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grantksupport at operamail.com

2015-Jan-09 16:05 UTC

OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

I run OpenSSH on linux

	@ client

		which ssh
			/usr/local/bin/ssh
		ssh -v
			OpenSSH_6.7p1, OpenSSL 1.0.1j 15 Oct 2014

	@ server

		which sshd
			/usr/local/bin/sshd
		sshd -v
			unknown option -- V
			OpenSSH_6.7p1, OpenSSL 1.0.1j 15 Oct 2014
			usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]
			            [-E log_file] [-f config_file] [-g login_grace_time]
			            [-h host_key_file] [-k key_gen_time] [-o option] [-p port]


I have configured for hostbased authentication

	client ssh_config
		...
		PreferredAuthentications           hostbased,publickey
		HostbasedAuthentication            yes
		PubkeyAuthentication               yes
		PasswordAuthentication             no
		...

	server sshd_config
		...
		AuthenticationMethods              hostbased,publickey
		HostbasedAuthentication            yes
		HostbasedUsesNameFromPacketOnly    yes
		PubkeyAuthentication               yes
		PasswordAuthentication             no
		...

on the server, because I'm not entirely sure where to put it yet

	echo "client.DOMAIN.COM" > /etc/shosts.equiv
	echo "client.DOMAIN.COM" > /usr/local/etc/shosts.equiv

when I try to connect

	ssh -vvv server.DOMAIN.COM

hostname auth fails

	...
	Permission denied (hostbased).

debug logs return

	client log
		...
		debug1: Authentications that can continue: hostbased
		debug3: start over, passed a different list hostbased
		debug3: preferred hostbased,publickey
		debug3: authmethod_lookup hostbased
		debug3: remaining preferred: publickey,password
		debug3: authmethod_is_enabled hostbased
		debug1: Next authentication method: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug1: No more client hostkeys for hostbased authentication.
		debug2: we did not send a packet, disable method
		debug1: No more authentication methods to try.
		Permission denied (hostbased).

	server log
		...
		Jan  9 07:37:31 server sshd[19835]: debug2: input_userauth_request: try method
hostbased [preauth]
		Jan  9 07:37:31 server sshd[19835]: debug1: userauth_hostbased: cuser root
chost client.DOMAIN.COM. pkalg ssh-ed25519 slen 83 [preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_key_allowed entering [preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_request_send entering: type 22
[preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_key_allowed: waiting for
MONITOR_ANS_KEYALLOWED [preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_request_receive_expect
entering: type 23 [preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_request_receive entering
[preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_request_receive entering
		Jan  9 07:37:31 server sshd[19835]: debug3: monitor_read: checking request 22
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_answer_keyallowed entering
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_answer_keyallowed:
key_from_blob: 0x7cd1262cbc76
		Jan  9 07:37:31 server sshd[19835]: debug2: userauth_hostbased: chost
client.DOMAIN.COM. resolvedname xxxx:xxx:xxxx:xxx::10 ipaddr
xxxx:xxx:xxxx:xxx::10
		Jan  9 07:37:31 server sshd[19835]: debug2: stripping trailing dot from chost
client.DOMAIN.COM.
		Jan  9 07:37:31 server sshd[19835]: debug2: auth_rhosts2: clientuser root
hostname client.DOMAIN.COM ipaddr client.DOMAIN.COM
		Jan  9 07:37:31 server sshd[19835]: debug1: temporarily_use_uid: 0/0 (e=0/0)
		Jan  9 07:37:31 server sshd[19835]: debug1: restore_uid: 0/0
		Jan  9 07:37:31 server sshd[19835]: debug1: temporarily_use_uid: 0/0 (e=0/0)
		Jan  9 07:37:31 server sshd[19835]: debug1: restore_uid: 0/0
		Jan  9 07:37:31 server sshd[19835]: Failed hostbased for root from
xxxx:xxx:xxxx:xxx::10 port 40452 ssh2: ED25519
xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx, client user "root",
client host "client.DOMAIN.COM"
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_answer_keyallowed: key
0x7cd1262cbc76 is not allowed
		Jan  9 07:37:31 server sshd[19835]: debug3: mm_request_send entering: type 23
		Jan  9 07:37:31 server sshd[19835]: debug2: userauth_hostbased: authenticated
0 [preauth]
		Jan  9 07:37:31 server sshd[19835]: debug3: userauth_finish: failure partial=0
next methods="hostbased" [preauth]
		...

