Question

我有一个客户端和一个服务器试图相互进行身份验证并启动TLS连接。我现在使用的证书是自签名的。

在服务器代码中，我设置了SSL_VERIFY_FAIL_IF_NO_PEER_CERT。握手成功，但SSL_get_peer_certificate在服务器端返回NULL指针。如果客户没有返回证书，为什么握手不会失败？

如果我在服务器端注释掉SSL_get_peer_certificate检查，则客户端和服务器会进行连接并能够进行通信，但它不是TLS连接。当我看着他们通过wireshark交换数据包时，我只看到TCP流量。

服务器代码：

BIO *acceptTLSConnection(char *port) {

  BIO *sbio, *bbio, *acpt = NULL;
  SSL_CTX *ctx = NULL;
  SSL *ssl = NULL;

  SSL_library_init();

  ctx = SSL_CTX_new(TLSv1_server_method());

  SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER|SSL_VERIFY_FAIL_IF_NO_PEER_CERT, NULL);

  if(!SSL_CTX_use_certificate_file(ctx,"servercert.pem",SSL_FILETYPE_PEM)
    || !SSL_CTX_use_PrivateKey_file(ctx,"serverkey.pem",SSL_FILETYPE_PEM)
    || !SSL_CTX_check_private_key(ctx)) {
    ERR_print_errors_fp(stderr);
    fatalError("Error setting up SSL_CTX.");
  }

  if(!SSL_CTX_load_verify_locations(ctx, "clientcert.pem", NULL))
    fatalError("Could not load trusted CA certificates.");

  sbio=BIO_new_ssl(ctx,0);

  BIO_get_ssl(sbio, &ssl);

  if(!ssl) {
    fatalError("Can't locate BIO SSL pointer.");
  }

  SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);

  bbio = BIO_new(BIO_f_buffer());
  sbio = BIO_push(bbio, sbio);

  acpt=BIO_new_accept(port);
  BIO_set_accept_bios(acpt,sbio);

  /* Setup accept BIO */
  if(BIO_do_accept(acpt) <= 0) {
    ERR_print_errors_fp(stderr);
    fatalError("Error in setting up accept BIO");
  }

  /* Now wait for incoming connection */
  if(BIO_do_accept(acpt) <= 0) {
    ERR_print_errors_fp(stderr);
    fatalError("Error in connection");
  }

  sbio = BIO_pop(acpt);
  BIO_free_all(acpt);

  if(BIO_do_handshake(sbio) <= 0) {
    ERR_print_errors_fp(stderr);
    fatalError("Error in SSL handshake");
  }

  /* Verify a client certificate was presented during the negotiation */
  X509* cert = SSL_get_peer_certificate(ssl);
  if(cert) { X509_free(cert); } /* Free immediately */
  if(NULL == cert) fatalError("Client did not present a cert during handshake.");

  /* Verify the result of chain verification */
  int res = SSL_get_verify_result(ssl);
  if(!(X509_V_OK == res)) fatalError("Cert presented by client couldn't be verified.");

  return sbio;
}

客户代码：

BIO *makeTLSConnection(char *servIP, char *servPort) {

  char *servLoc = calloc(strlen(servIP) + strlen(servPort) + 2, sizeof(char));
  strcat(servLoc, servIP);
  strcat(servLoc, ":");
  strcat(servLoc, servPort);

  BIO *sbio = NULL;
  SSL_CTX *ctx = NULL;
  SSL *ssl = NULL;

  SSL_library_init();

  ctx = SSL_CTX_new(TLSv1_client_method());

  SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);

  if(!SSL_CTX_use_certificate_file(ctx,"clientcert.pem",SSL_FILETYPE_PEM)
    || !SSL_CTX_use_PrivateKey_file(ctx,"clientkey.pem",SSL_FILETYPE_PEM)
    || !SSL_CTX_check_private_key(ctx)) {
    ERR_print_errors_fp(stderr);
    fatalError("Error setting up SSL_CTX.");
  }

  if(!SSL_CTX_load_verify_locations(ctx, "servercert.pem", NULL))
    fatalError("Could not load trusted CA certificates.");

  sbio = BIO_new_ssl_connect(ctx);

  BIO_get_ssl(sbio, &ssl);

  if(!ssl) {
    fatalError("Can't locate SSL pointer.");
  }

  BIO_set_conn_hostname(sbio, servLoc);

  if(BIO_do_connect(sbio) <= 0) {
    ERR_print_errors_fp(stderr);
    fatalError("Error connecting to server.");
  }

  if(BIO_do_handshake(sbio) <= 0) {
    ERR_print_errors_fp(stderr);
    fatalError("Error establishing SSL connection.");
  }

  /* Verify a server certificate was presented during the negotiation */
  X509* cert = SSL_get_peer_certificate(ssl);
  if(cert) { X509_free(cert); } /* Free immediately */
  if(NULL == cert) fatalError("Server did not present a cert during handshake.");

  /* Verify the result of chain verification */
  int res = SSL_get_verify_result(ssl);
  if(!(X509_V_OK == res)) fatalError("Cert presented by server couldn't be verified.");

  return sbio;
}

Answer 1

您似乎错过了对服务器上SSL_CTX_use_certificate_chain_file和SSL_CTX_set_client_CA_list的调用。我相信SSL_CTX_set_client_CA_list触发机器执行客户端身份验证（即，它在交换期间从7.4.6节中的RFC中引出ClientCertificate message。）

如果SSL_CTX_set_client_CA_list导致您正在寻找失败，那么我倾向于相信它是OpenSSL库中的一个错误。在服务器上指定SSL_VERIFY_PEER和SSL_VERIFY_FAIL_IF_NO_PEER_CERT时应该会失败，因为这就是文档所说的内容。

另请参阅OpenSSL Users邮件列表中的Is verification supposed to fail with SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT without SSL_CTX_set_client_CA_list。它是对这个问题的回应。

另见Testing SSL/TLS Client Authentication with OpenSSL和OpenSSL client not sending client certificate。

TLS服务器无法从客户端接收证书，无法终止握手

1 个答案: