├── .gitignore ├── LICENSE ├── README.md ├── meta └── main.yml ├── playbook.yml ├── tasks └── main.yml └── templates ├── login_duo.conf.j2 └── login_duo_multi /.gitignore: -------------------------------------------------------------------------------- 1 | playbook.retry 2 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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The role supports CentOS- and Debian- based systems, and has 4 | been tested on latest (05/24) CentOS 7 and Ubuntu 16.04. 5 | 6 | Duo is patched for multi-user support: any Duo user in the organization can authenticate as any user on the 7 | system (provided they also have a matching SSH key etc). 8 | 9 | If multiple humans use the same account on a system 10 | (Alice and Bob both log in as `centos`) this is great -- they can each have their own Duo account and 11 | hence own 2FA devices. If each human has their own user account, this probably isn't what you want and you 12 | should use a [different](https://github.com/jlafon/ansible-duo-security) Ansible role. 13 | 14 | Please read this README carefully to avoid creating security holes. In particular, note that you **must** 15 | modify the default Duo _New User Policy_. 16 | 17 | ## Role Variables 18 | * `duo_ssh_ikey` - Duo application Integration Key (found in application dashboard) 19 | * `duo_ssh_skey` - Duo application Secret Key (found in application dashboard) 20 | * `duo_ssh_host` - Duo application host endpoint (found in application dashboard) 21 | 22 | ## Security Discussion 23 | By default, Duo does not allow system-wide multi-user support (setting the `setuid` bit disables shared accounts for non-root-users, setting the `setuid` bit requires each user to have their own configuration file). This is for good reason: it allows every Duo user to retrieve the duo conf file, 24 | and hence fake authentication as other Duo users. 25 | 26 | However, by making the assumption that all Duo users are equally trusted: i.e., **all Duo users in the 27 | organization can perform the second factor of authentication for any account on the system**, then these 28 | security concerns go away. In fact, the assumption is weaker: a group of users can be created in the Duo 29 | dashboard, and the application restricted to this group. The trust then only need extend to users in this 30 | group. 31 | 32 | Additionally, the Duo **_New User Policy_ must be set to _Deny access to unenrolled users_**. Otherwise, 33 | an attacker can simply enter a nonexistent Duo user name, receive a link to enroll into Duo and then use 34 | their newly-created account to successfully complete 2FA. 35 | 36 | Finally, OpenSSH initializes port forwarding and tunneling before the Duo 2FA challenge, so `PermitTunnel` 37 | and `AllowTcpForwarding` are [disabled](https://duo.com/docs/loginduo) to avoid a potential attack via port 38 | forwarding. 39 | 40 | 41 | ## Walkthrough 42 | 1. Log into, or create a new account on [duo.com](https://duo.com/). 43 | 2. Use the _Applications_ tab of the Dashboard to protect a new `UNIX Application`. Make note of the 44 | integration key, secret key and API hostname. 45 | 3. Under the _Policy_ section of the application, create a new _Application Policy_. Set the _New User 46 | Policy_ to _Deny access to unenrolled users._. 47 | 4. Use the _Users_ tab of the dashboard to create a new Duo user. Add an email address, and follow the steps 48 | in the welcome email to complete the enrollment process. 49 | 5. Install Ansible and run 50 | ``` 51 | ansible-playbook --extra-vars "duo_ssh_ikey=IKEY duo_ssh_skey=SKEY duo_ssh_host=DUO_HOST" -u USER -i "HOST," playbook.yml 52 | ``` 53 | where `USER@HOST` is the server to run on, and `IKEY`, `SKEY` and `DUO_HOST` are the [vars](#Variables) 54 | noted in step 2. 55 | 6. Login to the server using the same key/etc as before. When prompted for a Duo user, enter the username 56 | created in step 4. Follow the on-screen instructions to complete push/SMS/voice authentication. 57 | 58 | ## Usage 59 | ### Standalone 60 | A barebones `playbook.yml` is included that can be used to run the role. Install Ansible and run 61 | ``` 62 | ansible-playbook --extra-vars "duo_ssh_ikey=IKEY duo_ssh_skey=SKEY duo_ssh_host=DUO_HOST" -u USER -i "HOST," playbook.yml 63 | ``` 64 | where `USER@HOST` is the machine to run on, and `IKEY`, `SKEY` and `DUO_HOST` are the vars described in 65 | [Variables](#Variables). 66 | 67 | ### Integration into an Existing Ansible Playbook 68 | To integrate the role into an existing ansible playbook: 69 | 1. Copy the `roles/duo` directoryfrom this repository into the existing ansible `roles` directory. 70 | 2. Add `duo` to the roles array in the existing playbook. 