X-Git-Url: https://vcs.fsf.org/?p=exim.git;a=blobdiff_plain;f=src%2Fsrc%2Ftls-gnu.c;h=b0b67d820824b214ff53df7fb22b9483270e115e;hp=9c9e437759ef7c87a5231665cc66e608f1ca1003;hb=4466248715466b6f251454283642b74de65e9d9a;hpb=26dd5a9508b34248285532c97a135b64aab1ec06 diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c index 9c9e43775..b0b67d820 100644 --- a/src/src/tls-gnu.c +++ b/src/src/tls-gnu.c @@ -1,109 +1,219 @@ -/* $Cambridge: exim/src/src/tls-gnu.c,v 1.3 2004/12/21 09:26:31 ph10 Exp $ */ - /************************************************* * Exim - an Internet mail transport agent * *************************************************/ -/* Copyright (c) University of Cambridge 1995 - 2004 */ +/* Copyright (c) University of Cambridge 1995 - 2014 */ /* See the file NOTICE for conditions of use and distribution. */ -/* This module provides TLS (aka SSL) support for Exim using the GnuTLS -library. It is #included into tls.c when that library is used. The code herein -is based on a patch that was contributed by Nikos Mavroyanopoulos. +/* Copyright (c) Phil Pennock 2012 */ + +/* This file provides TLS/SSL support for Exim using the GnuTLS library, +one of the available supported implementations. This file is #included into +tls.c when USE_GNUTLS has been set. + +The code herein is a revamp of GnuTLS integration using the current APIs; the +original tls-gnu.c was based on a patch which was contributed by Nikos +Mavroyanopoulos. The revamp is partially a rewrite, partially cut&paste as +appropriate. -No cryptographic code is included in Exim. All this module does is to call -functions from the GnuTLS library. */ +APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3, +which is not widely deployed by OS vendors. Will note issues below, which may +assist in updating the code in the future. Another sources of hints is +mod_gnutls for Apache (SNI callback registration and handling). +Keeping client and server variables more split than before and is currently +the norm, in anticipation of TLS in ACL callouts. -/* Heading stuff for GnuTLS */ +I wanted to switch to gnutls_certificate_set_verify_function() so that +certificate rejection could happen during handshake where it belongs, rather +than being dropped afterwards, but that was introduced in 2.10.0 and Debian +(6.0.5) is still on 2.8.6. So for now we have to stick with sub-par behaviour. + +(I wasn't looking for libraries quite that old, when updating to get rid of +compiler warnings of deprecated APIs. If it turns out that a lot of the rest +require current GnuTLS, then we'll drop support for the ancient libraries). +*/ #include +/* needed for cert checks in verification and DN extraction: */ #include +/* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */ +#include +/* needed to disable PKCS11 autoload unless requested */ +#if GNUTLS_VERSION_NUMBER >= 0x020c00 +# include +#endif +#ifdef EXPERIMENTAL_OCSP +# include +#endif + +/* GnuTLS 2 vs 3 + +GnuTLS 3 only: + gnutls_global_set_audit_log_function() + +Changes: + gnutls_certificate_verify_peers2(): is new, drop the 2 for old version +*/ +/* Local static variables for GnuTLS */ -#define UNKNOWN_NAME "unknown" -#define DH_BITS 768 -#define RSA_BITS 512 +/* Values for verify_requirement */ -/* Values for verify_requirment and initialized */ +enum peer_verify_requirement { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED }; -enum { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED }; -enum { INITIALIZED_NOT, INITIALIZED_SERVER, INITIALIZED_CLIENT }; +/* This holds most state for server or client; with this, we can set up an +outbound TLS-enabled connection in an ACL callout, while not stomping all +over the TLS variables available for expansion. -/* Local static variables for GNUTLS */ +Some of these correspond to variables in globals.c; those variables will +be set to point to content in one of these instances, as appropriate for +the stage of the process lifetime. -static BOOL initialized = INITIALIZED_NOT; -static host_item *client_host; +Not handled here: global tls_channelbinding_b64. +*/ -static gnutls_rsa_params rsa_params = NULL; -static gnutls_dh_params dh_params = NULL; +typedef struct exim_gnutls_state { + gnutls_session_t session; + gnutls_certificate_credentials_t x509_cred; + gnutls_priority_t priority_cache; + enum peer_verify_requirement verify_requirement; + int fd_in; + int fd_out; + BOOL peer_cert_verified; + BOOL trigger_sni_changes; + BOOL have_set_peerdn; + const struct host_item *host; + gnutls_x509_crt_t peercert; + uschar *peerdn; + uschar *ciphersuite; + uschar *received_sni; + + const uschar *tls_certificate; + const uschar *tls_privatekey; + const uschar *tls_sni; /* client send only, not received */ + const uschar *tls_verify_certificates; + const uschar *tls_crl; + const uschar *tls_require_ciphers; + uschar *exp_tls_certificate; + uschar *exp_tls_privatekey; + uschar *exp_tls_sni; + uschar *exp_tls_verify_certificates; + uschar *exp_tls_crl; + uschar *exp_tls_require_ciphers; + uschar *exp_tls_ocsp_file; + + tls_support *tlsp; /* set in tls_init() */ + + uschar *xfer_buffer; + int xfer_buffer_lwm; + int xfer_buffer_hwm; + int xfer_eof; + int xfer_error; +} exim_gnutls_state_st; + +static const exim_gnutls_state_st exim_gnutls_state_init = { + NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE, + NULL, NULL, NULL, NULL, + NULL, NULL, NULL, NULL, NULL, NULL, + NULL, NULL, NULL, NULL, NULL, NULL, NULL, + NULL, + NULL, 0, 0, 0, 0, +}; -static gnutls_certificate_server_credentials x509_cred = NULL; -static gnutls_session tls_session = NULL; +/* Not only do we have our own APIs which don't pass around state, assuming +it's held in globals, GnuTLS doesn't appear to let us register callback data +for callbacks, or as part of the session, so we have to keep a "this is the +context we're currently dealing with" pointer and rely upon being +single-threaded to keep from processing data on an inbound TLS connection while +talking to another TLS connection for an outbound check. This does mean that +there's no way for heart-beats to be responded to, for the duration of the +second connection. */ -static char ssl_errstring[256]; +static exim_gnutls_state_st state_server, state_client; -static int ssl_session_timeout = 200; -static int verify_requirement; +/* dh_params are initialised once within the lifetime of a process using TLS; +if we used TLS in a long-lived daemon, we'd have to reconsider this. But we +don't want to repeat this. */ -/* Priorities for TLS algorithms to use. At present, only the cipher priority -vector can be altered. */ +static gnutls_dh_params_t dh_server_params = NULL; -static const int protocol_priority[16] = { GNUTLS_TLS1, GNUTLS_SSL3, 0 }; +/* No idea how this value was chosen; preserving it. Default is 3600. */ -static const int kx_priority[16] = { - GNUTLS_KX_RSA, - GNUTLS_KX_DHE_DSS, - GNUTLS_KX_DHE_RSA, - GNUTLS_KX_RSA_EXPORT, - 0 }; +static const int ssl_session_timeout = 200; -static int default_cipher_priority[16] = { - GNUTLS_CIPHER_AES_256_CBC, - GNUTLS_CIPHER_AES_128_CBC, - GNUTLS_CIPHER_3DES_CBC, - GNUTLS_CIPHER_ARCFOUR_128, - 0 }; +static const char * const exim_default_gnutls_priority = "NORMAL"; -static int cipher_priority[16]; +/* Guard library core initialisation */ -static const int mac_priority[16] = { - GNUTLS_MAC_SHA, - GNUTLS_MAC_MD5, - 0 }; +static BOOL exim_gnutls_base_init_done = FALSE; -static const int comp_priority[16] = { GNUTLS_COMP_NULL, 0 }; -static const int cert_type_priority[16] = { GNUTLS_CRT_X509, 0 }; -/* Tables of cipher names and equivalent numbers */ +/* ------------------------------------------------------------------------ */ +/* macros */ -typedef struct pri_item { - uschar *name; - int *values; -} pri_item; +#define MAX_HOST_LEN 255 -static int arcfour_128_codes[] = { GNUTLS_CIPHER_ARCFOUR_128, 0 }; -static int arcfour_40_codes[] = { GNUTLS_CIPHER_ARCFOUR_40, 0 }; -static int arcfour_codes[] = { GNUTLS_CIPHER_ARCFOUR_128, - GNUTLS_CIPHER_ARCFOUR_40, 0 }; -static int aes_256_codes[] = { GNUTLS_CIPHER_AES_256_CBC, 0 }; -static int aes_128_codes[] = { GNUTLS_CIPHER_AES_128_CBC, 0 }; -static int aes_codes[] = { GNUTLS_CIPHER_AES_256_CBC, - GNUTLS_CIPHER_AES_128_CBC, 0 }; -static int des3_codes[] = { GNUTLS_CIPHER_3DES_CBC, 0 }; +/* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup +the library logging; a value less than 0 disables the calls to set up logging +callbacks. */ +#ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL +#define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1 +#endif -static pri_item cipher_index[] = { - { US"ARCFOUR_128", arcfour_128_codes }, - { US"ARCFOUR_40", arcfour_40_codes }, - { US"ARCFOUR", arcfour_codes }, - { US"AES_256", aes_256_codes }, - { US"AES_128", aes_128_codes }, - { US"AES", aes_codes }, - { US"3DES", des3_codes } -}; +#ifndef EXIM_CLIENT_DH_MIN_BITS +#define EXIM_CLIENT_DH_MIN_BITS 1024 +#endif + +/* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we +can ask for a bit-strength. Without that, we stick to the constant we had +before, for now. */ +#ifndef EXIM_SERVER_DH_BITS_PRE2_12 +#define EXIM_SERVER_DH_BITS_PRE2_12 1024 +#endif + +#define exim_gnutls_err_check(Label) do { \ + if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0) + +#define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname) + +#if GNUTLS_VERSION_NUMBER >= 0x020c00 +#define HAVE_GNUTLS_SESSION_CHANNEL_BINDING +#define HAVE_GNUTLS_SEC_PARAM_CONSTANTS +#define HAVE_GNUTLS_RND +/* The security fix we provide with the gnutls_allow_auto_pkcs11 option + * (4.82 PP/09) introduces a compatibility regression. The symbol simply + * isn't available sometimes, so this needs to become a conditional + * compilation; the sanest way to deal with this being a problem on + * older OSes is to block it in the Local/Makefile with this compiler + * definition */ +#ifndef AVOID_GNUTLS_PKCS11 +#define HAVE_GNUTLS_PKCS11 +#endif /* AVOID_GNUTLS_PKCS11 */ +#endif + + + + +/* ------------------------------------------------------------------------ */ +/* Callback declarations */ + +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +static void exim_gnutls_logger_cb(int level, const char *message); +#endif + +static int exim_sni_handling_cb(gnutls_session_t session); +#ifdef EXPERIMENTAL_OCSP +static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr, + gnutls_datum_t * ocsp_response); +#endif + +/* ------------------------------------------------------------------------ */ +/* Static functions */ + /************************************************* * Handle TLS error * *************************************************/ @@ -117,161 +227,180 @@ some shared functions. Argument: prefix text to include in the logged error + msg additional error string (may be NULL) + usually obtained from gnutls_strerror() host NULL if setting up a server; the connected host if setting up a client - err a GnuTLS error number, or 0 if local error Returns: OK/DEFER/FAIL */ static int -tls_error(uschar *prefix, host_item *host, int err) +tls_error(const uschar *prefix, const char *msg, const host_item *host) { -uschar *errtext = US""; -if (err != 0) errtext = string_sprintf(": %s", gnutls_strerror(err)); -if (host == NULL) +if (host) { - log_write(0, LOG_MAIN, "TLS error on connection from %s (%s)%s", - (sender_fullhost != NULL)? sender_fullhost : US "local process", - prefix, errtext); - return DEFER; + log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s", + host->name, host->address, prefix, msg ? ": " : "", msg ? msg : ""); + return FAIL; } else { - log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s", - host->name, host->address, prefix, errtext); - return FAIL; + uschar *conn_info = smtp_get_connection_info(); + if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) + conn_info += 5; + log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s", + conn_info, prefix, msg ? ": " : "", msg ? msg : ""); + return DEFER; } } + /************************************************* -* Verify certificate * +* Deal with logging errors during I/O * *************************************************/ -/* Called after a successful handshake, when certificate verification is -required or optional, for both server and client. +/* We have to get the identity of the peer from saved data. -Arguments: - session GNUTLS session - error where to put text giving a reason for failure +Argument: + state the current GnuTLS exim state container + rc the GnuTLS error code, or 0 if it's a local error + when text identifying read or write + text local error text when ec is 0 -Returns: TRUE/FALSE +Returns: nothing */ -static BOOL -verify_certificate(gnutls_session session, uschar **error) +static void +record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text) { -int verify; -uschar *dn_string = US""; -const gnutls_datum *cert; -unsigned int cert_size = 0; +const char *msg; -*error = NULL; +if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED) + msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc), + US gnutls_alert_get_name(gnutls_alert_get(state->session))); +else + msg = gnutls_strerror(rc); -/* Get the peer's certificate. If it sent one, extract it's DN, and then -attempt to verify the certificate. If no certificate is supplied, verification -is forced to fail. */ +tls_error(when, msg, state->host); +} -cert = gnutls_certificate_get_peers(session, &cert_size); -if (cert != NULL) - { - uschar buff[1024]; - gnutls_x509_crt gcert; - gnutls_x509_crt_init(&gcert); - dn_string = US"unknown"; - if (gnutls_x509_crt_import(gcert, cert, GNUTLS_X509_FMT_DER) == 0) - { - size_t bufsize = sizeof(buff); - if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0) - dn_string = string_copy_malloc(buff); - } - verify = gnutls_certificate_verify_peers(session); - } -else - { - DEBUG(D_tls) debug_printf("no peer certificate supplied\n"); - verify = GNUTLS_CERT_INVALID; - *error = US"not supplied"; - } +/************************************************* +* Set various Exim expansion vars * +*************************************************/ -/* Handle the result of verification. INVALID seems to be set as well -as REVOKED, but leave the test for both. */ +#define exim_gnutls_cert_err(Label) do { \ + if (rc != GNUTLS_E_SUCCESS) { \ + DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \ + return rc; } } while (0) -if ((verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0) - { - tls_certificate_verified = FALSE; - if (*error == NULL) *error = ((verify & GNUTLS_CERT_REVOKED) != 0)? - US"revoked" : US"invalid"; - if (verify_requirement == VERIFY_REQUIRED) - { - DEBUG(D_tls) debug_printf("TLS certificate verification failed (%s): " - "peerdn=%s\n", *error, dn_string); - gnutls_alert_send(session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); - return FALSE; /* reject */ - } - DEBUG(D_tls) debug_printf("TLS certificate verify failure (%s) overridden " - "(host in tls_try_verify_hosts): peerdn=%s\n", *error, dn_string); - } -else - { - tls_certificate_verified = TRUE; - DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n", - dn_string); - } +static int +import_cert(const gnutls_datum * cert, gnutls_x509_crt_t * crtp) +{ +int rc; -tls_peerdn = dn_string; -return TRUE; /* accept */ -} +rc = gnutls_x509_crt_init(crtp); +exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)"); +rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER); +exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]"); +return rc; +} +#undef exim_gnutls_cert_err -/************************************************* -* Write/read datum to/from file * -*************************************************/ -/* These functions are used for saving and restoring the RSA and D-H parameters -for use by all Exim processes. Data that is read is placed in malloc'd store -because that's what happens for newly generated data. +/* We set various Exim global variables from the state, once a session has +been established. With TLS callouts, may need to change this to stack +variables, or just re-call it with the server state after client callout +has finished. -Arguments: - fd the file descriptor - d points to the datum +Make sure anything set here is unset in tls_getc(). + +Sets: + tls_active fd + tls_bits strength indicator + tls_certificate_verified bool indicator + tls_channelbinding_b64 for some SASL mechanisms + tls_cipher a string + tls_peercert pointer to library internal + tls_peerdn a string + tls_sni a (UTF-8) string + tls_ourcert pointer to library internal -returns: FALSE on error (errno set) +Argument: + state the relevant exim_gnutls_state_st * */ -static BOOL -write_datum(int fd, gnutls_datum *d) +static void +extract_exim_vars_from_tls_state(exim_gnutls_state_st * state) { -if (write(fd, &(d->size), sizeof(d->size)) != sizeof(d->size)) return FALSE; -if (write(fd, d->data, d->size) != d->size) return FALSE; -return TRUE; +gnutls_cipher_algorithm_t cipher; +#ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING +int old_pool; +int rc; +gnutls_datum_t channel; +#endif +tls_support * tlsp = state->tlsp; + +tlsp->active = state->fd_out; + +cipher = gnutls_cipher_get(state->session); +/* returns size in "bytes" */ +tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8; + +tlsp->cipher = state->ciphersuite; + +DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite); + +tlsp->certificate_verified = state->peer_cert_verified; + +/* note that tls_channelbinding_b64 is not saved to the spool file, since it's +only available for use for authenticators while this TLS session is running. */ + +tls_channelbinding_b64 = NULL; +#ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING +channel.data = NULL; +channel.size = 0; +rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel); +if (rc) { + DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); +} else { + old_pool = store_pool; + store_pool = POOL_PERM; + tls_channelbinding_b64 = auth_b64encode(channel.data, (int)channel.size); + store_pool = old_pool; + DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n"); } +#endif +/* peercert is set in peer_status() */ +tlsp->peerdn = state->peerdn; +tlsp->sni = state->received_sni; -static BOOL -read_datum(int fd, gnutls_datum *d) -{ -if (read(fd, &(d->size), sizeof(d->size)) != sizeof(d->size)) return FALSE; -d->data = malloc(d->size); -if (d->data == NULL) return FALSE; -if (read(fd, d->data, d->size) != d->size) return FALSE; -return TRUE; +/* record our certificate */ + { + const gnutls_datum * cert = gnutls_certificate_get_ours(state->session); + gnutls_x509_crt_t crt; + + tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL; + } } + /************************************************* -* Setup up RSA and DH parameters * +* Setup up DH parameters * *************************************************/ -/* Generating the RSA and D-H parameters takes a long time. They only need to +/* Generating the D-H parameters may take a long time. They only need to be re-generated every so often, depending on security policy. What we do is to keep these parameters in a file in the spool directory. If the file does not exist, we generate them. This means that it is easy to cause a regeneration. @@ -281,125 +410,545 @@ file is never present. If two processes both compute some new parameters, you waste a bit of effort, but it doesn't seem worth messing around with locking to prevent this. -Argument: - host NULL for server, server for client (for error handling) - Returns: OK/DEFER/FAIL */ static int -init_rsa_dh(host_item *host) +init_server_dh(void) { -int fd, ret; -gnutls_datum m, e, d, p, q, u, prime, generator; -uschar filename[200]; - -/* Initialize the data structures for holding the parameters */ +int fd, rc; +unsigned int dh_bits; +gnutls_datum m; +uschar filename_buf[PATH_MAX]; +uschar *filename = NULL; +size_t sz; +uschar *exp_tls_dhparam; +BOOL use_file_in_spool = FALSE; +BOOL use_fixed_file = FALSE; +host_item *host = NULL; /* dummy for macros */ + +DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n"); + +rc = gnutls_dh_params_init(&dh_server_params); +exim_gnutls_err_check(US"gnutls_dh_params_init"); + +m.data = NULL; +m.size = 0; + +if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam)) + return DEFER; -ret = gnutls_rsa_params_init(&rsa_params); -if (ret < 0) return tls_error(US"init rsa_params", host, ret); +if (!exp_tls_dhparam) + { + DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n"); + m.data = US std_dh_prime_default(); + m.size = Ustrlen(m.data); + } +else if (Ustrcmp(exp_tls_dhparam, "historic") == 0) + use_file_in_spool = TRUE; +else if (Ustrcmp(exp_tls_dhparam, "none") == 0) + { + DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); + return OK; + } +else if (exp_tls_dhparam[0] != '/') + { + m.data = US std_dh_prime_named(exp_tls_dhparam); + if (m.data == NULL) + return tls_error(US"No standard prime named", CS exp_tls_dhparam, NULL); + m.size = Ustrlen(m.data); + } +else + { + use_fixed_file = TRUE; + filename = exp_tls_dhparam; + } -ret = gnutls_dh_params_init(&dh_params); -if (ret < 0) return tls_error(US"init dh_params", host, ret); +if (m.data) + { + rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); + exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); + DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n"); + return OK; + } -/* Set up the name of the cache file */ +#ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS +/* If you change this constant, also change dh_param_fn_ext so that we can use a +different filename and ensure we have sufficient bits. */ +dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL); +if (!dh_bits) + return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL); +DEBUG(D_tls) + debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n", + dh_bits); +#else +dh_bits = EXIM_SERVER_DH_BITS_PRE2_12; +DEBUG(D_tls) + debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n", + dh_bits); +#endif + +/* Some clients have hard-coded limits. */ +if (dh_bits > tls_dh_max_bits) + { + DEBUG(D_tls) + debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n", + tls_dh_max_bits); + dh_bits = tls_dh_max_bits; + } -if (!string_format(filename, sizeof(filename), "%s/gnutls-params", - spool_directory)) - return tls_error(US"overlong filename", host, 0); +if (use_file_in_spool) + { + if (!string_format(filename_buf, sizeof(filename_buf), + "%s/gnutls-params-%d", spool_directory, dh_bits)) + return tls_error(US"overlong filename", NULL, NULL); + filename = filename_buf; + } -/* Open the cache file for reading. If this fails because of a non-existent -file, compute a new set of parameters, write them to a temporary file, and then -rename that file as the cache file. Other opening errors are bad. */ +/* Open the cache file for reading and if successful, read it and set up the +parameters. */ fd = Uopen(filename, O_RDONLY, 0); -if (fd < 0) +if (fd >= 0) { - unsigned int rsa_bits = RSA_BITS; - unsigned int dh_bits = DH_BITS; - uschar tempfilename[sizeof(filename) + 10]; + struct stat statbuf; + FILE *fp; + int saved_errno; + + if (fstat(fd, &statbuf) < 0) /* EIO */ + { + saved_errno = errno; + (void)close(fd); + return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL); + } + if (!S_ISREG(statbuf.st_mode)) + { + (void)close(fd); + return tls_error(US"TLS cache not a file", NULL, NULL); + } + fp = fdopen(fd, "rb"); + if (!fp) + { + saved_errno = errno; + (void)close(fd); + return tls_error(US"fdopen(TLS cache stat fd) failed", + strerror(saved_errno), NULL); + } + + m.size = statbuf.st_size; + m.data = malloc(m.size); + if (m.data == NULL) + { + fclose(fp); + return tls_error(US"malloc failed", strerror(errno), NULL); + } + sz = fread(m.data, m.size, 1, fp); + if (!sz) + { + saved_errno = errno; + fclose(fp); + free(m.data); + return tls_error(US"fread failed", strerror(saved_errno), NULL); + } + fclose(fp); + + rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); + free(m.data); + exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); + DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename); + } - if (errno != ENOENT) - return tls_error(string_open_failed(errno, "%s for reading", filename), - host, 0); +/* If the file does not exist, fall through to compute new data and cache it. +If there was any other opening error, it is serious. */ + +else if (errno == ENOENT) + { + rc = -1; + DEBUG(D_tls) + debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename); + } +else + return tls_error(string_open_failed(errno, "\"%s\" for reading", filename), + NULL, NULL); - DEBUG(D_tls) debug_printf("generating %d bit RSA key...\n", RSA_BITS); - ret = gnutls_rsa_params_generate2(rsa_params, RSA_BITS); - if (ret < 0) return tls_error(US"RSA key generation", host, ret); +/* If ret < 0, either the cache file does not exist, or the data it contains +is not useful. One particular case of this is when upgrading from an older +release of Exim in which the data was stored in a different format. We don't +try to be clever and support both formats; we just regenerate new data in this +case. */ - DEBUG(D_tls) debug_printf("generating %d bit Diffie-Hellman key...\n", - DH_BITS); - ret = gnutls_dh_params_generate2(dh_params, DH_BITS); - if (ret < 0) return tls_error(US"D-H key generation", host, ret); +if (rc < 0) + { + uschar *temp_fn; + unsigned int dh_bits_gen = dh_bits; - /* Write the parameters to a file in the spool directory so that we - can use them from other Exim processes. */ + if ((PATH_MAX - Ustrlen(filename)) < 10) + return tls_error(US"Filename too long to generate replacement", + CS filename, NULL); - sprintf(CS tempfilename, "%s-%d", filename, (int)getpid()); - fd = Uopen(tempfilename, O_WRONLY|O_CREAT, 0400); + temp_fn = string_copy(US "%s.XXXXXXX"); + fd = mkstemp(CS temp_fn); /* modifies temp_fn */ if (fd < 0) - return tls_error(string_open_failed(errno, "%s for writing", filename), - host, 0); + return tls_error(US"Unable to open temp file", strerror(errno), NULL); (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */ - ret = gnutls_rsa_params_export_raw(rsa_params, &m, &e, &d, &p, &q, &u, - &rsa_bits); - if (ret < 0) return tls_error(US"RSA params export", host, ret); + /* GnuTLS overshoots! + * If we ask for 2236, we might get 2237 or more. + * But there's no way to ask GnuTLS how many bits there really are. + * We can ask how many bits were used in a TLS session, but that's it! + * The prime itself is hidden behind too much abstraction. + * So we ask for less, and proceed on a wing and a prayer. + * First attempt, subtracted 3 for 2233 and got 2240. + */ + if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10) + { + dh_bits_gen = dh_bits - 10; + DEBUG(D_tls) + debug_printf("being paranoid about DH generation, make it '%d' bits'\n", + dh_bits_gen); + } + + DEBUG(D_tls) + debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n", + dh_bits_gen); + rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen); + exim_gnutls_err_check(US"gnutls_dh_params_generate2"); + + /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time, + and I confirmed that a NULL call to get the size first is how the GnuTLS + sample apps handle this. */ + + sz = 0; + m.data = NULL; + rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, + m.data, &sz); + if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) + exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing"); + m.size = sz; + m.data = malloc(m.size); + if (m.data == NULL) + return tls_error(US"memory allocation failed", strerror(errno), NULL); + /* this will return a size 1 less than the allocation size above */ + rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, + m.data, &sz); + if (rc != GNUTLS_E_SUCCESS) + { + free(m.data); + exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real"); + } + m.size = sz; /* shrink by 1, probably */ + + sz = write_to_fd_buf(fd, m.data, (size_t) m.size); + if (sz != m.size) + { + free(m.data); + return tls_error(US"TLS cache write D-H params failed", + strerror(errno), NULL); + } + free(m.data); + sz = write_to_fd_buf(fd, US"\n", 1); + if (sz != 1) + return tls_error(US"TLS cache write D-H params final newline failed", + strerror(errno), NULL); + + rc = close(fd); + if (rc) + return tls_error(US"TLS cache write close() failed", + strerror(errno), NULL); + + if (Urename(temp_fn, filename) < 0) + return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"", + temp_fn, filename), strerror(errno), NULL); + + DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename); + } + +DEBUG(D_tls) debug_printf("initialized server D-H parameters\n"); +return OK; +} + + + + +/************************************************* +* Variables re-expanded post-SNI * +*************************************************/ + +/* Called from both server and client code, via tls_init(), and also from +the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni". + +We can tell the two apart by state->received_sni being non-NULL in callback. + +The callback should not call us unless state->trigger_sni_changes is true, +which we are responsible for setting on the first pass through. + +Arguments: + state exim_gnutls_state_st * + +Returns: OK/DEFER/FAIL +*/ - ret = gnutls_dh_params_export_raw(dh_params, &prime, &generator, &dh_bits); - if (ret < 0) return tls_error(US"DH params export", host, ret); +static int +tls_expand_session_files(exim_gnutls_state_st *state) +{ +struct stat statbuf; +int rc; +const host_item *host = state->host; /* macro should be reconsidered? */ +uschar *saved_tls_certificate = NULL; +uschar *saved_tls_privatekey = NULL; +uschar *saved_tls_verify_certificates = NULL; +uschar *saved_tls_crl = NULL; +int cert_count; + +/* We check for tls_sni *before* expansion. */ +if (!host) /* server */ + { + if (!state->received_sni) + { + if (state->tls_certificate && + (Ustrstr(state->tls_certificate, US"tls_sni") || + Ustrstr(state->tls_certificate, US"tls_in_sni") || + Ustrstr(state->tls_certificate, US"tls_out_sni") + )) + { + DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n"); + state->trigger_sni_changes = TRUE; + } + } + else + { + /* useful for debugging */ + saved_tls_certificate = state->exp_tls_certificate; + saved_tls_privatekey = state->exp_tls_privatekey; + saved_tls_verify_certificates = state->exp_tls_verify_certificates; + saved_tls_crl = state->exp_tls_crl; + } + } - if (!write_datum(fd, &m) || - !write_datum(fd, &e) || - !write_datum(fd, &d) || - !write_datum(fd, &p) || - !write_datum(fd, &q) || - !write_datum(fd, &u) || - !write_datum(fd, &prime) || - !write_datum(fd, &generator)) - return tls_error(US"TLS cache write failed", host, 0); +rc = gnutls_certificate_allocate_credentials(&state->x509_cred); +exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); - (void)close(fd); +/* remember: expand_check_tlsvar() is expand_check() but fiddling with +state members, assuming consistent naming; and expand_check() returns +false if expansion failed, unless expansion was forced to fail. */ - if (rename(CS tempfilename, CS filename) < 0) - return tls_error(string_sprintf("failed to rename %s as %s: %s", - tempfilename, filename, strerror(errno)), host, 0); +/* check if we at least have a certificate, before doing expensive +D-H generation. */ - DEBUG(D_tls) debug_printf("wrote RSA and D-H parameters to file\n"); +if (!expand_check_tlsvar(tls_certificate)) + return DEFER; + +/* certificate is mandatory in server, optional in client */ + +if ((state->exp_tls_certificate == NULL) || + (*state->exp_tls_certificate == '\0')) + { + if (!host) + return tls_error(US"no TLS server certificate is specified", NULL, NULL); + else + DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n"); } -/* File opened for reading; get the data */ +if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey)) + return DEFER; + +/* tls_privatekey is optional, defaulting to same file as certificate */ + +if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0') + { + state->tls_privatekey = state->tls_certificate; + state->exp_tls_privatekey = state->exp_tls_certificate; + } + + +if (state->exp_tls_certificate && *state->exp_tls_certificate) + { + DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", + state->exp_tls_certificate, state->exp_tls_privatekey); + + if (state->received_sni) + { + if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) && + (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0)) + { + DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n"); + } + else + { + DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n"); + } + } + rc = gnutls_certificate_set_x509_key_file(state->x509_cred, + CS state->exp_tls_certificate, CS state->exp_tls_privatekey, + GNUTLS_X509_FMT_PEM); + exim_gnutls_err_check( + string_sprintf("cert/key setup: cert=%s key=%s", + state->exp_tls_certificate, state->exp_tls_privatekey)); + DEBUG(D_tls) debug_printf("TLS: cert/key registered\n"); + } /* tls_certificate */ + + +/* Set the OCSP stapling server info */ + +#ifdef EXPERIMENTAL_OCSP +if ( !host /* server */ + && tls_ocsp_file + ) + { + if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", + &state->exp_tls_ocsp_file)) + return DEFER; + + /* Use the full callback method for stapling just to get observability. + More efficient would be to read the file once only, if it never changed + (due to SNI). Would need restart on file update, or watch datestamp. */ + + gnutls_certificate_set_ocsp_status_request_function(state->x509_cred, + server_ocsp_stapling_cb, state->exp_tls_ocsp_file); + + DEBUG(D_tls) debug_printf("Set OCSP response file %s\n", &state->exp_tls_ocsp_file); + } +#endif + + +/* Set the trusted CAs file if one is provided, and then add the CRL if one is +provided. Experiment shows that, if the certificate file is empty, an unhelpful +error message is provided. However, if we just refrain from setting anything up +in that case, certificate verification fails, which seems to be the correct +behaviour. */ + +if (state->tls_verify_certificates && *state->tls_verify_certificates) + { + if (!expand_check_tlsvar(tls_verify_certificates)) + return DEFER; + if (state->tls_crl && *state->tls_crl) + if (!expand_check_tlsvar(tls_crl)) + return DEFER; + + if (!(state->exp_tls_verify_certificates && + *state->exp_tls_verify_certificates)) + { + DEBUG(D_tls) + debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n"); + /* With no tls_verify_certificates, we ignore tls_crl too */ + return OK; + } + } else { - if (!read_datum(fd, &m) || - !read_datum(fd, &e) || - !read_datum(fd, &d) || - !read_datum(fd, &p) || - !read_datum(fd, &q) || - !read_datum(fd, &u) || - !read_datum(fd, &prime) || - !read_datum(fd, &generator)) - return tls_error(US"TLS cache read failed", host, 0); + DEBUG(D_tls) + debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n"); + return OK; + } - (void)close(fd); +if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0) + { + log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " + "(tls_verify_certificates): %s", state->exp_tls_verify_certificates, + strerror(errno)); + return DEFER; + } - ret = gnutls_rsa_params_import_raw(rsa_params, &m, &e, &d, &p, &q, &u); - if (ret < 0) return tls_error(US"RSA params import", host, ret); +/* The test suite passes in /dev/null; we could check for that path explicitly, +but who knows if someone has some weird FIFO which always dumps some certs, or +other weirdness. The thing we really want to check is that it's not a +directory, since while OpenSSL supports that, GnuTLS does not. +So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */ +if (S_ISDIR(statbuf.st_mode)) + { + DEBUG(D_tls) + debug_printf("verify certificates path is a dir: \"%s\"\n", + state->exp_tls_verify_certificates); + log_write(0, LOG_MAIN|LOG_PANIC, + "tls_verify_certificates \"%s\" is a directory", + state->exp_tls_verify_certificates); + return DEFER; + } - ret = gnutls_dh_params_import_raw(dh_params, &prime, &generator); - if (ret < 0) return tls_error(US"DH params import", host, ret); +DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n", + state->exp_tls_verify_certificates, statbuf.st_size); - DEBUG(D_tls) debug_printf("read RSA and D-H parameters from file\n"); +if (statbuf.st_size == 0) + { + DEBUG(D_tls) + debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n"); + return OK; + } + +cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred, + CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM); +if (cert_count < 0) + { + rc = cert_count; + exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file"); + } +DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count); + +if (state->tls_crl && *state->tls_crl && + state->exp_tls_crl && *state->exp_tls_crl) + { + DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); + cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred, + CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); + if (cert_count < 0) + { + rc = cert_count; + exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file"); + } + DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count); } -DEBUG(D_tls) debug_printf("initialized RSA and D-H parameters\n"); return OK; } +/************************************************* +* Set X.509 state variables * +*************************************************/ + +/* In GnuTLS, the registered cert/key are not replaced by a later +set of a cert/key, so for SNI support we need a whole new x509_cred +structure. Which means various other non-re-expanded pieces of state +need to be re-set in the new struct, so the setting logic is pulled +out to this. + +Arguments: + state exim_gnutls_state_st * + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_set_remaining_x509(exim_gnutls_state_st *state) +{ +int rc; +const host_item *host = state->host; /* macro should be reconsidered? */ + +/* Create D-H parameters, or read them from the cache file. This function does +its own SMTP error messaging. This only happens for the server, TLS D-H ignores +client-side params. */ + +if (!state->host) + { + if (!dh_server_params) + { + rc = init_server_dh(); + if (rc != OK) return rc; + } + gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params); + } + +/* Link the credentials to the session. */ + +rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); +exim_gnutls_err_check(US"gnutls_credentials_set"); + +return OK; +} + /************************************************* * Initialize for GnuTLS * *************************************************/ @@ -411,344 +960,513 @@ Arguments: host connected host, if client; NULL if server certificate certificate file privatekey private key file + sni TLS SNI to send, sometimes when client; else NULL cas CA certs file crl CRL file + require_ciphers tls_require_ciphers setting + caller_state returned state-info structure Returns: OK/DEFER/FAIL */ static int -tls_init(host_item *host, uschar *certificate, uschar *privatekey, uschar *cas, - uschar *crl) +tls_init( + const host_item *host, + const uschar *certificate, + const uschar *privatekey, + const uschar *sni, + const uschar *cas, + const uschar *crl, + const uschar *require_ciphers, + exim_gnutls_state_st **caller_state) { +exim_gnutls_state_st *state; int rc; -uschar *cert_expanded, *key_expanded, *cas_expanded, *crl_expanded; +size_t sz; +const char *errpos; +uschar *p; +BOOL want_default_priorities; -initialized = (host == NULL)? INITIALIZED_SERVER : INITIALIZED_CLIENT; +if (!exim_gnutls_base_init_done) + { + DEBUG(D_tls) debug_printf("GnuTLS global init required.\n"); + +#ifdef HAVE_GNUTLS_PKCS11 + /* By default, gnutls_global_init will init PKCS11 support in auto mode, + which loads modules from a config file, which sounds good and may be wanted + by some sysadmin, but also means in common configurations that GNOME keyring + environment variables are used and so breaks for users calling mailq. + To prevent this, we init PKCS11 first, which is the documented approach. */ + if (!gnutls_allow_auto_pkcs11) + { + rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); + exim_gnutls_err_check(US"gnutls_pkcs11_init"); + } +#endif -rc = gnutls_global_init(); -if (rc < 0) return tls_error(US"tls-init", host, rc); + rc = gnutls_global_init(); + exim_gnutls_err_check(US"gnutls_global_init"); + +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 + DEBUG(D_tls) + { + gnutls_global_set_log_function(exim_gnutls_logger_cb); + /* arbitrarily chosen level; bump upto 9 for more */ + gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); + } +#endif -/* Create RSA and D-H parameters, or read them from the cache file. This -function does its own SMTP error messaging. */ + exim_gnutls_base_init_done = TRUE; + } -rc = init_rsa_dh(host); -if (rc != OK) return rc; +if (host) + { + state = &state_client; + memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); + state->tlsp = &tls_out; + DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n"); + rc = gnutls_init(&state->session, GNUTLS_CLIENT); + } +else + { + state = &state_server; + memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); + state->tlsp = &tls_in; + DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n"); + rc = gnutls_init(&state->session, GNUTLS_SERVER); + } +exim_gnutls_err_check(US"gnutls_init"); -/* Create the credentials structure */ +state->host = host; -rc = gnutls_certificate_allocate_credentials(&x509_cred); -if (rc < 0) return tls_error(US"certificate_allocate_credentials", host, rc); +state->tls_certificate = certificate; +state->tls_privatekey = privatekey; +state->tls_require_ciphers = require_ciphers; +state->tls_sni = sni; +state->tls_verify_certificates = cas; +state->tls_crl = crl; -/* This stuff must be done for each session, because different certificates -may be required for different sessions. */ +/* This handles the variables that might get re-expanded after TLS SNI; +that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */ -if (!expand_check(certificate, US"tls_certificate", &cert_expanded)) - return DEFER; +DEBUG(D_tls) + debug_printf("Expanding various TLS configuration options for session credentials.