services: Add 'openssh-service'.

* gnu/packages/ssh.scm (openssh)[arguments]: Set sysconfdir to /etc/ssh.
* gnu/services/ssh.scm (<openssh-configuration>): New record type.
(%openssh-accounts): New variable.
(openssh-activation, openssh-config-file, openssh-shepherd-service)
(openssh-service): New procedures.
(openssh-service-type): New variable.
* doc/guix.texi (Networking Services): Document 'openssh-services'.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

doc/guix.texi

@@ -8199,6 +8199,40 @@ root.
 The other options should be self-descriptive.
 @end deffn
 
+@deffn {Scheme Procedure} openssh-service [#:pid-file "/var/run/sshd.pid"] @
+       [#:port-number 22] [#:permit-root-login 'without-password] @
+       [#:allow-empty-passwords #f] [#:password-authentication? #t] @
+       [#:pubkey-authentication? #t] [#:rsa-authentication? #t] @
+       [#:x11-forwarding? #f] [#:protocol-number "2"]
+Run the @command{sshd} program from @var{openssh} on port
+@var{port-number}.  @command{sshd} runs an SSH daemon and writes its PID
+to @var{pid-file}.  It understands SSH protocol
+@var{protocol-number}. The @var{protocol-number} can be either 1 or 2.
+
+@var{permit-root-login} takes one of @code{#t}, @code{'without-password}
+and @code{#f}.  It is used to allow root login through SSH.
+@code{'without-password} means that root login is allowed, but not with
+password-based authentication.
+
+When @var{allow-empty-passwords?} is true, users with empty passwords
+may log in.  When false, they may not.
+
+When @var{password-authentication?} is true, users may log in with their
+password.  When false, they have to use other means of authentication.
+
+When @var{pubkey-authentication?} is true, users may log in using public
+key authentication.  When false, users have to use other means of
+authentication.  Authorized public keys are stored in
+@file{~/.ssh/authorized_keys}.  This is used only by protocol version 2.
+
+When @var{rsa-authentication?} is true, users may log in using pure RSA
+authentication.  When false, users have to use other means of
+authentication.  This is used only by protocol 1.
+
+When @var{x11-forwarding?} is true, @command{ssh} options @option{-X}
+and @option{-Y} will work.
+@end deffn
+
 @deffn {Scheme Procedure} dropbear-service [@var{config}]
 Run the @uref{https://matt.ucc.asn.au/dropbear/dropbear.html,Dropbear SSH
 daemon} with the given @var{config}, a @code{<dropbear-configuration>}

gnu/packages/ssh.scm

@@ -144,7 +144,7 @@ (define-public openssh
              ("xauth" ,xauth)))                   ;for 'ssh -X' and 'ssh -Y'
    (arguments
     `(#:test-target "tests"
-      #:configure-flags '("--sysconfdir=/etc"
+      #:configure-flags '("--sysconfdir=/etc/ssh"
 
                           ;; Default value of 'PATH' used by sshd.
                           "--with-default-path=/run/current-system/profile/bin"

gnu/services/ssh.scm

@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 David Craven <david@craven.ch>
+;;; Copyright © 2016 Julien Lepiller <julien@lepiller.eu>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -19,17 +20,25 @@
 
 (define-module (gnu services ssh)
   #:use-module (gnu packages ssh)
+  #:use-module (gnu packages admin)
   #:use-module (gnu services)
   #:use-module (gnu services shepherd)
   #:use-module (gnu system pam)
+  #:use-module (gnu system shadow)
   #:use-module (guix gexp)
   #:use-module (guix records)
   #:use-module (srfi srfi-26)
+  #:use-module (ice-9 match)
   #:export (lsh-configuration
             lsh-configuration?
             lsh-service
             lsh-service-type
 
+            openssh-configuration
+            openssh-configuration?
+            openssh-service-type
+            openssh-service
+
             dropbear-configuration
             dropbear-configuration?
             dropbear-service-type
@@ -244,6 +253,128 @@ (define* (lsh-service #:key
                                public-key-authentication?)
                               (initialize? initialize?))))
 
