I currently am trying to implement mutual TLS authentication between a client and a server. I'm running into an SSL error and it is not very descriptive. StackOverflow also does not have many questions related to it since most of the time it is a one-way TLS on the internet. However, from what I've seen, this error occurs because something is wrong with the client certificate, so below I have attached information relevant to that. If that is not the case, please let me know.
Generating Client Cert
My client's cnf(foo.config) looks like(with replacing all the sensitive information):
[ req ]
default_bits = 2048
default_md = sha256
prompt = no
req_extensions = req_ext
distinguished_name = dn
encrypt_key = no
[ dn ]
O=Bar
OU=User
[email protected]
[ req_ext ]
subjectAltName = email:[email protected]
nsCertType = client, email, objsign
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
I pass in this config file using openssl to create a csr:
openssl req -new -sha256 -key foo.key -out foo.csr -config foo.config
And then I send it to an infrastructure management API internally to sign the x509 certificate. I save the client certificate as foo.cert(it contains the trust chain up to the CA).
How my client sends the cert
When I send a urllib open request to my server, I send the ssl context with my HTTPSConnection:
... # Inside some handler code
context = ssl.create_default_context(purpose=ssl.Purpose.SERVER_AUTH,
cafile=ROOT_CA)
context.load_cert_chain(certfile=CERT_DEST, keyfile=KEY_DEST)
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
return http.client.HTTPSConnection(host, context=context)
How my flask server sets up
When my testing flask server takes in the ssl context like so:
executor = Flask(__name__)
context = ssl.create_default_context(purpose=ssl.Purpose.CLIENT_AUTH, cafile=TEST_CA_CERT)
context.load_cert_chain(certfile=TEST_CERT, keyfile=TEST_KEY)
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = False
executor.run(host=host, port=port, ssl_context=context)
It sets up its own certificates an key files. It also sets up client authentication requests.
Full error traceback
Upon runtime, during a call, I get this traceback(replacing all sensitive information):
Traceback (most recent call last):
File "/auto/foo/python3-rhel6/lib/python3.6/urllib/request.py", line 1318, in do_open
encode_chunked=req.has_header('Transfer-encoding'))
File "/auto/foo/python3-rhel6/lib/python3.6/http/client.py", line 1239, in request
self._send_request(method, url, body, headers, encode_chunked)
File "/auto/foo/python3-rhel6/lib/python3.6/http/client.py", line 1285, in _send_request
self.endheaders(body, encode_chunked=encode_chunked)
File "/auto/foo/python3-rhel6/lib/python3.6/http/client.py", line 1234, in endheaders
self._send_output(message_body, encode_chunked=encode_chunked)
File "/auto/foo/python3-rhel6/lib/python3.6/http/client.py", line 1026, in _send_output
self.send(msg)
File "/auto/foo/python3-rhel6/lib/python3.6/http/client.py", line 964, in send
self.connect()
File "/auto/foo/python3-rhel6/lib/python3.6/http/client.py", line 1400, in connect
server_hostname=server_hostname)
File "/auto/foo/python3-rhel6/lib/python3.6/ssl.py", line 407, in wrap_socket
_context=self, _session=session)
File "/auto/foo/python3-rhel6/lib/python3.6/ssl.py", line 814, in __init__
self.do_handshake()
File "/auto/foo/python3-rhel6/lib/python3.6/ssl.py", line 1068, in do_handshake
self._sslobj.do_handshake()
File "/auto/foo/python3-rhel6/lib/python3.6/ssl.py", line 689, in do_handshake
self._sslobj.do_handshake()
ssl.SSLError: [SSL: SSLV3_ALERT_UNSUPPORTED_CERTIFICATE] sslv3 alert unsupported certificate (_ssl.c:833)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "./bar.py", line 375, in <module>
start(args, overrides, threadlock)
File "./bar.py", line 332, in start
approved, alloc_message = Executor.approve(flow.the_portal.inst)
File "/home/myuser/dev/bar/Executor.py", line 638, in approve
with opener.open(request, json_request) as response:
File "/auto/foo/python3-rhel6/lib/python3.6/urllib/request.py", line 526, in open
response = self._open(req, data)
File "/auto/foo/python3-rhel6/lib/python3.6/urllib/request.py", line 544, in _open
'_open', req)
File "/auto/foo/python3-rhel6/lib/python3.6/urllib/request.py", line 504, in _call_chain
result = func(*args)
File "/home/myuser/dev/bar/Auth.py", line 77, in https_open
return self.do_open(self.getConnection, req)
File "/auto/foo/python3-rhel6/lib/python3.6/urllib/request.py", line 1320, in do_open
raise URLError(err)
urllib.error.URLError: <urlopen error [SSL: SSLV3_ALERT_UNSUPPORTED_CERTIFICATE] sslv3 alert unsupported certificate (_ssl.c:833)>
If more information is required, please don't hesitate to let me know. Any help would be appreciated.
EDIT: Here's the certificate (in redacted form):
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
...
Signature Algorithm: sha256WithRSAEncryption
Issuer: DC=com, DC=foo, CN=Foo Issuing CA - XXX
Validity
Not Before: ... 2018 GMT
Not After : ... GMT
Subject: O=Bar, OU=User, [email protected]
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
...
X509v3 extensions:
X509v3 Key Usage:
Key Encipherment, Data Encipherment
X509v3 Subject Alternative Name:
email:[email protected]
X509v3 Subject Key Identifier:
...
X509v3 Authority Key Identifier:
...
X509v3 CRL Distribution Points:
Full Name:
...
Authority Information Access:
CA Issuers - ...
CA Issuers - ...
X509v3 Extended Key Usage:
TLS Web Server Authentication, TLS Web Client Authentication
Verifying this file with my cert bundle says:
openssl verify -CAfile /.../certification_bundle.pem foo.cert
foo.cert: OK
I am using OpenSSL v.1.0.1e-fips. This should support TLSv1.2.
openssl x509 -text -in foo.cert, maybe redacting some details)? – Steffen Ullrich