Duo can be easily added to any Unix system to protect remote (SSH) or local logins with the addition of a simple pam_duo PAM module. It has been tested on Linux (RedHat, Fedora, CentOS, Debian, Ubuntu, Amazon Linux), BSD (FreeBSD, NetBSD, OpenBSD), Solaris, and AIX. The code is open-source and available on GitHub.
Duo Unix with Pluggable Authentication Modules (PAM) support provides a secure and customizable method for protecting Unix and Linux logins. We recommend deploying the pam_duo module in most scenarios, but if you are unable to use PAM see our login_duo instructions.
This application communicates with Duo's service on TCP port 443. Firewall configurations that restrict outbound access to Duo's service with rules using destination IP addresses or IP address ranges aren't recommended, since these may change over time to maintain our service's high availability. If your organization requires IP-based rules, please review this Duo KB article.
Duo Unix is FIPS-compliant as of version 1.10.4 when run on any machine that has an operating system-wide FIPS mode (like Centos/RedHat 7, Ubuntu 16.04, etc.). No additional flags or options are required.
Before moving on to the deployment steps, it's a good idea to familiarize yourself with Duo administration concepts and features like options for applications, available methods for enrolling Duo users, and Duo policy settings and how to apply them. See all Duo Administrator documentation.
Then you'll need to:
duo_unix tarball (view checksum). From the command line you can use curl or wget to download the file, like $ wget --content-disposition https://dl.duosecurity.com/duo_unix-latest.tar.gz.The security of your Duo application is tied to the security of your secret key (skey). Secure it as you would any sensitive credential. Don't share it with unauthorized individuals or email it to anyone under any circumstances!
pam_duo PrerequisitesOpenSSL development headers and libraries are required for pam_duo, as well as libpam. When compiling on SUSE/SLES, the zlib package is also necessary.
| Dependency | Platform | Installation |
|---|---|---|
| OpenSSL | FreeBSD, NetBSD | Installed by default |
| Debian, Ubuntu | apt-get install libssl-dev |
|
| Red Hat, Fedora, CentOS, Amazon Linux | yum install openssl-devel |
|
| SUSE/SLES | zypper install libopenssl-devel |
|
| Solaris | pkg install openssl |
|
| AIX | 3rd party packages or source build | |
| libpam | FreeBSD, NetBSD, Solaris, AIX | Installed by default |
| Debian, Ubuntu | apt-get install libpam-dev |
|
| Red Hat, Fedora, CentOS, Amazon Linux | yum install pam-devel |
|
| SUSE/SLES | zypper install pam-devel |
|
| selinux-policy-devel | CentOS 7 & 8, Red Hat 7 & 8 (if using SELinux) | yum install selinux-policy-devel |
| bzip2 | CentOS 7 & 8, Red Hat 7 & 8 (if using SELinux) | yum install bzip2 |
| zlib | SUSE/SLES | zypper install zlib-devel |
You also need a compiler like gcc installed on your system to build Duo Unix.
pam_duoOnce the required dependencies are built and installed, build and install duo_unix.
Extract the downloaded tarball for duo_unix and change to the extracted directory (note your actual extracted directory name reflects the actual version downloaded; the example syntax below references version 1.12.0). View checksums for Duo downloads here.
$ tar zxf duo_unix-latest.tar.gz
$ cd duo_unix-1.12.0
Build and install duo_unix with PAM support ( pam_duo).
$ ./configure --with-pam --prefix=/usr && make && sudo make installFor advanced build options, see the README file in the source tarball.
Once installed, proceed to Duo configuration.
To more easily install and maintain Duo Unix deployments, we've built Linux packages for some popular Linux distributions. Duo tests these packages against the specific listed versions of their respective distributions. Please test all packages thoroughly prior to deploying them into your environment to ensure a great experience.
When installing Duo Unix from packages, there is no need to also install the build-from-source prerequisites on the target systems.
To download the packages, you'll need Duo's GPG key. The GPG key verifies the Duo Unix package for currently supported OS distributions and versions.
