FreeRDP/libfreerdp-core/tls.c

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/**
* FreeRDP: A Remote Desktop Protocol Client
* Transport Layer Security
*
* Copyright 2011 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
*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
* 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.
*/
#include <freerdp/utils/stream.h>
#include <freerdp/utils/memory.h>
#include "tls.h"
boolean tls_connect(rdpTls* tls)
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{
int connection_status;
tls->ctx = SSL_CTX_new(TLSv1_client_method());
if (tls->ctx == NULL)
{
printf("SSL_CTX_new failed\n");
return false;
}
/*
* This is necessary, because the Microsoft TLS implementation is not perfect.
* SSL_OP_ALL enables a couple of workarounds for buggy TLS implementations,
* but the most important workaround being SSL_OP_TLS_BLOCK_PADDING_BUG.
* As the size of the encrypted payload may give hints about its contents,
* block padding is normally used, but the Microsoft TLS implementation
* won't recognize it and will disconnect you after sending a TLS alert.
*/
SSL_CTX_set_options(tls->ctx, SSL_OP_ALL);
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tls->ssl = SSL_new(tls->ctx);
if (tls->ssl == NULL)
{
printf("SSL_new failed\n");
return false;
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}
if (SSL_set_fd(tls->ssl, tls->sockfd) < 1)
{
printf("SSL_set_fd failed\n");
return false;
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}
connection_status = SSL_connect(tls->ssl);
if (connection_status <= 0)
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{
if (tls_print_error("SSL_connect", tls->ssl, connection_status))
return false;
}
return true;
}
boolean tls_accept(rdpTls* tls, const char* cert_file, const char* privatekey_file)
{
int connection_status;
tls->ctx = SSL_CTX_new(TLSv1_server_method());
if (tls->ctx == NULL)
{
printf("SSL_CTX_new failed\n");
return false;
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}
if (SSL_CTX_use_RSAPrivateKey_file(tls->ctx, privatekey_file, SSL_FILETYPE_PEM) <= 0)
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{
printf("SSL_CTX_use_RSAPrivateKey_file failed\n");
return false;
}
tls->ssl = SSL_new(tls->ctx);
if (tls->ssl == NULL)
{
printf("SSL_new failed\n");
return false;
}
if (SSL_use_certificate_file(tls->ssl, cert_file, SSL_FILETYPE_PEM) <= 0)
{
printf("SSL_use_certificate_file failed\n");
return false;
}
if (SSL_set_fd(tls->ssl, tls->sockfd) < 1)
{
printf("SSL_set_fd failed\n");
return false;
}
connection_status = SSL_accept(tls->ssl);
if (connection_status <= 0)
{
if (tls_print_error("SSL_accept", tls->ssl, connection_status))
return false;
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}
printf("TLS connection accepted\n");
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return true;
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}
boolean tls_disconnect(rdpTls* tls)
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{
SSL_shutdown(tls->ssl);
return true;
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}
int tls_read(rdpTls* tls, uint8* data, int length)
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{
int status;
status = SSL_read(tls->ssl, data, length);
switch (SSL_get_error(tls->ssl, status))
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{
case SSL_ERROR_NONE:
break;
case SSL_ERROR_WANT_READ:
case SSL_ERROR_WANT_WRITE:
status = 0;
break;
default:
tls_print_error("SSL_read", tls->ssl, status);
status = -1;
break;
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}
return status;
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}
int tls_write(rdpTls* tls, uint8* data, int length)
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{
int status;
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status = SSL_write(tls->ssl, data, length);
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switch (SSL_get_error(tls->ssl, status))
{
case SSL_ERROR_NONE:
break;
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case SSL_ERROR_WANT_READ:
case SSL_ERROR_WANT_WRITE:
status = 0;
break;
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default:
tls_print_error("SSL_write", tls->ssl, status);
status = -1;
break;
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}
return status;
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}
boolean tls_print_error(char *func, SSL *connection, int value)
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{
switch (SSL_get_error(connection, value))
{
case SSL_ERROR_ZERO_RETURN:
printf("%s: Server closed TLS connection\n", func);
return true;
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case SSL_ERROR_WANT_READ:
printf("SSL_ERROR_WANT_READ\n");
return false;
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case SSL_ERROR_WANT_WRITE:
printf("SSL_ERROR_WANT_WRITE\n");
return false;
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case SSL_ERROR_SYSCALL:
printf("%s: I/O error\n", func);
return true;
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case SSL_ERROR_SSL:
printf("%s: Failure in SSL library (protocol error?)\n", func);
return true;
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default:
printf("%s: Unknown error\n", func);
return true;
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}
}
CryptoCert tls_get_certificate(rdpTls * tls)
{
CryptoCert cert;
X509* server_cert;
server_cert = SSL_get_peer_certificate(tls->ssl);
if (!server_cert)
{
printf("ssl_verify: failed to get the server SSL certificate\n");
cert = NULL;
}
else
{
cert = xmalloc(sizeof(*cert));
cert->px509 = server_cert;
}
return cert;
}
rdpTls* tls_new()
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{
rdpTls* tls;
tls = (rdpTls*) xzalloc(sizeof(rdpTls));
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if (tls != NULL)
{
SSL_load_error_strings();
SSL_library_init();
}
return tls;
}
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int tls_verify_certificate(CryptoCert cert, rdpSettings* settings, char* hostname)
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{
boolean status;
rdpCertificateStore* certificate_store;
certificate_store = certificate_store_new(settings);
status = x509_verify_certificate(cert, certificate_store->path);
if (status != true)
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{
char* issuer;
char* subject;
char* fingerprint;
rdpCertificateData* certificate_data;
certificate_data = crypto_get_certificate_data(cert->px509, hostname);
if (certificate_data_match(certificate_store, certificate_data) == 0)
return 0;
issuer = crypto_cert_issuer(cert->px509);
subject = crypto_cert_subject(cert->px509);
fingerprint = crypto_cert_fingerprint(cert->px509);
if (certificate_store->match == 1)
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{
boolean accept_certificate = settings->ignore_certificate;
if (!accept_certificate)
{
freerdp* instance = (freerdp*) settings->instance;
if (instance->VerifyCertificate)
accept_certificate = instance->VerifyCertificate(instance, subject, issuer, fingerprint);
xfree(issuer);
xfree(subject);
xfree(fingerprint);
}
if (!accept_certificate)
return 1;
certificate_data_print(certificate_store, certificate_data);
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}
else if (certificate_store->match == -1)
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{
tls_print_cert_error(hostname, fingerprint);
certificate_store_free(certificate_store);
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return 1;
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}
}
certificate_store_free(certificate_store);
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return 0;
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}
void tls_print_cert_error(char* hostname, char* fingerprint)
{
printf("The host key for %s has changed\n", hostname);
printf("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\n");
printf("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @\n");
printf("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\n");
printf("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!\n");
printf("Someone could be eavesdropping on you right now (man-in-the-middle attack)!\n");
printf("It is also possible that a host key has just been changed.\n");
printf("The fingerprint for the host key sent by the remote host is\n%s\n", fingerprint);
printf("Please contact your system administrator.\n");
printf("Add correct host key in ~/.freerdp/known_hosts to get rid of this message.\n");
printf("Host key for %s has changed and you have requested strict checking.\n", hostname);
printf("Host key verification failed.\n");
}
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void tls_free(rdpTls* tls)
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{
if (tls != NULL)
{
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if (tls->ssl)
SSL_free(tls->ssl);
if (tls->ctx)
SSL_CTX_free(tls->ctx);
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xfree(tls);
}
}