Do LINUX VMs on Azure require any special configuration for ssh public key pair login?

Question

I went through the regular public key-pair login sequence on an Azure VM.

I copied my id_rsa.pub from the client machine to ~/.ssh/authorized_keys on LINUX vm running on Azure. Made sure that:

1. chmod 700 ~/.ssh (on server)
2. chmod 500 ~/.ssh/authorized_keys (on server)
3. chmod 700 ~/.ssh (on client)
4. chmod 500 ~/.ssh/id_rsa (on client)

Yet when I try to login to the server, I get the following verbose output when I try to connect:

OpenSSH_7.3p1, LibreSSL 2.4.1
debug1: Reading configuration data /Users/johnsmith/.ssh/config
debug1: /Users/johnsmith/.ssh/config line 5: Applying options for tmaa
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 20: Applying options for *
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Connecting to 13.80.231.101 [13.80.231.101] port 22.
debug1: Connection established.
debug1: identity file /Users/johnsmith/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/johnsmith/.ssh/id_rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1
debug1: match: OpenSSH_6.6.1 pat OpenSSH_6.6.1* compat 0x04000000
debug1: Authenticating to 13.80.231.101:22 as 'appliedai'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2Me2OBl/WHx3/z3C2QtFqRf1Ra19O1ZPgHnSHcBR4eg
debug1: Host '13.80.231.101' is known and matches the ECDSA host key.
debug1: Found key in /Users/johnsmith/.ssh/known_hosts:45
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/johnsmith/.ssh/id_rsa
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug1: No more authentication methods to try.
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

NOTE 1: my client SSH setup works fine for Amazon EC2 instances.

NOTE 2: my SELinux file labels on the server are:

ls -Z .ssh .ssh/authroized_keys 
-r-x------. appliedai appliedai unconfined_u:object_r:ssh_home_t:s0 .ssh/authroized_keys

.ssh:
-r-x------. appliedai appliedai unconfined_u:object_r:ssh_home_t:s0 authroized_keys

NOTE 3, the tail -f of /var/secure give me one incremental line:

Feb 27 12:03:43 machinelearningmachine sshd[9807]: Connection closed by 142.255.111.222 [preauth]

NOTE 4, my sshd config with comments removed looks like:

cat /etc/ssh/sshd_config 

HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
SyslogFacility AUTHPRIV
AuthorizedKeysFile  .ssh/authorized_keys
PasswordAuthentication no
ChallengeResponseAuthentication no
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
UsePAM yes
X11Forwarding yes
UsePrivilegeSeparation sandbox      # Default for new installations.
ClientAliveInterval 180
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS
Subsystem   sftp    /usr/libexec/openssh/sftp-server

NOTE 5: DEBUG3 level diags below:

