/** * FreeRDP: A Remote Desktop Protocol Implementation * Transport Layer Security * * Copyright 2011-2012 Marc-Andre Moreau * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifdef HAVE_CONFIG_H #include "config.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include "../core/tcp.h" #include "opensslcompat.h" #ifdef HAVE_POLL_H #include #endif #ifdef HAVE_VALGRIND_MEMCHECK_H #include #endif #define TAG FREERDP_TAG("crypto") /** * Earlier Microsoft iOS RDP clients have sent a null or even double null * terminated hostname in the SNI TLS extension. * If the length indicator does not equal the hostname strlen OpenSSL * will abort (see openssl:ssl/t1_lib.c). * Here is a tcpdump segment of Microsoft Remote Desktop Client Version * 8.1.7 running on an iPhone 4 with iOS 7.1.2 showing the transmitted * SNI hostname TLV blob when connection to server "abcd": * 00 name_type 0x00 (host_name) * 00 06 length_in_bytes 0x0006 * 61 62 63 64 00 00 host_name "abcd\0\0" * * Currently the only (runtime) workaround is setting an openssl tls * extension debug callback that sets the SSL context's servername_done * to 1 which effectively disables the parsing of that extension type. * * Nowadays this workaround is not required anymore but still can be * activated by adding the following define: * * #define MICROSOFT_IOS_SNI_BUG */ struct _BIO_RDP_TLS { SSL* ssl; CRITICAL_SECTION lock; }; typedef struct _BIO_RDP_TLS BIO_RDP_TLS; static int bio_rdp_tls_write(BIO* bio, const char* buf, int size) { int error; int status; BIO_RDP_TLS* tls = (BIO_RDP_TLS*) BIO_get_data(bio); if (!buf || !tls) return 0; BIO_clear_flags(bio, BIO_FLAGS_WRITE | BIO_FLAGS_READ | BIO_FLAGS_IO_SPECIAL); EnterCriticalSection(&tls->lock); status = SSL_write(tls->ssl, buf, size); error = SSL_get_error(tls->ssl, status); LeaveCriticalSection(&tls->lock); if (status <= 0) { switch (error) { case SSL_ERROR_NONE: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_WRITE: BIO_set_flags(bio, BIO_FLAGS_WRITE | BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_READ: BIO_set_flags(bio, BIO_FLAGS_READ | BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_X509_LOOKUP: BIO_set_flags(bio, BIO_FLAGS_IO_SPECIAL); BIO_set_retry_reason(bio, BIO_RR_SSL_X509_LOOKUP); break; case SSL_ERROR_WANT_CONNECT: BIO_set_flags(bio, BIO_FLAGS_IO_SPECIAL); BIO_set_retry_reason(bio, BIO_RR_CONNECT); break; case SSL_ERROR_SYSCALL: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_SSL: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; } } return status; } static int bio_rdp_tls_read(BIO* bio, char* buf, int size) { int error; int status; BIO_RDP_TLS* tls = (BIO_RDP_TLS*) BIO_get_data(bio); if (!buf || !tls) return 0; BIO_clear_flags(bio, BIO_FLAGS_WRITE | BIO_FLAGS_READ | BIO_FLAGS_IO_SPECIAL); EnterCriticalSection(&tls->lock); status = SSL_read(tls->ssl, buf, size); error = SSL_get_error(tls->ssl, status); LeaveCriticalSection(&tls->lock); if (status <= 0) { switch (error) { case SSL_ERROR_NONE: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_READ: BIO_set_flags(bio, BIO_FLAGS_READ | BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_WRITE: BIO_set_flags(bio, BIO_FLAGS_WRITE | BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_X509_LOOKUP: BIO_set_flags(bio, BIO_FLAGS_IO_SPECIAL); BIO_set_retry_reason(bio, BIO_RR_SSL_X509_LOOKUP); break; case SSL_ERROR_WANT_ACCEPT: BIO_set_flags(bio, BIO_FLAGS_IO_SPECIAL); BIO_set_retry_reason(bio, BIO_RR_ACCEPT); break; case SSL_ERROR_WANT_CONNECT: BIO_set_flags(bio, BIO_FLAGS_IO_SPECIAL); BIO_set_retry_reason(bio, BIO_RR_CONNECT); break; case SSL_ERROR_SSL: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_ZERO_RETURN: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_SYSCALL: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; } } #ifdef HAVE_VALGRIND_MEMCHECK_H if (status > 0) { VALGRIND_MAKE_MEM_DEFINED(buf, status); } #endif return status; } static int bio_rdp_tls_puts(BIO* bio, const char* str) { int size; int status; if (!str) return 0; size = strlen(str); status = BIO_write(bio, str, size); return status; } static int bio_rdp_tls_gets(BIO* bio, char* str, int size) { return 1; } static long bio_rdp_tls_ctrl(BIO* bio, int cmd, long num, void* ptr) { BIO* ssl_rbio; BIO* ssl_wbio; BIO* next_bio; int status = -1; BIO_RDP_TLS* tls = (BIO_RDP_TLS*) BIO_get_data(bio); if (!tls) return 0; if (!tls->ssl && (cmd != BIO_C_SET_SSL)) return 0; next_bio = BIO_next(bio); ssl_rbio = tls->ssl ? SSL_get_rbio(tls->ssl) : NULL; ssl_wbio = tls->ssl ? SSL_get_wbio(tls->ssl) : NULL; switch (cmd) { case BIO_CTRL_RESET: SSL_shutdown(tls->ssl); if (SSL_in_connect_init(tls->ssl)) SSL_set_connect_state(tls->ssl); else if (SSL_in_accept_init(tls->ssl)) SSL_set_accept_state(tls->ssl); SSL_clear(tls->ssl); if (next_bio) status = BIO_ctrl(next_bio, cmd, num, ptr); else if (ssl_rbio) status = BIO_ctrl(ssl_rbio, cmd, num, ptr); else status = 1; break; case BIO_C_GET_FD: status = BIO_ctrl(ssl_rbio, cmd, num, ptr); break; case BIO_CTRL_INFO: status = 0; break; case BIO_CTRL_SET_CALLBACK: status = 0; break; case BIO_CTRL_GET_CALLBACK: *((ULONG_PTR*) ptr) = (ULONG_PTR) SSL_get_info_callback(tls->ssl); status = 1; break; case BIO_C_SSL_MODE: if (num) SSL_set_connect_state(tls->ssl); else SSL_set_accept_state(tls->ssl); status = 1; break; case BIO_CTRL_GET_CLOSE: status = BIO_get_shutdown(bio); break; case BIO_CTRL_SET_CLOSE: BIO_set_shutdown(bio, (int) num); status = 1; break; case BIO_CTRL_WPENDING: status = BIO_ctrl(ssl_wbio, cmd, num, ptr); break; case BIO_CTRL_PENDING: status = SSL_pending(tls->ssl); if (status == 0) status = BIO_pending(ssl_rbio); break; case BIO_CTRL_FLUSH: BIO_clear_retry_flags(bio); status = BIO_ctrl(ssl_wbio, cmd, num, ptr); BIO_copy_next_retry(bio); status = 1; break; case BIO_CTRL_PUSH: if (next_bio && (next_bio != ssl_rbio)) { #if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER) SSL_set_bio(tls->ssl, next_bio, next_bio); CRYPTO_add(&(bio->next_bio->references), 1, CRYPTO_LOCK_BIO); #else /* * We are going to pass ownership of next to the SSL object...but * we don't own a reference to pass yet - so up ref */ BIO_up_ref(next_bio); SSL_set_bio(tls->ssl, next_bio, next_bio); #endif } status = 1; break; case BIO_CTRL_POP: /* Only detach if we are the BIO explicitly being popped */ if (bio == ptr) { if (ssl_rbio != ssl_wbio) BIO_free_all(ssl_wbio); #if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER) if (next_bio) CRYPTO_add(&(bio->next_bio->references), -1, CRYPTO_LOCK_BIO); tls->ssl->wbio = tls->ssl->rbio = NULL; #else /* OpenSSL 1.1: This will also clear the reference we obtained during push */ SSL_set_bio(tls->ssl, NULL, NULL); #endif } status = 1; break; case BIO_C_GET_SSL: if (ptr) { *((SSL**) ptr) = tls->ssl; status = 1; } break; case BIO_C_SET_SSL: BIO_set_shutdown(bio, (int) num); if (ptr) { tls->ssl = (SSL*) ptr; ssl_rbio = SSL_get_rbio(tls->ssl); ssl_wbio = SSL_get_wbio(tls->ssl); } if (ssl_rbio) { if (next_bio) BIO_push(ssl_rbio, next_bio); BIO_set_next(bio, ssl_rbio); #if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER) CRYPTO_add(&(ssl_rbio->references), 1, CRYPTO_LOCK_BIO); #else BIO_up_ref(ssl_rbio); #endif } BIO_set_init(bio, 1); status = 1; break; case BIO_C_DO_STATE_MACHINE: BIO_clear_flags(bio, BIO_FLAGS_READ | BIO_FLAGS_WRITE | BIO_FLAGS_IO_SPECIAL); BIO_set_retry_reason(bio, 0); status = SSL_do_handshake(tls->ssl); if (status <= 0) { switch (SSL_get_error(tls->ssl, status)) { case SSL_ERROR_WANT_READ: BIO_set_flags(bio, BIO_FLAGS_READ | BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_WRITE: BIO_set_flags(bio, BIO_FLAGS_WRITE | BIO_FLAGS_SHOULD_RETRY); break; case SSL_ERROR_WANT_CONNECT: BIO_set_flags(bio, BIO_FLAGS_IO_SPECIAL | BIO_FLAGS_SHOULD_RETRY); BIO_set_retry_reason(bio, BIO_get_retry_reason(next_bio)); break; default: BIO_clear_flags(bio, BIO_FLAGS_SHOULD_RETRY); break; } } break; default: status = BIO_ctrl(ssl_rbio, cmd, num, ptr); break; } return status; } static int bio_rdp_tls_new(BIO* bio) { BIO_RDP_TLS* tls; BIO_set_flags(bio, BIO_FLAGS_SHOULD_RETRY); if (!(tls = calloc(1, sizeof(BIO_RDP_TLS)))) return 0; InitializeCriticalSectionAndSpinCount(&tls->lock, 4000); BIO_set_data(bio, (void*) tls); return 1; } static int bio_rdp_tls_free(BIO* bio) { BIO_RDP_TLS* tls; if (!bio) return 0; tls = (BIO_RDP_TLS*) BIO_get_data(bio); if (!tls) return 0; if (BIO_get_shutdown(bio)) { if (BIO_get_init(bio) && tls->ssl) { SSL_shutdown(tls->ssl); SSL_free(tls->ssl); } BIO_set_init(bio, 0); BIO_set_flags(bio, 0); } DeleteCriticalSection(&tls->lock); free(tls); return 1; } static long bio_rdp_tls_callback_ctrl(BIO* bio, int cmd, bio_info_cb* fp) { int status = 0; BIO_RDP_TLS* tls; if (!bio) return 0; tls = (BIO_RDP_TLS*) BIO_get_data(bio); if (!tls) return 0; switch (cmd) { case BIO_CTRL_SET_CALLBACK: SSL_set_info_callback(tls->ssl, (void (*)(const SSL*, int, int)) fp); status = 1; break; default: status = BIO_callback_ctrl(SSL_get_rbio(tls->ssl), cmd, fp); break; } return status; } #define BIO_TYPE_RDP_TLS 68 static BIO_METHOD* BIO_s_rdp_tls(void) { static BIO_METHOD* bio_methods = NULL; if (bio_methods == NULL) { if (!