Exemplo n.º 1
0
 /*
  * 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));

    /*
     * 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);

    /*
     * 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_MATCHED(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);
}
Exemplo n.º 2
0
 /*
  * 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;
    const SSL_CIPHER *cipher;
    X509   *peercert;
    TLS_SESS_STATE *TLScontext;
    TLS_APPL_STATE *app_ctx = props->ctx;
    VSTRING *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.
     */
    if (props->tls_level >= TLS_LEV_VERIFY)
	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
     * 
     * The cipherlist will be applied to the global SSL context, where it can be
     * repeatedly reset if necessary, but the protocol restrictions will be
     * is applied to the SSL connection, because protocol restrictions in the
     * global context cannot be cleared.
     */

    /*
     * 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.
     * 
     * Still, we salt the session lookup key with the protocol list, so that
     * sessions found in the cache are always acceptable.
     */
    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);
    }
    myserverid = vstring_alloc(100);
    vstring_sprintf_append(myserverid, "%s&p=%d", props->serverid, protomask);

    /*
     * Per session cipher selection for sessions with mandatory encryption
     * 
     * 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.
     */
    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));
	vstring_free(myserverid);
	return (0);
    }
    if (log_mask & TLS_LOG_VERBOSE)
	msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list);
    vstring_sprintf_append(myserverid, "&c=%s", cipher_list);

    /*
     * Finally, salt the session key with the OpenSSL library version,
     * (run-time, rather than compile-time, just in case that matters).
     */
    vstring_sprintf_append(myserverid, "&l=%ld", (long) SSLeay());

    /*
     * 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 = vstring_export(myserverid);
    TLScontext->stream = props->stream;

    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,
		   ((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L)
	     | ((protomask & TLS_PROTOCOL_TLSv1_1) ? SSL_OP_NO_TLSv1_1 : 0L)
	     | ((protomask & TLS_PROTOCOL_TLSv1_2) ? SSL_OP_NO_TLSv1_2 : 0L)
		 | ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L)
	       | ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L));

    /*
     * 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 */
#if (OPENSSL_VERSION_NUMBER < 0x00906011L) || (OPENSSL_VERSION_NUMBER == 0x00907000L)

	    /*
	     * Ugly Hack: OpenSSL before 0.9.6a does not store the verify
	     * result in sessions for the client side. We modify the session
	     * directly which is version specific, but this bug is version
	     * specific, too.
	     * 
	     * READ: 0-09-06-01-1 = 0-9-6-a-beta1: all versions before beta1
	     * have this bug, it has been fixed during development of 0.9.6a.
	     * The development version of 0.9.7 can have this bug, too. It
	     * has been fixed on 2000/11/29.
	     */
	    SSL_set_verify_result(TLScontext->con, session->verify_result);
#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);

    /*
     * 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_fingerprint.
	 */
	verify_extract_name(TLScontext, peercert, props);
	verify_extract_print(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_fingerprint,
		     TLScontext->peer_pkey_fprint);
	X509_free(peercert);
    } else {
	TLScontext->issuer_CN = mystrdup("");
	TLScontext->peer_CN = mystrdup("");
	TLScontext->peer_fingerprint = 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);

    /*
     * 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_MATCHED(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);
}
Exemplo n.º 3
0
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();

    /*
     * 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();

    /*
     * 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();
    if ((client_ctx = SSL_CTX_new(SSLv23_client_method())) == 0) {
	msg_warn("cannot allocate client SSL_CTX: disabling TLS support");
	tls_print_errors();
	return (0);
    }

    /*
     * 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);
    }

    /*
     * 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);

    /*
     * 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);
}
Exemplo n.º 4
0
/*
 * 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)
{
    const   char *myname = "tls_client_start";
    int     sts;
    int     protomask;
    const char *cipher_list;
    SSL_SESSION *session;
    SSL_CIPHER *cipher;
    X509   *peercert;
    TLS_SESS_STATE *TLScontext;
    TLS_APPL_STATE *app_ctx = props->ctx;
    ACL_VSTRING *myserverid;

    if (props->log_level >= 1)
	acl_msg_info("%s(%d): setting up TLS connection to %s",
		myname, __LINE__, props->namaddr);

    /*
     * First make sure we have valid protocol and cipher parameters
     * 
     * The cipherlist will be applied to the global SSL context, where it can be
     * repeatedly reset if necessary, but the protocol restrictions will be
     * is applied to the SSL connection, because protocol restrictions in the
     * global context cannot be cleared.
     */

