plumbing: format: pktline, Accept oversized pkt-lines up to 65524 bytes
The canonical Git client successfully decodes sideband packets up to
65524 bytes in length (4-byte header + 65520-byte payload). The Git
protocol documentation was updated in August 2016 to reduce the maximum
payload size to 65516 bytes, however old implementations still exist in
the wild emitting 65520-byte payloads.
As there is no technical difficulty with accepting (not emitting) larger
payload sizes, this change adjusts the limit check to allow successful
decoding of packets up to 65524 bytes. This change increases
compatibility with the current canonical Git implementation.
Doc changes from August 2016:
https://github.com/git/git/commit/7841c4801ce51f1f62d376d164372e8677c6bc94#diff-52695c8fe91b78b70cea44562ae28297L67
Current packet buffer size is still LARGE_PACKET_MAX (+1 null):
https://github.com/git/git/blob/468165c1d8a442994a825f3684528361727cd8c0/sideband.c#L24
https://github.com/git/git/blob/468165c1d8a442994a825f3684528361727cd8c0/sideband.c#L36
LARGE_PACKET_MAX definition:
https://github.com/git/git/blob/468165c1d8a442994a825f3684528361727cd8c0/pkt-line.h#L100
Signed-off-by: Joseph Vusich <jvusich@amazon.com>
diff --git a/plumbing/format/pktline/encoder.go b/plumbing/format/pktline/encoder.go
index eae85cc..6d40979 100644
--- a/plumbing/format/pktline/encoder.go
+++ b/plumbing/format/pktline/encoder.go
@@ -17,6 +17,9 @@
const (
// MaxPayloadSize is the maximum payload size of a pkt-line in bytes.
MaxPayloadSize = 65516
+
+ // For compatibility with canonical Git implementation, accept longer pkt-lines
+ OversizePayloadMax = 65520
)
var (
diff --git a/plumbing/format/pktline/scanner.go b/plumbing/format/pktline/scanner.go
index 4af254f..99aab46 100644
--- a/plumbing/format/pktline/scanner.go
+++ b/plumbing/format/pktline/scanner.go
@@ -97,7 +97,7 @@
return 0, nil
case n <= lenSize:
return 0, ErrInvalidPktLen
- case n > MaxPayloadSize+lenSize:
+ case n > OversizePayloadMax+lenSize:
return 0, ErrInvalidPktLen
default:
return n - lenSize, nil
diff --git a/plumbing/format/pktline/scanner_test.go b/plumbing/format/pktline/scanner_test.go
index 048ea38..9660c2d 100644
--- a/plumbing/format/pktline/scanner_test.go
+++ b/plumbing/format/pktline/scanner_test.go
@@ -20,7 +20,7 @@
for _, test := range [...]string{
"0001", "0002", "0003", "0004",
"0001asdfsadf", "0004foo",
- "fff1", "fff2",
+ "fff5", "ffff",
"gorka",
"0", "003",
" 5a", "5 a", "5 \n",
@@ -34,6 +34,20 @@
}
}
+func (s *SuiteScanner) TestDecodeOversizePktLines(c *C) {
+ for _, test := range [...]string{
+ "fff1" + strings.Repeat("a", 0xfff1),
+ "fff2" + strings.Repeat("a", 0xfff2),
+ "fff3" + strings.Repeat("a", 0xfff3),
+ "fff4" + strings.Repeat("a", 0xfff4),
+ } {
+ r := strings.NewReader(test)
+ sc := pktline.NewScanner(r)
+ _ = sc.Scan()
+ c.Assert(sc.Err(), IsNil)
+ }
+}
+
func (s *SuiteScanner) TestEmptyReader(c *C) {
r := strings.NewReader("")
sc := pktline.NewScanner(r)
