;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2013 Ludovic Courtès ;;; ;;; 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 . (define-module (guix pk-crypto) #:use-module (guix config) #:use-module ((guix utils) #:select (bytevector->base16-string base16-string->bytevector)) #:use-module (system foreign) #:use-module (rnrs bytevectors) #:use-module (ice-9 match) #:export (canonical-sexp? string->canonical-sexp canonical-sexp->string number->canonical-sexp canonical-sexp-car canonical-sexp-cdr canonical-sexp-nth canonical-sexp-nth-data canonical-sexp-length canonical-sexp-null? canonical-sexp-list? bytevector->hash-data hash-data->bytevector sign verify generate-key find-sexp-token)) ;;; Commentary: ;;; ;;; Public key cryptographic routines from GNU Libgcrypt. ;;;; ;;; Libgcrypt uses "canonical 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. ;;; ;;; Canonical sexps were defined by Rivest et al. in the IETF draft at ;;; for the purposes of SPKI ;;; (see .) ;;; ;;; Code: ;; Libgcrypt "s-expressions". (define-wrapped-pointer-type canonical-sexp? naked-pointer->canonical-sexp canonical-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 "#" (number->string (object-address obj) 16) (number->string (pointer-address (canonical-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-canonical-sexp! (libgcrypt-func "gcry_sexp_release")) (define-inlinable (pointer->canonical-sexp ptr) "Return a that wraps PTR." (let* ((sexp (naked-pointer->canonical-sexp ptr)) (ptr* (canonical-sexp->pointer sexp))) ;; Did we already have a 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-canonical-sexp!)) sexp)) (define string->canonical-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->canonical-sexp (dereference-pointer sexp)) (throw 'gcry-error err)))))) (define-syntax GCRYSEXP_FMT_ADVANCED (identifier-syntax 3)) (define canonical-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 (canonical-sexp->pointer sexp) GCRYSEXP_FMT_ADVANCED buf len))) (if (zero? size) (loop (* len 2)) (pointer->string buf size "ISO-8859-1"))))))) (define canonical-sexp-car (let* ((ptr (libgcrypt-func "gcry_sexp_car")) (proc (pointer->procedure '* ptr '(*)))) (lambda (lst) "Return the first element of LST, an sexp, if that element is a list; return #f if LST or its first element is not a list (this is different from the usual Lisp 'car'.)" (let ((result (proc (canonical-sexp->pointer lst)))) (if (null-pointer? result) #f (pointer->canonical-sexp result)))))) (define canonical-sexp-cdr (let* ((ptr (libgcrypt-func "gcry_sexp_cdr")) (proc (pointer->procedure '* ptr '(*)))) (lambda (lst) "Return the tail of LST, an sexp, or #f if LST is not a list." (let ((result (proc (canonical-sexp->pointer lst)))) (if (null-pointer? result) #f (pointer->canonical-sexp result)))))) (define canonical-sexp-nth (let* ((ptr (libgcrypt-func "gcry_sexp_nth")) (proc (pointer->procedure '* ptr `(* ,int)))) (lambda (lst index) "Return the INDEXth nested element of LST, an s-expression. Return #f if that element does not exist, or if it's an atom. (Note: this is obviously different from Scheme's 'list-ref'.)" (let ((result (proc (canonical-sexp->pointer lst) index))) (if (null-pointer? result) #f (pointer->canonical-sexp result)))))) (define (dereference-size_t p) "Return the size_t value pointed to by P." (bytevector-uint-ref (pointer->bytevector p (sizeof size_t)) 0 (native-endianness) (sizeof size_t))) (define canonical-sexp-length (let* ((ptr (libgcrypt-func "gcry_sexp_length")) (proc (pointer->procedure int ptr '(*)))) (lambda (sexp) "Return the length of SEXP if it's a list (including the empty list); return zero if SEXP is an atom." (proc (canonical-sexp->pointer sexp))))) (define token-string? (let ((token-cs (char-set-union char-set:digit char-set:letter (char-set #\- #\. #\/ #\_ #\: #\* #\+ #\=)))) (lambda (str) "Return #t if STR is a token as per Section 4.3 of ." (and (not (string-null? str)) (string-every token-cs str) (not (char-set-contains? char-set:digit (string-ref str 0))))))) (define canonical-sexp-nth-data (let* ((ptr (libgcrypt-func "gcry_sexp_nth_data")) (proc (pointer->procedure '* ptr `(* ,int *)))) (lambda (lst index) "Return as a symbol (for \"sexp tokens\") or a bytevector (for any other \"octet string\") the INDEXth data element (atom) of LST, an s-expression. Return #f if that element does not exist, or if it's a list." (let* ((size* (bytevector->pointer (make-bytevector (sizeof '*)))) (result (proc (canonical-sexp->pointer lst) index size*))) (if (null-pointer? result) #f (let* ((len (dereference-size_t size*)) (str (pointer->string result len "ISO-8859-1"))) ;; The sexp spec speaks of "tokens" and "octet strings". ;; Sometimes these octet strings are actual strings (text), ;; sometimes they're bytevectors, and sometimes they're ;; multi-precision integers (MPIs). Only the application knows. ;; However, for convenience, we return a symbol when a token is ;; encountered since tokens are frequent (at least in the 'car' ;; of each sexp.) (if (token-string? str) (string->symbol str) ; an sexp "token" (bytevector-copy ; application data, textual or binary (pointer->bytevector result len))))))))) (define (number->canonical-sexp number) "Return an s-expression representing NUMBER." (string->canonical-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->canonical-sexp (format #f "(data (flags pkcs1) (hash \"~a\" #~a#))" hash-algo (bytevector->base16-string bv)))) (define (hash-data->bytevector data) "Return two values: the hash value (a bytevector), and the hash algorithm (a string) extracted from DATA, an sexp as returned by 'bytevector->hash-data'. Return #f if DATA does not conform." (let ((hash (find-sexp-token data 'hash))) (if hash (let ((algo (canonical-sexp-nth-data hash 1)) (value (canonical-sexp-nth-data hash 2))) (values value (symbol->string algo))) (values #f #f)))) (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 (canonical-sexp->pointer data) (canonical-sexp->pointer secret-key)))) (if (= 0 err) (pointer->canonical-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 (canonical-sexp->pointer signature) (canonical-sexp->pointer data) (canonical-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 (canonical-sexp->pointer params)))) (if (zero? err) (pointer->canonical-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 (canonical-sexp->pointer sexp) token 0))) (if (null-pointer? res) #f (pointer->canonical-sexp res)))))) (define-inlinable (canonical-sexp-null? sexp) "Return #t if SEXP is the empty-list sexp." (null-pointer? (canonical-sexp->pointer sexp))) (define (canonical-sexp-list? sexp) "Return #t if SEXP is a list." (or (canonical-sexp-null? sexp) (> (canonical-sexp-length sexp) 0))) ;;; pk-crypto.scm ends here