    /*
     * 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.
     * 
     * Still, we salt the session lookup key with the protocol list, so that
     * sessions found in the cache are always acceptable.
     */
    protomask = tls_protocol_mask(props->protocols);
    if (protomask == TLS_PROTOCOL_INVALID) {
	/* tls_protocol_mask() logs no warning. */
	acl_msg_warn("%s(%d): nameaddr: %s: Invalid TLS protocol list \"%s\": aborting TLS session",
		myname, __LINE__, props->namaddr, props->protocols);
	return (0);
    }
    myserverid = acl_vstring_alloc(100);
    acl_vstring_sprintf_append(myserverid, "%s&p=%d", props->serverid, protomask);

    /*
     * Per session cipher selection for sessions with mandatory encryption
     * 
     * 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.
     */
    cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade,
	    props->cipher_exclusions);
    if (cipher_list == 0) {
	acl_msg_warn("%s(%d): %s: %s: aborting TLS session",
		myname, __LINE__, props->namaddr, acl_vstring_str(app_ctx->why));
	acl_vstring_free(myserverid);
	return (0);
    }
    if (props->log_level >= 2)
	acl_msg_info("%s(%d): %s: TLS cipher list \"%s\"",
		myname, __LINE__, props->namaddr, cipher_list);
    acl_vstring_sprintf_append(myserverid, "&c=%s", 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(props->log_level, props->namaddr);
    TLScontext->cache_type = app_ctx->cache_type;

    TLScontext->serverid = acl_vstring_export(myserverid);

    if ((TLScontext->con = SSL_new(app_ctx->ssl_ctx)) == NULL) {
	acl_msg_warn("%s(%d): Could not allocate 'TLScontext->con' with SSL_new()",
		myname, __LINE__);
	tls_print_errors();
	tls_free_context(TLScontext);
	return (0);
    }
    if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) {
	acl_msg_warn("%s(%d): Could not set application data for 'TLScontext->con'",
		myname, __LINE__);
	tls_print_errors();
	tls_free_context(TLScontext);
	return (0);
    }

    /*
     * Apply session protocol restrictions.
     */
    if (protomask != 0)
	SSL_set_options(TLScontext->con,
		((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L)
		| ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L)
		| ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L));

    /*
     * The TLS connection is realized by a BIO_pair, so obtain the pair.
     * 
     * XXX There is no need to make internal_bio a member of the TLScontext
     * structure. It will be attached to TLScontext->con, and destroyed along
     * with it. The network_bio, however, needs to be freed explicitly.
     */
    if (!BIO_new_bio_pair(&TLScontext->internal_bio, TLS_BIO_BUFSIZE,
		&TLScontext->network_bio, TLS_BIO_BUFSIZE)) {
	acl_msg_warn("%s(%d): Could not obtain BIO_pair", myname, __LINE__);
	tls_print_errors();
	tls_free_context(TLScontext);
	return (0);
    }

    /*
     * 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 */
#if (OPENSSL_VERSION_NUMBER < 0x00906011L) || (OPENSSL_VERSION_NUMBER == 0x00907000L)

	    /*
	     * Ugly Hack: OpenSSL before 0.9.6a does not store the verify
	     * result in sessions for the client side. We modify the session
	     * directly which is version specific, but this bug is version
	     * specific, too.
	     * 
	     * READ: 0-09-06-01-1 = 0-9-6-a-beta1: all versions before beta1
	     * have this bug, it has been fixed during development of 0.9.6a.
	     * The development version of 0.9.7 can have this bug, too. It
	     * has been fixed on 2000/11/29.
	     */
	    SSL_set_verify_result(TLScontext->con, session->verify_result);
#endif
	}
    }

    /*
     * Before really starting anything, try to seed the PRNG a little bit
     * more.
     */
    tls_int_seed();
    if (var_tls_daemon_rand_bytes > 0)
	(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 Postfix side of the BIO-pair for
     * reading and writing.
     */
    SSL_set_bio(TLScontext->con, TLScontext->internal_bio, TLScontext->internal_bio);

    /*
     * If the debug level selected is high enough, all of the data is dumped:
     * 3 will dump the SSL negotiation, 4 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 (props->log_level >= 3)
	BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb);