I see that

	mm_answer_keyallowed: key 0x7cd1262cbc76 is not allowed

but am not clear what key that is.  grep'ing for '7cd1262cbc76'
turns up nothing.

What's wrong or missing in my config?

Tim Rice

2015-Jan-09 18:48 UTC

head link

OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

On Fri, 9 Jan 2015, grantksupport at operamail.com wrote:

| 			OpenSSH_6.7p1, OpenSSL 1.0.1j 15 Oct 2014

| I have configured for hostbased authentication
| 
| 	client ssh_config
| 		...
| 		PreferredAuthentications           hostbased,publickey
| 		HostbasedAuthentication            yes
| 		PubkeyAuthentication               yes
| 		PasswordAuthentication             no
| 		...
| 
| 	server sshd_config
| 		...
| 		AuthenticationMethods              hostbased,publickey
| 		HostbasedAuthentication            yes
| 		HostbasedUsesNameFromPacketOnly    yes
| 		PubkeyAuthentication               yes
| 		PasswordAuthentication             no
| 		...
| 
| on the server, because I'm not entirely sure where to put it yet
| 
| 	echo "client.DOMAIN.COM" > /etc/shosts.equiv
| 	echo "client.DOMAIN.COM" > /usr/local/etc/shosts.equiv

| What's wrong or missing in my config?

My ssh_config has
Host *
  HostbasedAuthentication yes
  EnableSSHKeysign yes
  NoHostAuthenticationForLocalhost yes

NoHostAuthenticationForLocalhost is not necessary.
The one you are missing is EnableSSHKeysign.

Additionally, you made no mention of your ssh_known_hosts files. Make
sure the client's public keys are in the server's ssh_known_hosts file.


-- 
Tim Rice				Multitalents
tim at multitalents.net

Iain Morgan

2015-Jan-09 19:40 UTC

head link

OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

To begin with, don't complicate the situation by requiring two forms of
authentication before you've gotten a single form of authentication
working. In addition, root is too much of a special case for useful
debugging; try your tests as a regular user.

As Tim Rice noted, you will need to set EnableSSHKeysign in the
system--wide client configuration for hostbased authentication to work
for non-root users.

-- 
Iain Morgan

grantksupport at operamail.com

2015-Jan-09 20:07 UTC

head link

OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

Hi,

On Fri, Jan 9, 2015, at 10:48 AM, Tim Rice wrote:> My ssh_config has
> Host *
>   HostbasedAuthentication yes
>   EnableSSHKeysign yes
>   NoHostAuthenticationForLocalhost yes
> 
> NoHostAuthenticationForLocalhost is not necessary.
> The one you are missing is EnableSSHKeysign.
> 
> Additionally, you made no mention of your ssh_known_hosts files. Make
> sure the client's public keys are in the server's ssh_known_hosts
file.

On Fri, Jan 9, 2015, at 11:40 AM, Iain Morgan wrote:> To begin with, don't complicate the situation by requiring two forms of
> authentication before you've gotten a single form of authentication
> working. In addition, root is too much of a special case for useful
> debugging; try your tests as a regular user.
> 
> As Tim Rice noted, you will need to set EnableSSHKeysign in the
> system--wide client configuration for hostbased authentication to work
> for non-root users.
I edited configs to

	client ssh_config
		...
-		PreferredAuthentications           hostbased,publickey
+		PreferredAuthentications           hostbased
		HostbasedAuthentication            yes
		PubkeyAuthentication               yes
+		PubkeyAuthentication               no
		PasswordAuthentication             no
		...
		EnableSSHKeysign                   yes      (note: this had already been
'in there' --- just further down in the config)
		...

	server sshd_config
		...
-		AuthenticationMethods              hostbased,publickey
+		AuthenticationMethods              hostbased
		HostbasedAuthentication            yes
-		HostbasedUsesNameFromPacketOnly    yes
+		#HostbasedUsesNameFromPacketOnly    yes
-		PubkeyAuthentication               yes
+		PubkeyAuthentication               no
		PasswordAuthentication             no
		...

I already have the server's key in the known hosts file on the client.

