guix/ssh.scm

   1 ;;; GNU Guix --- Functional package management for GNU
   2 ;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
   3 ;;;
   4 ;;; This file is part of GNU Guix.
   5 ;;;
   6 ;;; GNU Guix is free software; you can redistribute it and/or modify it
   7 ;;; under the terms of the GNU General Public License as published by
   8 ;;; the Free Software Foundation; either version 3 of the License, or (at
   9 ;;; your option) any later version.
  10 ;;;
  11 ;;; GNU Guix is distributed in the hope that it will be useful, but
  12 ;;; WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 ;;; GNU General Public License for more details.
  15 ;;;
  16 ;;; You should have received a copy of the GNU General Public License
  17 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
  18
  19 (define-module (guix ssh)
  20   #:use-module (guix store)
  21   #:use-module ((guix ui) #:select (G_ N_))
  22   #:use-module (ssh session)
  23   #:use-module (ssh auth)
  24   #:use-module (ssh key)
  25   #:use-module (ssh channel)
  26   #:use-module (ssh popen)
  27   #:use-module (ssh session)
  28   #:use-module (ssh dist)
  29   #:use-module (ssh dist node)
  30   #:use-module (srfi srfi-11)
  31   #:use-module (srfi srfi-34)
  32   #:use-module (srfi srfi-35)
  33   #:use-module (ice-9 match)
  34   #:use-module (ice-9 binary-ports)
  35   #:export (open-ssh-session
  36             remote-daemon-channel
  37             connect-to-remote-daemon
  38             send-files
  39             retrieve-files
  40             remote-store-host
  41
  42             file-retrieval-port))
  43
  44 ;;; Commentary:
  45 ;;;
  46 ;;; This module provides tools to support communication with remote stores
  47 ;;; over SSH, using Guile-SSH.
  48 ;;;
  49 ;;; Code:
  50
  51 (define %compression
  52   "zlib@openssh.com,zlib")
  53
  54 (define* (open-ssh-session host #:key user port
  55                            (compression %compression))
  56   "Open an SSH session for HOST and return it.  When USER and PORT are #f, use
  57 default values or whatever '~/.ssh/config' specifies; otherwise use them.
  58 Throw an error on failure."
  59   (let ((session (make-session #:user user
  60                                #:host host
  61                                #:port port
  62                                #:timeout 10       ;seconds
  63                                ;; #:log-verbosity 'protocol
  64
  65                                ;; We need lightweight compression when
  66                                ;; exchanging full archives.
  67                                #:compression compression
  68                                #:compression-level 3)))
  69
  70     ;; Honor ~/.ssh/config.
  71     (session-parse-config! session)
  72
  73     (match (connect! session)
  74       ('ok
  75        ;; Use public key authentication, via the SSH agent if it's available.
  76        (match (userauth-public-key/auto! session)
  77          ('success
  78           session)
  79          (x
  80           (disconnect! session)
  81           (raise (condition
  82                   (&message
  83                    (message (format #f (G_ "SSH authentication failed for '~a': ~a~%")
  84                                     host (get-error session)))))))))
  85       (x
  86        ;; Connection failed or timeout expired.
  87        (raise (condition
  88                (&message
  89                 (message (format #f (G_ "SSH connection to '~a' failed: ~a~%")
  90                                  host (get-error session))))))))))
  91
  92 (define* (remote-daemon-channel session
  93                                 #:optional
  94                                 (socket-name
  95                                  "/var/guix/daemon-socket/socket"))
  96   "Return an input/output port (an SSH channel) to the daemon at SESSION."
  97   (define redirect
  98     ;; Code run in SESSION to redirect the remote process' stdin/stdout to the
  99     ;; daemon's socket, à la socat.  The SSH protocol supports forwarding to
 100     ;; Unix-domain sockets but libssh doesn't have an API for that, hence this
 101     ;; hack.
 102     `(begin
 103        (use-modules (ice-9 match) (rnrs io ports))
 104
 105        (let ((sock   (socket AF_UNIX SOCK_STREAM 0))
 106              (stdin  (current-input-port))
 107              (stdout (current-output-port)))
 108          (setvbuf stdin _IONBF)
 109          (setvbuf stdout _IONBF)
 110          (connect sock AF_UNIX ,socket-name)
 111
 112          (let loop ()
 113            (match (select (list stdin sock) '() (list stdin stdout sock))
 114              ((reads writes ())
 115               (when (memq stdin reads)
 116                 (match (get-bytevector-some stdin)
 117                   ((? eof-object?)
