/src/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>
 * Copyright 2023 Armin Novak <anovak@thincast.com>
 * Copyright 2023 Thincast Technologies GmbH
 *
 * 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.
 */

#include <freerdp/config.h>

#include "../core/settings.h"

#include <winpr/assert.h>
#include <string.h>
#include <errno.h>

#include <winpr/crt.h>
#include <winpr/string.h>
#include <winpr/sspi.h>
#include <winpr/ssl.h>

#include <winpr/stream.h>
#include <freerdp/utils/ringbuffer.h>

#include <freerdp/crypto/certificate.h>
#include <freerdp/crypto/certificate_data.h>

#include <freerdp/log.h>
#include "../crypto/tls.h"
#include "../core/tcp.h"

#include "opensslcompat.h"
#include "certificate.h"
#include "privatekey.h"

#ifdef WINPR_HAVE_POLL_H
#include <poll.h>
#endif

#ifdef FREERDP_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
 */

typedef struct
{
  SSL* ssl;
  CRITICAL_SECTION lock;
} BIO_RDP_TLS;

static int tls_verify_certificate(rdpTls* tls, const rdpCertificate* cert, const char* hostname,
                                  UINT16 port);
static void tls_print_certificate_name_mismatch_error(const char* hostname, UINT16 port,
                                                      const char* common_name, char** alt_names,
                                                      size_t alt_names_count);
static void tls_print_new_certificate_warn(rdpCertificateStore* store, const char* hostname,
                                           UINT16 port, const char* fingerprint);
static void tls_print_certificate_error(rdpCertificateStore* store, rdpCertificateData* stored_data,
                                        const char* hostname, UINT16 port, const char* fingerprint);

static void free_tls_public_key(rdpTls* tls)
{
  WINPR_ASSERT(tls);
  free(tls->PublicKey);
  tls->PublicKey = NULL;
  tls->PublicKeyLength = 0;
}

static void free_tls_bindings(rdpTls* tls)
{
  WINPR_ASSERT(tls);

  if (tls->Bindings)
    free(tls->Bindings->Bindings);

  free(tls->Bindings);
  tls->Bindings = NULL;
}

static int bio_rdp_tls_write(BIO* bio, const char* buf, int size)
{
  int error = 0;
  int status = 0;
  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 = 0;
  int status = 0;
  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 FREERDP_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)
{
  size_t size = 0;
  int status = 0;

  if (!str)
    return 0;

  size = strlen(str);
  ERR_clear_error();
  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 = NULL;
  BIO* ssl_wbio = NULL;
  BIO* next_bio = NULL;
  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:
      /* The OpenSSL API is horrible here:
       * we get a function pointer returned and have to cast it to ULONG_PTR
       * to return the value to the caller.
       *
       * This, of course, is something compilers warn about. So silence it by casting */
      {
        void* vptr = (void*)SSL_get_info_callback(tls->ssl);
        *((void**)ptr) = vptr;
        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);
      if (status != 1)
        WLog_DBG(TAG, "BIO_ctrl returned %d", status);
      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) && LIBRESSL_VERSION_NUMBER < 0x2070000fL)
        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) && LIBRESSL_VERSION_NUMBER < 0x2070000fL)

        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);
      }

      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) && LIBRESSL_VERSION_NUMBER < 0x2070000fL)
        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 = NULL;
  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 = NULL;

  if (!bio)
    return 0;

  tls = (BIO_RDP_TLS*)BIO_get_data(bio);

  if (!tls)
    return 0;

  BIO_set_data(bio, NULL);
  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)
{
  long status = 0;

  if (!bio)
    return 0;

  BIO_RDP_TLS* tls = (BIO_RDP_TLS*)BIO_get_data(bio);

  if (!tls)
    return 0;

  switch (cmd)
  {
    case BIO_CTRL_SET_CALLBACK:
    {
      typedef void (*fkt_t)(const SSL*, int, int);

      /* Documented since https://www.openssl.org/docs/man1.1.1/man3/BIO_set_callback.html
       * the argument is not really of type bio_info_cb* and must be cast
       * to the required type */

      fkt_t fkt = WINPR_FUNC_PTR_CAST(fp, fkt_t);
      SSL_set_info_callback(tls->ssl, fkt);
      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 = NULL;
  SSL* ssl = NULL;
  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 rdpCertificate* tls_get_certificate(rdpTls* tls, BOOL peer)
{
  X509* remote_cert = NULL;

  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;
  }

  /* Get the peer's chain. If it does not exist, we're setting NULL (clean data either way) */
  STACK_OF(X509)* chain = SSL_get_peer_cert_chain(tls->ssl);
  rdpCertificate* cert = freerdp_certificate_new_from_x509(remote_cert, chain);
  X509_free(remote_cert);

  return cert;
}

static const char* tls_get_server_name(rdpTls* tls)
{
  return tls->serverName ? tls->serverName : tls->hostname;
}

