From 4459c7859c286ab54fa3a9901c8a17591b04c516 Mon Sep 17 00:00:00 2001 From: Ludovic Courtès Date: Sat, 25 Apr 2020 23:23:51 +0200 Subject: openpgp: Decode the issuer-fingerprint signature subpacket. * guix/openpgp.scm (SUBPACKET-ISSUER-FINGERPRINT): New variable. (openpgp-signature-issuer-fingerprint): New procedure. (key-id-matches-fingerprint?): New procedure. (get-signature): Look for the 'issuer and 'issuer-fingerprint subpackets. Ensure the issuer key ID matches the fingerprint when both are available. (parse-subpackets): Handle SUBPACKET-ISSUER-FINGERPRINT. * tests/openpgp.scm (%rsa-key-fingerprint) (%dsa-key-fingerprint, %ed25519-key-fingerprint): New variables. * tests/openpgp.scm ("get-openpgp-detached-signature/ascii"): Check the result of 'openpgp-signature-issuer-fingerprint'. --- guix/openpgp.scm | 44 +++++++++++++++++++++++++++++++++++++++----- tests/openpgp.scm | 22 +++++++++++++++++----- 2 files changed, 56 insertions(+), 10 deletions(-) diff --git a/guix/openpgp.scm b/guix/openpgp.scm index bfdbe4b61b..77a75373df 100644 --- a/guix/openpgp.scm +++ b/guix/openpgp.scm @@ -33,6 +33,7 @@ openpgp-signature? openpgp-signature-issuer + openpgp-signature-issuer-fingerprint openpgp-signature-public-key-algorithm openpgp-signature-hash-algorithm openpgp-signature-creation-time @@ -345,7 +346,6 @@ hexadecimal format for fingerprints." ;; 12 = Revocation Key (define SUBPACKET-ISSUER 16) -;; TODO: hashed SUBPACKET-ISSUER-FINGERPRINT-V4 (define SUBPACKET-NOTATION-DATA 20) (define SUBPACKET-PREFERRED-HASH-ALGORITHMS 21) (define SUBPACKET-PREFERRED-COMPRESSION-ALGORITHMS 22) @@ -358,8 +358,8 @@ hexadecimal format for fingerprints." (define SUBPACKET-REASON-FOR-REVOCATION 29) (define SUBPACKET-FEATURES 30) ;; 31 = Signature Target - (define SUBPACKET-EMBEDDED-SIGNATURE 32) +(define SUBPACKET-ISSUER-FINGERPRINT 33) ;defined in RFC4880bis (define SIGNATURE-BINARY #x00) (define SIGNATURE-TEXT #x01) @@ -486,6 +486,13 @@ hexadecimal format for fingerprints." ;; XXX: is the issuer always in the unhashed subpackets? (else #f))) +(define (openpgp-signature-issuer-fingerprint sig) + "When it's available, return the fingerprint, a bytevector, or the issuer of +SIG. Otherwise, return #f." + (or (assoc-ref (openpgp-signature-hashed-subpackets sig) 'issuer-fingerprint) + (assoc-ref (openpgp-signature-unhashed-subpackets sig) + 'issuer-fingerprint))) + (define (openpgp-signature-creation-time sig) (cond ((assq 'signature-ctime (openpgp-signature-hashed-subpackets sig)) => (lambda (x) (unixtime (cdr x)))) @@ -578,6 +585,14 @@ the issuer's OpenPGP public key extracted from KEYRING." (values 'missing-key issuer)))) (values 'unsupported-signature sig))) +(define (key-id-matches-fingerprint? key-id fingerprint) + "Return true if KEY-ID, a number, corresponds to the low 8 bytes of +FINGERPRINT, a bytevector." + (let* ((len (bytevector-length fingerprint)) + (low (make-bytevector 8))) + (bytevector-copy! fingerprint (- len 8) low 0 8) + (= (bytevector->uint low) key-id))) + (define (get-signature p) (define (->hex n) (string-hex-pad (number->string n 16))) @@ -662,14 +677,26 @@ the issuer's OpenPGP public key extracted from KEYRING." ;; Errata ID: 2214. (integers->bytevector u8 #x04 u8 #xff - u32 (+ 6 