What is a Pluggable Authentication Module (PAM)

What is a Pluggable Authentication Module (PAM)

Programs that grant users access to an area use authentication to confirm each other’s identities. Historically, each program had its own method for doing this.

The Linux Pluggable Authentication Module (PAM) enables systems administrators to set authentication policies for applications that support PAM without recompiling them. Instead, this modular framework utilizes pluggable components.

What is PAM?

A Pluggable Authentication Module (PAM) is a high-level API that integrates multiple low-level authentication schemes into one application programming interface. This enables developers to construct applications requiring authentication regardless of their underlying authentication scheme.

PAM (Physical Address Module) was initially proposed by Sun Microsystems in an Open Software Foundation Request for Comments (RFC) 86.0 of October 1995. It is currently supported on AIX operating systems, DragonFly BSD, FreeBSD, HP-UX, Linux/macOS/NetBSD/Solaris platforms.

The PAM system is designed to be adaptable and scalable, meeting the demands of system administrators and application developers. This flexibility enables system administrators to implement authentication policies tailored to specific risks and technologies.

PAM provides an API to allow applications to function independently from their authentication mechanism by setting up “authentication modules.” Each such application has a corresponding configuration file in /etc/pam.d/, which contains directives specifying which module should be used when asking for authentication from the system.

These directives specify the requested mechanism (auth, account, password, or session), a success check, the path to the module, and any potential arguments. When an authentication request is made, all required PAM modules are executed for that operation; if all are successful, then acceptance of the request is given; otherwise, it is rejected.

When a user logs on to a Linux system, the login process makes an authentication call to libpam and receives the result. The pam_unix module checks local account authentication; other modules may be called upon for password strength checks or time-based access control lists verification.

If the user’s password has expired, a new one can be requested through a call to libpam. If the new password is valid, this request is also passed back onto the login process.

How does PAM work?

PAM is an open-source security framework that offers modules for user authentication and other related tasks. These are dynamically loaded based on application entries in configuration files, then called by the PAM library to perform authentication or other services.

PAM allows a range of applications to be configured with different authentication methods. For instance, biometric authentication, passphrase authentication, or both can all be used. Furthermore, system administrators can create rules that alter password requirements based on the time of day or other factors.

When an application requires authentication, it utilizes the PAM API to invoke a service-specific programming interface (SPI) defined in one or more Pluggable Authentication Modules. It then communicates with this module through a conversation function implemented within the application.

If the module is successful, it returns a success code. Conversely, if it fails, the PAM-API will use that failure status to decide whether to process another module or return to the application.

The success or failure of a module is determined not only by its status but also by the behavior defined for that module in its configuration file. This behavior guides decisions regarding whether to load another module, return to the application or continue processing a successful module.

Furthermore, each module has an encoding that indicates its behavior. This encoding allows the library to translate a module’s success or failure status into an actionable behavior for further processing.

A configuration PAM file lists required and optional modules for each service. A required module must be processed before any other module of its type can be processed, and it must be the initial instance of its kind for the service.

For instance, the login-config file contains at least one entry for each type of authentication. If the login module fails to authenticate, access is immediately denied.

What are the benefits of PAM?

PAM (Privilege Access Management) is a security framework that assists IT and security professionals in managing privileged accounts and passwords. Businesses can utilize PAM to control user and account access, monitor privileged activities, and establish policies to define legitimate user behavior.

PAM also assists companies in meeting data and privacy regulations such as the European General Data Protection Regulation (GDPR), Federal Information Security Management Act (FISMA), and Health Insurance Portability and Accountability Act (HIPAA). Furthermore, it offers a clear audit trail that detects unauthorized access to privileged accounts.

Today’s businesses rely heavily on privileged accounts and systems to keep operations running efficiently while adhering to ever-stricter data privacy regulations. Therefore, IT and security departments must take a proactive approach toward privileged account security to guarantee these accounts remain protected from breaches or hackers.

The two most prevalent threats to privileged accounts are privilege creep and user error, which can grant unsecured access and potentially destroy an entire network or system. Furthermore, a compromised privileged account could be used to impersonate employees or systems and launch cyberattacks without detection for weeks or months.

A privileged account is an administrative or superuser account with the highest privileges on a server. As such, they pose more of a security risk than standard users do, which is why many organizations utilize multiple accounts to safeguard their systems and data.

With PAM, administrators can easily define a privileged account’s permissions and restrict or revoke them. Furthermore, administrators can track privilege elevations, record privileged sessions, and monitor privileged account activity to detect abuse and mitigate risks.

Another advantage of PAM is that it separates authentication processes from programs requiring them. Previously, programs needing to authenticate users would read user information from the /etc/passwd file and then write its results back into it; however, this was inefficient as changes often had to be made to the program’s source code itself.

PAM makes it simple for applications to authenticate users and secure their credentials without modifying the source code. Furthermore, PAM enables you to change your security policy without recompiling your application, making it simpler for application developers to stay abreast of current security standards and eliminating a major roadblock to compliance.

What is the purpose of PAM?

A Pluggable Authentication Module (PAM) is an application programming interface that incorporates various low-level authentication schemes into a high-level authentication scheme. PAM was first introduced by Sun Microsystems and is supported on Linux, AIX OS, NetBSD, and FreeBSD systems.

PAM allows system administrators to choose which authentication policy should be applied for each application or service, enabling complex features like single sign-on, OTP (one-time password), or Kerberos transparently.

PAM is an essential element of a comprehensive privileged access management solution, protecting critical assets from unauthorized entry by decreasing the chance of cyber attackers stealing passwords and escalating privileges.

A proactive PAM program can significantly reduce the risk of credential abuse and data breaches by removing local administrative rights from endpoints. Furthermore, it enables Just-in-Time privileged access. Gartner predicts that enterprises that adopt this strategy will experience 80% fewer security breaches due to privilege abuse by 2024.

Furthermore, a PAM solution can limit user password reuse by automatically changing passwords for users when prompted by the system. This helps stop hackers from gaining access to an account by reusing old passwords, thus decreasing the likelihood of password leaks and data breaches.

When a login process requests PAM for authentication, it uses the appropriate modules to determine whether an account is valid. The result of this check is then passed back to the login process.

PAM grants access to the service if authentication is successful; otherwise, it denies the request.

Therefore, configuring the correct module for each service is essential. This can be accomplished by adding entries to /etc/pam.d/modules file associated with that particular service.

The name and interface must be provided when adding a module to the list. Furthermore, control flags for success and failure should be included; these indicate whether the module is necessary and whether its failure should result in the denial of authentication.

Understanding PAM, Pluggable Authentication Modules in Linux
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