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Use 'signature-case' in (guix nar) and 'substitute-binary'.

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* guix/nar.scm (restore-file-set)[assert-valid-signature]: Rewrite in
  terms of 'signature-case'.
* guix/scripts/substitute-binary.scm (narinfo-signature->canonical-sexp):
  Call 'leave' instead of 'raise' when SIGNATURE is invalid.
  (&nar-signature-error, &nar-invalid-hash-error): Remove.
  (assert-valid-signature): Add 'narinfo' parameter; remove 'port'.
  Rewrite in terms of 'signature-case' and 'leave'.  Mention NARINFO's
  URI in error messages.  Adjust caller.
  (narinfo-sha256): New procedure.
  (assert-valid-narinfo): Use it.
  (valid-narinfo?): Rewrite using 'narinfo-sha256' and
  'signature-case'.
* tests/substitute-binary.scm (assert-valid-signature,
  test-error-condition): Remove.
  ("corrupt signature data", "unauthorized public key", "invalid
  signature"): Remove.
This commit is contained in:
Ludovic Courtès 2014-03-31 23:47:02 +02:00
parent 81deef270d
commit e4687a5e68
3 changed files with 75 additions and 131 deletions
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21
guix/nar.scm
View file

@ -372,7 +372,7 @@ (define (assert-valid-signature signature hash file)
;; Bail out if SIGNATURE, which must be a string as produced by
;; 'canonical-sexp->string', doesn't match HASH, a bytevector containing
;; the expected hash for FILE.
(let* ((signature (catch 'gcry-error
(let ((signature (catch 'gcry-error
(lambda ()
(string->canonical-sexp signature))
(lambda (err . _)
@ -382,30 +382,31 @@ (define (assert-valid-signature signature hash file)
s-expression"))
(&nar-signature-error
(file file)
(signature signature) (port port)))))))
(subject (signature-subject signature))
(data (signature-signed-data signature)))
(if (and data subject)
(if (authorized-key? subject)
(if (equal? (hash-data->bytevector data) hash)
(unless (valid-signature? signature)
(signature signature) (port port))))))))
(signature-case (signature hash (current-acl))
(valid-signature #t)
(invalid-signature
(raise (condition
(&message (message "invalid signature"))
(&nar-signature-error
(file file) (signature signature) (port port)))))
(hash-mismatch
(raise (condition (&message (message "invalid hash"))
(&nar-invalid-hash-error
(port port) (file file)
(signature signature)
(expected (hash-data->bytevector data))
(expected (hash-data->bytevector
(signature-signed-data signature)))
(actual hash)))))
(unauthorized-key
(raise (condition (&message (message "unauthorized public key"))
(&nar-signature-error
(signature signature) (file file) (port port)))))
(corrupt-signature
(raise (condition
(&message (message "corrupt signature data"))
(&nar-signature-error
(signature signature) (file file) (port port)))))))
(signature signature) (file file) (port port))))))))
(let loop ((n (read-long-long port))
(files '()))

