static void tlsmgr_pre_init(char *unused_name, char **unused_argv)
{
char *path;
struct timeval tv;
TLSMGR_SCACHE *ent;
VSTRING *redirect;
HTABLE *dup_filter;
const char *dup_label;
/*
* If nothing else works then at least this will get us a few bits of
* entropy.
*
* XXX This is our first call into the OpenSSL library. We should find out
* if this can be moved to the post-jail initialization phase, without
* breaking compatibility with existing installations.
*/
GETTIMEOFDAY(&tv);
tv.tv_sec ^= getpid();
RAND_seed(&tv, sizeof(struct timeval));
/*
* Open the external entropy source. We will not be able to open it again
* after we are sent to chroot jail, so we keep it open. Errors are not
* fatal. The exchange file (see below) is the only entropy source that
* really matters in the long run.
*
* Security note: we open the entropy source while privileged, but we don't
* access the source until after we release privileges. This way, none of
* the OpenSSL code gets to execute while we are privileged.
*/
if (*var_tls_rand_source) {
/*
* Source is a random device.
*/
if (!strncmp(var_tls_rand_source, DEV_PREF, DEV_PREF_LEN)) {
path = DEV_PATH(var_tls_rand_source);
rand_source_dev = tls_prng_dev_open(path, TLS_MGR_TIMEOUT);
if (rand_source_dev == 0)
msg_warn("cannot open entropy device %s: %m", path);
}
/*
* Source is an EGD compatible socket.
*/
else if (!strncmp(var_tls_rand_source, EGD_PREF, EGD_PREF_LEN)) {
path = EGD_PATH(var_tls_rand_source);
rand_source_egd = tls_prng_egd_open(path, TLS_MGR_TIMEOUT);
if (rand_source_egd == 0)
msg_warn("cannot connect to EGD server %s: %m", path);
}
/*
* Source is regular file. We read this only once.
*/
else {
rand_source_file =
tls_prng_file_open(var_tls_rand_source, TLS_MGR_TIMEOUT);
}
} else {
msg_warn("no entropy source specified with parameter %s",
VAR_TLS_RAND_SOURCE);
msg_warn("encryption keys etc. may be predictable");
}
/*
* Security: don't create root-owned files that contain untrusted data.
* And don't create Postfix-owned files in root-owned directories,
* either. We want a correct relationship between (file/directory)
* ownership and (file/directory) content.
*/
SAVE_AND_SET_EUGID(var_owner_uid, var_owner_gid);
redirect = vstring_alloc(100);
/*
* Open the PRNG exchange file before going to jail, but don't use root
* privileges. Start the exchange file read/update pseudo thread after
* dropping privileges.
*/
if (*var_tls_rand_exch_name) {
rand_exch =
tls_prng_exch_open(data_redirect_file(redirect,
var_tls_rand_exch_name));
if (rand_exch == 0)
msg_fatal("cannot open PRNG exchange file %s: %m",
var_tls_rand_exch_name);
}
/*
* Open the session cache files and discard old information before going
* to jail, but don't use root privilege. Start the cache maintenance
* pseudo threads after dropping privileges.
*/
dup_filter = htable_create(sizeof(cache_table) / sizeof(cache_table[0]));
for (ent = cache_table; ent->cache_label; ++ent) {
/* Sanitize session timeout */
if (*ent->cache_timeout > 0) {
if (*ent->cache_timeout < TLS_SESSION_LIFEMIN)
*ent->cache_timeout = TLS_SESSION_LIFEMIN;
} else {
*ent->cache_timeout = 0;
}
/* External cache database disabled if timeout is non-positive */
if (*ent->cache_timeout > 0 && **ent->cache_db) {
if ((dup_label = htable_find(dup_filter, *ent->cache_db)) != 0)
msg_fatal("do not use the same TLS cache file %s for %s and %s",
*ent->cache_db, dup_label, ent->cache_label);
htable_enter(dup_filter, *ent->cache_db, ent->cache_label);
ent->cache_info =
tls_scache_open(data_redirect_map(redirect, *ent->cache_db),
ent->cache_label,
tls_log_mask(ent->log_param,
*ent->log_level) & TLS_LOG_CACHE,
*ent->cache_timeout);
}
}
htable_free(dup_filter, (void (*) (char *)) 0);
/*
* Clean up and restore privilege.
*/
vstring_free(redirect);
RESTORE_SAVED_EUGID();
}
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);
}
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 scache_timeout;
int ticketable = 0;
int protomask;
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 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);
}
}
/*
* 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. 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);
/*
* 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,
&scache_timeout) != TLS_MGR_STAT_OK)
scache_timeout = 0;
if (scache_timeout <= 0)
cachable = 0;
/*
* Protocol work-arounds, OpenSSL version dependent.
*/
off |= tls_bug_bits();
/*
* Add SSL_OP_NO_TICKET when the timeout is zero or library support is
* incomplete. The SSL_CTX_set_tlsext_ticket_key_cb feature was added in
* OpenSSL 0.9.8h, while SSL_NO_TICKET was added in 0.9.8f.
*/
#ifdef SSL_OP_NO_TICKET
#if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER >= 0x0090808fL
ticketable = (scache_timeout > 0 && !(off & SSL_OP_NO_TICKET));
if (ticketable)
SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb);
#endif
if (!ticketable)
off |= SSL_OP_NO_TICKET;
#endif
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));
/*
* 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);
/*
* Set the call-back routine to debug handshake progress.
*/
if (log_mask & TLS_LOG_DEBUG)
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 OpenSSL documentation, a temporary RSA key is needed when
* export ciphers are in use, because the certified key cannot be
* directly used.
*/
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, log_mask);
if (cachable || ticketable || 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. We set the session
* lifetime to twice the cache lifetime, which is also the issuing
* and retired key validation lifetime of session tickets keys. This
* way a session always lasts longer than the server's ability to
* decrypt its session ticket. Otherwise, a bug in OpenSSL may fail
* to re-issue tickets when sessions decrypt, but are expired.
*/
SSL_CTX_set_timeout(server_ctx, 2 * 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);
}