guix-devel/guix/scripts/publish.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015 David Thompson <davet@gnu.org>
;;; Copyright © 2015, 2016, 2017 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 publish)
  #:use-module ((system repl server) #:prefix repl:)
  #:use-module (ice-9 binary-ports)
  #:use-module (ice-9 format)
  #:use-module (ice-9 match)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 rdelim)
  #:use-module (ice-9 threads)
  #:use-module (rnrs bytevectors)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-2)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-9 gnu)
  #:use-module (srfi srfi-19)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-37)
  #:use-module (web http)
  #:use-module (web request)
  #:use-module (web response)
  #:use-module (web server)
  #:use-module (web uri)
  #:autoload   (sxml simple) (sxml->xml)
  #:use-module (guix base32)
  #:use-module (guix base64)
  #:use-module (guix config)
  #:use-module (guix derivations)
  #:use-module (guix hash)
  #:use-module (guix pki)
  #:use-module (guix pk-crypto)
  #:use-module (guix workers)
  #:use-module (guix store)
  #:use-module ((guix serialization) #:select (write-file))
  #:use-module (guix zlib)
  #:use-module (guix cache)
  #:use-module (guix ui)
  #:use-module (guix scripts)
  #:use-module ((guix utils)
                #:select (with-atomic-file-output compressed-file?))
  #:use-module ((guix build utils)
                #:select (dump-port mkdir-p find-files))
  #:use-module ((guix build syscalls) #:select (set-thread-name))
  #:export (%public-key
            %private-key

            guix-publish))

(define (show-help)
  (format #t (G_ "Usage: guix publish [OPTION]...
Publish ~a over HTTP.\n") %store-directory)
  (display (G_ "
  -p, --port=PORT        listen on PORT"))
  (display (G_ "
      --listen=HOST      listen on the network interface for HOST"))
  (display (G_ "
  -u, --user=USER        change privileges to USER as soon as possible"))
  (display (G_ "
  -C, --compression[=LEVEL]
                         compress archives at LEVEL"))
  (display (G_ "
  -c, --cache=DIRECTORY  cache published items to DIRECTORY"))
  (display (G_ "
      --workers=N        use N workers to bake items"))
  (display (G_ "
      --ttl=TTL          announce narinfos can be cached for TTL seconds"))
  (display (G_ "
      --nar-path=PATH    use PATH as the prefix for nar URLs"))
  (display (G_ "
      --public-key=FILE  use FILE as the public key for signatures"))
  (display (G_ "
      --private-key=FILE use FILE as the private key for signatures"))
  (display (G_ "
  -r, --repl[=PORT]      spawn REPL server on PORT"))
  (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 (getaddrinfo* host)
  "Like 'getaddrinfo', but properly report errors."
  (catch 'getaddrinfo-error
    (lambda ()
      (getaddrinfo host))
    (lambda (key error)
      (leave (G_ "lookup of host '~a' failed: ~a~%")
             host (gai-strerror error)))))

;; Nar compression parameters.
(define-record-type <compression>
  (compression type level)
  compression?
  (type   compression-type)
  (level  compression-level))

(define %no-compression
  (compression 'none 0))

(define %default-gzip-compression
  ;; Since we compress on the fly, default to fast compression.
  (compression 'gzip 3))

(define (actual-compression item requested)
  "Return the actual compression used for ITEM, which may be %NO-COMPRESSION
if ITEM is already compressed."
  (if (compressed-file? item)
      %no-compression
      requested))

