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acl/lib_tls/tls/tls_client.c

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/*++
* NAME
* tls_client
* SUMMARY
* client-side TLS engine
* SYNOPSIS
* #include <tls.h>
*
* TLS_APPL_STATE *tls_client_init(init_props)
* const TLS_CLIENT_INIT_PROPS *init_props;
*
* TLS_SESS_STATE *tls_client_start(start_props)
* const TLS_CLIENT_START_PROPS *start_props;
*
* void tls_client_stop(app_ctx, stream, failure, TLScontext)
* TLS_APPL_STATE *app_ctx;
* VSTREAM *stream;
* int failure;
* TLS_SESS_STATE *TLScontext;
* DESCRIPTION
* This module is the interface between Postfix TLS clients,
* the OpenSSL library and the TLS entropy and cache manager.
*
* The SMTP client will attempt to verify the server hostname
* against the names listed in the server certificate. When
* a hostname match is required, the verification fails
* on certificate verification or hostname mis-match errors.
* When no hostname match is required, hostname verification
* failures are logged but they do not affect the TLS handshake
* or the SMTP session.
*
* The rules for peer name wild-card matching differ between
* RFC 2818 (HTTP over TLS) and RFC 2830 (LDAP over TLS), while
* RFC RFC3207 (SMTP over TLS) does not specify a rule at all.
* Postfix uses a restrictive match algorithm. One asterisk
* ('*') is allowed as the left-most component of a wild-card
* certificate name; it matches the left-most component of
* the peer hostname.
*
* Another area where RFCs aren't always explicit is the
* handling of dNSNames in peer certificates. RFC 3207 (SMTP
* over TLS) does not mention dNSNames. Postfix follows the
* strict rules in RFC 2818 (HTTP over TLS), section 3.1: The
* Subject Alternative Name/dNSName has precedence over
* CommonName. If at least one dNSName is provided, Postfix
* verifies those against the peer hostname and ignores the
* CommonName, otherwise Postfix verifies the CommonName
* against the peer hostname.
*
* tls_client_init() is called once when the SMTP client
* initializes.
* Certificate details are also decided during this phase,
* so peer-specific certificate selection is not possible.
*
* tls_client_start() activates the TLS session over an established
* stream. We expect that network buffers are flushed and
* the TLS handshake can begin immediately.
*
* tls_client_stop() sends the "close notify" alert via
* SSL_shutdown() to the peer and resets all connection specific
* TLS data. As RFC2487 does not specify a separate shutdown, it
* is assumed that the underlying TCP connection is shut down
* immediately afterwards. Any further writes to the channel will
* be discarded, and any further reads will report end-of-file.
* If the failure flag is set, no SSL_shutdown() handshake is performed.
*
* Once the TLS connection is initiated, information about the TLS
* state is available via the TLScontext structure:
* .IP TLScontext->protocol
* the protocol name (SSLv2, SSLv3, TLSv1),
* .IP TLScontext->cipher_name
* the cipher name (e.g. RC4/MD5),
* .IP TLScontext->cipher_usebits
* the number of bits actually used (e.g. 40),
* .IP TLScontext->cipher_algbits
* the number of bits the algorithm is based on (e.g. 128).
* .PP
* The last two values may differ from each other when export-strength
* encryption is used.
*
* If the peer offered a certificate, part of the certificate data are
* available as:
* .IP TLScontext->peer_status
* A bitmask field that records the status of the peer certificate
* verification. This consists of one or more of
* TLS_CERT_FLAG_PRESENT, TLS_CERT_FLAG_ALTNAME, TLS_CERT_FLAG_TRUSTED
* and TLS_CERT_FLAG_MATCHED.
* .IP TLScontext->peer_CN
* Extracted CommonName of the peer, or zero-length string if the
* information could not be extracted.
* .IP TLScontext->issuer_CN
* Extracted CommonName of the issuer, or zero-length string if the
* information could not be extracted.
* .IP TLScontext->peer_fingerprint
* At the fingerprint security level, if the peer presented a certificate
* the fingerprint of the certificate.
* .PP
* If no peer certificate is presented the peer_status is set to 0.
* LICENSE
* .ad
* .fi
* This software is free. You can do with it whatever you want.
