[SSHD-1154] userauth_pubkey: unsupported public key algorithm: rsa-sha2-512

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Duplicate
• Affects Version/s: 2.6.0
• Fix Version/s: 2.7.0
• Assignee: Unassigned
• Reporter: UmaShankar Avagadda
• Created: 08/Apr/21 09:26
• Updated: 10/May/21 13:17
• Resolved: 09/Apr/21 07:01

Description

Environment details:

Server OS : CentOS release 6.9 (Final)

$ ssh -V

 

OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013

 

$ sshd -T

 

port 22
protocol 2
addressfamily any
listenaddress 0.0.0.0:22
listenaddress [::]:22
usepam yes
serverkeybits 1024
logingracetime 120
keyregenerationinterval 3600
x11displayoffset 10
maxauthtries 6
maxsessions 10
clientaliveinterval 0
clientalivecountmax 3
permitrootlogin yes
ignorerhosts yes
ignoreuserknownhosts no
rhostsrsaauthentication no
hostbasedauthentication no
hostbasedusesnamefrompacketonly no
rsaauthentication yes
pubkeyauthentication yes
kerberosauthentication no
kerberosorlocalpasswd yes
kerberosticketcleanup yes
gssapiauthentication yes
gssapikeyexchange no
gssapicleanupcredentials yes
gssapistrictacceptorcheck yes
gssapistorecredentialsonrekey no
gssapikexalgorithms gss-gex-sha1-,gss-group1-sha1-,gss-group14-sha1-
passwordauthentication yes
kbdinteractiveauthentication no
challengeresponseauthentication no
printmotd yes
printlastlog yes
x11forwarding yes
x11uselocalhost yes
strictmodes yes
tcpkeepalive yes
permitemptypasswords no
permituserenvironment no
uselogin no
compression delayed
gatewayports no
showpatchlevel no
usedns yes
allowtcpforwarding yes
allowagentforwarding yes
useprivilegeseparation yes
kerberosusekuserok yes
pidfile /var/run/sshd.pid
xauthlocation /usr/bin/xauth
ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[e-mail]
macs hmac-md5,hmac-sha1,[e-mail],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[e-mail],hmac-sha1-96,hmac-md5-96
kexalgorithms diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
banner none
authorizedkeysfile .ssh/authorized_keys
authorizedkeysfile2 .ssh/authorized_keys2
loglevel DEBUG
syslogfacility AUTHPRIV
hostkey /etc/ssh/ssh_host_rsa_key
hostkey /etc/ssh/ssh_host_dsa_key
acceptenv LANG
acceptenv LC_CTYPE
acceptenv LC_NUMERIC
acceptenv LC_TIME
acceptenv LC_COLLATE
acceptenv LC_MONETARY
acceptenv LC_MESSAGES
acceptenv LC_PAPER
acceptenv LC_NAME
acceptenv LC_ADDRESS
acceptenv LC_TELEPHONE
acceptenv LC_MEASUREMENT
acceptenv LC_IDENTIFICATION
acceptenv LC_ALL
acceptenv LANGUAGE
acceptenv XMODIFIERS
subsystem sftp /usr/libexec/openssh/sftp-server
maxstartups 10:30:100
permittunnel no
permitopen any

sshd-common : 2.6.0

sshd-core : 2.6.0

I am using Client protocol version 2.0; client software version APACHE-SSHD-2.6.0

I am trying to ssh my server(RHEL6) using APACHE-SSHD-2.6.0 using below code snippet.

 String send = "HOST:" + host + " " + command;
                InputStream inputStream = new ByteArrayInputStream(send.getBytes());
                SshClient client = SshClient.setUpDefaultClient();
                client.start();
                ConnectFuture cf = client.connect(username, host, port);
                try (ClientSession session = cf.verify().getSession();) {
                        session.addPublicKeyIdentity(loadKeypair(privateKey.getAbsolutePath()));
                        session.auth().verify(defaultTimeoutSeconds, TimeUnit.SECONDS);

This is working fine with RHEL8, Ubuntu14, Ubuntu16, Ubuntu18 but not working with RHEL6 and RHEL7, getting below exception. 

unsupported public key algorithm: rsa-sha2-512 in sshd log

 