(define %options
  (list (option '(#\h "help") #f #f
                (lambda _
                  (show-help)
                  (exit 0)))
        (option '(#\V "version") #f #f
                (lambda _
                  (show-version-and-exit "guix publish")))
        (option '(#\u "user") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'user arg result)))
        (option '(#\p "port") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'port (string->number* arg) result)))
        (option '("listen") #t #f
                (lambda (opt name arg result)
                  (match (getaddrinfo* arg)
                    ((info _ ...)
                     (alist-cons 'address (addrinfo:addr info)
                                 result))
                    (()
                     (leave (G_ "lookup of host '~a' returned nothing")
                            name)))))
        (option '(#\C "compression") #f #t
                (lambda (opt name arg result)
                  (match (if arg (string->number* arg) 3)
                    (0
                     (alist-cons 'compression %no-compression result))
                    (level
                     (if (zlib-available?)
                         (alist-cons 'compression
                                     (compression 'gzip level)
                                     result)
                         (begin
                           (warning (G_ "zlib support is missing; \
compression disabled~%"))
                           result))))))
        (option '(#\c "cache") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'cache arg result)))
        (option '("workers") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'workers (string->number* arg)
                              result)))
        (option '("ttl") #t #f
                (lambda (opt name arg result)
                  (let ((duration (string->duration arg)))
                    (unless duration
                      (leave (G_ "~a: invalid duration~%") arg))
                    (alist-cons 'narinfo-ttl (time-second duration)
                                result))))
        (option '("nar-path") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'nar-path arg result)))
        (option '("public-key") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'public-key-file arg result)))
        (option '("private-key" "secret-key") #t #f
                (lambda (opt name arg result)
                  (alist-cons 'private-key-file arg result)))
        (option '(#\r "repl") #f #t
                (lambda (opt name arg result)
                  ;; If port unspecified, use default Guile REPL port.
                  (let ((port (and arg (string->number* arg))))
                    (alist-cons 'repl (or port 37146) result))))))

(define %default-options
  `((port . 8080)

    ;; By default, serve nars under "/nar".
    (nar-path . "nar")

    (public-key-file . ,%public-key-file)
    (private-key-file . ,%private-key-file)

    ;; Default to fast & low compression.
    (compression . ,(if (zlib-available?)
                        %default-gzip-compression
                        %no-compression))

    ;; Default number of workers when caching is enabled.
    (workers . ,(current-processor-count))

    (address . ,(make-socket-address AF_INET INADDR_ANY 0))
    (repl . #f)))

;; The key pair used to sign narinfos.
(define %private-key
  (make-parameter #f))
(define %public-key
  (make-parameter #f))

(define %nix-cache-info
  `(("StoreDir" . ,%store-directory)
    ("WantMassQuery" . 0)
    ("Priority" . 100)))

(define (signed-string s)
  "Sign the hash of the string S with the daemon's key."
  (let* ((public-key (%public-key))
         (hash (bytevector->hash-data (sha256 (string->utf8 s))
                                      #:key-type (key-type public-key))))
    (signature-sexp hash (%private-key) public-key)))

(define base64-encode-string
  (compose base64-encode string->utf8))

(define* (narinfo-string store store-path key
                         #:key (compression %no-compression)
                         (nar-path "nar") file-size)
  "Generate a narinfo key/value string for STORE-PATH; an exception is raised
if STORE-PATH is invalid.  Produce a URL that corresponds to COMPRESSION.  The
narinfo is signed with KEY.  NAR-PATH specifies the prefix for nar URLs.
Optionally, FILE-SIZE can specify the size in bytes of the compressed NAR; it
informs the client of how much needs to be downloaded."
  (let* ((path-info  (query-path-info store store-path))
         (compression (actual-compression store-path compression))
         (url        (encode-and-join-uri-path
                      `(,@(split-and-decode-uri-path nar-path)
                        ,@(match compression
                            (($ <compression> 'none)
                             '())
                            (($ <compression> type)
                             (list (symbol->string type))))
                        ,(basename store-path))))
         (hash       (bytevector->nix-base32-string
                      (path-info-hash path-info)))
         (size       (path-info-nar-size path-info))
         (file-size  (or file-size
                         (and (eq? compression %no-compression) size)))
         (references (string-join
                      (map basename (path-info-references path-info))
                      " "))
         (deriver    (path-info-deriver path-info))
         (base-info  (format #f
                             "\
StorePath: ~a
URL: ~a
Compression: ~a
NarHash: sha256:~a
NarSize: ~d
References: ~a~%~a"
                             store-path url
                             (compression-type compression)
                             hash size references
                             (if file-size
                                 (format #f "FileSize: ~a~%" file-size)
                                 "")))
         ;; Do not render a "Deriver" or "System" line if we are rendering
         ;; info for a derivation.
         (info       (if (not deriver)
                         base-info
                         (catch 'system-error
                           (lambda ()
                             (let ((drv (read-derivation-from-file deriver)))
                               (format #f "~aSystem: ~a~%Deriver: ~a~%"
                                       base-info (derivation-system drv)
                                       (basename deriver))))
                           (lambda args
                             ;; DERIVER might be missing, but that's fine:
                             ;; it's only used for <substitutable> where it's
                             ;; optional.  'System' is currently unused.
                             (if (= ENOENT (system-error-errno args))
                                 base-info
                                 (apply throw args))))))
         (signature  (base64-encode-string
                      (canonical-sexp->string (signed-string info)))))
    (format #f "~aSignature: 1;~a;~a~%" info (gethostname) signature)))