#define TLS_SERVER_END_POINT "tls-server-end-point:"

static SecPkgContext_Bindings* tls_get_channel_bindings(const rdpCertificate* cert)
{
  size_t CertificateHashLength = 0;
  BYTE* ChannelBindingToken = NULL;
  UINT32 ChannelBindingTokenLength = 0;
  SEC_CHANNEL_BINDINGS* ChannelBindings = NULL;
  SecPkgContext_Bindings* ContextBindings = NULL;
  const size_t PrefixLength = strnlen(TLS_SERVER_END_POINT, ARRAYSIZE(TLS_SERVER_END_POINT));

  WINPR_ASSERT(cert);

  /* See https://www.rfc-editor.org/rfc/rfc5929 for details about hashes */
  WINPR_MD_TYPE alg = freerdp_certificate_get_signature_alg(cert);
  const char* hash = NULL;
  switch (alg)
  {

    case WINPR_MD_MD5:
    case WINPR_MD_SHA1:
      hash = winpr_md_type_to_string(WINPR_MD_SHA256);
      break;
    default:
      hash = winpr_md_type_to_string(alg);
      break;
  }
  if (!hash)
    return NULL;

  char* CertificateHash = freerdp_certificate_get_hash(cert, hash, &CertificateHashLength);
  if (!CertificateHash)
    return NULL;

  ChannelBindingTokenLength = PrefixLength + CertificateHashLength;
  ContextBindings = (SecPkgContext_Bindings*)calloc(1, sizeof(SecPkgContext_Bindings));

  if (!ContextBindings)
    goto out_free;

  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);
  free(CertificateHash);
  return ContextBindings;
out_free:
  free(CertificateHash);
  free(ContextBindings);
  return NULL;
}

static INIT_ONCE secrets_file_idx_once = INIT_ONCE_STATIC_INIT;
static int secrets_file_idx = -1;

static BOOL CALLBACK secrets_file_init_cb(PINIT_ONCE once, PVOID param, PVOID* context)
{
  secrets_file_idx = SSL_get_ex_new_index(0, NULL, NULL, NULL, NULL);

  return (secrets_file_idx != -1);
}

static void SSLCTX_keylog_cb(const SSL* ssl, const char* line)
{
  char* dfile = NULL;

  if (secrets_file_idx == -1)
    return;

  dfile = SSL_get_ex_data(ssl, secrets_file_idx);
  if (dfile)
  {
    FILE* f = winpr_fopen(dfile, "a+");
    if (f)
    {
      (void)fwrite(line, strlen(line), 1, f);
      (void)fwrite("\n", 1, 1, f);
      (void)fclose(f);
    }
  }
}

static void tls_reset(rdpTls* tls)
{
  WINPR_ASSERT(tls);

  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. */
  if (tls->bio)
    BIO_free_all(tls->bio);
  else if (tls->underlying)
    BIO_free_all(tls->underlying);
  tls->bio = NULL;
  tls->underlying = NULL;

  free_tls_public_key(tls);
  free_tls_bindings(tls);
}

#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
{
  WINPR_ASSERT(tls);

  rdpSettings* settings = tls->context->settings;
  WINPR_ASSERT(settings);

  tls_reset(tls);
  tls->ctx = SSL_CTX_new(method);

  tls->underlying = underlying;

  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)
  UINT16 version = freerdp_settings_get_uint16(settings, FreeRDP_TLSMinVersion);
  if (!SSL_CTX_set_min_proto_version(tls->ctx, version))
  {
    WLog_ERR(TAG, "SSL_CTX_set_min_proto_version %s failed", version);
    return FALSE;
  }
  version = freerdp_settings_get_uint16(settings, FreeRDP_TLSMaxVersion);
  if (!SSL_CTX_set_max_proto_version(tls->ctx, version))
  {
    WLog_ERR(TAG, "SSL_CTX_set_max_proto_version %s failed", version);
    return FALSE;
  }
#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;
  }

  if (settings->TlsSecretsFile)
  {
#if OPENSSL_VERSION_NUMBER >= 0x10101000L
    InitOnceExecuteOnce(&secrets_file_idx_once, secrets_file_init_cb, NULL, NULL);

    if (secrets_file_idx != -1)
    {
      SSL_set_ex_data(tls->ssl, secrets_file_idx, settings->TlsSecretsFile);
      SSL_CTX_set_keylog_callback(tls->ctx, SSLCTX_keylog_cb);
    }
#else
    WLog_WARN(TAG, "Key-Logging not available - requires OpenSSL 1.1.1 or higher");
#endif
  }