(bio_methods = BIO_meth_new(BIO_TYPE_RDP_TLS, "RdpTls"))) return NULL; BIO_meth_set_write(bio_methods, bio_rdp_tls_write); BIO_meth_set_read(bio_methods, bio_rdp_tls_read); BIO_meth_set_puts(bio_methods, bio_rdp_tls_puts); BIO_meth_set_gets(bio_methods, bio_rdp_tls_gets); BIO_meth_set_ctrl(bio_methods, bio_rdp_tls_ctrl); BIO_meth_set_create(bio_methods, bio_rdp_tls_new); BIO_meth_set_destroy(bio_methods, bio_rdp_tls_free); BIO_meth_set_callback_ctrl(bio_methods, bio_rdp_tls_callback_ctrl); } return bio_methods; } static BIO* BIO_new_rdp_tls(SSL_CTX* ctx, int client) { BIO* bio; SSL* ssl; bio = BIO_new(BIO_s_rdp_tls()); if (!bio) return NULL; ssl = SSL_new(ctx); if (!ssl) { BIO_free_all(bio); return NULL; } if (client) SSL_set_connect_state(ssl); else SSL_set_accept_state(ssl); BIO_set_ssl(bio, ssl, BIO_CLOSE); return bio; } static CryptoCert tls_get_certificate(rdpTls* tls, BOOL peer) { CryptoCert cert; X509* remote_cert; STACK_OF(X509) *chain; if (peer) remote_cert = SSL_get_peer_certificate(tls->ssl); else remote_cert = X509_dup(SSL_get_certificate(tls->ssl)); if (!remote_cert) { WLog_ERR(TAG, "failed to get the server TLS certificate"); return NULL; } cert = malloc(sizeof(*cert)); if (!cert) { X509_free(remote_cert); return NULL; } cert->px509 = remote_cert; /* Get the peer's chain. If it does not exist, we're setting NULL (clean data either way) */ chain = SSL_get_peer_cert_chain(tls->ssl); cert->px509chain = chain; return cert; } static void tls_free_certificate(CryptoCert cert) { X509_free(cert->px509); free(cert); } #define TLS_SERVER_END_POINT "tls-server-end-point:" static SecPkgContext_Bindings* tls_get_channel_bindings(X509* cert) { UINT32 CertificateHashLength; BYTE* ChannelBindingToken; UINT32 ChannelBindingTokenLength; SEC_CHANNEL_BINDINGS* ChannelBindings; SecPkgContext_Bindings* ContextBindings; const size_t PrefixLength = strnlen(TLS_SERVER_END_POINT, ARRAYSIZE(TLS_SERVER_END_POINT)); BYTE CertificateHash[32] = { 0 }; X509_digest(cert, EVP_sha256(), CertificateHash, &CertificateHashLength); ChannelBindingTokenLength = PrefixLength + CertificateHashLength; ContextBindings = (SecPkgContext_Bindings*) calloc(1, sizeof(SecPkgContext_Bindings)); if (!ContextBindings) return NULL; ContextBindings->BindingsLength = sizeof(SEC_CHANNEL_BINDINGS) + ChannelBindingTokenLength; ChannelBindings = (SEC_CHANNEL_BINDINGS*) calloc(1, ContextBindings->BindingsLength); if (!ChannelBindings) goto out_free; ContextBindings->Bindings = ChannelBindings; ChannelBindings->cbApplicationDataLength = ChannelBindingTokenLength; ChannelBindings->dwApplicationDataOffset = sizeof(SEC_CHANNEL_BINDINGS); ChannelBindingToken = &((BYTE*) ChannelBindings)[ChannelBindings->dwApplicationDataOffset]; memcpy(ChannelBindingToken, TLS_SERVER_END_POINT, PrefixLength); memcpy(ChannelBindingToken + PrefixLength, CertificateHash, CertificateHashLength); return ContextBindings; out_free: free(ContextBindings); return NULL; } #if OPENSSL_VERSION_NUMBER >= 0x010000000L static BOOL tls_prepare(rdpTls* tls, BIO* underlying, const SSL_METHOD* method, int options, BOOL clientMode) #else static BOOL tls_prepare(rdpTls* tls, BIO* underlying, SSL_METHOD* method, int options, BOOL clientMode) #endif { rdpSettings* settings = tls->settings; tls->ctx = SSL_CTX_new(method); if (!tls->ctx) { WLog_ERR(TAG, "SSL_CTX_new failed"); return FALSE; } SSL_CTX_set_mode(tls->ctx, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER | SSL_MODE_ENABLE_PARTIAL_WRITE); SSL_CTX_set_options(tls->ctx, options); SSL_CTX_set_read_ahead(tls->ctx, 1); #if OPENSSL_VERSION_NUMBER >= 0x10100000L || defined(LIBRESSL_VERSION_NUMBER) SSL_CTX_set_min_proto_version(tls->ctx, TLS1_VERSION); /* min version */ SSL_CTX_set_max_proto_version(tls->ctx, 0); /* highest supported version by library */ #endif #if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER) SSL_CTX_set_security_level(tls->ctx, settings->TlsSecLevel); #endif