/*++ /* NAME /* tls_client /* SUMMARY /* client-side TLS engine /* SYNOPSIS /* #include /* /* 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; /* /* TLS_SESS_STATE *tls_client_post_connect(TLScontext, start_props) /* TLS_SESS_STATE *TLScontext; /* 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_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. /* EVENT_DRIVEN APPLICATIONS /* .ad /* .fi /* Event-driven programs manage multiple I/O channels. Such /* programs cannot use the synchronous VSTREAM-over-TLS /* implementation that the TLS library historically provides, /* including tls_client_stop() and the underlying tls_stream(3) /* and tls_bio_ops(3) routines. /* /* With the current TLS library implementation, this means /* that an event-driven application is responsible for calling /* and retrying SSL_connect(), SSL_read(), SSL_write() and /* SSL_shutdown(). /* /* To maintain control over TLS I/O, an event-driven client /* invokes tls_client_start() with a null VSTREAM argument and /* with an fd argument that specifies the I/O file descriptor. /* Then, tls_client_start() performs all the necessary /* preparations before the TLS handshake and returns a partially /* populated TLS context. The event-driven application is then /* responsible for invoking SSL_connect(), and if successful, /* for invoking tls_client_post_connect() to finish the work /* that was started by tls_client_start(). In case of unrecoverable /* failure, tls_client_post_connect() destroys the TLS context /* and returns a null pointer value. /* 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 /* /* Wietse Venema /* Google, Inc. /* 111 8th Avenue /* New York, NY 10011, USA /* /* Victor Duchovni /* Morgan Stanley /*--*/ /* System library. */ #include #ifdef USE_TLS #include #ifdef STRCASECMP_IN_STRINGS_H #include #endif /* Utility library. */ #include #include #include #include #include #include #include /* non-blocking */ #include /* Global library. */ #include /* TLS library. */ #include #define TLS_INTERNAL #include /* 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); } /* 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 verbose; verbose = TLScontext->log_mask & (TLS_LOG_CERTMATCH | TLS_LOG_VERBOSE | TLS_LOG_PEERCERT); /* * On exit both peer_CN and issuer_CN should be set. */ TLScontext->issuer_CN = tls_issuer_CN(peercert, TLScontext); TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext); /* * Is the certificate trust chain trusted and matched? Any required name * checks are now performed internally in OpenSSL. */ if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) { TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; if (TLScontext->must_fail) { msg_panic("%s: cert valid despite trust init failure", TLScontext->namaddr); } else if (TLS_MUST_MATCH(TLScontext->level)) { /* * Fully secured only if not insecure like half-dane. We use * TLS_CERT_FLAG_MATCHED to satisfy policy, but * TLS_CERT_FLAG_SECURED to log the effective security. * * Would ideally also exclude "verify" (as opposed to "secure") * here, because that can be subject to insecure MX indirection, * but that's rather incompatible (and not even the case with * explicitly chosen non-default match patterns). Users have * been warned. */ if (!TLS_NEVER_SECURED(TLScontext->level)) TLScontext->peer_status |= TLS_CERT_FLAG_SECURED; TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED; if (verbose) { const char *peername = SSL_get0_peername(TLScontext->con); if (peername) msg_info("%s: matched peername: %s", TLScontext->namaddr, peername); tls_dane_log(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_MATCHED(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); } } /* add_namechecks - tell OpenSSL what names to check */ static void add_namechecks(TLS_SESS_STATE *TLScontext, const TLS_CLIENT_START_PROPS *props) { SSL *ssl = TLScontext->con; int namechecks_count = 0; int i; /* RFC6125: No part-label 'foo*bar.example.com' wildcards for SMTP */ SSL_set_hostflags(ssl, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS); for (i = 0; i < props->matchargv->argc; ++i) { const char *name = props->matchargv->argv[i]; const char *aname; int match_subdomain = 0; if (strcasecmp(name, "nexthop") == 0) { name = props->nexthop; } else if (strcasecmp(name, "dot-nexthop") == 0) { name = props->nexthop; match_subdomain = 1; } else if (strcasecmp(name, "hostname") == 0) { name = props->host; } else { if (*name == '.') { if (*++name == 0) { msg_warn("%s: ignoring invalid match name: \".