\n"); +rc = tls_expand_session_files(state); +if (rc != OK) return rc; -if (privatekey != NULL) - { - if (!expand_check(privatekey, US"tls_privatekey", &key_expanded)) - return DEFER; - } -else key_expanded = cert_expanded; +/* These are all other parts of the x509_cred handling, since SNI in GnuTLS +requires a new structure afterwards. */ -/* Set the certificate and private keys */ +rc = tls_set_remaining_x509(state); +if (rc != OK) return rc; -if (cert_expanded != NULL) +/* set SNI in client, only */ +if (host) { - DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", - cert_expanded, key_expanded); - rc = gnutls_certificate_set_x509_key_file(x509_cred, CS cert_expanded, - CS key_expanded, GNUTLS_X509_FMT_PEM); - if (rc < 0) + if (!expand_check(state->tlsp->sni, US"tls_out_sni", &state->exp_tls_sni)) + return DEFER; + if (state->exp_tls_sni && *state->exp_tls_sni) { - uschar *msg = string_sprintf("cert/key setup: cert=%s key=%s", - cert_expanded, key_expanded); - return tls_error(msg, host, rc); - } + DEBUG(D_tls) + debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni); + sz = Ustrlen(state->exp_tls_sni); + rc = gnutls_server_name_set(state->session, + GNUTLS_NAME_DNS, state->exp_tls_sni, sz); + exim_gnutls_err_check(US"gnutls_server_name_set"); + } } +else if (state->tls_sni) + DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \ + "have an SNI set for a client [%s]\n", state->tls_sni); -/* A certificate is mandatory in a server, but not in a client */ +/* This is the priority string support, +http://www.gnutls.org/manual/html_node/Priority-Strings.html +and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols. +This was backwards incompatible, but means Exim no longer needs to track +all algorithms and provide string forms for them. */ -else - { - if (host == NULL) - return tls_error(US"no TLS server certificate is specified", host, 0); - DEBUG(D_tls) debug_printf("no TLS client certificate is specified\n"); - } - -/* Set the trusted CAs file if one is provided, and then add the CRL if one is -provided. Experiment shows that, if the certificate file is empty, an unhelpful -error message is provided. However, if we just refrain from setting anything up -in that case, certificate verification fails, which seems to be the correct -behaviour. */ +want_default_priorities = TRUE; -if (cas != NULL) +if (state->tls_require_ciphers && *state->tls_require_ciphers) { - struct stat statbuf; - - if (!expand_check(cas, US"tls_verify_certificates", &cas_expanded)) + if (!expand_check_tlsvar(tls_require_ciphers)) return DEFER; - - if (stat(CS cas_expanded, &statbuf) < 0) + if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers) { - log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " - "(tls_verify_certificates): %s", cas_expanded, strerror(errno)); - return DEFER; + DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", + state->exp_tls_require_ciphers); + + rc = gnutls_priority_init(&state->priority_cache, + CS state->exp_tls_require_ciphers, &errpos); + want_default_priorities = FALSE; + p = state->exp_tls_require_ciphers; } + } +if (want_default_priorities) + { + DEBUG(D_tls) + debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", + exim_default_gnutls_priority); + rc = gnutls_priority_init(&state->priority_cache, + exim_default_gnutls_priority, &errpos); + p = US exim_default_gnutls_priority; + } - DEBUG(D_tls) debug_printf("verify certificates = %s size=%d\n", - cas_expanded, (int)statbuf.st_size); +exim_gnutls_err_check(string_sprintf( + "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"", + p, errpos - CS p, errpos)); - /* If the cert file is empty, there's no point in loading the CRL file. */ +rc = gnutls_priority_set(state->session, state->priority_cache); +exim_gnutls_err_check(US"gnutls_priority_set"); - if (statbuf.st_size > 0) - { - rc = gnutls_certificate_set_x509_trust_file(x509_cred, CS cas_expanded, - GNUTLS_X509_FMT_PEM); - if (rc < 0) return tls_error(US"setup_certs", host, rc); +gnutls_db_set_cache_expiration(state->session, ssl_session_timeout); - if (crl != NULL && *crl != 0) - { - if (!expand_check(crl, US"tls_crl", &crl_expanded)) - return DEFER; - DEBUG(D_tls) debug_printf("loading CRL file = %s\n", crl_expanded); - rc = gnutls_certificate_set_x509_crl_file(x509_cred, CS crl_expanded, - GNUTLS_X509_FMT_PEM); - if (rc < 0) return tls_error(US"CRL setup", host, rc); - } - } +/* Reduce security in favour of increased compatibility, if the admin +decides to make that trade-off. */ +if (gnutls_compat_mode) + { +#if LIBGNUTLS_VERSION_NUMBER >= 0x020104 + DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n"); + gnutls_session_enable_compatibility_mode(state->session); +#else + DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n"); +#endif } -/* Associate the parameters with the x509 credentials structure. */ - -gnutls_certificate_set_dh_params(x509_cred, dh_params); -gnutls_certificate_set_rsa_params(x509_cred, rsa_params); - -DEBUG(D_tls) debug_printf("initialized certificate stuff\n"); +*caller_state = state; return OK; } - /************************************************* -* Remove ciphers from priority list * +* Extract peer information * *************************************************/ -/* Cautiously written so that it will remove duplicates if present. +/* Called from both server and client code. +Only this is allowed to set state->peerdn and state->have_set_peerdn +and we use that to detect double-calls. + +NOTE: the state blocks last while the TLS connection is up, which is fine +for logging in the server side, but for the client side, we log after teardown +in src/deliver.c. While the session is up, we can twist about states and +repoint tls_* globals, but those variables used for logging or other variable +expansion that happens _after_ delivery need to have a longer life-time. + +So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from +doing this more than once per generation of a state context. We set them in +the state context, and repoint tls_* to them. After the state goes away, the +tls_* copies of the pointers remain valid and client delivery logging is happy. + +tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues +don't apply. Arguments: - list a zero-terminated list - remove_list a zero-terminated list to be removed + state exim_gnutls_state_st * -Returns: nothing +Returns: OK/DEFER/FAIL */ -static void -remove_ciphers(int *list, int *remove_list) +static int +peer_status(exim_gnutls_state_st *state) { -for (; *remove_list != 0; remove_list++) +uschar cipherbuf[256]; +const gnutls_datum *cert_list; +int old_pool, rc; +unsigned int cert_list_size = 0; +gnutls_protocol_t protocol; +gnutls_cipher_algorithm_t cipher; +gnutls_kx_algorithm_t kx; +gnutls_mac_algorithm_t mac; +gnutls_certificate_type_t ct; +gnutls_x509_crt_t crt; +uschar *p, *dn_buf; +size_t sz; + +if (state->have_set_peerdn) + return OK; +state->have_set_peerdn = TRUE; + +state->peerdn = NULL; + +/* tls_cipher */ +cipher = gnutls_cipher_get(state->session); +protocol = gnutls_protocol_get_version(state->session); +mac = gnutls_mac_get(state->session); +kx = gnutls_kx_get(state->session); + +string_format(cipherbuf, sizeof(cipherbuf), + "%s:%s:%d", + gnutls_protocol_get_name(protocol), + gnutls_cipher_suite_get_name(kx, cipher, mac), + (int) gnutls_cipher_get_key_size(cipher) * 8); + +/* I don't see a way that spaces could occur, in the current GnuTLS +code base, but it was a concern in the old code and perhaps older GnuTLS +releases did return "TLS 1.0"; play it safe, just in case. */ +for (p = cipherbuf; *p != '\0'; ++p) + if (isspace(*p)) + *p = '-'; +old_pool = store_pool; +store_pool = POOL_PERM; +state->ciphersuite = string_copy(cipherbuf); +store_pool = old_pool; +state->tlsp->cipher = state->ciphersuite; + +/* tls_peerdn */ +cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size); + +if (cert_list == NULL || cert_list_size == 0) { - int *p = list; - while (*p != 0) - { - if (*p == *remove_list) - { - int *pp = p; - do { pp[0] = pp[1]; pp++; } while (*pp != 0); - } - else p++; - } + DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n", + cert_list, cert_list_size); + if (state->verify_requirement == VERIFY_REQUIRED) + return tls_error(US"certificate verification failed", + "no certificate received from peer", state->host); + return OK; + } + +ct = gnutls_certificate_type_get(state->session); +if (ct != GNUTLS_CRT_X509) + { + const char *ctn = gnutls_certificate_type_get_name(ct); + DEBUG(D_tls) + debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn); + if (state->verify_requirement == VERIFY_REQUIRED) + return tls_error(US"certificate verification not possible, unhandled type", + ctn, state->host); + return OK; + } + +#define exim_gnutls_peer_err(Label) do { \ + if (rc != GNUTLS_E_SUCCESS) { \ + DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \ + if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \ + return OK; } } while (0) + +rc = import_cert(&cert_list[0], &crt); +exim_gnutls_peer_err(US"cert 0"); + +state->tlsp->peercert = state->peercert = crt; + +sz = 0; +rc = gnutls_x509_crt_get_dn(crt, NULL, &sz); +if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) + { + exim_gnutls_peer_err(US"getting size for cert DN failed"); + return FAIL; /* should not happen */ } +dn_buf = store_get_perm(sz); +rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz); +exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]"); + +state->peerdn = dn_buf; + +return OK; +#undef exim_gnutls_peer_err } + /************************************************* -* Add ciphers to priority list * +* Verify peer certificate * *************************************************/ -/* Cautiously written to check the list size +/* Called from both server and client code. +*Should* be using a callback registered with +gnutls_certificate_set_verify_function() to fail the handshake if we dislike +the peer information, but that's too new for some OSes. Arguments: - list a zero-terminated list - list_max maximum offset in the list - add_list a zero-terminated list to be added + state exim_gnutls_state_st * + error where to put an error message -Returns: TRUE if OK; FALSE if list overflows +Returns: + FALSE if the session should be rejected + TRUE if the cert is okay or we just don't care */ static BOOL -add_ciphers(int *list, int list_max, int *add_list) +verify_certificate(exim_gnutls_state_st *state, const char **error) { -int next = 0; -while (list[next] != 0) next++; -while (*add_list != 0) +int rc; +unsigned int verify; + +*error = NULL; + +if ((rc = peer_status(state)) != OK) { - if (next >= list_max) return FALSE; - list[next++] = *add_list++; + verify = GNUTLS_CERT_INVALID; + *error = "certificate not supplied"; } -list[next] = 0; -return TRUE; -} - +else + rc = gnutls_certificate_verify_peers2(state->session, &verify); +/* Handle the result of verification. INVALID seems to be set as well +as REVOKED, but leave the test for both. */ -/************************************************* -* Initialize a single GNUTLS session * -*************************************************/ +if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) + { + state->peer_cert_verified = FALSE; + if (!