net/mail: use base64 encoding when needed in Address.String()

When the name of an Address contains non-ASCII characters,
Address.String() used mime.QEncoding to encode the name.

However certain characters are forbidden when an encoded-word is
in a phrase context (see RFC 2047 section 5.3) and these
characters are not encoded by mime.QEncoding.

In this case we now use mime.BEncoding (base64 encoding) so that
forbidden characters are also encoded.

Fixes golang#11292

Change-Id: I52db98b41ece439295e97d7e94c8190426f499c2
Reviewed-on: https://go-review.googlesource.com/16012
Reviewed-by: Brad Fitzpatrick <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

src/net/mail/message.go

@@ -234,6 +234,12 @@ func (a *Address) String() string {
 		return b.String()
 	}
 
+	// Text in an encoded-word in a display-name must not contain certain
+	// characters like quotes or parentheses (see RFC 2047 section 5.3).
+	// When this is the case encode the name using base64 encoding.
+	if strings.ContainsAny(a.Name, "\"#$%&'(),.:;<>@[]^`{|}~") {
+		return mime.BEncoding.Encode("utf-8", a.Name) + " " + s
+	}
 	return mime.QEncoding.Encode("utf-8", a.Name) + " " + s
 }
 

src/net/mail/message_test.go

@@ -499,6 +499,10 @@ func TestAddressFormatting(t *testing.T) {
 			&Address{Name: "Rob", Address: "@"},
 			`"Rob" <@>`,
 		},
+		{
+			&Address{Name: "Böb, Jacöb", Address: "[email protected]"},
+			`=?utf-8?b?QsO2YiwgSmFjw7Zi?= <[email protected]>`,
+		},
 	}
 	for _, test := range tests {
 		s := test.addr.String()
@@ -594,3 +598,32 @@ func TestAddressParsingAndFormatting(t *testing.T) {
 	}
 
 }
+
+func TestAddressFormattingAndParsing(t *testing.T) {
+	tests := []*Address{
+		&Address{Name: "@lïce", Address: "[email protected]"},
+		&Address{Name: "Böb O'Connor", Address: "[email protected]"},
+		&Address{Name: "???", Address: "[email protected]"},
+		&Address{Name: "Böb ???", Address: "[email protected]"},
+		&Address{Name: "Böb (Jacöb)", Address: "[email protected]"},
+		&Address{Name: "à#$%&'(),.:;<>@[]^`{|}~'", Address: "[email protected]"},
+		// https://golang.org/issue/11292
+		&Address{Name: "\"\\\x1f,\"", Address: "0@0"},
+		// https://golang.org/issue/12782
+		&Address{Name: "naé, mée", Address: "[email protected]"},
+	}
+
+	for _, test := range tests {
+		parsed, err := ParseAddress(test.String())
+		if err != nil {
+			t.Errorf("ParseAddr(%q) error: %v", test.String(), err)
+			continue
+		}
+		if parsed.Name != test.Name {
+			t.Errorf("Parsed name = %q; want %q", parsed.Name, test.Name)
+		}
+		if parsed.Address != test.Address {
+			t.Errorf("Parsed address = %q; want %q", parsed.Address, test.Address)
+		}
+	}
+}