/* $NetBSD: tls_client.c,v 1.10 2017/02/14 01:16:48 christos Exp $ */
/*++
/* 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,
/* TLS_CERT_FLAG_MATCHED and TLS_CERT_FLAG_SECURED.
/* .IP TLScontext->peer_CN
/* Extracted CommonName of the peer, or zero-length string if the
/* information could not be extracted.
/* .IP TLScontext->issuer_CN
/* Extracted CommonName of the issuer, or zero-length string if the
/* information could not be extracted.
/* .IP TLScontext->peer_cert_fprint
/* At the fingerprint security level, if the peer presented a certificate
/* the fingerprint of the certificate.
/* .PP
/* If no peer certificate is presented the peer_status is set to 0.
/* 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
/*--*/
/* System library. */
#include <sys_defs.h>
#ifdef USE_TLS
#include <string.h>
#ifdef STRCASECMP_IN_STRINGS_H
#include <strings.h>
#endif
/* Utility library. */
#include <argv.h>
#include <mymalloc.h>
#include <vstring.h>
#include <vstream.h>
#include <stringops.h>
#include <msg.h>
#include <iostuff.h> /* non-blocking */
#include <midna_domain.h>
/* Global library. */
#include <mail_params.h>
/* TLS library. */
#include <tls_mgr.h>
#define TLS_INTERNAL
#include <tls.h>
/* Application-specific. */
#define STR vstring_str
#define LEN VSTRING_LEN
/* load_clnt_session - load session from client cache (non-callback) */
static SSL_SESSION *load_clnt_session(TLS_SESS_STATE *TLScontext)
{
const char *myname = "load_clnt_session";
SSL_SESSION *session = 0;
VSTRING *session_data = vstring_alloc(2048);
/*
* Prepare the query.
*/
if (TLScontext->log_mask & TLS_LOG_CACHE)
/* serverid contains transport:addr:port information */
msg_info("looking for session %s in %s cache",
TLScontext->serverid, TLScontext->cache_type);
/*
* We only get here if the cache_type is not empty. This code is not
* called unless caching is enabled and the cache_type is stored in the
* server SSL context.
*/
if (TLScontext->cache_type == 0)
msg_panic("%s: null client session cache type in session lookup",
myname);
/*
* Look up and activate the SSL_SESSION object. Errors are non-fatal,
* since caching is only an optimization.
*/
if (tls_mgr_lookup(TLScontext->cache_type, TLScontext->serverid,
session_data) == TLS_MGR_STAT_OK) {
session = tls_session_activate(STR(session_data), LEN(session_data));
if (session) {
if (TLScontext->log_mask & TLS_LOG_CACHE)
/* serverid contains transport:addr:port information */
msg_info("reloaded session %s from %s cache",
TLScontext->serverid, TLScontext->cache_type);
}
}
/*
* Clean up.
*/
vstring_free(session_data);
return (session);
}
/* new_client_session_cb - name new session and save it to client cache */
static int new_client_session_cb(SSL *ssl, SSL_SESSION *session)
{
const char *myname = "new_client_session_cb";
TLS_SESS_STATE *TLScontext;
VSTRING *session_data;
/*
* The cache name (if caching is enabled in tlsmgr(8)) and the cache ID
* string for this session are stored in the TLScontext. It cannot be
* null at this point.
*/
if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0)
msg_panic("%s: null TLScontext in new session callback", myname);
/*
* We only get here if the cache_type is not empty. This callback is not
* set unless caching is enabled and the cache_type is stored in the
* server SSL context.
*/
if (TLScontext->cache_type == 0)
msg_panic("%s: null session cache type in new session callback",
myname);
if (TLScontext->log_mask & TLS_LOG_CACHE)
/* serverid contains transport:addr:port information */
msg_info("save session %s to %s cache",
TLScontext->serverid, TLScontext->cache_type);
/*
* Passivate and save the session object. Errors are non-fatal, since
* caching is only an optimization.
*/
if ((session_data = tls_session_passivate(session)) != 0) {
tls_mgr_update(TLScontext->cache_type, TLScontext->serverid,
STR(session_data), LEN(session_data));
vstring_free(session_data);
}
/*
* Clean up.
*/
SSL_SESSION_free(session); /* 200502 */
return (1);
}
/* uncache_session - remove session from the external cache */
static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext)
{
SSL_SESSION *session = SSL_get_session(TLScontext->con);
SSL_CTX_remove_session(ctx, session);
if (TLScontext->cache_type == 0 || TLScontext->serverid == 0)
return;
if (TLScontext->log_mask & TLS_LOG_CACHE)
/* serverid contains transport:addr:port information */
msg_info("remove session %s from client cache", TLScontext->serverid);
tls_mgr_delete(TLScontext->cache_type, TLScontext->serverid);
}
/* tls_client_init - initialize client-side TLS engine */
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();
#if OPENSSL_VERSION_NUMBER < 0x10100000L
/*
* 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();
#endif
/*
* 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.