+
+;;;
+;;; OpenSSH.
+;;;
+
+(define-record-type* <openssh-configuration>
+  openssh-configuration make-openssh-configuration
+  openssh-configuration?
+  (pid-file              openssh-configuration-pid-file) ;string
+  (port-number           openssh-configuration-port-number) ;integer
+  (permit-root-login     openssh-configuration-permit-root-login) ;Boolean | 'without-password
+  (allow-empty-passwords? openssh-configuration-allow-empty-passwords?) ;Boolean
+  (password-authentication? openssh-configuration-password-authentication?) ;Boolean
+  (pubkey-authentication? openssh-configuration-pubkey-authentication?) ;Boolean
+  (rsa-authentication?   openssh-configuration-rsa-authentication?) ;Boolean
+  (x11-forwarding?       openssh-configuration-x11-forwarding?) ;Boolean
+  (protocol-number       openssh-configuration-protocol-number)) ;integer
+
+(define %openssh-accounts
+  (list (user-group (name "sshd") (system? #t))
+        (user-account
+          (name "sshd")
+          (group "sshd")
+          (system? #t)
+          (comment "sshd privilege separation user")
+          (home-directory "/var/run/sshd")
+          (shell #~(string-append #$shadow "/sbin/nologin")))))
+
+(define (openssh-activation config)
+  "Return the activation GEXP for CONFIG."
+  #~(begin
+      (mkdir-p "/etc/ssh")
+      (mkdir-p (dirname #$(openssh-configuration-pid-file config)))
+
+      ;; Generate missing host keys.
+      (system* (string-append #$openssh "/bin/ssh-keygen") "-A")))
+
+(define (openssh-config-file config)
+  "Return the sshd configuration file corresponding to CONFIG."
+  (computed-file
+   "sshd_config"
+   #~(call-with-output-file #$output
+       (lambda (port)
+         (display "# Generated by 'openssh-service'.\n" port)
+         (format port "Protocol ~a\n"
+                 #$(if (eq? (openssh-configuration-protocol-number config) 1)
+                       "1" "2"))
+         (format port "Port ~a\n"
+                 #$(number->string (openssh-configuration-port-number config)))
+         (format port "PermitRootLogin ~a\n"
+                 #$(match (openssh-configuration-permit-root-login config)
+                     (#t "yes")
+                     (#f "no")
+                     ('without-password "without-password")))
+         (format port "PermitEmptyPasswords ~a\n"
+                 #$(if (openssh-configuration-allow-empty-passwords? config)
+                       "yes" "no"))
+         (format port "PasswordAuthentication ~a\n"
+                 #$(if (openssh-configuration-password-authentication? config)
+                       "yes" "no"))
+         (format port "PubkeyAuthentication ~a\n"
+                 #$(if (openssh-configuration-pubkey-authentication? config)
+                       "yes" "no"))
+         (format port "RSAAuthentication ~a\n"
+                 #$(if (openssh-configuration-rsa-authentication? config)
+                       "yes" "no"))
+         (format port "X11Forwarding ~a\n"
+                 #$(if (openssh-configuration-x11-forwarding? config)
+                       "yes" "no"))
+         (format port "PidFile ~a\n"
+                 #$(openssh-configuration-pid-file config))
+         #t))))
+
+(define (openssh-shepherd-service config)
+  "Return a <shepherd-service> for openssh with CONFIG."
+
+  (define pid-file
+    (openssh-configuration-pid-file config))
+
+  (define openssh-command
+    #~(list (string-append #$openssh "/sbin/sshd")
+            "-D" "-f" #$(openssh-config-file config)))
+
+  (list (shepherd-service
+         (documentation "OpenSSH server.")
+         (requirement '(networking syslogd))
+         (provision '(ssh-daemon))
+         (start #~(make-forkexec-constructor #$openssh-command
+                                             #:pid-file #$pid-file))
+         (stop #~(make-kill-destructor)))))
+
+(define openssh-service-type
+  (service-type (name 'openssh)
+                (extensions
+                 (list (service-extension shepherd-root-service-type
+                                          openssh-shepherd-service)
+                       (service-extension activation-service-type
+                                          openssh-activation)
+                       (service-extension account-service-type
+                                          (const %openssh-accounts))))))
+
+(define* (openssh-service #:key
+                          (pid-file "/var/run/sshd.pid")
+                          (port-number 22)
+                          (permit-root-login 'without-password)
+                          (allow-empty-passwords? #f)
+                          (password-authentication? #t)
+                          (pubkey-authentication? #t)
+                          (rsa-authentication? #t)
+                          (x11-forwarding? #f)
+                          (protocol-number 2))
+  (service openssh-service-type (openssh-configuration
+                                 (pid-file pid-file)
+                                 (port-number port-number)
+                                 (permit-root-login permit-root-login)
+                                 (allow-empty-passwords? allow-empty-passwords?)
+                                 (password-authentication? password-authentication?)
+                                 (pubkey-authentication? pubkey-authentication?)
+                                 (rsa-authentication? rsa-authentication?)
+                                 (x11-forwarding? x11-forwarding?)
+                                 (protocol-number protocol-number))))
+
 
 ;;;
 ;;; Dropbear.