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我正在尝试将 PSK 与 mbedtls 库与 SGX 结合使用。如果没有 PSK，则连接可以正常工作。

这是相关的客户端代码：

mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_ssl_context ssl;
mbedtls_ssl_config conf;
mbedtls_x509_crt cacert;

mbedtls_net_init(&server_fd);
mbedtls_ssl_init(&ssl);
mbedtls_ssl_config_init(&conf);
mbedtls_x509_crt_init(&cacert);
mbedtls_ctr_drbg_init(&ctr_drbg);


mbedtls_entropy_init( &entropy );
if ((mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy, (const unsigned char*) pers, strlen(pers))) != 0) {
    mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
    ret = -1;
    break;
}

ret = mbedtls_x509_crt_parse(&cacert, (const unsigned char *) mbedtls_crt, mbedtls_crt_len);

if ((ret = mbedtls_net_connect(&server_fd, SERVER_NAME, SERVER_PORT, MBEDTLS_NET_PROTO_TCP )) != 0) {
    mbedtls_printf( " failed\n  ! mbedtls_net_connect returned %d\n\n", ret );
    break;
}

if ((ret = mbedtls_ssl_config_defaults(&conf,
                                       MBEDTLS_SSL_IS_CLIENT,
                                       MBEDTLS_SSL_TRANSPORT_STREAM,
                                       MBEDTLS_SSL_PRESET_DEFAULT)) != 0 )
{
    mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
    break;
}

mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );
mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
mbedtls_ssl_conf_dbg( &conf, my_debug, NULL );
mbedtls_ssl_conf_verify( &conf, my_verify, NULL );

const unsigned char psk_key[] = {
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
};
size_t psk_len = sizeof( psk_key );
const char psk_id[] = "Client_identity";

if ((ret = mbedtls_ssl_conf_psk(&conf, psk_key, psk_len,
                                (const unsigned char *) psk_id,
                                strlen(psk_id))) != 0 )
{
    mbedtls_printf( "  mbedtls_ssl_conf_psk returned %d\n\n", ret );
    break;
}



if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
{
    mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned %d\n\n", ret );
    break;
}

if( ( ret = mbedtls_ssl_set_hostname( &ssl, "mbed TLS Server 1" ) ) != 0 )
{
    mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n", ret );
    break;
}

mbedtls_ssl_set_bio( &ssl, &server_fd, mbedtls_net_send, mbedtls_net_recv, NULL );

mbedtls_printf( " ok\n" );
mbedtls_printf( "  . Performing the SSL/TLS handshake..." );

while ((ret = mbedtls_ssl_handshake(&ssl)) != 0) {
    if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret);
        break;
    }
}


....

我的 openssl 测试服务器运行：

 openssl s_server -accept 4433 -cert server.pem -psk 000102030405060708090a0b0c0d0e0f -psk_hint Client_identity -cipher PSK-AES256-CBC-SHA -debug

服务器接收连接并交换 PSK 消息，但在解密点我收到以下错误：

 error:1408F119:SSL routines:SSL3_GET_RECORD:decryption failed or bad record mac:s3_pkt.c:532:

我也尝试将其更改-cipher PSK-AES256-CBC-SHA为不同的密码，但仍然是相同的错误。当完全省略密码时，连接有效，但不执行 PSK！？

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1 回答 1

2

经过几次尝试，我设法找到了这个问题的根本原因。失败的原因是从 openssl s_server 日志中的以下日志中暗示的（我使用了 -debug -tlsextdebug）：

创建 PSK len=15

这源自openssl 代码 但是，您使用的密钥是 16 个字节。当我将 psk 更改为 "010102030405060708090a0b0c0d0e0f" 时，TLS 连接有效，日志如下：

创建 PSK len=16

我相信这个失败的根本原因是在OPENSSL_hexstr2buf()implementation中，它忽略了最重要的零，从而返回了错误的密钥长度。

于 2018-02-13T16:10:55.463 回答