/*++ /* NAME /* tls_client /* SUMMARY /* client-side TLS engine /* SYNOPSIS /* #include <tls.h> /* /* TLS_APPL_STATE *tls_client_init(init_props) /* const TLS_CLIENT_INIT_PROPS *init_props; /* /* TLS_SESS_STATE *tls_client_start(start_props) /* const TLS_CLIENT_START_PROPS *start_props; /* /* void tls_client_stop(app_ctx, stream, failure, TLScontext) /* TLS_APPL_STATE *app_ctx; /* VSTREAM *stream; /* int failure; /* TLS_SESS_STATE *TLScontext; /* DESCRIPTION /* This module is the interface between Postfix TLS clients, /* the OpenSSL library and the TLS entropy and cache manager. /* /* The SMTP client will attempt to verify the server hostname /* against the names listed in the server certificate. When /* a hostname match is required, the verification fails /* on certificate verification or hostname mis-match errors. /* When no hostname match is required, hostname verification /* failures are logged but they do not affect the TLS handshake /* or the SMTP session. /* /* The rules for peer name wild-card matching differ between /* RFC 2818 (HTTP over TLS) and RFC 2830 (LDAP over TLS), while /* RFC RFC3207 (SMTP over TLS) does not specify a rule at all. /* Postfix uses a restrictive match algorithm. One asterisk /* ('*') is allowed as the left-most component of a wild-card /* certificate name; it matches the left-most component of /* the peer hostname. /* /* Another area where RFCs aren't always explicit is the /* handling of dNSNames in peer certificates. RFC 3207 (SMTP /* over TLS) does not mention dNSNames. Postfix follows the /* strict rules in RFC 2818 (HTTP over TLS), section 3.1: The /* Subject Alternative Name/dNSName has precedence over /* CommonName. If at least one dNSName is provided, Postfix /* verifies those against the peer hostname and ignores the /* CommonName, otherwise Postfix verifies the CommonName /* against the peer hostname. /* /* tls_client_init() is called once when the SMTP client /* initializes. /* Certificate details are also decided during this phase, /* so peer-specific certificate selection is not possible. /* /* tls_client_start() activates the TLS session over an established /* stream. We expect that network buffers are flushed and /* the TLS handshake can begin immediately. /* /* tls_client_stop() sends the "close notify" alert via /* SSL_shutdown() to the peer and resets all connection specific /* TLS data. As RFC2487 does not specify a separate shutdown, it /* is assumed that the underlying TCP connection is shut down /* immediately afterwards. Any further writes to the channel will /* be discarded, and any further reads will report end-of-file. /* If the failure flag is set, no SSL_shutdown() handshake is performed. /* /* Once the TLS connection is initiated, information about the TLS /* state is available via the TLScontext structure: /* .IP TLScontext->protocol /* the protocol name (SSLv2, SSLv3, TLSv1), /* .IP TLScontext->cipher_name /* the cipher name (e.g. RC4/MD5), /* .IP TLScontext->cipher_usebits /* the number of bits actually used (e.g. 40), /* .IP TLScontext->cipher_algbits /* the number of bits the algorithm is based on (e.g. 128). /* .PP /* The last two values may differ from each other when export-strength /* encryption is used. /* /* If the peer offered a certificate, part of the certificate data are /* available as: /* .IP TLScontext->peer_status /* A bitmask field that records the status of the peer certificate /* verification. This consists of one or more of /* TLS_CERT_FLAG_PRESENT, TLS_CERT_FLAG_ALTNAME, TLS_CERT_FLAG_TRUSTED, /* TLS_CERT_FLAG_MATCHED and TLS_CERT_FLAG_SECURED. /* .IP TLScontext->peer_CN /* Extracted CommonName of the peer, or zero-length string if the /* information could not be extracted. /* .IP TLScontext->issuer_CN /* Extracted CommonName of the issuer, or zero-length string if the /* information could not be extracted. /* .IP TLScontext->peer_cert_fprint /* At the fingerprint security level, if the peer presented a certificate /* the fingerprint of the certificate. /* .PP /* If no peer certificate is presented the peer_status is set to 0. /* LICENSE /* .ad /* .fi /* This software is free. You can do with it whatever you want. /* The original author kindly requests that you acknowledge /* the use of his software. /* AUTHOR(S) /* Originally written by: /* Lutz Jaenicke /* BTU Cottbus /* Allgemeine Elektrotechnik /* Universitaetsplatz 3-4 /* D-03044 Cottbus, Germany /* /* Updated by: /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /* /* Victor Duchovni /* Morgan Stanley /*--*/ /* System library. */ #include <sys_defs.h> #ifdef USE_TLS #include <string.h> #ifdef STRCASECMP_IN_STRINGS_H #include <strings.h> #endif /* Utility library. */ #include <argv.h> #include <mymalloc.h> #include <vstring.h> #include <vstream.h> #include <stringops.h> #include <msg.h> #include <iostuff.h> /* non-blocking */ #include <midna_domain.h> /* Global library. */ #include <mail_params.h> /* TLS library. */ #include <tls_mgr.h> #define TLS_INTERNAL #include <tls.h> /* Application-specific. */ #define STR vstring_str #define LEN VSTRING_LEN /* load_clnt_session - load session from client cache (non-callback) */ static SSL_SESSION *load_clnt_session(TLS_SESS_STATE *TLScontext) { const char *myname = "load_clnt_session"; SSL_SESSION *session = 0; VSTRING *session_data = vstring_alloc(2048); /* * Prepare the query. */ if (TLScontext->log_mask & TLS_LOG_CACHE) /* serverid contains transport:addr:port information */ msg_info("looking for session %s in %s cache", TLScontext->serverid, TLScontext->cache_type); /* * We only get here if the cache_type is not empty. This code is not * called unless caching is enabled and the cache_type is stored in the * server SSL context. */ if (TLScontext->cache_type == 0) msg_panic("%s: null client session cache type in session lookup", myname); /* * Look up and activate the SSL_SESSION object. Errors are non-fatal, * since caching is only an optimization. */ if (tls_mgr_lookup(TLScontext->cache_type, TLScontext->serverid, session_data) == TLS_MGR_STAT_OK) { session = tls_session_activate(STR(session_data), LEN(session_data)); if (session) { if (TLScontext->log_mask & TLS_LOG_CACHE) /* serverid contains transport:addr:port information */ msg_info("reloaded session %s from %s cache", TLScontext->serverid, TLScontext->cache_type); } } /* * Clean up. */ vstring_free(session_data); return (session); } /* new_client_session_cb - name new session and save it to client cache */ static int new_client_session_cb(SSL *ssl, SSL_SESSION *session) { const char *myname = "new_client_session_cb"; TLS_SESS_STATE *TLScontext; VSTRING *session_data; /* * The cache name (if caching is enabled in tlsmgr(8)) and the cache ID * string for this session are stored in the TLScontext. It cannot be * null at this point. */ if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) msg_panic("%s: null TLScontext in new session callback", myname); /* * We only get here if the cache_type is not empty. This callback is not * set unless caching is enabled and the cache_type is stored in the * server SSL context. */ if (TLScontext->cache_type == 0) msg_panic("%s: null session cache type in new session callback", myname); if (TLScontext->log_mask & TLS_LOG_CACHE) /* serverid contains transport:addr:port information */ msg_info("save session %s to %s cache", TLScontext->serverid, TLScontext->cache_type); /* * Passivate and save the session object. Errors are non-fatal, since * caching is only an optimization. */ if ((session_data = tls_session_passivate(session)) != 0) { tls_mgr_update(TLScontext->cache_type, TLScontext->serverid, STR(session_data), LEN(session_data)); vstring_free(session_data); } /* * Clean up. */ SSL_SESSION_free(session); /* 200502 */ return (1); } /* uncache_session - remove session from the external cache */ static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext) { SSL_SESSION *session = SSL_get_session(TLScontext->con); SSL_CTX_remove_session(ctx, session); if (TLScontext->cache_type == 0 || TLScontext->serverid == 0) return; if (TLScontext->log_mask & TLS_LOG_CACHE) /* serverid contains transport:addr:port information */ msg_info("remove session %s from client cache", TLScontext->serverid); tls_mgr_delete(TLScontext->cache_type, TLScontext->serverid); } /* tls_client_init - initialize client-side TLS engine */ TLS_APPL_STATE *tls_client_init(const TLS_CLIENT_INIT_PROPS *props) { long off = 0; int cachable; int scache_timeout; SSL_CTX *client_ctx; TLS_APPL_STATE *app_ctx; int log_mask; /* * Convert user loglevel to internal logmask. */ log_mask = tls_log_mask(props->log_param, props->log_level); if (log_mask & TLS_LOG_VERBOSE) msg_info("initializing the client-side TLS engine"); /* * Load (mostly cipher related) TLS-library internal main.cf parameters. */ tls_param_init(); /* * Detect mismatch between compile-time headers and run-time library. */ tls_check_version(); #if OPENSSL_VERSION_NUMBER < 0x10100000L /* * Initialize the OpenSSL library by the book! To start with, we must * initialize the algorithms. We want cleartext error messages