对客户端证书URL的OpenSSL支持

Question

我试图确定OpenSSL库是否支持Client Certificate URLs from RFC 4366。我在OpenSSL文档中找不到任何信息。

在文件tls.h我可以看到以下定义：

/* ExtensionType values from RFC3546/RFC4366/RFC6066 */ 
# define TLSEXT_TYPE_server_name     0 
# define TLSEXT_TYPE_max_fragment_length   1 
# define TLSEXT_TYPE_client_certificate_url  2 
# define TLSEXT_TYPE_trusted_ca_keys    3 
# define TLSEXT_TYPE_truncated_hmac    4 
# define TLSEXT_TYPE_status_request    5 

也有使用客户端扩展的方法：

int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type, 
            custom_ext_add_cb add_cb, 
            custom_ext_free_cb free_cb, 
            void *add_arg, 
            custom_ext_parse_cb parse_cb, 
            void *parse_arg); 

我看了在OpenSSL的来源和TLSEXT_TYPE_client_certificate_url是仅用于s_cb.c作为回调支持：

void MS_CALLBACK tlsext_cb(SSL *s, int client_server, int type, 
        unsigned char *data, int len, 
        void *arg) 
{ 
    BIO *bio = arg; 
    char *extname; 

    switch(type) 
    { 
    case TLSEXT_TYPE_server_name: 
    extname = "server name"; 
    break; 

    case TLSEXT_TYPE_client_certificate_url: 
    extname = "client certificate URL"; 
    break; 

    (...) 

    default: 
    extname = "unknown"; 
    break; 

    } 

    BIO_printf(bio, "TLS %s extension \"%s\" (id=%d), len=%d\n", 
     client_server ? "server": "client", 
     extname, type, len); 
    BIO_dump(bio, (char *)data, len); 
    (void)BIO_flush(bio); 
} 

当我搜索TLSEXT_TYPE_server_name我可以看到有该标志 实例的文件t1_lib.c

unsigned char ssl_add_serverhello_tlsext(SSL s, unsigned char *buf, 
              unsigned char *limit) 
{ 
    int extdatalen = 0; 
    unsigned char *orig = buf; 
    unsigned char *ret = buf; 
# ifndef OPENSSL_NO_NEXTPROTONEG 
    int next_proto_neg_seen; 
# endif 

    /* 
    * don't add extensions for SSLv3, unless doing secure renegotiation 
    */ 
    if (s->version == SSL3_VERSION && !s->s3->send_connection_binding) 
     return orig; 

    ret += 2; 
    if (ret >= limit) 
     return NULL;   /this really never occurs, but .../

    if (!s->hit && s->servername_done == 1 
     && s->session->tlsext_hostname != NULL) { 
     if ((long)(limit - ret - 4) < 0) 
      return NULL; 

     s2n(TLSEXT_TYPE_server_name, ret); 
     s2n(0, ret); 

到如此地步，TLSEXT_TYPE_server_name扩展支持的使用它给我带来，但有大约TLSEXT_TYPE_client_certificate_url没有明确的信息。

Answer 1

不，这个扩展在任何OpenSSL版本中都不被支持。