*error) + *error = verify & GNUTLS_CERT_REVOKED + ? "certificate revoked" : "certificate invalid"; -/* Set the algorithm, the db backend, whether to request certificates etc. + DEBUG(D_tls) + debug_printf("TLS certificate verification failed (%s): peerdn=%s\n", + *error, state->peerdn ? state->peerdn : US""); -TLS in Exim was first implemented using OpenSSL. This has a function to which -you pass a list of cipher suites that are permitted/not permitted. GnuTLS works -differently. It operates using priority lists for the different components of -cipher suites. + if (state->verify_requirement == VERIFY_REQUIRED) + { + gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); + return FALSE; + } + DEBUG(D_tls) + debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n"); + } +else + { + state->peer_cert_verified = TRUE; + DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n", + state->peerdn ? state->peerdn : US""); + } -For compatibility of configuration, we scan a list of cipher suites and set -priorities therefrom. However, at the moment, we pay attention only to the bulk -cipher. +state->tlsp->peerdn = state->peerdn; -Arguments: - side one of GNUTLS_SERVER, GNUTLS_CLIENT - expciphers expanded ciphers list +return TRUE; +} -Returns: a gnutls_session, or NULL if there is a problem -*/ -static gnutls_session -tls_session_init(int side, uschar *expciphers) -{ -gnutls_session session; -gnutls_init(&session, side); -/* Handle the list of permitted ciphers */ +/* ------------------------------------------------------------------------ */ +/* Callbacks */ -memcpy(cipher_priority, default_cipher_priority, sizeof(cipher_priority)); +/* Logging function which can be registered with + * gnutls_global_set_log_function() + * gnutls_global_set_log_level() 0..9 + */ +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +static void +exim_gnutls_logger_cb(int level, const char *message) +{ + size_t len = strlen(message); + if (len < 1) + { + DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); + return; + } + DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, + message[len-1] == '\n' ? "" : "\n"); +} +#endif -if (expciphers != NULL) - { - int sep = 0; - BOOL first = TRUE; - uschar *cipher; - /* The names OpenSSL uses are of the form DES-CBC3-SHA, using hyphen - separators. GnuTLS uses underscore separators. So that I can use either form - in my tests, and also for general convenience, we turn hyphens into - underscores before scanning the list. */ +/* Called after client hello, should handle SNI work. +This will always set tls_sni (state->received_sni) if available, +and may trigger presenting different certificates, +if state->trigger_sni_changes is TRUE. - uschar *s = expciphers; - while (*s != 0) { if (*s == '-') *s = '_'; s++; } +Should be registered with + gnutls_handshake_set_post_client_hello_function() - while ((cipher = string_nextinlist(&expciphers, &sep, big_buffer, - big_buffer_size)) != NULL) - { - int i; - BOOL exclude = cipher[0] == '!'; - if (first && !exclude) cipher_priority[0] = 0; - first = FALSE; +"This callback must return 0 on success or a gnutls error code to terminate the +handshake.". - for (i = 0; i < sizeof(cipher_index)/sizeof(pri_item); i++) - { - uschar *ss = strstric(cipher, cipher_index[i].name, FALSE); - if (ss != NULL) - { - uschar *endss = ss + Ustrlen(cipher_index[i].name); - if ((ss == cipher || !isalnum(ss[-1])) && !isalnum(*endss)) - { - if (exclude) - remove_ciphers(cipher_priority, cipher_index[i].values); - else - { - if (!add_ciphers(cipher_priority, - sizeof(cipher_priority)/sizeof(pri_item), - cipher_index[i].values)) - { - log_write(0, LOG_MAIN|LOG_PANIC, "GnuTLS init failed: cipher " - "priority table overflow"); - gnutls_deinit(session); - return NULL; - } - } - } - } - } - } +For inability to get SNI information, we return 0. +We only return non-zero if re-setup failed. +Only used for server-side TLS. +*/ - DEBUG(D_tls) - { - int *ptr = cipher_priority; - debug_printf("adjusted cipher priorities:"); - while (*ptr != 0) debug_printf(" %d", *ptr++); - debug_printf("\n"); - } +static int +exim_sni_handling_cb(gnutls_session_t session) +{ +char sni_name[MAX_HOST_LEN]; +size_t data_len = MAX_HOST_LEN; +exim_gnutls_state_st *state = &state_server; +unsigned int sni_type; +int rc, old_pool; + +rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0); +if (rc != GNUTLS_E_SUCCESS) + { + DEBUG(D_tls) { + if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) + debug_printf("TLS: no SNI presented in handshake.\n"); + else + debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n", + gnutls_strerror(rc), rc); + }; + return 0; } -/* Define the various priorities */ +if (sni_type != GNUTLS_NAME_DNS) + { + DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type); + return 0; + } -gnutls_cipher_set_priority(session, cipher_priority); -gnutls_compression_set_priority(session, comp_priority); -gnutls_kx_set_priority(session, kx_priority); -gnutls_protocol_set_priority(session, protocol_priority); -gnutls_mac_set_priority(session, mac_priority); +/* We now have a UTF-8 string in sni_name */ +old_pool = store_pool; +store_pool = POOL_PERM; +state->received_sni = string_copyn(US sni_name, data_len); +store_pool = old_pool; -gnutls_cred_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred); +/* We set this one now so that variable expansions below will work */ +state->tlsp->sni = state->received_sni; -gnutls_dh_set_prime_bits(session, DH_BITS); +DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name, + state->trigger_sni_changes ? "" : " (unused for certificate selection)"); -/* Request or demand a certificate of the peer, as configured. This will -happen only in a server. */ +if (!state->trigger_sni_changes) + return 0; -if (verify_requirement != VERIFY_NONE) - gnutls_certificate_server_set_request(session, - (verify_requirement == VERIFY_OPTIONAL)? - GNUTLS_CERT_REQUEST : GNUTLS_CERT_REQUIRE); +rc = tls_expand_session_files(state); +if (rc != OK) + { + /* If the setup of certs/etc failed before handshake, TLS would not have + been offered. The best we can do now is abort. */ + return GNUTLS_E_APPLICATION_ERROR_MIN; + } -gnutls_db_set_cache_expiration(session, ssl_session_timeout); +rc = tls_set_remaining_x509(state); +if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; -DEBUG(D_tls) debug_printf("initialized GnuTLS session\n"); -return session; +return 0; } -/************************************************* -* Get name of cipher in use * -*************************************************/ +#ifdef EXPERIMENTAL_OCSP -/* The answer is left in a static buffer, and tls_cipher is set to point -to it. +static int +server_ocsp_stapling_cb(gnutls_session_t session, void * ptr, + gnutls_datum_t * ocsp_response) +{ +int ret; -Argument: pointer to a GnuTLS session -Returns: nothing -*/ +tls_in.ocsp = OCSP_NOT_RESP; +if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0) + { + DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n", + (char *)ptr); + return GNUTLS_E_NO_CERTIFICATE_STATUS; + } -static void -construct_cipher_name(gnutls_session session) -{ -static uschar cipherbuf[256]; -uschar *ver; -int bits, c, kx, mac; +tls_in.ocsp = OCSP_NOT_VFY; +return 0; +} -ver = string_copy( - US gnutls_protocol_get_name(gnutls_protocol_get_version(session))); -if (Ustrncmp(ver, "TLS ", 4) == 0) ver[3] = '-'; /* Don't want space */ +#endif -c = gnutls_cipher_get(session); -bits = gnutls_cipher_get_key_size(c); -mac = gnutls_mac_get(session); -kx = gnutls_kx_get(session); -string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, - gnutls_cipher_suite_get_name(kx, c, mac), bits); -tls_cipher = cipherbuf; -DEBUG(D_tls) debug_printf("cipher: %s\n", cipherbuf); -} + +/* ------------------------------------------------------------------------ */ +/* Exported functions */ + @@ -761,7 +1479,7 @@ the STARTTLS command. It must respond to that command, and then negotiate a TLS session. Arguments: - require_ciphers list of allowed ciphers + require_ciphers list of allowed ciphers or NULL Returns: OK on success DEFER for errors before the start of the negotiation @@ -770,19 +1488,16 @@ Returns: OK on success */ int -tls_server_start(uschar *require_ciphers) +tls_server_start(const uschar *require_ciphers) { int rc; -uschar *error; -uschar *expciphers = NULL; +const char *error; +exim_gnutls_state_st *state = NULL; /* Check for previous activation */ - -if (tls_active >= 0) +if (tls_in.active >= 0) { - log_write(0, LOG_MAIN, "STARTTLS received in already encrypted " - "connection from %s", - (sender_fullhost != NULL)? sender_fullhost : US"local process"); + tls_error(US"STARTTLS received after TLS started", "", NULL); smtp_printf("554 Already in TLS\r\n"); return FAIL; } @@ -790,31 +1505,40 @@ if (tls_active >= 0) /* Initialize the library. If it fails, it will already have logged the error and sent an SMTP response. */ -DEBUG(D_tls) debug_printf("initializing GnuTLS as a server\n"); +DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n"); -rc = tls_init(NULL, tls_certificate, tls_privatekey, tls_verify_certificates, - tls_crl); +rc = tls_init(NULL, tls_certificate, tls_privatekey, + NULL, tls_verify_certificates, tls_crl, + require_ciphers, &state); if (rc != OK) return rc; -if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) - return FAIL; - /* If this is a host for which certificate verification is mandatory or optional, set up appropriately. */ -tls_certificate_verified = FALSE; -verify_requirement = VERIFY_NONE; - if (verify_check_host(&tls_verify_hosts) == OK) - verify_requirement = VERIFY_REQUIRED; + { + DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n"); + state->verify_requirement = VERIFY_REQUIRED; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); + } else if (verify_check_host(&tls_try_verify_hosts) == OK) - verify_requirement = VERIFY_OPTIONAL; + { + DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n"); + state->verify_requirement = VERIFY_OPTIONAL; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); + } +else + { + DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n"); + state->verify_requirement = VERIFY_NONE; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); + } -/* Prepare for new connection */ +/* Register SNI handling; always, even if not in tls_certificate, so that the +expansion variable $tls_sni is always available. */ -tls_session = tls_session_init(GNUTLS_SERVER, expciphers); -if (tls_session == NULL) - return tls_error(US"tls_session_init", NULL, GNUTLS_E_MEMORY_ERROR); +gnutls_handshake_set_post_client_hello_function(state->session, + exim_sni_handling_cb); /* 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 @@ -822,7 +1546,7 @@ 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. */ -if (!tls_on_connect) +if (!state->tlsp->on_connect) { smtp_printf("220 TLS go ahead\r\n"); fflush(smtp_out); @@ -831,32 +1555,33 @@ if (!tls_on_connect) /* Now negotiate the TLS session. We put our own timer on it, since it seems that the GnuTLS library doesn't. */ -gnutls_transport_set_ptr(tls_session, (gnutls_transport_ptr)fileno(smtp_out)); +gnutls_transport_set_ptr2(state->session, + (gnutls_transport_ptr)(long) fileno(smtp_in), + (gnutls_transport_ptr)(long) fileno(smtp_out)); +state->fd_in = fileno(smtp_in); +state->fd_out = fileno(smtp_out); sigalrm_seen = FALSE; if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); -rc = gnutls_handshake(tls_session); +do + { + rc = gnutls_handshake(state->session); + } while ((rc == GNUTLS_E_AGAIN) || + (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen)); alarm(0); -if (rc < 0) +if (rc != GNUTLS_E_SUCCESS) { - if (sigalrm_seen) - Ustrcpy(ssl_errstring, "timed out"); - else - Ustrcpy(ssl_errstring, gnutls_strerror(rc)); - log_write(0, LOG_MAIN, - "TLS error on connection from %s (gnutls_handshake): %s", - (sender_fullhost != NULL)? sender_fullhost : US"local process", - ssl_errstring); - + tls_error(US"gnutls_handshake", + sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL); /* It seems that, except in the case of a timeout, we have to close the connection right here; otherwise if the other end is running OpenSSL it hangs until the server times out. */ if (!sigalrm_seen) { - fclose(smtp_out); - fclose(smtp_in); + (void)fclose(smtp_out); + (void)fclose(smtp_in); } return FAIL; @@ -864,30 +1589,40 @@ if (rc < 0) DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); -if (verify_requirement != VERIFY_NONE && - !verify_certificate(tls_session, &error)) +/* Verify after the fact */ + +if ( state->verify_requirement != VERIFY_NONE + && !verify_certificate(state, &error)) { - log_write(0, LOG_MAIN, - "TLS error on connection from %s: certificate verification failed (%s)", - (sender_fullhost != NULL)? sender_fullhost : US"local process", error); - return FAIL; + if (state->verify_requirement != VERIFY_OPTIONAL) + { + tls_error(US"certificate verification failed", error, NULL); + return FAIL; + } + DEBUG(D_tls) + debug_printf("TLS: continuing on only because verification was optional, after: %s\n", + error); } -construct_cipher_name(tls_session); +/* Figure out peer DN, and if authenticated, etc. */ + +rc = peer_status(state); +if (rc != OK) return rc; + +/* Sets various Exim expansion variables; always safe within server */ + +extract_exim_vars_from_tls_state(state); /* TLS has been set up. Adjust the input functions to read via TLS, and initialize appropriately. */ -ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); -ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; -ssl_xfer_eof = ssl_xfer_error = 0; +state->xfer_buffer = store_malloc(ssl_xfer_buffer_size); receive_getc = tls_getc; receive_ungetc = tls_ungetc; receive_feof = tls_feof; receive_ferror = tls_ferror; - -tls_active = fileno(smtp_out); +receive_smtp_buffered = tls_smtp_buffered; return OK; } @@ -904,142 +1639,216 @@ return OK; Arguments: fd the fd of the connection host connected host (for messages) - addr - dhparam DH parameter file - certificate certificate file - privatekey private key file - verify_certs file for certificate verify - verify_crl CRL for verify - require_ciphers list of allowed ciphers - timeout startup timeout + addr the first address (not used) + ob smtp transport options Returns: OK/DEFER/FAIL (because using common functions), but for a client, DEFER and FAIL have the same meaning */ int -tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, - uschar *certificate, uschar *privatekey, uschar *verify_certs, - uschar *verify_crl, uschar *require_ciphers, int timeout) +tls_client_start(int fd, host_item *host, + address_item *addr ARG_UNUSED, + void *v_ob) { -const gnutls_datum *server_certs; -uschar *expciphers = NULL; -uschar *error; -unsigned int server_certs_size; +smtp_transport_options_block *ob = v_ob; int rc; +const char *error; +exim_gnutls_state_st *state = NULL; +#ifdef EXPERIMENTAL_OCSP +BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp, + NULL, host->name, host->address, NULL) == OK; +BOOL request_ocsp = require_ocsp ? TRUE + : verify_check_this_host(&ob->hosts_request_ocsp, + NULL, host->name, host->address, NULL) == OK; +#endif + +DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd); + +if ((rc = tls_init(host, ob->tls_certificate, ob->tls_privatekey, + ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl, + ob->tls_require_ciphers, &state)) != OK) + return rc; -DEBUG(D_tls) debug_printf("initializing GnuTLS as a client\n"); + { + int dh_min_bits = ob->tls_dh_min_bits; + if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS) + { + DEBUG(D_tls) + debug_printf("WARNING: tls_dh_min_bits far too low," + " clamping %d up to %d\n", + dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS); + dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS; + } -client_host = host; -verify_requirement = (verify_certs == NULL)? VERIFY_NONE : VERIFY_REQUIRED; -rc = tls_init(host, certificate, privatekey, verify_certs, verify_crl); -if (rc != OK) return rc; + DEBUG(D_tls) debug_printf("Setting D-H prime minimum" + " acceptable bits to %d\n", + dh_min_bits); + gnutls_dh_set_prime_bits(state->session, dh_min_bits); + } -if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) - return FAIL; +/* Stick to the old behaviour for compatibility if tls_verify_certificates is +set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only +the specified host patterns if one of them is defined */ + +if (( state->exp_tls_verify_certificates + && !ob->tls_verify_hosts + && !ob->tls_try_verify_hosts + ) + || + verify_check_host(&ob->tls_verify_hosts) == OK + ) + { + DEBUG(D_tls) debug_printf("TLS: server certificate verification required.\n"); + state->verify_requirement = VERIFY_REQUIRED; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); + } +else if (verify_check_host(&ob->tls_try_verify_hosts) == OK) + { + DEBUG(D_tls) debug_printf("TLS: server certificate verification optional.\n"); + state->verify_requirement = VERIFY_OPTIONAL; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); + } +else + { + DEBUG(D_tls) debug_printf("TLS: server certificate verification not required.\n"); + state->verify_requirement = VERIFY_NONE; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); + } -tls_session = tls_session_init(GNUTLS_CLIENT, expciphers); -if (tls_session == NULL) - return tls_error(US "tls_session_init", host, GNUTLS_E_MEMORY_ERROR); +#ifdef EXPERIMENTAL_OCSP /* since GnuTLS 3.1.3 */ +if (request_ocsp) + { + DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n"); + if ((rc = gnutls_ocsp_status_request_enable_client(state->session, + NULL, 0, NULL)) != OK) + return tls_error(US"cert-status-req", + gnutls_strerror(rc), state->host); + tls_out.ocsp = OCSP_NOT_RESP; + } +#endif -gnutls_transport_set_ptr(tls_session, (gnutls_transport_ptr)fd); +gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)(long) fd); +state->fd_in = fd; +state->fd_out = fd; +DEBUG(D_tls) debug_printf("about to gnutls_handshake\n"); /* There doesn't seem to be a built-in timeout on connection. */ sigalrm_seen = FALSE; -alarm(timeout); -rc = gnutls_handshake(tls_session); +alarm(ob->command_timeout); +do + { + rc = gnutls_handshake(state->session); + } while ((rc == GNUTLS_E_AGAIN) || + (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen)); alarm(0); -if (rc < 0) - { - if (sigalrm_seen) - { - log_write(0, LOG_MAIN, "TLS error on connection to %s [%s]: " - "gnutls_handshake timed out", host->name, host->address); - return FAIL; - } - else return tls_error(US "gnutls_handshake", host, rc); - } +if (rc != GNUTLS_E_SUCCESS) + return tls_error(US"gnutls_handshake", + sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host); -server_certs = gnutls_certificate_get_peers(tls_session, &server_certs_size); +DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); -if (server_certs != NULL) - { - uschar buff[1024]; - gnutls_x509_crt gcert; +/* Verify late */ - gnutls_x509_crt_init(&gcert); - tls_peerdn = US"unknown"; +if (state->verify_requirement != VERIFY_NONE && + !verify_certificate(state, &error)) + return tls_error(US"certificate verification failed", error, state->host); - if (gnutls_x509_crt_import(gcert, server_certs, GNUTLS_X509_FMT_DER) == 0) +#ifdef EXPERIMENTAL_OCSP +if (require_ocsp) + { + DEBUG(D_tls) { - size_t bufsize = sizeof(buff); - if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0) - tls_peerdn = string_copy_malloc(buff); + gnutls_datum_t stapling; + gnutls_ocsp_resp_t resp; + gnutls_datum_t printed; + if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0 + && (rc= gnutls_ocsp_resp_init(&resp)) == 0 + && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0 + && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0 + ) + { + debug_printf("%.4096s", printed.data); + gnutls_free(printed.data); + } + else + (void) tls_error(US"ocsp decode", gnutls_strerror(rc), state->host); } + + if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0) + return tls_error(US"certificate status check failed", NULL, state->host); + DEBUG(D_tls) debug_printf("Passed OCSP checking\n"); + tls_out.ocsp = OCSP_VFIED; } +#endif -/* Should we also verify the hostname here? */ +/* Figure out peer DN, and if authenticated, etc. */ -if (verify_requirement != VERIFY_NONE && - !verify_certificate(tls_session, &error)) - { - log_write(0, LOG_MAIN, - "TLS error on connection to %s [%s]: certificate verification failed (%s)", - host->name, host->address, error); - return FAIL; - } +if ((rc = peer_status(state)) != OK) + return rc; + +/* Sets various Exim expansion variables; may need to adjust for ACL callouts */ + +extract_exim_vars_from_tls_state(state); -construct_cipher_name(tls_session); /* Sets tls_cipher */ -tls_active = fd; return OK; } + /************************************************* -* Deal