bug#51733: 27.1; Detect impossible email addresses better

[Robert Pluim]

>>>>> On Wed, 19 Jan 2022 13:53:59 +0200, Eli Zaretskii <eliz@gnu.org> said:

    Eli> Here:

    Eli>   (textsec-email-suspicious-p "אבגד <foo@bar.com>")
    Eli>     => (wrong-type-argument stringp nil)

    Eli> with this backtrace:

    Eli>   Debugger entered--Lisp error: (wrong-type-argument stringp nil)
    Eli>     string-search("=?" nil)
    Eli>     rfc2047-decode-string(nil)
    Eli>     mail-header-parse-address("אבגד <foo@bar.com>" t)
    Eli>     textsec-email-suspicious-p("אבגד <foo@bar.com>")
    Eli>     (progn (textsec-email-suspicious-p "אבגד <foo@bar.com>"))
    Eli>     eval((progn (textsec-email-suspicious-p "אבגד <foo@bar.com>")) t)
    Eli>     elisp--eval-last-sexp(t)
    Eli>     eval-last-sexp(t)
    Eli>     eval-print-last-sexp(nil)
    Eli>     funcall-interactively(eval-print-last-sexp nil)
    Eli>     call-interactively(eval-print-last-sexp nil nil)
    Eli>     command-execute(eval-print-last-sexp)

mail-header-parse-address assumes that the display name or the local
name starts with a (subset of) ASCII. The following doesnʼt signal an
error:

(textsec-email-suspicious-p "דגבאa <foo@bar.com>")

Since itʼs now open season on display names and mailbox names, the
following might be enough. Lars?

diff --git a/lisp/mail/ietf-drums.el b/lisp/mail/ietf-drums.el
index 4a07959189..1885f958ba 100644
--- a/lisp/mail/ietf-drums.el
+++ b/lisp/mail/ietf-drums.el
@@ -217,7 +217,7 @@ ietf-drums-parse-address
          (push (buffer-substring
                 (1+ (point)) (progn (forward-sexp 1) (1- (point))))
                display-name))
-        ((looking-at (concat "[" ietf-drums-atext-token "@" "]"))
+        ((not (eq c ?<))
          (push (buffer-substring (point) (progn (forward-sexp 1) (point)))
                display-name))
         ((eq c ?<)
@@ -240,7 +240,7 @@ ietf-drums-parse-address
            (cons
             (mapconcat #'identity (nreverse display-name) "")
             (ietf-drums-get-comment string)))
-       (cons mailbox (if decode
+       (cons mailbox (if (and decode display-string)
                           (rfc2047-decode-string display-string)
                         display-string))))))
 

Robert
--