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Bump maximum header size to 4096 bytes #144

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3bbb3b4
Bump maximum header size to 4096 bytes
emersion Feb 3, 2026
1f6ba25
Add test for v2 header with TLV too large
emersion Feb 3, 2026
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5 changes: 3 additions & 2 deletions protocol.go
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Original file line number Diff line number Diff line change
Expand Up @@ -155,8 +155,9 @@ func (p *Listener) Addr() net.Addr {
func NewConn(conn net.Conn, opts ...func(*Conn)) *Conn {
// For v1 the header length is at most 108 bytes.
// For v2 the header length is at most 52 bytes plus the length of the TLVs.
// We use 256 bytes to be safe.
const bufSize = 256
// PP2_SUBTYPE_SSL_CLIENT_CERT might be a few kilobytes. We use 4096 bytes
// to be safe.
const bufSize = 4096
br := bufio.NewReaderSize(conn, bufSize)

pConn := &Conn{
Expand Down
20 changes: 16 additions & 4 deletions v2_test.go
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Expand Up @@ -15,7 +15,8 @@ var (
invalidRune = byte('\x99')

// Lengths to use in tests.
lengthPadded = uint16(84)
lengthPadded = uint16(84)
lengthTLVsTooLarge = uint16(10 * 1024)

lengthEmptyBytes = func() []byte {
a := make([]byte, 2)
Expand All @@ -27,6 +28,11 @@ var (
binary.BigEndian.PutUint16(a, lengthPadded)
return a
}()
lengthTLVsTooLargeBytes = func() []byte {
a := make([]byte, 2)
binary.BigEndian.PutUint16(a, lengthTLVsTooLarge)
return a
}()

// If life gives you lemons, make mojitos.
portBytes = func() []byte {
Expand Down Expand Up @@ -60,9 +66,10 @@ var (
_, _ = iorand.Read(tlv)
return tlv
}()
fixtureIPv4V2TLV = fixtureWithTLV(lengthV4Bytes, fixtureIPv4Address, fixtureTLV)
fixtureIPv6V2TLV = fixtureWithTLV(lengthV6Bytes, fixtureIPv6Address, fixtureTLV)
fixtureUnspecTLV = fixtureWithTLV(lengthUnspecBytes, []byte{}, fixtureTLV)
fixtureIPv4V2TLV = fixtureWithTLV(lengthV4Bytes, fixtureIPv4Address, fixtureTLV)
fixtureIPv6V2TLV = fixtureWithTLV(lengthV6Bytes, fixtureIPv6Address, fixtureTLV)
fixtureUnspecTLV = fixtureWithTLV(lengthUnspecBytes, []byte{}, fixtureTLV)
fixtureTLVsTooLarge = append(append(lengthTLVsTooLargeBytes, fixtureIPv4Address...), make([]byte, lengthTLVsTooLarge-lengthV4)...)

// Arbitrary bytes following proxy bytes.
arbitraryTailBytes = []byte{'\x99', '\x97', '\x98'}
Expand Down Expand Up @@ -153,6 +160,11 @@ var invalidParseV2Tests = []struct {
reader: newBufioReader(append(append(SIGV2, byte(LOCAL), byte(UNSPEC)), fixtureUnspecTLV[:2]...)),
expectedError: ErrInvalidLength,
},
{
desc: "TCPv4 with length too large",
reader: newBufioReader(append(append(SIGV2, byte(PROXY), byte(TCPv4)), fixtureTLVsTooLarge...)),
expectedError: ErrInvalidLength,
},
}

func TestParseV2Invalid(t *testing.T) {
Expand Down
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