(bp); } #endif if (!(basic_response = OCSP_response_get1_basic(resp))) { DEBUG(D_tls) debug_printf("OCSP response parse error: unable to extract basic response.\n"); goto bad; } sk = cbinfo->verify_stack; verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */ /* May need to expose ability to adjust those flags? OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT OCSP_TRUSTOTHER OCSP_NOINTERN */ /* This does a full verify on the OCSP proof before we load it for serving up; possibly overkill - just date-checks might be nice enough. OCSP_basic_verify takes a "store" arg, but does not use it for the chain verification, which is all we do when OCSP_NOVERIFY is set. The content from the wire "basic_response" and a cert-stack "sk" are all that is used. We have a stack, loaded in setup_certs() if tls_verify_certificates was a file (not a directory, or "system"). It is unfortunate we cannot used the connection context store, as that would neatly handle the "system" case too, but there seems to be no library function for getting a stack from a store. [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ] We do not free the stack since it could be needed a second time for SNI handling. Separately we might try to replace using OCSP_basic_verify() - which seems to not be a public interface into the OpenSSL library (there's no manual entry) - But what with? We also use OCSP_basic_verify in the client stapling callback. And there we NEED it; we must verify that status... unless the library does it for us anyway? */ if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0) { DEBUG(D_tls) { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); debug_printf("OCSP response verify failure: %s\n", US ssl_errstring); } goto bad; } /* Here's the simplifying assumption: there's only one response, for the one certificate we use, and nothing for anything else in a chain. If this proves false, we need to extract a cert id from our issued cert (tls_certificate) and use that for OCSP_resp_find_status() (which finds the right cert in the stack and then calls OCSP_single_get0_status()). I'm hoping to avoid reworking a bunch more of how we handle state here. XXX that will change when we add support for (TLS1.3) whole-chain stapling */ if (!(single_response = OCSP_resp_get0(basic_response, 0))) { DEBUG(D_tls) debug_printf("Unable to get first response from OCSP basic response.\n"); goto bad; } status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd); if (status != V_OCSP_CERTSTATUS_GOOD) { DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n", OCSP_cert_status_str(status), status, OCSP_crl_reason_str(reason), reason); goto bad; } if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE)) { DEBUG(D_tls) debug_printf("OCSP status invalid times.\n"); goto bad; } supply_response: /* Add the resp to the list used by tls_server_stapling_cb() */ { ocsp_resplist ** op = &cbinfo->u_ocsp.server.olist, * oentry; while (oentry = *op) op = &oentry->next; *op = oentry = store_get(sizeof(ocsp_resplist), FALSE); oentry->next = NULL; oentry->resp = resp; } return; bad: if (f.running_in_test_harness) { extern char ** environ; if (environ) for (uschar ** p = USS environ; *p; p++) if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0) { DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n"); goto supply_response; } } return; } static void ocsp_free_response_list(tls_ext_ctx_cb * cbinfo) { for (ocsp_resplist * olist = cbinfo->u_ocsp.server.olist; olist; olist = olist->next) OCSP_RESPONSE_free(olist->resp); cbinfo->u_ocsp.server.olist = NULL; } #endif /*!DISABLE_OCSP*/ /* Create and install a selfsigned certificate, for use in server mode */ static int tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr) { X509 * x509 = NULL; EVP_PKEY * pkey; RSA * rsa; X509_NAME * name; uschar * where; where = US"allocating pkey"; if (!(pkey = EVP_PKEY_new())) goto err; where = US"allocating cert"; if (!(x509 = X509_new())) goto err; where = US"generating pkey"; if (!(rsa = rsa_callback(NULL, 0, 2048))) goto err; where = US"assigning pkey"; if (!EVP_PKEY_assign_RSA(pkey, rsa)) goto err; X509_set_version(x509, 2); /* N+1 - version 3 */ ASN1_INTEGER_set(X509_get_serialNumber(x509), 1); X509_gmtime_adj(X509_get_notBefore(x509), 0); X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */ X509_set_pubkey(x509, pkey); name = X509_get_subject_name(x509); X509_NAME_add_entry_by_txt(name, "C", MBSTRING_ASC, CUS "UK", -1, -1, 0); X509_NAME_add_entry_by_txt(name, "O", MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0); X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0); X509_set_issuer_name(x509, name); where = US"signing cert"; if (!X509_sign(x509, pkey, EVP_md5())) goto err; where = US"installing selfsign cert"; if (!SSL_CTX_use_certificate(sctx, x509)) goto err; where = US"installing selfsign key"; if (!SSL_CTX_use_PrivateKey(sctx, pkey)) goto err; return OK; err: (void) tls_error(where, NULL, NULL, errstr); if (x509) X509_free(x509); if (pkey) EVP_PKEY_free(pkey); return DEFER; } static int tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file, uschar ** errstr) { DEBUG(D_tls) debug_printf("tls_certificate file '%s'\n", file); if (!SSL_CTX_use_certificate_chain_file(sctx, CS file)) return tls_error(string_sprintf( "SSL_CTX_use_certificate_chain_file file=%s", file), cbinfo->host, NULL, errstr); return 0; } static int tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file, uschar ** errstr) { DEBUG(D_tls) debug_printf("tls_privatekey file '%s'\n", file); if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM)) return tls_error(string_sprintf( "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr); return 0; } /************************************************* * Expand key and cert file specs * *************************************************/ /* Called once during tls_init and possibly again during TLS setup, for a new context, if Server Name Indication was used and tls_sni was seen in the certificate string. Arguments: sctx the SSL_CTX* to update cbinfo various parts of session state errstr error string pointer Returns: OK/DEFER/FAIL */ static int tls_expand_session_files(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar ** errstr) { uschar * expanded; if (!cbinfo->certificate) { if (!cbinfo->is_server) /* client */ return OK; /* server */ if (tls_install_selfsign(sctx, errstr) != OK) return DEFER; } else { int err; if ( !reexpand_tls_files_for_sni && ( Ustrstr(cbinfo->certificate, US"tls_sni") || Ustrstr(cbinfo->certificate, US"tls_in_sni") || Ustrstr(cbinfo->certificate, US"tls_out_sni") ) ) reexpand_tls_files_for_sni = TRUE; if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr)) return DEFER; if (expanded) if (cbinfo->is_server) { const uschar * file_list = expanded; int sep = 0; uschar * file; #ifndef DISABLE_OCSP const uschar * olist = cbinfo->u_ocsp.server.file; int osep = 0; uschar * ofile; BOOL fmt_pem = FALSE; if (olist) if (!expand_check(olist, US"tls_ocsp_file", USS &olist, errstr)) return DEFER; if (olist && !*olist) olist = NULL; if ( cbinfo->u_ocsp.server.file_expanded && olist && (Ustrcmp(olist, cbinfo->u_ocsp.server.file_expanded) == 0)) { DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n"); olist = NULL; } else { ocsp_free_response_list(cbinfo); cbinfo->u_ocsp.server.file_expanded = olist; } #endif while (file = string_nextinlist(&file_list, &sep, NULL, 0)) { if ((err = tls_add_certfile(sctx, cbinfo, file, errstr))) return err; #ifndef DISABLE_OCSP if (olist) if ((ofile = string_nextinlist(&olist, &osep, NULL, 0))) { if (Ustrncmp(ofile, US"PEM ", 4) == 0) { fmt_pem = TRUE; ofile += 4; } else if (Ustrncmp(ofile, US"DER ", 4) == 0) { fmt_pem = FALSE; ofile += 4; } ocsp_load_response(sctx, cbinfo, ofile, fmt_pem); } else DEBUG(D_tls) debug_printf("ran out of ocsp file list\n"); #endif } } else /* would there ever be a need for multiple client certs? */ if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr))) return err; if ( cbinfo->privatekey && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr)) return DEFER; /* If expansion was forced to fail, key_expanded will be NULL. If the result of the expansion is an empty string, ignore it also, and assume the private key is in the same file as the certificate. */ if (expanded && *expanded) if (cbinfo->is_server) { const uschar * file_list = expanded; int sep = 0; uschar * file; while (file = string_nextinlist(&file_list, &sep, NULL, 0)) if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr))) return err; } else /* would there ever be a need for multiple client certs? */ if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr))) return err; } return OK; } /************************************************* * Callback to handle SNI * *************************************************/ /* Called when acting as server during the TLS session setup if a Server Name Indication extension was sent by the client. API documentation is OpenSSL s_server.c implementation. Arguments: s SSL* of the current session ad unknown (part of OpenSSL API) (unused) arg Callback of "our" registered data Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK} XXX might need to change to using ClientHello callback, per https://www.openssl.org/docs/manmaster/man3/SSL_client_hello_cb_fn.html */ #ifdef EXIM_HAVE_OPENSSL_TLSEXT static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg) { const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name); tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg; int rc; int old_pool = store_pool; uschar * dummy_errstr; if (!servername) return SSL_TLSEXT_ERR_OK; DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername, reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)"); /* Make the extension value available for expansion */ store_pool = POOL_PERM; tls_in.sni = string_copy_taint(US servername, TRUE); store_pool = old_pool; if (!reexpand_tls_files_for_sni) return SSL_TLSEXT_ERR_OK; /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually; not confident that memcpy wouldn't break some internal reference counting. Especially since there's a references struct member, which would be off. */ #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD if (!