From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Tue, 12 Nov 2013 21:08:12 +0000 (+0100)
Subject: die() if the wrong amount of randomness comes in.
X-Git-Url: https://git.sesse.net/?p=www-csrf;a=commitdiff_plain;h=80a40fdedd8dc58264dd6ef1c14d679cf2291add

die() if the wrong amount of randomness comes in.
---

diff --git a/lib/WWW/CSRF.pm b/lib/WWW/CSRF.pm
index 9197a6e..77d8e79 100644
--- a/lib/WWW/CSRF.pm
+++ b/lib/WWW/CSRF.pm
@@ -20,8 +20,10 @@ sub generate_csrf_token {
 	my @digest_bytes = _to_byte_array($digest);
 
 	# Mask the token to avoid the BREACH attack.
-	if (!defined($random) || length($random) != length($digest)) {
+	if (!defined($random)) {
 		$random = Bytes::Random::Secure::random_bytes(scalar @digest_bytes);
+	} elsif (length($random) != length($digest)) {
+		die "Given randomness is of the wrong length (should be " . length($digest) . " bytes)";
 	}
 	my @random_bytes = _to_byte_array($random);
 	
diff --git a/t/01_generate.t b/t/01_generate.t
index 3e97a6f..a2147de 100644
--- a/t/01_generate.t
+++ b/t/01_generate.t
@@ -1,4 +1,4 @@
-use Test::More tests => 5;
+use Test::More tests => 6;
 
 use WWW::CSRF qw(generate_csrf_token);
 
@@ -24,3 +24,9 @@ $random = pack('H*', '112233445566778899aabbccddeeff0011223340');
 is(generate_csrf_token("id", "secret", { Random => $random, Time => 1234567890 }),
    "5df5e9f17c929a45af5d33624ec052903599958b,112233445566778899aabbccddeeff0011223340,1234567890",
    "bitflip in mask flips corresponding bit in token");
+
+$random = pack('H*', '112233445566778899aabbccddeeff00112233');
+eval {
+  my $ignored = generate_csrf_token("id", "secret", { Random => $random, Time => 1234567890 });
+};
+ok($@, "check that wrong amount of randomness causes die()");