Git authentication not working when using RSA, but works if using ED25519

[dacucar]

Is it still possible to use RSA keys for SSH authentication in bitbucket?

I've been using bitbucket since a while back and I have been using a Yubikey+GPG+gpgagent to authenticate against my bitbucket repositories. One day, it suddenly stopped working while still working on other git cloud repository providers. Public key was the same and I tested on different computers.

After some investigation I realized that the problem was not the Yubikey or the fact that I was using `gpgagent`.

* If I generate a ssh-key with `ssh-keygen -t rsa` and I add the public key to my SSH keys, I can't use it for authentication.
* If I generate a ssh-key with `ssh-keygen -t ed25519` then everything works fine.

[Ben]

G'day!

The RSA SHA-1 hash algorithm is being quickly deprecated across operating systems and SSH clients because of various security vulnerabilities, with many of these technologies now outright denying the use of this algorithm. For example, here is a link to an announcement from OpenSSH mentioning the same:
https://www.openssh.com/txt/release-8.2 

In order to re-enable ssh-rsa support, inserting the following line into the affected SSH client's config file can re-enable this algorithm:

PubkeyAcceptedKeyTypes +ssh-rsa

Please note that this is not a recommended solution and we would recommend using ECDSA and ED25519 hash algorithms instead.

Cheers!

- Ben (Bitbucket Cloud Support)