Hello Niklas, Thank you for taking the time to file a bug report.
While the symptoms experienced here seem similar to the ones reported in https://bugzilla.redhat.com/show_bug.cgi?id=1162620, the patch that fixed the latter is present in the version of the package for which you reported the issue. Therefore, would you mind providing additional information, such as configuration files? More importantly, we would be interested in a reproducer for the issue. Can you reproduce it without using ansible? Since there is not enough information in your report to begin triage or to differentiate between a local configuration problem and a bug in Ubuntu, I am marking this bug as "Incomplete". We would be grateful if you would: provide a more complete description of the problem, explain why you believe this is a bug in Ubuntu rather than a problem specific to your system, and then change the bug status back to "New". For local configuration issues, you can find assistance here: http://www.ubuntu.com/support/communit ** Bug watch added: Red Hat Bugzilla #1162620 https://bugzilla.redhat.com/show_bug.cgi?id=1162620 ** Changed in: openssh (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1938144 Title: monitor_read: unpermitted request 48 on server while attempting GSSAPI key exchange Status in openssh package in Ubuntu: Incomplete Bug description: I'm using openssh 1:8.2p1-4ubuntu0.2 on Ubuntu 20.04.2 LTS (client and server) with the option "GSSAPIKeyExchange=yes", and this causes the connection to fail. The server has GSSAPI (Kerberos authentication) enabled, but is is only used for non-root users (root uses SSH keys). Client command: ssh -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex root@server -v -p 2222 -o GSSAPIKeyExchange=yes Client log: OpenSSH_8.2p1 Ubuntu-4ubuntu0.2, OpenSSL 1.1.1f 31 Mar 2020 debug1: Reading configuration data /home/user/.ssh/config debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files debug1: /etc/ssh/ssh_config line 21: Applying options for * debug1: Connecting to compute-test [130.75.80.46] port 2222. debug1: Connection established. debug1: identity file /home/rother/.ssh/id_rsa type 0 debug1: identity file /home/rother/.ssh/id_rsa-cert type -1 debug1: identity file /home/rother/.ssh/id_dsa type -1 debug1: identity file /home/rother/.ssh/id_dsa-cert type -1 debug1: identity file /home/rother/.ssh/id_ecdsa type -1 debug1: identity file /home/rother/.ssh/id_ecdsa-cert type -1 debug1: identity file /home/rother/.ssh/id_ecdsa_sk type -1 debug1: identity file /home/rother/.ssh/id_ecdsa_sk-cert type -1 debug1: identity file /home/rother/.ssh/id_ed25519 type -1 debug1: identity file /home/rother/.ssh/id_ed25519-cert type -1 debug1: identity file /home/rother/.ssh/id_ed25519_sk type -1 debug1: identity file /home/rother/.ssh/id_ed25519_sk-cert type -1 debug1: identity file /home/rother/.ssh/id_xmss type -1 debug1: identity file /home/rother/.ssh/id_xmss-cert type -1 debug1: Local version string SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.2 debug1: Remote protocol version 2.0, remote software version OpenSSH_8.2p1 Ubuntu-4ubuntu0.2 debug1: match: OpenSSH_8.2p1 Ubuntu-4ubuntu0.2 pat OpenSSH* compat 0x04000000 debug1: Authenticating to server:2222 as 'root' debug1: Offering GSSAPI proposal: gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-gex-sha1-eipGX3TCiQSrx573bT1o1Q==,gss-group14-sha1-eipGX3TCiQSrx573bT1o1Q== debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: algorithm: gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g== debug1: kex: host key algorithm: ecdsa-sha2-nistp256 debug1: kex: server->client cipher: chacha20-poly1...@openssh.com MAC: <implicit> compression: none debug1: kex: client->server cipher: chacha20-poly1...@openssh.com MAC: <implicit> compression: none debug1: Doing group exchange debug1: Calling gss_init_sec_context debug1: Delegating credentials debug1: Received GSSAPI_COMPLETE debug1: Calling gss_init_sec_context debug1: Delegating credentials debug1: Rekey has happened - updating saved versions debug1: rekey out after 134217728 blocks debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: rekey in after 134217728 blocks debug1: Will attempt key: /home/rother/.ssh/id_rsa RSA SHA256:n/EY/cGjgd/r+7JpuqODxIotHHLsYptGXYx9GlKCWSM agent debug1: Will attempt key: /home/rother/.ssh/root_id_rsa RSA SHA256:yCLAID9FMILharHmDpCB8wW8eiA+iHa4oQKLODbbzKw agent debug1: Will attempt key: /home/user/.ssh/id_dsa debug1: Will attempt key: /home/user/.ssh/id_ecdsa debug1: Will attempt key: /home/user/.ssh/id_ecdsa_sk debug1: Will attempt key: /home/user/.ssh/id_ed25519 debug1: Will attempt key: /home/user/.ssh/id_ed25519_sk debug1: Will attempt key: /home/user/.ssh/id_xmss debug1: SSH2_MSG_EXT_INFO received debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,sk-ssh-ed25...