98
guix/scripts/substitute-binary.scm
View file

@ -252,14 +252,10 @@ (define (narinfo-signature->canonical-sexp str)
(catch 'gcry-error
(lambda ()
(string->canonical-sexp signature))
(lambda (err . _)
(raise (condition
(&message
(message "signature is not a valid \
s-expression"))
(&nar-signature-error
(file #f)
(signature signature) (port #f)))))))))))
(lambda (err . rest)
(leave (_ "signature is not a valid \
s-expression: ~s~%")
signature))))))))
(x
(leave (_ "invalid format of the signature field: ~a~%") x))))
@ -288,43 +284,21 @@ (define (narinfo-maker str cache-url)
(and=> signature narinfo-signature->canonical-sexp))
str)))
(define &nar-signature-error (@@ (guix nar) &nar-signature-error))
(define &nar-invalid-hash-error (@@ (guix nar) &nar-invalid-hash-error))
;;; XXX: The following function is nearly an exact copy of the one from
;;; 'guix/nar.scm'. Factorize as soon as we know how to make the latter
;;; public (see <https://lists.gnu.org/archive/html/guix-devel/2014-03/msg00097.html>).
;;; Keep this one private to avoid confusion.
(define* (assert-valid-signature signature hash port
(define* (assert-valid-signature narinfo signature hash
#:optional (acl (current-acl)))
"Bail out if SIGNATURE, a canonical sexp, doesn't match HASH, a bytevector
containing the expected hash for FILE."
(let* (;; XXX: This is just to keep the errors happy; get a sensible
;; file name.
(file #f)
(subject (signature-subject signature))
(data (signature-signed-data signature)))
(if (and data subject)
(if (authorized-key? subject acl)
(if (equal? (hash-data->bytevector data) hash)
(unless (valid-signature? signature)
(raise (condition
(&message (message "invalid signature"))
(&nar-signature-error
(file file) (signature signature) (port port)))))
(raise (condition (&message (message "invalid hash"))
(&nar-invalid-hash-error
(port port) (file file)
(signature signature)
(expected (hash-data->bytevector data))
(actual hash)))))
(raise (condition (&message (message "unauthorized public key"))
(&nar-signature-error
(signature signature) (file file) (port port)))))
(raise (condition
(&message (message "corrupt signature data"))
(&nar-signature-error
(signature signature) (file file) (port port)))))))
"Bail out if SIGNATURE, a canonical sexp representing the signature of
NARINFO, doesn't match HASH, a bytevector containing the hash of NARINFO."
(let ((uri (uri->string (narinfo-uri narinfo))))
(signature-case (signature hash acl)
(valid-signature #t)
(invalid-signature
(leave (_ "invalid signature for '~a'~%") uri))
(hash-mismatch
(leave (_ "hash mismatch for '~a'~%") uri))
(unauthorized-key
(leave (_ "'~a' is signed with an unauthorized key~%") uri))
(corrupt-signature
(leave (_ "signature on '~a' is corrupt~%") uri)))))
(define* (read-narinfo port #:optional url)
"Read a narinfo from PORT. If URL is true, it must be a string used to
@ -343,22 +317,29 @@ (define %signature-line-rx
;; Regexp matching a signature line in a narinfo.
(make-regexp "(.+)^[[:blank:]]*Signature:[[:blank:]].+$"))
(define (narinfo-sha256 narinfo)
"Return the sha256 hash of NARINFO as a bytevector, or #f if NARINFO lacks a
'Signature' field."
(let ((contents (narinfo-contents narinfo)))
(match (regexp-exec %signature-line-rx contents)
(#f #f)
((= (cut match:substring <> 1) above-signature)
(sha256 (string->utf8 above-signature))))))
(define* (assert-valid-narinfo narinfo
#:optional (acl (current-acl))
#:key (verbose? #t))
"Raise an exception if NARINFO lacks a signature, has an invalid signature,
or is signed by an unauthorized key."
(let* ((contents (narinfo-contents narinfo))
(res (regexp-exec %signature-line-rx contents)))
(if (not res)
(let ((hash (narinfo-sha256 narinfo)))
(if (not hash)
(if %allow-unauthenticated-substitutes?
narinfo
(leave (_ "narinfo lacks a signature: ~s~%")
contents))
(let ((hash (sha256 (string->utf8 (match:substring res 1))))
(signature (narinfo-signature narinfo)))
(leave (_ "narinfo for '~a' lacks a signature~%")
(uri->string (narinfo-uri narinfo))))
(let ((signature (narinfo-signature narinfo)))
(unless %allow-unauthenticated-substitutes?
(assert-valid-signature signature hash #f acl)
(assert-valid-signature narinfo signature hash acl)
(when verbose?
(format (current-error-port)
"found valid signature for '~a', from '~a'~%"
@ -366,12 +347,15 @@ (define* (assert-valid-narinfo narinfo
(uri->string (narinfo-uri narinfo)))))
narinfo))))
(define (valid-narinfo? narinfo)
(define* (valid-narinfo? narinfo #:optional (acl (current-acl)))
"Return #t if NARINFO's signature is not valid."
(false-if-exception
(begin
(assert-valid-narinfo narinfo #:verbose? #f)
#t)))
(or %allow-unauthenticated-substitutes?
(let ((hash (narinfo-sha256 narinfo))
(signature (narinfo-signature narinfo)))
(and hash signature
(signature-case (signature hash acl)
(valid-signature #t)
(else #f))))))
(define (write-narinfo narinfo port)
"Write NARINFO to PORT."

41
tests/substitute-binary.scm
View file

@ -38,13 +38,6 @@ (define-module (test-substitute-binary)
#:use-module (srfi srfi-35)
#:use-module ((srfi srfi-64) #:hide (test-error)))
(define assert-valid-signature
;; (guix scripts substitute-binary) does not export this function in order to
;; avoid misuse.
(@@ (guix scripts substitute-binary) assert-valid-signature))
;;; XXX: Replace with 'test-error' from SRFI-64 as soon as it allow us to
;;; catch specific exceptions.
(define-syntax-rule (test-quit name error-rx exp)
"Emit a test that passes when EXP throws to 'quit' with value 1, and when
it writes to GUIX-WARNING-PORT a messages that matches ERROR-RX."
@ -117,39 +110,6 @@ (define* (signature-field bv-or-str
(test-assert "valid narinfo-signature->canonical-sexp"
(canonical-sexp? (narinfo-signature->canonical-sexp (signature-field "foo"))))
(define-syntax-rule (test-error-condition name pred message-rx exp)
(test-assert name
(guard (condition ((pred condition)
(and (string-match message-rx
(condition-message condition))
#t))
(else #f))
exp
#f)))
(test-error-condition "corrupt signature data"
nar-signature-error? "corrupt"
(assert-valid-signature (string->canonical-sexp "(foo bar baz)") "irrelevant"
(open-input-string "irrelevant")
(public-keys->acl (list %public-key))))
(test-error-condition "unauthorized public key"
nar-signature-error? "unauthorized"
(assert-valid-signature (narinfo-signature->canonical-sexp
(signature-field "foo"))
"irrelevant"
(open-input-string "irrelevant")
(public-keys->acl '())))
(test-error-condition "invalid signature"
nar-signature-error? "invalid signature"
(let ((message "this is the message that we sign"))
(assert-valid-signature (narinfo-signature->canonical-sexp
(signature-field message
#:public-key %wrong-public-key))
(sha256 (string->utf8 message))
(open-input-string "irrelevant")
(public-keys->acl (list %wrong-public-key)))))
(define %narinfo
@ -317,6 +277,5 @@ (define-syntax-rule (with-narinfo narinfo body ...)
;;; Local Variables:
;;; eval: (put 'with-narinfo 'scheme-indent-function 1)
;;; eval: (put 'test-error-condition 'scheme-indent-function 3)
;;; eval: (put 'test-quit 'scheme-indent-function 2)
;;; End: