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/*++
/* NAME
/* tls_server 3
/* SUMMARY
/* server-side TLS engine
/* SYNOPSIS
/* #include <tls.h>
/*
/* TLS_APPL_STATE *tls_server_init(props)
/* const TLS_SERVER_INIT_PROPS *props;
/*
/* TLS_SESS_STATE *tls_server_start(props)
/* const TLS_SERVER_START_PROPS *props;
/*
/* TLS_SESS_STATE *tls_server_post_accept(TLScontext)
/* TLS_SESS_STATE *TLScontext;
/*
/* void tls_server_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 servers,
/* the OpenSSL library, and the TLS entropy and cache manager.
/*
/* See "EVENT_DRIVEN APPLICATIONS" below for using this code
/* in event-driven programs.
/*
/* tls_server_init() is called once when the SMTP server
/* initializes.
/* Certificate details are also decided during this phase,
/* so that peer-specific behavior is not possible.
/*
/* tls_server_start() activates the TLS feature for the VSTREAM
/* passed as argument. We assume that network buffers are flushed
/* and the TLS handshake can begin immediately.
/*
/* tls_server_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. One or more of TLS_CERT_FLAG_PRESENT and
/* TLS_CERT_FLAG_TRUSTED.
/* .IP TLScontext->peer_CN
/* Extracted CommonName of the peer, or zero-length string
/* when information could not be extracted.
/* .IP TLScontext->issuer_CN
/* Extracted CommonName of the issuer, or zero-length string
/* when information could not be extracted.
/* .IP TLScontext->peer_cert_fprint
/* Fingerprint of the certificate, or zero-length string when no peer
/* certificate is available.
/* .PP
/* If no peer certificate is presented the peer_status is set to 0.
/* EVENT_DRIVEN APPLICATIONS
/* .ad
/* .fi
/* Event-driven programs manage multiple I/O channels. Such
/* programs cannot use the synchronous VSTREAM-over-TLS
/* implementation that the current TLS library provides,
/* including tls_server_stop() and the underlying tls_stream(3)
/* and tls_bio_ops(3) routines.
/*
/* With the current TLS library implementation, this means
/* that the application is responsible for calling and retrying
/* SSL_accept(), SSL_read(), SSL_write() and SSL_shutdown().
/*
/* To maintain control over TLS I/O, an event-driven server
/* invokes tls_server_start() with a null VSTREAM argument and
/* with an fd argument that specifies the I/O file descriptor.
/* Then, tls_server_start() performs all the necessary
/* preparations before the TLS handshake and returns a partially
/* populated TLS context. The event-driven application is then
/* responsible for invoking SSL_accept(), and if successful,
/* for invoking tls_server_post_accept() to finish the work
/* that was started by tls_server_start(). In case of unrecoverable
/* failure, tls_server_post_accept() destroys the TLS context
/* and returns a null pointer value.
/* 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 <unistd.h>
#include <string.h>
/* Utility library. */
#include <mymalloc.h>
#include <vstring.h>
#include <vstream.h>
#include <dict.h>
#include <stringops.h>
#include <msg.h>
#include <hex_code.h>
#include <iostuff.h> /* non-blocking */
/* Global library. */
#include <mail_params.h>
/* TLS library. */
#include <tls_mgr.h>
#define TLS_INTERNAL
#include <tls.h>
#define STR(x) vstring_str(x)
#define LEN(x) VSTRING_LEN(x)
/* Application-specific. */
/*
* The session_id_context indentifies the service that created a session.
* This information is used to distinguish between multiple TLS-based
* servers running on the same server. We use the name of the mail system.
*/
static const char server_session_id_context[] = "Postfix/TLS";
#define GET_SID(s, v, lptr) ((v) = SSL_SESSION_get_id((s), (lptr)))
/* OpenSSL 1.1.0 bitrot */
#if OPENSSL_VERSION_NUMBER >= 0x10100000L
typedef const unsigned char *session_id_t;
#else
typedef unsigned char *session_id_t;
#endif
/* get_server_session_cb - callback to retrieve session from server cache */
static SSL_SESSION *get_server_session_cb(SSL *ssl, session_id_t session_id,
int session_id_length,
int *unused_copy)
{
const char *myname = "get_server_session_cb";
TLS_SESS_STATE *TLScontext;
VSTRING *cache_id;
VSTRING *session_data = vstring_alloc(2048);
SSL_SESSION *session = 0;
if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0)
msg_panic("%s: null TLScontext in session lookup callback", myname);
#define GEN_CACHE_ID(buf, id, len, service) \
do { \
buf = vstring_alloc(2 * (len + strlen(service))); \
hex_encode(buf, (char *) (id), (len)); \
vstring_sprintf_append(buf, "&s=%s", (service)); \
vstring_sprintf_append(buf, "&l=%ld", (long) OpenSSL_version_num()); \
} while (0)
GEN_CACHE_ID(cache_id, session_id, session_id_length, TLScontext->serverid);
if (TLScontext->log_mask & TLS_LOG_CACHE)
msg_info("%s: looking up session %s in %s cache", TLScontext->namaddr,
STR(cache_id), TLScontext->cache_type);
/*
* Load the session from cache and decode it.