    /*
     * 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(ACL_VSTREAM_SOCK(props->stream), props->timeout,
	    TLScontext);
    if (sts <= 0) {
	acl_msg_info("%s(%d): SSL_connect error to %s: %d",
		myname, __LINE__, props->namaddr, sts);
	tls_print_errors();
	uncache_session(app_ctx->ssl_ctx, TLScontext);
	tls_free_context(TLScontext);
	return (0);
    }
    /* Only log_level==4 dumps everything */
    if (props->log_level < 4)
	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 (props->log_level >= 2 && TLScontext->session_reused)
	acl_msg_info("%s(%d): %s: Reusing old session",
		myname, __LINE__, 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_fingerprint.
	 */
	verify_extract_name(TLScontext, peercert, props);
	verify_extract_print(TLScontext, peercert, props);
	X509_free(peercert);
    } else {
	TLScontext->issuer_CN = acl_mystrdup("");
	TLScontext->peer_CN = acl_mystrdup("");
	TLScontext->peer_fingerprint = acl_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);

    /*
     * All the key facts in a single log entry.
     */
    if (props->log_level >= 1)
	acl_msg_info("%s(%d): %s TLS connection established to %s: %s with cipher %s "
		"(%d/%d bits)", myname, __LINE__,
		TLS_CERT_IS_MATCHED(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);
}
Exemplo n.º 5
0
int tls_client_setup(const TLS_CLIENT_INIT_PROPS *props)
{
    const char *myname = "tls_client_init";
    const EVP_MD *md_alg;
    unsigned int md_len;
    static int init_done = 0;

    if (init_done) {
	acl_msg_warn("%s(%d): called once before", myname, __LINE__);
	return (0);
    }

    if (props->log_level >= 2)
	acl_msg_info("%s: initializing the client-side TLS engine", myname);

    /*
     * Detect mismatch between compile-time headers and run-time library.
     */
    tls_check_version();

    /*
     * 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();

    /*
     * 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) {
	    acl_msg_warn("%s(%d): Cannot allocate SSL application data index: "
		    "disabling TLS support", myname, __LINE__);
	    return (-1);
	}
    }

    /*
     * If the administrator specifies an unsupported digest algorithm, fail
     * now, rather than in the middle of a TLS handshake.
     */
    if ((md_alg = EVP_get_digestbyname(props->fpt_dgst)) == 0) {
	acl_msg_warn("%s(%d): Digest algorithm \"%s\" not found: disabling TLS support",
		myname, __LINE__, props->fpt_dgst);
	return (-1);
    }

    /*
     * Sanity check: Newer shared libraries may use larger digests.
     */
    if ((md_len = EVP_MD_size(md_alg)) > EVP_MAX_MD_SIZE) {
	acl_msg_warn("%s(%d): Digest algorithm \"%s\" output size %u too large:"
		" disabling TLS support", myname, __LINE__, props->fpt_dgst, md_len);
	return (-1);
    }

    /*
     * Initialize the PRNG (Pseudo Random Number Generator) with some seed
     * from external and internal sources. Don't enable TLS without some real
     * entropy.
     */
    if (var_tls_daemon_rand_bytes > 0 && tls_ext_seed(var_tls_daemon_rand_bytes) < 0) {
	acl_msg_warn("%s(%d): no entropy for TLS key generation: disabling TLS support",
		myname, __LINE__);
	return (-1);
    }
    tls_int_seed();

    return (0);
}
Exemplo n.º 6
0
TLS_SESS_STATE *tls_server_post_accept(TLS_SESS_STATE *TLScontext)
{
    const SSL_CIPHER *cipher;
    X509   *peer;
    char    buf[CCERT_BUFSIZ];

    /* Only loglevel==4 dumps everything */
    if (TLScontext->log_level < 4)
	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 (TLScontext->log_level >= 2 && TLScontext->session_reused)
	msg_info("%s: Reusing old session", TLScontext->namaddr);

    /*
     * Let's see whether a peer certificate is available and what is the
     * actual information. We want to save it for later use.
     */
    peer = SSL_get_peer_certificate(TLScontext->con);
    if (peer != NULL) {
	TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT;
	if (SSL_get_verify_result(TLScontext->con) == X509_V_OK)
	    TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED;

	if (TLScontext->log_level >= 2) {
	    X509_NAME_oneline(X509_get_subject_name(peer),
			      buf, sizeof(buf));
	    msg_info("subject=%s", buf);
	    X509_NAME_oneline(X509_get_issuer_name(peer),
			      buf, sizeof(buf));
	    msg_info("issuer=%s", buf);
	}
	TLScontext->peer_CN = tls_peer_CN(peer, TLScontext);
	TLScontext->issuer_CN = tls_issuer_CN(peer, TLScontext);
	TLScontext->peer_fingerprint =
	    tls_fingerprint(peer, TLScontext->fpt_dgst);

