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diff --git a/doc/adg/Linux-PAM_ADG.xml b/doc/adg/Linux-PAM_ADG.xml new file mode 100644 index 00000000..8f5ec115 --- /dev/null +++ b/doc/adg/Linux-PAM_ADG.xml @@ -0,0 +1,779 @@ +<?xml version='1.0' encoding='UTF-8'?> +<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" + "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd"> +<book id="adg"> + <bookinfo> + <title>The Linux-PAM Application Developers' Guide</title> + <authorgroup> + <author> + <firstname>Andrew G.</firstname> + <surname>Morgan</surname> + <email>morgan@kernel.org</email> + </author> + <author> + <firstname>Thorsten</firstname> + <surname>Kukuk</surname> + <email>kukuk@thkukuk.de</email> + </author> + </authorgroup> + <releaseinfo>Version 1.0, 3. April 2008</releaseinfo> + <abstract> + <para> + This manual documents what an application developer needs to know + about the <emphasis remap='B'>Linux-PAM</emphasis> library. It + describes how an application might use the + <emphasis remap='B'>Linux-PAM</emphasis> library to authenticate + users. In addition it contains a description of the funtions + to be found in <filename>libpam_misc</filename> library, that can + be used in general applications. Finally, it contains some comments + on PAM related security issues for the application developer. + </para> + </abstract> + </bookinfo> + + <chapter id="adg-introduction"> + <title>Introduction</title> + <section id="adg-introduction-description"> + <title>Description</title> + <para> + <emphasis remap='B'>Linux-PAM</emphasis> + (Pluggable Authentication Modules for Linux) is a library that enables + the local system administrator to choose how individual applications + authenticate users. For an overview of the + <emphasis remap='B'>Linux-PAM</emphasis> library see the + <emphasis>Linux-PAM System Administrators' Guide</emphasis>. + </para> + <para> + It is the purpose of the <emphasis remap='B'>Linux-PAM</emphasis> + project to liberate the development of privilege granting software + from the development of secure and appropriate authentication schemes. + This is accomplished by providing a documented library of functions + that an application may use for all forms of user authentication + management. This library dynamically loads locally configured + authentication modules that actually perform the authentication tasks. + </para> + <para> + From the perspective of an application developer the information + contained in the local configuration of the PAM library should not be + important. Indeed it is intended that an application treat the + functions documented here as a 'black box' that will deal with all + aspects of user authentication. 'All aspects' includes user + verification, account management, session initialization/termination + and also the resetting of passwords + (<emphasis>authentication tokens</emphasis>). + </para> + </section> + + <section id="adg-introduction-synopsis"> + <title>Synopsis</title> + <para> + For general applications that wish to use the services provided by + <emphasis remap='B'>Linux-PAM</emphasis> the following is a summary + of the relevant linking information: + <programlisting> +#include <security/pam_appl.h> + +cc -o application .... -lpam + </programlisting> + </para> + <para> + In addition to <command>libpam</command>, there is a library of + miscellaneous functions that make the job of writing + <emphasis>PAM-aware</emphasis> applications easier (this library is not + covered in the DCE-RFC for PAM and is specific to the Linux-PAM + distribution): + <programlisting> +#include <security/pam_appl.h> +#include <security/pam_misc.h> + +cc -o application .... -lpam -lpam_misc + </programlisting> + </para> + </section> + </chapter> + + <chapter id="adg-overview"> + <title>Overview</title> + <para> + Most service-giving applications are restricted. In other words, + their service is not available to all and every prospective client. + Instead, the applying client must jump through a number of hoops to + convince the serving application that they are authorized to obtain + service. + </para> + <para> + The process of <emphasis>authenticating</emphasis> a client is what + PAM is designed to manage. In addition to authentication, PAM provides + account management, credential management, session management and + authentication-token (password changing) management services. It is + important to realize when writing a PAM based application that these + services are provided in a manner that is + <emphasis remap='B'>transparent</emphasis> to the application. That is + to say, when the application is written, no assumptions can be made + about <emphasis>how</emphasis> the client will be authenticated. + </para> + <para> + The process of authentication is performed by the PAM library via a + call to <function>pam_authenticate()</function>. The return value + of this function will indicate whether a named client (the + <emphasis>user</emphasis>) has been authenticated. If the PAM library + needs to prompt the user for any information, such as their + <emphasis>name</emphasis> or a <emphasis>password</emphasis> + then it will do so. If the PAM library is configured to authenticate + the user using some silent protocol, it will do this too. (This + latter case might be via some hardware interface for example.) + </para> + <para> + It is important to note that the application must leave all decisions + about when to prompt the user at the discretion of the PAM library. + </para> + <para> + The PAM library, however, must work equally