On 06-06-16 20:26, Tom Hendrikx wrote:
> On 06-06-16 17:46, Viktor Dukhovni wrote:
>> On Mon, Jun 06, 2016 at 05:31:49PM +0200, Tom Hendrikx wrote:
>>
>>> I have been playing around with the dane check tool from sys4 too, and
>>> it seems it doesn't support the nice CNAME trick shown in
>>> https://community.letsencrypt.org/t/please-avoid-3-0-1-and-3-0-2-dane-tlsa-records-with-le-certificates/7022
>>
>> In the dane.sys4.de test code CNAMEs in TLSA records are supported
>> and work, provided the target of the CNAME is in a signed zone of
>> course.  MX hosts that are CNAMEs are deliberately not supported
>> as these violate the RFC requirements for MX records.
>>
>> For example:
>>
>>     _25._tcp.gazonk.org.    CNAME   _tlsa.gazonk.org.
>>     _tlsa.gazonk.org.       TLSA    3 1 1 
>> 2EE262031C03AD1143E557074DADCE1F681F1818D6B0DC59ED33F472 6B180B6C
>>
>> For which https://dane.sys4.de correctly shows (that this domain
>> is misconfigured by promising and then not offering  STARTTLS):
>>
>>     42 gazonk.org
>>        212.247.24.42: STARTTLS not offered
>>
>>     IP Addresses
>>        212.247.24.42
>>
>>     Usable TLSA Records
>>        3, 1, 1 2ee262031c03ad11[...]ed33f4726b180b6c
>>
> 
> I did some further research. It seems that validns does not like this
> construct, because it insists that TLSA records are 'properly prefixed'
> (i.e. with a port and service prefix, see [1]).

Insists, as a policy check, which I have enabled (but is off by default)...

> 
> My dnssec auto-signing setup invalidated the zone because of this, so it
> was never published with these records, concluding in the sane tool not
> being able to see them. My bad...
> 
> [1]
> https://github.com/tobez/validns/blob/5a374cf1d629d8d2fecdf6f215aec9b056370868/tlsa.c#L87
> 
> Regards,
>       Tom
> 


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