authenticate: Allow signatures with binary data to be written to stdout.

Fixes <http://bugs.gnu.org/17312>.

* guix/scripts/authenticate.scm (guix-authenticate): Add calls to
  'set-port-encoding!' and 'set-port-conversion-strategy!'.  Wrap body
  in 'with-fluids' form that sets '%default-port-encoding' and
  '%default-port-conversion-strategy'.
* tests/guix-authenticate.sh: Add test.
* tests/pk-crypto.scm ("hash corrupt due to restrictive locale
  encoding"): Add reference to bug.

guix/scripts/authenticate.scm

@@ -89,6 +89,15 @@ (define (validate-signature port)
 ;;;
 
 (define (guix-authenticate . args)
+  ;; Signature sexps written to stdout may contain binary data, so force
+  ;; ISO-8859-1 encoding so that things are not mangled.  See
+  ;; <http://bugs.gnu.org/17312> for details.
+  (set-port-encoding! (current-output-port) "ISO-8859-1")
+  (set-port-conversion-strategy! (current-output-port) 'error)
+
+  ;; Same goes for input ports.
+  (with-fluids ((%default-port-encoding "ISO-8859-1")
+                (%default-port-conversion-strategy 'error))
     (match args
       ;; As invoked by guix-daemon.
       (("rsautl" "-sign" "-inkey" key "-in" hash-file)
@@ -113,6 +122,6 @@ (define (guix-authenticate . args)
       (("--version")
        (show-version-and-exit "guix authenticate"))
       (else
-     (leave (_ "wrong arguments")))))
+       (leave (_ "wrong arguments"))))))
 
 ;;; authenticate.scm ends here

tests/guix-authenticate.sh

@@ -72,3 +72,24 @@ if guix authenticate rsautl -verify				\
 then false
 else true
 fi
+
+
+# Test for <http://bugs.gnu.org/17312>: make sure 'guix authenticate' produces
+# valid signatures when run in the C locale.
+echo "5eff0b55c9c5f5e87b4e34cd60a2d5654ca1eb78c7b3c67c3179fed1cff07b4c" \
+    > "$hash"
+
+LC_ALL=C
+export LC_ALL
+
+guix authenticate rsautl -sign				\
+    -inkey "$abs_top_srcdir/tests/signing-key.sec"	\
+    -in "$hash" > "$sig"
+
+guix authenticate rsautl -verify			\
+        -inkey "$abs_top_srcdir/tests/signing-key.pub"	\
+        -pubin -in "$sig"
+hash2="`guix authenticate rsautl -verify		\
+          -inkey $abs_top_srcdir/tests/signing-key.pub	\
+          -pubin -in $sig`"
+test "$hash2" = `cat "$hash"`

tests/pk-crypto.scm

@@ -153,7 +153,7 @@ (define %ecc-key-pair
     ;; In Guix up to 0.6 included this test would fail because at some point
     ;; the hash value would be cropped to ASCII.  In practice 'guix
     ;; authenticate' would produce invalid signatures that would fail
-    ;; signature verification.
+    ;; signature verification.  See <http://bugs.gnu.org/17312>.
     (let ((locale (setlocale LC_ALL)))
      (dynamic-wind
        (lambda ()