crypto: hard-code tlsSocket.getCipher().version

This aligns the documentation with reality. This API never did what Node
claims it did.

The SSL_CIPHER_get_version function just isn't useful. In OpenSSL 1.0.2,
it always returned the string "TLSv1/SSLv3" for anything but SSLv2
ciphers, which Node does not support. Note how test-tls-multi-pfx.js
claims that ECDHE-ECDSA-AES256-GCM-SHA384 was added in TLSv1/SSLv3 which
is not true. That cipher is new as of TLS 1.2. The OpenSSL 1.0.2
implementation is:

char *SSL_CIPHER_get_version(const SSL_CIPHER *c)
{
    int i;

    if (c == NULL)
        return ("(NONE)");
    i = (int)(c->id >> 24L);
    if (i == 3)
        return ("TLSv1/SSLv3");
    else if (i == 2)
        return ("SSLv2");
    else
        return ("unknown");
}

In OpenSSL 1.1.0, SSL_CIPHER_get_version changed to actually behave as
Node documented it, but this changes the semantics of the function and
breaks tests. The cipher's minimum protocol version is not a useful
notion to return to the caller here, so just hardcode the string at
"TLSv1/SSLv3" and document it as legacy.

PR-URL: #16130
Backport-PR-URL: #18622
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>

doc/api/tls.md

@@ -558,12 +558,12 @@ Always returns `true`. This may be used to distinguish TLS sockets from regular
 added: v0.11.4
 -->
 
-Returns an object representing the cipher name and the SSL/TLS protocol version
-that first defined the cipher.
+Returns an object representing the cipher name. The `version` key is a legacy
+field which always contains the value `'TLSv1/SSLv3'`.
 
 For example: `{ name: 'AES256-SHA', version: 'TLSv1/SSLv3' }`
 
-See `SSL_CIPHER_get_name()` and `SSL_CIPHER_get_version()` in
+See `SSL_CIPHER_get_name()` in
 https://www.openssl.org/docs/man1.0.2/ssl/SSL_CIPHER_get_name.html for more
 information.
 

src/node_crypto.cc

@@ -2261,9 +2261,8 @@ void SSLWrap<Base>::GetCurrentCipher(const FunctionCallbackInfo<Value>& args) {
   Local<Object> info = Object::New(env->isolate());
   const char* cipher_name = SSL_CIPHER_get_name(c);
   info->Set(env->name_string(), OneByteString(args.GetIsolate(), cipher_name));
-  const char* cipher_version = SSL_CIPHER_get_version(c);
   info->Set(env->version_string(),
-            OneByteString(args.GetIsolate(), cipher_version));
+            OneByteString(args.GetIsolate(), "TLSv1/SSLv3"));
   args.GetReturnValue().Set(info);
 }