Addresses with quoted string with a folding white space fail validation

[JakubJanowski]

Hi, I've noticed that these addresses fail to validate but should be allowed under RFC 5322:

EmailValidator.Validate("\"FWS\r\n test\"@iana.org");
EmailValidator.Validate("\"FWS\r\n\ttest\"@iana.org");

I've gathered the necessary definitions from sections 3.4.1

addr-spec       =   local-part "@" domain

local-part      =   dot-atom / quoted-string / obs-local-part

3.2.4

qtext           =   %d33 /             ; Printable US-ASCII
                    %d35-91 /          ;  characters not including
                    %d93-126 /         ;  "\" or the quote character
                    obs-qtext

qcontent        =   qtext / quoted-pair

quoted-string   =   [CFWS]
                    DQUOTE *([FWS] qcontent) [FWS] DQUOTE
                    [CFWS]

3.2.2

FWS             =   ([*WSP CRLF] 1*WSP) /  obs-FWS
                                       ; Folding white space

and RFC 5234 Appendix B.1

CR             =  %x0D
                       ; carriage return

CRLF           =  CR LF
                       ; Internet standard newline
(...)
DQUOTE         =  %x22
                       ; " (Double Quote)
(...)
HTAB           =  %x09
                       ; horizontal tab

LF             =  %x0A
                       ; linefeed
(...)
SP             =  %x20
(...)
WSP            =  SP / HTAB
                       ; white space

This shows that the local-part of an address can be a quoted-string that contains a FWS (Folding white space) anywhere, separated by qcontent. Right now only spaces inside quotes are considered valid by the validator. Spaces alone also form a Folding white space but it can also consist of horizontal tabs and a single Windows-style newline .

I've prepared a few test cases for this. These should validate:

EmailValidator.Validate("\"FWS\ttest\"@iana.org");
EmailValidator.Validate("\" \t\"@iana.org");
EmailValidator.Validate("\" \t\r\n \t\"@iana.org");
EmailValidator.Validate("\"FWS\r\n x\r\n test\"@iana.org");

These should fail:

EmailValidator.Validate("\"FWS\r\ntest\"@iana.org");
EmailValidator.Validate("\"FWS\r test\"@iana.org");
EmailValidator.Validate("\"FWS\n test\"@iana.org");
EmailValidator.Validate("\"FWS\r\n \r\n test\"@iana.org");

[jstedfast]

No, they should not validate. You are looking at the wrong spec.

[JakubJanowski]

Right, my mistake. I think it would be useful to mention in the readme that this is a validator for SMTP envelope type email address instead of IMF type address.