@openssh.com,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp...@openssh.com> debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: gssapi-with-mic debug1: Delegating credentials debug1: Delegating credentials debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: gssapi-keyex Connection closed by 1.2.3.4 port 2222 Server log: debug1: sshd version OpenSSH_8.2, OpenSSL 1.1.1f 31 Mar 2020 debug1: private host key #0: ssh-rsa SHA256:REDACTED debug1: private host key #1: ecdsa-sha2-nistp256 SHA256:REDACTED debug1: private host key #2: ssh-ed25519 SHA256:REDACTED debug1: rexec_argv[0]='/usr/sbin/sshd' debug1: rexec_argv[1]='-d' debug1: rexec_argv[2]='-p' debug1: rexec_argv[3]='2222' debug1: Set /proc/self/oom_score_adj from 0 to -1000 debug1: Bind to port 2222 on 0.0.0.0. Server listening on 0.0.0.0 port 2222. debug1: Bind to port 2222 on ::. Server listening on :: port 2222. debug1: Server will not fork when running in debugging mode. debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8 debug1: sshd version OpenSSH_8.2, OpenSSL 1.1.1f 31 Mar 2020 debug1: private host key #0: ssh-rsa SHA256:REDACTED debug1: private host key #1: ecdsa-sha2-nistp256 SHA256:REDACTED debug1: private host key #2: ssh-ed25519 SHA256:REDACTED debug1: inetd sockets after dupping: 3, 3 Connection from 1.2.3.5 port 53724 on 1.2.3.4 port 2222 rdomain "" debug1: Local version string SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.2 debug1: Remote protocol version 2.0, remote software version OpenSSH_8.2p1 Ubuntu-4ubuntu0.2 debug1: match: OpenSSH_8.2p1 Ubuntu-4ubuntu0.2 pat OpenSSH* compat 0x04000000 debug1: permanently_set_uid: 111/65534 [preauth] debug1: list_hostkey_types: rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519 [preauth] debug1: SSH2_MSG_KEXINIT sent [preauth] debug1: SSH2_MSG_KEXINIT received [preauth] debug1: kex: algorithm: gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g== [preauth] debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth] debug1: kex: client->server cipher: chacha20-poly1...@openssh.com MAC: <implicit> compression: none [preauth] debug1: kex: server->client cipher: chacha20-poly1...@openssh.com MAC: <implicit> compression: none [preauth] debug1: Doing group exchange [preauth] debug1: Wait SSH2_MSG_GSSAPI_INIT [preauth] debug1: Received some client credentials debug1: rekey out after 134217728 blocks [preauth] debug1: SSH2_MSG_NEWKEYS sent [preauth] debug1: Sending SSH2_MSG_EXT_INFO [preauth] debug1: expecting SSH2_MSG_NEWKEYS [preauth] debug1: SSH2_MSG_NEWKEYS received [preauth] debug1: rekey in after 134217728 blocks [preauth] debug1: KEX done [preauth] debug1: userauth-request for user root service ssh-connection method none [preauth] debug1: attempt 0 failures 0 [preauth] debug1: PAM: initializing for "root" debug1: PAM: setting PAM_RHOST to "1.2.3.5" debug1: PAM: setting PAM_TTY to "ssh" debug1: userauth-request for user root service ssh-connection method gssapi-with-mic [preauth] debug1: attempt 1 failures 0 [preauth] Postponed gssapi-with-mic for root from 1.2.3.5 port 53724 ssh2 [preauth] debug1: Received some client credentials Failed gssapi-with-mic for root from 1.2.3.5 port 53724 ssh2 debug1: userauth-request for user root service ssh-connection method gssapi-with-mic [preauth] debug1: attempt 2 failures 1 [preauth] debug1: userauth-request for user root service ssh-connection method gssapi-keyex [preauth] debug1: attempt 3 failures 1 [preauth] monitor_read: unpermitted request 48 debug1: do_cleanup debug1: PAM: cleanup debug1: Killing privsep child 5525 debug1: audit_event: unhandled event 12 The important line might be "monitor_read: unpermitted request 48" When disabling GSSAPIKeyExchange=yes, everything works as expected. This bug was discovered using Ansible, which uses "-o PreferredAuthentications=gssapi-with-mic,gssapi- keyex,hostbased,publickey" for it's ssh connections. A similar bugs was reported in RHEL 7: https://bugzilla.redhat.com/show_bug.cgi?id=1162620 Please let me know if you need any further information! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1938144/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
