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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013 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 pki)
#:use-module (guix config)
#:use-module (guix pk-crypto)
#:use-module ((guix utils) #:select (with-atomic-file-output))
#:use-module (ice-9 match)
#:use-module (rnrs io ports)
#:export (%public-key-file
current-acl
public-keys->acl
acl->public-keys
signature-sexp
authorized-key?))
;;; Commentary:
;;;
;;; Public key infrastructure for the authentication and authorization of
;;; archive imports. This is essentially a subset of SPKI for our own
;;; purposes (see <http://theworld.com/~cme/spki.txt> and
;;; <http://www.ietf.org/rfc/rfc2693.txt>.)
;;;
;;; Code:
(define (acl-entry-sexp public-key)
"Return a SPKI-style ACL entry sexp for PUBLIC-KEY, authorizing imports
signed by the corresponding secret key (see the IETF draft at
<http://theworld.com/~cme/spki.txt> for the ACL format.)"
;; Note: We always use PUBLIC-KEY to designate the subject. Someday we may
;; want to have name certificates and to use subject names instead of
;; complete keys.
(string->canonical-sexp
(format #f
"(entry ~a (tag (guix import)))"
(canonical-sexp->string public-key))))
(define (acl-sexp entries)
"Return an ACL sexp from ENTRIES, a list of 'entry' sexps."
(string->canonical-sexp
(string-append "(acl "
(string-join (map canonical-sexp->string entries))
")")))
(define (public-keys->acl keys)
"Return an ACL canonical sexp that lists all of KEYS with a '(guix import)'
tag---meaning that all of KEYS are authorized for archive imports. Each
element in KEYS must be a canonical sexp with type 'public-key'."
(acl-sexp (map acl-entry-sexp keys)))
(define %acl-file
(string-append %config-directory "/acl"))
(define %public-key-file
(string-append %config-directory "/signing-key.pub"))
(define (ensure-acl)
"Make sure the ACL file exists, and create an initialized one if needed."
(unless (file-exists? %acl-file)
;; If there's no public key file, don't attempt to create the ACL.
(when (file-exists? %public-key-file)
(let ((public-key (call-with-input-file %public-key-file
(compose string->canonical-sexp
get-string-all))))
(with-atomic-file-output %acl-file
(lambda (port)
(display (canonical-sexp->string
(public-keys->acl (list public-key)))
port)))))))
(define (current-acl)
"Return the current ACL as a canonical sexp."
(ensure-acl)
(if (file-exists? %acl-file)
(call-with-input-file %acl-file
(compose string->canonical-sexp
get-string-all))
(public-keys->acl '()))) ; the empty ACL
(define (acl->public-keys acl)
"Return the public keys (as canonical sexps) listed in ACL with the '(guix
import)' tag."
(match (canonical-sexp->sexp acl)
(('acl
('entry subject-keys
('tag ('guix 'import)))
...)
(map sexp->canonical-sexp subject-keys))
(_
(error "invalid access-control list" acl))))
(define* (authorized-key? key
#:optional (acl (current-acl)))
"Return #t if KEY (a canonical sexp) is an authorized public key for archive
imports according to ACL."
(let ((key (canonical-sexp->sexp key)))
(match (canonical-sexp->sexp acl)
(('acl
('entry subject-keys
('tag ('guix 'import)))
...)
(not (not (member key subject-keys))))
(_
(error "invalid access-control list" acl)))))
(define (signature-sexp data secret-key public-key)
"Return a SPKI-style sexp for the signature of DATA with SECRET-KEY that
includes DATA, the actual signature value (with a 'sig-val' tag), and
PUBLIC-KEY (see <http://theworld.com/~cme/spki.txt> for examples.)"
(string->canonical-sexp
(format #f
"(signature ~a ~a ~a)"
(canonical-sexp->string data)
(canonical-sexp->string (sign data secret-key))
(canonical-sexp->string public-key))))
;;; pki.scm ends here
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