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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 pk-crypto)
#:use-module (guix config)
#:use-module ((guix utils) #:select (bytevector->base16-string))
#:use-module (system foreign)
#:use-module (rnrs bytevectors)
#:use-module (ice-9 match)
#:export (gcry-sexp?
string->gcry-sexp
gcry-sexp->string
number->gcry-sexp
bytevector->hash-data
sign
verify
generate-key
find-sexp-token))
;;; Commentary:
;;;
;;; Public key cryptographic routines from GNU Libgcrypt.
;;;;
;;; Libgcrypt uses s-expressions to represent key material, parameters, and
;;; data. We keep it as an opaque object rather than attempting to map them
;;; to Scheme s-expressions because (1) Libgcrypt sexps are stored in secure
;;; memory, and (2) the read syntax is different.
;;;
;;; Code:
;; Libgcrypt "s-expressions".
(define-wrapped-pointer-type <gcry-sexp>
gcry-sexp?
naked-pointer->gcry-sexp
gcry-sexp->pointer
(lambda (obj port)
;; Don't print OBJ's external representation: we don't want key material
;; to leak in backtraces and such.
(format port "#<gcry-sexp ~a | ~a>"
(number->string (object-address obj) 16)
(number->string (pointer-address (gcry-sexp->pointer obj))
16))))
(define libgcrypt-func
(let ((lib (dynamic-link %libgcrypt)))
(lambda (func)
"Return a pointer to symbol FUNC in libgcrypt."
(dynamic-func func lib))))
(define finalize-gcry-sexp!
(libgcrypt-func "gcry_sexp_release"))
(define-inlinable (pointer->gcry-sexp ptr)
"Return a <gcry-sexp> that wraps PTR."
(let* ((sexp (naked-pointer->gcry-sexp ptr))
(ptr* (gcry-sexp->pointer sexp)))
;; Did we already have a <gcry-sexp> object for PTR?
(when (equal? ptr ptr*)
;; No, so we can safely add a finalizer (in Guile 2.0.9
;; 'set-pointer-finalizer!' *adds* a finalizer rather than replacing the
;; existing one.)
(set-pointer-finalizer! ptr finalize-gcry-sexp!))
sexp))
(define string->gcry-sexp
(let* ((ptr (libgcrypt-func "gcry_sexp_new"))
(proc (pointer->procedure int ptr `(* * ,size_t ,int))))
(lambda (str)
"Parse STR and return the corresponding gcrypt s-expression."
(let* ((sexp (bytevector->pointer (make-bytevector (sizeof '*))))
(err (proc sexp (string->pointer str) 0 1)))
(if (= 0 err)
(pointer->gcry-sexp (dereference-pointer sexp))
(throw 'gcry-error err))))))
(define-syntax GCRYSEXP_FMT_ADVANCED
(identifier-syntax 3))
(define gcry-sexp->string
(let* ((ptr (libgcrypt-func "gcry_sexp_sprint"))
(proc (pointer->procedure size_t ptr `(* ,int * ,size_t))))
(lambda (sexp)
"Return a textual representation of SEXP."
(let loop ((len 1024))
(let* ((buf (bytevector->pointer (make-bytevector len)))
(size (proc (gcry-sexp->pointer sexp)
GCRYSEXP_FMT_ADVANCED buf len)))
(if (zero? size)
(loop (* len 2))
(pointer->string buf size "ISO-8859-1")))))))
(define (number->gcry-sexp number)
"Return an s-expression representing NUMBER."
(string->gcry-sexp (string-append "#" (number->string number 16) "#")))
(define* (bytevector->hash-data bv #:optional (hash-algo "sha256"))
"Given BV, a bytevector containing a hash, return an s-expression suitable
for use as the data for 'sign'."
(string->gcry-sexp
(format #f "(data (flags pkcs1) (hash \"~a\" #~a#))"
hash-algo
(bytevector->base16-string bv))))
(define sign
(let* ((ptr (libgcrypt-func "gcry_pk_sign"))
(proc (pointer->procedure int ptr '(* * *))))
(lambda (data secret-key)
"Sign DATA (an s-expression) with SECRET-KEY (an s-expression whose car
is 'private-key'.)"
(let* ((sig (bytevector->pointer (make-bytevector (sizeof '*))))
(err (proc sig (gcry-sexp->pointer data)
(gcry-sexp->pointer secret-key))))
(if (= 0 err)
(pointer->gcry-sexp (dereference-pointer sig))
(throw 'gry-error err))))))
(define verify
(let* ((ptr (libgcrypt-func "gcry_pk_verify"))
(proc (pointer->procedure int ptr '(* * *))))
(lambda (signature data public-key)
"Verify that SIGNATURE is a signature of DATA with PUBLIC-KEY, all of
which are gcrypt s-expressions."
(zero? (proc (gcry-sexp->pointer signature)
(gcry-sexp->pointer data)
(gcry-sexp->pointer public-key))))))
(define generate-key
(let* ((ptr (libgcrypt-func "gcry_pk_genkey"))
(proc (pointer->procedure int ptr '(* *))))
(lambda (params)
"Return as an s-expression a new key pair for PARAMS. PARAMS must be an
s-expression like: (genkey (rsa (nbits 4:2048)))."
(let* ((key (bytevector->pointer (make-bytevector (sizeof '*))))
(err (proc key (gcry-sexp->pointer params))))
(if (zero? err)
(pointer->gcry-sexp (dereference-pointer key))
(throw 'gcry-error err))))))
(define find-sexp-token
(let* ((ptr (libgcrypt-func "gcry_sexp_find_token"))
(proc (pointer->procedure '* ptr `(* * ,size_t))))
(lambda (sexp token)
"Find in SEXP the first element whose 'car' is TOKEN and return it;
return #f if not found."
(let* ((token (string->pointer (symbol->string token)))
(res (proc (gcry-sexp->pointer sexp) token 0)))
(if (null-pointer? res)
#f
(pointer->gcry-sexp res))))))
;;; pk-crypto.scm ends here
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