We updated the Duo GPG key for packages on supported distros on May 18, 2020. If you installed Duo Unix from packages before May 2020, be sure to update your previously imported GPG key using command for your distro the before the next time you install or upgrade Duo Unix.
The current Duo GPG key expires in May 2030.
OS distributions identified as no longer supported in the distro-specific packages sections use a previous GPG key. We won't replace or update the GPG key on these EOL versions when it expires, and urge you to update to a supported OS.
CentOS
Tested against 8.0 64-bit and 7.1 64-bit
IMPORTANT:
Centos 5 reached end of life on March 31, 2017. Duo Unix 1.11.0 was the last release with CentOS 5 support.
Centos 6 reached end of life on November 30, 2020. Duo Unix 1.11.4 was the last release with CentOS 6 support.
Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
Create /etc/yum.repos.d/duosecurity.repo with the following contents:
[duosecurity]
name=Duo Security Repository
baseurl=https://pkg.duosecurity.com/CentOS/$releasever/$basearch
enabled=1
gpgcheck=1Execute the following shell commands for Centos 7 and later:
# rpm --import https://duo.com/DUO-GPG-PUBLIC-KEY.asc
# yum install duo_unix
Ubuntu
Tested against 20.04 focal 64-bit, 18.04 bionic 64-bit, 16.04 xenial 32/64-bit, and 14.04.3 trusty 32/64-bit.
IMPORTANT:
Ubuntu 12.04 reached end of life in April 2017. Duo Unix 1.11.3 was the last release with Ubuntu 12.04 support.
Ubuntu 14.04 reached end of life in April 2019. Duo Unix 1.12.0 is the last release with Ubuntu 14.04 support.
Ubuntu 16.04 reached end of life in April 2021. Duo Unix 1.12.0 is the last release with Ubuntu 16.04 support.
Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
Create /etc/apt/sources.list.d/duosecurity.list with the following contents:
deb https://pkg.duosecurity.com/Ubuntu trusty mainor
deb https://pkg.duosecurity.com/Ubuntu xenial mainor
deb [arch=amd64] https://pkg.duosecurity.com/Ubuntu bionic mainor
deb [arch=amd64] https://pkg.duosecurity.com/Ubuntu focal mainExecute the following shell commands for Ubuntu 14.04 and later:
# curl -s https://duo.com/DUO-GPG-PUBLIC-KEY.asc | sudo apt-key add -
# apt-get update && apt-get install duo-unix
Red Hat Enterprise Linux
Tested against 8.0 64-bit, 7.0 64-bit, and 6.4 32/64-bit.
IMPORTANT: Red Hat 5 reached full end of life on November 30, 2020. Duo Unix 1.11.0 was the last release with Red Hat 5 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
Create /etc/yum.repos.d/duosecurity.repo with the following contents:
[duosecurity]
name=Duo Security Repository
baseurl=https://pkg.duosecurity.com/RedHat/$releasever/$basearch
enabled=1
gpgcheck=1Execute the following shell commands for Red Hat 6 and later:
# rpm --import https://duo.com/DUO-GPG-PUBLIC-KEY.asc
# yum install duo_unix
Debian
Tested against 11.0 32/64-bit, 10.0 32/64-bit, 9.5 32/64-bit.
IMPORTANT:
Debian 6 reached end of life on May 31, 2015. Duo Unix 1.9.18 was the last release with Debian 6 support.
Debian 7 reached end of life on April 26, 2016. Duo Unix 1.11.1 was the last release with Debian 7 support.
Debian 8 reached end of life on June 30, 2020. Duo Unix 1.11.4 was the last release with Debian 8 support.
Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
Create /etc/apt/sources.list.d/duosecurity.list with the following contents:
deb https://pkg.duosecurity.com/Debian stretch mainor
deb https://pkg.duosecurity.com/Debian buster mainor
deb https://pkg.duosecurity.com/Debian bullseye mainExecute the following shell commands for Debian 9 and later:
# curl -s https://duo.com/DUO-GPG-PUBLIC-KEY.asc | sudo apt-key add -
# apt-get update && apt-get install duo-unix
The pam_duo.conf configuration file uses the INI format.