*/
if (tls_mgr_lookup(TLScontext->cache_type, STR(cache_id),
session_data) == TLS_MGR_STAT_OK) {
session = tls_session_activate(STR(session_data), LEN(session_data));
if (session && (TLScontext->log_mask & TLS_LOG_CACHE))
msg_info("%s: reloaded session %s from %s cache",
TLScontext->namaddr, STR(cache_id),
TLScontext->cache_type);
}
/*
* Clean up.
*/
vstring_free(cache_id);
vstring_free(session_data);
return (session);
}
/* uncache_session - remove session from internal & external cache */
static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext)
{
VSTRING *cache_id;
SSL_SESSION *session = SSL_get_session(TLScontext->con);
const unsigned char *sid;
unsigned int sid_length;
SSL_CTX_remove_session(ctx, session);
if (TLScontext->cache_type == 0)
return;
GET_SID(session, sid, &sid_length);
GEN_CACHE_ID(cache_id, sid, sid_length, TLScontext->serverid);
if (TLScontext->log_mask & TLS_LOG_CACHE)
msg_info("%s: remove session %s from %s cache", TLScontext->namaddr,
STR(cache_id), TLScontext->cache_type);
tls_mgr_delete(TLScontext->cache_type, STR(cache_id));
vstring_free(cache_id);
}
/* new_server_session_cb - callback to save session to server cache */
static int new_server_session_cb(SSL *ssl, SSL_SESSION *session)
{
const char *myname = "new_server_session_cb";
VSTRING *cache_id;
TLS_SESS_STATE *TLScontext;
VSTRING *session_data;
const unsigned char *sid;
unsigned int sid_length;
if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0)
msg_panic("%s: null TLScontext in new session callback", myname);
GET_SID(session, sid, &sid_length);
GEN_CACHE_ID(cache_id, sid, sid_length, TLScontext->serverid);
if (TLScontext->log_mask & TLS_LOG_CACHE)
msg_info("%s: save session %s to %s cache", TLScontext->namaddr,
STR(cache_id), TLScontext->cache_type);
/*
* Passivate and save the session state.
*/
session_data = tls_session_passivate(session);
if (session_data)
tls_mgr_update(TLScontext->cache_type, STR(cache_id),
STR(session_data), LEN(session_data));
/*
* Clean up.
*/
if (session_data)
vstring_free(session_data);
vstring_free(cache_id);
SSL_SESSION_free(session); /* 200502 */
return (1);
}
#define NOENGINE ((ENGINE *) 0)
#define TLS_TKT_NOKEYS -1 /* No keys for encryption */
#define TLS_TKT_STALE 0 /* No matching keys for decryption */
#define TLS_TKT_ACCEPT 1 /* Ticket decryptable and re-usable */
#define TLS_TKT_REISSUE 2 /* Ticket decryptable, not re-usable */
/* ticket_cb - configure tls session ticket encrypt/decrypt context */
#if defined(SSL_OP_NO_TICKET) && !defined(OPENSSL_NO_TLSEXT)
static int ticket_cb(SSL *con, unsigned char name[], unsigned char iv[],
EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int create)
{
static const EVP_MD *sha256;
static const EVP_CIPHER *ciph;
TLS_TICKET_KEY *key;
TLS_SESS_STATE *TLScontext = SSL_get_ex_data(con, TLScontext_index);
int timeout = ((int) SSL_CTX_get_timeout(SSL_get_SSL_CTX(con))) / 2;
if ((!sha256 && (sha256 = EVP_sha256()) == 0)
|| (!ciph && (ciph = EVP_get_cipherbyname(var_tls_tkt_cipher)) == 0)
|| (key = tls_mgr_key(create ? 0 : name, timeout)) == 0
|| (create && RAND_bytes(iv, TLS_TICKET_IVLEN) <= 0))
return (create ? TLS_TKT_NOKEYS : TLS_TKT_STALE);
HMAC_Init_ex(hctx, key->hmac, TLS_TICKET_MACLEN, sha256, NOENGINE);
if (create) {
EVP_EncryptInit_ex(ctx, ciph, NOENGINE, key->bits, iv);
memcpy((void *) name, (void *) key->name, TLS_TICKET_NAMELEN);
if (TLScontext->log_mask & TLS_LOG_CACHE)
msg_info("%s: Issuing session ticket, key expiration: %ld",
TLScontext->namaddr, (long) key->tout);
} else {
EVP_DecryptInit_ex(ctx, ciph, NOENGINE, key->bits, iv);
if (TLScontext->log_mask & TLS_LOG_CACHE)
msg_info("%s: Decrypting session ticket, key expiration: %ld",
TLScontext->namaddr, (long) key->tout);
}
TLScontext->ticketed = 1;
return (TLS_TKT_ACCEPT);
}
#endif
/* tls_server_init - initialize the server-side TLS engine */
TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props)
{
SSL_CTX *server_ctx;
SSL_CTX *sni_ctx;
X509_STORE *cert_store;
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();
#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
/*
* 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();
server_ctx = SSL_CTX_new(TLS_server_method());
if (server_ctx == 0) {
msg_warn("cannot allocate server SSL_CTX: disabling TLS support");
tls_print_errors();
return (0);
}
sni_ctx = SSL_CTX_new(TLS_server_method());
if (sni_ctx == 0) {
SSL_CTX_free(server_ctx);
msg_warn("cannot allocate server SNI 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(server_ctx, 0);
SSL_CTX_set_security_level(sni_ctx, 0);
#endif
/*
* See the verify callback in tls_verify.c
*/
SSL_CTX_set_verify_depth(server_ctx, props->verifydepth + 1);
SSL_CTX_set_verify_depth(sni_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.