	if (TLScontext->log_level >= 1) {
	    msg_info("%s: %s: subject_CN=%s, issuer=%s, fingerprint=%s",
		     TLScontext->namaddr,
		  TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted",
		     TLScontext->peer_CN, TLScontext->issuer_CN,
		     TLScontext->peer_fingerprint);
	}
	X509_free(peer);
    } else {
	TLScontext->peer_CN = mystrdup("");
	TLScontext->issuer_CN = mystrdup("");
	TLScontext->peer_fingerprint = 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));

    /*
     * If the library triggered the SSL handshake, switch to the
     * tls_timed_read/write() functions and make the TLScontext available to
     * those functions. Otherwise, leave control over SSL_read/write/etc.
     * with the application.
     */
    if (TLScontext->stream != 0)
	tls_stream_start(TLScontext->stream, TLScontext);

    /*
     * All the key facts in a single log entry.
     */
    if (TLScontext->log_level >= 1)
	msg_info("%s TLS connection established from %s: %s with cipher %s "
	      "(%d/%d bits)", !TLS_CERT_IS_PRESENT(TLScontext) ? "Anonymous"
		 : TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted",
	 TLScontext->namaddr, TLScontext->protocol, TLScontext->cipher_name,
		 TLScontext->cipher_usebits, TLScontext->cipher_algbits);

    tls_int_seed();

    return (TLScontext);
}
Exemplo n.º 7
0
 /*
  * This is the actual startup routine for a new connection. We expect that
  * the SMTP buffers are flushed and the "220 Ready to start TLS" was sent to
  * the client, so that we can immediately start the TLS handshake process.
  */
TLS_SESS_STATE *tls_server_start(const TLS_SERVER_START_PROPS *props)
{
    int     sts;
    TLS_SESS_STATE *TLScontext;
    const char *cipher_list;
    TLS_APPL_STATE *app_ctx = props->ctx;

    if (props->log_level >= 1)
	msg_info("setting up TLS connection from %s", props->namaddr);

    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 (props->log_level >= 2)
	msg_info("%s: TLS cipher list \"%s\"", props->namaddr, 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().
     */
    TLScontext = tls_alloc_sess_context(props->log_level, props->namaddr);
    TLScontext->cache_type = app_ctx->cache_type;

    TLScontext->serverid = mystrdup(props->serverid);
    TLScontext->am_server = 1;

    TLScontext->fpt_dgst = mystrdup(props->fpt_dgst);
    TLScontext->stream = props->stream;

    ERR_clear_error();
    if ((TLScontext->con = (SSL *) SSL_new(app_ctx->ssl_ctx)) == 0) {
	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);
    }

    /*
     * 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 accept 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_accept_state(TLScontext->con);

    /*
     * 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:
     * 3 will dump the SSL negotiation, 4 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 (props->log_level >= 3)
	BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb);

    /*
     * If we don't trigger the handshake in the library, leave control over
     * SSL_accept/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 session caching and 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_accept(vstream_fileno(props->stream), props->timeout,
			 TLScontext);
    if (sts <= 0) {
	msg_info("SSL_accept error from %s: %d", props->namaddr, sts);
	tls_print_errors();
	tls_free_context(TLScontext);
	return (0);
    }
    return (tls_server_post_accept(TLScontext));
}
Exemplo n.º 8
0
TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props)
{
    SSL_CTX *server_ctx;
    long    off = 0;
    int     verify_flags = SSL_VERIFY_NONE;
    int     cachable;
    int     protomask;
    TLS_APPL_STATE *app_ctx;
    const EVP_MD *md_alg;
    unsigned int md_len;

    if (props->log_level >= 2)
	msg_info("initializing the server-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 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();

    /*
     * First validate the protocols. If these are invalid, we can't continue.
     */
    protomask = tls_protocol_mask(props->protocols);
    if (protomask == TLS_PROTOCOL_INVALID) {
	/* tls_protocol_mask() logs no warning. */
	msg_warn("Invalid TLS protocol list \"%s\": disabling TLS support",
		 props->protocols);
	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);
	}
    }

