Como fazer debug de conexões SSH
Quando se trabalha com SSH para gerenciar diversas estações de trabalho, ainda mais utilizando outros métodos de autenticação, se faz necessária uma ferramenta de debug do processo de conexão.
No próprio utilitário do SSH temos a opção -v que nos trás essa funcionalidade. É possível rastrear todo o processo de conexão com um outro equipamento.
Veja aqui o debug de uma conexão com uma máquina virtual que possuo.
$ ssh -v mmuller@192.168.25.14
Este foi o resultado (se atente a parte em negrito):
OpenSSH_7.5p1 Ubuntu-10ubuntu0.1, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 192.168.25.14 [192.168.25.14] port 22.
debug1: Connection established.
debug1: identity file /home/mateus/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.5p1 Ubuntu-10ubuntu0.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.25.14:22 as ‘mmuller’
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC:
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC:
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:vmHgmlutj9tCMH/6zTZOVDc2HTdLRLRgOo0TvQdOOmE
debug1: Host ‘192.168.25.14’ is known and matches the ECDSA host key.
debug1: Found key in /home/mateus/.ssh/known_hosts:3
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
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)
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/mateus/.ssh/id_rsa
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.25.14 ([192.168.25.14]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Sending environment.
debug1: Sending env LANG = pt_BR.UTF-8
Last login: Sun Feb 25 19:09:51 2018 from ubuntu17.home
Agora, vou mudar a chave pública na VM que estou acessando para forçar um erro e tentarmos identificá-lo:
$ ssh -v mmuller@192.168.25.14
Se atente novamente nas palavras em negrito:
OpenSSH_7.5p1 Ubuntu-10ubuntu0.1, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 192.168.25.14 [192.168.25.14] port 22.
debug1: Connection established.
debug1: identity file /home/mateus/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.5p1 Ubuntu-10ubuntu0.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.25.14:22 as ‘mmuller’
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC:
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC:
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:vmHgmlutj9tCMH/6zTZOVDc2HTdLRLRgOo0TvQdOOmE
debug1: Host ‘192.168.25.14’ is known and matches the ECDSA host key.
debug1: Found key in /home/mateus/.ssh/known_hosts:3
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
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)
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/mateus/.ssh/id_rsa
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Trying private key: /home/mateus/.ssh/id_dsa
debug1: Trying private key: /home/mateus/.ssh/id_ecdsa
debug1: Trying private key: /home/mateus/.ssh/id_ed25519
debug1: Next authentication method: password
mmuller@192.168.25.14’s password:
Veja que ele tentou autenticar utilizando a chave pública, o que não funcionou, e então alterou o modo de autenticação para password, me solicitando uma senha.
Ainda existem mais níveis de debug de conexões SSH que podem ser utilizados com as opções -vv (level 2) e -vvv (level 3).
$ ssh -vvv mmuller@192.168.25.14
OpenSSH_7.5p1 Ubuntu-10ubuntu0.1, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "192.168.25.14" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.25.14 [192.168.25.14] port 22.
debug1: Connection established.
debug1: identity file /home/mateus/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mateus/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.5p1 Ubuntu-10ubuntu0.1
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 192.168.25.14:22 as ‘mmuller’
debug3: hostkeys_foreach: reading file "/home/mateus/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/mateus/.ssh/known_hosts:3
debug3: load_hostkeys: loaded 1 keys from 192.168.25.14
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-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,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,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-ed25519,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,aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
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,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: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,cast128-cbc,3des-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,cast128-cbc,3des-cbc
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:
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC:
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:vmHgmlutj9tCMH/6zTZOVDc2HTdLRLRgOo0TvQdOOmE
debug3: hostkeys_foreach: reading file "/home/mateus/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/mateus/.ssh/known_hosts:3
debug3: load_hostkeys: loaded 1 keys from 192.168.25.14
debug1: Host ‘192.168.25.14’ is known and matches the ECDSA host key.