*/
#ifdef SSL_OP_NO_TICKET
#ifndef OPENSSL_NO_TLSEXT
ticketable = (*var_tls_tkt_cipher && scache_timeout > 0
&& !(off & SSL_OP_NO_TICKET));
if (ticketable) {
const EVP_CIPHER *ciph;
if ((ciph = EVP_get_cipherbyname(var_tls_tkt_cipher)) == 0
|| EVP_CIPHER_mode(ciph) != EVP_CIPH_CBC_MODE
|| EVP_CIPHER_iv_length(ciph) != TLS_TICKET_IVLEN
|| EVP_CIPHER_key_length(ciph) < TLS_TICKET_IVLEN
|| EVP_CIPHER_key_length(ciph) > TLS_TICKET_KEYLEN) {
msg_warn("%s: invalid value: %s; session tickets disabled",
VAR_TLS_TKT_CIPHER, var_tls_tkt_cipher);
ticketable = 0;
}
}
if (ticketable) {
SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb);
/*
* OpenSSL 1.1.1 introduces support for TLS 1.3, which can issue more
* than one ticket per handshake. While this may be appropriate for
* communication between browsers and webservers, it is not terribly
* useful for MTAs, many of which other than Postfix don't do TLS
* session caching at all, and Postfix has no mechanism for storing
* multiple session tickets, if more than one sent, the second
* clobbers the first. OpenSSL 1.1.1 servers default to issuing two
* tickets for non-resumption handshakes, we reduce this to one. Our
* ticket decryption callback already (since 2.11) asks OpenSSL to
* avoid issuing new tickets when the presented ticket is re-usable.
*/
SSL_CTX_set_num_tickets(server_ctx, 1);
}
#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, TLS_SSL_OP_PROTOMASK(protomask));
/*
* 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.
*/
if (var_tls_preempt_clist)
SSL_CTX_set_options(server_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
/* Done with server_ctx options, clone to sni_ctx */
SSL_CTX_clear_options(sni_ctx, ~0);
SSL_CTX_set_options(sni_ctx, SSL_CTX_get_options(server_ctx));
/*
* 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);
SSL_CTX_set_info_callback(sni_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 */
SSL_CTX_free(sni_ctx);
return (0);
}
/*
* Upref and share the cert store. Sadly we can't yet use
* SSL_CTX_set1_cert_store(3) which was added in OpenSSL 1.1.0.
*/
cert_store = SSL_CTX_get_cert_store(server_ctx);
X509_STORE_up_ref(cert_store);
SSL_CTX_set_cert_store(sni_ctx, cert_store);
/*
* 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->chain_files,
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 */
SSL_CTX_free(sni_ctx);
return (0);
}
/*
* 2015-12-05: Ephemeral RSA removed from OpenSSL 1.1.0-dev
*/
#if OPENSSL_VERSION_NUMBER < 0x10100000L
/*
* 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);
SSL_CTX_set_tmp_rsa_callback(sni_ctx, tls_tmp_rsa_cb);
#endif
/*
* 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);
SSL_CTX_set_tmp_dh_callback(sni_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.
