Problem was repeated step-by-step inside virtual machine in VirtualBox: - Used the same key type ed25519 - Used the same Username which has success auth via password - User the same OpenSSH version from Optional Features UPD June 29 of 2021: log updated after using `FixHostFilePermissions.ps1` and `FixUserFilePermissions.ps1` scripts ```powershell PS C:\Users\VBOX> sshd -ddd -p 22324 debug2: load_server_config: filename __PROGRAMDATA__\\ssh/sshd_config debug2: load_server_config: done config len = 251 debug2: parse_server_config: config __PROGRAMDATA__\\ssh/sshd_config len 251 debug3: __PROGRAMDATA__\\ssh/sshd_config:38 setting AuthorizedKeysFile .ssh/authorized_keys debug3: __PROGRAMDATA__\\ssh/sshd_config:76 setting Subsystem sftp sftp-server.exe debug3: checking syntax for 'Match Group administrators' debug1: sshd version OpenSSH_for_Windows_7.7, LibreSSL 2.6.5 debug1: private host key #0: ssh-rsa SHA256:TvljyOWl57yvB0tL8u1EAUj1on3ijEalhsOvn31MZx4 debug1: private host key #1: ecdsa-sha2-nistp256 SHA256:jbvUqyL3tAVcsKqAXkPH2jmV7FbAgroeneGHgZvjJK4 debug1: private host key #2: ssh-ed25519 SHA256:h/qb6crILgFwx1wqFX4sc/2cbI+ee8m4LebrlJbCFRQ debug1: rexec_argv[0]='C:\\Windows\\System32\\OpenSSH\\sshd.exe' debug1: rexec_argv[1]='-ddd' debug1: rexec_argv[2]='-p' debug1: rexec_argv[3]='22324' debug2: fd 3 setting O_NONBLOCK debug3: sock_set_v6only: set socket 3 IPV6_V6ONLY debug1: Bind to port 22324 on ::. Server listening on :: port 22324. debug2: fd 4 setting O_NONBLOCK debug1: Bind to port 22324 on 0.0.0.0. Server listening on 0.0.0.0 port 22324. debug3: fd 5 is not O_NONBLOCK debug1: Server will not fork when running in debugging mode. debug3: send_rexec_state: entering fd = 8 config len 251 debug3: ssh_msg_send: type 0 debug3: send_rexec_state: done Connection from ::1 port 52320 on ::1 port 22324 debug1: Client protocol version 2.0; client software version OpenSSH_for_Windows_7.7 debug1: match: OpenSSH_for_Windows_7.7 pat OpenSSH* compat 0x04000000 debug1: Local version string SSH-2.0-OpenSSH_for_Windows_7.7 debug2: fd 5 setting O_NONBLOCK debug3: spawning "C:\\Windows\\System32\\OpenSSH\\sshd.exe" "-ddd" "-p" "22324" "-y" debug2: Network child is on pid 2252 debug3: send_rexec_state: entering fd = 4 config len 251 debug3: ssh_msg_send: type 0 debug3: send_rexec_state: done debug3: ssh_msg_send: type 0 debug3: ssh_msg_send: type 0 debug3: preauth child monitor started debug3: recv_rexec_state: entering fd = 3 debug3: ssh_msg_recv entering debug3: recv_rexec_state: done debug2: parse_server_config: config __PROGRAMDATA__\\ssh/sshd_config len 251 debug3: __PROGRAMDATA__\\ssh/sshd_config:38 setting AuthorizedKeysFile .ssh/authorized_keys debug3: __PROGRAMDATA__\\ssh/sshd_config:76 setting Subsystem sftp sftp-server.exe debug3: checking syntax for 'Match Group administrators' debug1: sshd version OpenSSH_for_Windows_7.7, LibreSSL 2.6.5 debug3: ssh_msg_recv entering debug3: ssh_msg_recv entering debug2: fd 5 setting O_NONBLOCK debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth] debug3: send packet: type 20 [preauth] debug1: SSH2_MSG_KEXINIT sent [preauth] debug3: receive packet: type 20 [preauth] debug1: SSH2_MSG_KEXINIT received [preauth] debug2: local server KEXINIT proposal [preauth] 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,diffie-hellman-group14-sha1 [preauth] debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth] debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com [preauth] debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com [preauth] 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 [preauth] 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 [preauth] debug2: compression ctos: none [preauth] debug2: compression stoc: none [preauth] debug2: languages ctos: [preauth] debug2: languages stoc: [preauth] debug2: first_kex_follows 0 [preauth] debug2: reserved 0 [preauth] debug2: peer client KEXINIT proposal [preauth] 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-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c [preauth] 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,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa [preauth] debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com [preauth] debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com [preauth] 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 [preauth] 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 [preauth] debug2: compression ctos: none [preauth] debug2: compression stoc: none [preauth] debug2: languages ctos: [preauth] debug2: languages stoc: [preauth] debug2: first_kex_follows 0 [preauth] debug2: reserved 0 [preauth] debug1: kex: algorithm: curve25519-sha256 [preauth] debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth] debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: compression: none [preauth] debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: compression: none [preauth] debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth] debug3: receive packet: type 30 [preauth] debug3: mm_key_sign entering [preauth] debug3: mm_request_send entering: type 6 [preauth] debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN [preauth] debug3: mm_request_receive_expect entering: type 7 [preauth] debug3: mm_request_receive entering [preauth] debug3: mm_request_receive entering debug3: monitor_read: checking request 6 debug3: mm_answer_sign debug3: mm_answer_sign: hostkey proof signature 02A21A38(100) debug3: mm_request_send entering: type 7 debug2: monitor_read: 6 used once, disabling now debug3: send packet: type 31 [preauth] debug3: send packet: type 21 [preauth] debug2: set_newkeys: mode 1 [preauth] debug1: rekey after 134217728 blocks [preauth] debug1: SSH2_MSG_NEWKEYS sent [preauth] debug1: expecting SSH2_MSG_NEWKEYS [preauth] debug3: send packet: type 7 [preauth] debug3: receive packet: type 21 [preauth] debug1: SSH2_MSG_NEWKEYS received [preauth] debug2: set_newkeys: mode 0 [preauth] debug1: rekey after 134217728 blocks [preauth] debug1: KEX done [preauth] debug3: receive packet: type 5 [preauth] debug3: send packet: type 6 [preauth] debug3: receive packet: type 50 [preauth] debug1: userauth-request for user VBOX service ssh-connection method none [preauth] debug1: attempt 0 failures 0 [preauth] debug3: mm_getpwnamallow entering [preauth] debug3: mm_request_send entering: type 8 [preauth] debug3: mm_getpwnamallow: waiting for MONITOR_ANS_PWNAM [preauth] debug3: mm_request_receive_expect entering: type 9 [preauth] debug3: mm_request_receive entering [preauth] debug3: mm_request_receive entering debug3: monitor_read: checking request 8 debug3: mm_answer_pwnamallow debug2: parse_server_config: config reprocess config len 251 debug3: checking match for 'Group administrators' user vbox host ::1 addr ::1 laddr ::1 lport 22324 debug3: get_user_token - i am running as vbox, returning process token debug1: user matched group list administrators at line 84 debug3: match found debug3: reprocess config:85 setting AuthorizedKeysFile __PROGRAMDATA__/ssh/administrators_authorized_keys debug3: mm_answer_pwnamallow: sending MONITOR_ANS_PWNAM: 1 debug3: mm_request_send entering: type 9 debug2: monitor_read: 8 used once, disabling now debug2: input_userauth_request: setting up authctxt for VBOX [preauth] debug3: mm_inform_authserv entering [preauth] debug3: mm_request_send entering: type 4 [preauth] debug2: input_userauth_request: try method none [preauth] debug3: userauth_finish: failure partial=0 next methods="publickey,password,keyboard-interactive" [preauth] debug3: send packet: type 51 [preauth] debug3: mm_request_receive entering debug3: monitor_read: checking request 4 debug3: mm_answer_authserv: service=ssh-connection, style= debug2: monitor_read: 4 used once, disabling now debug3: receive packet: type 50 [preauth] debug1: userauth-request for user VBOX service ssh-connection method publickey [preauth] debug1: attempt 1 failures 0 [preauth] debug2: input_userauth_request: try method publickey [preauth] debug1: userauth_pubkey: test pkalg ssh-ed25519 pkblob ED25519 SHA256:Y/Jut0ibqUW9eflGB80oK2gxGsWxsvos/Op6hKtw3vg [preauth] debug3: mm_key_allowed entering [preauth] debug3: mm_request_send entering: type 22 [preauth] debug3: mm_key_allowed: waiting for MONITOR_ANS_KEYALLOWED [preauth] debug3: mm_request_receive_expect entering: type 23 [preauth] debug3: mm_request_receive entering [preauth] debug3: mm_request_receive entering debug3: monitor_read: checking request 22 debug3: mm_answer_keyallowed entering debug3: mm_answer_keyallowed: key_from_blob: 029C94A0 debug1: trying public key file __PROGRAMDATA__/ssh/administrators_authorized_keys debug1: read_keyfile_line: __PROGRAMDATA__/ssh/administrators_authorized_keys line 1 exceeds size limit debug3: mm_answer_keyallowed: publickey authentication test: ED25519 key is not allowed Failed publickey for VBOX from ::1 port 52320 ssh2: ED25519 SHA256:Y/Jut0ibqUW9eflGB80oK2gxGsWxsvos/Op6hKtw3vg debug3: mm_request_send entering: type 23 debug2: userauth_pubkey: authenticated 0 pkalg ssh-ed25519 [preauth] debug3: userauth_finish: failure partial=0 next methods="publickey,password,keyboard-interactive" [preauth] debug3: send packet: type 51 [preauth] debug3: receive packet: type 50 [preauth] debug1: userauth-request for user VBOX service ssh-connection method keyboard-interactive [preauth] debug1: attempt 2 failures 1 [preauth] debug2: input_userauth_request: try method keyboard-interactive [preauth] debug1: keyboard-interactive devs [preauth] debug1: auth2_challenge: user=VBOX devs= [preauth] debug1: kbdint_alloc: devices '' [preauth] debug2: auth2_challenge_start: devices [preauth] debug3: userauth_finish: failure partial=0 next methods="publickey,password,keyboard-interactive" [preauth] debug3: send packet: type 51 [preauth] debug3: recv - from CB ERROR:10054, io:02F0CDF0 [preauth] Connection reset by authenticating user VBOX ::1 port 52320 [preauth] debug1: do_cleanup [preauth] debug3: ReadFileEx() ERROR:109, io:02A219A0 debug1: monitor_read_log: child log fd closed debug3: mm_request_receive entering debug1: do_cleanup debug1: Killing privsep child 2252 ```