FWIW, I’d much rather that invalid characters in $tls_sni prompt an error.
There seems no reason to serve up meaningful content to someone who’s sending a malformed SNI header.
-Felipe Gasper
Mississauga, ON
> On Oct 17, 2016, at 11:42 PM, Jasen Betts <jasen@???> wrote:
>
> On 2016-10-17, Mike Tubby <mike@???> wrote:
>>
>> Couldn't we have - per perhaps shouldn't we have - a "safe domain name"
>> function in Exim that could be used for this and elsewhere where an
>> untrusted domain name enters - it would:
>>
>> * remove white space (tab, space, etc)
>> * remove non-printing chars
>> * remove 'quoting' and 'escaping'
>> * make it lower case
>> * only allow valid characters for a FQDN
>
> why remove? why not just reject if it contains any badness?
>
>> call it something like "safe_fqdn" and then you could do:
>>
>> ${if
>> exists{/etc/mail/ssl/${safe_fqdn:tls_sni}.pem}{/etc/mail/ssl/${safe_fqdn:tls_sni}.pem}{/etc/mail/default-cert.pem}
>>
>> aren't computers are supposed to be doing the work for us...?
>>
> This:
>
> ${domain:a@$tls_sni}
>
> will give the domain part if the $tls_sni is syntactically correct for a
> domain name else it will give the empty string.
>
> Is that not good enough?
>
>
> ${if exists{/etc/mail/ssl/${domain:a@$tls_sni}.pem}\
> {/etc/mail/ssl/${domain:a@$tls_sni}.pem}\
> {/etc/mail/default-cert.pem}\
> }
>
>
> it's going to try to use a file called /etc/mail/ssl/.pem if the sni
> is empty or contains garbage, probably not a problem.
>
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