Don't allow EOF in the middle of a framing chunk.

decode.go

@@ -108,9 +108,9 @@ func (r *Reader) Reset(reader io.Reader) {
 	r.readHeader = false
 }
 
-func (r *Reader) readFull(p []byte) (ok bool) {
+func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
 	if _, r.err = io.ReadFull(r.r, p); r.err != nil {
-		if r.err == io.ErrUnexpectedEOF {
+		if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
 			r.err = ErrCorrupt
 		}
 		return false
@@ -129,7 +129,7 @@ func (r *Reader) Read(p []byte) (int, error) {
 			r.i += n
 			return n, nil
 		}
-		if !r.readFull(r.buf[:4]) {
+		if !r.readFull(r.buf[:4], true) {
 			return 0, r.err
 		}
 		chunkType := r.buf[0]
@@ -156,7 +156,7 @@ func (r *Reader) Read(p []byte) (int, error) {
 				return 0, r.err
 			}
 			buf := r.buf[:chunkLen]
-			if !r.readFull(buf) {
+			if !r.readFull(buf, false) {
 				return 0, r.err
 			}
 			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
@@ -189,7 +189,7 @@ func (r *Reader) Read(p []byte) (int, error) {
 				return 0, r.err
 			}
 			buf := r.buf[:checksumSize]
-			if !r.readFull(buf) {
+			if !r.readFull(buf, false) {
 				return 0, r.err
 			}
 			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
@@ -199,7 +199,7 @@ func (r *Reader) Read(p []byte) (int, error) {
 				r.err = ErrCorrupt
 				return 0, r.err
 			}
-			if !r.readFull(r.decoded[:n]) {
+			if !r.readFull(r.decoded[:n], false) {
 				return 0, r.err
 			}
 			if crc(r.decoded[:n]) != checksum {
@@ -215,7 +215,7 @@ func (r *Reader) Read(p []byte) (int, error) {
 				r.err = ErrCorrupt
 				return 0, r.err
 			}
-			if !r.readFull(r.buf[:len(magicBody)]) {
+			if !r.readFull(r.buf[:len(magicBody)], false) {
 				return 0, r.err
 			}
 			for i := 0; i < len(magicBody); i++ {
@@ -234,7 +234,7 @@ func (r *Reader) Read(p []byte) (int, error) {
 		}
 		// Section 4.4 Padding (chunk type 0xfe).
 		// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
-		if !r.readFull(r.buf[:chunkLen]) {
+		if !r.readFull(r.buf[:chunkLen], false) {
 			return 0, r.err
 		}
 	}

snappy_test.go

@@ -725,6 +725,31 @@ func TestFlush(t *testing.T) {
 	}
 }
 
+func TestReaderUncompressedDataOK(t *testing.T) {
+	r := NewReader(strings.NewReader(magicChunk +
+		"\x01\x08\x00\x00" + // Uncompressed chunk, 8 bytes long (including 4 byte checksum).
+		"\x68\x10\xe6\xb6" + // Checksum.
+		"\x61\x62\x63\x64", // Uncompressed payload: "abcd".
+	))
+	g, err := ioutil.ReadAll(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := string(g), "abcd"; got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestReaderUncompressedDataNoPayload(t *testing.T) {
+	r := NewReader(strings.NewReader(magicChunk +
+		"\x01\x04\x00\x00" + // Uncompressed chunk, 4 bytes long.
+		"", // No payload; corrupt input.
+	))
+	if _, err := ioutil.ReadAll(r); err != ErrCorrupt {
+		t.Fatalf("got %v, want %v", err, ErrCorrupt)
+	}
+}
+
 func TestReaderUncompressedDataTooLong(t *testing.T) {
 	// https://github.com/google/snappy/blob/master/framing_format.txt section
 	// 4.3 says that "the maximum legal chunk length... is 65540", or 0x10004.