* The original author kindly requests that you acknowledge
* the use of his software.
* AUTHOR(S)
* Originally written by:
* Lutz Jaenicke
* BTU Cottbus
* Allgemeine Elektrotechnik
* Universitaetsplatz 3-4
* D-03044 Cottbus, Germany
*
* Updated by:
* Wietse Venema
* IBM T.J. Watson Research
* P.O. Box 704
* Yorktown Heights, NY 10598, USA
*
* Victor Duchovni
* Morgan Stanley
*--*/
#include "StdAfx.h"
#ifdef USE_TLS
#include <string.h>
#ifdef STRCASECMP_IN_STRINGS_H
#include <strings.h>
#endif
/* Global library. */
#include "tls_params.h"
/* TLS library. */
#include "tls_mgr.h"
#include "tls.h"
#include "tls_private.h"
/* Application-specific. */
#define STR acl_vstring_str
#define LEN ACL_VSTRING_LEN
/* load_clnt_session - load session from client cache (non-callback) */
static SSL_SESSION *load_clnt_session(TLS_SESS_STATE *TLScontext)
{
const char *myname = "load_clnt_session";
SSL_SESSION *session = 0;
ACL_VSTRING *session_data = acl_vstring_alloc(2048);
/*
* Prepare the query.
*/
if (TLScontext->log_level >= 2)
acl_msg_info("looking for session %s in %s cache",
TLScontext->serverid, TLScontext->cache_type);
/*
* We only get here if the cache_type is not empty. This code is not
* called unless caching is enabled and the cache_type is stored in the
* server SSL context.
*/
if (TLScontext->cache_type == 0)
acl_msg_panic("%s: null client session cache type in session lookup", myname);
/*
* Look up and activate the SSL_SESSION object. Errors are non-fatal,
* since caching is only an optimization.
*/
if (tls_mgr_lookup(TLScontext->cache_type, TLScontext->serverid,
session_data) == TLS_MGR_STAT_OK) {
session = tls_session_activate(STR(session_data), (int) LEN(session_data));
if (session) {
if (TLScontext->log_level >= 2)
acl_msg_info("reloaded session %s from %s cache",
TLScontext->serverid, TLScontext->cache_type);
}
}
/*
* Clean up.
*/
acl_vstring_free(session_data);
return (session);
}
/* new_client_session_cb - name new session and save it to client cache */
static int new_client_session_cb(SSL *ssl, SSL_SESSION *session)
{
const char *myname = "new_client_session_cb";
TLS_SESS_STATE *TLScontext;
ACL_VSTRING *session_data;
/*
* The cache name (if caching is enabled in tlsmgr(8)) and the cache ID
* string for this session are stored in the TLScontext. It cannot be
* null at this point.
*/
if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0)
acl_msg_panic("%s: null TLScontext in new session callback", myname);
/*
* We only get here if the cache_type is not empty. This callback is not
* set unless caching is enabled and the cache_type is stored in the
* server SSL context.
*/
if (TLScontext->cache_type == 0)
acl_msg_panic("%s: null session cache type in new session callback", myname);
if (TLScontext->log_level >= 2)
acl_msg_info("save session %s to %s cache", TLScontext->serverid, TLScontext->cache_type);
#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.
*/
session->verify_result = SSL_get_verify_result(TLScontext->con);
#endif
/*
* Passivate and save the session object. Errors are non-fatal, since
* caching is only an optimization.
*/
if ((session_data = tls_session_passivate(session)) != 0) {
tls_mgr_update(TLScontext->cache_type, TLScontext->serverid,
STR(session_data), (int) LEN(session_data));
acl_vstring_free(session_data);
}
/*
* Clean up.
