SSH login using Active Directory credentials

Question

I am having trouble logging into a Linux system via SSH using my Active Directory credentials. the system is bound to AD, and all of the required packages are installed and configured, but I cannot login. What am I missing here?

I get the following errors in /var/log/secure:

Mar  7 14:32:02 password sshd[4657]: User myusername from <anothersystem.mydomain.com> not allowed because none of user's groups are listed in AllowGroups
Mar  7 14:32:02 password sshd[4657]: input_userauth_request: invalid user <myusername> [preauth]

wbinfo -g lists all groups and wbinfo -u lists all users

My configurations:

/etc/pam.d/system-auth

auth        required      pam_env.so
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet_success
auth        sufficient    pam_sss.so use_first_pass
auth        sufficient    pam_krb5.so use_first_pass
auth        sufficient    pam_winbind.so cached_login use_first_pass
auth        required      pam_deny.so

account     required      pam_unix.so broken_shadow
account     sufficient    pam_localuser.so
account     sufficient    pam_succeed_if.so uid < 500 quiet
account     [default=bad success=ok user_unknown=ignore] pam_sss.so
account     [default=bad success=ok user_unknown=ignore] pam_krb5.so
account     [default=bad success=ok user_unknown=ignore] pam_winbind.so    cached_login
account     required      pam_permit.so

password    requisite     pam_pwquality.so try_first_pass local_users_only    retry=3 authtok_type=
password    sufficient    pam_unix.so sha512 shadow nullok try_first_pass use_authtok
password    sufficient    pam_sss.so use_authtok
password    sufficient    pam_krb5.so use_authtok
password    sufficient    pam_winbind.so use_authtok
password    required      pam_deny.so

session     optional      pam_keyinit.so revoke
session     required      pam_limits.so
session     optional      pam_systemd.so
session     optional      pam_oddjob_mkhomedir.so umask=0077
session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session     required      pam_unix.so
session     optional      pam_sss.so
session     optional      pam_krb5.so
session     optional      pam_winbind.so cached_login

cd /etc/sssd/sssd.conf

[sssd]
domains = mydomain.com
config_file_version = 2
services = nss, pam

[domain/mydomain.com]
ad_domain = mydomain.com
krb5_realm = MYDOMAIN.COM
realmd_tags = manages-system joined-with-samba
cache_credentials = True
id_provider = ad
krb5_store_password_if_offline = True
default_shell = /bin/bash
ldap_id_mapping = True
use_fully_qualified_names = True
fallback_homedir = /home/%d/%u
access_provider = simple
simple_allow_groups = IT Security

/etc/ssh/sshd_config

    #       $OpenBSD: sshd_config,v 1.93 2014/01/10 05:59:19 djm Exp $

    # This is the sshd server system-wide configuration file.  See
    # sshd_config(5) for more information.

    # This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin

    # The strategy used for options in the default sshd_config shipped with
    # OpenSSH is to specify options with their default value where
    # possible, but leave them commented.  Uncommented options override the
    # default value.

    # If you want to change the port on a SELinux system, you have to tell
    # SELinux about this change.
    # semanage port -a -t ssh_port_t -p tcp #PORTNUMBER
    #
    #Port 22
    #AddressFamily any
    #ListenAddress 0.0.0.0
    #ListenAddress ::

    # The default requires explicit activation of protocol 1
    #Protocol 2

    # HostKey for protocol version 1
    #HostKey /etc/ssh/ssh_host_key
    # HostKeys for protocol version 2
    HostKey /etc/ssh/ssh_host_rsa_key
    #HostKey /etc/ssh/ssh_host_dsa_key
    HostKey /etc/ssh/ssh_host_ecdsa_key
    HostKey /etc/ssh/ssh_host_ed25519_key

    # Lifetime and size of ephemeral version 1 server key
    #KeyRegenerationInterval 1h
    #ServerKeyBits 1024

    # Ciphers and keying
    #RekeyLimit default none

    # Logging
    # obsoletes QuietMode and FascistLogging
    #SyslogFacility AUTH
    SyslogFacility AUTHPRIV
    #LogLevel INFO

    # Authentication:

    #LoginGraceTime 2m
    #PermitRootLogin yes
    # Only allow root to run commands over ssh, no shell
    PermitRootLogin forced-commands-only
    #StrictModes yes
    #MaxAuthTries 6
    #MaxSessions 10
    AllowGroups IT Security

    #RSAAuthentication yes
    #PubkeyAuthentication yes

    # The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
    # but this is overridden so installations will only check .ssh/authorized_keys
    AuthorizedKeysFile .ssh/authorized_keys