  BIO_push(tls->bio, underlying);
  return TRUE;
}

static void adjustSslOptions(int* options)
{
  WINPR_ASSERT(options);
#if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
  *options |= SSL_OP_NO_SSLv2;
  *options |= SSL_OP_NO_SSLv3;
#endif
}

const SSL_METHOD* freerdp_tls_get_ssl_method(BOOL isDtls, BOOL isClient)
{
  if (isClient)
  {
    if (isDtls)
      return DTLS_client_method();
#if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
    return SSLv23_client_method();
#else
    return TLS_client_method();
#endif
  }

  if (isDtls)
    return DTLS_server_method();

#if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
  return SSLv23_server_method();
#else
  return TLS_server_method();
#endif
}

TlsHandshakeResult freerdp_tls_connect_ex(rdpTls* tls, BIO* underlying, const SSL_METHOD* methods)
{
  WINPR_ASSERT(tls);

  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;

  tls->isClientMode = TRUE;
  adjustSslOptions(&options);

  if (!tls_prepare(tls, underlying, methods, options, TRUE))
    return 0;

#if !defined(OPENSSL_NO_TLSEXT) && !defined(LIBRESSL_VERSION_NUMBER)
  SSL_set_tlsext_host_name(tls->ssl, tls_get_server_name(tls));
#endif

  return freerdp_tls_handshake(tls);
}

static int bio_err_print(const char* str, size_t len, void* u)
{
  wLog* log = u;
  WLog_Print(log, WLOG_ERROR, "[BIO_do_handshake] %s [%" PRIuz "]", str, len);
  return 0;
}

TlsHandshakeResult freerdp_tls_handshake(rdpTls* tls)
{
  TlsHandshakeResult ret = TLS_HANDSHAKE_ERROR;

  WINPR_ASSERT(tls);
  int status = BIO_do_handshake(tls->bio);
  if (status != 1)
  {
    if (!BIO_should_retry(tls->bio))
    {
      wLog* log = WLog_Get(TAG);
      WLog_Print(log, WLOG_ERROR, "BIO_do_handshake failed");
      ERR_print_errors_cb(bio_err_print, log);
      return TLS_HANDSHAKE_ERROR;
    }

    return TLS_HANDSHAKE_CONTINUE;
  }

  int verify_status = 0;
  rdpCertificate* cert = tls_get_certificate(tls, tls->isClientMode);

  if (!cert)
  {
    WLog_ERR(TAG, "tls_get_certificate failed to return the server certificate.");
    return TLS_HANDSHAKE_ERROR;
  }

  do
  {
    free_tls_bindings(tls);
    tls->Bindings = tls_get_channel_bindings(cert);
    if (!tls->Bindings)
    {
      WLog_ERR(TAG, "unable to retrieve bindings");
      break;
    }

    free_tls_public_key(tls);
    if (!freerdp_certificate_get_public_key(cert, &tls->PublicKey, &tls->PublicKeyLength))
    {
      WLog_ERR(TAG,
               "freerdp_certificate_get_public_key failed to return the server public key.");
      break;
    }

    /* server-side NLA needs public keys (keys from us, the server) but no certificate verify */
    ret = TLS_HANDSHAKE_SUCCESS;

    if (tls->isClientMode)
    {
      verify_status = tls_verify_certificate(tls, cert, tls_get_server_name(tls), tls->port);

      if (verify_status < 1)
      {
        WLog_ERR(TAG, "certificate not trusted, aborting.");
        freerdp_tls_send_alert(tls);
        ret = TLS_HANDSHAKE_VERIFY_ERROR;
      }
    }
  } while (0);

  freerdp_certificate_free(cert);
  return ret;
}

static int pollAndHandshake(rdpTls* tls)
{
  WINPR_ASSERT(tls);

  do
  {
    HANDLE event = NULL;
    DWORD status = 0;
    if (BIO_get_event(tls->bio, &event) < 0)
    {
      WLog_ERR(TAG, "unable to retrieve BIO associated event");
      return -1;
    }

    if (!event)
    {
      WLog_ERR(TAG, "unable to retrieve BIO event");
      return -1;
    }

    status = WaitForSingleObjectEx(event, 50, TRUE);
    switch (status)
    {
      case WAIT_OBJECT_0:
        break;
      case WAIT_TIMEOUT:
      case WAIT_IO_COMPLETION:
        continue;
      default:
        WLog_ERR(TAG, "error during WaitForSingleObject(): 0x%08" PRIX32 "", status);
        return -1;
    }

