From d973bb107e9142cf17e4a7f2666a71ed2d457e91 Mon Sep 17 00:00:00 2001 From: Daniel Martí Date: Mon, 11 Oct 2021 11:12:38 +0100 Subject: encoding/gob: follow documented io.EOF semantics MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The docs say: If the input is at EOF, Decode returns io.EOF and does not modify e. However, the added test fails: --- FAIL: TestDecodePartial (0.00s) encoder_test.go:1263: 31/81: expected io.ErrUnexpectedEOF: EOF encoder_test.go:1263: 51/81: expected io.ErrUnexpectedEOF: EOF In particular, the decoder would return io.EOF after reading a valid message for a type specification, and then hit EOF before reading a data item message. Fix that by only allowing a Decode call to return io.EOF if the reader hits EOF immediately, without successfully reading any message. Otherwise, hitting EOF is an ErrUnexpectedEOF, like in other cases. Also fix a net/rpc test that, coincidentally, expected an io.EOF as an error when feeding bad non-zero data to a gob decoder. An io.ErrUnexpectedEOF is clearly better in that scenario. Fixes #48905. Change-Id: Ied6a0d8ac8377f89646319a18c0380c4f2b09b85 Reviewed-on: https://go-review.googlesource.com/c/go/+/354972 Trust: Daniel Martí Run-TryBot: Daniel Martí TryBot-Result: Go Bot Reviewed-by: Rob Pike --- src/encoding/gob/decoder.go | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'src/encoding/gob/decoder.go') diff --git a/src/encoding/gob/decoder.go b/src/encoding/gob/decoder.go index b476aaac93..5e4ed5a7d7 100644 --- a/src/encoding/gob/decoder.go +++ b/src/encoding/gob/decoder.go @@ -138,9 +138,17 @@ func (dec *Decoder) nextUint() uint64 { // decoded. If this is an interface value, it can be ignored by // resetting that buffer. func (dec *Decoder) decodeTypeSequence(isInterface bool) typeId { + firstMessage := true for dec.err == nil { if dec.buf.Len() == 0 { if !dec.recvMessage() { + // We can only return io.EOF if the input was empty. + // If we read one or more type spec messages, + // require a data item message to follow. + // If we hit an EOF before that, then give ErrUnexpectedEOF. + if !firstMessage && dec.err == io.EOF { + dec.err = io.ErrUnexpectedEOF + } break } } @@ -166,6 +174,7 @@ func (dec *Decoder) decodeTypeSequence(isInterface bool) typeId { } dec.nextUint() } + firstMessage = false } return -1 } -- cgit v1.3