Re: Curl with rsa-sha2-256, rsa-sha2-512

From: João M. S. Silva via curl-users <curl-users_at_lists.haxx.se>
Date: Mon, 15 May 2023 13:30:14 +0100

>
> > Note that above I modified curl's source code to set:
>
> > Set "rsa-sha2-256,rsa-sha2-512"
>
> I'm not sure that's the right move.
>

I have reverted it.


> Either way: a decent way to debug this would to first use the SSH library
> alone with an example program and make sure that works, as then we know
> for
> sure the issue is truly in curl.
>

libssh2 seems to support it since it's using openssl as a cryptographic
library and LIBSSH2_RSA_SHA2 is defined.

But when I upload a file to itself (localhost) it now fails with:

$ curl/src/curl -v -T A -u x:y scp://localhost:/home/shared/B
  % Total % Received % Xferd Average Speed Time Time Time
 Current
                                 Dload Upload Total Spent Left
 Speed
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:--
  0* Trying 127.0.0.1:22...
* Connected to localhost (127.0.0.1) port 22 (#0)
* Found host localhost in /home/shared/.ssh/known_hosts
* Set "rsa-sha2-256,rsa-sha2-512,ssh-rsa" as SSH hostkey type
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:--
  0* Failure establishing ssh session: -5, Unable to exchange encryption
keys
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:--
  0
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:--
  0
* Closing connection 0
curl: (2) Failure establishing ssh session: -5, Unable to exchange
encryption keys

However, this works:

$ scp -oHostKeyAlgorithms=rsa-sha2-256 A localhost:B

Using the ECDSA key also works.

$ grep HostKeyAlgorithms /etc/ssh/sshd_config
HostKeyAlgorithms
rsa-sha2-256,rsa-sha2-512,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521

So, this must be debugged alone in libssh2 or can we get more info from
curl?

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Received on 2023-05-15