    TlsHandshakeResult result = freerdp_tls_handshake(tls);
    switch (result)
    {
      case TLS_HANDSHAKE_CONTINUE:
        break;
      case TLS_HANDSHAKE_SUCCESS:
        return 1;
      case TLS_HANDSHAKE_ERROR:
      case TLS_HANDSHAKE_VERIFY_ERROR:
      default:
        return -1;
    }
  } while (TRUE);
}

int freerdp_tls_connect(rdpTls* tls, BIO* underlying)
{
  const SSL_METHOD* method = freerdp_tls_get_ssl_method(FALSE, TRUE);

  WINPR_ASSERT(tls);
  TlsHandshakeResult result = freerdp_tls_connect_ex(tls, underlying, method);
  switch (result)
  {
    case TLS_HANDSHAKE_SUCCESS:
      return 1;
    case TLS_HANDSHAKE_CONTINUE:
      break;
    case TLS_HANDSHAKE_ERROR:
    case TLS_HANDSHAKE_VERIFY_ERROR:
      return -1;
  }

  return pollAndHandshake(tls);
}

#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 freerdp_tls_accept(rdpTls* tls, BIO* underlying, rdpSettings* settings)
{
  WINPR_ASSERT(tls);
  TlsHandshakeResult res =
      freerdp_tls_accept_ex(tls, underlying, settings, freerdp_tls_get_ssl_method(FALSE, FALSE));
  switch (res)
  {
    case TLS_HANDSHAKE_SUCCESS:
      return TRUE;
    case TLS_HANDSHAKE_CONTINUE:
      break;
    case TLS_HANDSHAKE_ERROR:
    case TLS_HANDSHAKE_VERIFY_ERROR:
    default:
      return FALSE;
  }

  return pollAndHandshake(tls) > 0;
}

TlsHandshakeResult freerdp_tls_accept_ex(rdpTls* tls, BIO* underlying, rdpSettings* settings,
                                         const SSL_METHOD* methods)
{
  WINPR_ASSERT(tls);

  long options = 0;
  int status = 0;

  /**
   * 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_OP_NO_RENEGOTIATION
   *
   * Disable SSL client site renegotiation.
   */

#if (OPENSSL_VERSION_NUMBER >= 0x10101000L) && (OPENSSL_VERSION_NUMBER < 0x30000000L) && \
    !defined(LIBRESSL_VERSION_NUMBER)
  options |= SSL_OP_NO_RENEGOTIATION;
#endif

  if (!tls_prepare(tls, underlying, methods, options, FALSE))
    return TLS_HANDSHAKE_ERROR;

  const rdpPrivateKey* key = freerdp_settings_get_pointer(settings, FreeRDP_RdpServerRsaKey);
  if (!key)
  {
    WLog_ERR(TAG, "invalid private key");
    return TLS_HANDSHAKE_ERROR;
  }

  EVP_PKEY* privkey = freerdp_key_get_evp_pkey(key);
  if (!privkey)
  {
    WLog_ERR(TAG, "invalid private key");
    return TLS_HANDSHAKE_ERROR;
  }

  status = SSL_use_PrivateKey(tls->ssl, privkey);
  /* The local reference to the private key will anyway go out of
   * scope; so the reference count should be decremented weither
   * SSL_use_PrivateKey succeeds or fails.
   */
  EVP_PKEY_free(privkey);

  if (status <= 0)
  {
    WLog_ERR(TAG, "SSL_CTX_use_PrivateKey_file failed");
    return TLS_HANDSHAKE_ERROR;
  }

  rdpCertificate* cert =
      freerdp_settings_get_pointer_writable(settings, FreeRDP_RdpServerCertificate);
  if (!cert)
  {
    WLog_ERR(TAG, "invalid certificate");
    return TLS_HANDSHAKE_ERROR;
  }

  status = SSL_use_certificate(tls->ssl, freerdp_certificate_get_x509(cert));

  if (status <= 0)
  {
    WLog_ERR(TAG, "SSL_use_certificate_file failed");
    return TLS_HANDSHAKE_ERROR;
  }

#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 freerdp_tls_handshake(tls);
}

BOOL freerdp_tls_send_alert(rdpTls* tls)
{
  WINPR_ASSERT(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 (!defined(LIBRESSL_VERSION_NUMBER) && (OPENSSL_VERSION_NUMBER < 0x10100000L)) || \
    (defined(LIBRESSL_VERSION_NUMBER) && (LIBRESSL_VERSION_NUMBER <= 0x2080300fL))

