From 23bb69826c8d600ce4a268ad27e14b0390e540c8 Mon Sep 17 00:00:00 2001 From: Jeremy Harris Date: Wed, 4 May 2016 14:48:41 +0100 Subject: TLS: when tls_certificates unset, generate a selfsigned cert --- src/src/readconf.c | 4 +- src/src/tls-gnu.c | 82 ++++++++++++++++++++++++---- src/src/tls-openssl.c | 144 ++++++++++++++++++++++++++++++++++++++------------ 3 files changed, 182 insertions(+), 48 deletions(-) (limited to 'src') diff --git a/src/src/readconf.c b/src/src/readconf.c index ba4cb668b..375f01a1a 100644 --- a/src/src/readconf.c +++ b/src/src/readconf.c @@ -2963,8 +2963,8 @@ if ( !tls_advertise_hosts ) return TRUE; else if (!nowarn && !tls_certificate) - log_write(0, LOG_MAIN|LOG_PANIC, - "Warning: No server certificate defined; TLS connections will fail.\n" + log_write(0, LOG_MAIN, + "Warning: No server certificate defined; will use a selfsigned one.\n" " Suggested action: either install a certificate or change tls_advertise_hosts option"); oldsignal = signal(SIGCHLD, SIG_DFL); diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c index 316906517..522bb9026 100644 --- a/src/src/tls-gnu.c +++ b/src/src/tls-gnu.c @@ -709,6 +709,70 @@ return OK; +/* Create and install a selfsigned certificate, for use in server mode */ + +static int +tls_install_selfsign(exim_gnutls_state_st * state) +{ +gnutls_x509_crt_t cert = NULL; +time_t now; +gnutls_x509_privkey_t pkey = NULL; +const uschar * where; +int rc; + +where = US"initialising pkey"; +if ((rc = gnutls_x509_privkey_init(&pkey))) goto err; + +where = US"initialising cert"; +if ((rc = gnutls_x509_crt_init(&cert))) goto err; + +where = US"generating pkey"; +if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA, + gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_LOW), + 0))) /* _to_pk_bits() Since: 2.12.0 */ + goto err; + +where = US"configuring cert"; +now = 0; +if ( (rc = gnutls_x509_crt_set_version(cert, 3)) + || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now))) + || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL))) + || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */ + || (rc = gnutls_x509_crt_set_key(cert, pkey)) + + || (rc = gnutls_x509_crt_set_dn_by_oid(cert, + GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2)) + || (rc = gnutls_x509_crt_set_dn_by_oid(cert, + GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15)) + || (rc = gnutls_x509_crt_set_dn_by_oid(cert, + GNUTLS_OID_X520_COMMON_NAME, 0, + smtp_active_hostname, Ustrlen(smtp_active_hostname))) + ) + goto err; + +where = US"signing cert"; +if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err; + +where = US"installing selfsign cert"; + /* Since: 2.4.0 */ +if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey))) + goto err; + +rc = OK; + +out: + if (cert) gnutls_x509_crt_deinit(cert); + if (pkey) gnutls_x509_privkey_deinit(pkey); + return rc; + +err: + rc = tls_error(where, gnutls_strerror(rc), NULL); + goto out; +} + + + + /************************************************* * Variables re-expanded post-SNI * *************************************************/ @@ -741,7 +805,6 @@ int cert_count; /* We check for tls_sni *before* expansion. */ if (!host) /* server */ - { if (!state->received_sni) { if (state->tls_certificate && @@ -762,7 +825,6 @@ if (!host) /* server */ saved_tls_verify_certificates = state->exp_tls_verify_certificates; saved_tls_crl = state->exp_tls_crl; } - } rc = gnutls_certificate_allocate_credentials(&state->x509_cred); exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); @@ -779,14 +841,13 @@ if (!expand_check_tlsvar(tls_certificate)) /* certificate is mandatory in server, optional in client */ -if ((state->exp_tls_certificate == NULL) || - (*state->exp_tls_certificate == '\0')) - { +if ( !state->exp_tls_certificate + || !*state->exp_tls_certificate + ) if (!host) - return tls_error(US"no TLS server certificate is specified", NULL, NULL); + return tls_install_selfsign(state); else DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n"); - } if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey)) return DEFER; @@ -806,9 +867,9 @@ if (state->exp_tls_certificate && *state->exp_tls_certificate) 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)) + 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"); } @@ -816,7 +877,6 @@ if (state->exp_tls_certificate && *state->exp_tls_certificate) { 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, diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c index 6036bce52..c24eb4544 100644 --- a/src/src/tls-openssl.c +++ b/src/src/tls-openssl.c @@ -214,7 +214,7 @@ Returns: OK/DEFER/FAIL */ static int -tls_error(uschar * prefix, const host_item * host, uschar * msg) +tls_error(uschar * prefix, const host_item * host, uschar * msg) { if (!msg) { @@ -273,8 +273,7 @@ if ( !BN_set_word(bn, (unsigned long)RSA_F4) || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL) ) #else -rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL); -if (rsa_key == NULL) +if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL))) #endif { @@ -915,6 +914,73 @@ return; +/* Create and install a selfsigned certificate, for use in server mode */ + +static int +tls_install_selfsign(SSL_CTX * sctx) +{ +X509 * x509 = NULL; +EVP_PKEY * pkey; +RSA * rsa; +X509_NAME * name; +uschar * where; + +where = US"allocating pkey"; +if (!