Estou tentando configurar um ambiente Kerberos simples, que consiste em um servidor Kerberos (KDC), uma máquina cliente e uma máquina servidor executando um daemon OpenSSH. O cliente deve ser autenticado através do Kerberos ao estabelecer uma conexão SSH com a máquina do servidor.
O nome do usuário do Kerberos que estou tentando autenticar é krbuser . Este usuário existe na máquina de serviço e tem um fluxo de 1001 .
O estranho é que eu preciso digitar a senha do usuário Kerberos ao fazer o login com o SSH. Toda vez que eu faço login. Não só pela minha primeira conexão. Isso parece estranho porque o objetivo do Kerberos é autenticar sem uma senha.
Eu peguei um tcpdump durante o processo de autenticação e notei que o cliente está fazendo AS-REQs para o KDC com cname root . Esse nome de usuário do Kerberos não e eu tenho não idéia do motivo pelo qual o cliente está usando esse nome. Como esperado, o KDC responde com uma mensagem eRR-C-PRINCIPAL-UNKNOWN , já que não há nenhum usuário root no banco de dados.
Para mim, parece que o principal problema é o fato de que o cliente tenta autenticar como root em vez de krbuser .
Vou postar algumas informações sobre minha configuração atual abaixo. Por favor, deixe-me saber se você precisar de alguma informação adicional.
No KDC:
/etc/krb5.conf
[logging]
default = FILE:/usr/local/krb5/var/log/krb5lib.log
kdc = FILE:/usr/local/krb5/var/log/krb5kdc.log
admin_server = FILE:/usr/local/krb5/var/log/kadmin.log
[libdefaults]
default_realm = metz.prac.os3.nl
rdns = false
# The following krb5.conf variables are only for MIT Kerberos.
krb4_config = /etc/krb.conf
krb4_realms = /etc/krb.realms
kdc_timesync = 1
ccache_type = 4
forwardable = true
proxiable = true
[realms]
metz.prac.os3.nl = {
kdc = krb-0.metz.prac.os3.nl
admin_server = krb-0.metz.prac.os3.nl
}
Na máquina de serviço:
/etc/ssh/sshd config (um extrato)
# Kerberos options
KerberosAuthentication yes
# KerberosGetAFSToken no
# KerberosOrLocalPasswd no
# KerberosTicketCleanup yes
# GSSAPI options
GSSAPIAuthentication yes
# GSSAPICleanupCredentials yes
Arquivos de log capturados durante a autenticação SSH:
debug1: rekey after 4294967296 blocks [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user root service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug1: PAM: initializing for "root"
debug1: PAM: setting PAM_RHOST to "218.65.30.30"
debug1: PAM: setting PAM_TTY to "ssh"
debug1: userauth-request for user root service ssh-connection method password [preauth]
debug1: attempt 1 failures 0 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: Client '[email protected]' not found in Kerberos database
debug1: krb5_cleanup_proc called
debug1: inetd sockets after dupping: 5, 5
Connection from 145.100.110.115 port 51946 on 145.100.110.116 port 22
debug1: Client protocol version 2.0; client software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.2 pat OpenSSH* compat 0x04000000
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: permanently_set_uid: 106/65534 [preauth]
debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: kex: algorithm: [email protected] [preauth]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth]
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none [preauth]
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none [preauth]
debug1: expecting SSH2_MSG_KEX_ECDH_INIT [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug1: rekey after 134217728 blocks [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user krbuser service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug1: PAM: initializing for "krbuser"
debug1: PAM: setting PAM_RHOST to "145.100.110.115"
debug1: PAM: setting PAM_TTY to "ssh"
debug1: userauth-request for user krbuser service ssh-connection method gssapi-with-mic [preauth]
debug1: attempt 1 failures 0 [preauth]
debug1: PAM: password authentication failed for root: Authentication failure
Failed password for root from 218.65.30.30 port 18460 ssh2
debug1: userauth-request for user root service ssh-connection method password [preauth]
debug1: attempt 2 failures 1 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: Client '[email protected]' not found in Kerberos database
debug1: krb5_cleanup_proc called
debug1: PAM: password authentication failed for root: Authentication failure
Failed password for root from 218.65.30.30 port 18460 ssh2
debug1: userauth-request for user root service ssh-connection method password [preauth]
debug1: attempt 3 failures 2 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: Client '[email protected]' not found in Kerberos database
debug1: krb5_cleanup_proc called
debug1: PAM: password authentication failed for root: Authentication failure
Failed password for root from 218.65.30.30 port 18460 ssh2
debug1: userauth-request for user krbuser service ssh-connection method password [preauth]
debug1: attempt 2 failures 0 [preauth]
debug1: temporarily_use_uid: 1001/1001 (e=0/0)
debug1: restore_uid: 0/0
debug1: temporarily_use_uid: 1001/1001 (e=0/0)
debug1: restore_uid: 0/0
debug1: do_pam_account: called
Accepted password for krbuser from 145.100.110.115 port 51946 ssh2
debug1: monitor_child_preauth: krbuser has been authenticated by privileged process
debug1: monitor_read_log: child log fd closed
debug1: temporarily_use_uid: 1001/1001 (e=0/0)
debug1: ssh_gssapi_storecreds: Not a GSSAPI mechanism
debug1: restore_uid: 0/0
debug1: PAM: establishing credentials
User child is on pid 20617
debug1: SELinux support disabled
debug1: PAM: establishing credentials
debug1: permanently_set_uid: 1001/1001
debug1: rekey after 134217728 blocks
debug1: rekey after 134217728 blocks
debug1: ssh_packet_set_postauth: called
debug1: Entering interactive session for SSH2.
