How to get response SSL certificate from requests in python?

requests deliberately wraps up low-level stuff like this. Normally, the only thing you want to do is to verify that the certs are valid. To do that, just pass verify=True. If you want to use a non-standard cacert bundle, you can pass that too. For example:

resp = requests.get('https://example.com', verify=True, cert=['/path/to/my/ca.crt'])

Also, requests is primarily a set of wrappers around other libraries, mostly urllib3 and the stdlib’s http.client (or, for 2.x, httplib) and ssl.

Sometimes, the answer is just to get at the lower-level objects (e.g., resp.raw is the urllib3.response.HTTPResponse), but in many cases that’s impossible.

And this is one of those cases. The only objects that ever see the certs are an http.client.HTTPSConnection (or a urllib3.connectionpool.VerifiedHTTPSConnection, but that’s just a subclass of the former) and an ssl.SSLSocket, and neither of those exist anymore by the time the request returns. (As the name connectionpool implies, the HTTPSConnection object is stored in a pool, and may be reused as soon as it’s done; the SSLSocket is a member of the HTTPSConnection.)

So, you need to patch things so you can copy the data up the chain. It may be as simple as this:

HTTPResponse = requests.packages.urllib3.response.HTTPResponse
orig_HTTPResponse__init__ = HTTPResponse.__init__
def new_HTTPResponse__init__(self, *args, **kwargs):
    orig_HTTPResponse__init__(self, *args, **kwargs)
    try:
        self.peercert = self._connection.sock.getpeercert()
    except AttributeError:
        pass
HTTPResponse.__init__ = new_HTTPResponse__init__

HTTPAdapter = requests.adapters.HTTPAdapter
orig_HTTPAdapter_build_response = HTTPAdapter.build_response
def new_HTTPAdapter_build_response(self, request, resp):
    response = orig_HTTPAdapter_build_response(self, request, resp)
    try:
        response.peercert = resp.peercert
    except AttributeError:
        pass
    return response
HTTPAdapter.build_response = new_HTTPAdapter_build_response

That’s untested, so no guarantees; you may need to patch more than that.

Also, subclassing and overriding would probably be cleaner than monkeypatching (especially since HTTPAdapter was designed to be subclassed).

Or, even better, forking urllib3 and requests, modifying your fork, and (if you think this is legitimately useful) submitting pull requests upstream.

Anyway, now, from your code, you can do this:

resp.peercert

This will give you a dict with 'subject' and 'subjectAltName' keys, as returned by pyopenssl.WrappedSocket.getpeercert. If you instead want more information about the cert, try Christophe Vandeplas’s variant of this answer that lets you get an OpenSSL.crypto.X509 object. If you want to get the entire peer certificate chain, see GoldenStake’s answer.

Of course you may also want to pass along all the information necessary to verify the cert, but that’s even easier, because it already passes through the top level.