Once duo_unix is installed, edit pam_duo.conf
(in /etc/duo or /etc/security) to add the integration key, secret key, and API hostname from your Duo Unix application.
You may also add optional Duo configuration options to pam_duo.conf. See the table below for all available settings.
Example configuration file with additional options:
[duo]
; Duo integration key
ikey = INTEGRATION_KEY
; Duo secret key
skey = SECRET_KEY
; Duo API hostname
host = API_HOSTNAME
pushinfo=yes
autopush=yes| Key | Required? | Description |
|---|---|---|
ikey
|
Required | Your integration key |
skey
|
Required | Your secret key |
host
|
Required |
Your API hostname i.e. api-XXXXXXXX.duosecurity.com
|
groups
|
Optional |
If specified, Duo authentication is required only for users whose primary group or supplementary group list matches one of the space-separated pattern lists. A pattern consists of zero or more non-whitespace characters, " A pattern-list is a comma-separated list of patterns. Patterns within pattern-lists may be negated by preceding them with an exclamation mark ("
|
failmode
|
Optional |
On service or configuration errors that prevent Duo authentication, fail "safe" (allow access) or "secure" (deny access). The default is "safe". |
pushinfo
|
Optional |
Include information such as the command to be executed in the Duo Push message. Either "yes" or "no". The default is "no". |
http_proxy
|
Optional |
Use the specified HTTP proxy. If the HTTP proxy requires authentication, include the credentials in the proxy URL. Example format: |
autopush
|
Optional |
Either "yes" or "no". Default is "no". If "yes", Duo Unix will automatically send a push login request to the user's phone, falling back on a phone call if push is unavailable. Note that this effectively disables passcode authentication. If "no", the user will be prompted to choose an authentication method. When configured with |
motd
|
Optional |
Print the contents of This option is only available for |
prompts
|
Optional |
If a user fails to authenticate with a second factor, Duo Unix will prompt the user to authenticate again. This option sets the maximum number of prompts that Duo Unix will display before denying access. Must be 1, 2, or 3. Default is 3. For example, when When configured with |
accept_env_factor
|
Optional |
Look for factor selection or passcode in the The SSH client will need Default is This option is only available for |
fallback_local_ip
|
Optional |
Duo Unix reports the IP address of the authorizing user, for the purposes of authorization and network allow/deny. If Duo Unix cannot detect the IP address of the client, setting If you are using Authorized Networks, enabling this option could cause unauthorized logins if the local IP is listed in the allow list. |
https_timeout
|
Optional |
Set to the number of seconds to wait for HTTPS responses from Duo Security. If Duo Security takes longer than the configured number of seconds to respond to the preauth API call, the configured failmode is triggered. Other network operations such as DNS resolution, TCP connection establishment, and the SSL handshake have their own independent timeout and retry logic. Default is 0, which disables the HTTPS timeout. If you specify an |
send_gecos
|
Optional |
Sends the entire GECOS field as the Duo username. Default is If you specify |
gecos_username_pos
|
Optional |
Specify this option to select what position from the GECOS field will be used as the username. Positions are separated by whatever you specify in For example, if the
Then setting If not configured, the GECOS field is not parsed for the username. Overrides |
gecos_delim
|
Optional |
Specify this option to change the default value of the GECOS delimiter from a comma to another character. The new delimiter specified must be exactly one character, and must a valid punctuation character other than a colon ( For example, if the
Then setting If not configured, the default comma ( |
For more information, see the man page for pam_duo.
We recommend leaving a root shell open while making any changes to your PAM or sshd configuration, in order to prevent accidentally locking yourself out. Additionally, always make sure your PAM configuration works locally before testing it with SSH logins.
If you would like to use pam_duo with SSH public key authentication, make the following changes to your sshd_config file (usually in /etc or /etc/ssh).
This feature is only available with OpenSSH 6.2+, SSH protocol 2, and Duo Unix 1.9.15 or later.
