mirrors/FreeRDP
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
690a6b624d
FreeRDP/libfreerdp/crypto/tls.c

881 lines
20 KiB
C
Raw Blame History

/**
* 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 <winpr/crt.h>
#include <winpr/sspi.h>
#include <winpr/stream.h>
#include <freerdp/utils/tcp.h>
#include <freerdp/crypto/tls.h>
static CryptoCert tls_get_certificate(rdpTls* tls, BOOL peer)
{
CryptoCert cert;
X509* server_cert;
if (peer)
server_cert = SSL_get_peer_certificate(tls->ssl);
else
server_cert = SSL_get_certificate(tls->ssl);
if (!server_cert)
{
fprintf(stderr, "tls_get_certificate: failed to get the server TLS certificate\n");
cert = NULL;
}
else
{
cert = malloc(sizeof(*cert));
cert->px509 = server_cert;
}
return cert;
}
static void tls_free_certificate(CryptoCert cert)
{
X509_free(cert->px509);
free(cert);
}
#define TLS_SERVER_END_POINT "tls-server-end-point:"
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*) malloc(sizeof(SecPkgContext_Bindings));
ZeroMemory(ContextBindings, sizeof(SecPkgContext_Bindings));
ContextBindings->BindingsLength = sizeof(SEC_CHANNEL_BINDINGS) + ChannelBindingTokenLength;
ChannelBindings = (SEC_CHANNEL_BINDINGS*) malloc(ContextBindings->BindingsLength);
ZeroMemory(ChannelBindings, ContextBindings->BindingsLength);
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;
}
static void tls_ssl_info_callback(const SSL* ssl, int type, int val)
{
if (type & SSL_CB_HANDSHAKE_START)
{
}
}
BOOL tls_connect(rdpTls* tls)
{
CryptoCert cert;
long options = 0;
int connection_status;
char *hostname;
tls->ctx = SSL_CTX_new(TLSv1_client_method());
if (!tls->ctx)
{
fprintf(stderr, "SSL_CTX_new failed\n");
return FALSE;
}
//SSL_CTX_set_mode(tls->ctx, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER | SSL_MODE_ENABLE_PARTIAL_WRITE);
/**
* 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;
SSL_CTX_set_options(tls->ctx, options);
tls->ssl = SSL_new(tls->ctx);
if (!tls->ssl)
{
fprintf(stderr, "SSL_new failed\n");
return FALSE;
}
if (tls->tsg)
{
tls->bio = BIO_new(tls->methods);
if (!tls->bio)
{
fprintf(stderr, "BIO_new failed\n");
return FALSE;
}
tls->bio->ptr = tls->tsg;
SSL_set_bio(tls->ssl, tls->bio, tls->bio);
SSL_CTX_set_info_callback(tls->ctx, tls_ssl_info_callback);
}
else
{
if (SSL_set_fd(tls->ssl, tls->sockfd) < 1)
{
fprintf(stderr, "SSL_set_fd failed\n");
return FALSE;
}
}
connection_status = SSL_connect(tls->ssl);
if (connection_status <= 0)
{
if (tls_print_error("SSL_connect", tls->ssl, connection_status))
{
return FALSE;
}
}
cert = tls_get_certificate(tls, TRUE);
if (!cert)
{
fprintf(stderr, "tls_connect: tls_get_certificate failed to return the server certificate.\n");
return FALSE;
}
tls->Bindings = tls_get_channel_bindings(cert->px509);
if (!crypto_cert_get_public_key(cert, &tls->PublicKey, &tls->PublicKeyLength))
{
fprintf(stderr, "tls_connect: crypto_cert_get_public_key failed to return the server public key.\n");
tls_free_certificate(cert);
return FALSE;
}
if (tls->settings->GatewayEnabled)
hostname = tls->settings->GatewayHostname;
else
hostname = tls->settings->ServerHostname;
if (!tls_verify_certificate(tls, cert, hostname))
{
fprintf(stderr, "tls_connect: certificate not trusted, aborting.\n");
tls_disconnect(tls);
tls_free_certificate(cert);
return FALSE;
}
tls_free_certificate(cert);
return TRUE;
}
BOOL tls_accept(rdpTls* tls, const char* cert_file, const char* privatekey_file)
{
CryptoCert cert;
long options = 0;
int connection_status;
tls->ctx = SSL_CTX_new(SSLv23_server_method());
if (tls->ctx == NULL)
{
fprintf(stderr, "SSL_CTX_new failed\n");
return FALSE;
}
/*
* 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;
SSL_CTX_set_options(tls->ctx, options);
if (SSL_CTX_use_RSAPrivateKey_file(tls->ctx, privatekey_file, SSL_FILETYPE_PEM) <= 0)
{
