From a65f4ccb8994c1e6cfd8031012957a85e943b9b1 Mon Sep 17 00:00:00 2001
From: Benny Siegert <bsiegert@gmail.com>
Date: Thu, 28 Jul 2011 11:15:59 +1000
Subject: [PATCH] image/tiff: Do not panic when RowsPerStrip is missing.

The RowsPerStrip tag is mandatory according to the spec. However,
Mac OS sometimes (?) omits it. I managed to create such an image
by applying "tiffutil -none" on a compressed image.

If RowsPerStrip is 0, there was a division by zero in the decoder.
Assume that the image is a single strip in this case.

R=nigeltao, bradfitz
CC=golang-dev
https://golang.org/cl/4815061
---
 src/pkg/image/tiff/reader.go            |   4 ++++
 src/pkg/image/tiff/reader_test.go       |  25 ++++++++++++++++++++++++
 src/pkg/image/tiff/testdata/no_rps.tiff | Bin 0 -> 1294 bytes
 3 files changed, 29 insertions(+)
 create mode 100644 src/pkg/image/tiff/reader_test.go
 create mode 100644 src/pkg/image/tiff/testdata/no_rps.tiff

diff --git a/src/pkg/image/tiff/reader.go b/src/pkg/image/tiff/reader.go
index 26e52144d4..f5652667aa 100644
--- a/src/pkg/image/tiff/reader.go
+++ b/src/pkg/image/tiff/reader.go
@@ -362,6 +362,10 @@ func Decode(r io.Reader) (img image.Image, err os.Error) {
 
 	// Check if we have the right number of strips, offsets and counts.
 	rps := int(d.firstVal(tRowsPerStrip))
+	if rps == 0 {
+		// Assume only one strip.
+		rps = d.config.Height
+	}
 	numStrips := (d.config.Height + rps - 1) / rps
 	if rps == 0 || len(d.features[tStripOffsets]) < numStrips || len(d.features[tStripByteCounts]) < numStrips {
 		return nil, FormatError("inconsistent header")
diff --git a/src/pkg/image/tiff/reader_test.go b/src/pkg/image/tiff/reader_test.go
new file mode 100644
index 0000000000..f2122c4403
--- /dev/null
+++ b/src/pkg/image/tiff/reader_test.go
@@ -0,0 +1,25 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tiff
+
+import (
+	"os"
+	"testing"
+)
+
+// TestNoRPS tries to decode an image that has no RowsPerStrip tag.
+// The tag is mandatory according to the spec but some software omits
+// it in the case of a single strip.
+func TestNoRPS(t *testing.T) {
+	f, err := os.Open("testdata/no_rps.tiff")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	_, err = Decode(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/src/pkg/image/tiff/testdata/no_rps.tiff b/src/pkg/image/tiff/testdata/no_rps.tiff
new file mode 100644
index 0000000000000000000000000000000000000000..3280cf8e344b0ff0b6b98a1c3ca0029174eb82ef
GIT binary patch
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literal 0
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-- 
2.50.0