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FreeRDP/libfreerdp/crypto/tls.c

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/**
* FreeRDP: A Remote Desktop Protocol Implementation
* Transport Layer Security
*
* Copyright 2011-2012 Marc-Andre Moreau <marcandre.moreau@gmail.com>
*
* 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 <assert.h>
#include <string.h>
#include <errno.h>
#include <winpr/crt.h>
#include <winpr/sspi.h>
#include <winpr/ssl.h>
#include <winpr/stream.h>
#include <freerdp/utils/ringbuffer.h>
#include <freerdp/log.h>
#include <freerdp/crypto/tls.h>
#include "../core/tcp.h"
#include "opensslcompat.h"
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#ifdef HAVE_VALGRIND_MEMCHECK_H
#include <valgrind/memcheck.h>
#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(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)
{
int PrefixLength;
BYTE CertificateHash[32];
UINT32 CertificateHashLength;
BYTE* ChannelBindingToken;
UINT32 ChannelBindingTokenLength;
SEC_CHANNEL_BINDINGS* ChannelBindings;
SecPkgContext_Bindings* ContextBindings;
ZeroMemory(CertificateHash, sizeof(CertificateHash));
X509_digest(cert, EVP_sha256(), CertificateHash, &CertificateHashLength);
PrefixLength = strlen(TLS_SERVER_END_POINT);
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];
strcpy((char*) ChannelBindingToken, TLS_SERVER_END_POINT);
CopyMemory(&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 (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;
/**
* disable SSLv2 and SSLv3
*/
options |= SSL_OP_NO_SSLv2;
options |= SSL_OP_NO_SSLv3;
if (!tls_prepare(tls, underlying, SSLv23_client_method(), options, TRUE))
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(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(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_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 (settings->RedirectionFlags != 0)
{
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 (settings->RedirectionFlags != 0)
{
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, const BYTE* pem, size_t length)
{
rdpSettings* settings = tls->settings;
if (tls->isGatewayTransport)
{
settings->GatewayAcceptedCert = pem;
settings->GatewayAcceptedCertLength = length;
}
else if (settings->RedirectionFlags != 0)
{
settings->RedirectionAcceptedCert = pem;
settings->RedirectionAcceptedCertLength = length;
}
else
{
settings->AcceptedCert = pem;
settings->AcceptedCertLength = length;
}
return TRUE;
}
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** alt_names = NULL;
int alt_names_count = 0;
int* alt_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 (!crypto_cert_get_public_key(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);
else
WLog_ERR(TAG, "No VerifyX509Certificate callback registered!");
if (status > 0)
{
accept_cert(tls, pemCert, length);
}
else
free(pemCert);
if (status < 0)
{
WLog_ERR(TAG, "VerifyX509Certificate failed: (length = %d) status: [%d] %s",
length, status, pemCert);
return -1;
}
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);
alt_names = crypto_cert_subject_alt_name(cert->px509, &alt_names_count,
&alt_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 (alt_names)
{
for (index = 0; index < alt_names_count; index++)
{
if (tls_match_hostname(alt_names[index], alt_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, alt_names,
alt_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 (alt_names)
crypto_cert_subject_alt_name_free(alt_names_count, alt_names_lengths,
alt_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;
}
if (tls->bio)
{
BIO_free(tls->bio);
tls->bio = NULL;
}
if (tls->underlying)
{
BIO_free(tls->underlying);
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);
}
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