(server_sni = SSL_CTX_new(TLS_server_method()))) #else if (!(server_sni = SSL_CTX_new(SSLv23_server_method()))) #endif { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring); goto bad; } /* Not sure how many of these are actually needed, since SSL object already exists. Might even need this selfsame callback, for reneg? */ SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx)); SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx)); SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx)); SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx)); SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb); SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo); if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr) || !init_ecdh(server_sni, NULL, &dummy_errstr) ) goto bad; if ( cbinfo->server_cipher_list && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list)) goto bad; #ifndef DISABLE_OCSP if (cbinfo->u_ocsp.server.file) { SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb); SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo); } #endif if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server, &dummy_errstr)) != OK) goto bad; /* do this after setup_certs, because this can require the certs for verifying OCSP information. */ if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK) goto bad; DEBUG(D_tls) debug_printf("Switching SSL context.\n"); SSL_set_SSL_CTX(s, server_sni); return SSL_TLSEXT_ERR_OK; bad: return SSL_TLSEXT_ERR_ALERT_FATAL; } #endif /* EXIM_HAVE_OPENSSL_TLSEXT */ #ifndef DISABLE_OCSP /************************************************* * Callback to handle OCSP Stapling * *************************************************/ /* Called when acting as server during the TLS session setup if the client requests OCSP information with a Certificate Status Request. Documentation via openssl s_server.c and the Apache patch from the OpenSSL project. */ static int tls_server_stapling_cb(SSL *s, void *arg) { const tls_ext_ctx_cb * cbinfo = (tls_ext_ctx_cb *) arg; ocsp_resplist * olist = cbinfo->u_ocsp.server.olist; uschar * response_der; /*XXX blob */ int response_der_len; DEBUG(D_tls) debug_printf("Received TLS status request (OCSP stapling); %s response list\n", olist ? "have" : "lack"); tls_in.ocsp = OCSP_NOT_RESP; if (!olist) return SSL_TLSEXT_ERR_NOACK; #ifdef EXIM_HAVE_OPESSL_GET0_SERIAL { const X509 * cert_sent = SSL_get_certificate(s); const ASN1_INTEGER * cert_serial = X509_get0_serialNumber(cert_sent); const BIGNUM * cert_bn = ASN1_INTEGER_to_BN(cert_serial, NULL); const X509_NAME * cert_issuer = X509_get_issuer_name(cert_sent); uschar * chash; uint chash_len; for (; olist; olist = olist->next) { OCSP_BASICRESP * bs = OCSP_response_get1_basic(olist->resp); const OCSP_SINGLERESP * single = OCSP_resp_get0(bs, 0); const OCSP_CERTID * cid = OCSP_SINGLERESP_get0_id(single); ASN1_INTEGER * res_cert_serial; const BIGNUM * resp_bn; ASN1_OCTET_STRING * res_cert_iNameHash; (void) OCSP_id_get0_info(&res_cert_iNameHash, NULL, NULL, &res_cert_serial, (OCSP_CERTID *) cid); resp_bn = ASN1_INTEGER_to_BN(res_cert_serial, NULL); DEBUG(D_tls) { debug_printf("cert serial: %s\n", BN_bn2hex(cert_bn)); debug_printf("resp serial: %s\n", BN_bn2hex(resp_bn)); } if (BN_cmp(cert_bn, resp_bn) == 0) { DEBUG(D_tls) debug_printf("matched serial for ocsp\n"); /*XXX TODO: check the rest of the list for duplicate matches. If any, need to also check the Issuer Name hash. Without this, we will provide the wrong status in the case of duplicate id. */ break; } DEBUG(D_tls) debug_printf("not match serial for ocsp\n"); } if (!olist) { DEBUG(D_tls) debug_printf("failed to find match for ocsp\n"); return SSL_TLSEXT_ERR_NOACK; } } #else if (olist->next) { DEBUG(D_tls) debug_printf("OpenSSL version too early to support multi-leaf OCSP\n"); return SSL_TLSEXT_ERR_NOACK; } #endif /*XXX could we do the i2d earlier, rather than during the callback? */ response_der = NULL; response_der_len = i2d_OCSP_RESPONSE(olist->resp, &response_der); if (response_der_len <= 0) return SSL_TLSEXT_ERR_NOACK; SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len); tls_in.ocsp = OCSP_VFIED; return SSL_TLSEXT_ERR_OK; } static void time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time) { BIO_printf(bp, "\t%s: ", str); ASN1_GENERALIZEDTIME_print(bp, time); BIO_puts(bp, "\n"); } static int tls_client_stapling_cb(SSL *s, void *arg) { tls_ext_ctx_cb * cbinfo = arg; const unsigned char * p; int len; OCSP_RESPONSE * rsp; OCSP_BASICRESP * bs; int i; DEBUG(D_tls) debug_printf("Received TLS status callback (OCSP stapling):\n"); len = SSL_get_tlsext_status_ocsp_resp(s, &p); if(!p) { /* Expect this when we requested ocsp but got none */ if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher)) log_write(0, LOG_MAIN, "Required TLS certificate status not received"); else DEBUG(D_tls) debug_printf(" null\n"); return cbinfo->u_ocsp.client.verify_required ? 0 : 1; } if (!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len))) { tls_out.ocsp = OCSP_FAILED; /*XXX should use tlsp-> to permit concurrent outbound */ if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN, "Received TLS cert status response, parse error"); else DEBUG(D_tls) debug_printf(" parse error\n"); return 0; } if (!(bs = OCSP_response_get1_basic(rsp))) { tls_out.ocsp = OCSP_FAILED; if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response"); else DEBUG(D_tls) debug_printf(" error parsing response\n"); OCSP_RESPONSE_free(rsp); return 0; } /* We'd check the nonce here if we'd put one in the request. */ /* However that would defeat cacheability on the server so we don't. */ /* This section of code reworked from OpenSSL apps source; The OpenSSL Project retains copyright: Copyright (c) 1999 The OpenSSL Project. All rights reserved. */ { BIO * bp = NULL; #ifndef EXIM_HAVE_OCSP_RESP_COUNT STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses; #endif DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE); /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */ /* Use the chain that verified the server cert to verify the stapled info */ /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */ if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack, cbinfo->u_ocsp.client.verify_store, OCSP_NOEXPLICIT)) <= 0) if (ERR_peek_error()) { tls_out.ocsp = OCSP_FAILED; if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable: %s", ERR_reason_error_string(ERR_peek_error())); BIO_printf(bp, "OCSP response verify failure\n"); ERR_print_errors(bp); OCSP_RESPONSE_print(bp, rsp, 0); goto failed; } else DEBUG(D_tls) debug_printf("no explicit trust for OCSP signing" " in the root CA certificate; ignoring\n"); DEBUG(D_tls) debug_printf("OCSP response well-formed and signed OK\n"); /*XXX So we have a good stapled OCSP status. How do we know it is for the cert of interest? OpenSSL 1.1.0 has a routine OCSP_resp_find_status() which matches on a cert id, which presumably we should use. Making an id needs OCSP_cert_id_new(), which takes issuerName, issuerKey, serialNumber. Are they all in the cert? For now, carry on blindly accepting the resp. */ for (int idx = #ifdef EXIM_HAVE_OCSP_RESP_COUNT OCSP_resp_count(bs) - 1; #else sk_OCSP_SINGLERESP_num(sresp) - 1; #endif idx >= 0; idx--) { OCSP_SINGLERESP * single = OCSP_resp_get0(bs, idx); int status, reason; ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd; /*XXX so I can see putting a loop in here to handle a rsp with >1 singleresp - but what happens with a GnuTLS-style input? we could do with a debug label for each singleresp - it has a certID with a serialNumber, but I see no API to get that */ status = OCSP_single_get0_status(single, &reason, &rev, &thisupd, &nextupd); DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd); DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd); if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE)) { tls_out.ocsp = OCSP_FAILED; DEBUG(D_tls) ERR_print_errors(bp); log_write(0, LOG_MAIN, "Server OSCP dates invalid"); goto failed; } DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n", OCSP_cert_status_str(status)); switch(status) { case V_OCSP_CERTSTATUS_GOOD: continue; /* the idx loop */ case V_OCSP_CERTSTATUS_REVOKED: log_write(0, LOG_MAIN, "Server certificate revoked%s%s", reason != -1 ? "; reason: " : "", reason != -1 ? OCSP_crl_reason_str(reason) : ""); DEBUG(D_tls) time_print(bp, "Revocation Time", rev); break; default: log_write(0, LOG_MAIN, "Server certificate status unknown, in OCSP stapling"); break; } goto failed; } i = 1; tls_out.ocsp = OCSP_VFIED; goto good; failed: tls_out.ocsp = OCSP_FAILED; i = cbinfo->u_ocsp.client.verify_required ? 