    #AuthorizedPrincipalsFile none

    #AuthorizedKeysCommand none
    #AuthorizedKeysCommandUser nobody

    # For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
    #RhostsRSAAuthentication no
    # similar for protocol version 2
    #HostbasedAuthentication no
    # Change to yes if you don't trust ~/.ssh/known_hosts for
    # RhostsRSAAuthentication and HostbasedAuthentication
    #IgnoreUserKnownHosts no
    # Don't read the user's ~/.rhosts and ~/.shosts files
    #IgnoreRhosts yes

    # To disable tunneled clear text passwords, change to no here!
    #PasswordAuthentication yes
    #PermitEmptyPasswords no
    # EC2 uses keys for remote access
    PasswordAuthentication no

    # Change to no to disable s/key passwords
    #ChallengeResponseAuthentication yes
    ChallengeResponseAuthentication no

    # Kerberos options
    KerberosAuthentication yes
    #KerberosOrLocalPasswd yes
    KerberosTicketCleanup yes
    #KerberosGetAFSToken yes
    #KerberosUseKuserok yes

    # GSSAPI options
    GSSAPIAuthentication yes
    #GSSAPICleanupCredentials yes
    #GSSAPIStrictAcceptorCheck yes
    #GSSAPIKeyExchange no
    #GSSAPIEnablek5users no

    # Set this to 'yes' to enable PAM authentication, account processing,
    # and session processing. If this is enabled, PAM authentication will
    # be allowed through the ChallengeResponseAuthentication and
    # PasswordAuthentication.  Depending on your PAM configuration,
    # PAM authentication via ChallengeResponseAuthentication may bypass
    # the setting of "PermitRootLogin without-password".
    # If you just want the PAM account and session checks to run without
    # PAM authentication, then enable this but set PasswordAuthentication
    # and ChallengeResponseAuthentication to 'no'.
    # WARNING: 'UsePAM no' is not supported in Amazon Linux AMI and may cause several
    # problems.
    # Leaving enabled as described so that account and session checks are run
    UsePAM yes

    #AllowAgentForwarding yes
    #AllowTcpForwarding yes
    #GatewayPorts no
    X11Forwarding yes
    #X11DisplayOffset 10
    #X11UseLocalhost yes
    #PermitTTY yes
    #PrintMotd yes
    # Explicitly enable
    PrintLastLog yes
    #TCPKeepAlive yes
    #UseLogin no
    UsePrivilegeSeparation sandbox          # Default for new installations.
    #PermitUserEnvironment no
    #Compression delayed
    #ClientAliveInterval 0
    #ClientAliveCountMax 3
    #ShowPatchLevel no
    #UseDNS yes
    #PidFile /var/run/sshd.pid
    #MaxStartups 10:30:100
    #PermitTunnel no
    #ChrootDirectory none
    #VersionAddendum none

    # no default banner path
    #Banner none

    # Accept locale-related environment variables
    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

    # override default of no subsystems
    Subsystem sftp  /usr/libexec/openssh/sftp-server

    # Example of overriding settings on a per-user basis
    #Match User anoncvs
    #       X11Forwarding no
    #       AllowTcpForwarding no
    #       PermitTTY no
    #       ForceCommand cvs server

Solution

AllowGroups This keyword can be followed by a list of group name patterns, separated by spaces. If specified, login is allowed only for users whose primary group or supplementary group list matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. The allow/deny directives are processed in the following order: DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.

It looks like the Problem is the whitespace in the sshd_config, which is used as separator in the AllowGroups field. Although even not really documented, it should work to use double-quotes, using "IT Security".

https://bugzilla.mindrot.org/show_bug.cgi?id=482

For debugging groups id <username> and getent are always helpful to see if the users and groups are properly retrieved.

Also check the sssd.conf man page and verify how sssd handles whitespace in groups.

Comments

[Michael Hampton]

The error message is self-explanatory. First, you should read it, and then you should look at the directive it mentions, and then you should do the needful.

[newyorkstateofmind]

@MichaelHampton That's what I thought, but the error persists even after adding the group and/or user to my sssd config.

[Michael Hampton]

I suspect that you didn't actually do the needful. Which group is this user in?

[newyorkstateofmind]

The user is a member of the 'IT Security' group in Active Directory. Not a member of any local groups.

[Michael Hampton]

But you have defined two allowed groups, "IT" and "Security". Not "IT Security".

[newyorkstateofmind]

It's actually one group. I thought I accounted for the space between IT and security by specifying the carat between the two words.

[Paul Haldane]

I don't see any caret in the group reference in the posted sssd and sshd config files

[newyorkstateofmind]

What is the correct syntax for adding an AD user group with a space in it's name?