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Document agent protocol extensions.

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Jacob Nevins 2021-04-04 13:27:05 +01:00
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doc/sshnames.but
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@ -65,3 +65,66 @@ They have been superseded by \cw{rsa1024-sha1} and \cw{rsa2048-sha256}.
\dd These were used in drafts of what eventually became RFC\_4345.
They have been superseded by \cw{arcfour128} and \cw{arcfour256}.
\H{sshnames-agent} Agent extension request names
The SSH agent protocol, which is only specified in an Internet-Draft
at the time of writing
(\W{https://tools.ietf.org/html/draft-miller-ssh-agent}\cw{draft-miller-ssh-agent}),
defines an extension mechanism. These names can be sent in an
\cw{SSH_AGENTC_EXTENSION} message.
\dt \cw{add-ppk@putty.projects.tartarus.org}
\dd The payload is a single SSH-2 \cw{string} containing a keypair in
the PPK format defined in \k{ppk}. Compared to the standard
\cw{SSH_AGENTC_ADD_IDENTITY}, this extension allows adding keys in
encrypted form, with the agent requesting a decryption passphrase from
the user on demand, and able to revert the key to encrypted form.
\dt \cw{reencrypt@putty.projects.tartarus.org}
\dd The payload is a single SSH-2 \cw{string} specifying a public key
blob, as in \cw{SSH_AGENTC_REMOVE_IDENTITY}. Requests that the agent
forget any cleartext form of a specific key.
\lcont{
Returns \cw{SSH_AGENT_SUCCESS} if the agent ended up holding the key
only in encrypted form (even if it was already encrypted); returns
\cw{SSH_AGENT_EXTENSION_FAILURE} if not (if it wasn't held by the
agent at all, or only in cleartext form).
}
\dt \cw{reencrypt-all@putty.projects.tartarus.org}
\dd No payload. Requests that the agent forget the cleartext form of
any keys for which it holds an encrypted form.
\lcont{
If the agent holds any keys with an encrypted form (or no keys at all),
returns \cw{SSH_AGENT_SUCCESS} to indicate that no such keys are now
held in cleartext form, followed by a \cw{uint32} specifying how many keys
remain in cleartext form (because the agent didn't hold an encrypted
form for them). If the agent holds nothing but keys in cleartext form,
returns \cw{SSH_AGENT_EXTENSION_FAILURE}.
}
\dt \cw{list-extended@putty.projects.tartarus.org}
\dd No payload. Returns \cw{SSH_AGENT_SUCCESS} followed by a list of
identities similar to \cw{SSH_AGENT_IDENTITIES_ANSWER}, except that
each key has an extra SSH-2 \cw{string} at the end. Currently that
\cw{string} contains a single \cw{uint32} flags word, with the
following bits defined:
\lcont{
\dt Bit 0
\dd If set, key is held with an encrypted form (so that the
\c{reencrypt} extension can do something useful with it).
\dt Bit 1
\dd If set, key's cleartext form is not currently held (so the
user will have to supply a passphrase before the key can be used).
}