OTP-keycloak setup

 https://github.com/kha7iq/kc-ssh-pam?tab=readme-ov-file

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Install • Usage • Configuration • Contributers • Contributing •

Keycloak SSH PAM

kc-ssh-pam designed to streamline the process of user authentication and enable users to access Linux systems through SSH. The program integrates with Keycloak to obtain a password grant token based on the user's login credentials, including their username and password. If two-factor authentication is enabled for the user, the program supports OTP code as well.

Once the password grant token is obtained, the program verifies it and passes the necessary parameters so that the user can be authenticated via SSH and access the Linux systems.

Install

DEB & RPM

Manual

Usage

❯ kc-ssh-pam --help
Usage: kc-ssh-pam USERNAME PASSWORD/[OTP]

Generates a password grant token from Keycloak for the given user.

Options:
  -h, --help              Show this help message and exit
  -v, --version           Show version information
  -c                      Set configuration file path

Notes:
  For the program to function properly, it needs to locate a configuration file called 'config.toml'.
  The program will search for this file in the current directory, '/opt/kc-ssh-pam' and '$HOME/.config/config.toml',
  in that specific order. You can also set a custom path by specifying KC_SSH_CONFIG variable or -c flag which takes prefrence.

  In addition to defaults, all configuration parameters can also be provided through environment variables.

  KC_SSH_CONFIG KC_SSH_REALM KC_SSH_ENDPOINT KC_SSH_CLIENTID KC_SSH_CLIENTSECRET KC_SSH_CLIENTSCOPE
  
  To use the program, you must create a client in Keycloak and provide the following 
  information in the configuration file: realm, endpoint, client ID, client secret, and 
  client scope is optional.

Arguments:
  USERNAME                The username of the user is taken from $PAM_USER environment variable
  PASSWORD                The password of the user is taken from stdIn
  OTP                     (Optional) The OTP code if two-factor authentication is enabled i.e (password/otp)

  EXAMPLE                 (With otp): echo testpass/717912 | kc-ssh-pam (Only Password): echo testpass | kc-ssh-pam

Configuration

For the program to function properly, it needs to locate a configuration file called config.toml.

The program will search for this file in the follwoing order..

1. If a config path is specified using the -c flag, it will override any other defined options.
2. Verify the existence of the KC_SSH_CONFIG variable; if it's defined, use the location specified within it.
3. The working directory where the program is being executed from.
4. Default install location /opt/kc-ssh-pam/
5. $HOME/.config/

Important

For proper operation, ensure that SeLinux is configured in Permissive mode.

config.toml

realm = "ssh-demo"
endpoint = "https://keycloak.example.com"
clientid = "keycloak-client-id"
clientsecret = "MIKEcHObWmI3V3pF1hcSqC9KEILfLN"
clientscop = "openid"

• Edit /etc/pam.d/sshd and add the following at the top of file

auth sufficient pam_exec.so expose_authtok      log=/var/log/kc-ssh-pam.log     /opt/kc-ssh-pam/kc-ssh-pam

• User is not automatically created during login, so a local user must be present on the system before hand.

To automatically create a user install

 apt-get install libpam-script

Add the follwoing in /etc/pam.d/sshd underneath previous argument

auth optional pam_script.so

Then, the script itself. In the file /usr/share/libpam-script/pam_script_auth

#!/bin/bash
adduser $PAM_USER --disabled-password --quiet --gecos ""

In PAM modules, username is given in "$PAM_USER" variable.

Make this script executable

chmod +x /usr/share/libpam-script/pam_script_auth 

Restart sshd service

sudo systemctl restart sshd

Keycloak Cleint Creation

Step 1: Log in to the Keycloak Administration Console.

Step 2: Select the realm for which you want to create the client.

Step 3: Click on "Clients" from the left-hand menu, and then click on the "Create" button.

Step 4: In the "Client ID" field, enter "ssh-login".

Step 5: Set the "Client Protocol" to "openid-connect".

Step 6: In the "Redirect URIs" field, enter "urn:ietf:wg:oauth:2.0:oob".

Step 7: In the "Access Type" field, select "confidential".

Step 8: In the "Standard Flow Enabled" field, select "ON".

Step 9: In the "Direct Access Grants Enabled" field, select "ON".

Step 10: Click on the "Save" button to create the client.

To get the credentials of the client, follow these steps:

Step 1: Go to the "Clients" page in the Keycloak Administration Console.

Step 2: Select the "ssh-login" client from the list.

Step 3: Click on the "Credentials" tab.

Step 4: The client secret will be displayed under the "Client Secret" section.

💠 Detailed article with screenshots is also available here