\"", TLScontext->namaddr); continue; } match_subdomain = 1; } #ifndef NO_EAI else { /* * 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. */ unsigned char *cp = (unsigned char *) name; 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 (name[3]) { name = name + 3; match_subdomain = 1; } } } #endif } /* * 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. */ #ifndef NO_EAI if (!allascii(name) && (aname = midna_domain_to_ascii(name)) != 0) { if (msg_verbose) msg_info("%s asciified to %s", name, aname); name = aname; } #endif if (!match_subdomain) { if (SSL_add1_host(ssl, name)) ++namechecks_count; else msg_warn("%s: error loading match name: \"%s\"", TLScontext->namaddr, name); } else { char *dot_name = concatenate(".", name, (char *) 0); if (SSL_add1_host(ssl, dot_name)) ++namechecks_count; else msg_warn("%s: error loading match name: \"%s\"", TLScontext->namaddr, dot_name); myfree(dot_name); } } /* * If we failed to add any names, OpenSSL will perform no namechecks, so * we set the "must_fail" bit to avoid verification false-positives. */ if (namechecks_count == 0) { msg_warn("%s: could not configure peer name checks", TLScontext->namaddr); TLScontext->must_fail = 1; } } /* tls_auth_enable - set up TLS authentication */ static int tls_auth_enable(TLS_SESS_STATE *TLScontext, const TLS_CLIENT_START_PROPS *props) { const char *sni = 0; if (props->sni && *props->sni) { #ifndef NO_EAI const char *aname; #endif /* * MTA-STS policy plugin compatibility: with servername=hostname, * Postfix must send the MX hostname (not CNAME expanded). */ if (strcmp(props->sni, "hostname") == 0) sni = props->host; else if (strcmp(props->sni, "nexthop") == 0) sni = props->nexthop; else sni = props->sni; /* * The SSL_set_tlsext_host_name() documentation does not promise that * every implementation will convert U-label form to A-label form. */ #ifndef NO_EAI if (!allascii(sni) && (aname = midna_domain_to_ascii(sni)) != 0) { if (msg_verbose) msg_info("%s asciified to %s", sni, aname); sni = aname; } #endif } switch (TLScontext->level) { case TLS_LEV_HALF_DANE: case TLS_LEV_DANE: case TLS_LEV_DANE_ONLY: /* * 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 make use of SNI the best * opportunity to find the certificate they promised via the * associated TLSA RRs. * * Since the hostname is DNSSEC-validated, it must be a DNS FQDN and * therefore valid for use with SNI. */ if (SSL_dane_enable(TLScontext->con, 0) <= 0) { msg_warn("%s: error enabling DANE-based certificate validation", TLScontext->namaddr); tls_print_errors(); return (0); } /* RFC7672 Section 3.1.1 specifies no name checks for DANE-EE(3) */ SSL_dane_set_flags(TLScontext->con, DANE_FLAG_NO_DANE_EE_NAMECHECKS); /* Per RFC7672 the SNI name is the TLSA base domain */ sni = props->dane->base_domain; add_namechecks(TLScontext, props); break; case TLS_LEV_FPRINT: /* Synthetic DANE for fingerprint security */ if (SSL_dane_enable(TLScontext->con, 0) <= 0) { msg_warn("%s: error enabling fingerprint certificate validation", props->namaddr); tls_print_errors(); return (0); } SSL_dane_set_flags(TLScontext->con, DANE_FLAG_NO_DANE_EE_NAMECHECKS); break; case TLS_LEV_SECURE: case TLS_LEV_VERIFY: if (TLScontext->dane != 0 && TLScontext->dane->tlsa != 0) { /* Synthetic DANE for per-destination trust-anchors */ if (SSL_dane_enable(TLScontext->con, NULL) <= 0) { msg_warn("%s: error configuring local trust anchors", props->namaddr); tls_print_errors(); return (0); } } add_namechecks(TLScontext, props); break; default: break; } if (sni) { if (strlen(sni) > TLSEXT_MAXLEN_host_name) { msg_warn("%s: ignoring too long SNI hostname: %.100s", props->namaddr, sni); return (0); } /* * 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, sni)) { msg_warn("%s: error setting SNI hostname to: %s", props->namaddr, sni); return (0); } /* * The saved value is not presently used client-side, but could later * be logged if acked by the server (requires new client-side * callback to detect the ack). For now this just maintains symmetry * with the server code, where do record the received SNI for * logging. */ TLScontext->peer_sni = mystrdup(sni); if (TLScontext->log_mask & TLS_LOG_DEBUG) msg_info("%s: SNI hostname: %s", props->namaddr, sni); } return (1); } /* tls_client_init - initialize client-side TLS engine */ TLS_APPL_STATE *tls_client_init(const TLS_CLIENT_INIT_PROPS *props) { SSL_CTX *client_ctx; TLS_APPL_STATE *app_ctx; const EVP_MD *fpt_alg; long off = 0; int cachable; int scache_timeout; 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(); /* * Initialize the OpenSSL library, possibly loading its configuration * file. */ if (tls_library_init() == 0) return (0); /* * 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 ((fpt_alg = tls_validate_digest(props->mdalg)) == 0) { 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); /* * This is a prerequisite for enabling DANE support in OpenSSL, but not a * commitment to use DANE, thus suitable for both DANE and non-DANE TLS * connections. Indeed we need this not just for DANE, but aslo for * fingerprint and "tafile" support. Since it just allocates memory, it * should never fail except when we're likely to fail anyway. Rather * than try to run with crippled TLS support, just give up using TLS. */ if (SSL_CTX_dane_enable(client_ctx) <= 0) { msg_warn("OpenSSL DANE initialization failed: disabling TLS support"); tls_print_errors(); return (0); } tls_dane_digest_init(client_ctx, fpt_alg); /* * Presently we use TLS only with SMTP where truncation attacks are not * possible as a result of application framing. If we ever use TLS in * some other application protocol where truncation could be relevant, * we'd need to disable truncation detection conditionally, or explicitly * clear the option in that code path. */ off |= SSL_OP_IGNORE_UNEXPECTED_EOF; /* * 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->chain_files, 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); } /* * 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, var_tls_eecdh_auto); /* * 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, 0, 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); } /* * 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; int min_proto; int max_proto; const char *cipher_list; SSL_SESSION *session = 0; TLS_SESS_STATE *TLScontext; TLS_APPL_STATE *app_ctx = props->ctx; 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_MATCH(props->tls_level)) 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_proto_mask_lims(props->protocols, &min_proto, &max_proto); 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); } /* * Though RFC7672 set the floor at SSLv3, we really can and should * require TLS 1.0, since e.g. we send SNI, which is a TLS 1.0 extension. * No DANE domains have been observed to support only SSLv3. * * XXX: Would be nice to make that TLS 1.2 at some point. Users can choose * to exclude TLS 1.0 and TLS 1.1 if they find they don't run into any * problems doing that. */ if (TLS_DANE_BASED(props->tls_level)) protomask |= TLS_PROTOCOL_SSLv2 | TLS_PROTOCOL_SSLv3; /* * 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->level = props->tls_level; 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); } /* * 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(TLScontext, props->cipher_grade, props->cipher_exclusions); if (cipher_list == 0) { /* already warned */ tls_free_context(TLScontext); return (0); } if (log_mask & TLS_LOG_VERBOSE) msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); TLScontext->stream = props->stream; TLScontext->mdalg = props->mdalg; /* Alias DANE digest info from props */ TLScontext->dane = props->dane; 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); } #define CARP_VERSION(which) do { \ if (which##_proto != 0) \ msg_warn("%s: error setting %simum TLS version to: 0x%04x", \ TLScontext->namaddr, #which, which##_proto); \ else \ msg_warn("%s: error clearing %simum TLS version", \ TLScontext->namaddr, #which); \ } while (0) /* * Apply session protocol restrictions. */ if (protomask != 0) SSL_set_options(TLScontext->con, TLS_SSL_OP_PROTOMASK(protomask)); if (!SSL_set_min_proto_version(TLScontext->con, min_proto)) CARP_VERSION(min); if (!SSL_set_max_proto_version(TLScontext->con, max_proto)) CARP_VERSION(max); /* * When