(define* (not-found request
                    #:key (phrase "Resource not found")
                    ttl)
  "Render 404 response for REQUEST."
  (values (build-response #:code 404
                          #:headers (if ttl
                                        `((cache-control (max-age . ,ttl)))
                                        '()))
          (string-append phrase ": "
                         (uri-path (request-uri request)))))

(define (render-nix-cache-info)
  "Render server information."
  (values '((content-type . (text/plain)))
          (lambda (port)
            (for-each (match-lambda
                       ((key . value)
                        (format port "~a: ~a~%" key value)))
                      %nix-cache-info))))

(define* (render-narinfo store request hash
                         #:key ttl (compression %no-compression)
                         (nar-path "nar"))
  "Render metadata for the store path corresponding to HASH.  If TTL is true,
advertise it as the maximum validity period (in seconds) via the
'Cache-Control' header.  This allows 'guix substitute' to cache it for an
appropriate duration.  NAR-PATH specifies the prefix for nar URLs."
  (let ((store-path (hash-part->path store hash)))
    (if (string-null? store-path)
        (not-found request)
        (values `((content-type . (application/x-nix-narinfo))
                  ,@(if ttl
                        `((cache-control (max-age . ,ttl)))
                        '()))
                (cut display
                  (narinfo-string store store-path (%private-key)
                                  #:nar-path nar-path
                                  #:compression compression)
                  <>)))))

(define* (nar-cache-file directory item
                             #:key (compression %no-compression))
  (string-append directory "/"
                 (symbol->string (compression-type compression))
                 "/" (basename item) ".nar"))

(define* (narinfo-cache-file directory item
                             #:key (compression %no-compression))
  (string-append directory "/"
                 (symbol->string (compression-type compression))
                 "/" (basename item)
                 ".narinfo"))

(define run-single-baker
  (let ((baking (make-weak-value-hash-table))
        (mutex  (make-mutex)))
    (lambda (item thunk)
      "Run THUNK, which is supposed to bake ITEM, but make sure only one
thread is baking ITEM at a given time."
      (define selected?
        (with-mutex mutex
          (and (not (hash-ref baking item))
               (begin
                 (hash-set! baking item (current-thread))
                 #t))))

      (when selected?
        (dynamic-wind
          (const #t)
          thunk
          (lambda ()
            (with-mutex mutex
              (hash-remove! baking item))))))))

(define-syntax-rule (single-baker item exp ...)
  "Bake ITEM by evaluating EXP, but make sure there's only one baker for ITEM
at a time."
  (run-single-baker item (lambda () exp ...)))


(define (narinfo-files cache)
  "Return the list of .narinfo files under CACHE."
  (if (file-is-directory? cache)
      (find-files cache
                  (lambda (file stat)
                    (string-suffix? ".narinfo" file)))
      '()))

(define (nar-expiration-time ttl)
  "Return the narinfo expiration time (in seconds since the Epoch).  The
expiration time is +inf.0 when passed an item that is still in the store; in
other cases, it is the last-access time of the item plus TTL.

This policy allows us to keep cached nars that correspond to valid store
items.  Failing that, we could eventually have to recompute them and return
404 in the meantime."
  (let ((expiration-time (file-expiration-time ttl)))
    (lambda (file)
      (let ((item (string-append (%store-prefix) "/"
                                 (basename file ".narinfo"))))
        ;; Note: We don't need to use 'valid-path?' here because FILE would
        ;; not exist if ITEM were not valid in the first place.
        (if (file-exists? item)
            +inf.0
            (expiration-time file))))))