Caused by: org.apache.sshd.common.SshException: No more authentication methods available
        at org.apache.sshd.common.future.AbstractSshFuture.verifyResult(AbstractSshFuture.java:126)
        at org.apache.sshd.client.future.DefaultAuthFuture.verify(DefaultAuthFuture.java:39)
        at org.apache.sshd.client.future.DefaultAuthFuture.verify(DefaultAuthFuture.java:32)
        at org.apache.sshd.common.future.VerifiableFuture.verify(VerifiableFuture.java:56)
        at com.zimbra.cs.rmgmt.RemoteManager.executeRemoteCommand(RemoteManager.java:170)
        at com.zimbra.cs.rmgmt.RemoteManager.execute(RemoteManager.java:147)
        ... 70 more
Caused by: org.apache.sshd.common.SshException: No more authentication methods available
        at org.apache.sshd.client.session.ClientUserAuthService.tryNext(ClientUserAuthService.java:342)
        at org.apache.sshd.client.session.ClientUserAuthService.processUserAuth(ClientUserAuthService.java:277)
        at org.apache.sshd.client.session.ClientUserAuthService.process(ClientUserAuthService.java:224)
        at org.apache.sshd.common.session.helpers.AbstractSession.doHandleMessage(AbstractSession.java:502)
        at org.apache.sshd.common.session.helpers.AbstractSession.handleMessage(AbstractSession.java:428)
        at org.apache.sshd.common.session.helpers.AbstractSession.decode(AbstractSession.java:1463)
        at org.apache.sshd.common.session.helpers.AbstractSession.messageReceived(AbstractSession.java:388)
        at org.apache.sshd.common.session.helpers.AbstractSessionIoHandler.messageReceived(AbstractSessionIoHandler.java:64)
        at org.apache.sshd.common.io.nio2.Nio2Session.handleReadCycleCompletion(Nio2Session.java:358)
        at org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:335)
        at org.apache.sshd.common.io.nio2.Nio2Session$1.onCompleted(Nio2Session.java:332)
        at org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:312)
        at org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
        at java.base/sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:127)
        at java.base/sun.nio.ch.Invoker$2.run(Invoker.java:219)
        at java.base/sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)

broken-relay2:# /usr/sbin/sshd -d
debug1: sshd version OpenSSH_5.3p1
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug1: read PEM private key done: type DSA
debug1: private host key: #1 type 2 DSA
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-d'
Set /proc/self/oom_score_adj from 0 to -1000
debug1: Bind to port 22 on 0.0.0.0.
Server listening on 0.0.0.0 port 22.
debug1: Bind to port 22 on ::.
Server listening on :: port 22.
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8
debug1: inetd sockets after dupping: 3, 3
Connection from X.X.X.X port 55874
debug1: Client protocol version 2.0; client software version APACHE-SSHD-2.6.0
debug1: no match: APACHE-SSHD-2.6.0
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: permanently_set_uid: 74/74
debug1: list_hostkey_types: ssh-rsa,ssh-dss
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: client->server aes128-ctr hmac-sha2-256 none
debug1: kex: server->client aes128-ctr hmac-sha2-256 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST received
debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT
debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: KEX done
debug1: userauth-request for user zimbra service ssh-connection method none
debug1: attempt 0 failures 0
debug1: PAM: initializing for "zimbra"
debug1: PAM: setting PAM_RHOST to "mail.example.com"
debug1: PAM: setting PAM_TTY to "ssh"
debug1: userauth-request for user zimbra service ssh-connection method publickey
debug1: attempt 1 failures 0
userauth_pubkey: unsupported public key algorithm: rsa-sha2-512
Connection closed by X.X.X.X
debug1: do_cleanup
debug1: do_cleanup
debug1: PAM: cleanup

I found 2 solutions.

Solution 1:

I upgraded ssh on RHEL6 , it's working fine now.

Before upgrade ssh version:

$ ssh -V

OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013

After upgrade ssh version:

$ ssh -V

OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017

Solution 2:

I changed the order of SignatureFactoriesNameList, it's working fine now.

Changed order of rsa-sha2-512, rsa-sha2-256, ssh-rsa

Actual order: 

[e-mail],[e-mail],[e-mail],[e-mail],[e-mail],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[e-mail],rsa-sha2-512,rsa-sha2-256,ssh-rsa

Changed order:

[e-mail],[e-mail],[e-mail],[e-mail],[e-mail],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[e-mail],ssh-rsa,rsa-sha2-512,rsa-sha2-256

 

SshClient client = SshClient.setUpDefaultClient();
client.setSignatureFactoriesNameList("[e-mail],[e-mail],[e-mail],[e-mail],[e-mail],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[e-mail],ssh-rsa,rsa-sha2-512,rsa-sha2-256");
	

Solution 1 is good but not acceptable in my case, we can't ask our customers to upgrade server/system packages to make compatible with Java SSH client.  

Please let me know the solution 2 is better approach or not, If not why and what are issues I am going to face it with this change. 

 

Issue Links

• duplicates: SSHD-1141 Implement server-sig-algs
• duplicates: SSHD-1105 Use all possible signatures for a public key type in public key authentication