71 | 3. Add the duo [vars](#Variables) to the playbook or inventory. Alternatively, pass in the vars when 72 | running the `ansible-playbook` command, as demonstrated in [Standalone](#Standalone). 73 | 74 | ## License 75 | MIT -------------------------------------------------------------------------------- /meta/main.yml: -------------------------------------------------------------------------------- 1 | --- 2 | galaxy_info: 3 | author: Amida Technology Solutions 4 | description: Role to install and configure multi-user Duo for 2FA on SSH logins 5 | company: Amida Technology Solutions 6 | license: MIT 7 | min_ansible_version: 2.0 8 | platforms: 9 | - name: Debian 10 | versions: 11 | - all 12 | - name: Ubuntu 13 | versions: 14 | - all 15 | - name: CentOS 16 | versions: 17 | - all 18 | - name: Red Hat Enterprise Linux 19 | versions: 20 | - all 21 | galaxy_tags: 22 | - system 23 | - security 24 | - ssh 25 | -------------------------------------------------------------------------------- /playbook.yml: -------------------------------------------------------------------------------- 1 | --- 2 | - hosts: all 3 | roles: 4 | - duo 5 | vars: 6 | duo_ssh_ikey: "IKEY" 7 | duo_ssh_skey: "SKEY" 8 | duo_ssh_host: "DUO_HOST" 9 | -------------------------------------------------------------------------------- /tasks/main.yml: -------------------------------------------------------------------------------- 1 | --- 2 | - name: Install Python (Debian) 3 | raw: sudo apt-get install -y python 4 | when: ansible_distribution == 'Debian' or ansible_distribution == 'Ubuntu' 5 | 6 | - name: Install prerequisites (CentOS) 7 | yum: 8 | name: 9 | - openssl-devel 10 | - pam-devel 11 | - libtool 12 | - autoconf 13 | - git 14 | state: present 15 | when: ansible_distribution == 'CentOS' or ansible_distribution == 'Red Hat Enterprise Linux' 16 | become: true 17 | 18 | - name: Install prerequisites (Debian) 19 | apt: 20 | name: 21 | - libssl-dev 22 | - libpam-dev 23 | - libtool 24 | - autoconf 25 | - build-essential 26 | state: present 27 | when: ansible_distribution == 'Debian' or ansible_distribution == 'Ubuntu' 28 | become: true 29 | 30 | - name: Download duo 31 | git: 32 | dest: /tmp/duo 33 | repo: https://github.com/duosecurity/duo_unix.git 34 | force: yes 35 | accept_hostkey: yes 36 | version: master 37 | 38 | - name: Patch duo for multiuser support 39 | lineinfile: 40 | dest: /tmp/duo/login_duo/login_duo.c 41 | regexp: 'ctx->duouser != NULL' 42 | line: 'if (ctx->config != NULL) {' 43 | 44 | - name: Generate duo configure 45 | command: autoreconf -i chdir=/tmp/duo 46 | 47 | - name: Configure duo source 48 | command: ./configure --prefix=/usr chdir=/tmp/duo 49 | 50 | - name: Build duo 51 | command: make chdir=/tmp/duo 52 | 53 | - name: Install duo 54 | command: make install chdir=/tmp/duo 55 | become: true 56 | 57 | - name: Clear duo source dir 58 | file: 59 | path: /tmp/duo 60 | state: absent 61 | 62 | - name: Install duo config 63 | template: 64 | src: login_duo.conf.j2 65 | dest: /etc/duo/login_duo.conf 66 | owner: sshd 67 | group: 0 68 | mode: 0600 69 | become: true 70 | 71 | - name: Install helper script 72 | template: 73 | src: login_duo_multi 74 | dest: /usr/sbin/login_duo_multi 75 | owner: root 76 | mode: 0755 77 | become: true 78 | 79 | - name: Add duo to ssh login 80 | lineinfile: 81 | dest: /etc/ssh/sshd_config 82 | regexp: '^ForceCommand' 83 | line: 'ForceCommand /usr/sbin/login_duo_multi' 84 | become: true 85 | 86 | - name: Disable ssh PermitTunnel 87 | lineinfile: 88 | dest: /etc/ssh/sshd_config 89 | regexp: '^PermitTunnel' 90 | line: 'PermitTunnel no' 91 | become: true 92 | 93 | - name: Disable ssh AllowTcpForwarding 94 | lineinfile: 95 | dest: /etc/ssh/sshd_config 96 | regexp: '^AllowTcpForwarding' 97 | line: 'AllowTcpForwarding no' 98 | become: true 99 | 100 | - name: Restart ssh 101 | service: name=sshd state=restarted 102 | become: true 103 | -------------------------------------------------------------------------------- /templates/login_duo.conf.j2: -------------------------------------------------------------------------------- 1 | [duo] 2 | ; Duo integration key 3 | ikey = {{duo_ssh_ikey}} 4 | ; Duo secret key 5 | skey = {{duo_ssh_skey}} 6 | ; Duo API host 7 | host = {{duo_ssh_host}} 8 | ; Send command for Duo Push authentication 9 | pushinfo = yes 10 | autopush = yes -------------------------------------------------------------------------------- /templates/login_duo_multi: -------------------------------------------------------------------------------- 1 | #!/bin/bash 2 | read -rp "Enter Duo user to authenticate as: " user 3 | /usr/sbin/login_duo -f $(echo $user | tr -cd '[[:alnum:]]._-') 4 | --------------------------------------------------------------------------------