Cyclades AlterPath ACS, Command Reference Manual

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Authentication
Figure 3.1 - Data flow diagram of Linux-PAM
The left of the figure represents the application: Application X. Such an application
interfaces with the Linux-PAM library and knows none of the specifics of its configured
authentication method. The Linux-PAM library (in the center) consults the contents of
the PAM configuration file and loads the modules that are appropriate for Application
X. These modules fall into one of four management groups (lower center) and are
stacked in the order they appear in the configuration file. These modules, when called
by Linux-PAM, perform the various authentication tasks for the application. Textual
information, required from or offered to the user can be exchanged through the use of
the application-supplied conversation function.
The Linux-PAM Configuration Directory
Linux-PAM is designed to provide the system administrator with a great deal of
flexibility in configuring the privilege-granting applications of their system. The local
configuration of those aspects of system security controlled by Linux-PAM is contained
in the directory
/etc/pam.d/ . In this section we discuss the correct syntax of and generic
options respected by entries for the files in this directory.