;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015-2017, 2019-2022 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 colors)
  #:use-module (guix scripts)
  #:use-module (guix store)
  #:use-module (guix utils)
  #:use-module (guix monads)
  #:use-module (guix base32)
  #:use-module ((guix progress) #:hide (dump-port*))
  #:use-module (guix serialization)
  #:use-module (guix substitutes)
  #:use-module (guix narinfo)
  #:use-module (rnrs bytevectors)
  #:autoload   (guix http-client) (http-fetch)
  #:use-module ((guix build syscalls) #:select (terminal-columns))
  #:autoload   (guix build utils) (make-file-writable)
  #:use-module (gcrypt hash)
  #: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 (srfi srfi-71)
  #:use-module (ice-9 match)
  #:use-module (ice-9 vlist)
  #:use-module (ice-9 format)
  #:use-module (ice-9 ftw)
  #:use-module (web uri)
  #:export (compare-contents

            comparison-report?
            comparison-report-item
            comparison-report-result
            comparison-report-local-sha256
            comparison-report-narinfos

            comparison-report-match?
            comparison-report-mismatch?
            comparison-report-inconclusive?

            differing-files
            call-with-mismatches

            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 comparison report for ITEM.
(define-record-type <comparison-report>
  (%comparison-report item result local-sha256 narinfos)
  comparison-report?
  (item         comparison-report-item)    ;string, /gnu/store/… item
  (result       comparison-report-result)  ;'match | 'mismatch | 'inconclusive
  (local-sha256 comparison-report-local-sha256)   ;bytevector | #f
  (narinfos     comparison-report-narinfos))      ;list of <narinfo>

(define-syntax comparison-report
  ;; Some sort of a an enum to make sure 'result' is correct.
  (syntax-rules (match mismatch inconclusive)
    ((_ item 'match rest ...)
     (%comparison-report item 'match rest ...))
    ((_ item 'mismatch rest ...)
     (%comparison-report item 'mismatch rest ...))
    ((_ item 'inconclusive rest ...)
     (%comparison-report item 'inconclusive rest ...))))

(define (comparison-report-predicate result)
  "Return a predicate that returns true when pass a REPORT that has RESULT."
  (lambda (report)
    (eq? (comparison-report-result report) result)))

(define comparison-report-mismatch?
  (comparison-report-predicate 'mismatch))

(define comparison-report-match?
  (comparison-report-predicate 'match))

(define comparison-report-inconclusive?
  (comparison-report-predicate 'inconclusive))

(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 ((store-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 (compare-contents 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 <comparison-report> objects.

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)
      (or (not narinfo)
          (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))))))))

  (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)
                                            (vhash-cons (narinfo-path narinfo) narinfo
                                                        vhash))
                                          vlist-null
                                          remote)))
    (return (map (lambda (item local)
                   (match (vhash-fold* cons '() item narinfos)
                     (()                          ;no substitutes
                      (comparison-report item 'inconclusive local '()))
                     ((narinfo)
                      (if local
                          (if ((compare item local) narinfo (first servers))
                              (comparison-report item 'match
                                                 local (list narinfo))
                              (comparison-report item 'mismatch
                                                 local (list narinfo)))
                          (comparison-report item 'inconclusive
                                             local (list narinfo))))
                     ((narinfos ...)
                      (let ((reference
                             (or local (select-reference item narinfos
                                                         servers))))
                        (if (every (compare item reference) narinfos servers)
                            (comparison-report item 'match
                                               local narinfos)
                            (comparison-report item 'mismatch
                                               local narinfos))))))
                 items
                 local))))


;;;
;;; Reporting.
;;;

(define (port-sha256* port size)
  ;; Like 'port-sha256', but limited to SIZE bytes.
  (let ((out get (open-sha256-port)))
    (dump-port* port out size)
    (close-port out)
    (get)))

