BIND 9.18.6 disables RSASHA1 at runtime?

[Petr Špaček]

On 02. 09. 22 15:49, Anand Buddhdev wrote:
> On 02/09/2022 13:53, Mark Andrews wrote:
> 
> Hi Mark,
> 
>> We don’t log rsamd5 is disabled now ec or ed curves when they are
>> not  supported by the crypto provider. Why should rsasha1 based algs be 
> special?
> 
> The problem I see with 9.18.6 is that at startup, it is checking to see 
> if it can validate RSASHA1 signatures, and if it can't, it is disabling 
> the algorithm *silently*. I understand the reasoning, but I disagree 
> with it being disabled silently. If BIND is disabling something as 
> important as this at runtime, at the very least, a log entry about it 
> would go a long way towards helping system administrators. Here's my 
> reasoning:
> 
> There is a difference between RSAMD5 and RSASHA1. RFC 8624 clearly 
> forbids RSAMD5 for all uses, with "MUST NOT". It's fine for BIND to skip 
> validation for any zone signed with this algorithm.
> 
> RSASHA1 is quite different. The RFC recommends not signing with it, but 
> validation is still a must. Similarly, it forbids publishing SHA1 
> digests in DS records, but requires validation using them.
> 
> Now, on RedHat Linux 9 and its clones, SHA1 is disabled by *policy*. The 
> named.conf from the BIND package in this distro (version 9.16.23) 
> includes the file:
> 
> /etc/crypto-policies/back-ends/bind.config
> 
> and this file contains:
> 
> disable-algorithms "." {
> RSAMD5;
> RSASHA1;
> NSEC3RSASHA1;
> DSA;
> };
> disable-ds-digests "." {
> SHA-1;
> GOST;
> };
> 
> This is explicit declaration that SHA1 has been disabled.
> 
> But if one builds BIND >= 9.18.6 from pristine sources, the 
> configuration file is not going to include this snippet, and BIND is 
> going to silently disable SHA1. I strongly feel that BIND should log this.

Can you propose log line?

Should it be one line per algorithm? Or one line with all disabled? Or 
one one with all enabled? What log level? Log category? It it okay it 
will be almost always logging GOST? ...

So many questions to get log line covering < 2 % of all signed domains, 
which will be obsolete over time anyway (hopefully).

-- 
Petr Špaček