[openssl-users] Hostname validation

[Serj]

Hi, Viktor.

I have some questions.
I didn't find docs on such functions as SSL_get0_param
Why there is no corresponding functions as SSL_set0_param in your code?
Where can I found documentation on functions operating with params?

I found only this code:
  X509_VERIFY_PARAM *param;
  param = X509_VERIFY_PARAM_new();
  X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_CRL_CHECK);
  SSL_CTX_set1_param(ctx, param);
  X509_VERIFY_PARAM_free(param);

here: https://www.openssl.org/docs/crypto/X509_VERIFY_PARAM_set_hostflags.html

But there is no any description how SSL_CTX_set1_param works! Does it clear all previous flags on CTX or "ORing" with them?
And there are no any docs on "GET" params functions!

For example, like docs on SSL_CTX_set_options,SSL_CTX_get_option,SSL_set_options,SSL_get_options.


--
Best Regards,

Serj

25.01.2015, 20:59, "Viktor Dukhovni" <openssl-users at dukhovni.org>:
> On Sun, Jan 25, 2015 at 07:43:14PM +0300, Serj wrote:
>>  What is the best way to make hostname validation?
>>
>>  1. http://wiki.openssl.org/index.php/Hostname_validation
>>  2. X509_check_host that was added in OpenSSL 1.1.0.
>
> The X509_check_host() interface is also available in OpenSSL 1.0.2
> released a few days ago
>
>     https://www.openssl.org/docs/crypto/X509_check_host.html
>
> (the documentation should be updated to note the earlier availability).
>
> Starting with 1.0.2, you can also ask OpenSSL to automatically
> perform hostname checks during the SSL handshake on the application's
> behalf:
>
>     https://www.openssl.org/docs/crypto/X509_VERIFY_PARAM_set_hostflags.html
>     https://www.openssl.org/docs/crypto/X509_VERIFY_PARAM_set1_host.html
>     https://www.openssl.org/docs/crypto/X509_VERIFY_PARAM_add1_host.html
>     https://www.openssl.org/docs/ssl/SSL_set_verify.html
>
> Sadly, we're still lacking documentation of SSL_get0_param() which
> is needed for a complete SSL hostname check recipe:
>
>         const char *servername;
>         SSL *ssl;
>         X509_VERIFY_PARAM *param;
>
>         servername = "www.example.com";
>         ssl = SSL_new(...);
>         param = SSL_get0_param(ssl);
>
>         /* Enable automatic hostname checks */
>         X509_VERIFY_PARAM_set_hostflags(param, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS);
>         X509_VERIFY_PARAM_set1_host(param, servername, 0);
>
>         /* Configure a non-zero callback if desired */
>         SSL_set_verify(ssl, SSL_VERIFY_PEER, 0);
>
>         /*
>          * Establish SSL connection, hostname should be checked
>          * automatically test with a hostname that should not match,
>          * the connection will fail (unless you specify a callback
>          * that returns despite the verification failure.  In that
>          * case SSL_get_verify_status() can expose the problem after
>          * connection completion.
>          */
>          ...
>>  I don't know does the first one support wildcards or no! Seems
>>  to be: how does Curl_cert_hostcheck work - is the answer, but I
>>  don't know how it works.
>
> Wildcard support is configured via the flags documented for X509_check_host(),
> the two most frequently useful are:
>
>         X509_CHECK_FLAG_NO_WILDCARDS
>         X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
>
> --
>         Viktor.
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