OpenSSH 7.7 gives warning

[ffes]

Recently OpenSSH on Cygwin was upgraded to 7.7 and now ssh-pageant gives this warning when any ssh process is invoked.

warning: agent returned different signature type ssh-rsa (expected rsa-sha2-512)

This warning was added in OpenSSH 7.7:

https://www.openssh.com/txt/release-7.7

• ssh(1): Warn when the agent returns a ssh-rsa (SHA1) signature when
  a rsa-sha2-256/512 signature was requested. This condition is possible
  when an old or non-OpenSSH agent is in use. bz#279

Some examples:

$ git pull
warning: agent returned different signature type ssh-rsa (expected rsa-sha2-512)
Already up to date.

$ ssh frank@host.example.com
warning: agent returned different signature type ssh-rsa (expected rsa-sha2-512)
Welcome to Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-116-generic x86_64)

When I close pageant and use the native openssh keys the warning is not shown.

[cuviper]

Thanks for the bug report, but I think this will have to be reported to PuTTY/Pageant itself. ssh-pageant only acts as a middle-man between the UNIX socket and Windows messages, but doesn't interpret or examine the actual agent packets at all.

[cuviper]

I can also reproduce this warning by connecting PuTTY to Fedora 28 (openssh-7.7p1-2.fc28.x86_64) with agent forwarding enabled, then ssh localhost within so that remote ssh talks to Pageant.

I'm closing this issue since ssh-pageant is not responsible for the content of the agent messages.

[cuviper]

Also FWIW, the referenced openssh bug is still open, so their behavior may yet change. PuTTY/Pageant is also mentioned in the comments.

https://bugzilla.mindrot.org/show_bug.cgi?id=2799

[cuviper]

Even further, ssh-agent from openssh-clients-7.4p1-16.el7.x86_64 triggers the same warning when forwarded to that F28 machine and the key is used.