fprintf(stderr, "SSL_CTX_use_RSAPrivateKey_file failed\n");
fprintf(stderr, "PrivateKeyFile: %s\n", privatekey_file);
return FALSE;
}
tls->ssl = SSL_new(tls->ctx);
if (!tls->ssl)
{
fprintf(stderr, "SSL_new failed\n");
return FALSE;
}
if (SSL_use_certificate_file(tls->ssl, cert_file, SSL_FILETYPE_PEM) <= 0)
{
fprintf(stderr, "SSL_use_certificate_file failed\n");
return FALSE;
}
if (SSL_set_fd(tls->ssl, tls->sockfd) < 1)
{
fprintf(stderr, "SSL_set_fd failed\n");
return FALSE;
}
while (1)
{
connection_status = SSL_accept(tls->ssl);
if (connection_status <= 0)
{
switch (SSL_get_error(tls->ssl, connection_status))
{
case SSL_ERROR_WANT_READ:
case SSL_ERROR_WANT_WRITE:
break;
default:
if (tls_print_error("SSL_accept", tls->ssl, connection_status))
return FALSE;
break;
}
}
else
{
break;
}
}
cert = tls_get_certificate(tls, FALSE);
if (!cert)
{
fprintf(stderr, "tls_connect: tls_get_certificate failed to return the server certificate.\n");
return FALSE;
}
if (!crypto_cert_get_public_key(cert, &tls->PublicKey, &tls->PublicKeyLength))
{
fprintf(stderr, "tls_connect: crypto_cert_get_public_key failed to return the server public key.\n");
tls_free_certificate(cert);
return FALSE;
}
free(cert);
fprintf(stderr, "TLS connection accepted\n");
return TRUE;
}
BOOL tls_disconnect(rdpTls* tls)
{
if (!tls)
return FALSE;
if (tls->ssl)
SSL_shutdown(tls->ssl);
return TRUE;
}
int tls_read(rdpTls* tls, BYTE* data, int length)
{
int error;
int status;
if (!tls)
return -1;
if (!tls->ssl)
return -1;
status = SSL_read(tls->ssl, data, length);
if (status <= 0)
{
error = SSL_get_error(tls->ssl, status);
//fprintf(stderr, "tls_read: length: %d status: %d error: 0x%08X\n",
// length, status, error);
switch (error)
{
case SSL_ERROR_NONE:
break;
case SSL_ERROR_WANT_READ:
case SSL_ERROR_WANT_WRITE:
status = 0;
break;
case SSL_ERROR_SYSCALL:
if ((errno == EAGAIN) || (errno == 0))
{
status = 0;
}
else
{
tls_print_error("SSL_read", tls->ssl, status);
status = -1;
}
break;
default:
tls_print_error("SSL_read", tls->ssl, status);
status = -1;
break;
}
}
return status;
}
int tls_write(rdpTls* tls, BYTE* data, int length)
{
int error;
int status;
if (!tls)
return -1;
if (!tls->ssl)
return -1;
status = SSL_write(tls->ssl, data, length);
if (status <= 0)
{
error = SSL_get_error(tls->ssl, status);
//fprintf(stderr, "tls_write: length: %d status: %d error: 0x%08X\n", length, status, error);
switch (error)
{
case SSL_ERROR_NONE:
break;
case SSL_ERROR_WANT_READ:
case SSL_ERROR_WANT_WRITE:
status = 0;
break;
case SSL_ERROR_SYSCALL:
if (errno == EAGAIN)
{
status = 0;
}
else
{
tls_print_error("SSL_write", tls->ssl, status);
status = -1;
}
break;
default:
tls_print_error("SSL_write", tls->ssl, status);
status = -1;
break;
}
}
return status;
}
int tls_write_all(rdpTls* tls, BYTE* data, int length)
{
int status;
int sent = 0;
do
{
status = tls_write(tls, &data[sent], length - sent);
if (status > 0)
sent += status;
else if (status == 0)
tls_wait_write(tls);
if (sent >= length)
break;
}
while (status >= 0);
if (status > 0)
return length;
else
return status;
}
int tls_wait_read(rdpTls* tls)
{
return freerdp_tcp_wait_read(tls->sockfd);
}
int tls_wait_write(rdpTls* tls)
{
return freerdp_tcp_wait_write(tls->sockfd);
}
static void tls_errors(const char *prefix)
{
unsigned long error;
while ((error = ERR_get_error()) != 0)
fprintf(stderr, "%s: %s\n", prefix, ERR_error_string(error, NULL));
}
BOOL tls_print_error(char* func, SSL* connection, int value)
{
switch (SSL_get_error(connection, value))
{
case SSL_ERROR_ZERO_RETURN:
fprintf(stderr, "%s: Server closed TLS connection\n", func);
return TRUE;
case SSL_ERROR_WANT_READ:
fprintf(stderr, "%s: SSL_ERROR_WANT_READ\n", func);
return FALSE;
case SSL_ERROR_WANT_WRITE:
fprintf(stderr, "%s: SSL_ERROR_WANT_WRITE\n", func);
return FALSE;
