gpg-agent protocol

[NIIBE Yutaka]

On 12/03/2015 12:17 AM, Dubravszky József wrote:
> Atsuhiko Yamanaka made an excellent Eclipse SSH agent plugin
> (https://github.com/ymnk/jsch-agent-proxy) to proxy SSH agents to Eclipse
> subsystems. Currently it supports ssh-agent on Linux and Pageant on Windows.

It's good to hear his name again.  Great.

I guess it also just works with gpg-agent, possibly.  (Newer)
gpg-agent supports the communication method of Pageant<->Putty.

> My question might sound silly, but is there anything that would
> prevent me writing a connector that uses the same Win32 shared
> memory operations based protocol?

IIUC, the connector for Pageant works with gpg-agent, because it's the
same protocol.  Please try.

> I also recognized that on Windows an S.gpg-agent.ssh file is created in the
> users roaming AppData
> (C:\Users\USERNAME\AppData\Roaming\gnupg\S.gpg-agent.ssh), that pretty much
> resembles a Unix socket. As far as I know there is no such compatible domain
> socket on Windows, but what is this file then?

Please note that my knowledge is limited since I'm not a Windows user.
GnuPG implements Unix domain socket emulation and use it for
gpg<->gpg-agent communication.  The S.gpg-agent.ssh is the one for
SSH, while there are no client program on Windows (Putty uses another
channel: Win32 shared memory operations).
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