  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 freerdp_tls_write_all(rdpTls* tls, const BYTE* data, int length)
{
  WINPR_ASSERT(tls);
  int status = 0;
  int offset = 0;
  BIO* bio = tls->bio;

  while (offset < length)
  {
    ERR_clear_error();
    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))
        return -2; /* Abort write, there is data that must be read */
      else
        USleep(100);

      if (status < 0)
        return -1;
    }
  }

  return length;
}

int freerdp_tls_set_alert_code(rdpTls* tls, int level, int description)
{
  WINPR_ASSERT(tls);
  tls->alertLevel = level;
  tls->alertDescription = description;
  return 0;
}

static BOOL tls_match_hostname(const char* pattern, const size_t pattern_length,
                               const char* hostname)
{
  if (strlen(hostname) == pattern_length)
  {
    if (_strnicmp(hostname, pattern, pattern_length) == 0)
      return TRUE;
  }

  if ((pattern_length > 2) && (pattern[0] == '*') && (pattern[1] == '.') &&
      ((strlen(hostname)) >= pattern_length))
  {
    const 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->context->settings;

  if (LB_NOREDIRECT & settings->RedirectionFlags)
    return FALSE;

  return settings->RedirectionFlags != 0;
}

static BOOL is_accepted(rdpTls* tls, const rdpCertificate* cert)
{
  WINPR_ASSERT(tls);
  WINPR_ASSERT(tls->context);
  WINPR_ASSERT(cert);
  rdpSettings* settings = tls->context->settings;
  WINPR_ASSERT(settings);

  FreeRDP_Settings_Keys_String keyAccepted = FreeRDP_AcceptedCert;
  FreeRDP_Settings_Keys_UInt32 keyLength = FreeRDP_AcceptedCertLength;

  if (tls->isGatewayTransport)
  {
    keyAccepted = FreeRDP_GatewayAcceptedCert;
    keyLength = FreeRDP_GatewayAcceptedCertLength;
  }
  else if (is_redirected(tls))
  {
    keyAccepted = FreeRDP_RedirectionAcceptedCert;
    keyLength = FreeRDP_RedirectionAcceptedCertLength;
  }

  const char* AcceptedKey = freerdp_settings_get_string(settings, keyAccepted);
  const UINT32 AcceptedKeyLength = freerdp_settings_get_uint32(settings, keyLength);

  if ((AcceptedKeyLength > 0) && AcceptedKey)
  {
    BOOL accepted = FALSE;
    size_t pemLength = 0;
    char* pem = freerdp_certificate_get_pem_ex(cert, &pemLength, FALSE);
    if (pem && (AcceptedKeyLength == pemLength))
    {
      if (memcmp(AcceptedKey, pem, AcceptedKeyLength) == 0)
        accepted = TRUE;
    }
    free(pem);
    if (accepted)
      return TRUE;
  }

  freerdp_settings_set_string(settings, keyAccepted, NULL);
  freerdp_settings_set_uint32(settings, keyLength, 0);

  return FALSE;
}

static BOOL compare_fingerprint(const char* fp, const char* hash, const rdpCertificate* cert,
                                BOOL separator)
{
  BOOL equal = 0;
  char* strhash = NULL;

  WINPR_ASSERT(fp);
  WINPR_ASSERT(hash);
  WINPR_ASSERT(cert);

  strhash = freerdp_certificate_get_fingerprint_by_hash_ex(cert, hash, separator);
  if (!strhash)
    return FALSE;

  equal = (_stricmp(strhash, fp) == 0);
  free(strhash);
  return equal;
}

static BOOL compare_fingerprint_all(const char* fp, const char* hash, const rdpCertificate* cert)
{
  WINPR_ASSERT(fp);
  WINPR_ASSERT(hash);
  WINPR_ASSERT(cert);
  if (compare_fingerprint(fp, hash, cert, FALSE))
    return TRUE;
  if (compare_fingerprint(fp, hash, cert, TRUE))
    return TRUE;
  return FALSE;
}

static BOOL is_accepted_fingerprint(const rdpCertificate* cert,
                                    const char* CertificateAcceptedFingerprints)
{
  WINPR_ASSERT(cert);

  BOOL rc = FALSE;
  if (CertificateAcceptedFingerprints)
  {
    char* context = NULL;
    char* copy = _strdup(CertificateAcceptedFingerprints);
    char* cur = strtok_s(copy, ",", &context);
    while (cur)
    {
      char* subcontext = NULL;
      const char* h = strtok_s(cur, ":", &subcontext);
      const char* fp = NULL;

      if (!h)
        goto next;

      fp = h + strlen(h) + 1;
      if (!fp)
        goto next;

      if (compare_fingerprint_all(fp, h, cert))
      {
        rc = TRUE;
        break;
      }
    next:
      cur = strtok_s(NULL, ",", &context);
    }
    free(copy);
  }

  return rc;
}

static BOOL accept_cert(rdpTls* tls, const rdpCertificate* cert)
{
  WINPR_ASSERT(tls);
  WINPR_ASSERT(tls->context);
  WINPR_ASSERT(cert);

