401 lines
16 KiB
Scheme
401 lines
16 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
|
||
;;; Copyright © 2013, 2014, 2015 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 utils)
|
||
#:select (bytevector->base16-string
|
||
base16-string->bytevector))
|
||
#:use-module (guix gcrypt)
|
||
|
||
#:use-module (system foreign)
|
||
#:use-module (rnrs bytevectors)
|
||
#:use-module (ice-9 match)
|
||
#:export (canonical-sexp?
|
||
error-source
|
||
error-string
|
||
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
|
||
key-type
|
||
sign
|
||
verify
|
||
generate-key
|
||
find-sexp-token
|
||
canonical-sexp->sexp
|
||
sexp->canonical-sexp)
|
||
#:re-export (gcrypt-version))
|
||
|
||
|
||
;;; 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 to map them to
|
||
;;; Scheme s-expressions because (1) Libgcrypt sexps may be stored in secure
|
||
;;; memory, and (2) the read syntax is different.
|
||
;;;
|
||
;;; A 'canonical-sexp->sexp' procedure is provided nevertheless, for use in
|
||
;;; cases where it is safe to move data out of Libgcrypt---e.g., when
|
||
;;; processing ACL entries, public keys, etc.
|
||
;;;
|
||
;;; Canonical sexps were defined by Rivest et al. in the IETF draft at
|
||
;;; <http://people.csail.mit.edu/rivest/Sexp.txt> for the purposes of SPKI
|
||
;;; (see <http://www.ietf.org/rfc/rfc2693.txt>.)
|
||
;;;
|
||
;;; Code:
|
||
|
||
;; Libgcrypt "s-expressions".
|
||
(define-wrapped-pointer-type <canonical-sexp>
|
||
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 "#<canonical-sexp ~a | ~a>"
|
||
(number->string (object-address obj) 16)
|
||
(number->string (pointer-address (canonical-sexp->pointer obj))
|
||
16))))
|
||
|
||
(define finalize-canonical-sexp!
|
||
(libgcrypt-func "gcry_sexp_release"))
|
||
|
||
(define-inlinable (pointer->canonical-sexp ptr)
|
||
"Return a <canonical-sexp> that wraps PTR."
|
||
(let* ((sexp (naked-pointer->canonical-sexp ptr))
|
||
(ptr* (canonical-sexp->pointer sexp)))
|
||
;; Did we already have a <canonical-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-canonical-sexp!))
|
||
sexp))
|
||
|
||
(define error-source
|
||
(let* ((ptr (libgcrypt-func "gcry_strsource"))
|
||
(proc (pointer->procedure '* ptr (list int))))
|
||
(lambda (err)
|
||
"Return the error source (a string) for ERR, an error code as thrown
|
||
along with 'gcry-error'."
|
||
(pointer->string (proc err)))))
|
||
|
||
(define error-string
|
||
(let* ((ptr (libgcrypt-func "gcry_strerror"))
|
||
(proc (pointer->procedure '* ptr (list int))))
|
||
(lambda (err)
|
||
"Return the error description (a string) for ERR, an error code as
|
||
thrown along with 'gcry-error'."
|
||
(pointer->string (proc err)))))
|
||
|
||
(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."
|
||
|
||
;; When STR comes from 'canonical-sexp->string', it may contain
|
||
;; characters that are really meant to be interpreted as bytes as in a C
|
||
;; 'char *'. Thus, convert STR to ISO-8859-1 so the byte values of the
|
||
;; characters are preserved.
|
||
(let* ((sexp (bytevector->pointer (make-bytevector (sizeof '*))))
|
||
(err (proc sexp (string->pointer str "ISO-8859-1") 0 1)))
|
||
(if (= 0 err)
|
||
(pointer->canonical-sexp (dereference-pointer sexp))
|
||
(throw 'gcry-error 'string->canonical-sexp 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
|
||
<http://people.csail.mit.edu/rivest/Sexp.txt>."
|
||
(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")
|
||
#:key (key-type 'ecc))
|
||
"Given BV, a bytevector containing a hash of type HASH-ALGO, return an
|
||
s-expression suitable for use as the 'data' argument for 'sign'. KEY-TYPE
|
||
must be a symbol: 'dsa, 'ecc, or 'rsa."