subpacket-len))))) + u32 (+ 6 subpacket-len)))) + (unhashed-subpackets + (parse-subpackets unhashed-subpackets)) + (hashed-subpackets (parse-subpackets hashed-subpackets)) + (subpackets (append hashed-subpackets + unhashed-subpackets)) + (issuer-key-id (assoc-ref subpackets 'issuer)) + (issuer (assoc-ref subpackets + 'issuer-fingerprint))) + (unless (or (not issuer) (not issuer-key-id) + (key-id-matches-fingerprint? issuer-key-id issuer)) + (error "issuer key id does not match fingerprint" issuer)) + (make-openpgp-signature version type (public-key-algorithm pkalg) (openpgp-hash-algorithm halg) hashl16 append-data - (parse-subpackets hashed-subpackets) - (parse-subpackets unhashed-subpackets) + hashed-subpackets + unhashed-subpackets value))))) (else (print "Unsupported signature version: " version) @@ -701,6 +728,13 @@ the issuer's OpenPGP public key extracted from KEYRING." ((= type SUBPACKET-ISSUER) (cons 'issuer (bytevector-u64-ref data 0 (endianness big)))) + ((= type SUBPACKET-ISSUER-FINGERPRINT) ;v4+ only, RFC4880bis + (cons 'issuer-fingerprint + (let* ((version (bytevector-u8-ref data 0)) + (len (match version (4 20) (5 32)) ) + (fingerprint (make-bytevector len))) + (bytevector-copy! data 1 fingerprint 0 len) + fingerprint))) ((= type SUBPACKET-NOTATION-DATA) (let ((p (open-bytevector-input-port data))) (let-values (((f1 nlen vlen) diff --git a/tests/openpgp.scm b/tests/openpgp.scm index 8a3c7bbeb7..20d65171fd 100644 --- a/tests/openpgp.scm +++ b/tests/openpgp.scm @@ -18,6 +18,7 @@ (define-module (tests-openpgp) #:use-module (guix openpgp) + #:use-module (gcrypt base16) #:use-module (gcrypt hash) #:use-module (gcrypt pk-crypto) #:use-module (ice-9 binary-ports) @@ -65,6 +66,16 @@ vBSFjNSiVHsuAA== (define %dsa-key-id #x587918047BE8BD2C) ;dsa.key (define %ed25519-key-id #x771F49CBFAAE072D) ;ed25519.key +(define %rsa-key-fingerprint + (base16-string->bytevector + (string-downcase "385F86CFC86B665A5C165E6BAE25DA2A70DEED59"))) +(define %dsa-key-fingerprint + (base16-string->bytevector + (string-downcase "2884A980422330A4F33DD97F587918047BE8BD2C"))) +(define %ed25519-key-fingerprint + (base16-string->bytevector + (string-downcase "44D31E21AF7138F9B632280A771F49CBFAAE072D"))) + ;;; The following are detached signatures created commands like: ;;; echo 'Hello!' | gpg -sba --digest-algo sha512 @@ -160,15 +171,16 @@ Pz7oopeN72xgggYUNT37ezqN3MeCqw0= "Ludovic Courtès ")))))) (test-equal "get-openpgp-detached-signature/ascii" - (list `(,%dsa-key-id dsa sha256) - `(,%rsa-key-id rsa sha256) - `(,%ed25519-key-id eddsa sha256) - `(,%ed25519-key-id eddsa sha512) - `(,%ed25519-key-id eddsa sha1)) + (list `(,%dsa-key-id ,%dsa-key-fingerprint dsa sha256) + `(,%rsa-key-id ,%rsa-key-fingerprint rsa sha256) + `(,%ed25519-key-id ,%ed25519-key-fingerprint eddsa sha256) + `(,%ed25519-key-id ,%ed25519-key-fingerprint eddsa sha512) + `(,%ed25519-key-id ,%ed25519-key-fingerprint eddsa sha1)) (map (lambda (str) (let ((signature (get-openpgp-detached-signature/ascii (open-input-string str)))) (list (openpgp-signature-issuer signature) + (openpgp-signature-issuer-fingerprint signature) (openpgp-signature-public-key-algorithm signature) (openpgp-signature-hash-algorithm signature)))) (list %hello-signature/dsa -- cgit 1.4.1