(define (archive-contents port)
  "Return a list representing the files contained in the nar read from PORT.
The list is sorted in canonical order--i.e., the order in which entries appear
in the nar."
  (reverse
   (fold-archive (lambda (file type contents result)
                   (match type
                     ((or 'regular 'executable)
                      (match contents
                        ((port . size)
                         (cons `(,file ,type ,(port-sha256* port size))
                               result))))
                     ('directory result)
                     ('directory-complete result)
                     ('symlink
                      (cons `(,file ,type ,contents) result))))
                 '()
                 port
                 "")))

(define (store-item-contents item)
  "Return a list of files and contents for ITEM in the same format as
'archive-contents'."
  (let loop ((file item))
    (define stat
      (lstat file))

    (define short
      (string-drop file (string-length item)))

    (match (stat:type stat)
      ('regular
       (let ((size (stat:size stat))
             (type (if (zero? (logand (stat:mode stat)
                                      #o100))
                       'regular
                       'executable)))
         `((,short ,type
                   ,(call-with-input-file file
                      (cut port-sha256* <> size))))))
      ('symlink
       `((,short symlink ,(readlink file))))
      ('directory
       (append-map (match-lambda
                     ((or "." "..")
                      '())
                     (entry
                      (loop (string-append file "/" entry))))
                   ;; Traverse entries in canonical order, the same as the
                   ;; order of entries in nars.
                   (scandir file (const #t) string<?))))))

(define (call-with-nar narinfo proc)
  "Call PROC with an input port from which it can read the nar pointed to by
NARINFO."
  (let* ((uri compression size (narinfo-best-uri narinfo))
         (port actual-size     (http-fetch uri)))
    (define reporter
      (progress-reporter/file (narinfo-path narinfo)
                              (and size
                                   (max size (or actual-size 0))) ;defensive
                              #:abbreviation (const (uri-host uri))))

    (define result
      (call-with-decompressed-port (string->symbol compression)
          (progress-report-port reporter port)
        proc))

    (close-port port)
    (erase-current-line (current-output-port))
    result))

(define (narinfo-contents narinfo)
  "Fetch the nar described by NARINFO and return a list representing the file
it contains."
  (call-with-nar narinfo archive-contents))

(define (differing-files comparison-report)
  "Return a list of files that differ among the nars and possibly the local
store item specified in COMPARISON-REPORT."
  (define contents
    (map narinfo-contents
         (comparison-report-narinfos comparison-report)))

  (define local-contents
    (and (comparison-report-local-sha256 comparison-report)
         (store-item-contents (comparison-report-item comparison-report))))

  (match (apply lset-difference equal?
                (take (delete-duplicates
                       (if local-contents
                           (cons local-contents contents)
                           contents))
                      2))
    (((files _ ...) ...)
     files)))

(define (report-differing-files comparison-report)
  "Report differences among the nars and possibly the local store item
specified in COMPARISON-REPORT."
  (match (differing-files comparison-report)
    (()
     #t)
    ((files ...)
     (format #t (N_ "  differing file:~%"
                    "  differing files:~%"
                    (length files)))
     (format #t     "~{    ~a~%~}" files))))

(define (make-directory-writable directory)
  "Recurse into DIRECTORY and make each entry writable, similar to
'chmod -R +w DIRECTORY'."
  (file-system-fold (const #t)
                    (lambda (file stat _)         ;leaf
                      (unless (eq? 'symlink (stat:type stat))
                        (make-file-writable file)))
                    (lambda (directory stat _)    ;down
                      (make-file-writable directory))
                    (const #t)                    ;up
                    (const #f)                    ;skip
                    (lambda (file stat errno _)   ;error
                      (leave (G_ "failed to delete '~a': ~a~%")
                             file (strerror errno)))
                    #t
                    directory))

(define (call-with-mismatches comparison-report proc)
  "Call PROC with two directories containing the mismatching store items."
  (define local-hash
    (comparison-report-local-sha256 comparison-report))

