/*
* 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);
}
/*
* 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);
}
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);
}
/*
* 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);
}
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);
}
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);
}
/*
* 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));
}
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);
}