*/
SSL_SESSION_free(session); /* 200502 */
return (1);
}
/* uncache_session - remove session from the external cache */
static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext)
{
SSL_SESSION *session = SSL_get_session(TLScontext->con);
SSL_CTX_remove_session(ctx, session);
if (TLScontext->cache_type == 0 || TLScontext->serverid == 0)
return;
if (TLScontext->log_level >= 2)
acl_msg_info("remove session %s from client cache", TLScontext->serverid);
tls_mgr_delete(TLScontext->cache_type, TLScontext->serverid);
}
/* tls_client_init - initialize client-side TLS engine */
void tls_client_init()
{
tls_params_init();
tls_threads_init();
}
/* tls_client_setup - setup client-side TLS engine */
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_client_create - create client-side connection */
TLS_APPL_STATE *tls_client_create(const TLS_CLIENT_INIT_PROPS *props)
{
const char *myname = "tls_client_create";
long off = 0;
int cachable;
SSL_CTX *client_ctx;
TLS_APPL_STATE *app_ctx;
/*
* 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) {
acl_msg_warn("%s: cannot allocate client SSL_CTX: disabling TLS support", myname);
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 (props->log_level >= 2)
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 (props->cache_type == 0 || tls_mgr_policy(props->cache_type, &cachable) != TLS_MGR_STAT_OK)
cachable = 0;
/*
* Allocate an application context, and populate with mandatory protocol
* and cipher data.
*/
app_ctx = tls_alloc_app_context(client_ctx);
/*
* The external session cache is implemented by the tlsmgr(8) process.
*/
if (cachable) {
app_ctx->cache_type = acl_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_AUTO_CLEAR |
SSL_SESS_CACHE_NO_INTERNAL_STORE);
SSL_CTX_sess_set_new_cb(client_ctx, new_client_session_cb);
}
return (app_ctx);
}
/* match_hostname - match hostname against pattern */
static int match_hostname(const char *peerid, const TLS_CLIENT_START_PROPS *props)
{
const ACL_ARGV *cmatch_argv = props->matchargv;
const char *nexthop = props->nexthop;
const char *hname = props->host;
const char *pattern;
const char *pattern_left;
int sub;
int i;
int idlen;
int patlen;
/*
* Match the peerid against each pattern until we find a match.
*/
for (i = 0; i < cmatch_argv->argc; ++i) {
sub = 0;
if (!strcasecmp(cmatch_argv->argv[i], "nexthop"))
pattern = nexthop;
else if (!strcasecmp(cmatch_argv->argv[i], "hostname"))
pattern = hname;
else if (!strcasecmp(cmatch_argv->argv[i], "dot-nexthop")) {
pattern = nexthop;
sub = 1;
} else {
pattern = cmatch_argv->argv[i];
if (*pattern == '.' && pattern[1] != '\0') {
++pattern;
sub = 1;
}
}
/*
* Sub-domain match: peerid is any sub-domain of pattern.
*/
if (sub) {
if ((idlen = (int) strlen(peerid)) > (patlen = (int) strlen(pattern)) + 1
&& peerid[idlen - patlen - 1] == '.'
&& !strcasecmp(peerid + (idlen - patlen), pattern))
return (1);
else
continue;
}
/*
* Exact match and initial "*" match. The initial "*" in a peerid
* matches exactly one hostname component, under the condition that
* the peerid contains multiple hostname components.
*/
if (!strcasecmp(peerid, pattern)
|| (peerid[0] == '*' && peerid[1] == '.' && peerid[2] != 0
&& (pattern_left = strchr(pattern, '.')) != 0
&& strcasecmp(pattern_left + 1, peerid + 2) == 0))
return (1);
}
return (0);
}
/* verify_extract_name - verify peer name and extract peer information */
static void verify_extract_name(TLS_SESS_STATE *TLScontext, X509 *peercert,
const TLS_CLIENT_START_PROPS *props)
{
int i;
int r;
int matched = 0;
const char *dnsname;
const GENERAL_NAME *gn;
STACK_OF(GENERAL_NAME) * gens;
/*
* On exit both peer_CN and issuer_CN should be set.
*/
TLScontext->issuer_CN = tls_issuer_CN(peercert, TLScontext);
/*
* Is the certificate trust chain valid and trusted?
*/
if (SSL_get_verify_result(TLScontext->con) == X509_V_OK)
TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED;
if (TLS_CERT_IS_TRUSTED(TLScontext) && props->tls_level >= TLS_LEV_VERIFY) {
/*
* Verify the dNSName(s) in the peer certificate against the nexthop
* and hostname.
*
* If DNS names are present, we use the first matching (or else simply
* the first) DNS name as the subject CN. The CommonName in the
* issuer DN is obsolete when SubjectAltName is available. This
* yields much less surprising logs, because we log the name we
* verified or a name we checked and failed to match.