  (define narinfos
    (comparison-report-narinfos comparison-report))

  (define (restore-file* port directory)
    ;; Since 'restore-file' sets "canonical" file permissions (read-only),
    ;; make an extra traversal to make DIRECTORY writable so it can be deleted
    ;; when the dynamic extent of 'call-with-temporary-directory' is left.
    (restore-file port directory)
    (make-directory-writable directory))

  (call-with-temporary-directory
   (lambda (directory1)
     (call-with-temporary-directory
      (lambda (directory2)
        (define narinfo1
          (if local-hash
              (find (lambda (narinfo)
                      (not (bytevector=? (narinfo-hash->sha256
                                          (narinfo-hash narinfo))
                                         local-hash)))
                    narinfos)
              (first (comparison-report-narinfos comparison-report))))

        (define narinfo2
          (and (not local-hash)
               (find (lambda (narinfo)
                       (not (eq? narinfo narinfo1)))
                     narinfos)))

        (rmdir directory1)
        (call-with-nar narinfo1 (cut restore-file* <> directory1))
        (when narinfo2
          (rmdir directory2)
          (call-with-nar narinfo2 (cut restore-file* <> directory2)))
        (proc directory1
              (if local-hash
                  (comparison-report-item comparison-report)
                  directory2)))))))

(define %diffoscope-command
  ;; Default external diff command.  Pass "--exclude-directory-metadata" so
  ;; that the mtime/ctime differences are ignored.
  '("diffoscope" "--exclude-directory-metadata=yes"))

(define* (report-differing-files/external comparison-report
                                          #:optional
                                          (command %diffoscope-command))
  "Run COMMAND to show the file-level differences for the mismatches in
COMPARISON-REPORT."
  (call-with-mismatches comparison-report
                        (lambda (directory1 directory2)
                          (apply system*
                                 (append command
                                         (list directory1 directory2))))))

(define good-news
  (coloring-procedure (color BOLD GREEN)))
(define bad-news
  (coloring-procedure (color BOLD RED)))

(define* (summarize-report comparison-report
                           #:key
                           (report-differences (const #f))
                           (hash->string bytevector->nix-base32-string)
                           verbose?)
  "Write to the current error port a summary of COMPARISON-REPORT, a
<comparison-report> object.  When VERBOSE?, display matches in addition to
mismatches and inconclusive reports.  Upon mismatch, call REPORT-DIFFERENCES
with COMPARISON-REPORT."
  (define (report-hashes item local narinfos)
    (if local
        (report (G_ "  local hash: ~a~%") (hash->string local))
        (report (G_ "  no local build for '~a'~%") item))
    (for-each (lambda (narinfo)
                (report (G_ "  ~50a: ~a~%")
                        (uri->string (narinfo-best-uri narinfo))
                        (hash->string
                         (narinfo-hash->sha256 (narinfo-hash narinfo)))))
              narinfos))

  (match comparison-report
    (($ <comparison-report> item 'mismatch local (narinfos ...))
     (report (bad-news (G_ "~a contents differ:~%")) item)
     (report-hashes item local narinfos)
     (report-differences comparison-report))
    (($ <comparison-report> item 'inconclusive #f narinfos)
     (warning (G_ "could not challenge '~a': no local build~%") item))
    (($ <comparison-report> item 'inconclusive locals ())
     (warning (G_ "could not challenge '~a': no substitutes~%") item))
    (($ <comparison-report> item 'match local (narinfos ...))
     (when verbose?
       (report (good-news (G_ "~a contents match:~%")) item)
       (report-hashes item local narinfos)))))