(define* (render-narinfo/cached store request hash
                                #:key ttl (compression %no-compression)
                                (nar-path "nar")
                                cache pool)
  "Respond to the narinfo request for REQUEST.  If the narinfo is available in
CACHE, then send it; otherwise, return 404 and \"bake\" that nar and narinfo
requested using POOL."
  (define (delete-entry narinfo)
    ;; Delete NARINFO and the corresponding nar from CACHE.
    (let ((nar (string-append (string-drop-right narinfo
                                                 (string-length ".narinfo"))
                              ".nar")))
      (delete-file* narinfo)
      (delete-file* nar)))

  (let* ((item        (hash-part->path store hash))
         (compression (actual-compression item compression))
         (cached      (and (not (string-null? item))
                           (narinfo-cache-file cache item
                                               #:compression compression))))
    (cond ((string-null? item)
           (not-found request))
          ((file-exists? cached)
           ;; Narinfo is in cache, send it.
           (values `((content-type . (application/x-nix-narinfo))
                     ,@(if ttl
                           `((cache-control (max-age . ,ttl)))
                           '()))
                   (lambda (port)
                     (display (call-with-input-file cached
                                read-string)
                              port))))
          ((and (file-exists? item)        ;cheaper than the 'valid-path?' RPC
                (valid-path? store item))
           ;; Nothing in cache: bake the narinfo and nar in the background and
           ;; return 404.
           (eventually pool
             (single-baker item
               ;; Check whether CACHED has been produced in the meantime.
               (unless (file-exists? cached)
                 ;; (format #t "baking ~s~%" item)
                 (bake-narinfo+nar cache item
                                   #:ttl ttl
                                   #:compression compression
                                   #:nar-path nar-path)))

             (when ttl
               (single-baker 'cache-cleanup
                 (maybe-remove-expired-cache-entries cache
                                                     narinfo-files
                                                     #:entry-expiration
                                                     (nar-expiration-time ttl)
                                                     #:delete-entry delete-entry
                                                     #:cleanup-period ttl))))
           (not-found request
                      #:phrase "We're baking it"
                      #:ttl 300))              ;should be available within 5m
          (else
           (not-found request)))))

(define* (bake-narinfo+nar cache item
                           #:key ttl (compression %no-compression)
                           (nar-path "/nar"))
  "Write the narinfo and nar for ITEM to CACHE."
  (let* ((compression (actual-compression item compression))
         (nar         (nar-cache-file cache item
                                      #:compression compression))
         (narinfo     (narinfo-cache-file cache item
                                          #:compression compression)))

    (mkdir-p (dirname nar))
    (match (compression-type compression)
      ('gzip
       ;; Note: the file port gets closed along with the gzip port.
       (call-with-gzip-output-port (open-output-file (string-append nar ".tmp"))
         (lambda (port)
           (write-file item port))
         #:level (compression-level compression)
         #:buffer-size (* 128 1024))
       (rename-file (string-append nar ".tmp") nar))
      ('none
       ;; When compression is disabled, we retrieve files directly from the
       ;; store; no need to cache them.
       #t))

    (mkdir-p (dirname narinfo))
    (with-atomic-file-output narinfo
      (lambda (port)
        ;; Open a new connection to the store.  We cannot reuse the main
        ;; thread's connection to the store since we would end up sending
        ;; stuff concurrently on the same channel.
        (with-store store
          (display (narinfo-string store item
                                   (%private-key)
                                   #:nar-path nar-path
                                   #:compression compression
                                   #:file-size (and=> (stat nar #f)
                                                      stat:size))
                   port))))))

;; XXX: Declare the 'Guix-Compression' HTTP header, which is in fact for
;; internal consumption: it allows us to pass the compression info to
;; 'http-write', as part of the workaround to <http://bugs.gnu.org/21093>.
(declare-header! "Guix-Nar-Compression"
                 (lambda (str)
                   (match (call-with-input-string str read)
                     (('compression type level)
                      (compression type level))))
                 compression?
                 (lambda (compression port)
                   (match compression
                     (($ <compression> type level)
                      (write `(compression ,type ,level) port)))))