Feb 27 12:25:17 mlm sshd[10027]: debug3: monitor_read: checking request 124
Feb 27 12:25:17 mlm sshd[10027]: debug3: mm_request_receive entering
Feb 27 12:25:17 mlm sshd[10027]: debug3: monitor_read: checking request 122
Feb 27 12:25:17 mlm sshd[10027]: debug3: mm_request_send entering: type 123
Feb 27 12:25:17 mlm sshd[10027]: debug1: monitor_read_log: child log fd closed
Feb 27 12:25:17 mlm sshd[10027]: debug3: mm_request_receive entering
Feb 27 12:25:17 mlm sshd[10027]: debug1: do_cleanup
Feb 27 12:25:17 mlm sshd[10027]: debug1: PAM: cleanup
Feb 27 12:25:17 mlm sshd[10027]: debug3: PAM: sshpam_thread_cleanup entering
Feb 27 12:25:17 mlm sshd[10027]: debug1: Killing privsep child 10028
Feb 27 12:25:29 mlm sshd[10003]: debug3: fd 5 is not O_NONBLOCK
Feb 27 12:25:29 mlm sshd[10003]: debug1: Forked child 10031.
Feb 27 12:25:29 mlm sshd[10003]: debug3: send_rexec_state: entering fd = 8 config len 780
Feb 27 12:25:29 mlm sshd[10003]: debug3: ssh_msg_send: type 0
Feb 27 12:25:29 mlm sshd[10003]: debug3: send_rexec_state: done
Feb 27 12:25:29 mlm sshd[10031]: debug3: oom_adjust_restore
Feb 27 12:25:29 mlm sshd[10031]: Set /proc/self/oom_score_adj to 0
Feb 27 12:25:29 mlm sshd[10031]: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8
Feb 27 12:25:29 mlm sshd[10031]: debug1: inetd sockets after dupping: 3, 3
Feb 27 12:25:29 mlm sshd[10031]: Connection from 142.255.93.140 port 64851 on 10.0.0.4 port 22
Feb 27 12:25:29 mlm sshd[10031]: debug1: Client protocol version 2.0; client software version OpenSSH_7.3
Feb 27 12:25:29 mlm sshd[10031]: debug1: match: OpenSSH_7.3 pat OpenSSH* compat 0x04000000
Feb 27 12:25:29 mlm sshd[10031]: debug1: Enabling compatibility mode for protocol 2.0
Feb 27 12:25:29 mlm sshd[10031]: debug1: Local version string SSH-2.0-OpenSSH_6.6.1
Feb 27 12:25:29 mlm sshd[10031]: debug2: fd 3 setting O_NONBLOCK
Feb 27 12:25:29 mlm sshd[10031]: debug3: ssh_sandbox_init: preparing rlimit sandbox
Feb 27 12:25:29 mlm sshd[10031]: debug2: Network child is on pid 10032
Feb 27 12:25:29 mlm sshd[10031]: debug3: preauth child monitor started
Feb 27 12:25:29 mlm sshd[10031]: debug1: SELinux support enabled [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: ssh_selinux_change_context: setting context from 'system_u:system_r:sshd_t:s0-s0:c0.c1023' to 'system_u:system_r:sshd_net_t:s0-s0:c0.c1023' [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: privsep user:group 74:74 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: permanently_set_uid: 74/74 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: list_hostkey_types: ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: SSH2_MSG_KEXINIT sent [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: SSH2_MSG_KEXINIT received [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: none,[email protected] [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: none,[email protected] [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit:  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit:  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: reserved 0  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],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 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: none,[email protected],zlib [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: none,[email protected],zlib [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit:  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit:  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_parse_kexinit: reserved 0  [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: kex: client->server [email protected] <implicit> none [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: kex: server->client [email protected] <implicit> none [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: kex: [email protected] need=64 dh_need=64 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 120 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive_expect entering: type 121 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 120
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 121
Feb 27 12:25:29 mlm sshd[10031]: debug1: kex: [email protected] need=64 dh_need=64 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 120 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive_expect entering: type 121 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 120
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 121
Feb 27 12:25:29 mlm sshd[10031]: debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_key_sign entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 6 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive_expect entering: type 7 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 6
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_sign
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_sign: signature 0x7f8d20faa430(100)
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 7
Feb 27 12:25:29 mlm sshd[10031]: debug2: monitor_read: 6 used once, disabling now
Feb 27 12:25:29 mlm sshd[10031]: debug2: kex_derive_keys [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: set_newkeys: mode 1 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: SSH2_MSG_NEWKEYS sent [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: expecting SSH2_MSG_NEWKEYS [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: set_newkeys: mode 0 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: SSH2_MSG_NEWKEYS received [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: KEX done [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: userauth-request for user johnsmith service ssh-connection method none [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: attempt 0 failures 0 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_getpwnamallow entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 8 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_getpwnamallow: waiting for MONITOR_ANS_PWNAM [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive_expect entering: type 9 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 8