 118                    (primitive-exit 0))
 119                   (bv
 120                    (put-bytevector sock bv))))
 121               (when (memq sock reads)
 122                 (match (get-bytevector-some sock)
 123                   ((? eof-object?)
 124                    (primitive-exit 0))
 125                   (bv
 126                    (put-bytevector stdout bv))))
 127               (loop))
 128              (_
 129               (primitive-exit 1)))))))
 130
 131   (open-remote-pipe* session OPEN_BOTH
 132                      ;; Sort-of shell-quote REDIRECT.
 133                      "guile" "-c"
 134                      (object->string
 135                       (object->string redirect))))
 136
 137 (define* (connect-to-remote-daemon session
 138                                    #:optional
 139                                    (socket-name
 140                                     "/var/guix/daemon-socket/socket"))
 141   "Connect to the remote build daemon listening on SOCKET-NAME over SESSION,
 142 an SSH session.  Return a <nix-server> object."
 143   (open-connection #:port (remote-daemon-channel session)))
 144
 145
 146 (define (store-import-channel session)
 147   "Return an output port to which archives to be exported to SESSION's store
 148 can be written."
 149   ;; Using the 'import-paths' RPC on a remote store would be slow because it
 150   ;; makes a round trip every time 32 KiB have been transferred.  This
 151   ;; procedure instead opens a separate channel to use the remote
 152   ;; 'import-paths' procedure, which consumes all the data in a single round
 153   ;; trip.  This optimizes the successful case at the expense of error
 154   ;; conditions: errors can only be reported once all the input has been
 155   ;; consumed.
 156   (define import
 157     `(begin
 158        (use-modules (guix) (srfi srfi-34)
 159                     (rnrs io ports) (rnrs bytevectors))
 160
 161        (define (consume-input port)
 162          (let ((bv (make-bytevector 32768)))
 163            (let loop ()
 164              (let ((n (get-bytevector-n! port bv 0
 165                                          (bytevector-length bv))))
 166                (unless (eof-object? n)
 167                  (loop))))))
 168
 169        ;; Upon completion, write an sexp that denotes the status.
 170        (write
 171         (catch #t
 172           (lambda ()
 173             (guard (c ((nix-protocol-error? c)
 174                        ;; Consume all the input since the only time we can
 175                        ;; report the error is after everything has been
 176                        ;; consumed.
 177                        (consume-input (current-input-port))
 178                        (list 'protocol-error (nix-protocol-error-message c))))
 179               (with-store store
 180                 (setvbuf (current-input-port) _IONBF)
 181                 (import-paths store (current-input-port))
 182                 '(success))))
 183           (lambda args
 184             (cons 'error args))))))
 185
 186   (open-remote-pipe session
 187                     (string-join
 188                      `("guile" "-c"
 189                        ,(object->string (object->string import))))
 190                     OPEN_BOTH))
 191
 192 (define* (store-export-channel session files
 193                                #:key recursive?)
 194   "Return an input port from which an export of FILES from SESSION's store can
 195 be read.  When RECURSIVE? is true, the closure of FILES is exported."
 196   ;; Same as above: this is more efficient than calling 'export-paths' on a
 197   ;; remote store.
 198   (define export
 199     `(begin
 200        (use-modules (guix))
 201
 202        (with-store store
 203          (setvbuf (current-output-port) _IONBF)
 204
 205          ;; FIXME: Exceptions are silently swallowed.  We should report them
 206          ;; somehow.
 207          (export-paths store ',files (current-output-port)
 208                        #:recursive? ,recursive?))))
 209
 210   (open-remote-input-pipe session
 211                           (string-join
 212                            `("guile" "-c"
 213                              ,(object->string
 214                                (object->string export))))))
 215
 216 (define* (send-files local files remote
 217                      #:key
 218                      recursive?