  FreeRDP_Settings_Keys_String id = FreeRDP_AcceptedCert;
  FreeRDP_Settings_Keys_UInt32 lid = FreeRDP_AcceptedCertLength;

  rdpSettings* settings = tls->context->settings;
  WINPR_ASSERT(settings);

  if (tls->isGatewayTransport)
  {
    id = FreeRDP_GatewayAcceptedCert;
    lid = FreeRDP_GatewayAcceptedCertLength;
  }
  else if (is_redirected(tls))
  {
    id = FreeRDP_RedirectionAcceptedCert;
    lid = FreeRDP_RedirectionAcceptedCertLength;
  }

  size_t pemLength = 0;
  char* pem = freerdp_certificate_get_pem_ex(cert, &pemLength, FALSE);

  BOOL rc = FALSE;
  if (freerdp_settings_set_string_len(settings, id, pem, pemLength))
    rc = freerdp_settings_set_uint32(settings, lid, pemLength);
  free(pem);
  return rc;
}

static BOOL tls_extract_full_pem(const rdpCertificate* cert, BYTE** PublicKey,
                                 size_t* PublicKeyLength)
{
  if (!cert || !PublicKey)
    return FALSE;
  *PublicKey = (BYTE*)freerdp_certificate_get_pem(cert, PublicKeyLength);
  return *PublicKey != NULL;
}

int tls_verify_certificate(rdpTls* tls, const rdpCertificate* cert, const char* hostname,
                           UINT16 port)
{
  int match = 0;
  size_t length = 0;
  BOOL certificate_status = 0;
  char* common_name = NULL;
  size_t common_name_length = 0;
  char** dns_names = 0;
  size_t dns_names_count = 0;
  size_t* dns_names_lengths = NULL;
  int verification_status = -1;
  BOOL hostname_match = FALSE;
  rdpCertificateData* certificate_data = NULL;
  BYTE* pemCert = NULL;
  DWORD flags = VERIFY_CERT_FLAG_NONE;
  freerdp* instance = NULL;

  WINPR_ASSERT(tls);
  WINPR_ASSERT(tls->context->settings);

  instance = (freerdp*)tls->context->settings->instance;
  WINPR_ASSERT(instance);

  if (freerdp_shall_disconnect_context(instance->context))
    return -1;

  if (!tls_extract_full_pem(cert, &pemCert, &length))
    goto end;

  /* Check, if we already accepted this key. */
  if (is_accepted(tls, cert))
  {
    verification_status = 1;
    goto end;
  }

  if (is_accepted_fingerprint(cert, tls->context->settings->CertificateAcceptedFingerprints))
  {
    verification_status = 1;
    goto end;
  }

  if (tls->isGatewayTransport || is_redirected(tls))
    flags |= VERIFY_CERT_FLAG_LEGACY;

  if (tls->isGatewayTransport)
    flags |= VERIFY_CERT_FLAG_GATEWAY;

  if (is_redirected(tls))
    flags |= VERIFY_CERT_FLAG_REDIRECT;

  /* Certificate management is done by the application */
  if (tls->context->settings->ExternalCertificateManagement)
  {
    if (instance->VerifyX509Certificate)
      verification_status =
          instance->VerifyX509Certificate(instance, pemCert, length, hostname, port, flags);
    else
      WLog_ERR(TAG, "No VerifyX509Certificate callback registered!");

    if (verification_status > 0)
      accept_cert(tls, cert);
    else if (verification_status < 0)
    {
      WLog_ERR(TAG, "VerifyX509Certificate failed: (length = %" PRIuz ") status: [%d] %s",
               length, verification_status, pemCert);
      goto end;
    }
  }
  /* ignore certificate verification if user explicitly required it (discouraged) */
  else if (tls->context->settings->IgnoreCertificate)
    verification_status = 1; /* success! */
  else if (!tls->isGatewayTransport && (tls->context->settings->AuthenticationLevel == 0))
    verification_status = 1; /* success! */
  else
  {
    /* if user explicitly specified a certificate name, use it instead of the hostname */
    if (!tls->isGatewayTransport && tls->context->settings->CertificateName)
      hostname = tls->context->settings->CertificateName;