if (settings->AllowedTlsCiphers) { if (!SSL_CTX_set_cipher_list(tls->ctx, settings->AllowedTlsCiphers)) { WLog_ERR(TAG, "SSL_CTX_set_cipher_list %s failed", settings->AllowedTlsCiphers); return FALSE; } } tls->bio = BIO_new_rdp_tls(tls->ctx, clientMode); if (BIO_get_ssl(tls->bio, &tls->ssl) < 0) { WLog_ERR(TAG, "unable to retrieve the SSL of the connection"); return FALSE; } BIO_push(tls->bio, underlying); tls->underlying = underlying; return TRUE; } static int tls_do_handshake(rdpTls* tls, BOOL clientMode) { CryptoCert cert; int verify_status; do { #ifdef HAVE_POLL_H int fd; int status; struct pollfd pollfds; #elif !defined(_WIN32) SOCKET fd; int status; fd_set rset; struct timeval tv; #else HANDLE event; DWORD status; #endif status = BIO_do_handshake(tls->bio); if (status == 1) break; if (!BIO_should_retry(tls->bio)) return -1; #ifndef _WIN32 /* we select() only for read even if we should test both read and write * depending of what have blocked */ fd = BIO_get_fd(tls->bio, NULL); if (fd < 0) { WLog_ERR(TAG, "unable to retrieve BIO fd"); return -1; } #else BIO_get_event(tls->bio, &event); if (!event) { WLog_ERR(TAG, "unable to retrieve BIO event"); return -1; } #endif #ifdef HAVE_POLL_H pollfds.fd = fd; pollfds.events = POLLIN; pollfds.revents = 0; do { status = poll(&pollfds, 1, 10); } while ((status < 0) && (errno == EINTR)); #elif !defined(_WIN32) FD_ZERO(&rset); FD_SET(fd, &rset); tv.tv_sec = 0; tv.tv_usec = 10 * 1000; /* 10ms */ status = _select(fd + 1, &rset, NULL, NULL, &tv); #else status = WaitForSingleObject(event, 10); #endif #ifndef _WIN32 if (status < 0) { WLog_ERR(TAG, "error during select()"); return -1; } #else if ((status != WAIT_OBJECT_0) && (status != WAIT_TIMEOUT)) { WLog_ERR(TAG, "error during WaitForSingleObject(): 0x%08"PRIX32"", status); return -1; } #endif } while (TRUE); cert = tls_get_certificate(tls, clientMode); if (!cert) { WLog_ERR(TAG, "tls_get_certificate failed to return the server certificate."); return -1; } tls->Bindings = tls_get_channel_bindings(cert->px509); if (!tls->Bindings) { WLog_ERR(TAG, "unable to retrieve bindings"); verify_status = -1; goto out; } if (!crypto_cert_get_public_key(cert, &tls->PublicKey, &tls->PublicKeyLength)) { WLog_ERR(TAG, "crypto_cert_get_public_key failed to return the server public key."); verify_status = -1; goto out; } /* server-side NLA needs public keys (keys from us, the server) but no certificate verify */ verify_status = 1; if (clientMode) { verify_status = tls_verify_certificate(tls, cert, tls->hostname, tls->port); if (verify_status < 1) { WLog_ERR(TAG, "certificate not trusted, aborting."); tls_send_alert(tls); verify_status = 0; } } out: tls_free_certificate(cert); return verify_status; } int tls_connect(rdpTls* tls, BIO* underlying) { int options = 0; /** * SSL_OP_NO_COMPRESSION: * * The Microsoft RDP server does not advertise support * for TLS compression, but alternative servers may support it. * This was observed between early versions of the FreeRDP server * and the FreeRDP client, and caused major performance issues, * which is why we're disabling it. */ #ifdef SSL_OP_NO_COMPRESSION options |= SSL_OP_NO_COMPRESSION; #endif /** * SSL_OP_TLS_BLOCK_PADDING_BUG: * * The Microsoft RDP server does *not* support TLS padding. * It absolutely needs to be disabled otherwise it won't work. */ options |= SSL_OP_TLS_BLOCK_PADDING_BUG; /** * SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS: * * Just like TLS padding, the Microsoft RDP server does not * support empty fragments. This needs to be disabled. */ options |= SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; #if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER) /** * disable SSLv2 and SSLv3 */ options |= SSL_OP_NO_SSLv2; options |= SSL_OP_NO_SSLv3; if (!tls_prepare(tls, underlying, SSLv23_client_method(), options, TRUE)) #else if (!tls_prepare(tls, underlying, TLS_client_method(), options, TRUE)) #endif return FALSE; #if !defined(OPENSSL_NO_TLSEXT) && !defined(LIBRESSL_VERSION_NUMBER) SSL_set_tlsext_host_name(tls->ssl, tls->hostname); #endif return tls_do_handshake(tls, TRUE); } #if defined(MICROSOFT_IOS_SNI_BUG) && !defined(OPENSSL_NO_TLSEXT) && !defined(LIBRESSL_VERSION_NUMBER) static void tls_openssl_tlsext_debug_callback(SSL* s, int