0 : 1; good: BIO_free(bp); } OCSP_RESPONSE_free(rsp); return i; } #endif /*!DISABLE_OCSP*/ /************************************************* * Initialize for TLS * *************************************************/ static void tls_openssl_init(void) { #ifdef EXIM_NEED_OPENSSL_INIT SSL_load_error_strings(); /* basic set up */ OpenSSL_add_ssl_algorithms(); #endif #if defined(EXIM_HAVE_SHA256) && !defined(OPENSSL_AUTO_SHA256) /* SHA256 is becoming ever more popular. This makes sure it gets added to the list of available digests. */ EVP_add_digest(EVP_sha256()); #endif } /* Called from both server and client code, to do preliminary initialization of the library. We allocate and return a context structure. Arguments: ctxp returned SSL context host connected host, if client; NULL if server dhparam DH parameter file certificate certificate file privatekey private key ocsp_file file of stapling info (server); flag for require ocsp (client) addr address if client; NULL if server (for some randomness) cbp place to put allocated callback context errstr error string pointer Returns: OK/DEFER/FAIL */ static int tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate, uschar *privatekey, #ifndef DISABLE_OCSP uschar *ocsp_file, #endif address_item *addr, tls_ext_ctx_cb ** cbp, tls_support * tlsp, uschar ** errstr) { SSL_CTX * ctx; long init_options; int rc; tls_ext_ctx_cb * cbinfo; cbinfo = store_malloc(sizeof(tls_ext_ctx_cb)); cbinfo->tlsp = tlsp; cbinfo->certificate = certificate; cbinfo->privatekey = privatekey; cbinfo->is_server = host==NULL; #ifndef DISABLE_OCSP cbinfo->verify_stack = NULL; if (!host) { cbinfo->u_ocsp.server.file = ocsp_file; cbinfo->u_ocsp.server.file_expanded = NULL; cbinfo->u_ocsp.server.olist = NULL; } else cbinfo->u_ocsp.client.verify_store = NULL; #endif cbinfo->dhparam = dhparam; cbinfo->server_cipher_list = NULL; cbinfo->host = host; #ifndef DISABLE_EVENT cbinfo->event_action = NULL; #endif tls_openssl_init(); /* Create a context. The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant negotiation in the different methods; as far as I can tell, the only *_{server,client}_method which allows negotiation is SSLv23, which exists even when OpenSSL is built without SSLv2 support. By disabling with openssl_options, we can let admins re-enable with the existing knob. */ #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method()))) #else if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method()))) #endif return tls_error(US"SSL_CTX_new", host, NULL, errstr); /* It turns out that we need to seed the random number generator this early in order to get the full complement of ciphers to work. It took me roughly a day of work to discover this by experiment. On systems that have /dev/urandom, SSL may automatically seed itself from there. Otherwise, we have to make something up as best we can. Double check afterwards. */ if (!RAND_status()) { randstuff r; gettimeofday(&r.tv, NULL); r.p = getpid(); RAND_seed(US (&r), sizeof(r)); RAND_seed(US big_buffer, big_buffer_size); if (addr != NULL) RAND_seed(US addr, sizeof(addr)); if (!RAND_status()) return tls_error(US"RAND_status", host, US"unable to seed random number generator", errstr); } /* Set up the information callback, which outputs if debugging is at a suitable level. */ DEBUG(D_tls) { SSL_CTX_set_info_callback(ctx, (void (*)())info_callback); #if defined(EXIM_HAVE_OPESSL_TRACE) && !defined(OPENSSL_NO_SSL_TRACE) /* this needs a debug build of OpenSSL */ SSL_CTX_set_msg_callback(ctx, (void (*)())SSL_trace); #endif #ifdef OPENSSL_HAVE_KEYLOG_CB SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback); #endif } /* Automatically re-try reads/writes after renegotiation. */ (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY); /* Apply administrator-supplied work-arounds. Historically we applied just one requested option, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we moved to an administrator-controlled list of options to specify and grandfathered in the first one as the default value for "openssl_options". No OpenSSL version number checks: the options we accept depend upon the availability of the option value macros from OpenSSL. */ if (!tls_openssl_options_parse(openssl_options, &init_options)) return tls_error(US"openssl_options parsing failed", host, NULL, errstr); #ifdef EXPERIMENTAL_TLS_RESUME tlsp->resumption = RESUME_SUPPORTED; #endif if (init_options) { #ifdef EXPERIMENTAL_TLS_RESUME /* Should the server offer session resumption? */ if (!host && verify_check_host(&tls_resumption_hosts) == OK) { DEBUG(D_tls) debug_printf("tls_resumption_hosts overrides openssl_options\n"); init_options &= ~SSL_OP_NO_TICKET; tlsp->resumption |= RESUME_SERVER_TICKET; /* server will give ticket on request */ tlsp->host_resumable = TRUE; } #endif DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options); if (!(SSL_CTX_set_options(ctx, init_options))) return tls_error(string_sprintf( "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr); } else DEBUG(D_tls) debug_printf("no SSL CTX options to set\n"); /* We'd like to disable session cache unconditionally, but foolish Outlook Express clients then give up the first TLS connection and make a second one (which works). Only when there is an IMAP service on the same machine. Presumably OE is trying to use the cache for A on B. Leave it enabled for now, until we work out a decent way of presenting control to the config. It will never be used because we use a new context every time. */ #ifdef notdef (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF); #endif /* Initialize with DH parameters if supplied */ /* Initialize ECDH temp key parameter selection */ if ( !init_dh(ctx, dhparam, host, errstr) || !init_ecdh(ctx, host, errstr) ) return DEFER; /* Set up certificate and key (and perhaps OCSP info) */ if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK) return rc; /* If we need to handle SNI or OCSP, do so */ #ifdef EXIM_HAVE_OPENSSL_TLSEXT # ifndef DISABLE_OCSP if (!(cbinfo->verify_stack = sk_X509_new_null())) { DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n"); return FAIL; } # endif if (!host) /* server */ { # ifndef DISABLE_OCSP /* We check u_ocsp.server.file, not server.olist, because we care about if the option exists, not what the current expansion might be, as SNI might change the certificate and OCSP file in use between now and the time the callback is invoked. */ if (cbinfo->u_ocsp.server.file) { SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb); SSL_CTX_set_tlsext_status_arg(ctx, cbinfo); } # endif /* We always do this, so that $tls_sni is available even if not used in tls_certificate */ SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb); SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo); } # ifndef DISABLE_OCSP else /* client */ if(ocsp_file) /* wanting stapling */ { if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new())) { DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n"); return FAIL; } SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb); SSL_CTX_set_tlsext_status_arg(ctx, cbinfo); } # endif #endif cbinfo->verify_cert_hostnames = NULL; #ifdef EXIM_HAVE_EPHEM_RSA_KEX /* Set up the RSA callback */ SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); #endif /* Finally, set the session cache timeout, and we are done. The period appears to be also used for (server-generated) session tickets */ SSL_CTX_set_timeout(ctx, ssl_session_timeout); DEBUG(D_tls) debug_printf("Initialized TLS\n"); *cbp = cbinfo; *ctxp = ctx; return OK; } /************************************************* * Get name of cipher in use * *************************************************/ /* Argument: pointer to an SSL structure for the connection pointer to number of bits for cipher Returns: pointer to allocated string in perm-pool */ static uschar * construct_cipher_name(SSL * ssl, const uschar * ver, int * bits) { int pool = store_pool; /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't yet reflect that. It should be a safe change anyway, even 0.9.8 versions have the accessor functions use const in the prototype. */ const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl); uschar * s; SSL_CIPHER_get_bits(c, bits); store_pool = POOL_PERM; s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits); store_pool = pool; DEBUG(D_tls) debug_printf("Cipher: %s\n", s); return s; } /* Get IETF-standard name for ciphersuite. Argument: pointer to an SSL structure for the connection Returns: pointer to string */ static const uschar * cipher_stdname_ssl(SSL * ssl) { #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl)); #else ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl)); return cipher_stdname(id >> 8, id & 0xff); #endif } static const uschar * tlsver_name(SSL * ssl) { uschar * s, * p; int pool = store_pool; store_pool = POOL_PERM; s = string_copy(US SSL_get_version(ssl)); store_pool = pool; if ((p = Ustrchr(s, 'v'))) /* TLSv1.2 -> TLS1.2 */ for (;; p++) if (!