On 2/7/21 1:09 PM, Brian Candler wrote:
Does the ssh-agent protocol allow adding a certificate for a private key
which it already has? The idea is to issue a certificate for a key the
agent already has, to avoid the entropy drain of generating a new key.
https://tools.ietf.org/html/draft-miller-ssh-agent-04 shows private
keys, and doesn't mention certificates at all. However it does say:
"Typically only the public components of any keys supported on a
hardware token will be loaded into an agent" - which suggests that the
SSH_AGENTC_ADD_IDENTITY message might be able to carry only the public
parts of a key.
https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.certkeys defines
new *public* key formats for certificates - they don't contain the
private key components as far as I can see.
However, looking at the Go ssh-agent client, it inserts a private key
and certificate in a single SSH_AGENTC_ADD_IDENTITY or
SSH_AGENTC_ADD_ID_CONSTRAINED message:
https://github.com/golang/crypto/blob/master/ssh/agent/client.go#L664
(and I haven't been able to find documentation which defines that
private key + certificate message format).
So basically: can I send just a certificate to ssh-agent? And if so,
how is that done?
Hi,
this was discussed in the following two bugs in context of pkcs11 keys,
but without any definite solution.
https://bugzilla.mindrot.org/show_bug.cgi?id=2472
https://bugzilla.mindrot.org/show_bug.cgi?id=2808
To support this, we would need and update of ssh-agent protocol (or
extension) and some variant of a patch in the first bug above.
Regards,
--
Jakub Jelen
Senior Software Engineer
Crypto Team, Security Engineering
Red Hat, Inc.
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