client_server, int type, unsigned char* data, int len, void* arg) { if (type == TLSEXT_TYPE_server_name) { WLog_DBG(TAG, "Client uses SNI (extension disabled)"); s->servername_done = 2; } } #endif BOOL tls_accept(rdpTls* tls, BIO* underlying, rdpSettings* settings) { long options = 0; BIO* bio; RSA* rsa; X509* x509; /** * SSL_OP_NO_SSLv2: * * We only want SSLv3 and TLSv1, so disable SSLv2. * SSLv3 is used by, eg. Microsoft RDC for Mac OS X. */ options |= SSL_OP_NO_SSLv2; /** * SSL_OP_NO_COMPRESSION: * * The Microsoft RDP server does not advertise support * for TLS compression, but alternative servers may support it. * This was observed between early versions of the FreeRDP server * and the FreeRDP client, and caused major performance issues, * which is why we're disabling it. */ #ifdef SSL_OP_NO_COMPRESSION options |= SSL_OP_NO_COMPRESSION; #endif /** * SSL_OP_TLS_BLOCK_PADDING_BUG: * * The Microsoft RDP server does *not* support TLS padding. * It absolutely needs to be disabled otherwise it won't work. */ options |= SSL_OP_TLS_BLOCK_PADDING_BUG; /** * SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS: * * Just like TLS padding, the Microsoft RDP server does not * support empty fragments. This needs to be disabled. */ options |= SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; if (!tls_prepare(tls, underlying, SSLv23_server_method(), options, FALSE)) return FALSE; if (settings->PrivateKeyFile) { bio = BIO_new_file(settings->PrivateKeyFile, "rb"); if (!bio) { WLog_ERR(TAG, "BIO_new_file failed for private key %s", settings->PrivateKeyFile); return FALSE; } } else if (settings->PrivateKeyContent) { bio = BIO_new_mem_buf(settings->PrivateKeyContent, strlen(settings->PrivateKeyContent)); if (!bio) { WLog_ERR(TAG, "BIO_new_mem_buf failed for private key"); return FALSE; } } else { WLog_ERR(TAG, "no private key defined"); return FALSE; } rsa = PEM_read_bio_RSAPrivateKey(bio, NULL, NULL, NULL); BIO_free_all(bio); if (!rsa) { WLog_ERR(TAG, "invalid private key"); return FALSE; } if (SSL_use_RSAPrivateKey(tls->ssl, rsa) <= 0) { WLog_ERR(TAG, "SSL_CTX_use_RSAPrivateKey_file failed"); RSA_free(rsa); return FALSE; } if (settings->CertificateFile) { bio = BIO_new_file(settings->CertificateFile, "rb"); if (!bio) { WLog_ERR(TAG, "BIO_new_file failed for certificate %s", settings->CertificateFile); return FALSE; } } else if (settings->CertificateContent) { bio = BIO_new_mem_buf(settings->CertificateContent, strlen(settings->CertificateContent)); if (!bio) { WLog_ERR(TAG, "BIO_new_mem_buf failed for certificate"); return FALSE; } } else { WLog_ERR(TAG, "no certificate defined"); return FALSE; } x509 = PEM_read_bio_X509(bio, NULL, NULL, 0); BIO_free_all(bio); if (!x509) { WLog_ERR(TAG, "invalid certificate"); return FALSE; } if (SSL_use_certificate(tls->ssl, x509) <= 0) { WLog_ERR(TAG, "SSL_use_certificate_file failed"); X509_free(x509); return FALSE; } #if defined(MICROSOFT_IOS_SNI_BUG) && !defined(OPENSSL_NO_TLSEXT) && !defined(LIBRESSL_VERSION_NUMBER) SSL_set_tlsext_debug_callback(tls->ssl, tls_openssl_tlsext_debug_callback); #endif return tls_do_handshake(tls, FALSE) > 0; } BOOL tls_send_alert(rdpTls* tls) { if (!tls) return FALSE; if (!tls->ssl) return TRUE; /** * FIXME: The following code does not work on OpenSSL > 1.1.0 because the * SSL struct is opaqe now */ #if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER) if (tls->alertDescription != TLS_ALERT_DESCRIPTION_CLOSE_NOTIFY) { /** * OpenSSL doesn't really expose an API for sending a TLS alert manually. * * The following code disables the sending of the default "close notify" * and then proceeds to force sending a custom TLS alert before shutting down. * * Manually sending a TLS alert is necessary in certain cases, * like when server-side NLA results in an authentication failure. */ SSL_SESSION* ssl_session = SSL_get_session(tls->ssl); SSL_CTX* ssl_ctx = SSL_get_SSL_CTX(tls->ssl); SSL_set_quiet_shutdown(tls->ssl, 1); if ((tls->alertLevel == TLS_ALERT_LEVEL_FATAL) && (ssl_session)) SSL_CTX_remove_session(ssl_ctx, ssl_session); tls->ssl->s3->alert_dispatch = 1; tls->ssl->s3->send_alert[0] = tls->alertLevel; tls->ssl->s3->send_alert[1] = tls->alertDescription; if (tls->ssl->s3->wbuf.left == 0) tls->ssl->method->ssl_dispatch_alert(tls->ssl); } #endif return TRUE; } int tls_write_all(rdpTls* tls, const