PubkeyAuthentication yes
PasswordAuthentication no
AuthenticationMethods publickey,keyboard-interactiveYou'll need to modify your system's PAM configuration to include a line like the following:
auth required pam_duo.soDepending on your OS or architecture, the pam_duo.so module might be in /lib64/security instead of the default location /lib/security. If so, specify the full path to pam_duo.so in the PAM config file, such as /lib64/security/pam_duo.so.
The location of this line and the specified control flag (e.g. "required", "requisite", "sufficient") varies. For most common configurations, place pam_duo directly after pam_unix (frequently found in common-auth or system-auth on Linux), set pam_unix's control flag to "requisite", and set pam_duo's control flag to whatever pam_unix used to be.
If you want to use pam_duo with your installation of OpenSSH sshd, set both UsePAM and ChallengeResponseAuthentication to yes in your sshd_config file (usually
in /etc or /etc/ssh). You should also set UseDNS to no so that PAM Duo is always passed the IP address of the connecting user, rather than the resolved hostname.
UsePAM yes
ChallengeResponseAuthentication yes
UseDNS noBe sure to restart the SSH service after making edits to sshd and sshd_config to apply the updated configuration with Duo.
PAM configuration examples for common Linux systems:
Remember that you may need to specify the full path to pam_duo.so in the PAM config file, such as /lib64/security/pam_duo.so if the module is not in the default location /lib/security.
Note: Running authconfig after editing your PAM config files will overwrite your changes. Do not run authconfig once you edit your PAM files to add Duo.
If you must preserve your ability to run authconfig in the future, use the symbolic link method described in the "Keeping Custom Settings with authconfig" topic in section 4.1.2 of the Red Hat Security Guide.
System-wide Authentication
/etc/pam.d/system-auth
Before:
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.soAfter:
auth required pam_env.so
# auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_unix.so nullok try_first_pass
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
#%PAM-1.0
auth required pam_sepermit.so
auth substack password-auth
auth include postloginAfter:
#%PAM-1.0
auth required pam_sepermit.so
#auth substack password-auth
auth required pam_env.so
auth sufficient pam_duo.so
auth required pam_deny.so
auth include postloginIf you are running SELinux you must install the selinux-policy-devel and policycoreutils-python prerequisite packages and also update your policies to include authlogin_duo (run from the location where you built Duo Unix):
sudo make -C pam_duo semodule
sudo make -C pam_duo semodule-install
This allows sshd to make outgoing HTTP connections, which is required for Duo authentication to complete.
Verify that your SELinux configuration has been updated to include Duo:
$ semodule -l | grep duo
The semodule output should include:
authlogin_duo
There are two adjustable tunables:
pam_duo_permit_local_login allows local logins to use pam_duo (off by default)
pam_duo_permit_sshd allows sshd to use pam_duo (on by default)
To turn on and off the tunables:
sudo setsebool -P pam_duo_permit_sshd on/off
sudo setsebool -P pam_duo_permit_local_login on/off
The -P flag causes the boolean to persist through server restarts.
Note: If the nis_enabled tunable is on then regardless of the value of pam_duo_permit_sshd pam_duo will always be able to access Duo via ssh.
System-wide Authentication
/etc/pam.d/system-auth
Before:
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.soAfter:
auth required pam_env.so
# auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_unix.so nullok try_first_pass
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
#%PAM-1.0
auth required pam_sepermit.so
auth substack password-auth
auth include postloginAfter:
#%PAM-1.0
auth required pam_sepermit.so
#auth substack password-auth
auth required pam_env.so
auth sufficient pam_duo.so
auth required pam_deny.so
auth include postloginIf you are running SELinux you must install the selinux-policy-devel prerequisite package and also update your policies to include authlogin_duo (run from the location where you built Duo Unix):
sudo make -C pam_duo semodule
sudo make -C pam_duo semodule-install
This allows sshd to make outgoing HTTP connections, which is required for Duo authentication to complete.
Verify that your SELinux configuration has been updated to include Duo:
$ semodule -l | grep duo
The semodule output should include (depending on your specific v7 version):
authlogin_duo 2.1.0
or
authlogin_duo
There are two adjustable tunables:
pam_duo_permit_local_login allows local logins to use pam_duo (off by default)
pam_duo_permit_sshd allows sshd to use pam_duo (on by default)
To turn on and off the tunables:
sudo setsebool -P pam_duo_permit_sshd on/off
sudo setsebool -P pam_duo_permit_local_login on/off
The -P flag causes the boolean to persist through server restarts.