debug1: server_init_dispatch_20
debug1: server_input_channel_open: ctype session rchan 0 win 1048576 max 16384
debug1: input_session_request
debug1: channel 0: new [server-session]
debug1: session_new: session 0
debug1: session_open: channel 0
debug1: session_open: session 0: link with channel 0
debug1: server_input_channel_open: confirm session
debug1: server_input_global_request: rtype [email protected] want_reply 0
debug1: server_input_channel_req: channel 0 request pty-req reply 1
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req pty-req
debug1: Allocating pty.
debug1: session_new: session 0
debug1: SELinux support disabled
debug1: session_pty_req: session 0 alloc /dev/pts/2
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request env reply 0
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req env
debug1: server_input_channel_req: channel 0 request shell reply 1
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req shell
Starting session: shell on pts/2 for krbuser from 145.100.110.115 port 51946 id 0
debug1: Setting controlling tty using TIOCSCTTY.
debug1: userauth-request for user root service ssh-connection method password [preauth]
debug1: attempt 4 failures 3 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: Client '[email protected]' not found in Kerberos database
debug1: krb5_cleanup_proc called
debug1: PAM: password authentication failed for root: Authentication failure
Failed password for root from 218.65.30.30 port 18460 ssh2
debug1: userauth-request for user root service ssh-connection method password [preauth]
debug1: attempt 5 failures 4 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: Client '[email protected]' not found in Kerberos database
debug1: krb5_cleanup_proc called
debug1: PAM: password authentication failed for root: Authentication failure
Failed password for root from 218.65.30.30 port 18460 ssh2
debug1: userauth-request for user root service ssh-connection method password [preauth]
debug1: attempt 6 failures 5 [preauth]
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: Kerberos password authentication failed: Client '[email protected]' not found in Kerberos database
debug1: krb5_cleanup_proc called
debug1: PAM: password authentication failed for root: Authentication failure
Failed password for root from 218.65.30.30 port 18460 ssh2
maximum authentication attempts exceeded for root from 218.65.30.30 port 18460 ssh2 [preauth]
Disconnecting: Too many authentication failures [preauth]
debug1: do_cleanup [preauth]
debug1: monitor_read_log: child log fd closed
debug1: do_cleanup
debug1: PAM: cleanup
debug1: Killing privsep child 20604
debug1: audit_event: unhandled event 12
debug1: inetd sockets after dupping: 5, 5
Connection from 218.65.30.30 port 58146 on 145.100.110.116 port 22
debug1: Client protocol version 2.0; client software version nsssh2_4.0.0032 NetSarang Computer, Inc.
debug1: no match: nsssh2_4.0.0032 NetSarang Computer, Inc.
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: permanently_set_uid: 106/65534 [preauth]
debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: kex: algorithm: diffie-hellman-group14-sha1 [preauth]
debug1: kex: host key algorithm: ssh-rsa [preauth]
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha1 compression: none [preauth]
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha1 compression: none [preauth]
debug1: expecting SSH2_MSG_KEXDH_INIT [preauth]
Na máquina do cliente:
kinit e klist antes da autenticação:
$ kinit -p krbuser
$ klist
Ticket cache: FILE:/tmp/krb5cc_1000
Default principal: [email protected]
Valid starting Expires Service principal
06/15/17 00:24:05 06/15/17 10:24:05 krbtgt/[email protected]
renew until 06/16/17 00:23:56
/etc/ssh/ssh config (um extrato):
GSSAPIAuthentication yes
GSSAPIDelegateCredentials yes
# GSSAPIKeyExchange no
# GSSAPITrustDNS no
E finalmente a autenticação SSH:
$ ssh [email protected] -vvv
...
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "service-0.metz.prac.os3.nl" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to service-0.metz.prac.os3.nl [145.***.***.***] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/client/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
...
debug1: Found key in /home/client/.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
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /home/client/.ssh/id_rsa ((nil))
debug2: key: /home/client/.ssh/id_dsa ((nil))
debug2: key: /home/client/.ssh/id_ecdsa ((nil))
debug2: key: /home/client/.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
debug3: send packet: type 50
debug2: we sent a gssapi-with-mic packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: send packet: type 50
debug2: we sent a gssapi-with-mic packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: send packet: type 50
debug2: we sent a gssapi-with-mic packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: send packet: type 50
debug2: we sent a gssapi-with-mic packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
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: Next authentication method: password
[email protected]'s password: <entering PW of Kerberos user> !!!
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to service-0.metz.prac.os3.nl ([145.***.***.***]: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 [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] 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
...
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: Thu Jun 15 00:28:57 2017
Connection established
Agora, klist mostra os seguintes tickets:
$ klist
Ticket cache: FILE:/tmp/krb5cc_1000
Default principal: [email protected]
Valid starting Expires Service principal
06/15/17 00:24:05 06/15/17 10:24:05 krbtgt/[email protected]
renew until 06/16/17 00:23:56
06/15/17 00:27:37 06/15/17 10:24:05 host/service-0.metz.prac.os3.nl@
renew until 06/16/17 00:23:56
06/15/17 00:27:37 06/15/17 10:24:05 host/[email protected]
renew until 06/16/17 00:23:56
Então, para resumir: O usuário Kerberos no cliente pode estabelecer uma sessão SSH para o servidor digitando sua senha Kerberos (!). Não é sua senha do UNIX. O tcpdump mostrou que o cliente autentica como root , que não é um usuário do Kerberos, e não tenho idéia de por que ele está usando esse nome de usuário, em vez de krbuser . Qual é o que eu usei com o comando kinit .
Alguém pode me dizer por que esta autenticação não está funcionando corretamente? Por favor, deixe-me saber se você precisar de informações adicionais. Eu tentei manter isso curto.