    /*
     * Register SHA-2 digests, if implemented and not already registered.
     * Improves interoperability with clients and servers that prematurely
     * deploy SHA-2 certificates.
     */
#if defined(LN_sha256) && defined(NID_sha256) && !defined(OPENSSL_NO_SHA256)
    if (!EVP_get_digestbyname(LN_sha224))
	EVP_add_digest(EVP_sha224());
    if (!EVP_get_digestbyname(LN_sha256))
	EVP_add_digest(EVP_sha256());
#endif
#if defined(LN_sha512) && defined(NID_sha512) && !defined(OPENSSL_NO_SHA512)
    if (!EVP_get_digestbyname(LN_sha384))
	EVP_add_digest(EVP_sha384());
    if (!EVP_get_digestbyname(LN_sha512))
	EVP_add_digest(EVP_sha512());
#endif

    /*
     * If the administrator specifies an unsupported digest algorithm, fail
     * now, rather than in the middle of a TLS handshake.
     */
    if ((md_alg = EVP_get_digestbyname(props->fpt_dgst)) == 0) {
	msg_warn("Digest algorithm \"%s\" not found: disabling TLS support",
		 props->fpt_dgst);
	return (0);
    }

    /*
     * Sanity check: Newer shared libraries may use larger digests.
     */
    if ((md_len = EVP_MD_size(md_alg)) > EVP_MAX_MD_SIZE) {
	msg_warn("Digest algorithm \"%s\" output size %u too large:"
		 " disabling TLS support", props->fpt_dgst, md_len);
	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. Netscape communicator can still
     * communicate with SSLv2 servers, so it sends out a SSLv2 client hello.
     * To deal with it, our server must be SSLv2 aware (even if we don't like
     * SSLv2), so we need to have the SSLv23 server here. If we want to limit
     * the protocol level, we can add an option to not use SSLv2/v3/TLSv1
     * later.
     */
    ERR_clear_error();
    if ((server_ctx = SSL_CTX_new(SSLv23_server_method())) == 0) {
	msg_warn("cannot allocate server SSL_CTX: disabling TLS support");
	tls_print_errors();
	return (0);
    }

    /*
     * See the verify callback in tls_verify.c
     */
    SSL_CTX_set_verify_depth(server_ctx, props->verifydepth + 1);

    /*
     * Protocol work-arounds, OpenSSL version dependent.
     */
#ifdef SSL_OP_NO_TICKET
    off |= SSL_OP_NO_TICKET;
#endif
    off |= tls_bug_bits();
    SSL_CTX_set_options(server_ctx, off);

    /*
     * Global protocol selection.
     */
    if (protomask != 0)
	SSL_CTX_set_options(server_ctx,
		   ((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L)
	     | ((protomask & TLS_PROTOCOL_TLSv1_1) ? SSL_OP_NO_TLSv1_1 : 0L)
	     | ((protomask & TLS_PROTOCOL_TLSv1_2) ? SSL_OP_NO_TLSv1_2 : 0L)
		 | ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L)
	       | ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L));

#if OPENSSL_VERSION_NUMBER >= 0x0090700fL

    /*
     * Some sites may want to give the client less rope. On the other hand,
     * this could trigger inter-operability issues, the client should not
     * offer ciphers it implements poorly, but this hasn't stopped some
     * vendors from getting it wrong.
     * 
     * XXX: Given OpenSSL's security history, nobody should still be using
     * 0.9.7, let alone 0.9.6 or earlier. Warning added to TLS_README.html.
     */
    if (var_tls_preempt_clist)
	SSL_CTX_set_options(server_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
#endif

    /*
     * Set the call-back routine to debug handshake progress.
     */
    if (props->log_level >= 2)
	SSL_CTX_set_info_callback(server_ctx, tls_info_callback);

    /*
     * Load the CA public key certificates for both the server cert and for
     * the verification of client 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(server_ctx,
				    props->CAfile, props->CApath) < 0) {
	/* tls_set_ca_certificate_info() already logs a warning. */
	SSL_CTX_free(server_ctx);		/* 200411 */
	return (0);
    }

    /*
     * Load the server 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). A client
     * with RSA only (e.g. Netscape) will use the RSA certificate only. A
     * client with openssl-library will use RSA first if not especially
     * changed in the cipher setup.
     */
    if (tls_set_my_certificate_key_info(server_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(server_ctx);		/* 200411 */
	return (0);
    }

    /*
     * 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(server_ctx, tls_tmp_rsa_cb);