instead of * just error codes, so we load the error_strings. */ SSL_load_error_strings(); OpenSSL_add_ssl_algorithms(); #endif /* * Create an application data index for SSL objects, so that we can * attach TLScontext information; this information is needed inside * tls_verify_certificate_callback(). */ if (TLScontext_index < 0) { if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) { msg_warn("Cannot allocate SSL application data index: " "disabling TLS support"); return (0); } } /* * If the administrator specifies an unsupported digest algorithm, fail * now, rather than in the middle of a TLS handshake. */ if (!tls_validate_digest(props->mdalg)) { msg_warn("disabling TLS support"); return (0); } /* * Initialize the PRNG (Pseudo Random Number Generator) with some seed * from external and internal sources. Don't enable TLS without some real * entropy. */ if (tls_ext_seed(var_tls_daemon_rand_bytes) < 0) { msg_warn("no entropy for TLS key generation: disabling TLS support"); return (0); } tls_int_seed(); /* * The SSL/TLS specifications require the client to send a message in the * oldest specification it understands with the highest level it * understands in the message. RFC2487 is only specified for TLSv1, but * we want to be as compatible as possible, so we will start off with a * SSLv2 greeting allowing the best we can offer: TLSv1. We can restrict * this with the options setting later, anyhow. */ ERR_clear_error(); client_ctx = SSL_CTX_new(TLS_client_method()); if (client_ctx == 0) { msg_warn("cannot allocate client SSL_CTX: disabling TLS support"); tls_print_errors(); return (0); } #ifdef SSL_SECOP_PEER /* Backwards compatible security as a base for opportunistic TLS. */ SSL_CTX_set_security_level(client_ctx, 0); #endif /* * See the verify callback in tls_verify.c */ SSL_CTX_set_verify_depth(client_ctx, props->verifydepth + 1); /* * Protocol selection is destination dependent, so we delay the protocol * selection options to the per-session SSL object. */ off |= tls_bug_bits(); SSL_CTX_set_options(client_ctx, off); /* * Set the call-back routine for verbose logging. */ if (log_mask & TLS_LOG_DEBUG) SSL_CTX_set_info_callback(client_ctx, tls_info_callback); /* * Load the CA public key certificates for both the client cert and for * the verification of server certificates. As provided by OpenSSL we * support two types of CA certificate handling: One possibility is to * add all CA certificates to one large CAfile, the other possibility is * a directory pointed to by CApath, containing separate files for each * CA with softlinks named after the hash values of the certificate. The * first alternative has the advantage that the file is opened and read * at startup time, so that you don't have the hassle to maintain another * copy of the CApath directory for chroot-jail. */ if (tls_set_ca_certificate_info(client_ctx, props->CAfile, props->CApath) < 0) { /* tls_set_ca_certificate_info() already logs a warning. */ SSL_CTX_free(client_ctx); /* 200411 */ return (0); } /* * We do not need a client certificate, so the certificates are only * loaded (and checked) if supplied. A clever client would handle * multiple client certificates and decide based on the list of * acceptable CAs, sent by the server, which certificate to submit. * OpenSSL does however not do this and also has no call-back hooks to * easily implement it. * * Load the client public key certificate and private key from file and * check whether the cert matches the key. We can use RSA certificates * ("cert") DSA certificates ("dcert") or ECDSA certificates ("eccert"). * All three can be made available at the same time. The CA certificates * for all three are handled in the same setup already finished. Which * one is used depends on the cipher negotiated (that is: the first * cipher listed by the client which does match the server). The client * certificate is presented after the server chooses the session cipher, * so we will just present the right cert for the chosen cipher (if it * uses certificates). */ if (tls_set_my_certificate_key_info(client_ctx, props->cert_file, props->key_file, props->dcert_file, props->dkey_file, props->eccert_file, props->eckey_file) < 0) { /* tls_set_my_certificate_key_info() already logs a warning. */ SSL_CTX_free(client_ctx); /* 200411 */ return (0); } /* * 2015-12-05: Ephemeral RSA removed from OpenSSL 1.1.0-dev */ #if OPENSSL_VERSION_NUMBER < 0x10100000L /* * According to the OpenSSL documentation, temporary RSA key is needed * export ciphers are in use. We have