Note: If the nis_enabled tunable is on then regardless of the value of pam_duo_permit_sshd pam_duo will always be able to access Duo via ssh.
IMPORTANT: Centos 6 reached end of life on November 30, 2020. Duo Unix 1.11.4 was the last release with CentOS 6 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
IMPORTANT: Centos 5 reached end of life on March 31, 2017. Duo Unix 1.11.0 was the last release with CentOS 5 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
System-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_deny.so
auth required pam_permit.soAfter:
# auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_unix.so nullok_secure
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSystem-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_deny.so
auth required pam_permit.soAfter:
# auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_unix.so nullok_secure
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soIMPORTANT: Ubuntu 16.04 reached end of life in April 2021. Duo Unix 1.12.0 is the last release with Ubuntu 16.04 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
System-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_deny.so
auth required pam_permit.soAfter:
# auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_unix.so nullok_secure
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soIMPORTANT: Ubuntu 14.04 reached end of life in April 2019. Duo Unix 1.12.0 is the last release with Ubuntu 14.04 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
System-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_deny.soAfter:
# auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_unix.so nullok_secure
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.so
auth optional pam_cap.soIMPORTANT: Ubuntu 12.04 reached end of life in April 2017. Duo Unix 1.11.3 was the last release with Ubuntu 12.04 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
Note: Running authconfig after editing your PAM config files will overwrite your changes. Do not run authconfig once you edit your PAM files to add Duo.
If you must preserve your ability to run authconfig in the future, use the symbolic link method described in the "Keeping Custom Settings with authconfig" topic in section 4.1.2 of the Red Hat Security Guide.
System-wide Authentication
/etc/pam.d/system-auth
Before:
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.soAfter:
auth required pam_env.so
# auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_unix.so nullok try_first_pass
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
#%PAM-1.0
auth required pam_sepermit.so
auth substack password-auth
auth include postloginAfter:
#%PAM-1.0
auth required pam_sepermit.so
#auth substack password-auth
auth required pam_env.so
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.so
auth include postloginIf you are running SELinux you must install the selinux-policy-devel prerequisite package and also update your policies to include authlogin_duo (run from the location where you built Duo Unix):
sudo make -C pam_duo semodule
sudo make -C pam_duo semodule-install
This allows sshd to make outgoing HTTP connections, which is required for Duo authentication to complete.
Verify that your SELinux configuration has been updated to include Duo:
$ semodule -l | grep duo
The semodule output should include:
authlogin_duo
There are two adjustable tunables:
pam_duo_permit_local_login allows local logins to use pam_duo (off by default)
pam_duo_permit_sshd allows sshd to use pam_duo (on by default)
To turn on and off the tunables:
sudo setsebool -P pam_duo_permit_sshd on/off
sudo setsebool -P pam_duo_permit_local_login on/off
The -P flag causes the boolean to persist through server restarts.
Note: If the nis_enabled tunable is on then regardless of the value of pam_duo_permit_sshd pam_duo will always be able to access Duo via ssh.
System-wide Authentication
/etc/pam.d/system-auth
Before:
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.soAfter:
auth required pam_env.so
# auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_unix.so nullok try_first_pass
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
#%PAM-1.0
auth required pam_sepermit.so
auth substack password-auth
auth include postloginAfter:
#%PAM-1.0
auth required pam_sepermit.so
#auth substack password-auth
auth required pam_env.so
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.so
auth include postloginIf you are running SELinux you must install the selinux-policy-devel prerequisite package and also update your policies to include authlogin_duo (run from the location where you built Duo Unix):
sudo make -C pam_duo semodule
sudo make -C pam_duo semodule-install
This allows sshd to make outgoing HTTP connections, which is required for Duo authentication to complete.
Verify that your SELinux configuration has been updated to include Duo:
$ semodule -l | grep duo
The semodule output should include (depending on your specific v7 version):
authlogin_duo 2.1.0
or
authlogin_duo
There are two adjustable tunables:
pam_duo_permit_local_login allows local logins to use pam_duo (off by default)
pam_duo_permit_sshd allows sshd to use pam_duo (on by default)
To turn on and off the tunables:
sudo setsebool -P pam_duo_permit_sshd on/off
sudo setsebool -P pam_duo_permit_local_login on/off
The -P flag causes the boolean to persist through server restarts.
Note: If the nis_enabled tunable is on then regardless of the value of pam_duo_permit_sshd pam_duo will always be able to access Duo via ssh.
System-wide Authentication
/etc/pam.d/system-auth
Before:
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.soAfter:
auth required pam_env.so
# auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_unix.so nullok try_first_pass
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
#%PAM-1.0
auth required pam_sepermit.so
auth include password-authAfter:
#%PAM-1.0
auth required pam_sepermit.so
#auth include password-auth
auth required pam_env.so
auth sufficient pam_duo.so
auth required pam_deny.soIf you are running SELinux you must also update your policies to include authlogin_duo (run from the location where you built Duo Unix):
sudo make -C pam_duo semodule
sudo make -C pam_duo semodule-install
This allows sshd to make outgoing HTTP connections, which is required for Duo authentication to complete.
Verify that your SELinux configuration has been updated to include Duo:
$ semodule -l | grep duo
The semodule output should include:
authlogin_duo 2.1.0
pam_duo_permit_local_login is a tunable that allows users to use pam_duo with local logins (off by default).
To turn on or off tunable:
sudo setsebool -P pam_duo_permit_local_login on/off
The -P flag causes the boolean to persist through server restarts.
The tunable pam_duo_permit_sshd has no effect. The default SELinux policy allows sshd to use tcp ports so turning this tunable off will not block pam_duo via ssh.
IMPORTANT: Red Hat 5 reached full end of life on November 30, 2020. Duo Unix 1.11.0 was the last release with Red Hat 5 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
System-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok
auth requisite pam_deny.so
auth required pam_permit.soAfter:
#auth [success=1 default=ignore] pam_unix.so nullok
auth [success=2 default=ignore] pam_unix.so nullok
auth sufficient /lib64/security/pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth required pam_unix.so
auth sufficient /lib64/security/pam_duo.so
auth required pam_deny.soSystem-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_deny.so
auth required pam_permit.soAfter:
#auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_unix.so nullok_secure
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSystem-wide Authentication
/etc/pam.d/common-auth
Before:
auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_deny.so
auth required pam_permit.soAfter:
#auth [success=1 default=ignore] pam_unix.so nullok_secure
auth requisite pam_unix.so nullok_secure
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
@include common-authAfter:
#@include common-auth
auth [success=1 default=ignore] pam_duo.so
auth requisite pam_deny.so
auth required pam_permit.soIMPORTANT: Debian 8 reached end of life on June 30, 2020. Duo Unix 1.11.4 was the last release with Debian 8 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
IMPORTANT: Debian 7 reached end of life on April 26, 2016. Duo Unix 1.11.1 was the last release with Debian 7 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
IMPORTANT: Debian 6 reached end of life on May 31, 2015. Duo Unix 1.9.18 was the last release with Debian 6 support. Please review the Duo End of Sale, Last Date of Support, and End of Life Policy.
Amazon Linux
Note: Running authconfig after editing your PAM config files will overwrite your changes. Do not run authconfig once you edit your PAM files to add Duo.
If you must preserve your ability to run authconfig in the future, use the symbolic link method described in the "Keeping Custom Settings with authconfig" topic in section 4.1.2 of the Red Hat Security Guide.