*
* XXX: The nexthop and host name may both be the same network address
* rather than a DNS name. In this case we really should be looking
* for GEN_IPADD entries, not GEN_DNS entries.
*
* XXX: In ideal world the caller who used the address to build the
* connection would tell us that the nexthop is the connection
* address, but if that is not practical, we can parse the nexthop
* again here.
*/
gens = X509_get_ext_d2i(peercert, NID_subject_alt_name, 0, 0);
if (gens) {
r = sk_GENERAL_NAME_num(gens);
for (i = 0; i < r && !matched; ++i) {
gn = sk_GENERAL_NAME_value(gens, i);
if (gn->type != GEN_DNS)
continue;
/*
* Even if we have an invalid DNS name, we still ultimately
* ignore the CommonName, because subjectAltName:DNS is
* present (though malformed). Replace any previous peer_CN
* if empty or we get a match.
*
* We always set at least an empty peer_CN if the ALTNAME cert
* flag is set. If not, we set peer_CN from the cert
* CommonName below, so peer_CN is always non-null on return.
*/
TLScontext->peer_status |= TLS_CERT_FLAG_ALTNAME;
dnsname = tls_dns_name(gn, TLScontext);
if (dnsname && *dnsname) {
matched = match_hostname(dnsname, props);
if (TLScontext->peer_CN
&& (matched || *TLScontext->peer_CN == 0)) {
acl_myfree(TLScontext->peer_CN);
TLScontext->peer_CN = 0;
}
}
if (TLScontext->peer_CN == 0)
TLScontext->peer_CN = acl_mystrdup(dnsname ? dnsname : "");
}
/*
* (Sam Rushing, Ironport) Free stack *and* member GENERAL_NAME
* objects
*/
sk_GENERAL_NAME_pop_free(gens, GENERAL_NAME_free);
}
/*
* No subjectAltNames, peer_CN is taken from CommonName.
*/
if (TLScontext->peer_CN == 0) {
TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext);
if (*TLScontext->peer_CN)
matched = match_hostname(TLScontext->peer_CN, props);
}
if (matched)
TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED;
/*
* - Matched: Trusted and peername matches - Trusted: Signed by
* trusted CA(s), but peername not matched - Untrusted: Can't verify
* the trust chain, reason already logged.
*/
if (TLScontext->log_level >= 2)
acl_msg_info("%s: %s subject_CN=%s, issuer_CN=%s", props->namaddr,
TLS_CERT_IS_MATCHED(TLScontext) ? "Matched" :
TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted",
TLScontext->peer_CN, TLScontext->issuer_CN);
} else
TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext);
/*
* Give them a clue. Problems with trust chain verification were logged
* when the session was first negotiated, before the session was stored
* into the cache. We don't want mystery failures, so log the fact the
* real problem is to be found in the past.
*/
if (TLScontext->session_reused
&& !TLS_CERT_IS_TRUSTED(TLScontext)
&& TLScontext->log_level >= 1)
acl_msg_info("%s: re-using session with untrusted certificate, "
"look for details earlier in the log", props->namaddr);
}
/* verify_extract_print - extract and verify peer fingerprint */
static void verify_extract_print(TLS_SESS_STATE *TLScontext, X509 *peercert,
const TLS_CLIENT_START_PROPS *props)
{
char **cpp;
/* Non-null by contract */
TLScontext->peer_fingerprint = tls_fingerprint(peercert, props->fpt_dgst);
if (props->tls_level != TLS_LEV_FPRINT)
return;
/*
* Compare the fingerprint against each acceptable value, ignoring
* upper/lower case differences.
*/
for (cpp = props->matchargv->argv; *cpp; ++cpp)
if (strcasecmp(TLScontext->peer_fingerprint, *cpp) == 0) {
TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED;
break;
}
if (props->log_level >= 2)
acl_msg_info("%s %s%s fingerprint %s", props->namaddr,
TLS_CERT_IS_MATCHED(TLScontext) ? "Matched " : "",
props->fpt_dgst, TLScontext->peer_fingerprint);
}
/*
* 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);
}
#endif /* USE_TLS */
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