Having Trouble While Connecting AWS using ssh - linux

Question

I'm using ubuntu AWS instance it worked fine previously but today I tried to login using ssh but it keeps denying me
I also tried correcting permission of pem file chmod 400 and 600 and I checked user again ubuntu or not by connecting root it said
Please login as the user "ubuntu" rather than the user "root".
also tried ssh with sudo still not able to connect.
Here the verbose output while i'm connecting ssh -vvv -i {pemfile} ubuntu#{ip}
ssh -vvv -i "myfile.pem" ubuntu#ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com
OpenSSH_8.2p1 Ubuntu-4ubuntu0.5, OpenSSL 1.1.1f 31 Mar 2020
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 *
debug2: resolving "ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com" port 22
debug2: ssh_connect_direct
debug1: Connecting to ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com [13.xxx.xxx.xxx] port 22.
debug1: Connection established.
debug1: identity file myfile.pem type -1
debug1: identity file myfile.pem-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.5
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.9p1 Ubuntu-3
debug1: match: OpenSSH_8.9p1 Ubuntu-3 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com:22 as 'ubuntu'
debug3: hostkeys_foreach: reading file "/home/user/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/user/.ssh/known_hosts:40
debug3: load_hostkeys: loaded 1 keys from ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-cert-v01#openssh.com,ecdsa-sha2-nistp384-cert-v01#openssh.com,ecdsa-sha2-nistp521-cert-v01#openssh.com,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,curve25519-sha256#libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: ecdsa-sha2-nistp256-cert-v01#openssh.com,ecdsa-sha2-nistp384-cert-v01#openssh.com,ecdsa-sha2-nistp521-cert-v01#openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256-cert-v01#openssh.com,ssh-ed25519-cert-v01#openssh.com,sk-ssh-ed25519-cert-v01#openssh.com,rsa-sha2-512-cert-v01#openssh.com,rsa-sha2-256-cert-v01#openssh.com,ssh-rsa-cert-v01#openssh.com,sk-ecdsa-sha2-nistp256#openssh.com,ssh-ed25519,sk-ssh-ed25519#openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: chacha20-poly1305#openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm#openssh.com,aes256-gcm#openssh.com
debug2: ciphers stoc: chacha20-poly1305#openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm#openssh.com,aes256-gcm#openssh.com
debug2: MACs ctos: umac-64-etm#openssh.com,umac-128-etm#openssh.com,hmac-sha2-256-etm#openssh.com,hmac-sha2-512-etm#openssh.com,hmac-sha1-etm#openssh.com,umac-64#openssh.com,umac-128#openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm#openssh.com,umac-128-etm#openssh.com,hmac-sha2-256-etm#openssh.com,hmac-sha2-512-etm#openssh.com,hmac-sha1-etm#openssh.com,umac-64#openssh.com,umac-128#openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib#openssh.com,zlib
debug2: compression stoc: none,zlib#openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256#libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,sntrup761x25519-sha512#openssh.com,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256
debug2: host key algorithms: rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: chacha20-poly1305#openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm#openssh.com,aes256-gcm#openssh.com
debug2: ciphers stoc: chacha20-poly1305#openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm#openssh.com,aes256-gcm#openssh.com
debug2: MACs ctos: umac-64-etm#openssh.com,umac-128-etm#openssh.com,hmac-sha2-256-etm#openssh.com,hmac-sha2-512-etm#openssh.com,hmac-sha1-etm#openssh.com,umac-64#openssh.com,umac-128#openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm#openssh.com,umac-128-etm#openssh.com,hmac-sha2-256-etm#openssh.com,hmac-sha2-512-etm#openssh.com,hmac-sha1-etm#openssh.com,umac-64#openssh.com,umac-128#openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib#openssh.com
debug2: compression stoc: none,zlib#openssh.com
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: chacha20-poly1305#openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305#openssh.com MAC: <implicit> compression: none
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:kaOCGj+Dgbbm8LqMeci7YjRjl5zBYHDhgq173rGs9ZA
debug3: hostkeys_foreach: reading file "/home/user/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/user/.ssh/known_hosts:40
debug3: load_hostkeys: loaded 1 keys from ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com
debug3: hostkeys_foreach: reading file "/home/user/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/user/.ssh/known_hosts:41
debug3: load_hostkeys: loaded 1 keys from 13.xxx.xxx.xxx
debug1: Host 'ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com' is known and matches the ECDSA host key.
debug1: Found key in /home/user/.ssh/known_hosts:40
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey out 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 in after 134217728 blocks
debug1: Will attempt key: myfile.pem RSA SHA256:hQqliBUwEKzZ+ZCA/K9hIoODTG+Ao9IsDNp/ncSl7CM agent
debug1: Will attempt key: myfile.pem explicit
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,sk-ssh-ed25519#openssh.com,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256#openssh.com,webauthn-sk-ecdsa-sha2-nistp256#openssh.com>
debug1: kex_input_ext_info: publickey-hostbound#openssh.com (unrecognised)
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
debug3: start over, passed a different list publickey
debug3: preferred gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: myfile.pem RSA SHA256:hQqliBUwEKzZ+ZCA/K9hIoODTG+Ao9IsDNp/ncSl7CM agent
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug1: Trying private key: myfile.pem
debug3: sign_and_send_pubkey: RSA SHA256:hQqliBUwEKzZ+ZCA/K9hIoODTG+Ao9IsDNp/ncSl7CM
debug3: sign_and_send_pubkey: signing using rsa-sha2-512 SHA256:hQqliBUwEKzZ+ZCA/K9hIoODTG+Ao9IsDNp/ncSl7CM
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
ubuntu#ec2-xx-xxx-xxx-xxx.ap-xxxx-1.compute.amazonaws.com: Permission denied (publickey).

Answer 1

Honestly it looks like your key is not accepted by the server as the client does not indicate any errors, simply that no other authentication methods are available.
I don't have too much experience with AWS but I would suggest checking the /var/log/auth.log file on the server.
That will probably shed some light on why the key is not allowed on the machine.
Also worth checking is the ˜/.ssh/authorized_keys file on the server so you can compare the keys.
Perhaps the permissions on this file are too open.
With the logging you provided there is not much left but to guess.

Answer 2

I solved with myself with different method
here what i done.
Instances -> Open Your Instance -> Action -> Monitor and Troubleshoot -> EC2 Serial Console -> now enable if not enabled -> connect
or
EC2 Instance Connect Method
it will open new tab with ssh you can login using ubuntu or other user and with the password you used
after logined inside
$ sudo nano /etc/ssh/sshd_config
or
$ sudo vi /etc/ssh/sshd_config
Replace this lines
UsePAM yes
IgnoreUserKnownHosts no
PasswordAuthentication no
With these modification
UsePAM no
IgnoreUserKnownHosts no
PasswordAuthentication yes
save the file and restart ssh service
$ sudo systemctl restart ssh
after that you can login directly with
$ ssh ubuntu#<ip>
and enter password that's all.
There is other methods like changing the authorized_keys or change the pubic keys with yours