From 3636ced112d89da03739fa7d5468c0270addaa28 Mon Sep 17 00:00:00 2001 From: Joe Tsai Date: Thu, 24 Jul 2025 12:16:35 -0700 Subject: [PATCH] encoding/json: fix extra data regression under goexperiment.jsonv2 When operating under v1 semantics in the v2 implementation, a extra data error should take precedence over any semantic error that could theoretically occur within the value itself. This change only affects code compiled under goexperiment.jsonv2. Fixes #74614 Change-Id: I055a606b053fa66b0c766ae205487b8290109285 Reviewed-on: https://go-review.googlesource.com/c/go/+/689919 Reviewed-by: Damien Neil Reviewed-by: Michael Knyszek Auto-Submit: Michael Knyszek LUCI-TryBot-Result: Go LUCI --- src/encoding/json/jsontext/decode.go | 10 +++++++-- src/encoding/json/v2/arshal.go | 33 ++++++++++++++-------------- 2 files changed, 24 insertions(+), 19 deletions(-) diff --git a/src/encoding/json/jsontext/decode.go b/src/encoding/json/jsontext/decode.go index 44b436686f..b9f247bff4 100644 --- a/src/encoding/json/jsontext/decode.go +++ b/src/encoding/json/jsontext/decode.go @@ -776,7 +776,8 @@ func (d *decoderState) ReadValue(flags *jsonwire.ValueFlags) (Value, error) { // CheckNextValue checks whether the next value is syntactically valid, // but does not advance the read offset. -func (d *decoderState) CheckNextValue() error { +// If last, it verifies that the stream cleanly terminates with [io.EOF]. +func (d *decoderState) CheckNextValue(last bool) error { d.PeekKind() // populates d.peekPos and d.peekErr pos, err := d.peekPos, d.peekErr d.peekPos, d.peekErr = 0, nil @@ -787,13 +788,18 @@ func (d *decoderState) CheckNextValue() error { var flags jsonwire.ValueFlags if pos, err := d.consumeValue(&flags, pos, d.Tokens.Depth()); err != nil { return wrapSyntacticError(d, err, pos, +1) + } else if last { + return d.checkEOF(pos) } return nil } // CheckEOF verifies that the input has no more data. func (d *decoderState) CheckEOF() error { - switch pos, err := d.consumeWhitespace(d.prevEnd); err { + return d.checkEOF(d.prevEnd) +} +func (d *decoderState) checkEOF(pos int) error { + switch pos, err := d.consumeWhitespace(pos); err { case nil: err := jsonwire.NewInvalidCharacterError(d.buf[pos:], "after top-level value") return wrapSyntacticError(d, err, pos, 0) diff --git a/src/encoding/json/v2/arshal.go b/src/encoding/json/v2/arshal.go index 5cd2106be9..e2ce778d5a 100644 --- a/src/encoding/json/v2/arshal.go +++ b/src/encoding/json/v2/arshal.go @@ -409,7 +409,7 @@ func Unmarshal(in []byte, out any, opts ...Options) (err error) { dec := export.GetBufferedDecoder(in, opts...) defer export.PutBufferedDecoder(dec) xd := export.Decoder(dec) - err = unmarshalFull(dec, out, &xd.Struct) + err = unmarshalDecode(dec, out, &xd.Struct, true) if err != nil && xd.Flags.Get(jsonflags.ReportErrorsWithLegacySemantics) { return internal.TransformUnmarshalError(out, err) } @@ -426,25 +426,13 @@ func UnmarshalRead(in io.Reader, out any, opts ...Options) (err error) { dec := export.GetStreamingDecoder(in, opts...) defer export.PutStreamingDecoder(dec) xd := export.Decoder(dec) - err = unmarshalFull(dec, out, &xd.Struct) + err = unmarshalDecode(dec, out, &xd.Struct, true) if err != nil && xd.Flags.Get(jsonflags.ReportErrorsWithLegacySemantics) { return internal.TransformUnmarshalError(out, err) } return err } -func unmarshalFull(in *jsontext.Decoder, out any, uo *jsonopts.Struct) error { - switch err := unmarshalDecode(in, out, uo); err { - case nil: - return export.Decoder(in).CheckEOF() - case io.EOF: - offset := in.InputOffset() + int64(len(in.UnreadBuffer())) - return &jsontext.SyntacticError{ByteOffset: offset, Err: io.ErrUnexpectedEOF} - default: - return err - } -} - // UnmarshalDecode deserializes a Go value from a [jsontext.Decoder] according to // the provided unmarshal options (while ignoring marshal, encode, or decode options). // Any unmarshal options already specified on the [jsontext.Decoder] @@ -463,14 +451,14 @@ func UnmarshalDecode(in *jsontext.Decoder, out any, opts ...Options) (err error) defer func() { xd.Struct = optsOriginal }() xd.Struct.JoinWithoutCoderOptions(opts...) } - err = unmarshalDecode(in, out, &xd.Struct) + err = unmarshalDecode(in, out, &xd.Struct, false) if err != nil && xd.Flags.Get(jsonflags.ReportErrorsWithLegacySemantics) { return internal.TransformUnmarshalError(out, err) } return err } -func unmarshalDecode(in *jsontext.Decoder, out any, uo *jsonopts.Struct) (err error) { +func unmarshalDecode(in *jsontext.Decoder, out any, uo *jsonopts.Struct, last bool) (err error) { v := reflect.ValueOf(out) if v.Kind() != reflect.Pointer || v.IsNil() { return &SemanticError{action: "unmarshal", GoType: reflect.TypeOf(out), Err: internal.ErrNonNilReference} @@ -481,7 +469,11 @@ func unmarshalDecode(in *jsontext.Decoder, out any, uo *jsonopts.Struct) (err er // In legacy semantics, the entirety of the next JSON value // was validated before attempting to unmarshal it. if uo.Flags.Get(jsonflags.ReportErrorsWithLegacySemantics) { - if err := export.Decoder(in).CheckNextValue(); err != nil { + if err := export.Decoder(in).CheckNextValue(last); err != nil { + if err == io.EOF { + offset := in.InputOffset() + int64(len(in.UnreadBuffer())) + return &jsontext.SyntacticError{ByteOffset: offset, Err: io.ErrUnexpectedEOF} + } return err } } @@ -495,8 +487,15 @@ func unmarshalDecode(in *jsontext.Decoder, out any, uo *jsonopts.Struct) (err er if !uo.Flags.Get(jsonflags.AllowDuplicateNames) { export.Decoder(in).Tokens.InvalidateDisabledNamespaces() } + if err == io.EOF { + offset := in.InputOffset() + int64(len(in.UnreadBuffer())) + return &jsontext.SyntacticError{ByteOffset: offset, Err: io.ErrUnexpectedEOF} + } return err } + if last { + return export.Decoder(in).CheckEOF() + } return nil } -- 2.51.0