(*p = p[1])) break; return CUS s; } static void peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz) { /*XXX we might consider a list-of-certs variable for the cert chain. SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support in list-handling functions, also consider the difference between the entire chain and the elements sent by the peer. */ tlsp->peerdn = NULL; /* Will have already noted peercert on a verify fail; possibly not the leaf */ if (!tlsp->peercert) tlsp->peercert = SSL_get_peer_certificate(ssl); /* Beware anonymous ciphers which lead to server_cert being NULL */ if (tlsp->peercert) if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz)) { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); } else { int oldpool = store_pool; peerdn[siz-1] = '\0'; /* paranoia */ store_pool = POOL_PERM; tlsp->peerdn = string_copy(peerdn); store_pool = oldpool; /* We used to set CV in the cert-verify callbacks (either plain or dane) but they don't get called on session-resumption. So use the official interface, which uses the resumed value. Unfortunately this claims verified when it actually failed but we're in try-verify mode, due to us wanting the knowlege that it failed so needing to have the callback and forcing a permissive return. If we don't force it, the TLS startup is failed. The extra bit of information is set in verify_override in the cb, stashed for resumption next to the TLS session, and used here. */ if (!tlsp->verify_override) tlsp->certificate_verified = #ifdef SUPPORT_DANE tlsp->dane_verified || #endif SSL_get_verify_result(ssl) == X509_V_OK; } } /************************************************* * Set up for verifying certificates * *************************************************/ #ifndef DISABLE_OCSP /* Load certs from file, return TRUE on success */ static BOOL chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack) { BIO * bp; X509 * x; while (sk_X509_num(verify_stack) > 0) X509_free(sk_X509_pop(verify_stack)); if (!(bp = BIO_new_file(CS file, "r"))) return FALSE; while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL))) sk_X509_push(verify_stack, x); BIO_free(bp); return TRUE; } #endif /* Called by both client and server startup; on the server possibly repeated after a Server Name Indication. Arguments: sctx SSL_CTX* to initialise certs certs file or NULL crl CRL file or NULL host NULL in a server; the remote host in a client optional TRUE if called from a server for a host in tls_try_verify_hosts; otherwise passed as FALSE cert_vfy_cb Callback function for certificate verification errstr error string pointer Returns: OK/DEFER/FAIL */ static int setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr) { uschar *expcerts, *expcrl; if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr)) return DEFER; DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts); if (expcerts && *expcerts) { /* Tell the library to use its compiled-in location for the system default CA bundle. Then add the ones specified in the config, if any. */ if (!SSL_CTX_set_default_verify_paths(sctx)) return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr); if (Ustrcmp(expcerts, "system") != 0) { struct stat statbuf; if (Ustat(expcerts, &statbuf) < 0) { log_write(0, LOG_MAIN|LOG_PANIC, "failed to stat %s for certificates", expcerts); return DEFER; } else { uschar *file, *dir; if ((statbuf.st_mode & S_IFMT) == S_IFDIR) { file = NULL; dir = expcerts; } else { file = expcerts; dir = NULL; #ifndef DISABLE_OCSP /* In the server if we will be offering an OCSP proof, load chain from file for verifying the OCSP proof at load time. */ /*XXX Glitch! The file here is tls_verify_certs: the chain for verifying the client cert. This is inconsistent with the need to verify the OCSP proof of the server cert. */ if ( !host && statbuf.st_size > 0 && server_static_cbinfo->u_ocsp.server.file && !chain_from_pem_file(file, server_static_cbinfo->verify_stack) ) { log_write(0, LOG_MAIN|LOG_PANIC, "failed to load cert chain from %s", file); return DEFER; } #endif } /* If a certificate file is empty, the next function fails with an unhelpful error message. If we skip it, we get the correct behaviour (no certificates are recognized, but the error message is still misleading (it says no certificate was supplied). But this is better. */ if ( (!file || statbuf.st_size > 0) && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir)) return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr); /* Load the list of CAs for which we will accept certs, for sending to the client. This is only for the one-file tls_verify_certificates variant. If a list isn't loaded into the server, but some verify locations are set, the server end appears to make a wildcard request for client certs. Meanwhile, the client library as default behaviour *ignores* the list we send over the wire - see man SSL_CTX_set_client_cert_cb. Because of this, and that the dir variant is likely only used for the public-CA bundle (not for a private CA), not worth fixing. */ if (file) { STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file); SSL_CTX_set_client_CA_list(sctx, names); DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", sk_X509_NAME_num(names)); } } } /* Handle a certificate revocation list. */ #if OPENSSL_VERSION_NUMBER > 0x00907000L /* This bit of code is now the version supplied by Lars Mainka. (I have merely reformatted it into the Exim code style.) "From here I changed the code to add support for multiple crl's in pem format in one file or to support hashed directory entries in pem format instead of a file. This method now uses the library function X509_STORE_load_locations to add the CRL location to the SSL context. OpenSSL will then handle the verify against CA certs and CRLs by itself in the verify callback." */ if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER; if (expcrl && *expcrl) { struct stat statbufcrl; if (Ustat(expcrl, &statbufcrl) < 0) { log_write(0, LOG_MAIN|LOG_PANIC, "failed to stat %s for certificates revocation lists", expcrl); return DEFER; } else { /* is it a file or directory? */ uschar *file, *dir; X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx); if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) { file = NULL; dir = expcrl; DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); } else { file = expcrl; dir = NULL; DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); } if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) return tls_error(US"X509_STORE_load_locations", host, NULL, errstr); /* setting the flags to check against the complete crl chain */ X509_STORE_set_flags(cvstore, X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); } } #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ /* If verification is optional, don't fail if no certificate */ SSL_CTX_set_verify(sctx, SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), cert_vfy_cb); } return OK; } /************************************************* * Start a TLS session in a server * *************************************************/ /* This is called when Exim is running as a server, after having received the STARTTLS command. It must respond to that command, and then negotiate a TLS session. Arguments: require_ciphers allowed ciphers errstr pointer to error message Returns: OK on success DEFER for errors before the start of the negotiation FAIL for errors during the negotiation; the server can't continue running. */ int tls_server_start(const uschar * require_ciphers, uschar ** errstr) { int rc; uschar * expciphers; tls_ext_ctx_cb * cbinfo; static uschar peerdn[256]; /* Check for previous activation */ if (tls_in.active.sock >= 0) { tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr); smtp_printf("554 Already in TLS\r\n", FALSE); return FAIL; } /* Initialize the SSL library. If it fails, it will already have logged the error. */ rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey, #ifndef DISABLE_OCSP tls_ocsp_file, #endif NULL, &server_static_cbinfo, &tls_in, errstr); if (rc != OK) return rc; cbinfo = server_static_cbinfo; if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr)) return