net/mail: fixed quoted-local

Fixes some minor issues regarding quoted-string when parsing
the local-part.

Those strings should return an error:
- quoted-string without any content: `""@test.com`
- quoted-string containing tab: "\"\t\"@test.com"

Fixes #11293

Change-Id: Ied93eb6831915c9b1f8e727cea14168af21f8d3b
Reviewed-on: https://go-review.googlesource.com/12905Reviewed-by: Russ Cox <rsc@golang.org>

src/net/mail/message.go

@@ -419,7 +419,7 @@ Loop:
 			}
 			qsb = append(qsb, p.s[i+1])
 			i += 2
-		case isQtext(c), c == ' ' || c == '\t':
+		case isQtext(c), c == ' ':
 			// qtext (printable US-ASCII excluding " and \), or
 			// FWS (almost; we're ignoring CRLF)
 			qsb = append(qsb, c)
@@ -429,6 +429,9 @@ Loop:
 		}
 	}
 	p.s = p.s[i+1:]
+	if len(qsb) == 0 {
+		return "", errors.New("mail: empty quoted-string")
+	}
 	return string(qsb), nil
 }
 

src/net/mail/message_test.go

@@ -522,6 +522,7 @@ func TestAddressParsingAndFormatting(t *testing.T) {
 		`<".john.doe"@example.com>`,
 		`<"."@example.com>`,
 		`<".."@example.com>`,
+		`<"0:"@0>`,
 	}
 
 	for _, test := range tests {
@@ -563,6 +564,8 @@ func TestAddressParsingAndFormatting(t *testing.T) {
 		`<test@.>`,
 		`< @example.com>`,
 		`<""test""blah""@example.com>`,
+		`<""@0>`,
+		"<\"\t0\"@0>",
 	}
 
 	for _, test := range badTests {