@ client

	cat ssh_config
		...
		GlobalKnownHostsFile /usr/local/etc/ssh/ssh_known_hosts
		UserKnownHostsFile   /usr/local/etc/ssh/ssh_known_hosts
		...

	ssh-keyscan -t ed25519 server.DOMAIN.COM >>
/usr/local/etc/ssh/ssh_known_hosts

and @server

	ssh-keyscan -t ed25519 client.DOMAIN.COM >>
/usr/local/etc/ssh/ssh_known_hosts

with all of the above, the hostbased auth connnect still fails just as before,

	ssh server.DOMAIN.COM
		...
		Permission denied (hostbased).

grantksupport at operamail.com

2015-Jan-09 21:00 UTC

head link

OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

Hi

On Fri, Jan 9, 2015, at 12:34 PM, Mark Hahn wrote:> >> The one you are missing is EnableSSHKeysign.
> 
> I suppose it's worth asking: is your ssh-keysign suid root
> (and are the permissions on your host keys sufficiently tight)?
Note that everything works correctly with other auth methods: pubkey, password,
...
I suspect key perms issues would've come up there.

Here's also the ssk-keysign perms

	client

		ls -al /usr/local/libexec/ssh-keysign
			-rwsr-xr-x+ 1 root root 459K Oct 11 06:51 /usr/local/libexec/ssh-keysign*

		ls -al /usr/local/etc/ssh/ssh.client.ed25519*
			-rw-------+ 1 root root 517 May  9  2014
/usr/local/etc/ssh/ssh.client.ed25519
			-rw-r--r--+ 1 root root 107 May  9  2014
/usr/local/etc/ssh/ssh.client.ed25519.pub


	server

		ls -al /usr/local/libexec/ssh-keysign
			-rwsr-xr-x+ 1 root root 455K Oct 11 06:51 /usr/local/libexec/ssh-keysign*

		ls -al /usr/local/etc/ssh/ssh.server.ed25519*
			-rw-------+ 1 root root 464 May 10  2014
/usr/local/etc/ssh/ssh.server.ed25519
			-rw-r--r--+ 1 root root 107 May 10  2014
/usr/local/etc/ssh/ssh.server.ed25519.pub

> > 	ssh-keyscan -t ed25519 server.DOMAIN.COM >>
/usr/local/etc/ssh/ssh_known_hosts
> 
> fine, though it's worth verifying that these are the files being used
> by the (non-default, right) sshd and ssh (client) that you're using.
i have

	@ server

	which sshd
		/usr/local/sbin/sshd

	systemctl status sshd
		sshd.service - OpenSSH Daemon
		   Loaded: loaded (/etc/systemd/system/sshd.service; enabled)
		   Active: active (running) since Fri 2015-01-09 12:57:12 PST; 2s ago
		 Main PID: 21534 (sshd)
		   CGroup: /system.slice/sshd.service
		           ?? 4662 sshd: root at pts/0
		           ?? 4664 -bash
		           ??21534 /usr/local/sbin/sshd -D -f /usr/local/etc/ssh/sshd_config
		           ??21541 systemctl status sshd

	ps ax | grep sshd_config
		20989 ?        Ss     0:00 /usr/local/sbin/sshd -D -f
/usr/local/etc/ssh/sshd_config

and

	@ client

		which ssh
			/usr/local/bin/ssh

		ssh server.DOMAIN.COM -vvv
			...
			debug3: load_hostkeys: loading entries for host "server.DOMAIN.COM"
from file "/usr/local/etc/ssh/ssh_known_hosts"
			debug3: load_hostkeys: found key type ED25519 in file
/usr/local/etc/ssh/ssh_known_hosts:2
			debug3: load_hostkeys: loaded 1 keys
			debug3: load_hostkeys: loading entries for host "server.DOMAIN.COM"
from file "/usr/local/etc/ssh/ssh_known_hosts"
			debug3: load_hostkeys: found key type ED25519 in file
/usr/local/etc/ssh/ssh_known_hosts:2
			debug3: load_hostkeys: loaded 1 keys
			...
> > 		Permission denied (hostbased).