*/
tls_set_eecdh_curve(server_ctx, props->eecdh_grade);
tls_set_eecdh_curve(sni_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);
SSL_CTX_set_verify(sni_ctx, verify_flags,
tls_verify_certificate_callback);
if (props->ask_ccert && *props->CAfile) {
STACK_OF(X509_NAME) *calist = SSL_load_client_CA_file(props->CAfile);
if (calist == 0) {
/* Not generally critical */
msg_warn("error loading client CA names from: %s",
props->CAfile);
tls_print_errors();
}
SSL_CTX_set_client_CA_list(server_ctx, calist);
if (calist != 0 && sk_X509_NAME_num(calist) > 0) {
calist = SSL_dup_CA_list(calist);
if (calist == 0) {
msg_warn("error duplicating client CA names for SNI");
tls_print_errors();
} else {
SSL_CTX_set_client_CA_list(sni_ctx, calist);
}
}
}
/*
* Initialize our own TLS server handle, before diving into the details
* of TLS session cache management.
*/
app_ctx = tls_alloc_app_context(server_ctx, sni_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);
}
/*
* 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;
int log_mask = app_ctx->log_mask;
/*
* Implicitly enable logging of trust chain errors when verified certs
* are required.
*/
if (props->requirecert)
log_mask |= TLS_LOG_UNTRUSTED;
if (log_mask & TLS_LOG_VERBOSE)
msg_info("setting up TLS connection from %s", props->namaddr);
/*
* 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(log_mask, props->namaddr);
TLScontext->cache_type = app_ctx->cache_type;
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);
}
cipher_list = tls_set_ciphers(TLScontext, props->cipher_grade,
props->cipher_exclusions);
if (cipher_list == 0) {
/* already warned */
tls_free_context(TLScontext);
return (0);
}
if (log_mask & TLS_LOG_VERBOSE)
msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list);
TLScontext->serverid = mystrdup(props->serverid);
TLScontext->am_server = 1;
TLScontext->stream = props->stream;
TLScontext->mdalg = props->mdalg;
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);
}
#ifdef SSL_SECOP_PEER
/* When authenticating the peer, use 80-bit plus OpenSSL security level */
if (props->requirecert)
SSL_set_security_level(TLScontext->con, 1);
#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);
/*
* 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:
* 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);
/*
* 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) {
if (ERR_peek_error() != 0) {
msg_info("SSL_accept error from %s: %d", props->namaddr, sts);
tls_print_errors();
} else if (errno != 0) {
msg_info("SSL_accept error from %s: %m", props->namaddr);
} else {
msg_info("SSL_accept error from %s: lost connection",
props->namaddr);
}
tls_free_context(TLScontext);
return (0);
}
return (tls_server_post_accept(TLScontext));
}
/* tls_server_post_accept - post-handshake processing */
TLS_SESS_STATE *tls_server_post_accept(TLS_SESS_STATE *TLScontext)
{
const SSL_CIPHER *cipher;
X509 *peer;
char buf[CCERT_BUFSIZ];
/* Turn off packet dump if only dumping the handshake */
if ((TLScontext->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 ((TLScontext->log_mask & TLS_LOG_CACHE) && TLScontext->session_reused)
msg_info("%s: Reusing old session%s", TLScontext->namaddr,
TLScontext->ticketed ? " (RFC 5077 session ticket)" : "");
/*
* 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_mask & TLS_LOG_VERBOSE) {
X509_NAME_oneline(X509_get_subject_name(peer),
buf, sizeof(buf));
msg_info("subject=%s", printable(buf, '?'));
X509_NAME_oneline(X509_get_issuer_name(peer),
buf, sizeof(buf));
msg_info("issuer=%s", printable(buf, '?'));
}
TLScontext->peer_CN = tls_peer_CN(peer, TLScontext);
TLScontext->issuer_CN = tls_issuer_CN(peer, TLScontext);
TLScontext->peer_cert_fprint = tls_cert_fprint(peer, TLScontext->mdalg);
TLScontext->peer_pkey_fprint = tls_pkey_fprint(peer, TLScontext->mdalg);
if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) {
msg_info("%s: subject_CN=%s, issuer=%s, fingerprint=%s"
", pkey_fingerprint=%s",
TLScontext->namaddr,
TLScontext->peer_CN, TLScontext->issuer_CN,
TLScontext->peer_cert_fprint,
TLScontext->peer_pkey_fprint);
}
X509_free(peer);
/*
* 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",
TLScontext->namaddr);
}
} else {
TLScontext->peer_CN = mystrdup("");
TLScontext->issuer_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));
/*
* 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);
/*
* With the handshake done, extract TLS 1.3 signature metadata.
*/
tls_get_signature_params(TLScontext);
/*
* All the key facts in a single log entry.
*/
if (TLScontext->log_mask & TLS_LOG_SUMMARY)
tls_log_summary(TLS_ROLE_SERVER, TLS_USAGE_NEW, TLScontext);
tls_int_seed();
return (TLScontext);
}
#endif /* USE_TLS */
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