On Wed, 4 Apr 2018, Alex Wilson wrote: > Hi, > > I've been reading the RFC draft for the OpenSSH agent protocol and > trying to understand the extension mechanism. It seems like a client, > after sending an extension message, will have to then interpret any > following success (0x6) message differently according to the extension > request just sent. The example with the "query" extension returning a > success message with extra data appended would seem to imply that, too. > Is that correct? > > If so, I would love to get some insight into why this was chosen over > having an "extension reply" message number or something like that. It > seems to me that the protocol up until now has always been stateless -- > you didn't have to know what you sent last in order to parse and > validate received data -- which generally makes implementations nice and > simple. After this change, client impls will have to change their > parsing of the success message dramatically after sending each extension > request message (and will have to track which ext they last sent etc), > since it doesn't include enough information in the message itself any > more to figure out what it should contain. I don't follow - clients always have to know that the last message sent was, otherwise they wouldn't be able to disambiguate the shared SSH_AGENT_SUCCESS / SSH_AGENT_FAILURE. If it's a problem in practice, then I guess I could add an extension- specific reply message to a future draft, but I'm struggling to think of a situation in which it would be needed. BTW nothing at present implements any extensions AFAIK. -d _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
