Re: [exim] SNI and DANE TLSA record monitoring

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Szerző: Felipe Gasper
Dátum:  
Címzett: Mike Tubby
CC: exim-users
Tárgy: Re: [exim] SNI and DANE TLSA record monitoring
SNI is concerned strictly with the domain name, whereas virtual hosting (as I’ve seen it) concerns content.

Apache’s SNI configuration is poorly conceived, in my opinion. It forces all domains on a given virtual host to use the same certificate, which makes no sense. There is no reason whatsoever why “foo.com” and “bar.com” should have to serve up the same certificate--regardless of whether those two domains serve up the same content.

Exim’s approach of making the SNI request available and allowing the admin to do whatever with it is much more ideal. Please do NOT change this!

-FG

> On Oct 19, 2016, at 5:54 AM, Mike Tubby <mike@???> wrote:
>
> If what we're saying is that Exim needs to be virtual host capable then I think that we're on the edge of needing a proper virtual hosts sub-system that deals with:
>
>    1. naming the virtual host
>    2. configuring certificates
>    3. configuring TLS options (ciphers, etc)
>    4. configuring a logging location

>
> Mike
>
>
> On 10/19/2016 10:10 AM, Viktor Dukhovni wrote:
>> On Wed, Oct 12, 2016 at 02:50:41PM +0200, Arkadiusz Miśkiewicz wrote:
>>
>>> Docs say that $tls_sni has raw data from client:
>>>
>>> "Great care should be taken to deal with matters of case, various injection
>>> attacks in the string (../ or SQL), and ensuring that a valid filename can
>>> always be referenced; it is important to remember that $tls_sni is arbitrary
>>> unverified data provided prior to authentication."
>> While we're on the topic of Exim and SNI, I just interacted with
>> a user who rather admirably was monitoring his DANE TLSA records,
>> but his monitoring script was not sending the SNI extension as
>> required by RFC 7672. Sadly, his MX host was configured to respond
>> with a different (non-default) certificate when the SNI matched
>> the actual MX hostname. Consequently, the monitoring was flawed,
>> and missed a problem with certification rotation.
>>
>> So please keep in mind that SNI makes things a bit more complex
>> from a monitoring perspective. Avoid SNI if you can, use with
>> care if you must.
>>
>
>
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