    /*
     * Diffie-Hellman key generation parameters can either be loaded from
     * files (preferred) or taken from compiled in values. First, set the
     * callback that will select the values when requested, then load the
     * (possibly) available DH parameters from files. We are generous with
     * the error handling, since we do have default values compiled in, so we
     * will not abort but just log the error message.
     */
    SSL_CTX_set_tmp_dh_callback(server_ctx, tls_tmp_dh_cb);
    if (*props->dh1024_param_file != 0)
	tls_set_dh_from_file(props->dh1024_param_file, 1024);
    if (*props->dh512_param_file != 0)
	tls_set_dh_from_file(props->dh512_param_file, 512);

    /*
     * Enable EECDH if available, errors are not fatal, we just keep going
     * with any remaining key-exchange algorithms.
     */
    (void) tls_set_eecdh_curve(server_ctx, props->eecdh_grade);

    /*
     * If we want to check client certificates, we have to indicate it in
     * advance. By now we only allow to decide on a global basis. If we want
     * to allow certificate based relaying, we must ask the client to provide
     * one with SSL_VERIFY_PEER. The client now can decide, whether it
     * provides one or not. We can enforce a failure of the negotiation with
     * SSL_VERIFY_FAIL_IF_NO_PEER_CERT, if we do not allow a connection
     * without one. In the "server hello" following the initialization by the
     * "client hello" the server must provide a list of CAs it is willing to
     * accept. Some clever clients will then select one from the list of
     * available certificates matching these CAs. Netscape Communicator will
     * present the list of certificates for selecting the one to be sent, or
     * it will issue a warning, if there is no certificate matching the
     * available CAs.
     * 
     * With regard to the purpose of the certificate for relaying, we might like
     * a later negotiation, maybe relaying would already be allowed for other
     * reasons, but this would involve severe changes in the internal postfix
     * logic, so we have to live with it the way it is.
     */
    if (props->ask_ccert)
	verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE;
    SSL_CTX_set_verify(server_ctx, verify_flags,
		       tls_verify_certificate_callback);
    if (*props->CAfile)
	SSL_CTX_set_client_CA_list(server_ctx,
				   SSL_load_client_CA_file(props->CAfile));

    /*
     * Initialize our own TLS server handle, before diving into the details
     * of TLS session cache management.
     */
    app_ctx = tls_alloc_app_context(server_ctx);

    /*
     * The session cache is implemented by the tlsmgr(8) server.
     * 
     * XXX 200502 Surprise: when OpenSSL purges an entry from the in-memory
     * cache, it also attempts to purge the entry from the on-disk cache.
     * This is undesirable, especially when we set the in-memory cache size
     * to 1. For this reason we don't allow OpenSSL to purge on-disk cache
     * entries, and leave it up to the tlsmgr process instead. Found by
     * Victor Duchovni.
     */

    if (tls_mgr_policy(props->cache_type, &cachable) != TLS_MGR_STAT_OK)
	cachable = 0;

    if (cachable || props->set_sessid) {

	/*
	 * Initialize the session cache.
	 * 
	 * With a large number of concurrent smtpd(8) processes, it is not a
	 * good idea to cache multiple large session objects in each process.
	 * We set the internal cache size to 1, and don't register a
	 * "remove_cb" so as to avoid deleting good sessions from the
	 * external cache prematurely (when the internal cache is full,
	 * OpenSSL removes sessions from the external cache also)!
	 * 
	 * 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).
	 * 
	 * Set a session id context to identify to what type of server process
	 * created a session. In our case, the context is simply the name of
	 * the mail system: "Postfix/TLS".
	 */
	SSL_CTX_sess_set_cache_size(server_ctx, 1);
	SSL_CTX_set_session_id_context(server_ctx,
				       (void *) &server_session_id_context,
				       sizeof(server_session_id_context));
	SSL_CTX_set_session_cache_mode(server_ctx,
				       SSL_SESS_CACHE_SERVER |
				       SSL_SESS_CACHE_NO_AUTO_CLEAR);
	if (cachable) {
	    app_ctx->cache_type = mystrdup(props->cache_type);

	    SSL_CTX_sess_set_get_cb(server_ctx, get_server_session_cb);
	    SSL_CTX_sess_set_new_cb(server_ctx, new_server_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.
	 */
	SSL_CTX_set_timeout(server_ctx, props->scache_timeout);
    } else {

	/*
	 * If we have no external cache, disable all caching. No use wasting
	 * server memory resources with sessions they are unlikely to be able
	 * to reuse.
	 */
	SSL_CTX_set_session_cache_mode(server_ctx, SSL_SESS_CACHE_OFF);
    }

    return (app_ctx);
}