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-rw-r--r--src/tls/tls_client.c1251
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diff --git a/src/tls/tls_client.c b/src/tls/tls_client.c
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+/*++
+/* 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;
+/*
+/* 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 <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);
+}
+
+/* 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. With OpenSSL 3.0 and TLS 1.3, the same applies
+ * to the FFDHE groups which become part of a unified "groups" list.
+ */
+ tls_auto_groups(client_ctx, var_tls_eecdh_auto, var_tls_ffdhe_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 */