From 5ba0c29655be05b4aa816fbb0bbf7d36f20ea4d8 Mon Sep 17 00:00:00 2001
From: Damien Neil <dneil@google.com>
Date: Sat, 21 Dec 2019 09:45:00 -0800
Subject: [PATCH] internal/encoding/json: fix crash in parsing

Fuzzer-detected crash when parsing: {""

Change-Id: I019c667f48e6a1237858b5abf7d34f43593fb3b6
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/212357
Reviewed-by: Herbie Ong <herbie@google.com>
---
 internal/encoding/json/decode.go      | 3 +++
 internal/encoding/json/decode_test.go | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/internal/encoding/json/decode.go b/internal/encoding/json/decode.go
index ae2ee9ab..3e58d069 100644
--- a/internal/encoding/json/decode.go
+++ b/internal/encoding/json/decode.go
@@ -102,6 +102,9 @@ func (d *Decoder) Read() (Value, error) {
 		}
 		d.in = d.in[n:]
 		d.consume(0)
+		if len(d.in) == 0 {
+			return Value{}, d.newSyntaxError(`unexpected EOF, missing ":" after object name`)
+		}
 		if c := d.in[0]; c != ':' {
 			return Value{}, d.newSyntaxError(`unexpected character %v, missing ":" after object name`, string(c))
 		}
diff --git a/internal/encoding/json/decode_test.go b/internal/encoding/json/decode_test.go
index c29d5087..c896a2ea 100644
--- a/internal/encoding/json/decode_test.go
+++ b/internal/encoding/json/decode_test.go
@@ -872,6 +872,13 @@ func TestDecoder(t *testing.T) {
 				{E: `unexpected EOF`},
 			},
 		},
+		{
+			input: `{""`,
+			want: []R{
+				{T: json.StartObject},
+				{E: `syntax error (line 1:4): unexpected EOF`},
+			},
+		},
 		{
 			input: `{"34":"89",}`,
 			want: []R{