[Reproducible-commits] [strip-nondeterminism] 01/01: png: gracefully handle nonconformant PNG files with trailing garbage

[Andrew Ayer]

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agwa-guest pushed a commit to branch master
in repository strip-nondeterminism.

commit 94c17377f15cc3191768b34b898aefc6c6977fb9
Author: Andrew Ayer <agwa at andrewayer.name>
Date:   Sat Oct 17 19:25:59 2015 -0700

    png: gracefully handle nonconformant PNG files with trailing garbage
    
    Closes: #802057
---
 lib/File/StripNondeterminism/handlers/png.pm | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/lib/File/StripNondeterminism/handlers/png.pm b/lib/File/StripNondeterminism/handlers/png.pm
index f0f806e..4b92047 100644
--- a/lib/File/StripNondeterminism/handlers/png.pm
+++ b/lib/File/StripNondeterminism/handlers/png.pm
@@ -72,9 +72,24 @@ sub normalize {
 							gmtime($canonical_time))) if defined($canonical_time);
 		} else {
 			print $tempfile $header . $data;
+
+			last if $type eq 'IEND'; # Stop processing immediately, in case
+						 # there's garbage after the PNG datastream.
+						 # (see https://bugs.debian.org/802057)
 		}
 	}
 
+	# Copy through trailing garbage.  Conformant PNG files don't have trailing
+	# garbage (see http://www.w3.org/TR/PNG/#15FileConformance item c), however
+	# in the interest of strip-nondeterminism being as transparent as possible,
+	# we preserve the garbage.
+	my $bytes_read;
+	my $buf;
+	while ($bytes_read = read($fh, $buf, 4096)) {
+		print $tempfile $buf;
+	}
+	defined($bytes_read) or die "$filename: read failed: $!";
+
 	chmod((stat($fh))[2] & 07777, $tempfile->filename);
 	rename($tempfile->filename, $filename)
 		or die "$filename: unable to overwrite: rename: $!";

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