debug1: Found key in /home/mateus/.ssh/known_hosts:3
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/mateus/.ssh/id_rsa (0x560b6a357360), agent
debug2: key: /home/mateus/.ssh/id_dsa ((nil))
debug2: key: /home/mateus/.ssh/id_ecdsa ((nil))
debug2: key: /home/mateus/.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=
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 RSA public key: /home/mateus/.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:pnVXslIWlg9t/Es6JKx0pUx61PmgigZSFtK7lndGrRw
debug3: sign_and_send_pubkey: RSA SHA256:pnVXslIWlg9t/Es6JKx0pUx61PmgigZSFtK7lndGrRw
debug3: send packet: type 50
debug3: receive packet: type 52
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.25.14 ([192.168.25.14]:22).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting no-more-sessions@openssh.com
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug3: receive packet: type 91
debug2: callback start
debug2: fd 3 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x10
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug3: send packet: type 98
debug1: Sending environment.
debug3: Ignored env CLUTTER_IM_MODULE
debug3: Ignored env LS_COLORS
debug3: Ignored env LESSCLOSE
debug3: Ignored env XDG_MENU_PREFIX
debug1: Sending env LANG = pt_BR.UTF-8
debug2: channel 0: request env confirm 0
debug3: send packet: type 98
debug3: Ignored env DISPLAY
debug3: Ignored env GNOME_SHELL_SESSION_MODE
debug3: Ignored env COLORTERM
debug3: Ignored env USERNAME
debug3: Ignored env XDG_VTNR
debug3: Ignored env SSH_AUTH_SOCK
debug3: Ignored env MANDATORY_PATH
debug3: Ignored env XDG_SESSION_ID
debug3: Ignored env USER
debug3: Ignored env DESKTOP_SESSION
debug3: Ignored env QT4_IM_MODULE
debug3: Ignored env TEXTDOMAINDIR
debug3: Ignored env DEFAULTS_PATH
debug3: Ignored env PWD
debug3: Ignored env HOME
debug3: Ignored env JOURNAL_STREAM
debug3: Ignored env TEXTDOMAIN
debug3: Ignored env SSH_AGENT_PID
debug3: Ignored env QT_ACCESSIBILITY
debug3: Ignored env XDG_SESSION_TYPE
debug3: Ignored env XDG_DATA_DIRS
debug3: Ignored env XDG_SESSION_DESKTOP
debug3: Ignored env GJS_DEBUG_OUTPUT
debug3: Ignored env GTK_MODULES
debug3: Ignored env WINDOWPATH
debug3: Ignored env TERM
debug3: Ignored env SHELL
debug3: Ignored env VTE_VERSION
debug3: Ignored env QT_IM_MODULE
debug3: Ignored env XMODIFIERS
debug3: Ignored env IM_CONFIG_PHASE
debug3: Ignored env XDG_CURRENT_DESKTOP
debug3: Ignored env XDG_SEAT
debug3: Ignored env SHLVL
debug3: Ignored env LANGUAGE
debug3: Ignored env WINDOWID
debug3: Ignored env GDMSESSION
debug3: Ignored env GNOME_DESKTOP_SESSION_ID
debug3: Ignored env LOGNAME
debug3: Ignored env DBUS_SESSION_BUS_ADDRESS
debug3: Ignored env XDG_RUNTIME_DIR
debug3: Ignored env XAUTHORITY
debug3: Ignored env XDG_CONFIG_DIRS
debug3: Ignored env PATH
debug3: Ignored env GJS_DEBUG_TOPICS
debug3: Ignored env SESSION_MANAGER
debug3: Ignored env LESSOPEN
debug3: Ignored env GTK_IM_MODULE
debug3: Ignored env _
debug2: channel 0: request shell confirm 1
debug3: send packet: type 98
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Last login: Sun Feb 25 19:47:10 2018 from ubuntu17.home
Bom pessoal, esta foi a dica de hoje, um abraço!
Se tiver alguma dúvida ou sugestão de conteúdo, por favor, comente!