to provide one, so well, we just do * it. */ SSL_CTX_set_tmp_rsa_callback(client_ctx, tls_tmp_rsa_cb); #endif /* * With OpenSSL 1.0.2 and later the client EECDH curve list becomes * configurable with the preferred curve negotiated via the supported * curves extension. */ tls_auto_eecdh_curves(client_ctx); /* * Finally, the setup for the server certificate checking, done "by the * book". */ SSL_CTX_set_verify(client_ctx, SSL_VERIFY_NONE, tls_verify_certificate_callback); /* * Initialize the session cache. * * Since the client does not search an internal cache, we simply disable it. * It is only useful for expiring old sessions, but we do that in the * tlsmgr(8). * * This makes SSL_CTX_remove_session() not useful for flushing broken * sessions from the external cache, so we must delete them directly (not * via a callback). */ if (tls_mgr_policy(props->cache_type, &cachable, &scache_timeout) != TLS_MGR_STAT_OK) scache_timeout = 0; if (scache_timeout <= 0) cachable = 0; /* * Allocate an application context, and populate with mandatory protocol * and cipher data. */ app_ctx = tls_alloc_app_context(client_ctx, log_mask); /* * The external session cache is implemented by the tlsmgr(8) process. */ if (cachable) { app_ctx->cache_type = mystrdup(props->cache_type); /* * OpenSSL does not use callbacks to load sessions from a client * cache, so we must invoke that function directly. Apparently, * OpenSSL does not provide a way to pass session names from here to * call-back routines that do session lookup. * * OpenSSL can, however, automatically save newly created sessions for * us by callback (we create the session name in the call-back * function). * * XXX gcc 2.95 can't compile #ifdef .. #endif in the expansion of * SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_NO_INTERNAL_STORE | * SSL_SESS_CACHE_NO_AUTO_CLEAR. */ #ifndef SSL_SESS_CACHE_NO_INTERNAL_STORE #define SSL_SESS_CACHE_NO_INTERNAL_STORE 0 #endif SSL_CTX_set_session_cache_mode(client_ctx, SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_NO_INTERNAL_STORE | SSL_SESS_CACHE_NO_AUTO_CLEAR); SSL_CTX_sess_set_new_cb(client_ctx, new_client_session_cb); /* * OpenSSL ignores timed-out sessions. We need to set the internal * cache timeout at least as high as the external cache timeout. This * applies even if no internal cache is used. We set the session to * twice the cache lifetime. This way a session always lasts longer * than its lifetime in the cache. */ SSL_CTX_set_timeout(client_ctx, 2 * scache_timeout); } return (app_ctx); } /* match_servername - match servername against pattern */ static int match_servername(const char *certid, const TLS_CLIENT_START_PROPS *props) { const ARGV *cmatch_argv; const char *nexthop = props->nexthop; const char *hname = props->host; const char *domain; const char *parent; const char *aname; int match_subdomain; int i; int idlen; int domlen; if ((cmatch_argv = props->matchargv) == 0) return 0; #ifndef NO_EAI /* * DNS subjectAltNames are required to be ASCII. * * Per RFC 6125 Section 6.4.4 Matching the CN-ID, follows the same rules * (6.4.1, 6.4.2 and 6.4.3) that apply to subjectAltNames. In * particular, 6.4.2 says that the reference identifier is coerced to * ASCII, but no conversion is stated or implied for the CN-ID, so it * seems it only matches if it is all ASCII. Otherwise, it is some other * sort of name. */ if (!allascii(certid)) return (0); if (!allascii(nexthop) && (aname = midna_domain_to_ascii(nexthop)) != 0) { if (msg_verbose) msg_info("%s asciified to %s", nexthop, aname); nexthop = aname; } #endif /* * Match the certid against each pattern until we find a match. */ for (i = 0; i < cmatch_argv->argc; ++i) { match_subdomain = 0; if (!strcasecmp(cmatch_argv->argv[i], "nexthop")) domain = nexthop; else if (!strcasecmp(cmatch_argv->argv[i], "hostname")) domain = hname; else if (!strcasecmp(cmatch_argv->argv[i], "dot-nexthop")) { domain = nexthop; match_subdomain = 1; } else { domain = cmatch_argv->argv[i]; if (*domain == '.') { if (domain[1]) { ++domain; match_subdomain = 1; } } #ifndef NO_EAI /* * Besides U+002E (full stop) IDNA2003 allows labels to be * separated by any of the Unicode variants U+3002 (ideographic * full stop), U+FF0E (fullwidth full stop), and U+FF61 * (halfwidth ideographic full stop). Their respective UTF-8 * encodings are: E38082, EFBC8E and EFBDA1. * * IDNA2008 does not permit (upper) case and other variant * differences in U-labels. The midna_domain_to_ascii() function, * based on UTS46, normalizes such differences away. * * The IDNA