Add 'guix challenge'.

* guix/scripts/challenge.scm, tests/challenge.scm: New files.
* Makefile.am (MODULES): Add the former.
  (SCM_TESTS): Add the latter.
* doc.am (SUBCOMMANDS): Add 'challenge'.
* doc/guix.texi (Substitutes): Add xref to 'guix challenge'.
  (Invoking guix challenge): New node.
* doc/contributing.texi (Submitting Patches): Add note about using 'guix
  challenge'.
* po/guix/POTFILES.in: Add guix/scripts/challenge.scm.

1 files changed, 244 insertions, 0 deletions

diff --git a/guix/scripts/challenge.scm b/guix/scripts/challenge.scm
new file mode 100644
index 0000000000..19a9b061b8
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+++ b/guix/scripts/challenge.scm
@@ -0,0 +1,244 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix 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.
+;;;
+;;; GNU Guix 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 GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix scripts challenge)
+  #:use-module (guix ui)
+  #:use-module (guix scripts)
+  #:use-module (guix store)
+  #:use-module (guix utils)
+  #:use-module (guix monads)
+  #:use-module (guix base32)
+  #:use-module (guix packages)
+  #:use-module (guix serialization)
+  #:use-module (guix scripts substitute)
+  #:use-module (rnrs bytevectors)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-37)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 vlist)
+  #:use-module (ice-9 format)
+  #:use-module (web uri)
+  #:export (discrepancies
+
+            discrepancy?
+            discrepancy-item
+            discrepancy-local-sha256
+            discrepancy-narinfos
+
+            guix-challenge))
+
+;;; Commentary:
+;;;
+;;; Challenge substitute servers, checking whether they provide the same
+;;; binaries as those built locally.
+;;;
+;;; Here we completely bypass the daemon to access substitutes.  This is
+;;; because we want to be able to report fine-grain information about
+;;; discrepancies: We need to show the URL of the offending nar, its hash, and
+;;; so on.
+;;;
+;;; Code:
+
+(define ensure-store-item                         ;XXX: move to (guix ui)?
+  (@@ (guix scripts size) ensure-store-item))
+
+;; Representation of a hash mismatch for ITEM.
+(define-record-type <discrepancy>
+  (discrepancy item local-sha256 narinfos)
+  discrepancy?
+  (item         discrepancy-item)                   ;string, /gnu/store/… item
+  (local-sha256 discrepancy-local-sha256)           ;bytevector | #f
+  (narinfos     discrepancy-narinfos))              ;list of <narinfo>
+
+(define (locally-built? store item)
+  "Return true if ITEM was built locally."
+  ;; XXX: For now approximate it by checking whether there's a build log for
+  ;; ITEM.  There could be false negatives, if logs have been removed.
+  (->bool (log-file store item)))
+
+(define (query-locally-built-hash item)
+  "Return the hash of ITEM, a store item, if ITEM was built locally.
+Otherwise return #f."
+  (lambda (store)
+    (guard (c ((nix-protocol-error? c)
+               (values #f store)))
+      (if (locally-built? store item)
+          (values (query-path-hash store item) store)
+          (values #f store)))))
+
+(define-syntax-rule (report args ...)
+  (format (current-error-port) args ...))
+
+(define (discrepancies items servers)
+  "Challenge the substitute servers whose URLs are listed in SERVERS by
+comparing the hash of the substitutes of ITEMS that they serve.  Return the
+list of discrepancies.
+
+This procedure does not authenticate narinfos from SERVERS, nor does it verify
+that they are signed by an authorized public keys.  The reason is that, by
+definition, we may want to target unknown servers.  Furthermore, no risk is
+taken since we do not import the archives."
+  (define (compare item reference)
+    ;; Return a procedure to compare the hash of ITEM with REFERENCE.
+    (lambda (narinfo url)
+      (if (not narinfo)
+          (begin
+            (warning (_ "~a: no substitute at '~a'~%")
+                     item url)
+            #t)
+          (let ((value (narinfo-hash->sha256 (narinfo-hash narinfo))))
+            (bytevector=? reference value)))))
+
+  (define (select-reference item narinfos urls)
+    ;; Return a "reference" narinfo among NARINFOS.
+    (match narinfos
+      ((first narinfos ...)
+       (match servers
+         ((url urls ...)
+          (if (not first)
+              (select-reference item narinfos urls)
+              (narinfo-hash->sha256 (narinfo-hash first))))))
+      (()
+       (leave (_ "no substitutes for '~a'~%") item))))
+
+  (mlet* %store-monad ((local     (mapm %store-monad
+                                        query-locally-built-hash items))
+                       (remote -> (append-map (cut lookup-narinfos <> items)
+                                              servers))