case SSL_ERROR_SYSCALL:
fprintf(stderr, "%s: I/O error: %s (%d)\n", func, strerror(errno), errno);
tls_errors(func);
return TRUE;
case SSL_ERROR_SSL:
fprintf(stderr, "%s: Failure in SSL library (protocol error?)\n", func);
tls_errors(func);
return TRUE;
default:
fprintf(stderr, "%s: Unknown error\n", func);
tls_errors(func);
return TRUE;
}
}
BOOL tls_match_hostname(char *pattern, int pattern_length, char *hostname)
{
if (strlen(hostname) == pattern_length)
{
if (memcmp((void*) hostname, (void*) pattern, pattern_length) == 0)
return TRUE;
}
if (pattern_length > 2 && pattern[0] == '*' && pattern[1] == '.' && strlen(hostname) >= pattern_length)
{
char *check_hostname = &hostname[ strlen(hostname) - pattern_length+1 ];
if (memcmp((void*) check_hostname, (void*) &pattern[1], pattern_length - 1) == 0 )
{
return TRUE;
}
}
return FALSE;
}
BOOL tls_verify_certificate(rdpTls* tls, CryptoCert cert, char* hostname)
{
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;
if (tls->settings->ExternalCertificateManagement)
{
BIO* bio;
int status;
int length;
int offset;
BYTE* pemCert;
freerdp* instance = (freerdp*) tls->settings->instance;
/**
* Don't manage certificates internally, leave it up entirely to the external client implementation
*/
bio = BIO_new(BIO_s_mem());
status = PEM_write_bio_X509(bio, cert->px509);
offset = 0;
length = 2048;
pemCert = (BYTE*) malloc(length + 1);
status = BIO_read(bio, pemCert, length);
offset += status;
while (offset >= length)
{
length *= 2;
pemCert = (BYTE*) realloc(pemCert, length + 1);
status = BIO_read(bio, &pemCert[offset], length);
if (status < 0)
break;
offset += status;
}
length = offset;
pemCert[length] = '\0';
status = -1;
if (instance->VerifyX509Certificate)
{
status = instance->VerifyX509Certificate(instance, pemCert, length, 0);
}
free(pemCert);
return (status < 0) ? FALSE : TRUE;
}
/* ignore certificate verification if user explicitly required it (discouraged) */
if (tls->settings->IgnoreCertificate)
return TRUE; /* success! */
/* if user explicitly specified a certificate name, use it instead of the hostname */
if (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);
/* 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 != NULL)
{
if (tls_match_hostname(common_name, common_name_length, hostname))
hostname_match = TRUE;
}
/* compare against alternative names */
if (alt_names != NULL)
{
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)
{
if (common_name)
{
free(common_name);
common_name = NULL;
}
verification_status = TRUE; /* success! */
}
/* if the certificate is valid but the certificate name does not match, warn user, do not accept */
if (certificate_status && !hostname_match)
tls_print_certificate_name_mismatch_error(hostname, common_name, alt_names, alt_names_count);
/* verification could not succeed with OpenSSL, use known_hosts file and prompt user for manual verification */
if (!certificate_status)
{
char* issuer;
char* subject;
char* fingerprint;
freerdp* instance = (freerdp*) tls->settings->instance;
BOOL accept_certificate = FALSE;
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, common_name, alt_names, alt_names_count);
if (instance->VerifyCertificate)
accept_certificate = instance->VerifyCertificate(instance, subject, issuer, fingerprint);
if (!accept_certificate)
{
/* user did not accept, abort and do not add entry in known_hosts file */
verification_status = FALSE; /* failure! */
}
else
{
/* user accepted certificate, add entry in known_hosts file */
certificate_data_print(tls->certificate_store, certificate_data);
verification_status = TRUE; /* success! */
}
}
else if (match == -1)
{
/* entry was found in known_hosts file, but fingerprint does not match. ask user to use it */
tls_print_certificate_error(hostname, fingerprint, tls->certificate_store->file);