Iain Morgan

2015-Jan-09 22:26 UTC

head link

OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

On Fri, Jan 09, 2015 at 13:00:10 -0800, grantksupport at operamail.com
wrote:> Hi
> 
> On Fri, Jan 9, 2015, at 12:34 PM, Mark Hahn wrote:
> > >> The one you are missing is EnableSSHKeysign.
> > 
> > I suppose it's worth asking: is your ssh-keysign suid root
> > (and are the permissions on your host keys sufficiently tight)?
> 
> Note that everything works correctly with other auth methods: pubkey,
password, ...
> I suspect key perms issues would've come up there.
Not so, only hostbased authentication uses the client's host keys, and
it is likewise the only method that uses ssh-keysign. Further,
ssh-keysign is only used for non-root users.
> 
> Here's also the ssk-keysign perms
> 
> 	client
> 
> 		ls -al /usr/local/libexec/ssh-keysign
> 			-rwsr-xr-x+ 1 root root 459K Oct 11 06:51
/usr/local/libexec/ssh-keysign*
> 
> 		ls -al /usr/local/etc/ssh/ssh.client.ed25519*
> 			-rw-------+ 1 root root 517 May  9  2014
/usr/local/etc/ssh/ssh.client.ed25519
> 			-rw-r--r--+ 1 root root 107 May  9  2014
/usr/local/etc/ssh/ssh.client.ed25519.pub
> 
Err, those _should_ be ssh_host_ed25519 and
ssh_host_ed25519.pub.> 
> 	server
> 
> 		ls -al /usr/local/libexec/ssh-keysign
> 			-rwsr-xr-x+ 1 root root 455K Oct 11 06:51
/usr/local/libexec/ssh-keysign*
> 
> 		ls -al /usr/local/etc/ssh/ssh.server.ed25519*
> 			-rw-------+ 1 root root 464 May 10  2014
/usr/local/etc/ssh/ssh.server.ed25519
> 			-rw-r--r--+ 1 root root 107 May 10  2014
/usr/local/etc/ssh/ssh.server.ed25519.pub
> 
Renaming the keys in your output only serves to complicate matters for
those who are taking time to try to help you. Further, ssh-keysign plays
no role on the server and the server's keys are not a factor in the
problem you are facing.> 
> > > 	ssh-keyscan -t ed25519 server.DOMAIN.COM >>
/usr/local/etc/ssh/ssh_known_hosts
> > 
> > fine, though it's worth verifying that these are the files being
used
> > by the (non-default, right) sshd and ssh (client) that you're
using.
> 
> i have
> 
> 	@ server
> 
> 	which sshd
> 		/usr/local/sbin/sshd
> 
> 	systemctl status sshd
> 		sshd.service - OpenSSH Daemon
> 		   Loaded: loaded (/etc/systemd/system/sshd.service; enabled)
> 		   Active: active (running) since Fri 2015-01-09 12:57:12 PST; 2s ago
> 		 Main PID: 21534 (sshd)
> 		   CGroup: /system.slice/sshd.service
> 		           ?? 4662 sshd: root at pts/0
> 		           ?? 4664 -bash
> 		           ??21534 /usr/local/sbin/sshd -D -f
/usr/local/etc/ssh/sshd_config
> 		           ??21541 systemctl status sshd
> 
> 	ps ax | grep sshd_config
> 		20989 ?        Ss     0:00 /usr/local/sbin/sshd -D -f
/usr/local/etc/ssh/sshd_config
> 
> and
> 
> 	@ client
> 
> 		which ssh
> 			/usr/local/bin/ssh
> 
> 		ssh server.DOMAIN.COM -vvv
> 			...
> 			debug3: load_hostkeys: loading entries for host
"server.DOMAIN.COM" from file
"/usr/local/etc/ssh/ssh_known_hosts"
> 			debug3: load_hostkeys: found key type ED25519 in file
/usr/local/etc/ssh/ssh_known_hosts:2
> 			debug3: load_hostkeys: loaded 1 keys
> 			debug3: load_hostkeys: loading entries for host
"server.DOMAIN.COM" from file
"/usr/local/etc/ssh/ssh_known_hosts"
> 			debug3: load_hostkeys: found key type ED25519 in file
/usr/local/etc/ssh/ssh_known_hosts:2
> 			debug3: load_hostkeys: loaded 1 keys
> 			...
> 
> > > 		Permission denied (hostbased).
> 
> _______________________________________________
> openssh-unix-dev mailing list
> openssh-unix-dev at mindrot.org
> https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
-- 
Iain Morgan

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