|
||
(string->canonical-sexp
|
||
(format #f "(data (flags ~a) (hash \"~a\" #~a#))"
|
||
(case key-type
|
||
((ecc dsa) "rfc6979")
|
||
((rsa) "pkcs1")
|
||
(else (error "unknown key type" key-type)))
|
||
hash-algo
|
||
(bytevector->base16-string bv))))
|
||
|
||
(define (key-type sexp)
|
||
"Return a symbol denoting the type of public or private key represented by
|
||
SEXP--e.g., 'rsa', 'ecc'--or #f if SEXP does not denote a valid key."
|
||
(case (canonical-sexp-nth-data sexp 0)
|
||
((public-key private-key)
|
||
(canonical-sexp-nth-data (canonical-sexp-nth sexp 1) 0))
|
||
(else #f)))
|
||
|
||
(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, a canonical s-expression representing a suitable hash, with
|
||
SECRET-KEY (a canonical s-expression whose car is 'private-key'.) Note that
|
||
DATA must be a 'data' s-expression, as returned by
|
||
'bytevector->hash-data' (info \"(gcrypt) Cryptographic Functions\")."
|
||
(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 'gcry-error 'sign 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 'generate-key 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)))
|
||
|
||
(define (canonical-sexp-fold proc seed sexp)
|
||
"Fold PROC (as per SRFI-1) over SEXP, a canonical sexp."
|
||
(if (canonical-sexp-list? sexp)
|
||
(let ((len (canonical-sexp-length sexp)))
|
||
(let loop ((index 0)
|
||
(result seed))
|
||
(if (= index len)
|
||
result
|
||
(loop (+ 1 index)
|
||
;; XXX: Call 'nth-data' *before* 'nth' to work around
|
||
;; <https://bugs.g10code.com/gnupg/issue1594>, which
|
||
;; affects 1.6.0 and earlier versions.
|
||
(proc (or (canonical-sexp-nth-data sexp index)
|
||
(canonical-sexp-nth sexp index))
|
||
result)))))
|
||
(error "sexp is not a list" sexp)))
|
||
|
||
(define (canonical-sexp->sexp sexp)
|
||
"Return a Scheme sexp corresponding to SEXP. This is particularly useful to
|
||
compare sexps (since Libgcrypt does not provide an 'equal?' procedure), or to
|
||
use pattern matching."
|
||
(if (canonical-sexp-list? sexp)
|
||
(reverse
|
||
(canonical-sexp-fold (lambda (item result)
|
||
(cons (if (canonical-sexp? item)
|
||
(canonical-sexp->sexp item)
|
||
item)
|
||
result))
|
||
'()
|
||
sexp))
|
||
|
||
;; As of Libgcrypt 1.6.0, there's no function to extract the buffer of a
|
||
;; non-list sexp (!), so we first enlist SEXP, then get at its buffer.
|
||
(let ((sexp (string->canonical-sexp
|
||
(string-append "(" (canonical-sexp->string sexp)
|
||
")"))))
|
||
(or (canonical-sexp-nth-data sexp 0)
|
||
(canonical-sexp-nth sexp 0)))))
|
||
|
||
(define (sexp->canonical-sexp sexp)
|
||
"Return a canonical sexp equivalent to SEXP, a Scheme sexp as returned by
|
||
'canonical-sexp->sexp'."
|
||
;; XXX: This is inefficient, but the Libgcrypt API doesn't allow us to do
|
||
;; much better.
|
||
(string->canonical-sexp
|
||
(call-with-output-string
|
||
(lambda (port)
|
||
(define (write item)
|
||
(cond ((list? item)
|
||
(display "(" port)
|
||
(for-each write item)
|
||
(display ")" port))
|
||
((symbol? item)
|
||
(format port " ~a" item))
|
||
((bytevector? item)
|
||
(format port " #~a#"
|
||
(bytevector->base16-string item)))
|
||
(else
|
||
(error "unsupported sexp item type" item))))
|
||
|
||
(write sexp)))))
|
||
|
||
(define (gcrypt-error-printer port key args default-printer)
|
||
"Print the gcrypt error specified by ARGS."
|
||
(match args
|
||
((proc err)
|
||
(format port "In procedure ~a: ~a: ~a"
|
||
proc (error-source err) (error-string err)))))
|
||
|
||
(set-exception-printer! 'gcry-error gcrypt-error-printer)
|
||
|
||
;;; pk-crypto.scm ends here
|