Am 09.03.24 um 22:26 schrieb Julian Bradfield via Exim-users:
Following an idle-moment post on mailop, I wonder:

 From the default config:

---
acl_check_rcpt:

accept  hosts = :

deny    domains       = +local_domains
         local_parts   = ^[.] : ^.*[@%!/|]
         message       = Restricted characters in address

deny    domains       = !+local_domains
         local_parts   = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
         message       = Restricted characters in address

@Jeremy:

Why aren't the extended restrictions for the "$run{}" attack the new defaults?

          local_parts   = ^[.] : ^.*[\$@%!/|] : ^.*x24 : ^.*0.44
          local_parts   = ^[./|] : ^.*[\$@%!] : ^.*/\\.\\./ : ^.*x24 : ^.*0.44

Doesn't it make sense to have two barriers in the way and not relaying on only one defense line(the patched string expand flaw) ?

This does not costs us anything besides some cpu cycles. Existing configs won't get changed by new defaults for new installations. It could be changed with a new major release i.e. 4.98 .


Firstly, I don't understand the logic of accepting any address from an
stdio submission, while applying the restriction to a localhost tcp
submission.

Simple: on multiuser systems you never know who got hacked, has malicouse intents or uses faulty webapps. X


Secondly, is there really any reason nowadays for restricting % and !
?

The last time I saw a % address was in 1995, and the last time I saw a
! address was in 1994. (And of course, when I did see them, they had

As may imagined: hackers do not care when it was used last. They care, if it triggers something they can leverage.



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