sendmail allow "=" symbol in recipient, closes 10241

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/mailutils/sendmail.c b/mailutils/sendmail.c
index defbd9552..4ca91fad8 100644
--- a/mailutils/sendmail.c
+++ b/mailutils/sendmail.c
@@ -150,7 +150,13 @@ static char *sane_address(char *str)
         trim(str);
         s = str;
         while (*s) {
-                if (!isalnum(*s) && !strchr("+_-.@", *s)) {
+                /* Standard allows these chars in username without quoting:
+                 * /!#$%&'*+-=?^_`{|}~
+                 * and allows dot (.) with some restrictions.
+                 * I chose to only allow a saner subset.
+                 * I propose to expand it only on user's request.
+                 */
+                if (!isalnum(*s) && !strchr("=+_-.@", *s)) {
                         bb_error_msg("bad address '%s'", str);
                         /* returning "": */
                         str[0] = '\0';