为何PHP中howsmyssl.com TLS检测结果与cURL STDERR输出不一致？

为了给客户提供支持，我需要检查API请求使用的TLS版本。我用PHP脚本通过cURL向https://www.howsmyssl.com/a/check发送请求，接口返回结果显示使用TLS 1.3，但开启VERBOSE=true后记录的STDERR输出却显示使用TLSv1.2，这是为什么？

cURL响应结果 #

{"given_cipher_suites":["TLS_AES_256_GCM_SHA384","TLS_CHACHA20_POLY1305_SHA256","TLS_AES_128_GCM_SHA256","TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384","TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384","TLS_DHE_RSA_WITH_AES_256_GCM_SHA384","TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256","TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256","TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256","TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256","TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256","TLS_DHE_RSA_WITH_AES_128_GCM_SHA256","TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384","TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384","TLS_DHE_RSA_WITH_AES_256_CBC_SHA256","TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256","TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256","TLS_DHE_RSA_WITH_AES_128_CBC_SHA256","TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA","TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA","TLS_DHE_RSA_WITH_AES_256_CBC_SHA","TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA","TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA","TLS_DHE_RSA_WITH_AES_128_CBC_SHA","TLS_RSA_WITH_AES_256_GCM_SHA384","TLS_RSA_WITH_AES_128_GCM_SHA256","TLS_RSA_WITH_AES_256_CBC_SHA256","TLS_RSA_WITH_AES_128_CBC_SHA256","TLS_RSA_WITH_AES_256_CBC_SHA","TLS_RSA_WITH_AES_128_CBC_SHA","TLS_EMPTY_RENEGOTIATION_INFO_SCSV"],"ephemeral_keys_supported":true,"session_ticket_supported":false,"tls_compression_supported":false,"unknown_cipher_suite_supported":false,"beast_vuln":false,"able_to_detect_n_minus_one_splitting":false,"insecure_cipher_suites":{},"tls_version":"TLS 1.3","rating":"Probably Okay"}

cURL verbose日志（STDERR输出） #

*   Trying 34.71.45.200:443...
* Connected to www.howsmyssl.com (34.71.45.200) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305
* ALPN, server did not agree to a protocol
* Server certificate:
*  subject: CN=www.howsmyssl.com
*  start date: Oct 30 02:45:45 2022 GMT
*  expire date: Jan 28 02:45:44 2023 GMT
*  subjectAltName: host "www.howsmyssl.com" matched cert's "www.howsmyssl.com"
*  issuer: C=US; O=Let's Encrypt; CN=R3
*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.
> GET /a/check HTTP/1.1
Host: www.howsmyssl.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en; rv:1.9.0.13) Gecko/2009073022 Firefox/3.5.2
Accept: */*

* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Length: 1459
< Access-Control-Allow-Origin: *
< Connection: close
< Content-Type: application/json
< Date: Wed, 09 Nov 2022 08:08:44 GMT
< Strict-Transport-Security: max-age=631138519; includeSubdomains; preload
< 
* Closing connection 0

所用PHP代码 #

$out = fopen('php://temp', 'w+');
$curl = curl_init('https://www.howsmyssl.com/a/check');

curl_setopt_array($curl, array(
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_USERAGENT      => 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en; rv:1.9.0.13) Gecko/2009073022 Firefox/3.5.2',
    CURLOPT_SSL_VERIFYPEER => false,
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_VERBOSE        => true,
    CURLOPT_STDERR         => $out,
    //CURLOPT_SSLVERSION => CURL_SSLVERSION_MAX_TLSv1_2, //6 = 1.2 | 4 = 1.1.1m
));
$curl_result = curl_exec($curl);
if ($curl_result)
{
    Kint::dump($curl_result);
}

rewind($out);
curl_close($curl);
$TLS_logOutput = stream_get_contents($out);
Kint::dump($TLS_logOutput);

问题原因及解决办法 #

核心原因 #

日志显示和实际协议版本不符，是因为你的cURL或其依赖的OpenSSL版本不支持TLS 1.3的日志输出，导致verbose模块错误标记了协议版本，但实际握手已经成功协商为TLS 1.3。

验证依据 #

• howsmyssl的返回结果是服务器端直接检测到的握手协议版本，准确性更高，明确标注了"tls_version":"TLS 1.3"。
• 响应里的加密套件列表包含TLS 1.3专属套件（如TLS_AES_256_GCM_SHA384），这些套件只在TLS 1.3握手时才会被使用，进一步证明实际用的是TLS 1.3。

解决办法 #

1. 更新依赖版本：将cURL升级到7.66+、OpenSSL升级到1.1.1+，新版本已经修复了TLS 1.3的日志显示问题，verbose日志会正确输出TLS 1.3。
2. 以服务器检测结果为准：如果无法更新依赖，直接参考howsmyssl的返回结果，它比客户端日志更可靠。

内容的提问来源于stack exchange，提问作者mikexmagic