(define (summarize-report-list reports)
  "Display the overall summary of REPORTS."
  (let ((total         (length reports))
        (inconclusive  (count comparison-report-inconclusive? reports))
        (matches       (count comparison-report-match? reports))
        (discrepancies (count comparison-report-mismatch? reports)))
    (report (highlight (G_ "~h store items were analyzed:~%")) total)
    (report (highlight (G_ "  - ~h (~,1f%) were identical~%"))
            matches (* 100. (/ matches total)))
    (report ((if (zero? discrepancies) good-news bad-news)
             (G_ "  - ~h (~,1f%) differed~%"))
            discrepancies (* 100. (/ discrepancies total)))
    (report (G_ "  - ~h (~,1f%) were inconclusive~%")
            inconclusive (* 100. (/ inconclusive total)))))


;;;
;;; Command-line options.
;;;

(define (show-help)
  (display (G_ "Usage: guix challenge [PACKAGE...]
Challenge the substitutes for PACKAGE... provided by one or more servers.\n"))
  (display (G_ "
      --substitute-urls=URLS
                         compare build results with those at URLS"))
  (display (G_ "
  -v, --verbose          show details about successful comparisons"))
  (display (G_ "
      --diff=MODE        show differences according to MODE"))
  (newline)
  (display (G_ "
  -h, --help             display this help and exit"))
  (display (G_ "
  -V, --version          display version information and exit"))
  (newline)
  (show-bug-report-information))

(define %options
  (list  (option '(#\h "help") #f #f
                 (lambda args
                   (leave-on-EPIPE (show-help))
                   (exit 0)))
         (option '(#\V "version") #f #f
                 (lambda args
                   (show-version-and-exit "guix challenge")))

         (option '("diff") #t #f
                 (lambda (opt name arg result . rest)
                   (define mode
                     (match arg
                       ("none" (const #t))
                       ("simple" report-differing-files)
                       ("diffoscope" report-differing-files/external)
                       ((and (? (cut string-prefix? "/" <>)) command)
                        (cute report-differing-files/external <>
                              (string-tokenize command)))
                       (_ (leave (G_ "~a: unknown diff mode~%") arg))))

                   (apply values
                          (alist-cons 'difference-report mode result)
                          rest)))

         (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)))
         (option '("verbose" #\v) #f #f
                 (lambda (opt name arg result . rest)
                   (apply values
                          (alist-cons 'verbose? #t result)
                          rest)))))

(define %default-options
  `((system . ,(%current-system))
    (substitute-urls . ,%default-substitute-urls)
    (difference-report . ,report-differing-files)))


;;;
;;; Entry point.
;;;

(define-command (guix-challenge . args)
  (category packaging)
  (synopsis "challenge substitute servers, comparing their binaries")

  (with-error-handling
    (let* ((opts     (parse-command-line args %options (list %default-options)
                                         #:build-options? #f))
           (files    (filter-map (match-lambda
                                   (('argument . file) file)
                                   (_ #f))
                                 opts))
           (system   (assoc-ref opts 'system))
           (urls     (assoc-ref opts 'substitute-urls))
           (diff     (assoc-ref opts 'difference-report))
           (verbose? (assoc-ref opts 'verbose?)))
      (leave-on-EPIPE
       (with-store store
         ;; Disable grafts since substitute servers normally provide only
         ;; ungrafted stuff.
         (parameterize ((%graft? #f)
                        (current-terminal-columns (terminal-columns)))
           (let ((files (match files
                          (()
                           (warning
                            (G_ "no arguments specified, nothing to do~%"))
                           (exit 0))
                          (x
                           files))))
             (set-build-options store
                                #:use-substitutes? #f)

             (run-with-store store
               (mlet* %store-monad ((items   (mapm %store-monad
                                                   ensure-store-item files))
                                    (reports (compare-contents items urls)))
                 (for-each (cut summarize-report <> #:verbose? verbose?
                                #:report-differences diff)
                           reports)
                 (report "\n")
                 (summarize-report-list reports)

                 (exit (cond ((any comparison-report-mismatch? reports) 2)
                             ((every comparison-report-match? reports) 0)
                             (else 1))))
               #:system system))))))))

;;; challenge.scm ends here
