As an update (still open three years later?...), it turns out that OpenSSH "certificates" also trigger this bug:
debug1: Offering RSA-CERT public key: /home/grawity/.ssh/id_global
debug2: we sent a publickey packet, wait for reply
[hangs]
Even the IdentitiesOnly option does not work here, as OpenSSH always tries <file>-cert.pub in addition to just <file> (it's documented in ssh_config with no option to disable).
Fortunately I was only testing the feature and can work around by removing ~/.ssh/*-cert.pub, but some other people wouldn't be so lucky.
As an update (still open three years later?...), it turns out that OpenSSH "certificates" also trigger this bug:
debug1: Offering RSA-CERT public key: /home/grawity/ .ssh/id_ global
debug2: we sent a publickey packet, wait for reply
[hangs]
Even the IdentitiesOnly option does not work here, as OpenSSH always tries <file>-cert.pub in addition to just <file> (it's documented in ssh_config with no option to disable).
Fortunately I was only testing the feature and can work around by removing ~/.ssh/*-cert.pub, but some other people wouldn't be so lucky.