net/mail: enhanced Address.String and ParseAddress to match RFC 5322

Updated Address.String so it restores quoted local parts, which wasn't
done before.
When parsing `<" "@example.com>`, the formatted string returned
`< @example>`, which doens't match RFC 5322, since a space is not atext.
Another example is `<"bob@valid"@example.com>` which returned
`<bob@valid@example.com>`, which is completely invalid.
I also added support for quotes and backslashes in a quoted local part.

Besides formatting a parsed Address, the ParseAddress function also
needed more testing and finetuning for special cases.
Things like `<.john.doe@example.com>` and `<john..doe@example.com>`
e.a. were accepted, but are invalid.
I fixed those details and add tests for some other special cases.

Fixes #10768

Change-Id: Ib0caf8ad603eb21e32fcb957a5f1a0fe5d1c6e6e
Reviewed-on: https://go-review.googlesource.com/8724
Reviewed-by: Russ Cox <rsc@golang.org>

1 files changed, 92 insertions, 0 deletions

diff --git a/src/net/mail/message_test.go b/src/net/mail/message_test.go
index 43574c6188..1da3213f7e 100644
--- a/src/net/mail/message_test.go
+++ b/src/net/mail/message_test.go
@@ -458,6 +458,14 @@ func TestAddressFormatting(t *testing.T) {
 			&Address{Address: "bob@example.com"},
 			"<bob@example.com>",
 		},
+		{ // quoted local parts: RFC 5322, 3.4.1. and 3.2.4.
+			&Address{Address: `my@idiot@address@example.com`},
+			`<"my@idiot@address"@example.com>`,
+		},
+		{ // quoted local parts
+			&Address{Address: ` @example.com`},
+			`<" "@example.com>`,
+		},
 		{
 			&Address{Name: "Bob", Address: "bob@example.com"},
 			`"Bob" <bob@example.com>`,
@@ -483,3 +491,87 @@ func TestAddressFormatting(t *testing.T) {
 		}
 	}
 }
+
+// Check if all valid addresses can be parsed, formatted and parsed again
+func TestAddressParsingAndFormatting(t *testing.T) {
+
+	// Should pass
+	tests := []string{
+		`<Bob@example.com>`,
+		`<bob.bob@example.com>`,
+		`<".bob"@example.com>`,
+		`<" "@example.com>`,
+		`<some.mail-with-dash@example.com>`,
+		`<"dot.and space"@example.com>`,
+		`<"very.unusual.@.unusual.com"@example.com>`,
+		`<admin@mailserver1>`,
+		`<postmaster@localhost>`,
+		"<#!$%&'*+-/=?^_`{}|~@example.org>",
+		`<"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com>`, // escaped quotes
+		`<"()<>[]:,;@\\\"!#$%&'*+-/=?^_{}| ~.a"@example.org>`,                      // escaped backslashes
+		`<"Abc\\@def"@example.com>`,
+		`<"Joe\\Blow"@example.com>`,
+		`<test1/test2=test3@example.com>`,
+		`<def!xyz%abc@example.com>`,
+		`<_somename@example.com>`,
+		`<joe@uk>`,
+		`<~@example.com>`,
+		`<"..."@test.com>`,
+		`<"john..doe"@example.com>`,
+		`<"john.doe."@example.com>`,
+		`<".john.doe"@example.com>`,
+		`<"."@example.com>`,
+		`<".."@example.com>`,
+	}
+
+	for _, test := range tests {
+		addr, err := ParseAddress(test)
+		if err != nil {
+			t.Errorf("Couldn't parse address %s: %s", test, err.Error())
+			continue
+		}
+		str := addr.String()
+		addr, err = ParseAddress(str)
+		if err != nil {
+			t.Errorf("ParseAddr(%q) error: %v", test, err)
+			continue
+		}
+
+		if addr.String() != test {
+			t.Errorf("String() round-trip = %q; want %q", addr, test)
+			continue
+		}
+
+	}
+
+	// Should fail
+	badTests := []string{
+		`<Abc.example.com>`,
+		`<A@b@c@example.com>`,
+		`<a"b(c)d,e:f;g<h>i[j\k]l@example.com>`,
+		`<just"not"right@example.com>`,
+		`<this is"not\allowed@example.com>`,
+		`<this\ still\"not\\allowed@example.com>`,
+		`<john..doe@example.com>`,
+		`<john.doe@example..com>`,
+		`<john.doe@example..com>`,
+		`<john.doe.@example.com>`,
+		`<john.doe.@.example.com>`,
+		`<.john.doe@example.com>`,
+		`<@example.com>`,
+		`<.@example.com>`,
+		`<test@.>`,
+		`< @example.com>`,
+		`<""test""blah""@example.com>`,
+	}
+
+	for _, test := range badTests {
+		_, err := ParseAddress(test)
+		if err == nil {
+			t.Errorf("Should have failed to parse address: %s", test)
+			continue
+		}
+
+	}
+
+}