I have a problem when establishing an ssh session, either tunnel only (-N) or when starting a console. My client is 18.04.2 LTS and my server is CentOs 7. The behavior seems random
- Sometimes the session starts successfully
- Sometimes it hangs on : (debug2: we sent a publickey packet, wait for reply)
- Sometimes it hangs in : (debug3: send packet: type 50) after server accepts key
It is so frustrating and random. What could be wrong? The following is a sample of the output when it hangs on (send packet: type 50) after the server accepts key.
$ ssh -vvv
OpenSSH_7.6p1 Ubuntu-4ubuntu0.2, OpenSSL 1.0.2n 7 Dec 2017
debug1: Reading configuration data /home/parsa/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "XX.XX.XXX.XX" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to XX.XX.XXX.XX [XX.XX.XXX.XX] port 22.
debug1: Connection established.
debug1: identity file /home/parsa/.ssh/id_rsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/parsa/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to XX.XX.XXX.XX:22 as 'parsa'
debug3: hostkeys_foreach: reading file "/home/parsa/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/parsa/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from XX.XX.XXX.XX
debug3: order_hostkeyalgs: prefer hostkeyalgs: ,,,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ,,,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,,,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: ,aes128-ctr,aes192-ctr,aes256-ctr,,
debug2: ciphers stoc: ,aes128-ctr,aes192-ctr,aes256-ctr,,
debug2: MACs ctos: ,,,,,,,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: ,,,,,,,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: ,zlib,none
debug2: compression stoc: ,zlib,none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: ,aes128-ctr,aes192-ctr,aes256-ctr,,,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,cast128-cbc,3des-cbc
debug2: ciphers stoc: ,aes128-ctr,aes192-ctr,aes256-ctr,,,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,cast128-cbc,3des-cbc
debug2: MACs ctos: ,,,,,,,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: ,,,,,,,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,
debug2: compression stoc: none,
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: MAC: <implicit> compression:
debug1: kex: client->server cipher: MAC: <implicit> compression:
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:PGifCzsbbBFaBbm3E2N7fQA70iyUO/mHGz5HQzPd3wc
debug3: hostkeys_foreach: reading file "/home/parsa/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/parsa/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from XX.XX.XXX.XX
debug1: Host 'XX.XX.XXX.XX' is known and matches the ECDSA host key.
debug1: Found key in /home/parsa/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /home/parsa/.ssh/id_rsa (0x55a63fd78630), agent
debug2: key: /home/parsa/.ssh/id_dsa ((nil))
debug2: key: /home/parsa/.ssh/id_ecdsa ((nil))
debug2: key: /home/parsa/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic,password
debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup gssapi-keyex
debug3: remaining preferred: gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-keyex
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug2: we did not send a packet, disable method
debug3: authmethod_lookup gssapi-with-mic
debug3: remaining preferred: publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-with-mic
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure. Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_1000)
debug1: Unspecified GSS failure. Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_1000)
debug2: we did not send a packet, disable method
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:UmGbR0Po40l31qILYVQKTslfHxbbzXXUHU7/JPi/Fy4 /home/parsa/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug2: input_userauth_pk_ok: fp SHA256:UmGbR0Po40l31qILYVQKTslfHxbbzXXUHU7/JPi/Fy4
debug3: sign_and_send_pubkey: RSA SHA256:UmGbR0Po40l31qILYVQKTslfHxbbzXXUHU7/JPi/Fy4
debug3: send packet: type 50