    /* attempt verification using OpenSSL and the ~/.freerdp/certs certificate store */
    certificate_status = freerdp_certificate_verify(
        cert, freerdp_certificate_store_get_certs_path(tls->certificate_store));
    /* verify certificate name match */
    certificate_data = freerdp_certificate_data_new(hostname, port, cert);
    if (!certificate_data)
      goto end;
    /* extra common name and alternative names */
    common_name = freerdp_certificate_get_common_name(cert, &common_name_length);
    dns_names = freerdp_certificate_get_dns_names(cert, &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 (size_t 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 = 1; /* success! */

    if (!hostname_match)
      flags |= VERIFY_CERT_FLAG_MISMATCH;

    /* verification could not succeed with OpenSSL, use known_hosts file and prompt user for
     * manual verification */
    if (!certificate_status || !hostname_match)
    {
      DWORD accept_certificate = 0;
      size_t pem_length = 0;
      char* issuer = freerdp_certificate_get_issuer(cert);
      char* subject = freerdp_certificate_get_subject(cert);
      char* pem = freerdp_certificate_get_pem(cert, &pem_length);

      if (!pem)
        goto end;

      /* search for matching entry in known_hosts file */
      match =
          freerdp_certificate_store_contains_data(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);

        {
          char* efp = freerdp_certificate_get_fingerprint(cert);
          tls_print_new_certificate_warn(tls->certificate_store, hostname, port, efp);
          free(efp);
        }

        /* Automatically accept certificate on first use */
        if (tls->context->settings->AutoAcceptCertificate)
        {
          WLog_INFO(TAG, "No certificate stored, automatically accepting.");
          accept_certificate = 1;
        }
        else if (tls->context->settings->AutoDenyCertificate)
        {
          WLog_INFO(TAG, "No certificate stored, automatically denying.");
          accept_certificate = 0;
        }
        else if (instance->VerifyX509Certificate)
        {
          int rc = instance->VerifyX509Certificate(instance, pemCert, pem_length,
                                                   hostname, port, flags);

          if (rc == 1)
            accept_certificate = 1;
          else if (rc > 1)
            accept_certificate = 2;
          else
            accept_certificate = 0;
        }
        else if (instance->VerifyCertificateEx)
        {
          const BOOL use_pem = freerdp_settings_get_bool(
              tls->context->settings, FreeRDP_CertificateCallbackPreferPEM);
          char* fp = NULL;
          DWORD cflags = flags;
          if (use_pem)
          {
            cflags |= VERIFY_CERT_FLAG_FP_IS_PEM;
            fp = pem;
          }
          else
            fp = freerdp_certificate_get_fingerprint(cert);
          accept_certificate = instance->VerifyCertificateEx(
              instance, hostname, port, common_name, subject, issuer, fp, cflags);
          if (!use_pem)
            free(fp);
        }
#if defined(WITH_FREERDP_DEPRECATED)
        else if (instance->VerifyCertificate)
        {
          char* fp = freerdp_certificate_get_fingerprint(cert);

          WLog_WARN(TAG, "The VerifyCertificate callback is deprecated, migrate your "
                         "application to VerifyCertificateEx");
          accept_certificate = instance->VerifyCertificate(instance, common_name, subject,
                                                           issuer, fp, !hostname_match);
          free(fp);
        }
#endif
      }
      else if (match == -1)
      {
        rdpCertificateData* stored_data =
            freerdp_certificate_store_load_data(tls->certificate_store, hostname, port);
        /* entry was found in known_hosts file, but fingerprint does not match. ask user
         * to use it */
        {
          char* efp = freerdp_certificate_get_fingerprint(cert);
          tls_print_certificate_error(tls->certificate_store, stored_data, hostname, port,
                                      efp);
          free(efp);
        }

        if (!stored_data)
          WLog_WARN(TAG, "Failed to get certificate entry for %s:%" PRIu16 "", hostname,
                    port);

        if (tls->context->settings->AutoDenyCertificate)
        {
          WLog_INFO(TAG, "No certificate stored, automatically denying.");
          accept_certificate = 0;
        }
        else if (instance->VerifyX509Certificate)
        {
          const int rc =
              instance->VerifyX509Certificate(instance, pemCert, pem_length, hostname,
                                              port, flags | VERIFY_CERT_FLAG_CHANGED);