to_ASCII conversion does not allow empty leading labels, * so we handle these explicitly here. */ else { unsigned char *cp = (unsigned char *) domain; if ((cp[0] == 0xe3 && cp[1] == 0x80 && cp[2] == 0x82) || (cp[0] == 0xef && cp[1] == 0xbc && cp[2] == 0x8e) || (cp[0] == 0xef && cp[1] == 0xbd && cp[2] == 0xa1)) { if (domain[3]) { domain = domain + 3; match_subdomain = 1; } } } if (!allascii(domain) && (aname = midna_domain_to_ascii(domain)) != 0) { if (msg_verbose) msg_info("%s asciified to %s", domain, aname); domain = aname; } #endif } /* * Sub-domain match: certid is any sub-domain of hostname. */ if (match_subdomain) { if ((idlen = strlen(certid)) > (domlen = strlen(domain)) + 1 && certid[idlen - domlen - 1] == '.' && !strcasecmp(certid + (idlen - domlen), domain)) return (1); else continue; } /* * Exact match and initial "*" match. The initial "*" in a certid * matches one (if var_tls_multi_label is false) or more hostname * components under the condition that the certid contains multiple * hostname components. */ if (!strcasecmp(certid, domain) || (certid[0] == '*' && certid[1] == '.' && certid[2] != 0 && (parent = strchr(domain, '.')) != 0 && (idlen = strlen(certid + 1)) <= (domlen = strlen(parent)) && strcasecmp(var_tls_multi_wildcard == 0 ? parent : parent + domlen - idlen, certid + 1) == 0)) return (1); } return (0); } /* verify_extract_name - verify peer name and extract peer information */ static void verify_extract_name(TLS_SESS_STATE *TLScontext, X509 *peercert, const TLS_CLIENT_START_PROPS *props) { int i; int r; int matched = 0; int dnsname_match; int verify_peername = 0; int log_certmatch; int verbose; const char *dnsname; const GENERAL_NAME *gn; general_name_stack_t *gens; /* * On exit both peer_CN and issuer_CN should be set. */ TLScontext->issuer_CN = tls_issuer_CN(peercert, TLScontext); /* * Is the certificate trust chain valid and trusted? */ if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; /* * With fingerprint or dane we may already be done. Otherwise, verify the * peername if using traditional PKI or DANE with trust-anchors. */ if (!TLS_CERT_IS_MATCHED(TLScontext) && TLS_CERT_IS_TRUSTED(TLScontext) && TLS_MUST_TRUST(props->tls_level)) verify_peername = 1; /* Force cert processing so we can log the data? */ log_certmatch = TLScontext->log_mask & TLS_LOG_CERTMATCH; /* Log cert details when processing? */ verbose = log_certmatch || (TLScontext->log_mask & TLS_LOG_VERBOSE); if (verify_peername || log_certmatch) { /* * Verify the dNSName(s) in the peer certificate against the nexthop * and hostname. * * If DNS names are present, we use the first matching (or else simply * the first) DNS name as the subject CN. The CommonName in the * issuer DN is obsolete when SubjectAltName is available. This * yields much less surprising logs, because we log the name we * verified or a name we checked and failed to match. * * XXX: The nexthop and host name may both be the same network address * rather than a DNS name. In this case we really should be looking * for GEN_IPADD entries, not GEN_DNS entries. * * XXX: In ideal world the caller who used the address to build the * connection would tell us that the nexthop is the connection * address, but if that is not practical, we can parse the nexthop * again here. */ gens = X509_get_ext_d2i(peercert, NID_subject_alt_name, 0, 0); if (gens) { r = sk_GENERAL_NAME_num(gens); for (i = 0; i < r; ++i) { gn = sk_GENERAL_NAME_value(gens, i); if (gn->type != GEN_DNS) continue; /* * Even if we have an invalid DNS name, we still ultimately * ignore the CommonName, because subjectAltName:DNS is * present (though malformed). Replace any previous peer_CN * if empty or we get a match. * * We always set at least an empty peer_CN if the ALTNAME cert * flag is set. If not, we set peer_CN from the cert * CommonName below, so peer_CN is always non-null on return. */ TLScontext->peer_status |= TLS_CERT_FLAG_ALTNAME; dnsname = tls_dns_name(gn, TLScontext); if (dnsname && *dnsname) { if ((dnsname_match = match_servername(dnsname, props)) != 0) matched++; /* Keep the first matched name. */ if (TLScontext->peer_CN && ((dnsname_match && matched == 1) || *TLScontext->peer_CN == 0)) { myfree(TLScontext->peer_CN); TLScontext->peer_CN = 0; } if (verbose) msg_info("%s: %ssubjectAltName: %s", props->namaddr, dnsname_match ? "Matched " : "", dnsname); } if (TLScontext->peer_CN == 0) TLScontext->peer_CN = mystrdup(dnsname ? dnsname : ""); if (matched && !log_certmatch) break; } if (verify_peername && matched) TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED; /* * (Sam Rushing, Ironport) Free stack *and* member GENERAL_NAME * objects */ sk_GENERAL_NAME_pop_free(gens, GENERAL_NAME_free); } /* * No subjectAltNames, peer_CN is taken from CommonName. */ if (TLScontext->peer_CN == 0) { TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext); if (*TLScontext->peer_CN) matched = match_servername(TLScontext->peer_CN, props); if (verify_peername && matched) TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED; if (verbose) msg_info("%s %sCommonName %s", props->namaddr, matched ? "Matched " : "", TLScontext->peer_CN); } else if (verbose) { char *tmpcn = tls_peer_CN(peercert, TLScontext); /* * Though the CommonName was superceded by a subjectAltName, log * it when certificate match debugging was requested. */ msg_info("%s CommonName %s", TLScontext->namaddr, tmpcn); myfree(tmpcn); } } else TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext); /* * Give them a clue. Problems with trust chain verification are logged * when the session is first negotiated, before the session is stored * into the cache. We don't want mystery failures, so log the fact the * real problem is to be found in the past. */ if (!TLS_CERT_IS_TRUSTED(TLScontext) && (TLScontext->log_mask & TLS_LOG_UNTRUSTED)) { if (TLScontext->session_reused == 0) tls_log_verify_error(TLScontext); else msg_info("%s: re-using session with untrusted certificate, " "look for details earlier in the log", props->namaddr); } } /* verify_extract_print - extract and verify peer fingerprint */ static void verify_extract_print(TLS_SESS_STATE *TLScontext, X509 *peercert, const TLS_CLIENT_START_PROPS *props) { TLScontext->peer_cert_fprint = tls_cert_fprint(peercert, props->mdalg); TLScontext->peer_pkey_fprint = tls_pkey_fprint(peercert, props->mdalg); /* * Whether the level is "dane" or "fingerprint" when the peer certificate * is matched without resorting to a separate CA, we set both the trusted * and matched bits. This simplifies logic in smtp_proto.c where "dane" * must be trusted and matched, since some "dane" TLSA RRsets do use CAs. * * This also suppresses spurious logging of the peer certificate as * untrusted in verify_extract_name(). */ if (TLS_DANE_HASEE(props->dane) && tls_dane_match(TLScontext, TLS_DANE_EE, peercert, 0)) TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED | TLS_CERT_FLAG_MATCHED; } /* * This is the actual startup routine for the connection. We expect that the * buffers are flushed and the "220 Ready to start TLS" was received by us, * so that we can immediately start the TLS handshake process. */ TLS_SESS_STATE *tls_client_start(const TLS_CLIENT_START_PROPS *props) { int sts; int protomask; const char *cipher_list; SSL_SESSION *session = 0; SSL_CIPHER_const SSL_CIPHER *cipher; X509 *peercert; TLS_SESS_STATE *TLScontext; TLS_APPL_STATE *app_ctx = props->ctx; char *myserverid; int log_mask = app_ctx->log_mask; /* * When certificate verification is required, log trust chain validation * errors even when disabled by default for opportunistic sessions. For * DANE this only applies when using trust-anchor associations. */ if (TLS_MUST_TRUST(props->tls_level) && (!TLS_DANE_BASED(props->tls_level) || TLS_DANE_HASTA(props->dane))) log_mask |= TLS_LOG_UNTRUSTED; if (log_mask & TLS_LOG_VERBOSE) msg_info("setting up TLS connection to %s", props->namaddr); /* * First make sure we have valid protocol and cipher parameters * * Per-session protocol restrictions must be applied to the SSL connection, * as restrictions in the global context cannot be cleared. */ protomask = tls_protocol_mask(props->protocols); if (protomask == TLS_PROTOCOL_INVALID) { /* tls_protocol_mask() logs no warning. */ msg_warn("%s: Invalid TLS protocol list \"%s\": aborting TLS session", props->namaddr, props->protocols); return (0); } /* DANE requires SSLv3 or later, not SSLv2. */ if (TLS_DANE_BASED(props->tls_level)) protomask |= TLS_PROTOCOL_SSLv2; /* * Per session cipher selection for sessions with mandatory encryption * * The cipherlist is applied to the global SSL context, since it is likely * to stay the same between connections, so we make use of a 1-element * cache to return the same result for identical inputs. */ cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade, props->cipher_exclusions); if (cipher_list == 0) { msg_warn("%s: %s: aborting TLS session", props->namaddr, vstring_str(app_ctx->why)); return (0); } if (log_mask & TLS_LOG_VERBOSE) msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); /* * OpenSSL will ignore cached