FAIL; /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they were historically separated by underscores. So that I can use either form in my tests, and also for general convenience, we turn underscores into hyphens here. XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites() for TLS 1.3 . Since we do not call it at present we get the default list: TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256 */ if (expciphers) { for (uschar * s = expciphers; *s; s++ ) if (*s == '_') *s = '-'; DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers)) return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr); cbinfo->server_cipher_list = expciphers; } /* If this is a host for which certificate verification is mandatory or optional, set up appropriately. */ tls_in.certificate_verified = FALSE; #ifdef SUPPORT_DANE tls_in.dane_verified = FALSE; #endif server_verify_callback_called = FALSE; if (verify_check_host(&tls_verify_hosts) == OK) { rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server, errstr); if (rc != OK) return rc; server_verify_optional = FALSE; } else if (verify_check_host(&tls_try_verify_hosts) == OK) { rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, TRUE, verify_callback_server, errstr); if (rc != OK) return rc; server_verify_optional = TRUE; } #ifdef EXPERIMENTAL_TLS_RESUME SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_key_callback); /* despite working, appears to always return failure, so ignoring */ #endif #ifdef OPENSSL_HAVE_NUM_TICKETS # ifdef EXPERIMENTAL_TLS_RESUME SSL_CTX_set_num_tickets(server_ctx, tls_in.host_resumable ? 1 : 0); # else SSL_CTX_set_num_tickets(server_ctx, 0); /* send no TLS1.3 stateful-tickets */ # endif #endif /* Prepare for new connection */ if (!(server_ssl = SSL_new(server_ctx))) return tls_error(US"SSL_new", NULL, NULL, errstr); /* Warning: we used to SSL_clear(ssl) here, it was removed. * * With the SSL_clear(), we get strange interoperability bugs with * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in * OpenSSL itself, as a clear should not lead to inability to follow protocols. * * The SSL_clear() call is to let an existing SSL* be reused, typically after * session shutdown. In this case, we have a brand new object and there's no * obvious reason to immediately clear it. I'm guessing that this was * originally added because of incomplete initialisation which the clear fixed, * in some historic release. */ /* Set context and tell client to go ahead, except in the case of TLS startup on connection, where outputting anything now upsets the clients and tends to make them disconnect. We need to have an explicit fflush() here, to force out the response. Other smtp_printf() calls do not need it, because in non-TLS mode, the fflush() happens when smtp_getc() is called. */ SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx)); if (!tls_in.on_connect) { smtp_printf("220 TLS go ahead\r\n", FALSE); fflush(smtp_out); } /* Now negotiate the TLS session. We put our own timer on it, since it seems that the OpenSSL library doesn't. */ SSL_set_wfd(server_ssl, fileno(smtp_out)); SSL_set_rfd(server_ssl, fileno(smtp_in)); SSL_set_accept_state(server_ssl); DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); sigalrm_seen = FALSE; if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout); rc = SSL_accept(server_ssl); ALARM_CLR(0); if (rc <= 0) { int error = SSL_get_error(server_ssl, rc); switch(error) { case SSL_ERROR_NONE: break; case SSL_ERROR_ZERO_RETURN: DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr); if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN) SSL_shutdown(server_ssl); tls_close(NULL, TLS_NO_SHUTDOWN); return FAIL; /* Handle genuine errors */ case SSL_ERROR_SSL: { uschar * s = US"SSL_accept"; unsigned long e = ERR_peek_error(); if (ERR_GET_REASON(e) == SSL_R_WRONG_VERSION_NUMBER) s = string_sprintf("%s (%s)", s, SSL_get_version(server_ssl)); (void) tls_error(s, NULL, sigalrm_seen ? US"timed out" : NULL, errstr); return FAIL; } default: DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); if (error == SSL_ERROR_SYSCALL) { if (!errno) { *errstr = US"SSL_accept: TCP connection closed by peer"; return FAIL; } DEBUG(D_tls) debug_printf(" - syscall %s\n", strerror(errno)); } (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr); return FAIL; } } DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); ERR_clear_error(); /* Even success can leave errors in the stack. Seen with anon-authentication ciphersuite negotiated. */ #ifdef EXPERIMENTAL_TLS_RESUME if (SSL_session_reused(server_ssl)) { tls_in.resumption |= RESUME_USED; DEBUG(D_tls) debug_printf("Session reused\n"); } #endif /* TLS has been set up. Record data for the connection, adjust the input functions to read via TLS, and initialize things. */ #ifdef SSL_get_extms_support tls_in.ext_master_secret = SSL_get_extms_support(server_ssl) == 1; #endif peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn)); tls_in.ver = tlsver_name(server_ssl); tls_in.cipher = construct_cipher_name(server_ssl, tls_in.ver, &tls_in.bits); tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl); DEBUG(D_tls) { uschar buf[2048]; if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf))) debug_printf("Shared ciphers: %s\n", buf); #ifdef EXIM_HAVE_OPENSSL_KEYLOG { BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE); SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl)); BIO_free(bp); } #endif #ifdef EXIM_HAVE_SESSION_TICKET { SSL_SESSION * ss = SSL_get_session(server_ssl); if (SSL_SESSION_has_ticket(ss)) /* 1.1.0 */ debug_printf("The session has a ticket, life %lu seconds\n", SSL_SESSION_get_ticket_lifetime_hint(ss)); } #endif } /* Record the certificate we presented */ { X509 * crt = SSL_get_certificate(server_ssl); tls_in.ourcert = crt ? X509_dup(crt) : NULL; } /* Channel-binding info for authenticators See description in https://paquier.xyz/postgresql-2/channel-binding-openssl/ */ { uschar c, * s; size_t len = SSL_get_peer_finished(server_ssl, &c, 0); int old_pool = store_pool; SSL_get_peer_finished(server_ssl, s = store_get((int)len, FALSE), len); store_pool = POOL_PERM; tls_in.channelbinding = b64encode_taint(CUS s, (int)len, FALSE); store_pool = old_pool; DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage %p\n", tls_in.channelbinding); } /* Only used by the server-side tls (tls_in), including tls_getc. Client-side (tls_out) reads (seem to?) go via smtp_read_response()/ip_recv(). Hence no need to duplicate for _in and _out. */ if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; ssl_xfer_eof = ssl_xfer_error = FALSE; receive_getc = tls_getc; receive_getbuf = tls_getbuf; receive_get_cache = tls_get_cache; receive_ungetc = tls_ungetc; receive_feof = tls_feof; receive_ferror = tls_ferror; receive_smtp_buffered = tls_smtp_buffered; tls_in.active.sock = fileno(smtp_out); tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */ return OK; } static int tls_client_basic_ctx_init(SSL_CTX * ctx, host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo, uschar ** errstr) { int rc; /* stick to the old behaviour for compatibility if tls_verify_certificates is set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only the specified host patterns if one of them is defined */ if ( ( !ob->tls_verify_hosts && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts) ) || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK ) client_verify_optional = FALSE; else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK) client_verify_optional = TRUE; else return OK; if ((rc = setup_certs(ctx, ob->tls_verify_certificates, ob->tls_crl, host, client_verify_optional, verify_callback_client, errstr)) != OK) return rc; if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK) { cbinfo->verify_cert_hostnames = #ifdef SUPPORT_I18N string_domain_utf8_to_alabel(host->name, NULL); #else host->name; #endif DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n", cbinfo->verify_cert_hostnames); } return OK; } #ifdef SUPPORT_DANE static int dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr) { dns_scan dnss; const char * hostnames[2] = { CS host->name, NULL }; int found = 0; if (DANESSL_init(ssl, NULL, hostnames) != 1) return tls_error(US"hostnames load", host, NULL, errstr); for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) ) if (rr->type == T_TLSA && rr->size > 3) { const uschar * p = rr->data; uint8_t usage, selector, mtype; const char * mdname; usage = *p++; /* Only DANE-TA(2) and DANE-EE(3) are supported */ if (usage != 2 && usage != 3) continue; selector = *p++; mtype = *p++; switch (mtype) { default: continue; /* Only match-types 0, 1, 2 are supported */ case 0: mdname = NULL; break; case 1: mdname = "sha256"; break; case 2: mdname = "sha512"; break; } found++; switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3)) { default: return tls_error(US"tlsa load", host, NULL, errstr); case 0: /* action not taken */ case 1: break; } tls_out.tlsa_usage |= 1<resumption |= RESUME_SUPPORTED; if (tlsp->host_resumable) { dbdata_tls_session * dt; int len; open_db dbblock, * dbm_file; tlsp->resumption |= RESUME_CLIENT_REQUESTED; DEBUG(D_tls) debug_printf("checking for resumable session for %s\n", key); if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE))) { /* key for the db is the IP */ if ((dt = dbfn_read_with_length(dbm_file, key, &len))) { SSL_SESSION * ss = NULL; const uschar * sess_asn1 = dt->session; len -= sizeof(dbdata_tls_session); if (!