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_pwnamallow
Feb 27 12:25:29 mlm sshd[10031]: debug3: Trying to reverse map address 142.255.93.140.
Feb 27 12:25:29 mlm sshd[10031]: debug2: parse_server_config: config reprocess config len 780
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_pwnamallow: sending MONITOR_ANS_PWNAM: 1
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 9
Feb 27 12:25:29 mlm sshd[10031]: debug2: monitor_read: 8 used once, disabling now
Feb 27 12:25:29 mlm sshd[10031]: debug2: input_userauth_request: setting up authctxt for johnsmith [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_start_pam entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 100 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_inform_authserv entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 4 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_inform_authrole entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 80 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: input_userauth_request: try method none [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: userauth_finish: failure partial=0 next methods="publickey,gssapi-keyex,gssapi-with-mic" [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 100
Feb 27 12:25:29 mlm sshd[10031]: debug1: PAM: initializing for "johnsmith"
Feb 27 12:25:29 mlm sshd[10031]: debug1: PAM: setting PAM_RHOST to "cpe-142-255-93-140.nyc.res.rr.com"
Feb 27 12:25:29 mlm sshd[10031]: debug1: PAM: setting PAM_TTY to "ssh"
Feb 27 12:25:29 mlm sshd[10031]: debug2: monitor_read: 100 used once, disabling now
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 4
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_authserv: service=ssh-connection, style=
Feb 27 12:25:29 mlm sshd[10031]: debug2: monitor_read: 4 used once, disabling now
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 80
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_authrole: role=
Feb 27 12:25:29 mlm sshd[10031]: debug2: monitor_read: 80 used once, disabling now
Feb 27 12:25:29 mlm sshd[10031]: debug1: userauth-request for user johnsmith service ssh-connection method publickey [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: attempt 1 failures 0 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug2: input_userauth_request: try method publickey [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: test whether pkalg/pkblob are acceptable [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_key_allowed entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 22 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_key_allowed: waiting for MONITOR_ANS_KEYALLOWED [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive_expect entering: type 23 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 22
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_keyallowed entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_keyallowed: key_from_blob: 0x7f8d20faa1d0
Feb 27 12:25:29 mlm sshd[10031]: debug1: temporarily_use_uid: 1002/1002 (e=0/0)
Feb 27 12:25:29 mlm sshd[10031]: debug1: trying public key file /home/johnsmith/.ssh/authorized_keys
Feb 27 12:25:29 mlm sshd[10031]: debug1: Could not open authorized keys '/home/johnsmith/.ssh/authorized_keys': No such file or directory
Feb 27 12:25:29 mlm sshd[10031]: debug1: restore_uid: 0/0
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_answer_keyallowed: key 0x7f8d20faa1d0 is not allowed
Feb 27 12:25:29 mlm sshd[10031]: Failed publickey for johnsmith from 142.255.93.140 port 64851 ssh2: RSA 1c:88:ac:d5:45:94:9f:1c:f0:1f:88:55:c2:53:f6:16
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 23
Feb 27 12:25:29 mlm sshd[10031]: debug2: userauth_pubkey: authenticated 0 pkalg ssh-rsa [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: userauth_finish: failure partial=0 next methods="publickey,gssapi-keyex,gssapi-with-mic" [preauth]
Feb 27 12:25:29 mlm sshd[10031]: Connection closed by 142.255.93.140 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug1: do_cleanup [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: PAM: sshpam_thread_cleanup entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 124 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 122 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive_expect entering: type 123 [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering [preauth]
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 124
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug3: monitor_read: checking request 122
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_send entering: type 123
Feb 27 12:25:29 mlm sshd[10031]: debug1: monitor_read_log: child log fd closed
Feb 27 12:25:29 mlm sshd[10031]: debug3: mm_request_receive entering
Feb 27 12:25:29 mlm sshd[10031]: debug1: do_cleanup
Feb 27 12:25:29 mlm sshd[10031]: debug1: PAM: cleanup
Feb 27 12:25:29 mlm sshd[10031]: debug3: PAM: sshpam_thread_cleanup entering
Feb 27 12:25:29 mlm sshd[10031]: debug1: Killing privsep child 10032

Answer 1

I guess now the error is obvious:

debug1: trying public key file /home/johnsmith/.ssh/authorized_keys
debug1: Could not open authorized keys '/home/johnsmith/.ssh/authorized_keys': No such file or directory

the file where sshd is expecting to find the authorized keys is not there for some reason. So either you are connecting as a different user, you wrote the public keys using different user or something similar.