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;;; agent.scm -- Interaction with SSH agents.
;; Copyright (C) 2020-2021 Artyom V. Poptsov <poptsov.artyom@gmail.com>
;;
;; This file is a part of Guile-SSH.
;;
;; Guile-SSH is free software: you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation, either version 3 of the
;; License, or (at your option) any later version.
;;
;; Guile-SSH is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;; General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with Guile-SSH. If not, see
;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;; The module contains procedures for interaction with SSH agent instances.
;;
;; The module provides the following procedures:
;; ssh-agent-sock-get
;; ssh-agent-sock-set!
;; ssh-agent-start
;; ssh-agent-stop
;; ssh-agent-info
;;
;; See the Info documentation for detailed description of these exceptions and
;; aforementioned procedures.
;;; Code:
(define-module (ssh agent)
#:use-module (ice-9 regex)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 popen)
#:export (ssh-agent-sock-get
ssh-agent-sock-set!
ssh-agent-start
ssh-agent-stop
ssh-agent-info))
(define %ssh-agent-sock-env "SSH_AUTH_SOCK")
(define %ssh-agent-dir-regexp (make-regexp "^ssh-[A-Za-z0-9]{12}"))
(define %ssh-agent-pid-file-regexp (make-regexp "agent.[0-9]+"))
(define %ssh-auth-sock-regexp
(make-regexp "SSH_AUTH_SOCK=(.*); export SSH_AUTH_SOCK;"))
(define %ssh-agent-pid-regexp
(make-regexp "SSH_AGENT_PID=(.*); export SSH_AGENT_PID;"))
(define (ssh-agent-start)
"Start an OpenSSH agent. Return a list with SSH agent information."
(let ((p (open-input-pipe "ssh-agent -s")))
(let ((ssh-auth-sock-data (read-line p))
(ssh-agent-pid-data (read-line p)))
(when (or (eof-object? ssh-auth-sock-data)
(eof-object? ssh-agent-pid-data))
(error "Could not start a SSH agent"))
(close p)
(let ((sockm (regexp-exec %ssh-auth-sock-regexp ssh-auth-sock-data))
(pidm (regexp-exec %ssh-agent-pid-regexp ssh-agent-pid-data)))
(unless (and sockm pidm)
(error "Could not parse SSH agent response"
ssh-auth-sock-data
ssh-agent-pid-data))
`((SSH_AUTH_SOCK . ,(match:substring sockm 1))
(SSH_AGENT_PID . ,(match:substring pidm 1)))))))
(define (ssh-agent-stop)
"Kill the current agent (given by the 'SSH_AGENT_PID' environment
variable)."
(system "ssh-agent -k"))
(define* (ssh-agent-info #:key
(user (getenv "USER"))
(path (or (getenv "TMPDIR") "/tmp")))
"Get OpenSSH agent information for a given USER as a list."
(define (owned-by-user? file-name uid)
(= (stat:uid (stat file-name)) uid))
(define (user->uid user)
(passwd:uid (getpwnam user)))
(define (get-agent-socket-file dir-name)
(let ((stream (opendir dir-name)))
(let loop ((file-name (readdir stream)))
(if (regexp-exec %ssh-agent-pid-file-regexp file-name)
(begin
(closedir stream)
file-name)
(loop (readdir stream))))))
(define (agent-socket->pid agent-socket)
(cadr (string-split agent-socket #\.)))
(let ((dir (opendir path))
(uid (user->uid user)))
(let loop ((entry (readdir dir))
(info '()))
(if (eof-object? entry)
(begin
(closedir dir)
info)
(let ((file-name (string-append path "/" entry)))
(if (and (regexp-exec %ssh-agent-dir-regexp entry)
(owned-by-user? file-name uid))
(let* ((agent-socket (get-agent-socket-file file-name))
(auth-sock (string-append file-name "/" agent-socket))
(agent-pid (agent-socket->pid agent-socket)))
(loop (readdir dir)
(append info
(list
(list (cons 'SSH_AUTH_SOCK auth-sock)
(cons 'SSH_AGENT_PID agent-pid))))))
(loop (readdir dir) info)))))))
(define (ssh-agent-sock-get)
"Get the 'SSH_AGENT_SOCK' environment variable value."
(getenv %ssh-agent-sock-env))
(define (ssh-agent-sock-set! sock-file)
"Set the value of 'SSH_AGENT_SOCK' environment variable."
(setenv %ssh-agent-sock-env sock-file))
;;; agent.scm ends here.
|