(define* (render-nar store request store-item
                     #:key (compression %no-compression))
  "Render archive of the store path corresponding to STORE-ITEM."
  (let ((store-path (string-append %store-directory "/" store-item)))
    ;; The ISO-8859-1 charset *must* be used otherwise HTTP clients will
    ;; interpret the byte stream as UTF-8 and arbitrarily change invalid byte
    ;; sequences.
    (if (valid-path? store store-path)
        (values `((content-type . (application/x-nix-archive
                                   (charset . "ISO-8859-1")))
                  (guix-nar-compression . ,compression))
                ;; XXX: We're not returning the actual contents, deferring
                ;; instead to 'http-write'.  This is a hack to work around
                ;; <http://bugs.gnu.org/21093>.
                store-path)
        (not-found request))))

(define* (render-nar/cached store cache request store-item
                            #:key (compression %no-compression))
  "Respond to REQUEST with a nar for STORE-ITEM.  If the nar is in CACHE,
return it; otherwise, return 404."
  (let ((cached (nar-cache-file cache store-item
                                #:compression compression)))
    (if (file-exists? cached)
        (values `((content-type . (application/octet-stream
                                   (charset . "ISO-8859-1"))))
                ;; XXX: We're not returning the actual contents, deferring
                ;; instead to 'http-write'.  This is a hack to work around
                ;; <http://bugs.gnu.org/21093>.
                cached)
        (not-found request))))

(define (render-content-addressed-file store request
                                       name algo hash)
  "Return the content of the result of the fixed-output derivation NAME that
has the given HASH of type ALGO."
  ;; TODO: Support other hash algorithms.
  (if (and (eq? algo 'sha256) (= 32 (bytevector-length hash)))
      (let ((item (fixed-output-path name hash
                                     #:hash-algo algo
                                     #:recursive? #f)))
        (if (valid-path? store item)
            (values `((content-type . (application/octet-stream
                                       (charset . "ISO-8859-1"))))
                    ;; XXX: We're not returning the actual contents, deferring
                    ;; instead to 'http-write'.  This is a hack to work around
                    ;; <http://bugs.gnu.org/21093>.
                    item)
            (not-found request)))
      (not-found request)))

(define (render-home-page request)
  "Render the home page."
  (values `((content-type . (text/html (charset . "UTF-8"))))
          (call-with-output-string
            (lambda (port)
              (sxml->xml '(html
                           (head (title "GNU Guix Substitute Server"))
                           (body
                            (h1 "GNU Guix Substitute Server")
                            (p "Hi, "
                               (a (@ (href
                                      "https://gnu.org/s/guix/manual/html_node/Invoking-guix-publish.html"))
                                  (tt "guix publish"))
                               " speaking.  Welcome!")))
                         port)))))

(define (extract-narinfo-hash str)
  "Return the hash within the narinfo resource string STR, or false if STR
is invalid."
  (and (string-suffix? ".narinfo" str)
       (let ((base (string-drop-right str 8)))
         (and (string-every %nix-base32-charset base)
              base))))

(define (get-request? request)
  "Return #t if REQUEST uses the GET method."
  (eq? (request-method request) 'GET))

(define (request-path-components request)
  "Split the URI path of REQUEST into a list of component strings.  For
example: \"/foo/bar\" yields '(\"foo\" \"bar\")."
  (split-and-decode-uri-path (uri-path (request-uri request))))


;;;
;;; Server.
;;;

(define %http-write
  (@@ (web server http) http-write))

(define (sans-content-length response)
  "Return RESPONSE without its 'content-length' header."
  (set-field response (response-headers)
             (alist-delete 'content-length
                           (response-headers response)
                           eq?)))

(define (with-content-length response length)
  "Return RESPONSE with a 'content-length' header set to LENGTH."
  (set-field response (response-headers)
             (alist-cons 'content-length length
                         (alist-delete 'content-length
                                       (response-headers response)
                                       eq?))))

