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Message-ID: <20240926191139.GA9140@openwall.com>
Date: Thu, 26 Sep 2024 21:11:39 +0200
From: Solar Designer <solar@...nwall.com>
To: LinkinStar <linkinstar@...che.org>
Cc: oss-security@...ts.openwall.com
Subject: Re: CVE-2024-40761: Apache Answer: Avatar URL leaked user email addresses
Hi LinkinStar,
There were several more replies from others, please see in the list
archive if you're not subscribed:
https://www.openwall.com/lists/oss-security/
On Thu, Sep 26, 2024 at 10:10:38AM +0800, LinkinStar wrote:
> Because *Gravatar recommends using sha-256*, we believe there must be a
> reason for its modification. Since the official recommendation is to change
> the encryption method, why not implement it according to the official
> requirements? You must admit that sha-256 is more difficult than md5, even
> if only slightly. Although this may not completely solve the problem, I
> believe following the official recommendation would be marginally better,
> wouldn't it? So I think this fix itself is acceptable.
The change is fine - just don't call it a security fix. Also, this is
hashing and not encryption.
Others pointed out that Gravatar's recommendation is just that - not a
specification - so unless you need interoperability with other servers
implementing Gravatar, you can do better than SHA-256. Specifically,
use of a keyed hash such as HMAC-SHA256 was suggested and makes sense to
me - as long as the key is generated from a CSPRNG (such as
/dev/urandom) and is large enough (such as 32 bytes).
Alexander
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