*
* OpenSSL 1.1.0-dev deprecates SSLv23_client_method() in favour of
* TLS_client_method(), with the change in question signalled via a new
* TLS_ANY_VERSION macro.
*/
ERR_clear_error();
#if OPENSSL_VERSION_NUMBER >= 0x10100000L && defined(TLS_ANY_VERSION)
client_ctx = SSL_CTX_new(TLS_client_method());
#else
client_ctx = SSL_CTX_new(SSLv23_client_method());
#endif
if (client_ctx == 0) {
msg_warn("cannot allocate client SSL_CTX: disabling TLS support");
tls_print_errors();
return (0);
}
#ifdef SSL_SECOP_PEER
/* Backwards compatible security as a base for opportunistic TLS. */
SSL_CTX_set_security_level(client_ctx, 0);
#endif
/*
* See the verify callback in tls_verify.c
*/
SSL_CTX_set_verify_depth(client_ctx, props->verifydepth + 1);
/*
* 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);
}
/*
* 2015-12-05: Ephemeral RSA removed from OpenSSL 1.1.0-dev
*/
#if OPENSSL_VERSION_NUMBER < 0x10100000L
/*
* 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);
#endif
/*
* 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);
}
/* match_servername - match servername against pattern */
static int match_servername(const char *certid,
const TLS_CLIENT_START_PROPS *props)
{
const ARGV *cmatch_argv;
const char *nexthop = props->nexthop;
const char *hname = props->host;
const char *domain;
const char *parent;
const char *aname;
int match_subdomain;
int i;
int idlen;
int domlen;
if ((cmatch_argv = props->matchargv) == 0)
return 0;
#ifndef NO_EAI
/*
* DNS subjectAltNames are required to be ASCII.
*
* Per RFC 6125 Section 6.4.4 Matching the CN-ID, follows the same rules
* (6.4.1, 6.4.2 and 6.4.3) that apply to subjectAltNames. In
* particular, 6.4.2 says that the reference identifier is coerced to
* ASCII, but no conversion is stated or implied for the CN-ID, so it
* seems it only matches if it is all ASCII. Otherwise, it is some other
* sort of name.
*/
if (!allascii(certid))
return (0);
if (!allascii(nexthop) && (aname = midna_domain_to_ascii(nexthop)) != 0) {
if (msg_verbose)
msg_info("%s asciified to %s", nexthop, aname);
nexthop = aname;
}
#endif
/*
* Match the certid against each pattern until we find a match.
*/
for (i = 0; i < cmatch_argv->argc; ++i) {
match_subdomain = 0;
if (!strcasecmp(cmatch_argv->argv[i], "nexthop"))
domain = nexthop;
else if (!strcasecmp(cmatch_argv->argv[i], "hostname"))
domain = hname;
else if (!strcasecmp(cmatch_argv->argv[i], "dot-nexthop")) {
domain = nexthop;
match_subdomain = 1;
} else {
domain = cmatch_argv->argv[i];
if (*domain == '.') {
if (domain[1]) {
++domain;
match_subdomain = 1;
}
}
#ifndef NO_EAI
/*
* Besides U+002E (full stop) IDNA2003 allows labels to be
* separated by any of the Unicode variants U+3002 (ideographic
* full stop), U+FF0E (fullwidth full stop), and U+FF61
* (halfwidth ideographic full stop). Their respective UTF-8
* encodings are: E38082, EFBC8E and EFBDA1.
*
* IDNA2008 does not permit (upper) case and other variant
* differences in U-labels. The midna_domain_to_ascii() function,
* based on UTS46, normalizes such differences away.
*
* The IDNA to_ASCII conversion does not allow empty leading labels,
* so we handle these explicitly here.
*/
else {
unsigned char *cp = (unsigned char *) domain;
if ((cp[0] == 0xe3 && cp[1] == 0x80 && cp[2] == 0x82)
|| (cp[0] == 0xef && cp[1] == 0xbc && cp[2] == 0x8e)
|| (cp[0] == 0xef && cp[1] == 0xbd && cp[2] == 0xa1)) {
if (domain[3]) {
domain = domain + 3;
match_subdomain = 1;
}
}
}
if (!allascii(domain)
&& (aname = midna_domain_to_ascii(domain)) != 0) {
if (msg_verbose)
msg_info("%s asciified to %s", domain, aname);
domain = aname;
}
#endif
}
/*
* Sub-domain match: certid is any sub-domain of hostname.
*/
if (match_subdomain) {
if ((idlen = strlen(certid)) > (domlen = strlen(domain)) + 1
&& certid[idlen - domlen - 1] == '.'
&& !strcasecmp(certid + (idlen - domlen), domain))
return (1);
else
continue;
}
/*
* Exact match and initial "*" match. The initial "*" in a certid
* matches one (if var_tls_multi_label is false) or more hostname
* components under the condition that the certid contains multiple
* hostname components.