(define-syntax-rule (swallow-EPIPE exp ...)
  "Swallow EPIPE errors raised by EXP..."
  (catch 'system-error
    (lambda ()
      exp ...)
    (lambda args
      (if (= EPIPE (system-error-errno args))
          (values)
          (apply throw args)))))

(define-syntax-rule (swallow-zlib-error exp ...)
  "Swallow 'zlib-error' exceptions raised by EXP..."
  (catch 'zlib-error
    (lambda ()
      exp ...)
    (const #f)))

(define (nar-response-port response)
  "Return a port on which to write the body of RESPONSE, the response of a
/nar request, according to COMPRESSION."
  (match (assoc-ref (response-headers response) 'guix-nar-compression)
    (($ <compression> 'gzip level)
     ;; Note: We cannot used chunked encoding here because
     ;; 'make-gzip-output-port' wants a file port.
     (make-gzip-output-port (response-port response)
                            #:level level
                            #:buffer-size (* 64 1024)))
    (($ <compression> 'none)
     (response-port response))
    (#f
     (response-port response))))

(define (http-write server client response body)
  "Write RESPONSE and BODY to CLIENT, possibly in a separate thread to avoid
blocking."
  (match (response-content-type response)
    (('application/x-nix-archive . _)
     ;; Sending the the whole archive can take time so do it in a separate
     ;; thread so that the main thread can keep working in the meantime.
     (call-with-new-thread
      (lambda ()
        (set-thread-name "publish nar")
        (let* ((response (write-response (sans-content-length response)
                                         client))
               (port     (begin
                           (force-output client)
                           (nar-response-port response))))
          ;; XXX: Given our ugly workaround for <http://bugs.gnu.org/21093> in
          ;; 'render-nar', BODY here is just the file name of the store item.
          ;; We call 'write-file' from here because we know that's the only
          ;; way to avoid building the whole nar in memory, which could
          ;; quickly become a real problem.  As a bonus, we even do
          ;; sendfile(2) directly from the store files to the socket.
          (swallow-zlib-error
           (swallow-EPIPE
            (write-file (utf8->string body) port)))
          (swallow-zlib-error
           (close-port port))
          (values)))))
    (('application/octet-stream . _)
     ;; Send a raw file in a separate thread.
     (call-with-new-thread
      (lambda ()
        (set-thread-name "publish file")
        (catch 'system-error
          (lambda ()
            (call-with-input-file (utf8->string body)
              (lambda (input)
                (let* ((size     (stat:size (stat input)))
                       (response (write-response (with-content-length response
                                                                      size)
                                                 client))
                       (output   (response-port response)))
                  (if (file-port? output)
                      (sendfile output input size)
                      (dump-port input output))
                  (close-port output)
                  (values)))))
          (lambda args
            ;; If the file was GC'd behind our back, that's fine.  Likewise if
            ;; the client closes the connection.
            (unless (memv (system-error-errno args)
                          (list ENOENT EPIPE ECONNRESET))
              (apply throw args))
            (values))))))
    (_
     ;; Handle other responses sequentially.
     (%http-write server client response body))))

(define-server-impl concurrent-http-server
  ;; A variant of Guile's built-in HTTP server that offloads possibly long
  ;; responses to a different thread.
  (@@ (web server http) http-open)
  (@@ (web server http) http-read)
  http-write
  (@@ (web server http) http-close))

(define* (make-request-handler store
                               #:key
                               cache pool
                               narinfo-ttl
                               (nar-path "nar")
                               (compression %no-compression))
  (define nar-path?
    (let ((expected (split-and-decode-uri-path nar-path)))
      (cut equal? expected <>)))

  (lambda (request body)
    (format #t "~a ~a~%"
            (request-method request)
            (uri-path (request-uri request)))
    (if (get-request? request)                    ;reject POST, PUT, etc.
        (match (request-path-components request)
          ;; /nix-cache-info
          (("nix-cache-info")
           (render-nix-cache-info))
          ;; /
          ((or () ("index.html"))
           (render-home-page request))
          ;; /<hash>.narinfo
          (((= extract-narinfo-hash (? string? hash)))
           ;; TODO: Register roots for HASH that will somehow remain for
           ;; NARINFO-TTL.
           (if cache
               (render-narinfo/cached store request hash
                                      #:cache cache
                                      #:pool pool
                                      #:ttl narinfo-ttl
                                      #:nar-path nar-path
                                      #:compression compression)
               (render-narinfo store request hash
                               #:ttl narinfo-ttl
                               #:nar-path nar-path
                               #:compression compression)))
          ;; /nar/file/NAME/sha256/HASH
          (("file" name "sha256" hash)
           (guard (c ((invalid-base32-character? c)
                      (not-found request)))
             (let ((hash (nix-base32-string->bytevector hash)))
               (render-content-addressed-file store request
                                              name 'sha256 hash))))

          ;; Use different URLs depending on the compression type.  This
          ;; guarantees that /nar URLs remain valid even when 'guix publish'
          ;; is restarted with different compression parameters.

