openssh unix dev - Oct 2018 - no mutual signature algorithm with RSA user certs client 7.8, server 7.4

On Thu, 11 Oct 2018, Damien Miller wrote:
> On Thu, 11 Oct 2018, Adam Eijdenberg wrote:
> 
> > Thanks for looking into. I wasn't able to get the patch to apply
> > cleanly to the portable source for whatever reason, so I manually made
> > the changes and got a little further. I now get past the "no
mutual
> > signature algorithm" client message, and get an error on the
server
> > side (OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017):
> > 
> > userauth_pubkey: unsupported public key algorithm:
> > rsa-sha2-512-cert-v01 at openssh.com [preauth]
> 
> Could you sent me a debug trace from the client for this? We shouldn't
> send this algorithm name unless the server supports it.
Could you try this?

diff --git a/sshconnect2.c b/sshconnect2.c
index f104408..1d2906f 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1080,7 +1080,8 @@ key_sig_algorithm(struct ssh *ssh, const struct sshkey
*key)
 	 * newer (SHA2) algorithms.
 	 */
 	if (ssh == NULL || ssh->kex->server_sig_algs == NULL ||
-	    (key->type != KEY_RSA && key->type != KEY_RSA_CERT)) {
+	    (key->type != KEY_RSA && key->type != KEY_RSA_CERT) ||
+	    (key->type == KEY_RSA_CERT && (datafellows &
SSH_BUG_SIGTYPE))) {
 		/* Filter base key signature alg against our configuration */
 		return match_list(sshkey_ssh_name(key),
 		    options.pubkey_key_types, NULL);

On Thu, Oct 11, 2018 at 12:13 PM Damien Miller <djm at mindrot.org>
wrote:
> Could you try this?
>
> diff --git a/sshconnect2.c b/sshconnect2.c
> index f104408..1d2906f 100644
> --- a/sshconnect2.c
> +++ b/sshconnect2.c
> @@ -1080,7 +1080,8 @@ key_sig_algorithm(struct ssh *ssh, const struct
sshkey *key)
>          * newer (SHA2) algorithms.
>          */
>         if (ssh == NULL || ssh->kex->server_sig_algs == NULL ||
> -           (key->type != KEY_RSA && key->type !=
KEY_RSA_CERT)) {
> +           (key->type != KEY_RSA && key->type !=
KEY_RSA_CERT) ||
> +           (key->type == KEY_RSA_CERT && (datafellows &
SSH_BUG_SIGTYPE))) {
>                 /* Filter base key signature alg against our configuration
*/
>                 return match_list(sshkey_ssh_name(key),
>                     options.pubkey_key_types, NULL);
That fixes it for me, thank you. Would you still like a copy of the
previous failing client trace?

On Thu, 11 Oct 2018, Adam Eijdenberg wrote:
> On Thu, Oct 11, 2018 at 12:13 PM Damien Miller <djm at mindrot.org>
wrote:
> > Could you try this?
> >
> > diff --git a/sshconnect2.c b/sshconnect2.c
> > index f104408..1d2906f 100644
> > --- a/sshconnect2.c
> > +++ b/sshconnect2.c
> > @@ -1080,7 +1080,8 @@ key_sig_algorithm(struct ssh *ssh, const struct
sshkey *key)
> >          * newer (SHA2) algorithms.
> >          */
> >         if (ssh == NULL || ssh->kex->server_sig_algs == NULL ||
> > -           (key->type != KEY_RSA && key->type !=
KEY_RSA_CERT)) {
> > +           (key->type != KEY_RSA && key->type !=
KEY_RSA_CERT) ||
> > +           (key->type == KEY_RSA_CERT && (datafellows
& SSH_BUG_SIGTYPE))) {
> >                 /* Filter base key signature alg against our
configuration */
> >                 return match_list(sshkey_ssh_name(key),
> >                     options.pubkey_key_types, NULL);
> 
> That fixes it for me, thank you. Would you still like a copy of the
> previous failing client trace?
No, I think I figured it out :)

On Thu, 11 Oct 2018, Adam Eijdenberg wrote:
> On Thu, Oct 11, 2018 at 12:13 PM Damien Miller <djm at mindrot.org>
wrote:
> > Could you try this?
> >
> > diff --git a/sshconnect2.c b/sshconnect2.c
> > index f104408..1d2906f 100644
> > --- a/sshconnect2.c
> > +++ b/sshconnect2.c
> > @@ -1080,7 +1080,8 @@ key_sig_algorithm(struct ssh *ssh, const struct
sshkey *key)
> >          * newer (SHA2) algorithms.
> >          */
> >         if (ssh == NULL || ssh->kex->server_sig_algs == NULL ||
> > -           (key->type != KEY_RSA && key->type !=
KEY_RSA_CERT)) {
> > +           (key->type != KEY_RSA && key->type !=
KEY_RSA_CERT) ||
> > +           (key->type == KEY_RSA_CERT && (datafellows
& SSH_BUG_SIGTYPE))) {
> >                 /* Filter base key signature alg against our
configuration */
> >                 return match_list(sshkey_ssh_name(key),
> >                     options.pubkey_key_types, NULL);
> 
> That fixes it for me, thank you. Would you still like a copy of the
> previous failing client trace?
That fix is committed and will be in the OpenSSH 7.9 release.

Thanks for catching those two bugs in time!

-d