applicable, configure DNS-based or synthetic (fingerprint or * local trust anchor) DANE authentication, enable an appropriate SNI * name and peer name matching. * * NOTE, this can change the effective security level, and needs to happen * early. */ if (!tls_auth_enable(TLScontext, props)) { tls_free_context(TLScontext); return (0); } /* * Try to convey the configured TLSA records for this connection to the * OpenSSL library. If none are "usable", we'll fall back to "encrypt" * when authentication is not mandatory, otherwise we must arrange to * ensure authentication failure. */ if (TLScontext->dane && TLScontext->dane->tlsa) { int usable = tls_dane_enable(TLScontext); int must_fail = usable <= 0; if (usable == 0) { switch (TLScontext->level) { case TLS_LEV_HALF_DANE: case TLS_LEV_DANE: msg_warn("%s: all TLSA records unusable, fallback to " "unauthenticated TLS", TLScontext->namaddr); must_fail = 0; TLScontext->level = TLS_LEV_ENCRYPT; break; case TLS_LEV_FPRINT: msg_warn("%s: all fingerprints unusable", TLScontext->namaddr); break; case TLS_LEV_DANE_ONLY: msg_warn("%s: all TLSA records unusable", TLScontext->namaddr); break; case TLS_LEV_SECURE: case TLS_LEV_VERIFY: msg_warn("%s: all trust anchors unusable", TLScontext->namaddr); break; } } TLScontext->must_fail |= must_fail; } /* * We compute the policy digest after we compute the SNI name in * tls_auth_enable() and possibly update the TLScontext security level. * * 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. */ TLScontext->serverid = tls_serverid_digest(TLScontext, props, cipher_list); /* * When authenticating the peer, use 80-bit plus OpenSSL security level * * XXX: We should perhaps use security level 1 also for mandatory * encryption, with only "may" tolerating weaker algorithms. But that * could mean no TLS 1.0 with OpenSSL >= 3.0 and encrypt, unless I get my * patch in on time to conditionally re-enable SHA1 at security level 1, * and we add code to make it so. * * That said, with "encrypt", we could reasonably require TLS 1.2? */ if (TLS_MUST_MATCH(TLScontext->level)) SSL_set_security_level(TLScontext->con, 1); /* * 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 */ } } /* * 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); /* * Connect the SSL connection with the network socket. */ if (SSL_set_fd(TLScontext->con, props->stream == 0 ? props->fd : 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); } /* * 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) tls_set_bio_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); /* * If we don't trigger the handshake in the library, leave control over * SSL_connect/read/write/etc with the application. */ if (props->stream == 0) return (TLScontext); /* * Turn on non-blocking I/O so that we can enforce timeouts on network * I/O. */ non_blocking(vstream_fileno(props->stream), NON_BLOCKING); /* * Start TLS negotiations. This process is a black box that invokes our * call-backs for certificate verification. * * Error handling: If the SSL handshake 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); } return (tls_client_post_connect(TLScontext, props)); } /* tls_client_post_connect - post-handshake processing */ TLS_SESS_STATE *tls_client_post_connect(TLS_SESS_STATE *TLScontext, const TLS_CLIENT_START_PROPS *props) { const SSL_CIPHER *cipher; X509 *peercert; /* Turn off packet dump if only dumping the handshake */ if ((TLScontext->log_mask & TLS_LOG_ALLPKTS) == 0) tls_set_bio_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 ((TLScontext->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 = TLS_PEEK_PEER_CERT(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(). */ TLScontext->peer_cert_fprint = tls_cert_fprint(peercert, props->mdalg); TLScontext->peer_pkey_fprint = tls_pkey_fprint(peercert, props->mdalg); 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); } 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. */ if (TLScontext->stream != 0) tls_stream_start(props->stream, TLScontext); /* * With the handshake done, extract TLS 1.3 signature metadata. */ tls_get_signature_params(TLScontext); if (TLScontext->log_mask & TLS_LOG_SUMMARY) tls_log_summary(TLS_ROLE_CLIENT, TLS_USAGE_NEW, TLScontext); tls_int_seed(); return (TLScontext); } #endif /* USE_TLS */