Getting SSL* is a little bit tricky and hacky, so you need to be careful as
libcurl doesn't provide a direct way to get OpenSSL handle
and discourages from using it directly, especially for SSL_read/SSL_write as
it may break how libcurl protocol filters work.
But if you really need to go that path and planning to use SSL* only for
extracting some certificate info,
then here are the steps which you can try:
1. Register SSL context callback function via CURLOPT_SSL_CTX_FUNCTION option
on the easy handle.
It will give you the ability to get SSL context (SSL_CTX*).
2. Once you have the SSL context, you can register SSL_VERIFY_PEER callback on
that context:
Like:
SSL_CTX_set_verify(ctx_, SSL_VERIFY_PEER, sslVerifyCallback);
3. In the SSL verify peer callback, you can get the SSL handle like:
static int sslVerifyCallback(int valid_sig, X509_STORE_CTX* ctx) {
auto ssl = (SSL*)(X509_STORE_CTX_get_ex_data(ctx,
SSL_get_ex_data_X509_STORE_CTX_idx()));
...
// Extract additional certificate info using OpenSSL API.
...
}
This is what I used in the past.
Again, use it on your own risk, as you will not get any support for that kind
of things.
Thanks,
Dmitry Karpov
-----Original Message-----
From: curl-library <[email protected]> On Behalf Of Patrick
Schlangen via curl-library
Sent: Monday, November 4, 2024 12:51 AM
To: libcurl development <[email protected]>
Cc: Patrick Schlangen <[email protected]>
Subject: [EXTERNAL] Get SSL handle after connection has been established
Hi,
I'd like to extract some information from the OpenSSL SSL* after connection
establishment. Is there any callback / libcurl option I can use for that?
Basically, I'd like to provide a callback which is invoked at about the point
where libcurl also performs the CERTINFO extraction.
Background: I'd like to extract the certificate expiration date, but without
the overhead of string parsing and all the other values captured by
CURLOPT_CERTINFO.
Thanks,
Patrick
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