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Re: Support_better_than_MD5_hostkey

From: Daniel Gustafsson via curl-library <curl-library_at_cool.haxx.se>
Date: Thu, 8 Jul 2021 14:56:16 +0200

> On 8 Jul 2021, at 14:05, Mats Lindestam via curl-library <curl-library_at_cool.haxx.se> wrote:

> I am trying to implement support for SHA256 public keys. I have been able to reach as far as the lib/vssh/libssh2.c file and the ssh_check_fingerprint function. Now I have no idea on how to calculate the SHA156 public key from the hostkey hash, a.k.a. 'fingerprint, in the same manner as done for the MD5 public key (See https://github.com/curl/curl/blob/master/lib/vssh/libssh2.c#L627). From where have you picked up the algorithm for MD5, from the 'The MD5 Message-Digest Algorithm' RFC (https://www.ietf.org/rfc/rfc1321.txt)?
> Is there an RFC that explains the 'The SHA256 Message-Digest Algorithm'?
> Does any know where to get information about this?

You don’t need to implment SHA256 on your own, in fact you really shouldn’t.
AFAICT libssh2 supports SHA256 by passing LIBSSH2_HOSTKEY_HASH_SHA256 to
libssh2_hostkey_hash().

--
Daniel Gustafsson		https://vmware.com/
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Received on 2021-07-08