From: Damien Neil <dneil@google.com>
Date: Tue, 14 May 2024 21:39:10 +0000 (-0700)
Subject: archive/zip: treat truncated EOCDR comment as an error
X-Git-Tag: go1.23rc1~315
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=33d725e5758bf1fea62e6c77fc70b57a828a49f5;p=gostls13.git

archive/zip: treat truncated EOCDR comment as an error

When scanning for an end of central directory record,
treat an EOCDR signature with a record containing a truncated
comment as an error. Previously, we would skip over the invalid
record and look for another one. Other implementations do not
do this (they either consider this a hard error, or just ignore
the truncated comment). This parser misalignment allowed
presenting entirely different archive contents to Go programs
and other zip decoders.

Fixes #66869

Change-Id: I94e5cb028534bb5704588b8af27f1e22ea49c7c6
Reviewed-on: https://go-review.googlesource.com/c/go/+/585397
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---

diff --git a/src/archive/zip/reader.go b/src/archive/zip/reader.go
index ff6fedf632..60b34b76ee 100644
--- a/src/archive/zip/reader.go
+++ b/src/archive/zip/reader.go
@@ -699,9 +699,13 @@ func findSignatureInBlock(b []byte) int {
 		if b[i] == 'P' && b[i+1] == 'K' && b[i+2] == 0x05 && b[i+3] == 0x06 {
 			// n is length of comment
 			n := int(b[i+directoryEndLen-2]) | int(b[i+directoryEndLen-1])<<8
-			if n+directoryEndLen+i <= len(b) {
-				return i
+			if n+directoryEndLen+i > len(b) {
+				// Truncated comment.
+				// Some parsers (such as Info-ZIP) ignore the truncated comment
+				// rather than treating it as a hard error.
+				return -1
 			}
+			return i
 		}
 	}
 	return -1
diff --git a/src/archive/zip/reader_test.go b/src/archive/zip/reader_test.go
index 9f651da530..00e5ec3e05 100644
--- a/src/archive/zip/reader_test.go
+++ b/src/archive/zip/reader_test.go
@@ -570,6 +570,14 @@ var tests = []ZipTest{
 			},
 		},
 	},
+	// Issue 66869: Don't skip over an EOCDR with a truncated comment.
+	// The test file sneakily hides a second EOCDR before the first one;
+	// previously we would extract one file ("file") from this archive,
+	// while most other tools would reject the file or extract a different one ("FILE").
+	{
+		Name:  "comment-truncated.zip",
+		Error: ErrFormat,
+	},
 }
 
 func TestReader(t *testing.T) {
diff --git a/src/archive/zip/testdata/comment-truncated.zip b/src/archive/zip/testdata/comment-truncated.zip
new file mode 100644
index 0000000000..1bc19a8557
Binary files /dev/null and b/src/archive/zip/testdata/comment-truncated.zip differ