From 8d76c56a31bb10a182e3240fa55d3d748f1daa6c Mon Sep 17 00:00:00 2001
From: Lucas Bremgartner <lucas@bremis.ch>
Date: Mon, 16 Sep 2019 19:46:12 +0000
Subject: [PATCH] encoding/json: validate strings when decoding into Number
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Unmarshaling a string into a json.Number should first check that the string is a valid Number.
If not, we should fail without decoding it.

Fixes #14702

Change-Id: I286178e93df74ad63c0a852c3f3489577072cf47
GitHub-Last-Rev: fe69bb68eed06d056639f440d2daf4bb7c99013b
GitHub-Pull-Request: golang/go#34272
Reviewed-on: https://go-review.googlesource.com/c/go/+/195045
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 decode.go      |  3 +++
 decode_test.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/decode.go b/decode.go
index 360fc69..407fbce 100644
--- a/decode.go
+++ b/decode.go
@@ -949,6 +949,9 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			}
 			v.SetBytes(b[:n])
 		case reflect.String:
+			if v.Type() == numberType && !isValidNumber(string(s)) {
+				return fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item)
+			}
 			v.SetString(string(s))
 		case reflect.Interface:
 			if v.NumMethod() == 0 {
diff --git a/decode_test.go b/decode_test.go
index 489f867..4cbd217 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -949,6 +949,37 @@ var unmarshalTests = []unmarshalTest{
 			Offset: 29,
 		},
 	},
+	// #14702
+	{
+		in:  `invalid`,
+		ptr: new(Number),
+		err: &SyntaxError{
+			msg:    "invalid character 'i' looking for beginning of value",
+			Offset: 1,
+		},
+	},
+	{
+		in:  `"invalid"`,
+		ptr: new(Number),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+	{
+		in:  `{"A":"invalid"}`,
+		ptr: new(struct{ A Number }),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+	{
+		in: `{"A":"invalid"}`,
+		ptr: new(struct {
+			A Number `json:",string"`
+		}),
+		err: fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into json.Number", `invalid`),
+	},
+	{
+		in:  `{"A":"invalid"}`,
+		ptr: new(map[string]Number),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
 }
 
 func TestMarshal(t *testing.T) {