ssh Permission denied (publickey) after upgrade Fedora 33

问题

i have been trying many answers on this Stackoverlow questions same like i am asking now, but still can't resolve my problem, i am trying to clone by ssh but always got Permission denied (publickey)

when i run GIT_SSH_COMMAND="ssh -vvv" git clone git@bitbucket.org:myusername/my-api.git

debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: curve25519-sha256@libssh.org need=64 dh_need=64
debug1: kex: curve25519-sha256@libssh.org need=64 dh_need=64
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ssh-rsa SHA256:kkXQOXSRBEiUtuE8AikLLLwbHaxvSc0ojez9YXaGp2A
debug3: hostkeys_foreach: reading file "/home/alienwarepocket/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/alienwarepocket/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from bitbucket.org
debug3: hostkeys_foreach: reading file "/home/alienwarepocket/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/alienwarepocket/.ssh/known_hosts:3
debug3: load_hostkeys: loaded 1 keys from 18.205.93.2
debug1: Host 'bitbucket.org' is known and matches the RSA host key.
debug1: Found key in /home/alienwarepocket/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /home/alienwarepocket/.ssh/id_rsa RSA SHA256:ktMzaalYyvU9Ev1bgELXatabkUkdcT828O0PppnNiV4M explicit agent
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/alienwarepocket/.ssh/id_rsa RSA SHA256:ktMzaalYyvU9Ev1bgELXatabkUkdcT828O0PppnNiV4M explicit agent
debug1: send_pubkey_test: no mutual signature algorithm
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
git@bitbucket.org: Permission denied (publickey).
fatal: Could not read from remote repository.

after i upgrade Fedora 33, i got this issue, it was no issue on Fedora 32

回答1:

This could be related to "Changes/StrongCryptoSettings2 in Fedora33"

The changes for default policy are:

Keep only TLS 1.2 (and TLS 1.3 when available) as enabled protocols and move the TLS 1.x, x<=1 to legacy level.

Require finite field parameters (RSA, Diffie-Hellman) of 2048 and more in the default settings

Disable SHA1 support for use in signatures (X.509 certificates, TLS, IPSEC handshakes)

The "Upgrade/compatibility impact" section of the aforementioned link clearly mentions:

It may be that the new settings break software that connects to servers which utilize weak algorithms.
Compatibility can be obtained by switching the system to Fedora 32 policy level:
update-crypto-policies --set DEFAULT:FEDORA32

NOT RECOMMENDED though: if you can use an ed25519, this is better.

As mentioned in Peque's answer, you can add on your ~/.ssh/config an option initially found in sshd_config

 PubkeyAcceptedKeyTypes
         Specifies the key types that will be accepted for public key
         authentication as a list of comma-separated patterns.

So if you cannot use ed25519, you can, for one specific host, allow the use of id_rsa keys with:

Host aHost
    Hostname a.hostname.com
    PubkeyAcceptedKeyTypes +ssh-rsa

Finally: Double-check your permissions after upgrade:

~/.ssh is 775 drwxrwxr-x.
~/.ssh/id_rsa is 600 -rw-------.
~/.ssh/id_rsa.pub is 644 -rw-r--r--.
~/.ssh/authorized_keys on remote server is 600 -rw-------

But using ssh-keygen -t ed25519 keys seems to be recommended now.

回答2:

@VonC Is correct, I upgraded to fedora 33 and ran into this permission issue.

running the following command fixed it :

update-crypto-policies --set DEFAULT:FEDORA32

Thank you for sharing that article

回答3:

Instead of globally changing the crypto policies, it is better to downgrade security per-host.

You can update the configuration for the specific legacy host in your .ssh/config file by adding:

Host legacy.host
    PubkeyAcceptedKeyTypes +ssh-rsa

For more details, have a look at this discussion in Bugzilla.

来源：https://stackoverflow.com/questions/64640596/ssh-permission-denied-publickey-after-upgrade-fedora-33

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bitbucket

rsa

fedora