BYTE* data, int length) { int status; int offset = 0; BIO* bio = tls->bio; while (offset < length) { status = BIO_write(bio, &data[offset], length - offset); if (status > 0) { offset += status; } else { if (!BIO_should_retry(bio)) return -1; if (BIO_write_blocked(bio)) status = BIO_wait_write(bio, 100); else if (BIO_read_blocked(bio)) status = BIO_wait_read(bio, 100); else USleep(100); if (status < 0) return -1; } } return length; } int tls_set_alert_code(rdpTls* tls, int level, int description) { tls->alertLevel = level; tls->alertDescription = description; return 0; } BOOL tls_match_hostname(char* pattern, int pattern_length, char* hostname) { if (strlen(hostname) == pattern_length) { if (_strnicmp(hostname, pattern, pattern_length) == 0) return TRUE; } if ((pattern_length > 2) && (pattern[0] == '*') && (pattern[1] == '.') && (((int) strlen(hostname)) >= pattern_length)) { char* check_hostname = &hostname[strlen(hostname) - pattern_length + 1]; if (_strnicmp(check_hostname, &pattern[1], pattern_length - 1) == 0) { return TRUE; } } return FALSE; } static BOOL is_redirected(rdpTls* tls) { rdpSettings* settings = tls->settings; if (LB_NOREDIRECT & settings->RedirectionFlags) return FALSE; return settings->RedirectionFlags != 0; } static BOOL is_accepted(rdpTls* tls, const BYTE* pem, size_t length) { rdpSettings* settings = tls->settings; char* AccpetedKey; UINT32 AcceptedKeyLength; if (tls->isGatewayTransport) { AccpetedKey = settings->GatewayAcceptedCert; AcceptedKeyLength = settings->GatewayAcceptedCertLength; } else if (is_redirected(tls)) { AccpetedKey = settings->RedirectionAcceptedCert; AcceptedKeyLength = settings->RedirectionAcceptedCertLength; } else { AccpetedKey = settings->AcceptedCert; AcceptedKeyLength = settings->AcceptedCertLength; } if (AcceptedKeyLength > 0) { if (AcceptedKeyLength == length) { if (memcmp(AccpetedKey, pem, AcceptedKeyLength) == 0) return TRUE; } } if (tls->isGatewayTransport) { free(settings->GatewayAcceptedCert); settings->GatewayAcceptedCert = NULL; settings->GatewayAcceptedCertLength = 0; } else if (is_redirected(tls)) { free(settings->RedirectionAcceptedCert); settings->RedirectionAcceptedCert = NULL; settings->RedirectionAcceptedCertLength = 0; } else { free(settings->AcceptedCert); settings->AcceptedCert = NULL; settings->AcceptedCertLength = 0; } return FALSE; } static BOOL accept_cert(rdpTls* tls, BYTE* pem, UINT32 length) { rdpSettings* settings = tls->settings; if (tls->isGatewayTransport) { settings->GatewayAcceptedCert = (char*)pem; settings->GatewayAcceptedCertLength = length; } else if (is_redirected(tls)) { settings->RedirectionAcceptedCert = (char*)pem; settings->RedirectionAcceptedCertLength = length; } else { settings->AcceptedCert = (char*)pem; settings->AcceptedCertLength = length; } return TRUE; } static BOOL tls_extract_pem(CryptoCert cert, BYTE** PublicKey, DWORD* PublicKeyLength) { BIO* bio; int status; size_t offset; int length = 0; BOOL rc = FALSE; BYTE* pemCert = NULL; if (!PublicKey || !PublicKeyLength) return FALSE; *PublicKey = NULL; *PublicKeyLength = 0; /** * Don't manage certificates internally, leave it up entirely to the external client implementation */ bio = BIO_new(BIO_s_mem()); if (!bio) { WLog_ERR(TAG, "BIO_new() failure"); return FALSE; } status = PEM_write_bio_X509(bio, cert->px509); if (status < 0) { WLog_ERR(TAG, "PEM_write_bio_X509 failure: %d", status); goto fail; } offset = 0; length = 2048; pemCert = (BYTE*) malloc(length + 1); if (!pemCert) { WLog_ERR(TAG, "error allocating pemCert"); goto fail; } status = BIO_read(bio, pemCert, length); if (status < 0) { WLog_ERR(TAG, "failed to read certificate"); goto fail; } offset += status; while (offset >= length) { int new_len; BYTE* new_cert; new_len = length * 2; new_cert = (BYTE*) realloc(pemCert, new_len + 1); if (!new_cert) goto fail; length = new_len; pemCert = new_cert; status = BIO_read(bio, &pemCert[offset], length - offset); if (status < 0) break; offset += status; } if (status < 0) { WLog_ERR(TAG, "failed to read certificate"); goto fail; } length = offset; pemCert[length] = '\0'; *PublicKey = pemCert; *PublicKeyLength = length; rc = TRUE; fail: if (!rc) free(pemCert); BIO_free_all(bio); return rc; } int tls_verify_certificate(rdpTls* tls, CryptoCert cert, char* hostname, int port) { int match; int index; char* common_name = NULL; int common_name_length = 0; char** dns_names = 0; int dns_names_count = 0; int* dns_names_lengths = NULL; BOOL certificate_status; BOOL hostname_match = FALSE; BOOL verification_status = FALSE; rdpCertificateData* certificate_data; freerdp* instance = (freerdp*) tls->settings->instance; DWORD length; BYTE* pemCert; if (!tls_extract_pem(cert, &pemCert, &length)) return -1; /* Check, if we already accepted this key. */ if (is_accepted(tls, pemCert, length)) { free(pemCert); return 1; } if (tls->settings->ExternalCertificateManagement) { int status = -1; if (instance->VerifyX509Certificate) status = instance->VerifyX509Certificate(instance, pemCert, length, hostname, port, tls->isGatewayTransport | is_redirected(tls) ? 2 : 0); else WLog_ERR(TAG, "No VerifyX509Certificate callback registered!"); if (status > 0) { accept_cert(tls, pemCert, length); } else if (status < 0) { WLog_ERR(TAG, "VerifyX509Certificate failed: (length = %d) status: [%d] %s", length, status, pemCert); free(pemCert); return -1; } else free(pemCert); return (status == 0) ? 0 : 1; } /* ignore certificate verification if user explicitly required it (discouraged) */ if (tls->settings->IgnoreCertificate) { free(pemCert); return 1; /* success! */ } if (!tls->isGatewayTransport && tls->settings->AuthenticationLevel == 0) { free(pemCert); return 1; /* success! */ } /* if user explicitly specified a certificate name, use it instead of the hostname */ if (!tls->isGatewayTransport && tls->settings->CertificateName) hostname = tls->settings->CertificateName; /* attempt verification using OpenSSL and the ~/.freerdp/certs certificate store */ certificate_status = x509_verify_certificate(cert, tls->certificate_store->path); /* verify certificate name match */ certificate_data = crypto_get_certificate_data(cert->px509, hostname, port); /* extra common name and alternative names */ common_name = crypto_cert_subject_common_name(cert->px509, &common_name_length); dns_names = crypto_cert_get_dns_names(cert->px509, &dns_names_count, &dns_names_lengths); /* compare against common name */ if (common_name) { if (tls_match_hostname(common_name, common_name_length, hostname)) hostname_match = TRUE; } /* compare against alternative names */ if (dns_names) { for (index = 0; index < dns_names_count; index++) { if (tls_match_hostname(dns_names[index], dns_names_lengths[index], hostname)) { hostname_match = TRUE; break; } } } /* if the certificate is valid and the certificate name matches, verification succeeds */ if (certificate_status && hostname_match) verification_status = TRUE; /* success! */ /* verification could not succeed with OpenSSL, use known_hosts file and prompt user for manual verification */ if (!certificate_status || !hostname_match) { char* issuer; char* subject; char* fingerprint; DWORD accept_certificate = 0; issuer = crypto_cert_issuer(cert->px509); subject = crypto_cert_subject(cert->px509); fingerprint = crypto_cert_fingerprint(cert->px509); /* search for matching entry in known_hosts file */ match = certificate_data_match(tls->certificate_store, certificate_data); if (match == 1) { /* no entry was found in known_hosts file, prompt user for manual verification */ if (!hostname_match) tls_print_certificate_name_mismatch_error( hostname, port, common_name, dns_names, dns_names_count); /* Automatically accept certificate on first use */ if (tls->settings->AutoAcceptCertificate) { WLog_INFO(TAG, "No certificate stored, automatically accepting."); accept_certificate = 1; } else if (instance->VerifyCertificate) { accept_certificate = instance->VerifyCertificate( instance, common_name, subject, issuer, fingerprint, !hostname_match); } switch (accept_certificate) { case 1: /* user accepted certificate, add entry in known_hosts file */ verification_status = certificate_data_print(tls->certificate_store, certificate_data); break; case 2: /* user did accept temporaty, do not add to known hosts file */ verification_status = TRUE; break; default: /* user did not accept, abort and do not add entry in known_hosts file */ verification_status = FALSE; /* failure! */ break; } } else if (match == -1) { char* old_subject = NULL; char* old_issuer = NULL; char* old_fingerprint = NULL; /* entry was found in known_hosts file, but fingerprint does not match. ask user to use it */ tls_print_certificate_error(hostname, port, fingerprint, tls->certificate_store->file); if (!certificate_get_stored_data(tls->certificate_store, certificate_data, &old_subject, &old_issuer, &old_fingerprint)) WLog_WARN(TAG, "Failed to get certificate entry for %s:%d", hostname, port); if (instance->VerifyChangedCertificate) { accept_certificate = instance->VerifyChangedCertificate( instance, common_name, subject, issuer, fingerprint, old_subject, old_issuer, old_fingerprint); } free(old_subject); free(old_issuer); free(old_fingerprint); switch (accept_certificate) { case 1: /* user accepted certificate, add entry in known_hosts file */ verification_status = certificate_data_replace(tls->certificate_store, certificate_data); break; case 2: /* user did accept temporaty, do not add to known hosts file */ verification_status = TRUE; break; default: /* user did not accept, abort and do not add entry in known_hosts file */ verification_status = FALSE; /* failure! */ break; } } else if (match == 0) verification_status = TRUE; /* success! */ free(issuer); free(subject); free(fingerprint); } certificate_data_free(certificate_data); free(common_name); if (dns_names) crypto_cert_dns_names_free(dns_names_count, dns_names_lengths, dns_names); if (verification_status > 0) { accept_cert(tls, pemCert, length); } else { free(pemCert); } return (verification_status == 0) ? 0 : 1; } void tls_print_certificate_error(char* hostname, UINT16 port, char* fingerprint, char* hosts_file) { WLog_ERR(TAG, "The host key for %s:%"PRIu16" has changed", hostname, port); WLog_ERR(TAG, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); WLog_ERR(TAG, "@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); WLog_ERR(TAG, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); WLog_ERR(TAG, "IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); WLog_ERR(TAG, "Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); WLog_ERR(TAG, "It is also possible that a host key has just been changed."); WLog_ERR(TAG, "The fingerprint for the host key sent by the remote host is%s", fingerprint); WLog_ERR(TAG, "Please contact your system administrator."); WLog_ERR(TAG, "Add correct host key in %s to get rid of this message.", hosts_file); WLog_ERR(TAG, "Host key for %s has changed and you have requested strict checking.", hostname); WLog_ERR(TAG, "Host key verification failed."); } void tls_print_certificate_name_mismatch_error(char* hostname, UINT16 port, char* common_name, char** alt_names, int alt_names_count) { int index; assert(NULL != hostname); WLog_ERR(TAG, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); WLog_ERR(TAG, "@ WARNING: CERTIFICATE NAME MISMATCH! @"); WLog_ERR(TAG, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); WLog_ERR(TAG, "The hostname used for this connection (%s:%"PRIu16") ", hostname, port); WLog_ERR(TAG, "does not match %s given in the certificate:", alt_names_count < 1 ? "the name" : "any of the names"); WLog_ERR(TAG, "Common Name (CN):"); WLog_ERR(TAG, "\t%s", common_name ? common_name : "no CN found in certificate"); if (alt_names_count > 0) { assert(NULL != alt_names); WLog_ERR(TAG, "Alternative names:"); for (index = 0; index < alt_names_count; index++) { assert(alt_names[index]); WLog_ERR(TAG, "\t %s", alt_names[index]); } } WLog_ERR(TAG, "A valid certificate for the wrong name should NOT be trusted!"); } rdpTls* tls_new(rdpSettings* settings) { rdpTls* tls; tls = (rdpTls*) calloc(1, sizeof(rdpTls)); if (!tls) return NULL; tls->settings = settings; if (!settings->ServerMode) { tls->certificate_store = certificate_store_new(settings); if (!tls->certificate_store) goto out_free; } tls->alertLevel = TLS_ALERT_LEVEL_WARNING; tls->alertDescription = TLS_ALERT_DESCRIPTION_CLOSE_NOTIFY; return tls; out_free: free(tls); return NULL; } void tls_free(rdpTls* tls) { if (!tls) return; if (tls->ctx) { SSL_CTX_free(tls->ctx); tls->ctx = NULL; } /* tls->underlying is a stacked BIO under tls->bio. * BIO_free_all will free recursivly. */ BIO_free_all(tls->bio); tls->bio = NULL; tls->underlying = NULL; if (tls->PublicKey) { free(tls->PublicKey); tls->PublicKey = NULL; } if (tls->Bindings) { free(tls->Bindings->Bindings); free(tls->Bindings); tls->Bindings = NULL; } if (tls->certificate_store) { certificate_store_free(tls->certificate_store); tls->certificate_store = NULL; } free(tls); }