(pkey = EVP_PKEY_new())) + goto err; + +where = US"allocating cert"; +if (!(x509 = X509_new())) + goto err; + +where = US"generating pkey"; + /* deprecated, use RSA_generate_key_ex() */ +if (!(rsa = RSA_generate_key(1024, RSA_F4, NULL, NULL))) + goto err; + +where = US"assiging pkey"; +if (!EVP_PKEY_assign_RSA(pkey, rsa)) + goto err; + +X509_set_version(x509, 2); /* N+1 - version 3 */ +ASN1_INTEGER_set(X509_get_serialNumber(x509), 0); +X509_gmtime_adj(X509_get_notBefore(x509), 0); +X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */ +X509_set_pubkey(x509, pkey); + +name = X509_get_subject_name(x509); +X509_NAME_add_entry_by_txt(name, "C", + MBSTRING_ASC, "UK", -1, -1, 0); +X509_NAME_add_entry_by_txt(name, "O", + MBSTRING_ASC, "Exim Developers", -1, -1, 0); +X509_NAME_add_entry_by_txt(name, "CN", + MBSTRING_ASC, CS smtp_active_hostname, -1, -1, 0); +X509_set_issuer_name(x509, name); + +where = US"signing cert"; +if (!X509_sign(x509, pkey, EVP_md5())) + goto err; + +where = US"installing selfsign cert"; +if (!SSL_CTX_use_certificate(sctx, x509)) + goto err; + +where = US"installing selfsign key"; +if (!SSL_CTX_use_PrivateKey(sctx, pkey)) + goto err; + +return OK; + +err: + (void) tls_error(where, NULL, NULL); + if (x509) X509_free(x509); + if (pkey) EVP_PKEY_free(pkey); + return DEFER; +} + + + + /************************************************* * Expand key and cert file specs * *************************************************/ @@ -935,41 +1001,49 @@ tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo) { uschar *expanded; -if (cbinfo->certificate == NULL) - return OK; - -if (Ustrstr(cbinfo->certificate, US"tls_sni") || - Ustrstr(cbinfo->certificate, US"tls_in_sni") || - Ustrstr(cbinfo->certificate, US"tls_out_sni") - ) - reexpand_tls_files_for_sni = TRUE; - -if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded)) - return DEFER; - -if (expanded != NULL) +if (!cbinfo->certificate) { - DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); - if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded)) - return tls_error(string_sprintf( - "SSL_CTX_use_certificate_chain_file file=%s", expanded), - cbinfo->host, NULL); + if (cbinfo->host) /* client */ + return OK; + /* server */ + if (tls_install_selfsign(sctx) != OK) + return DEFER; } +else + { + if (Ustrstr(cbinfo->certificate, US"tls_sni") || + Ustrstr(cbinfo->certificate, US"tls_in_sni") || + Ustrstr(cbinfo->certificate, US"tls_out_sni") + ) + reexpand_tls_files_for_sni = TRUE; -if (cbinfo->privatekey != NULL && - !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded)) - return DEFER; + if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded)) + return DEFER; -/* If expansion was forced to fail, key_expanded will be NULL. If the result -of the expansion is an empty string, ignore it also, and assume the private -key is in the same file as the certificate. */ + if (expanded != NULL) + { + DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); + if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded)) + return tls_error(string_sprintf( + "SSL_CTX_use_certificate_chain_file file=%s", expanded), + cbinfo->host, NULL); + } -if (expanded && *expanded) - { - DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); - if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM)) - return tls_error(string_sprintf( - "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL); + if (cbinfo->privatekey != NULL && + !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded)) + return DEFER; + + /* If expansion was forced to fail, key_expanded will be NULL. If the result + of the expansion is an empty string, ignore it also, and assume the private + key is in the same file as the certificate. */ + + if (expanded && *expanded) + { + DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); + if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM)) + return tls_error(string_sprintf( + "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL); + } } #ifndef DISABLE_OCSP @@ -1429,8 +1503,8 @@ if ( !init_dh(*ctxp, dhparam, host) /* Set up certificate and key (and perhaps OCSP info) */ -rc = tls_expand_session_files(*ctxp, cbinfo); -if (rc != OK) return rc; +if ((rc = tls_expand_session_files(*ctxp, cbinfo)) != OK) + return rc; /* If we need to handle SNI, do so */ #ifdef EXIM_HAVE_OPENSSL_TLSEXT -- cgit v1.2.3