commit 8003f08e512d166721d584db3033d7764f1a9a6b
author Damien Neil <dneil@google.com> Fri Aug 02 15:13:00 2019 -0700
committer Damien Neil <dneil@google.com> Mon Aug 05 21:44:30 2019 +0000
tree 56abc9ac66d63aca0ffb8ba2489f79c71255bf18
parent afd3633ce3ba0318ee242e4971734b116f890ae5

proto, internal/impl: zero-length proto2 bytes fields should be non-nil

Fix decoding of zero-length bytes fields to produce a non-nil []byte.

Change-Id: Ifb7791a47df81091700f7226523371d1386fb1ad
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/188765
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

internal/impl/codec_gen.go

diff --git a/internal/impl/codec_gen.go b/internal/impl/codec_gen.go
index 46380f5..f40af3d 100644
--- a/internal/impl/codec_gen.go
+++ b/internal/impl/codec_gen.go
@@ -4395,7 +4395,7 @@
 	if n < 0 {
 		return 0, wire.ParseError(n)
 	}
-	*p.Bytes() = append(([]byte)(nil), v...)
+	*p.Bytes() = append(emptyBuf[:], v...)
 	return n, nil
 }
 
@@ -4428,7 +4428,7 @@
 	if !utf8.Valid(v) {
 		return 0, errInvalidUTF8{}
 	}
-	*p.Bytes() = append(([]byte)(nil), v...)
+	*p.Bytes() = append(emptyBuf[:], v...)
 	return n, nil
 }
 
@@ -4460,10 +4460,24 @@
 	return b, nil
 }
 
+// consumeBytesNoZero wire decodes a []byte pointer as a Bytes.
+// The zero value is not decoded.
+func consumeBytesNoZero(b []byte, p pointer, wtyp wire.Type, _ unmarshalOptions) (n int, err error) {
+	if wtyp != wire.BytesType {
+		return 0, errUnknown
+	}
+	v, n := wire.ConsumeBytes(b)
+	if n < 0 {
+		return 0, wire.ParseError(n)
+	}
+	*p.Bytes() = append(([]byte)(nil), v...)
+	return n, nil
+}
+
 var coderBytesNoZero = pointerCoderFuncs{
 	size:      sizeBytesNoZero,
 	marshal:   appendBytesNoZero,
-	unmarshal: consumeBytes,
+	unmarshal: consumeBytesNoZero,
 }
 
 // appendBytesNoZeroValidateUTF8 wire encodes a []byte pointer as a Bytes.
@@ -4481,10 +4495,26 @@
 	return b, nil
 }
 
+// consumeBytesNoZeroValidateUTF8 wire decodes a []byte pointer as a Bytes.
+func consumeBytesNoZeroValidateUTF8(b []byte, p pointer, wtyp wire.Type, _ unmarshalOptions) (n int, err error) {
+	if wtyp != wire.BytesType {
+		return 0, errUnknown
+	}
+	v, n := wire.ConsumeBytes(b)
+	if n < 0 {
+		return 0, wire.ParseError(n)
+	}
+	if !utf8.Valid(v) {
+		return 0, errInvalidUTF8{}
+	}
+	*p.Bytes() = append(([]byte)(nil), v...)
+	return n, nil
+}
+
 var coderBytesNoZeroValidateUTF8 = pointerCoderFuncs{
 	size:      sizeBytesNoZero,
 	marshal:   appendBytesNoZeroValidateUTF8,
-	unmarshal: consumeBytesValidateUTF8,
+	unmarshal: consumeBytesNoZeroValidateUTF8,
 }
 
 // sizeBytesSlice returns the size of wire encoding a [][]byte pointer as a repeated Bytes.
@@ -4516,7 +4546,7 @@
 	if n < 0 {
 		return 0, wire.ParseError(n)
 	}
-	*sp = append(*sp, append(([]byte)(nil), v...))
+	*sp = append(*sp, append(emptyBuf[:], v...))
 	return n, nil
 }
 
@@ -4552,7 +4582,7 @@
 	if !utf8.Valid(v) {
 		return 0, errInvalidUTF8{}
 	}
-	*sp = append(*sp, append(([]byte)(nil), v...))
+	*sp = append(*sp, append(emptyBuf[:], v...))
 	return n, nil
 }
 
@@ -4585,7 +4615,7 @@
 	if n < 0 {
 		return nil, 0, wire.ParseError(n)
 	}
-	return append(([]byte)(nil), v...), n, nil
+	return append(emptyBuf[:], v...), n, nil
 }
 
 var coderBytesIface = ifaceCoderFuncs{
@@ -4617,7 +4647,7 @@
 	if !utf8.Valid(v) {
 		return nil, 0, errInvalidUTF8{}
 	}
-	return append(([]byte)(nil), v...), n, nil
+	return append(emptyBuf[:], v...), n, nil
 }
 
 var coderBytesIfaceValidateUTF8 = ifaceCoderFuncs{
@@ -4655,7 +4685,7 @@
 	if n < 0 {
 		return nil, 0, wire.ParseError(n)
 	}
-	*sp = append(*sp, append(([]byte)(nil), v...))
+	*sp = append(*sp, append(emptyBuf[:], v...))
 	return ival, n, nil
 }
 
@@ -4665,6 +4695,9 @@
 	unmarshal: consumeBytesSliceIface,
 }
 
+// We append to an empty array rather than a nil []byte to get non-nil zero-length byte slices.
+var emptyBuf [0]byte
+
 var wireTypes = map[protoreflect.Kind]wire.Type{
 	protoreflect.BoolKind:     wire.VarintType,
 	protoreflect.EnumKind:     wire.VarintType,