with logging errors during I/O * +* Close down a TLS session * *************************************************/ -/* We have to get the identity of the peer from saved data. - -Argument: - ec the GnuTLS error code, or 0 if it's a local error - when text identifying read or write - text local error text when ec is 0 +/* 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 TLS session in the parent process). -Returns: nothing +Arguments: TRUE if gnutls_bye is to be called +Returns: nothing */ -static void -record_io_error(int ec, uschar *when, uschar *text) +void +tls_close(BOOL is_server, BOOL shutdown) { -uschar *additional = US""; +exim_gnutls_state_st *state = is_server ? &state_server : &state_client; + +if (!state->tlsp || state->tlsp->active < 0) return; /* TLS was not active */ + +if (shutdown) + { + DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n"); + gnutls_bye(state->session, GNUTLS_SHUT_WR); + } -if (ec == GNUTLS_E_FATAL_ALERT_RECEIVED) - additional = string_sprintf(": %s", - gnutls_alert_get_name(gnutls_alert_get(tls_session))); +gnutls_deinit(state->session); -if (initialized == INITIALIZED_SERVER) - log_write(0, LOG_MAIN, "TLS %s error on connection from %s: %s%s", when, - (sender_fullhost != NULL)? sender_fullhost : US "local process", - (ec == 0)? text : US gnutls_strerror(ec), additional); +state->tlsp->active = -1; +memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); + +if ((state_server.session == NULL) && (state_client.session == NULL)) + { + gnutls_global_deinit(); + exim_gnutls_base_init_done = FALSE; + } -else - log_write(0, LOG_MAIN, "TLS %s error on connection to %s [%s]: %s%s", when, - client_host->name, client_host->address, - (ec == 0)? text : US gnutls_strerror(ec), additional); } + /************************************************* * 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 GnuTLS reading function. +Only used by the server-side TLS. + +This feeds DKIM and should be used for all message-body reads. Arguments: none Returns: the next character or EOF @@ -1048,15 +1857,16 @@ Returns: the next character or EOF int tls_getc(void) { -if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) +exim_gnutls_state_st *state = &state_server; +if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm) { - int inbytes; + ssize_t inbytes; - DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n", - (long) tls_session, (long) ssl_xfer_buffer, ssl_xfer_buffer_size); + DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n", + state->session, state->xfer_buffer, ssl_xfer_buffer_size); if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); - inbytes = gnutls_record_recv(tls_session, CS ssl_xfer_buffer, + inbytes = gnutls_record_recv(state->session, state->xfer_buffer, ssl_xfer_buffer_size); alarm(0); @@ -1072,12 +1882,17 @@ if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) receive_ungetc = smtp_ungetc; receive_feof = smtp_feof; receive_ferror = smtp_ferror; - - gnutls_deinit(tls_session); - tls_session = NULL; - tls_active = -1; - tls_cipher = NULL; - tls_peerdn = NULL; + receive_smtp_buffered = smtp_buffered; + + gnutls_deinit(state->session); + state->session = NULL; + state->tlsp->active = -1; + state->tlsp->bits = 0; + state->tlsp->certificate_verified = FALSE; + tls_channelbinding_b64 = NULL; + state->tlsp->cipher = NULL; + state->tlsp->peercert = NULL; + state->tlsp->peerdn = NULL; return smtp_getc(); } @@ -1086,28 +1901,32 @@ if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) else if (inbytes < 0) { - record_io_error(inbytes, US"recv", NULL); - ssl_xfer_error = 1; + record_io_error(state, (int) inbytes, US"recv", NULL); + state->xfer_error = 1; return EOF; } - - ssl_xfer_buffer_hwm = inbytes; - ssl_xfer_buffer_lwm = 0; +#ifndef DISABLE_DKIM + dkim_exim_verify_feed(state->xfer_buffer, inbytes); +#endif + state->xfer_buffer_hwm = (int) inbytes; + state->xfer_buffer_lwm = 0; } - /* Something in the buffer; return next uschar */ -return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; +return state->xfer_buffer[state->xfer_buffer_lwm++]; } + /************************************************* * Read bytes from TLS channel * *************************************************/ -/* +/* This does not feed DKIM, so if the caller uses this for reading message body, +then the caller must feed DKIM. + Arguments: buff buffer of data len size of buffer @@ -1117,32 +1936,45 @@ Returns: the number of bytes read */ int -tls_read(uschar *buff, size_t len) +tls_read(BOOL is_server, uschar *buff, size_t len) { -int inbytes; +exim_gnutls_state_st *state = is_server ? &state_server : &state_client; +ssize_t inbytes; + +if (len > INT_MAX) + len = INT_MAX; -DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n", - (long) tls_session, (long) buff, len); +if (state->xfer_buffer_lwm < state->xfer_buffer_hwm) + DEBUG(D_tls) + debug_printf("*** PROBABLY A BUG *** " \ + "tls_read() called with data in the tls_getc() buffer, %d ignored\n", + state->xfer_buffer_hwm - state->xfer_buffer_lwm); + +DEBUG(D_tls) + debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n", + state->session, buff, len); -inbytes = gnutls_record_recv(tls_session, CS buff, len); +inbytes = gnutls_record_recv(state->session, buff, len); if (inbytes > 0) return inbytes; if (inbytes == 0) { DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); } -else record_io_error(inbytes, US"recv", NULL); +else record_io_error(state, (int)inbytes, US"recv", NULL); return -1; } + /************************************************* * Write bytes down TLS channel * *************************************************/ /* Arguments: + is_server channel specifier buff buffer of data len number of bytes @@ -1151,27 +1983,28 @@ Returns: the number of bytes after a successful write, */ int -tls_write(const uschar *buff, size_t len) +tls_write(BOOL is_server, const uschar *buff, size_t len) { -int outbytes; -int left = len; +ssize_t outbytes; +size_t left = len; +exim_gnutls_state_st *state = is_server ? &state_server : &state_client; -DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long) buff, left); +DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left); while (left > 0) { - DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %lx, %d)\n", (long)buff, - left); - outbytes = gnutls_record_send(tls_session, CS buff, left); + DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n", + buff, left); + outbytes = gnutls_record_send(state->session, buff, left); - DEBUG(D_tls) debug_printf("outbytes=%d\n", outbytes); + DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes); if (outbytes < 0) { - record_io_error(outbytes, US"send", NULL); + record_io_error(state, outbytes, US"send", NULL); return -1; } if (outbytes == 0) { - record_io_error(0, US"send", US"TLS channel closed on write"); + record_io_error(state, 0, US"send", US"TLS channel closed on write"); return -1; } @@ -1179,39 +2012,168 @@ while (left > 0) buff += outbytes; } -return len; +if (len > INT_MAX) + { + DEBUG(D_tls) + debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n", + len); + len = INT_MAX; + } + +return (int) len; } + /************************************************* -* Close down a TLS session * +* Random number generation * *************************************************/ -/* 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 TLS session in the parent process). +/* 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: TRUE if gnutls_bye is to be called -Returns: nothing +Arguments: + max range maximum +Returns a random number in range [0, max-1] */ -void -tls_close(BOOL shutdown) +#ifdef HAVE_GNUTLS_RND +int +vaguely_random_number(int max) { -if (tls_active < 0) return; /* TLS was not active */ +unsigned int r; +int i, needed_len; +uschar *p; +uschar smallbuf[sizeof(r)]; + +if (max <= 1) + return 0; + +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; + +i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len); +if (i < 0) + { + DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n"); + return vaguely_random_number_fallback(max); + } +r = 0; +for (p = smallbuf; needed_len; --needed_len, ++p) + { + r *= 256; + r += *p; + } -if (shutdown) +/* 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; +} +#else /* HAVE_GNUTLS_RND */ +int +vaguely_random_number(int max) +{ + return vaguely_random_number_fallback(max); +} +#endif /* HAVE_GNUTLS_RND */ + + + + +/************************************************* +* 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) +{ +int rc; +uschar *expciphers = NULL; +gnutls_priority_t priority_cache; +const char *errpos; + +#define validate_check_rc(Label) do { \ + if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \ + return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0) +#define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0) + +if (exim_gnutls_base_init_done) + log_write(0, LOG_MAIN|LOG_PANIC, + "already initialised GnuTLS, Exim developer bug"); + +#ifdef HAVE_GNUTLS_PKCS11 +if (!gnutls_allow_auto_pkcs11) { - DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n"); - gnutls_bye(tls_session, GNUTLS_SHUT_WR); + rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); + validate_check_rc(US"gnutls_pkcs11_init"); } +#endif +rc = gnutls_global_init(); +validate_check_rc(US"gnutls_global_init()"); +exim_gnutls_base_init_done = TRUE; + +if (!(tls_require_ciphers && *tls_require_ciphers)) + return_deinit(NULL); + +if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers)) + return_deinit(US"failed to expand tls_require_ciphers"); + +if (!(expciphers && *expciphers)) + return_deinit(NULL); + +DEBUG(D_tls) + debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers); -gnutls_deinit(tls_session); -tls_session = NULL; +rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos); +validate_check_rc(string_sprintf( + "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"", + expciphers, errpos - CS expciphers, errpos)); + +#undef return_deinit +#undef validate_check_rc gnutls_global_deinit(); -tls_active = -1; +return NULL; +} + + + + +/************************************************* +* Report the library versions. * +*************************************************/ + +/* See a description in tls-openssl.c for an explanation of why this exists. + +Arguments: a FILE* to print the results to +Returns: nothing +*/ + +void +tls_version_report(FILE *f) +{ +fprintf(f, "Library version: GnuTLS: Compile: %s\n" + " Runtime: %s\n", + LIBGNUTLS_VERSION, + gnutls_check_version(NULL)); } +/* vi: aw ai sw=2 +*/ /* End of tls-gnu.c */