well for different styles + of application. Some applications, like the familiar + <command>login</command> and <command>passwd</command> are terminal + based applications, exchanges of information with the client in + these cases is as plain text messages. Graphically based applications, + however, have a more sophisticated interface. They generally interact + with the user via specially constructed dialogue boxes. Additionally, + network based services require that text messages exchanged with the + client are specially formatted for automated processing: one such + example is <command>ftpd</command> which prefixes each exchanged + message with a numeric identifier. + </para> + <para> + The presentation of simple requests to a client is thus something very + dependent on the protocol that the serving application will use. In + spite of the fact that PAM demands that it drives the whole + authentication process, it is not possible to leave such protocol + subtleties up to the PAM library. To overcome this potential problem, + the application provides the PAM library with a + <emphasis>conversation</emphasis> function. This function is called + from <emphasis>within</emphasis> the PAM library and enables the PAM + to directly interact with the client. The sorts of things that this + conversation function must be able to do are prompt the user with + text and/or obtain textual input from the user for processing by the + PAM library. The details of this function are provided in a later + section. + </para> + <para> + For example, the conversation function may be called by the PAM + library with a request to prompt the user for a password. Its job is + to reformat the prompt request into a form that the client will + understand. In the case of <command>ftpd</command>, this might involve + prefixing the string with the number <command>331</command> and sending + the request over the network to a connected client. The conversation + function will then obtain any reply and, after extracting the typed + password, will return this string of text to the PAM library. Similar + concerns need to be addressed in the case of an X-based graphical + server. + </para> + <para> + There are a number of issues that need to be addressed when one is + porting an existing application to become PAM compliant. A section + below has been devoted to this: Porting legacy applications. + </para> + <para> + Besides authentication, PAM provides other forms of management. + Session management is provided with calls to + <function>pam_open_session()</function> and + <function>pam_close_session()</function>. What these functions + actually do is up to the local administrator. But typically, they + could be used to log entry and exit from the system or for mounting + and unmounting the user's home directory. If an application provides + continuous service for a period of time, it should probably call + these functions, first open after the user is authenticated and then + close when the service is terminated. + </para> + <para> + Account management is another area that an application developer + should include with a call to <function>pam_acct_mgmt()</function>. + This call will perform checks on the good health of the user's account + (has it expired etc.). One of the things this function may check is + whether the user's authentication token has expired - in such a case the + application may choose to attempt to update it with a call to + <function>pam_chauthtok()</function>, although some applications + are not suited to this task (<command>ftp</command> for example) + and in this case the application should deny access to the user. + </para> + <para> + PAM is also capable of setting and deleting the users credentials with + the call <function>pam_setcred()</function>. This function should + always be called after the user is authenticated and before service + is offered to the user. By convention, this should be the last call + to the PAM library before the PAM session is opened. What exactly a + credential is, is not well defined. However, some examples are given + in the glossary below. + </para> + </chapter> + + <chapter id="adg-interface"> + <title> + The public interface to <emphasis remap='B'>Linux-PAM</emphasis> + </title> + <para> + Firstly, the relevant include file for the + <emphasis remap='B'>Linux-PAM</emphasis> library is + <function><security/pam_appl.h></function>. + It contains the definitions for a number of functions. After + listing these functions, we collect some guiding remarks for + programmers. + </para> + <section id="adg-interface-by-app-expected"> + <title>What can be expected by the application</title> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_start.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_end.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_set_item.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_get_item.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_strerror.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_fail_delay.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_authenticate.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_setcred.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_acct_mgmt.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_chauthtok.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_open_session.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_close_session.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_putenv.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_getenv.