sessions that use the wrong protocol. So we * do not need to filter out cached sessions with the "wrong" protocol, * rather OpenSSL will simply negotiate a new session. * * We salt the session lookup key with the protocol list, so that sessions * found in the cache are plausibly acceptable. * * By the time a TLS client is negotiating ciphers it has already offered to * re-use a session, it is too late to renege on the offer. So we must * not attempt to re-use sessions whose ciphers are too weak. We salt the * session lookup key with the cipher list, so that sessions found in the * cache are always acceptable. * * With DANE, (more generally any TLScontext where we specified explicit * trust-anchor or end-entity certificates) the verification status of * the SSL session depends on the specified list. Since we verify the * certificate only during the initial handshake, we must segregate * sessions with different TA lists. Note, that TA re-verification is * not possible with cached sessions, since these don't hold the complete * peer trust chain. Therefore, we compute a digest of the sorted TA * parameters and append it to the serverid. */ myserverid = tls_serverid_digest(props, protomask, cipher_list); /* * Allocate a new TLScontext for the new connection and get an SSL * structure. Add the location of TLScontext to the SSL to later retrieve * the information inside the tls_verify_certificate_callback(). * * If session caching was enabled when TLS was initialized, the cache type * is stored in the client SSL context. */ TLScontext = tls_alloc_sess_context(log_mask, props->namaddr); TLScontext->cache_type = app_ctx->cache_type; TLScontext->serverid = myserverid; TLScontext->stream = props->stream; TLScontext->mdalg = props->mdalg; /* Alias DANE digest info from props */ TLScontext->dane = props->dane; if ((TLScontext->con = SSL_new(app_ctx->ssl_ctx)) == NULL) { msg_warn("Could not allocate 'TLScontext->con' with SSL_new()"); tls_print_errors(); tls_free_context(TLScontext); return (0); } if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) { msg_warn("Could not set application data for 'TLScontext->con'"); tls_print_errors(); tls_free_context(TLScontext); return (0); } /* * Apply session protocol restrictions. */ if (protomask != 0) SSL_set_options(TLScontext->con, TLS_SSL_OP_PROTOMASK(protomask)); #ifdef SSL_SECOP_PEER /* When authenticating the peer, use 80-bit plus OpenSSL security level */ if (TLS_MUST_MATCH(props->tls_level)) SSL_set_security_level(TLScontext->con, 1); #endif /* * XXX To avoid memory leaks we must always call SSL_SESSION_free() after * calling SSL_set_session(), regardless of whether or not the session * will be reused. */ if (TLScontext->cache_type) { session = load_clnt_session(TLScontext); if (session) { SSL_set_session(TLScontext->con, session); SSL_SESSION_free(session); /* 200411 */ } } #ifdef TLSEXT_MAXLEN_host_name if (TLS_DANE_BASED(props->tls_level) && strlen(props->host) <= TLSEXT_MAXLEN_host_name) { /* * With DANE sessions, send an SNI hint. We don't care whether the * server reports finding a matching certificate or not, so no * callback is required to process the server response. Our use of * SNI is limited to giving servers that are (mis)configured to use * SNI the best opportunity to find the certificate they promised via * the associated TLSA RRs. (Generally, server administrators should * avoid SNI, and there are no plans to support SNI in the Postfix * SMTP server). * * Since the hostname is DNSSEC-validated, it must be a DNS FQDN and * thererefore valid for use with SNI. Failure to set a valid SNI * hostname is a memory allocation error, and thus transient. Since * we must not cache the session if we failed to send the SNI name, * we have little choice but to abort. */ if (!SSL_set_tlsext_host_name(TLScontext->con, props->host)) { msg_warn("%s: error setting SNI hostname to: %s", props->namaddr, props->host); tls_free_context(TLScontext); return (0); } if (log_mask & TLS_LOG_DEBUG) msg_info("%s: SNI hostname: %s", props->namaddr, props->host); } #endif /* * Before really starting anything, try to seed the PRNG a little bit * more. */ tls_int_seed(); (void) tls_ext_seed(var_tls_daemon_rand_bytes); /* * Initialize the SSL connection to connect state. This should not be * necessary anymore since 0.9.3, but the call is still in the library * and maintaining compatibility never hurts. */ SSL_set_connect_state(TLScontext->con); /* * Connect the SSL connection with the network socket. */ if (SSL_set_fd(TLScontext->con, vstream_fileno(props->stream)) != 