Etc pam.d system-auth file

Posted: July 29, by Susan Lauber. In a previous article , I described the flow of an application calling PAM libraries for authentication at a very high level. In this article, we will walk through the configuration files for a local sudo command. When using sudo , we switch users and do something. This privilege change requires verification that we are who we say we are and are allowed to perform the given action. The first field in this file identifies a Type of call made to PAM.

Lines of the same type are grouped together. There are four types: auth, account, password, and session. Look at man pam for a description of each type. The second field is known as the ReturnCode. This field lets PAM know how to handle the results of the module test. Return codes indicate whether a test is required or optional. The codes might also be used to indicate the line is not a module test with options but rather the name of another configuration file with additional checks.

A full description of the return codes is found in man pam. The rest of the line contains the module name and options for that module. The options may be different depending on the type of call made. Some modules only perform tests for some types of calls. Use the man page for each module to see examples and learn about the uses and options available. The order of entries within a type of call matters. This is mostly due to how the return codes are processed, but in some cases because of a module action.

When libpam receives a "done" or "die" message, it reports the overall result back to the calling process. The configuration for sudo has several include lines. These lines tell libpam to include all lines of given type from the configuration file specified. There is also a substack option, which is similar in how it includes lines from a given configuration file, but on a "done" or "die," it reports back to the substack instruction instead of the original process calling libpam.

Instead, only the home directory of the user who is about to log in, is mounted. A basic configuration of this feature can be done with YaST. LUKS2 support was added to cryptsetup 2. System limits can be set on a user or group basis in limits. The file allows you to set hard limits, which may not be exceeded, and soft limits, which may be exceeded temporarily. For a list of supported modules, use the pam-config --list-modules command.

Use the pam-config command to maintain your PAM configuration files. Add new modules to your PAM configurations, delete other modules or modify options to these modules. When changing global PAM configuration files, no manual tweaking of the PAM setup for individual applications is required.

Auto-generate a fresh Unix-style PAM configuration. Let pam-config create the simplest possible setup which you can extend later on. The pam-config --create command creates a simple Unix authentication configuration. Add a new authentication method. Adding a new authentication method for example, LDAP to your stack of PAM modules comes down to a simple pam-config --add --ldap command.

Add debugging for test purposes. To make sure the new authentication procedure works as planned, turn on debugging for all PAM-related operations. Find the debugging output in the systemd journal see Chapter 15, journalctl : Query the systemd Journal. Query your setup. Before you finally apply your new PAM setup, check if it contains all the options you wanted to add.

Remove the debug options. Finally, remove the debug option from your setup when you are entirely satisfied with the performance of it. The pam-config --delete --ldap-debug command turns off debugging for LDAP authentication.

In case you had debugging options added for other modules, use similar commands to turn these off. For more information on the pam-config command and the options available, refer to the manual page of pam-config 8. If you prefer to manually create or maintain your PAM configuration files, make sure to disable pam-config for these files. This document comprises everything that the system administrator should know about PAM. It discusses a range of topics, from the syntax of configuration files to the security aspects of PAM.

This document summarizes the topic from the developer's point of view, with information about how to write standard-compliant PAM modules. This document comprises everything needed by an application developer who wants to use the PAM libraries. PAM in general and the individual modules come with manual pages that provide a good overview of the functionality of all the components. Contents Contents. Edit source. A module stack with of one or more PAM modules.

TYPE Declares the type of the service. PAM knows about four different types of modules: auth Check the user's authenticity, traditionally by querying a password.

Note: Bit and Bit Mixed Installations When using a bit operating system, it is possible to also include a runtime environment for bit applications. Example 2. This module performs any necessary account verification. It then tests the newly created password to see whether it can easily be determined by a dictionary-based password cracking program.

The argument shadow tells the module to create shadow passwords when updating a user's password. The argument nullok instructs the module to allow the user to change their password from a blank password, otherwise a null password is treated as an account lock. This argument tells the module not to prompt the user for a new password. Instead, it accepts any password that was recorded by a previous password module. It can be supplemented by stacking it with other session modules for more functionality.