Hi Ben,

Comments inline.

 

> Should it instead say, "The recommended way to provide this is to ensure each 
> certificate is logged to CT and then list the crt.sh fingerprint URL for each 
> certificate in the format 'https://crt.sh/?q=[sha256 
> <https://crt.sh/?q=%5bsha256>  hash]', ...."? 

 

The current language on the Wiki doesn’t explicitly “encourage” the use of 
crt.sh (one can list fingerprints and not provide them in a crt.sh URL), 
whereas this proposal does. Not to besmirch crt.sh (it’s a great tool), but I 
don’t think we should recommend the use of a single tool over an interoperable 
solution. Namely, we should encourage listing SHA256 fingerprints and leave it 
to the reader to supply those fingerprints to the tool of their choice, whether 
that be crt.sh, Censys, or something else.

 

> Should the SHA1 fingerprint also be allowed?

 

I think we should encourage the use of SHA256 fingerprints and discourage other 
hash algorithms. Popular tooling (crt.sh, Censys, etc.) supports SHA256 
fingerprints, whereas support for other algorithms may not be as universal.

 

> What is the preferred method, and which other alternatives should be allowed 
> for unambiguously reporting / locating the certificates or their "complete 
> certificate data"?

 

An alternative method would be to allow the specification of a CT log’s base 
URI and the entry number of the affected certificate. Uptime of CT logs is 
monitored by at least one Root Program, which provides assurance that the 
certificate can be retrieved. Additionally, retrieving the certificate is done 
in a documented, standard manner (any CT client can fetch the certificate).

 

Thanks,

Corey

 

From: [email protected] <[email protected]> On 
Behalf Of Ben Wilson
Sent: Wednesday, November 17, 2021 5:47 PM
To: [email protected] <[email protected]>
Subject: Use of crt.sh ID in Incident Reports

 

All,

 

In an incident report recently, there was discussion about the right way to 
report the certificates involved in the incident. See 
https://bugzilla.mozilla.org/show_bug.cgi?id=1736064

 

In section 5 of 
https://wiki.mozilla.org/CA/Responding_To_An_Incident#Incident_Report, it 
currently says, "5. In a case involving TLS server certificates, the complete 
certificate data for the problematic certificates. The recommended way to 
provide this is to ensure each certificate is logged to CT and then list the 
fingerprints or crt.sh IDs, either in the report or as an attached spreadsheet, 
with one list per distinct problem." 

 

We are thinking of removing the reference to the "crt.sh ID" and clarifying the 
instructions on providing the certificate fingerprints. Instead of the crt.sh 
database ID, for instance, crt.sh currently supports a lookup based on the 
SHA256 hash (https://crt.sh/?q=[sha256 <https://crt.sh/?q=%5bsha256>  hash]).

 

Should it instead say, "The recommended way to provide this is to ensure each 
certificate is logged to CT and then list the crt.sh fingerprint URL for each 
certificate in the format 'https://crt.sh/?q=[sha256 
<https://crt.sh/?q=%5bsha256>  hash]', ...."? Should the SHA1 fingerprint also 
be allowed?

 

What is the preferred method, and which other alternatives should be allowed 
for unambiguously reporting / locating the certificates or their "complete 
certificate data"?

 

Thanks,

 

Ben

 

 

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