Re: Apparent dnsbl bug in Sendmail or m4

On Aug 22, 2010, at 6:40 AM, Stefan Bethke wrote:

> Am 22.08.2010 um 10:00 schrieb Stefan Bethke:
>=20
>> FEATURE(`dnsbl', `bl.spamcop.net', `"550 " $&{client_addr} "foo" =
$&{client_addr} ""')dnl
>=20
> The real culprit is the comma.  I believe the problem stems from =
unquoted use of the arguments in some of the ifelses, where the comma =
turns the single argument into two.

That makes a lot of sense, especially when combined with the off-list =
suggestions I got to double-quote the error message.

> Tracing the ifelses with -d aceq I see this for the last ifelse in =
cf/feature/dnsbl.m4:
>=20
> m4trace: -1- ifelse(`X"550 Mail from " $&{client_addr} " rejected', =
`see http://spamcop.net/bl.shtml?" $&{client_addr}', `Xquarantine', =
`R<?>$+         $#error $@ quarantine $: _DNSBL_SRV_', `X"550 Mail from =
" $&{client_addr} " rejected', `
> see http://spamcop.net/bl.shtml?" $&{client_addr}', `Xdiscard', =
`R<?>$+        =20
> $#discard $: _DNSBL_SRV_', `R<?>$+              $#error $@ 5.7.1 $: =
_DNSBL_MSG_'
> ) -> ???
> m4trace: -1- ifelse(...) -> `'
> m4trace: -1- ifelse ...
>=20
>=20
> I've never managed to really wrap my head around m4 quoting, but the =
easy fix is to use some other character that has no meaning to m4.

The fact that you knew how to do a trace shows that you're way ahead of =
me in grokking m4. :) I can confirm that replacing the comma with a =
colon makes the problem go away.

Does someone with some m4-fu want to take a stab at producing a fix? The =
problem appears in the 7-arg "ifelse" in the last few lines of =
/usr/share/sendmail/cf/feature/dnsbl.m4, though the source could of =
course be missing quotes earlier in the file.

I'd be happy to test any proposed patches and submit a bug report to =
Sendmail if appropriate. At the very least perhaps the example in the =
comment of /etc/mail/freebsd.mc should be modified to not use a comma.

Thanks!

JN

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