(d2i_SSL_SESSION(&ss, &sess_asn1, (long)len))) { DEBUG(D_tls) { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); debug_printf("decoding session: %s\n", ssl_errstring); } } #ifdef EXIM_HAVE_SESSION_TICKET else if ( SSL_SESSION_get_ticket_lifetime_hint(ss) + dt->time_stamp < time(NULL)) { DEBUG(D_tls) debug_printf("session expired\n"); dbfn_delete(dbm_file, key); } #endif else if (!SSL_set_session(ssl, ss)) { DEBUG(D_tls) { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); debug_printf("applying session to ssl: %s\n", ssl_errstring); } } else { DEBUG(D_tls) debug_printf("good session\n"); tlsp->resumption |= RESUME_CLIENT_SUGGESTED; tlsp->verify_override = dt->verify_override; tlsp->ocsp = dt->ocsp; } } else DEBUG(D_tls) debug_printf("no session record\n"); dbfn_close(dbm_file); } } } /* On the client, save the session for later resumption */ static int tls_save_session_cb(SSL * ssl, SSL_SESSION * ss) { tls_ext_ctx_cb * cbinfo = SSL_get_ex_data(ssl, tls_exdata_idx); tls_support * tlsp; DEBUG(D_tls) debug_printf("tls_save_session_cb\n"); if (!cbinfo || !(tlsp = cbinfo->tlsp)->host_resumable) return 0; # ifdef OPENSSL_HAVE_NUM_TICKETS if (SSL_SESSION_is_resumable(ss)) /* 1.1.1 */ # endif { int len = i2d_SSL_SESSION(ss, NULL); int dlen = sizeof(dbdata_tls_session) + len; dbdata_tls_session * dt = store_get(dlen, TRUE); uschar * s = dt->session; open_db dbblock, * dbm_file; DEBUG(D_tls) debug_printf("session is resumable\n"); tlsp->resumption |= RESUME_SERVER_TICKET; /* server gave us a ticket */ dt->verify_override = tlsp->verify_override; dt->ocsp = tlsp->ocsp; (void) i2d_SSL_SESSION(ss, &s); /* s gets bumped to end */ if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE))) { const uschar * key = cbinfo->host->address; dbfn_delete(dbm_file, key); dbfn_write(dbm_file, key, dt, dlen); dbfn_close(dbm_file); DEBUG(D_tls) debug_printf("wrote session (len %u) to db\n", (unsigned)dlen); } } return 1; } static void tls_client_ctx_resume_prehandshake( exim_openssl_client_tls_ctx * exim_client_ctx, tls_support * tlsp, smtp_transport_options_block * ob, host_item * host) { /* Should the client request a session resumption ticket? */ if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK) { tlsp->host_resumable = TRUE; SSL_CTX_set_session_cache_mode(exim_client_ctx->ctx, SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_NO_INTERNAL | SSL_SESS_CACHE_NO_AUTO_CLEAR); SSL_CTX_sess_set_new_cb(exim_client_ctx->ctx, tls_save_session_cb); } } static BOOL tls_client_ssl_resume_prehandshake(SSL * ssl, tls_support * tlsp, host_item * host, uschar ** errstr) { if (tlsp->host_resumable) { DEBUG(D_tls) debug_printf("tls_resumption_hosts overrides openssl_options, enabling tickets\n"); SSL_clear_options(ssl, SSL_OP_NO_TICKET); tls_exdata_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0); if (!SSL_set_ex_data(ssl, tls_exdata_idx, client_static_cbinfo)) { tls_error(US"set ex_data", host, NULL, errstr); return FALSE; } debug_printf("tls_exdata_idx %d cbinfo %p\n", tls_exdata_idx, client_static_cbinfo); } tlsp->resumption = RESUME_SUPPORTED; /* Pick up a previous session, saved on an old ticket */ tls_retrieve_session(tlsp, ssl, host->address); return TRUE; } static void tls_client_resume_posthandshake(exim_openssl_client_tls_ctx * exim_client_ctx, tls_support * tlsp) { if (SSL_session_reused(exim_client_ctx->ssl)) { DEBUG(D_tls) debug_printf("The session was reused\n"); tlsp->resumption |= RESUME_USED; } } #endif /* EXPERIMENTAL_TLS_RESUME */ /************************************************* * Start a TLS session in a client * *************************************************/ /* Called from the smtp transport after STARTTLS has been accepted. Arguments: cctx connection context conn_args connection details cookie datum for randomness; can be NULL tlsp record details of TLS channel configuration here; must be non-NULL errstr error string pointer Returns: TRUE for success with TLS session context set in connection context, FALSE on error */ BOOL tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args, void * cookie, tls_support * tlsp, uschar ** errstr) { host_item * host = conn_args->host; /* for msgs and option-tests */ transport_instance * tb = conn_args->tblock; /* always smtp or NULL */ smtp_transport_options_block * ob = tb ? (smtp_transport_options_block *)tb->options_block : &smtp_transport_option_defaults; exim_openssl_client_tls_ctx * exim_client_ctx; uschar * expciphers; int rc; static uschar peerdn[256]; #ifndef DISABLE_OCSP BOOL request_ocsp = FALSE; BOOL require_ocsp = FALSE; #endif rc = store_pool; store_pool = POOL_PERM; exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx), FALSE); exim_client_ctx->corked = NULL; store_pool = rc; #ifdef SUPPORT_DANE tlsp->tlsa_usage = 0; #endif #ifndef DISABLE_OCSP { # ifdef SUPPORT_DANE if ( conn_args->dane && ob->hosts_request_ocsp[0] == '*' && ob->hosts_request_ocsp[1] == '\0' ) { /* Unchanged from default. Use a safer one under DANE */ request_ocsp = TRUE; ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} " " {= {4}{$tls_out_tlsa_usage}} } " " {*}{}}"; } # endif if ((require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK)) request_ocsp = TRUE; else # ifdef SUPPORT_DANE if (!request_ocsp) # endif request_ocsp = verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK; } #endif rc = tls_init(&exim_client_ctx->ctx, host, NULL, ob->tls_certificate, ob->tls_privatekey, #ifndef DISABLE_OCSP (void *)(long)request_ocsp, #endif cookie, &client_static_cbinfo, tlsp, errstr); if (rc != OK) return FALSE; tlsp->certificate_verified = FALSE; client_verify_callback_called = FALSE; expciphers = NULL; #ifdef SUPPORT_DANE if (conn_args->dane) { /* We fall back to tls_require_ciphers if unset, empty or forced failure, but other failures should be treated as problems. */ if (ob->dane_require_tls_ciphers && !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers", &expciphers, errstr)) return FALSE; if (expciphers && *expciphers == '\0') expciphers = NULL; } #endif if (!expciphers && !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers", &expciphers, errstr)) return FALSE; /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they are separated by underscores. So that I can use either form in my tests, and also for general convenience, we turn underscores into hyphens here. */ if (expciphers) { uschar *s = expciphers; while (*s) { if (*s == '_') *s = '-'; s++; } DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers)) { tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr); return FALSE; } } #ifdef SUPPORT_DANE if (conn_args->dane) { SSL_CTX_set_verify(exim_client_ctx->ctx, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, verify_callback_client_dane); if (!DANESSL_library_init()) { tls_error(US"library init", host, NULL, errstr); return FALSE; } if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0) { tls_error(US"context init", host, NULL, errstr); return FALSE; } } else #endif if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob, client_static_cbinfo, errstr) != OK) return FALSE; #ifdef EXPERIMENTAL_TLS_RESUME tls_client_ctx_resume_prehandshake(exim_client_ctx, tlsp, ob, host); #endif if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx))) { tls_error(US"SSL_new", host, NULL, errstr); return FALSE; } SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx)); SSL_set_fd(exim_client_ctx->ssl, cctx->sock); SSL_set_connect_state(exim_client_ctx->ssl); if (ob->tls_sni) { if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr)) return FALSE; if (!tlsp->sni) { DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n"); } else if (!Ustrlen(tlsp->sni)) tlsp->sni = NULL; else { #ifdef EXIM_HAVE_OPENSSL_TLSEXT DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni); SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni); #else log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n", tlsp->sni); #endif } } #ifdef SUPPORT_DANE if (conn_args->dane) if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK) return FALSE; #endif #ifndef DISABLE_OCSP /* Request certificate status at connection-time. If the server does OCSP stapling we will get the callback (set in tls_init()) */ # ifdef SUPPORT_DANE if (request_ocsp) { const uschar * s; if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage")) || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage")) ) { /* Re-eval now $tls_out_tlsa_usage is populated. If this means we avoid the OCSP request, we wasted the setup cost in tls_init(). */ require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK; request_ocsp = require_ocsp || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK; } } # endif if (request_ocsp) { SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp); client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp; tlsp->ocsp = OCSP_NOT_RESP; } #endif #ifdef EXPERIMENTAL_TLS_RESUME if (!tls_client_ssl_resume_prehandshake(exim_client_ctx->ssl, tlsp, host, errstr)) return FALSE; #endif #ifndef DISABLE_EVENT client_static_cbinfo->event_action = tb ? tb->event_action : NULL; #endif /* There doesn't seem to be a built-in timeout on connection. */ DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); sigalrm_seen = FALSE; ALARM(ob->command_timeout); rc = SSL_connect(exim_client_ctx->ssl); ALARM_CLR(0); #ifdef SUPPORT_DANE if (conn_args->dane) DANESSL_cleanup(exim_client_ctx->ssl); #endif if (rc <= 0) { tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr); return FALSE; } DEBUG(D_tls) { debug_printf("SSL_connect succeeded\n"); #ifdef EXIM_HAVE_OPENSSL_KEYLOG { BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE); SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl)); BIO_free(bp); } #endif } #ifdef EXPERIMENTAL_TLS_RESUME tls_client_resume_posthandshake(exim_client_ctx, tlsp); #endif #ifdef SSL_get_extms_support tlsp->ext_master_secret = SSL_get_extms_support(exim_client_ctx->ssl) == 1; #endif peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn)); tlsp->ver = tlsver_name(exim_client_ctx->ssl); tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, tlsp->ver, &tlsp->bits); tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl); /* Record the certificate we presented */ { X509 * crt = SSL_get_certificate(exim_client_ctx->ssl); tlsp->ourcert = crt ? X509_dup(crt) : NULL; } /*XXX will this work with continued-TLS? */ /* Channel-binding info for authenticators */ { uschar c, * s; size_t len = SSL_get_finished(exim_client_ctx->ssl, &c, 0); int old_pool = store_pool; SSL_get_finished(exim_client_ctx->ssl, s = store_get((int)len, TRUE), len); store_pool = POOL_PERM; tlsp->channelbinding = b64encode_taint(CUS s, (int)len, TRUE); store_pool = old_pool; DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage %p %p\n", tlsp->channelbinding, tlsp); } tlsp->active.sock = cctx->sock; tlsp->active.tls_ctx = exim_client_ctx; cctx->tls_ctx = exim_client_ctx; return TRUE; } static BOOL tls_refill(unsigned lim) { int error; int inbytes; DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl, ssl_xfer_buffer, ssl_xfer_buffer_size); if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout); inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, MIN(ssl_xfer_buffer_size, lim)); error = SSL_get_error(server_ssl, inbytes); if (smtp_receive_timeout > 0) ALARM_CLR(0); if (had_command_timeout) /* set by signal handler */ smtp_command_timeout_exit(); /* does not return */ if (had_command_sigterm) smtp_command_sigterm_exit(); if (had_data_timeout) smtp_data_timeout_exit(); if (had_data_sigint) smtp_data_sigint_exit(); /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been closed down, not that the socket itself has been closed down. Revert to non-SSL handling. */ switch(error) { case SSL_ERROR_NONE: break; case SSL_ERROR_ZERO_RETURN: DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN) SSL_shutdown(server_ssl); tls_close(NULL, TLS_NO_SHUTDOWN); return FALSE; /* Handle genuine errors */ case SSL_ERROR_SSL: ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring); ssl_xfer_error = TRUE; return FALSE; default: DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL) debug_printf(" - syscall %s\n", strerror(errno)); ssl_xfer_error = TRUE; return FALSE; } #ifndef DISABLE_DKIM dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); #endif ssl_xfer_buffer_hwm = inbytes; ssl_xfer_buffer_lwm = 0; return TRUE; } /************************************************* * TLS version of getc * *************************************************/ /* This gets the next byte from the TLS input buffer. If the buffer is empty, it refills the buffer via the SSL reading function. Arguments: lim Maximum amount to read/buffer Returns: the next character or EOF Only used by the server-side TLS. */ int tls_getc(unsigned lim) { if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) if (!tls_refill(lim)) return ssl_xfer_error ? EOF : smtp_getc(lim); /* Something in the buffer; return next uschar */ return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; } uschar * tls_getbuf(unsigned * len) { unsigned size; uschar * buf; if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) if (!tls_refill(*len)) { if (!ssl_xfer_error) return smtp_getbuf(len); *len = 0; return NULL; } if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len) size = *len; buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm]; ssl_xfer_buffer_lwm += size; *len = size; return buf; } void tls_get_cache() { #ifndef DISABLE_DKIM int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm; if (n > 0) dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n); #endif } BOOL tls_could_read(void) { return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0; } /************************************************* * Read bytes from TLS channel * *************************************************/ /* Arguments: ct_ctx client context pointer, or NULL for the one global server context buff buffer of data len size of buffer Returns: the number of bytes read -1 after a failed read, including EOF Only used by the client-side TLS. */ int tls_read(void * ct_ctx, uschar *buff, size_t len) { SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl; int inbytes; int error; DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl, buff, (unsigned int)len); inbytes = SSL_read(ssl, CS buff, len); error = SSL_get_error(ssl, inbytes); if (error == SSL_ERROR_ZERO_RETURN) { DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); return -1; } else if (error != SSL_ERROR_NONE) return -1; return inbytes; } /************************************************* * Write bytes down TLS channel * *************************************************/ /* Arguments: ct_ctx client context pointer, or NULL for the one global server context buff buffer of data len number of bytes more further data expected soon Returns: the number of bytes after a successful write, -1 after a failed write Used by both server-side and client-side TLS. Calling with len zero and more unset will flush buffered writes; buff can be null for this case. */ int tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more) { size_t olen = len; int outbytes, error; SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl; static gstring * server_corked = NULL; gstring ** corkedp = ct_ctx ? &((exim_openssl_client_tls_ctx *)ct_ctx)->corked : &server_corked; gstring * corked = *corkedp; DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__, buff, (unsigned long)len, more ? ", more" : ""); /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when "more" is notified. This hack is only ok if small amounts are involved AND only one stream does it, in one context (i.e. no store reset). Currently it is used for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. We support callouts done by the server process by using a separate client context for the stashed information. */ /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's a store reset there, so use POOL_PERM. */ /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */ if ((more || corked)) { if (!len) buff = US &error; /* dummy just so that string_catn is ok */ #ifndef DISABLE_PIPE_CONNECT int save_pool = store_pool; store_pool = POOL_PERM; #endif corked = string_catn(corked, buff, len); #ifndef DISABLE_PIPE_CONNECT store_pool = save_pool; #endif if (more) { *corkedp = corked; return len; } buff = CUS corked->s; len = corked->ptr; *corkedp = NULL; } for (int left = len; left > 0;) { DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left); outbytes = SSL_write(ssl, CS buff, left); error = SSL_get_error(ssl, outbytes); DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); switch (error) { case SSL_ERROR_NONE: /* the usual case */ left -= outbytes; buff += outbytes; break; case SSL_ERROR_SSL: ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); return -1; case SSL_ERROR_ZERO_RETURN: log_write(0, LOG_MAIN, "SSL channel closed on write"); return -1; case SSL_ERROR_SYSCALL: log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s", sender_fullhost ? sender_fullhost : US"", strerror(errno)); return -1; default: log_write(0, LOG_MAIN, "SSL_write error %d", error); return -1; } } return olen; } /************************************************* * Close down a TLS session * *************************************************/ /* This is also called from within a delivery subprocess forked from the daemon, to shut down the TLS library, without actually doing a shutdown (which would tamper with the SSL session in the parent