          ;; /nar/gzip/<store-item>
          ((components ... "gzip" store-item)
           (if (and (nar-path? components) (zlib-available?))
               (let ((compression (match compression
                                    (($ <compression> 'gzip)
                                     compression)
                                    (_
                                     %default-gzip-compression))))
                 (if cache
                     (render-nar/cached store cache request store-item
                                        #:compression compression)
                     (render-nar store request store-item
                                 #:compression compression)))
               (not-found request)))

          ;; /nar/<store-item>
          ((components ... store-item)
           (if (nar-path? components)
               (render-nar store request store-item
                           #:compression %no-compression)
               (not-found request)))

          (x (not-found request)))
        (not-found request))))

(define* (run-publish-server socket store
                             #:key (compression %no-compression)
                             (nar-path "nar") narinfo-ttl
                             cache pool)
  (run-server (make-request-handler store
                                    #:cache cache
                                    #:pool pool
                                    #:nar-path nar-path
                                    #:narinfo-ttl narinfo-ttl
                                    #:compression compression)
              concurrent-http-server
              `(#:socket ,socket)))

(define (open-server-socket address)
  "Return a TCP socket bound to ADDRESS, a socket address."
  (let ((sock (socket (sockaddr:fam address) SOCK_STREAM 0)))
    (setsockopt sock SOL_SOCKET SO_REUSEADDR 1)
    (bind sock address)
    sock))

(define (gather-user-privileges user)
  "Switch to the identity of USER, a user name."
  (catch 'misc-error
    (lambda ()
      (let ((user (getpw user)))
        (setgroups #())
        (setgid (passwd:gid user))
        (setuid (passwd:uid user))))
    (lambda (key proc message args . rest)
      (leave (G_ "user '~a' not found: ~a~%")
             user (apply format #f message args)))))

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

(define (guix-publish . args)
  (with-error-handling
    (let* ((opts    (args-fold* args %options
                                (lambda (opt name arg result)
                                  (leave (G_ "~A: unrecognized option~%") name))
                                (lambda (arg result)
                                  (leave (G_ "~A: extraneous argument~%") arg))
                                %default-options))
           (user    (assoc-ref opts 'user))
           (port    (assoc-ref opts 'port))
           (ttl     (assoc-ref opts 'narinfo-ttl))
           (compression (assoc-ref opts 'compression))
           (address (let ((addr (assoc-ref opts 'address)))
                      (make-socket-address (sockaddr:fam addr)
                                           (sockaddr:addr addr)
                                           port)))
           (socket  (open-server-socket address))
           (nar-path  (assoc-ref opts 'nar-path))
           (repl-port (assoc-ref opts 'repl))
           (cache     (assoc-ref opts 'cache))
           (workers   (assoc-ref opts 'workers))

           ;; Read the key right away so that (1) we fail early on if we can't
           ;; access them, and (2) we can then drop privileges.
           (public-key  (read-file-sexp (assoc-ref opts 'public-key-file)))
           (private-key (read-file-sexp (assoc-ref opts 'private-key-file))))

      (when user
        ;; Now that we've read the key material and opened the socket, we can
        ;; drop privileges.
        (gather-user-privileges user))

      (when (zero? (getuid))
        (warning (G_ "server running as root; \
consider using the '--user' option!~%")))

      (parameterize ((%public-key public-key)
                     (%private-key private-key))
        (format #t (G_ "publishing ~a on ~a, port ~d~%")
                %store-directory
                (inet-ntop (sockaddr:fam address) (sockaddr:addr address))
                (sockaddr:port address))
        (when repl-port
          (repl:spawn-server (repl:make-tcp-server-socket #:port repl-port)))

        ;; Set the name of the main thread.
        (set-thread-name "guix publish")

        (with-store store
          (run-publish-server socket store
                              #:cache cache
                              #:pool (and cache (make-pool workers
                                                           #:thread-name
                                                           "publish worker"))
                              #:nar-path nar-path
                              #:compression compression
                              #:narinfo-ttl ttl))))))

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