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-rw-r--r--src/tls/tls_server.c1051
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diff --git a/src/tls/tls_server.c b/src/tls/tls_server.c
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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>
+#if OPENSSL_VERSION_PREREQ(3,0)
+#include <openssl/core_names.h> /* EVP_MAC parameters */
+#endif
+
+#define STR(x) vstring_str(x)
+#define LEN(x) VSTRING_LEN(x)
+
+/* Application-specific. */
+
+ /*
+ * The session_id_context identifies 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";
+
+#ifndef OPENSSL_NO_TLSEXT
+ /*
+ * We retain the cipher handle for the lifetime of the process.
+ */
+static const EVP_CIPHER *tkt_cipher;
+#endif
+
+#define GET_SID(s, v, lptr) ((v) = SSL_SESSION_get_id((s), (lptr)))
+
+typedef const unsigned char *session_id_t;
+
+/* 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 */
+
+#if !defined(OPENSSL_NO_TLSEXT)
+
+#if OPENSSL_VERSION_PREREQ(3,0)
+
+/* ticket_cb - configure tls session ticket encrypt/decrypt context */
+
+static int ticket_cb(SSL *con, unsigned char name[], unsigned char iv[],
+ EVP_CIPHER_CTX *ctx, EVP_MAC_CTX *hctx, int create)
+{
+ OSSL_PARAM params[3];
+ 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 ((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);
+
+ params[0] = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_DIGEST,
+ LN_sha256, 0);
+ params[1] = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
+ (char *) key->hmac,
+ TLS_TICKET_MACLEN);
+ params[2] = OSSL_PARAM_construct_end();
+ if (!EVP_MAC_CTX_set_params(hctx, params))
+ return (create ? TLS_TKT_NOKEYS : TLS_TKT_STALE);
+
+ if (create) {
+ EVP_EncryptInit_ex(ctx, tkt_cipher, 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, tkt_cipher, 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);
+}
+
+#else /* OPENSSL_VERSION_PREREQ(3,0) */
+
+/* ticket_cb - configure tls session ticket encrypt/decrypt context */
+
+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;
+ 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)
+ || (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, tkt_cipher, 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, tkt_cipher, 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 /* OPENSSL_VERSION_PREREQ(3,0) */
+
+#endif /* defined(SSL_OP_NO_TICKET) &&
+ * !defined(OPENSSL_NO_TLSEXT) */
+
+/* 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;
+ int min_proto;
+ int max_proto;
+ TLS_APPL_STATE *app_ctx;
+ int log_mask;
+
+ /*
+ * Convert user loglevel to internal logmask.
+ */
+ log_mask = tls_log_mask(props->log_param, props->log_level);
+
+ if (log_mask & TLS_LOG_VERBOSE)
+ msg_info("initializing the server-side TLS engine");
+
+ /*
+ * Load (mostly cipher related) TLS-library internal main.cf parameters.
+ */
+ tls_param_init();
+
+ /*
+ * Detect mismatch between compile-time headers and run-time library.
+ */
+ tls_check_version();
+
+ /*
+ * Initialize the OpenSSL library, possibly loading its configuration
+ * file.
+ */
+ if (tls_library_init() == 0)
+ return (0);
+
+ /*
+ * First validate the protocols. If these are invalid, we can't continue.
+ */
+ protomask = tls_proto_mask_lims(props->protocols, &min_proto, &max_proto);
+ 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;
+
+ /*
+ * Presently we use TLS only with SMTP where truncation attacks are not
+ * possible as a result of application framing. If we ever use TLS in
+ * some other application protocol where truncation could be relevant,
+ * we'd need to disable truncation detection conditionally, or explicitly
+ * clear the option in that code path.
+ */
+ off |= SSL_OP_IGNORE_UNEXPECTED_EOF;
+
+ /*
+ * 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.
+ */
+#ifndef OPENSSL_NO_TLSEXT
+ ticketable = (*var_tls_tkt_cipher && scache_timeout > 0
+ && !(off & SSL_OP_NO_TICKET));
+ if (ticketable) {
+#if OPENSSL_VERSION_PREREQ(3,0)
+ tkt_cipher = EVP_CIPHER_fetch(NULL, var_tls_tkt_cipher, NULL);
+#else
+ tkt_cipher = EVP_get_cipherbyname(var_tls_tkt_cipher);
+#endif
+ if (tkt_cipher == 0
+ || EVP_CIPHER_mode(tkt_cipher) != EVP_CIPH_CBC_MODE
+ || EVP_CIPHER_iv_length(tkt_cipher) != TLS_TICKET_IVLEN
+ || EVP_CIPHER_key_length(tkt_cipher) < TLS_TICKET_IVLEN
+ || EVP_CIPHER_key_length(tkt_cipher) > TLS_TICKET_KEYLEN) {
+ msg_warn("%s: invalid value: %s; session tickets disabled",
+ VAR_TLS_TKT_CIPHER, var_tls_tkt_cipher);
+ ticketable = 0;
+ }
+ }
+ if (ticketable) {
+#if OPENSSL_VERSION_PREREQ(3,0)
+ SSL_CTX_set_tlsext_ticket_key_evp_cb(server_ctx, ticket_cb);
+#else
+ SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb);
+#endif
+
+ /*
+ * 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;
+
+ SSL_CTX_set_options(server_ctx, off);
+
+ /*
+ * Global protocol selection.
+ */
+ if (protomask != 0)
+ SSL_CTX_set_options(server_ctx, TLS_SSL_OP_PROTOMASK(protomask));
+ SSL_CTX_set_min_proto_version(server_ctx, min_proto);
+ SSL_CTX_set_max_proto_version(server_ctx, max_proto);
+ SSL_CTX_set_min_proto_version(sni_ctx, min_proto);
+ SSL_CTX_set_max_proto_version(sni_ctx, max_proto);
+
+ /*
+ * 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);
+ }
+
+ /*
+ * 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.
+ */
+ if (*props->dh1024_param_file != 0)
+ tls_set_dh_from_file(props->dh1024_param_file);
+ tls_tmp_dh(server_ctx, 1);
+ tls_tmp_dh(sni_ctx, 1);
+
+ /*
+ * Enable EECDH if available, errors are not fatal, we just keep going
+ * with any remaining key-exchange algorithms.
+ */
+ tls_auto_eecdh_curves(server_ctx, var_tls_eecdh_auto);
+ tls_auto_eecdh_curves(sni_ctx, var_tls_eecdh_auto);
+
+ /*
+ * 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_INTERNAL |
+ 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)
+ tls_set_bio_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 handshake 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)
+ tls_set_bio_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 = TLS_PEEK_PEER_CERT(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);
+ }
+ TLS_FREE_PEER_CERT(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 */