Description of problem:
gnutls in fedora 33 can still connect to a server over TLS using SHA1 signature. It should be forbidden as per https://fedoraproject.org/wiki/Changes/StrongCryptoSettings2
Version-Release number of selected component (if applicable):
System was upgraded from fedora 32.
$ gnutls-cli -V espaceclient.axa.fr:443
Processed 154 CA certificate(s).
Connecting to '22.214.171.124:443'...
- Certificate type: X.509
- Got a certificate list of 3 certificates.
- Certificate info:
- Certificate info:
- Certificate info:
- Status: The certificate is trusted.
- Description: (TLS1.2-X.509)-(ECDHE-SECP256R1)-(RSA-SHA1)-(AES-256-GCM)
- Session ID: F8:F1:59:AD:06:1D:76:D1:B8:09:72:CF:62:5D:5C:C1:E4:4B:06:9D:2B:C5:BB:CA:21:47:3D:42:F8:6B:AA:B1
- Ephemeral EC Diffie-Hellman parameters
- Using curve: SECP256R1
- Curve size: 256 bits
- Version: TLS1.2
- Key Exchange: ECDHE-RSA
- Server Signature: RSA-SHA1
- Cipher: AES-256-GCM
- MAC: AEAD
- Options: safe renegotiation,
- Channel binding 'tls-unique': 2181e59d6a0fdac0bc6f862c
- Handshake was completed
- Simple Client Mode:
GET / HTTP/1.1
User-Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:82.0) Gecko/20100101 Firefox/82.0- Sent: 15 bytes
- Sent: 26 bytes
- Sent: 89 bytes
- Sent: 1 bytes
- Received: HTTP/1.1 406 Not Acceptable
Content-Type: text/html; charset=utf-8
It's possible to connect to the server and get an answer from it even though we can see that the server signature is RSA-SHA1.
The session should be dropped. Firefox cannot connect with the reason SSL_ERROR_UNSUPPORTED_HASH_ALGORITHM, openssl cannot connect either:
$ openssl s_client -connect espaceclient.axa.fr:443
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert Global Root G2
depth=1 C = US, O = DigiCert Inc, CN = DigiCert EV RSA CA G2
depth=0 businessCategory = Private Organization, jurisdictionC = FR, jurisdictionST = \C3\8Ele-de-France, jurisdictionL = Paris, serialNumber = 572 093 920, C = FR, L = PARIS, O = AXA, OU = AXA, CN = espaceclient.axa.fr
139840200582976:error:1414D172:SSL routines:tls12_check_peer_sigalg:wrong signature type:ssl/t1_lib.c:1185:
I can confirm that on a clean Fedora 33 install, it also connects with
[root@fedora33 ~]# update-crypto-policies --show
[root@fedora33 ~]# grep RSA-SHA1 /etc/crypto-policies/back-ends/gnutls.config
insecure-sig = RSA-SHA1
This is caused by the special case introduced by:
Despite the comment, the algorithm check is done after the addition of GNUTLS_VERIFY_ALLOW_BROKEN. The commit log is not very clear about the intention as well.
This message is a reminder that Fedora 33 is nearing its end of life.
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