*/
if (!strcasecmp(certid, domain)
|| (certid[0] == '*' && certid[1] == '.' && certid[2] != 0
&& (parent = strchr(domain, '.')) != 0
&& (idlen = strlen(certid + 1)) <= (domlen = strlen(parent))
&& strcasecmp(var_tls_multi_wildcard == 0 ? parent :
parent + domlen - idlen,
certid + 1) == 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;
int dnsname_match;
int verify_peername = 0;
int log_certmatch;
int verbose;
const char *dnsname;
const GENERAL_NAME *gn;
general_name_stack_t *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;
/*
* With fingerprint or dane we may already be done. Otherwise, verify the
* peername if using traditional PKI or DANE with trust-anchors.
*/
if (!TLS_CERT_IS_MATCHED(TLScontext)
&& TLS_CERT_IS_TRUSTED(TLScontext)
&& TLS_MUST_TRUST(props->tls_level))
verify_peername = 1;
/* Force cert processing so we can log the data? */
log_certmatch = TLScontext->log_mask & TLS_LOG_CERTMATCH;
/* Log cert details when processing? */
verbose = log_certmatch || (TLScontext->log_mask & TLS_LOG_VERBOSE);
if (verify_peername || log_certmatch) {
/*
* 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; ++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) {
if ((dnsname_match = match_servername(dnsname, props)) != 0)
matched++;
/* Keep the first matched name. */
if (TLScontext->peer_CN
&& ((dnsname_match && matched == 1)
|| *TLScontext->peer_CN == 0)) {
myfree(TLScontext->peer_CN);
TLScontext->peer_CN = 0;
}
if (verbose)
msg_info("%s: %ssubjectAltName: %s", props->namaddr,
dnsname_match ? "Matched " : "", dnsname);
}
if (TLScontext->peer_CN == 0)
TLScontext->peer_CN = mystrdup(dnsname ? dnsname : "");
if (matched && !log_certmatch)
break;
}
if (verify_peername && matched)
TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED;
/*
* (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_servername(TLScontext->peer_CN, props);
if (verify_peername && matched)
TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED;
if (verbose)
msg_info("%s %sCommonName %s", props->namaddr,
matched ? "Matched " : "", TLScontext->peer_CN);
} else if (verbose) {
char *tmpcn = tls_peer_CN(peercert, TLScontext);
/*
* Though the CommonName was superceded by a subjectAltName, log
* it when certificate match debugging was requested.
*/
msg_info("%s CommonName %s", TLScontext->namaddr, tmpcn);
myfree(tmpcn);
}
} else
TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext);
/*
* Give them a clue. Problems with trust chain verification are logged
* when the session is first negotiated, before the session is stored
* into the cache. We don't want mystery failures, so log the fact the
* real problem is to be found in the past.
*/
if (!TLS_CERT_IS_TRUSTED(TLScontext)
&& (TLScontext->log_mask & TLS_LOG_UNTRUSTED)) {
if (TLScontext->session_reused == 0)
tls_log_verify_error(TLScontext);
else
msg_info("%s: re-using session with untrusted certificate, "
"look for details earlier in the log", props->namaddr);
}
}
/* 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)
{
TLScontext->peer_cert_fprint = tls_cert_fprint(peercert, props->mdalg);
TLScontext->peer_pkey_fprint = tls_pkey_fprint(peercert, props->mdalg);
/*
* Whether the level is "dane" or "fingerprint" when the peer certificate
* is matched without resorting to a separate CA, we set both the trusted
* and matched bits. This simplifies logic in smtp_proto.c where "dane"
* must be trusted and matched, since some "dane" TLSA RRsets do use CAs.
*
* This also suppresses spurious logging of the peer certificate as
* untrusted in verify_extract_name().
*/
if (TLS_DANE_HASEE(props->dane)
&& tls_dane_match(TLScontext, TLS_DANE_EE, peercert, 0))
TLScontext->peer_status |=
TLS_CERT_FLAG_TRUSTED | TLS_CERT_FLAG_MATCHED;
}
/*
* 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));
#ifdef SSL_SECOP_PEER
/* When authenticating the peer, use 80-bit plus OpenSSL security level */
if (TLS_MUST_MATCH(props->tls_level))
SSL_set_security_level(TLScontext->con, 1);
#endif
/*
* 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);
/*
* Fully secured only if trusted, matched and not insecure like halfdane.
* Should perhaps also exclude "verify" (as opposed to "secure") here,
* because that can be subject to insecure MX indirection, but that's
* rather incompatible. Users have been warned.
*/
if (TLS_CERT_IS_PRESENT(TLScontext)
&& TLS_CERT_IS_TRUSTED(TLScontext)
&& TLS_CERT_IS_MATCHED(TLScontext)
&& !TLS_NEVER_SECURED(props->tls_level))
TLScontext->peer_status |= TLS_CERT_FLAG_SECURED;
/*
* 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_SECURED(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 */