1) { msg_info("SSL_set_fd error to %s", props->namaddr); tls_print_errors(); uncache_session(app_ctx->ssl_ctx, TLScontext); tls_free_context(TLScontext); return (0); } /* * Turn on non-blocking I/O so that we can enforce timeouts on network * I/O. */ non_blocking(vstream_fileno(props->stream), NON_BLOCKING); /* * If the debug level selected is high enough, all of the data is dumped: * TLS_LOG_TLSPKTS will dump the SSL negotiation, TLS_LOG_ALLPKTS will * dump everything. * * We do have an SSL_set_fd() and now suddenly a BIO_ routine is called? * Well there is a BIO below the SSL routines that is automatically * created for us, so we can use it for debugging purposes. */ if (log_mask & TLS_LOG_TLSPKTS) BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); tls_dane_set_callback(app_ctx->ssl_ctx, TLScontext); /* * Start TLS negotiations. This process is a black box that invokes our * call-backs for certificate verification. * * Error handling: If the SSL handhake fails, we print out an error message * and remove all TLS state concerning this session. */ sts = tls_bio_connect(vstream_fileno(props->stream), props->timeout, TLScontext); if (sts <= 0) { if (ERR_peek_error() != 0) { msg_info("SSL_connect error to %s: %d", props->namaddr, sts); tls_print_errors(); } else if (errno != 0) { msg_info("SSL_connect error to %s: %m", props->namaddr); } else { msg_info("SSL_connect error to %s: lost connection", props->namaddr); } uncache_session(app_ctx->ssl_ctx, TLScontext); tls_free_context(TLScontext); return (0); } /* Turn off packet dump if only dumping the handshake */ if ((log_mask & TLS_LOG_ALLPKTS) == 0) BIO_set_callback(SSL_get_rbio(TLScontext->con), 0); /* * The caller may want to know if this session was reused or if a new * session was negotiated. */ TLScontext->session_reused = SSL_session_reused(TLScontext->con); if ((log_mask & TLS_LOG_CACHE) && TLScontext->session_reused) msg_info("%s: Reusing old session", TLScontext->namaddr); /* * Do peername verification if requested and extract useful information * from the certificate for later use. */ if ((peercert = SSL_get_peer_certificate(TLScontext->con)) != 0) { TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT; /* * Peer name or fingerprint verification as requested. * Unconditionally set peer_CN, issuer_CN and peer_cert_fprint. Check * fingerprint first, and avoid logging verified as untrusted in the * call to verify_extract_name(). */ verify_extract_print(TLScontext, peercert, props); verify_extract_name(TLScontext, peercert, props); if (TLScontext->log_mask & (TLS_LOG_CERTMATCH | TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) msg_info("%s: subject_CN=%s, issuer_CN=%s, " "fingerprint=%s, pkey_fingerprint=%s", props->namaddr, TLScontext->peer_CN, TLScontext->issuer_CN, TLScontext->peer_cert_fprint, TLScontext->peer_pkey_fprint); X509_free(peercert); } else { TLScontext->issuer_CN = mystrdup(""); TLScontext->peer_CN = mystrdup(""); TLScontext->peer_cert_fprint = mystrdup(""); TLScontext->peer_pkey_fprint = mystrdup(""); } /* * Finally, collect information about protocol and cipher for logging */ TLScontext->protocol = SSL_get_version(TLScontext->con); cipher = SSL_get_current_cipher(TLScontext->con); TLScontext->cipher_name = SSL_CIPHER_get_name(cipher); TLScontext->cipher_usebits = SSL_CIPHER_get_bits(cipher, &(TLScontext->cipher_algbits)); /* * The TLS engine is active. Switch to the tls_timed_read/write() * functions and make the TLScontext available to those functions. */ tls_stream_start(props->stream, TLScontext); /* * Fully secured only if trusted, matched and not insecure like halfdane. * Should perhaps also exclude "verify" (as opposed to "secure") here, * because that can be subject to insecure MX indirection, but that's * rather incompatible. Users have been warned. */ if (TLS_CERT_IS_PRESENT(TLScontext) && TLS_CERT_IS_TRUSTED(TLScontext) && TLS_CERT_IS_MATCHED(TLScontext) && !TLS_NEVER_SECURED(props->tls_level)) TLScontext->peer_status |= TLS_CERT_FLAG_SECURED; /* * All the key facts in a single log entry. */ if (log_mask & TLS_LOG_SUMMARY) msg_info("%s TLS connection established to %s: %s with cipher %s " "(%d/%d bits)", !TLS_CERT_IS_PRESENT(TLScontext) ? "Anonymous" : TLS_CERT_IS_SECURED(TLScontext) ? "Verified" : TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted", props->namaddr, TLScontext->protocol, TLScontext->cipher_name, TLScontext->cipher_usebits, TLScontext->cipher_algbits); tls_int_seed(); return (TLScontext); } #endif /* USE_TLS */