process). Arguments: ct_ctx client TLS context pointer, or NULL for the one global server context shutdown 1 if TLS close-alert is to be sent, 2 if also response to be waited for Returns: nothing Used by both server-side and client-side TLS. */ void tls_close(void * ct_ctx, int shutdown) { exim_openssl_client_tls_ctx * o_ctx = ct_ctx; SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx; SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl; int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock; if (*fdp < 0) return; /* TLS was not active */ if (shutdown) { int rc; DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n", shutdown > 1 ? " (with response-wait)" : ""); if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */ && shutdown > 1) { ALARM(2); rc = SSL_shutdown(*sslp); /* wait for response */ ALARM_CLR(0); } if (rc < 0) DEBUG(D_tls) { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); debug_printf("SSL_shutdown: %s\n", ssl_errstring); } } if (!o_ctx) /* server side */ { #ifndef DISABLE_OCSP sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free); server_static_cbinfo->verify_stack = NULL; #endif receive_getc = smtp_getc; receive_getbuf = smtp_getbuf; receive_get_cache = smtp_get_cache; receive_ungetc = smtp_ungetc; receive_feof = smtp_feof; receive_ferror = smtp_ferror; receive_smtp_buffered = smtp_buffered; tls_in.active.tls_ctx = NULL; tls_in.sni = NULL; /* Leave bits, peercert, cipher, peerdn, certificate_verified set, for logging */ } SSL_CTX_free(*ctxp); SSL_free(*sslp); *ctxp = NULL; *sslp = NULL; *fdp = -1; } /************************************************* * Let tls_require_ciphers be checked at startup * *************************************************/ /* The tls_require_ciphers option, if set, must be something which the library can parse. Returns: NULL on success, or error message */ uschar * tls_validate_require_cipher(void) { SSL_CTX *ctx; uschar *s, *expciphers, *err; tls_openssl_init(); if (!(tls_require_ciphers && *tls_require_ciphers)) return NULL; if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers, &err)) return US"failed to expand tls_require_ciphers"; if (!(expciphers && *expciphers)) return NULL; /* normalisation ripped from above */ s = expciphers; while (*s != 0) { if (*s == '_') *s = '-'; s++; } err = NULL; #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD if (!(ctx = SSL_CTX_new(TLS_server_method()))) #else if (!(ctx = SSL_CTX_new(SSLv23_server_method()))) #endif { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring); } DEBUG(D_tls) debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers); if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) { ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s", expciphers, ssl_errstring); } SSL_CTX_free(ctx); return err; } /************************************************* * Report the library versions. * *************************************************/ /* There have historically been some issues with binary compatibility in OpenSSL libraries; if Exim (like many other applications) is built against one version of OpenSSL but the run-time linker picks up another version, it can result in serious failures, including crashing with a SIGSEGV. So report the version found by the compiler and the run-time version. Note: some OS vendors backport security fixes without changing the version number/string, and the version date remains unchanged. The _build_ date will change, so we can more usefully assist with version diagnosis by also reporting the build date. Arguments: a FILE* to print the results to Returns: nothing */ void tls_version_report(FILE *f) { fprintf(f, "Library version: OpenSSL: Compile: %s\n" " Runtime: %s\n" " : %s\n", OPENSSL_VERSION_TEXT, SSLeay_version(SSLEAY_VERSION), SSLeay_version(SSLEAY_BUILT_ON)); /* third line is 38 characters for the %s and the line is 73 chars long; the OpenSSL output includes a "built on: " prefix already. */ } /************************************************* * Random number generation * *************************************************/ /* Pseudo-random number generation. The result is not expected to be cryptographically strong but not so weak that someone will shoot themselves in the foot using it as a nonce in input in some email header scheme or whatever weirdness they'll twist this into. The result should handle fork() and avoid repeating sequences. OpenSSL handles that for us. Arguments: max range maximum Returns a random number in range [0, max-1] */ int vaguely_random_number(int max) { unsigned int r; int i, needed_len; static pid_t pidlast = 0; pid_t pidnow; uschar smallbuf[sizeof(r)]; if (max <= 1) return 0; pidnow = getpid(); if (pidnow != pidlast) { /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state is unique for each thread", this doesn't apparently apply across processes, so our own warning from vaguely_random_number_fallback() applies here too. Fix per PostgreSQL. */ if (pidlast != 0) RAND_cleanup(); pidlast = pidnow; } /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */ if (!RAND_status()) { randstuff r; gettimeofday(&r.tv, NULL); r.p = getpid(); RAND_seed(US (&r), sizeof(r)); } /* We're after pseudo-random, not random; if we still don't have enough data in the internal PRNG then our options are limited. We could sleep and hope for entropy to come along (prayer technique) but if the system is so depleted in the first place then something is likely to just keep taking it. Instead, we'll just take whatever little bit of pseudo-random we can still manage to get. */ needed_len = sizeof(r); /* Don't take 8 times more entropy than needed if int is 8 octets and we were asked for a number less than 10. */ for (r = max, i = 0; r; ++i) r >>= 1; i = (i + 7) / 8; if (i < needed_len) needed_len = i; #ifdef EXIM_HAVE_RAND_PSEUDO /* We do not care if crypto-strong */ i = RAND_pseudo_bytes(smallbuf, needed_len); #else i = RAND_bytes(smallbuf, needed_len); #endif if (i < 0) { DEBUG(D_all) debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n"); return vaguely_random_number_fallback(max); } r = 0; for (uschar * p = smallbuf; needed_len; --needed_len, ++p) r = 256 * r + *p; /* We don't particularly care about weighted results; if someone wants smooth distribution and cares enough then they should submit a patch then. */ return r % max; } /************************************************* * OpenSSL option parse * *************************************************/ /* Parse one option for tls_openssl_options_parse below Arguments: name one option name value place to store a value for it Returns success or failure in parsing */ static BOOL tls_openssl_one_option_parse(uschar *name, long *value) { int first = 0; int last = exim_openssl_options_size; while (last > first) { int middle = (first + last)/2; int c = Ustrcmp(name, exim_openssl_options[middle].name); if (c == 0) { *value = exim_openssl_options[middle].value; return TRUE; } else if (c > 0) first = middle + 1; else last = middle; } return FALSE; } /************************************************* * OpenSSL option parsing logic * *************************************************/ /* OpenSSL has a number of compatibility options which an administrator might reasonably wish to set. Interpret a list similarly to decode_bits(), so that we look like log_selector. Arguments: option_spec the administrator-supplied string of options results ptr to long storage for the options bitmap Returns success or failure */ BOOL tls_openssl_options_parse(uschar *option_spec, long *results) { long result, item; uschar * exp, * end; uschar keep_c; BOOL adding, item_parsed; /* Server: send no (<= TLS1.2) session tickets */ result = SSL_OP_NO_TICKET; /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed from default because it increases BEAST susceptibility. */ #ifdef SSL_OP_NO_SSLv2 result |= SSL_OP_NO_SSLv2; #endif #ifdef SSL_OP_NO_SSLv3 result |= SSL_OP_NO_SSLv3; #endif #ifdef SSL_OP_SINGLE_DH_USE result |= SSL_OP_SINGLE_DH_USE; #endif #ifdef SSL_OP_NO_RENEGOTIATION result |= SSL_OP_NO_RENEGOTIATION; #endif if (!option_spec) { *results = result; return TRUE; } if (!expand_check(option_spec, US"openssl_options", &exp, &end)) return FALSE; for (uschar * s = exp; *s; /**/) { while (isspace(*s)) ++s; if (*s == '\0') break; if (*s != '+' && *s != '-') { DEBUG(D_tls) debug_printf("malformed openssl option setting: " "+ or - expected but found \"%s\"\n", s); return FALSE; } adding = *s++ == '+'; for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ; keep_c = *end; *end = '\0'; item_parsed = tls_openssl_one_option_parse(s, &item); *end = keep_c; if (!item_parsed) { DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s); return FALSE; } DEBUG(D_tls) debug_printf("openssl option, %s %08lx: %08lx (%s)\n", adding ? "adding to " : "removing from", result, item, s); if (adding) result |= item; else result &= ~item; s = end; } *results = result; return TRUE; } #endif /*!MACRO_PREDEF*/ /* vi: aw ai sw=2 */ /* End of tls-openssl.c */