 219                      (log-port (current-error-port)))
 220   "Send the subset of FILES from LOCAL (a local store) that's missing to
 221 REMOTE, a remote store.  When RECURSIVE? is true, send the closure of FILES.
 222 Return the list of store items actually sent."
 223   ;; Compute the subset of FILES missing on SESSION and send them.
 224   (let* ((files   (if recursive? (requisites local files) files))
 225          (session (channel-get-session (nix-server-socket remote)))
 226          (node    (make-node session))
 227          (missing (node-eval node
 228                              `(begin
 229                                 (use-modules (guix)
 230                                              (srfi srfi-1) (srfi srfi-26))
 231
 232                                 (with-store store
 233                                   (remove (cut valid-path? store <>)
 234                                           ',files)))))
 235          (count   (length missing))
 236          (port    (store-import-channel session)))
 237     (format log-port (N_ "sending ~a store item to '~a'...~%"
 238                          "sending ~a store items to '~a'...~%" count)
 239             count (session-get session 'host))
 240
 241     ;; Send MISSING in topological order.
 242     (export-paths local missing port)
 243
 244     ;; Tell the remote process that we're done.  (In theory the end-of-archive
 245     ;; mark of 'export-paths' would be enough, but in practice it's not.)
 246     (channel-send-eof port)
 247
 248     ;; Wait for completion of the remote process and read the status sexp from
 249     ;; PORT.
 250     (let* ((result (false-if-exception (read port)))
 251            (status (zero? (channel-get-exit-status port))))
 252       (close-port port)
 253       (match result
 254         (('success . _)
 255          missing)
 256         (('protocol-error message)
 257          (raise (condition
 258                  (&nix-protocol-error (message message) (status 42)))))
 259         (('error key args ...)
 260          (raise (condition
 261                  (&nix-protocol-error
 262                   (message (call-with-output-string
 263                              (lambda (port)
 264                                (print-exception port #f key args))))
 265                   (status 43)))))
 266         (_
 267          (raise (condition
 268                  (&nix-protocol-error
 269                   (message "unknown error while sending files over SSH")
 270                   (status 44)))))))))
 271
 272 (define (remote-store-session remote)
 273   "Return the SSH channel beneath REMOTE, a remote store as returned by
 274 'connect-to-remote-daemon', or #f."
 275   (channel-get-session (nix-server-socket remote)))
 276
 277 (define (remote-store-host remote)
 278   "Return the name of the host REMOTE is connected to, where REMOTE is a
 279 remote store as returned by 'connect-to-remote-daemon'."
 280   (match (remote-store-session remote)
 281     (#f #f)
 282     ((? session? session)
 283      (session-get session 'host))))
 284
 285 (define* (file-retrieval-port files remote
 286                               #:key recursive?)
 287   "Return an input port from which to retrieve FILES (a list of store items)
 288 from REMOTE, along with the number of items to retrieve (lower than or equal
 289 to the length of FILES.)"
 290   (values (store-export-channel (remote-store-session remote) files
 291                                 #:recursive? recursive?)
 292           (length files)))            ;XXX: inaccurate when RECURSIVE? is true
 293
 294 (define* (retrieve-files local files remote
 295                          #:key recursive? (log-port (current-error-port)))
 296   "Retrieve FILES from REMOTE and import them using the 'import-paths' RPC on
 297 LOCAL.  When RECURSIVE? is true, retrieve the closure of FILES."
 298   (let-values (((port count)
 299                 (file-retrieval-port files remote
 300                                      #:recursive? recursive?)))
 301     (format #t (N_ "retrieving ~a store item from '~a'...~%"
 302                    "retrieving ~a store items from '~a'...~%" count)
 303             count (remote-store-host remote))
 304     (when (eof-object? (lookahead-u8 port))
 305       ;; The failure could be because one of the requested store items is not
 306       ;; valid on REMOTE, or because Guile or Guix is improperly installed.
 307       ;; TODO: Improve error reporting.
 308       (raise (condition
 309               (&message
 310                (message
 311                 (format #f
 312                         (G_ "failed to retrieve store items from '~a'")
 313                         (remote-store-host remote)))))))
 314
 315     (let ((result (import-paths local port)))
 316       (close-port port)
 317       result)))
 318
 319 ;;; ssh.scm ends here