[Bug 1612] New: ssh-add should not discard constraints if the agent fails to implement them

[bugzilla-daemon at bugzilla.mindrot.org]

https://bugzilla.mindrot.org/show_bug.cgi?id=1612

           Summary: ssh-add should not discard constraints if the agent
                    fails to implement them
           Product: Portable OpenSSH
           Version: 5.2p1
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ssh-add
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: dkg at fifthhorseman.net


Created an attachment (id=1652)
 --> (http://bugzilla.mindrot.org/attachment.cgi?id=1652)
ssh-add should not retry key addition without constraints if
constraints fail.

When ssh-add tries to add a key to the agent with constraints, and the
agent rejects the addition, ssh-add appears to retry the addition
without constraints.

This is dangerous behavior when the agent does not support certain
constraints.  For example, if a user uses an agent (such as the current
ssh-agent implementation in gnome-keyring) that does not support
confirmation or maximum lifetime, then using:

  ssh-add -t 3600

will print an error message but then proceed to re-add the key withut
the constrained lifetime.  this causes the agent to retain the key far
past the specified time, an explicit contravention of the user's
declared intent.

I expect more conservative behavior from openssh when handling
sensitive material.  Discarding the constraint and retrying should be a
choice left to the user, not taken automatically by ssh-add.

the attached patch should fix this behavior.

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