+                       ;; No 'assert-valid-narinfo' on purpose.
+                       (narinfos -> (fold (lambda (narinfo vhash)
+                                            (if narinfo
+                                                (vhash-cons (narinfo-path narinfo) narinfo
+                                                            vhash)
+                                                vhash))
+                                          vlist-null
+                                          remote)))
+    (return (filter-map (lambda (item local)
+                          (let ((narinfos (vhash-fold* cons '() item narinfos)))
+                            (define reference
+                              (or local
+                                  (begin
+                                    (warning (_ "no local build for '~a'~%") item)
+                                    (select-reference item narinfos servers))))
+
+                            (if (every (compare item reference)
+                                       narinfos servers)
+                                #f
+                                (discrepancy item local narinfos))))
+                        items
+                        local))))
+
+(define* (summarize-discrepancy discrepancy
+                                #:key (hash->string
+                                       bytevector->nix-base32-string))
+  "Write to the current error port a summary of DISCREPANCY, a <discrepancy>
+object that denotes a hash mismatch."
+  (match discrepancy
+    (($ <discrepancy> item local (narinfos ...))
+     (report (_ "~a contents differ:~%") item)
+     (if local
+         (report (_ "  local hash: ~a~%") (hash->string local))
+         (warning (_ "no local build for '~a'~%") item))
+
+     (for-each (lambda (narinfo)
+                 (if narinfo
+                     (report (_ "  ~50a: ~a~%")
+                             (uri->string (narinfo-uri narinfo))
+                             (hash->string
+                              (narinfo-hash->sha256 (narinfo-hash narinfo))))
+                     (report (_ "  ~50a: unavailable~%")
+                             (uri->string (narinfo-uri narinfo)))))
+               narinfos))))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define (show-help)
+  (display (_ "Usage: guix challenge [PACKAGE...]
+Challenge the substitutes for PACKAGE... provided by one or more servers.\n"))
+  (display (_ "
+      --substitute-urls=URLS
+                         compare build results with those at URLS"))
+  (newline)
+  (display (_ "
+  -h, --help             display this help and exit"))
+  (display (_ "
+  -V, --version          display version information and exit"))
+  (newline)
+  (show-bug-report-information))
+
+(define %options
+  (list  (option '(#\h "help") #f #f
+                 (lambda args
+                   (show-help)
+                   (exit 0)))
+         (option '(#\V "version") #f #f
+                 (lambda args
+                   (show-version-and-exit "guix challenge")))
+
+         (option '("substitute-urls") #t #f
+                 (lambda (opt name arg result . rest)
+                   (apply values
+                          (alist-cons 'substitute-urls
+                                      (string-tokenize arg)
+                                      (alist-delete 'substitute-urls result))
+                          rest)))))
+
+(define %default-options
+  `((system . ,(%current-system))
+    (substitute-urls . ,%default-substitute-urls)))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-challenge . args)
+  (with-error-handling
+    (let* ((opts     (parse-command-line args %options (list %default-options)))
+           (files    (filter-map (match-lambda
+                                   (('argument . file) file)
+                                   (_ #f))
+                                 opts))
+           (system   (assoc-ref opts 'system))
+           (urls     (assoc-ref opts 'substitute-urls)))
+      (leave-on-EPIPE
+       (with-store store
+         (let ((files (match files
+                        (()
+                         (filter (cut locally-built? store <>)
+                                 (live-paths store)))
+                        (x
+                         files))))
+           (set-build-options store
+                              #:use-substitutes? #f)
+
+           (run-with-store store
+             (mlet* %store-monad ((items  (mapm %store-monad
+                                               ensure-store-item files))
+                                  (issues (discrepancies items urls)))
+               (for-each summarize-discrepancy issues)
+               (return (null? issues)))
+             #:system system)))))))
+
+;;; challenge.scm ends here