          if (rc == 1)
            accept_certificate = 1;
          else if (rc > 1)
            accept_certificate = 2;
          else
            accept_certificate = 0;
        }
        else if (instance->VerifyChangedCertificateEx)
        {
          DWORD cflags = flags | VERIFY_CERT_FLAG_CHANGED;
          const char* old_subject = freerdp_certificate_data_get_subject(stored_data);
          const char* old_issuer = freerdp_certificate_data_get_issuer(stored_data);
          const char* old_fp = freerdp_certificate_data_get_fingerprint(stored_data);
          const char* old_pem = freerdp_certificate_data_get_pem(stored_data);
          const BOOL fpIsAllocated =
              !old_pem ||
              !freerdp_settings_get_bool(tls->context->settings,
                                         FreeRDP_CertificateCallbackPreferPEM);
          char* fp = NULL;
          if (!fpIsAllocated)
          {
            cflags |= VERIFY_CERT_FLAG_FP_IS_PEM;
            fp = pem;
            old_fp = old_pem;
          }
          else
          {
            fp = freerdp_certificate_get_fingerprint(cert);
          }
          accept_certificate = instance->VerifyChangedCertificateEx(
              instance, hostname, port, common_name, subject, issuer, fp, old_subject,
              old_issuer, old_fp, cflags);
          if (fpIsAllocated)
            free(fp);
        }
#if defined(WITH_FREERDP_DEPRECATED)
        else if (instance->VerifyChangedCertificate)
        {
          char* fp = freerdp_certificate_get_fingerprint(cert);
          const char* old_subject = freerdp_certificate_data_get_subject(stored_data);
          const char* old_issuer = freerdp_certificate_data_get_issuer(stored_data);
          const char* old_fingerprint =
              freerdp_certificate_data_get_fingerprint(stored_data);

          WLog_WARN(TAG, "The VerifyChangedCertificate callback is deprecated, migrate "
                         "your application to VerifyChangedCertificateEx");
          accept_certificate = instance->VerifyChangedCertificate(
              instance, common_name, subject, issuer, fp, old_subject, old_issuer,
              old_fingerprint);
          free(fp);
        }
#endif

        freerdp_certificate_data_free(stored_data);
      }
      else if (match == 0)
        accept_certificate = 2; /* success! */

      /* Save certificate or do a simple accept / reject */
      switch (accept_certificate)
      {
        case 1:

          /* user accepted certificate, add entry in known_hosts file */
          verification_status = freerdp_certificate_store_save_data(
                                    tls->certificate_store, certificate_data)
                                    ? 1
                                    : -1;
          break;

        case 2:
          /* user did accept temporaty, do not add to known hosts file */
          verification_status = 1;
          break;

        default:
          /* user did not accept, abort and do not add entry in known_hosts file */
          verification_status = -1; /* failure! */
          break;
      }

      free(issuer);
      free(subject);
      free(pem);
    }

    if (verification_status > 0)
      accept_cert(tls, cert);
  }

end:
  freerdp_certificate_data_free(certificate_data);
  free(common_name);
  freerdp_certificate_free_dns_names(dns_names_count, dns_names_lengths, dns_names);
  free(pemCert);
  return verification_status;
}

void tls_print_new_certificate_warn(rdpCertificateStore* store, const char* hostname, UINT16 port,
                                    const char* fingerprint)
{
  char* path = freerdp_certificate_store_get_cert_path(store, hostname, port);

  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.", path);
  WLog_ERR(TAG, "Host key for %s has changed and you have requested strict checking.", hostname);
  WLog_ERR(TAG, "Host key verification failed.");

  free(path);
}

void tls_print_certificate_error(rdpCertificateStore* store, rdpCertificateData* stored_data,
                                 const char* hostname, UINT16 port, const char* fingerprint)
{
  char* path = freerdp_certificate_store_get_cert_path(store, hostname, port);

  WLog_ERR(TAG, "New host key for %s:%" PRIu16, hostname, port);
  WLog_ERR(TAG, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
  WLog_ERR(TAG, "@    WARNING: NEW HOST IDENTIFICATION!     @");
  WLog_ERR(TAG, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");

  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.", path);

  free(path);
}

void tls_print_certificate_name_mismatch_error(const char* hostname, UINT16 port,
                                               const char* common_name, char** alt_names,
                                               size_t alt_names_count)
{
  WINPR_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)
  {
    WINPR_ASSERT(NULL != alt_names);
    WLog_ERR(TAG, "Alternative names:");

    for (size_t index = 0; index < alt_names_count; index++)
    {
      WINPR_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* freerdp_tls_new(rdpContext* context)
{
  rdpTls* tls = NULL;
  tls = (rdpTls*)calloc(1, sizeof(rdpTls));

  if (!tls)
    return NULL;

  tls->context = context;

  if (!freerdp_settings_get_bool(tls->context->settings, FreeRDP_ServerMode))
  {
    tls->certificate_store = freerdp_certificate_store_new(tls->context->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 freerdp_tls_free(rdpTls* tls)
{
  if (!tls)
    return;

  tls_reset(tls);

  if (tls->certificate_store)
  {
    freerdp_certificate_store_free(tls->certificate_store);
    tls->certificate_store = NULL;
  }

  free(tls);
}

Coverage Report

Created: 2024-09-08 06:20