From 1365611d62f130d0a096b322656b5b790628d2c7 Mon Sep 17 00:00:00 2001 From: Phil Pennock Date: Thu, 17 May 2012 02:53:44 -0400 Subject: [PATCH] Get TLS SNI server-switching working with GnuTLS. Registering a cert/key in an x509 credentials *adds* them, and there's no way to remove them, so we need a shiny new x509_cred each time the key/cert change. Since we avoid re-expanding unless tls_sni appears in tls_certificate, we've mostly avoided the expense unless SNI is in use, and the extra loading should be minimal, as everything should be in buffer/cache from a few microseconds beforehand. This code tested with GnuTLS and OpenSSL clients, without TLS extensions, with servername, and verifying we do now get the correct cert. --- src/src/tls-gnu.c | 229 +++++++++++++++++++++++----------------------- 1 file changed, 115 insertions(+), 114 deletions(-) diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c index 8391914b6..a0a35b447 100644 --- a/src/src/tls-gnu.c +++ b/src/src/tls-gnu.c @@ -582,6 +582,7 @@ Returns: OK/DEFER/FAIL 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; @@ -603,6 +604,7 @@ if (!state->host) } 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; @@ -610,6 +612,9 @@ if (!state->host) } } +rc = gnutls_certificate_allocate_credentials(&state->x509_cred); +exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); + /* 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. */ @@ -645,7 +650,6 @@ if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0') if (state->exp_tls_certificate && *state->exp_tls_certificate) { - BOOL setit = TRUE; DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", state->exp_tls_certificate, state->exp_tls_privatekey); @@ -655,7 +659,6 @@ if (state->exp_tls_certificate && *state->exp_tls_certificate) (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0)) { DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n"); - setit = FALSE; } else { @@ -663,16 +666,13 @@ if (state->exp_tls_certificate && *state->exp_tls_certificate) } } - if (setit) - { - 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"); - } + 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 trusted CAs file if one is provided, and then add the CRL if one is @@ -683,112 +683,124 @@ behaviour. */ if (state->tls_verify_certificates && *state->tls_verify_certificates) { - struct stat statbuf; - BOOL setit_vc = TRUE, setit_crl = TRUE; - 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->received_sni) - { - state->exp_tls_verify_certificates, state->exp_tls_verify_certificates, - saved_tls_verify_certificates, saved_tls_verify_certificates); - if (!(state->exp_tls_verify_certificates || saved_tls_verify_certificates)) - setit_vc = FALSE; /* never was set */ - else if (!state->exp_tls_verify_certificates || !saved_tls_verify_certificates) - setit_vc = TRUE; /* changed whether set */ - else if (Ustrcmp(state->exp_tls_verify_certificates, saved_tls_verify_certificates) == 0) - setit_vc = FALSE; /* not changed value */ - - state->exp_tls_crl, state->exp_tls_crl, - saved_tls_crl, saved_tls_crl); - if (!(state->exp_tls_crl || saved_tls_crl)) - setit_crl = FALSE; /* never was set */ - else if (!state->exp_tls_crl || !saved_tls_crl) - setit_crl = TRUE; /* changed whether set */ - else if (Ustrcmp(state->exp_tls_crl, saved_tls_crl) == 0) - setit_crl = FALSE; /* not changed value */ - } - - /* nb: early exit; change if add more expansions to this function */ - if (!(setit_vc || setit_crl)) + if (!(state->exp_tls_verify_certificates && + *state->exp_tls_verify_certificates)) { DEBUG(D_tls) - debug_printf("TLS SNI: no change to tls_crl or tls_verify_certificates\n"); + debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n"); + /* With no tls_verify_certificates, we ignore tls_crl too */ return OK; } + } - 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; - } +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; + } - if (!S_ISREG(statbuf.st_mode)) - { - DEBUG(D_tls) - debug_printf("verify certificates path is not a file: \"%s\"\n%s\n", - state->exp_tls_verify_certificates, - S_ISDIR(statbuf.st_mode) - ? " it's a directory, that's OpenSSL, this is GnuTLS" - : " (not a directory either)"); - log_write(0, LOG_MAIN|LOG_PANIC, - "tls_verify_certificates \"%s\" is not a file", - state->exp_tls_verify_certificates); - return DEFER; - } +if (!S_ISREG(statbuf.st_mode)) + { + DEBUG(D_tls) + debug_printf("verify certificates path is not a file: \"%s\"\n%s\n", + state->exp_tls_verify_certificates, + S_ISDIR(statbuf.st_mode) + ? " it's a directory, that's OpenSSL, this is GnuTLS" + : " (not a directory either)"); + log_write(0, LOG_MAIN|LOG_PANIC, + "tls_verify_certificates \"%s\" is not a file", + state->exp_tls_verify_certificates); + return DEFER; + } - 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("verify certificates = %s size=" OFF_T_FMT "\n", + state->exp_tls_verify_certificates, statbuf.st_size); - /* If the CA cert file is empty, there's no point in loading the CRL file, - as we aren't verifying, so checking for revocation is pointless. */ +if (statbuf.st_size == 0) + { + DEBUG(D_tls) + debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n"); + return OK; + } - if (statbuf.st_size > 0) - { - if (setit_vc) - { - 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); - } - else - { - DEBUG(D_tls) debug_printf("TLS SNI: tls_verify_certificates unchanged\n"); - } +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 (setit_crl && state->tls_crl && *state->tls_crl) - { - if (state->exp_tls_crl && *state->exp_tls_crl) - { - DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); - rc = gnutls_certificate_set_x509_crl_file(state->x509_cred, - CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); - exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file"); - } - } - DEBUG(D_tls) - if (!setit_crl) debug_printf("TLS SNI: tls_crl unchanged\n"); - } /* statbuf.st_size */ - } /* tls_verify_certificates */ +if (state->tls_crl && *state->tls_crl) + { + if (state->exp_tls_crl && *state->exp_tls_crl) + { + DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); + rc = gnutls_certificate_set_x509_crl_file(state->x509_cred, + CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); + exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file"); + } + } return OK; -/* also above, during verify_certificates/crl, during SNI, if unchanged */ } +/************************************************* +* 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 * *************************************************/ @@ -869,9 +881,6 @@ state->tls_sni = sni; state->tls_verify_certificates = cas; state->tls_crl = crl; -rc = gnutls_certificate_allocate_credentials(&state->x509_cred); -exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); - /* This handles the variables that might get re-expanded after TLS SNI; that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */ @@ -880,21 +889,11 @@ DEBUG(D_tls) rc = tls_expand_session_files(state); if (rc != OK) return rc; -/* 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 (!host) - { - 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. */ +/* These are all other parts of the x509_cred handling, since SNI in GnuTLS +requires a new structure afterwards. */ -rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); -exim_gnutls_err_check(US"gnutls_credentials_set"); +rc = tls_set_remaining_x509(state); +if (rc != OK) return rc; /* set SNI in client, only */ if (host) @@ -1214,8 +1213,10 @@ if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; } -rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); -return (rc == GNUTLS_E_SUCCESS) ? 0 : rc; +rc = tls_set_remaining_x509(state); +if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; + +return 0; } -- 2.25.1