if (instance->VerifyChangedCertificate)
accept_certificate = instance->VerifyChangedCertificate(instance, subject, issuer, fingerprint, "");
if (!accept_certificate)
{
/* user did not accept, abort and do not change known_hosts file */
verification_status = FALSE; /* failure! */
}
else
{
/* user accepted new certificate, add replace fingerprint for this host in known_hosts file */
certificate_data_replace(tls->certificate_store, certificate_data);
verification_status = TRUE; /* success! */
}
}
else if (match == 0)
{
verification_status = TRUE; /* success! */
}
free(issuer);
free(subject);
free(fingerprint);
}
if (certificate_data)
{
free(certificate_data->fingerprint);
free(certificate_data->hostname);
free(certificate_data);
}
#ifndef _WIN32
if (common_name)
free(common_name);
#endif
if (alt_names)
crypto_cert_subject_alt_name_free(alt_names_count, alt_names_lengths,
alt_names);
return verification_status;
}
void tls_print_certificate_error(char* hostname, char* fingerprint, char *hosts_file)
{
fprintf(stderr, "The host key for %s has changed\n", hostname);
fprintf(stderr, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\n");
fprintf(stderr, "@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @\n");
fprintf(stderr, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\n");
fprintf(stderr, "IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!\n");
fprintf(stderr, "Someone could be eavesdropping on you right now (man-in-the-middle attack)!\n");
fprintf(stderr, "It is also possible that a host key has just been changed.\n");
fprintf(stderr, "The fingerprint for the host key sent by the remote host is\n%s\n", fingerprint);
fprintf(stderr, "Please contact your system administrator.\n");
fprintf(stderr, "Add correct host key in %s to get rid of this message.\n", hosts_file);
fprintf(stderr, "Host key for %s has changed and you have requested strict checking.\n", hostname);
fprintf(stderr, "Host key verification failed.\n");
}
void tls_print_certificate_name_mismatch_error(char* hostname, char* common_name, char** alt_names, int alt_names_count)
{
int index;
assert(NULL != hostname);
assert(NULL != common_name);
fprintf(stderr, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\n");
fprintf(stderr, "@ WARNING: CERTIFICATE NAME MISMATCH! @\n");
fprintf(stderr, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\n");
fprintf(stderr, "The hostname used for this connection (%s) \n", hostname);
fprintf(stderr, "does not match %s given in the certificate:\n", alt_names_count < 1 ? "the name" : "any of the names");
fprintf(stderr, "Common Name (CN):\n");
fprintf(stderr, "\t%s\n", common_name ? common_name : "no CN found in certificate");
if (alt_names_count > 1)
{
assert(NULL != alt_names);
fprintf(stderr, "Alternative names:\n");
if (alt_names_count > 1)
{
for (index = 0; index < alt_names_count; index++)
{
assert(alt_names[index]);
fprintf(stderr, "\t %s\n", alt_names[index]);
}
}
}
fprintf(stderr, "A valid certificate for the wrong name should NOT be trusted!\n");
}
rdpTls* tls_new(rdpSettings* settings)
{
rdpTls* tls;
tls = (rdpTls*) malloc(sizeof(rdpTls));
if (tls)
{
ZeroMemory(tls, sizeof(rdpTls));
SSL_load_error_strings();
SSL_library_init();
tls->settings = settings;
tls->certificate_store = certificate_store_new(settings);
}
return tls;
}
void tls_free(rdpTls* tls)
{
if (tls)
{
if (tls->ssl)
{
SSL_free(tls->ssl);
tls->ssl = NULL;
}
if (tls->ctx)
{
SSL_CTX_free(tls->ctx);
tls->ctx = NULL;
}
if (tls->PublicKey)
{
free(tls->PublicKey);
tls->PublicKey = NULL;
}
if (tls->Bindings)
{
free(tls->Bindings->Bindings);
free(tls->Bindings);
tls->Bindings = NULL;
}
certificate_store_free(tls->certificate_store);
tls->certificate_store = NULL;
free(tls);
}
}
Reference in New Issue View Git Blame Copy Permalink