System-wide Authentication
/etc/pam.d/system-auth
Before:
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.soAfter:
auth required pam_env.so
# auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_unix.so nullok try_first_pass
auth sufficient pam_duo.so
auth requisite pam_succeed_if.so uid >= 500 quiet
auth required pam_deny.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
auth required pam_sepermit.so
auth substack password-authAfter:
auth required pam_sepermit.so
# auth substack password-auth
auth required pam_duo.soFreeBSD
System-wide Authentication
/etc/pam.d/system
Before:
# auth
auth sufficient pam_opie.so no_warn no_fake_prompts
auth requisite pam_opieaccess.so no_warn allow_local
# auth sufficient pam_krb5.so no_warn try_first_pass
# auth sufficient pam_ssh.so no_warn try_first_pass
auth required pam_unix.so no_warn try_first_pass nullokAfter:
# auth
auth sufficient pam_opie.so no_warn no_fake_prompts
auth requisite pam_opieaccess.so no_warn allow_local
# auth sufficient pam_krb5.so no_warn try_first_pass
# auth sufficient pam_ssh.so no_warn try_first_pass
# auth required pam_unix.so no_warn try_first_pass nullok
auth requisite pam_unix.so no_warn try_first_pass nullok
auth requisite pam_duo.soSSH Public Key Authentication
/etc/pam.d/sshd
Before:
# auth
auth sufficient pam_opie.so no_warn no_fake_prompts
auth requisite pam_opieaccess.so no_warn allow_local
# auth sufficient pam_krb5.so no_warn try_first_pass
# auth sufficient pam_ssh.so no_warn try_first_pass
auth required pam_unix.so no_warn try_first_passAfter:
# auth
auth sufficient pam_opie.so no_warn no_fake_prompts
auth requisite pam_opieaccess.so no_warn allow_local
# auth sufficient pam_krb5.so no_warn try_first_pass
# auth sufficient pam_ssh.so no_warn try_first_pass
# auth required pam_unix.so no_warn try_first_pass
auth required pam_duo.soAIX 7
Edit /etc/security/login.cfg and change this line near the bottom of the file:
auth_type = STD_AUTHto read:
auth_type = PAM_AUTH/etc/pam.conf
Before:
# Authentication
#
authexec auth required pam_aix
dtaction auth required pam_aix
dtsession auth required pam_aix
dtlogin auth required pam_aix
ftp auth required pam_aix
imap auth required pam_aix
login auth required pam_aix
rexec auth required pam_aix
rlogin auth sufficient pam_rhosts_auth
rlogin auth required pam_aix
rsh auth required pam_rhosts_auth
snapp auth required pam_aix
su auth required pam_aix
swrole auth required pam_aix
telnet auth required pam_aix
xdm auth required pam_aix
sshd auth required pam_aix
OTHER auth required pam_prohibitAfter (protecting both su and ssh with Duo):
# Authentication
#
authexec auth required pam_aix
dtaction auth required pam_aix
dtsession auth required pam_aix
dtlogin auth required pam_aix
ftp auth required pam_aix
imap auth required pam_aix
login auth required pam_aix
rexec auth required pam_aix
rlogin auth sufficient pam_rhosts_auth
rlogin auth required pam_aix
rsh auth required pam_rhosts_auth
snapp auth required pam_aix
su auth requisite pam_aix
su auth required /usr/lib/security/pam_duo.so
swrole auth required pam_aix
telnet auth required pam_aix
xdm auth required pam_aix
sshd auth requisite pam_aix
sshd auth required /usr/lib/security/pam_duo.so
OTHER auth required pam_prohibitIf sshd entries do not already exist in /etc/pam.conf then add them after all the other sections:
sshd account required pam_aix
sshd password required pam_aix
sshd session required pam_aixSSH into your system newly configured with pam_duo. If everything is set up correctly and your username doesn't exist in Duo, you'll be given an enrollment link:
Copy the enrollment link and paste it into a web browser to complete Duo's enrollment process.
After enrolling your authentication device with Duo (or if your test user was already enrolled in Duo) you'll receive the prompt for additional verification.
Choose your authentication method and approve the request using your phone or other device.
Need some help? Take a look at the Duo UNIX Frequently Asked Questions (FAQ) page or try searching our Duo UNIX Knowledge Base articles or Community discussions. For further assistance, contact Support.
If you open a support case with Duo, be sure to use the Duo Unix Support Tool to create a tarball you can send to the support engineer to aid with troubleshooting.