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_getenvlist.xml"/> + </section> + <section id="adg-interface-of-app-expected"> + <title>What is expected of an application</title> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_conv.xml"/> + </section> + <section id="adg-interface-programming-notes"> + <title>Programming notes</title> + <para> + Note, all of the authentication service function calls accept the + token <emphasis remap='B'>PAM_SILENT</emphasis>, which instructs + the modules to not send messages to the application. This token + can be logically OR'd with any one of the permitted tokens specific + to the individual function calls. + <emphasis remap='B'>PAM_SILENT</emphasis> does not override the + prompting of the user for passwords etc., it only stops informative + messages from being generated. + </para> + </section> + </chapter> + + <chapter id="adg-security"> + <title> + Security issues of <emphasis remap='B'>Linux-PAM</emphasis> + </title> + <para> + PAM, from the perspective of an application, is a convenient API for + authenticating users. PAM modules generally have no increased + privilege over that possessed by the application that is making use of + it. For this reason, the application must take ultimate responsibility + for protecting the environment in which PAM operates. + </para> + <para> + A poorly (or maliciously) written application can defeat any + <emphasis remap='B'>Linux-PAM</emphasis> module's authentication + mechanisms by simply ignoring it's return values. It is the + applications task and responsibility to grant privileges and access + to services. The <emphasis remap='B'>Linux-PAM</emphasis> library + simply assumes the responsibility of <emphasis>authenticating</emphasis> + the user; ascertaining that the user <emphasis>is</emphasis> who they + say they are. Care should be taken to anticipate all of the documented + behavior of the <emphasis remap='B'>Linux-PAM</emphasis> library + functions. A failure to do this will most certainly lead to a future + security breach. + </para> + + <section id="adg-security-library-calls"> + <title>Care about standard library calls</title> + <para> + In general, writers of authorization-granting applications should + assume that each module is likely to call any or + <emphasis>all</emphasis> 'libc' functions. For 'libc' functions + that return pointers to static/dynamically allocated structures + (ie. the library allocates the memory and the user is not expected + to '<function>free()</function>' it) any module call to this + function is likely to corrupt a pointer previously + obtained by the application. The application programmer should + either re-call such a 'libc' function after a call to the + <emphasis remap='B'>Linux-PAM</emphasis> library, or copy the + structure contents to some safe area of memory before passing + control to the <emphasis remap='B'>Linux-PAM</emphasis> library. + </para> + <para> + Two important function classes that fall into this category are + <citerefentry> + <refentrytitle>getpwnam</refentrytitle><manvolnum>3</manvolnum> + </citerefentry> and <citerefentry> + <refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>. + </para> + </section> + + <section id="adg-security-service-name"> + <title>Choice of a service name</title> + <para> + When picking the <emphasis>service-name</emphasis> that + corresponds to the first entry in the + <emphasis remap='B'>Linux-PAM</emphasis> configuration file, + the application programmer should <emphasis>avoid</emphasis> + the temptation of choosing something related to + <varname>argv[0]</varname>. It is a trivial matter for any user + to invoke any application on a system under a different name and + this should not be permitted to cause a security breach. + </para> + <para> + In general, this is always the right advice if the program is + setuid, or otherwise more privileged than the user that invokes + it. In some cases, avoiding this advice is convenient, but as an + author of such an application, you should consider well the ways + in which your program will be installed and used. (Its often the + case that programs are not intended to be setuid, but end up + being installed that way for convenience. If your program falls + into this category, don't fall into the trap of making this mistake.) + </para> + <para> + To invoke some <emphasis>target</emphasis> application by + another name, the user may symbolically link the target application + with the desired name. To be precise all the user need do is, + <command>ln -s /target/application ./preferred_name</command> + and then run <command>./preferred_name</command>. + </para> + <para> + By studying the <emphasis remap='B'>Linux-PAM</emphasis> + configuration file(s), an attacker can choose the + <command>preferred_name</command> to be that of a service enjoying + minimal protection; for example a game which uses + <emphasis remap='B'>Linux-PAM</emphasis> to restrict access to + certain hours of the day. If the service-name were to be linked + to the filename under which the service was invoked, it + is clear that the user is effectively in the position of + dictating which authentication scheme the service uses. Needless + to say, this is not a secure situation. + </para> + <para> + The conclusion is that the application developer should carefully + define the service-name of an application. The safest thing is to + make it a single hard-wired name. + </para> + </section> + + <section id="adg-security-conv-function"> + <title>The conversation function</title> + <para> + Care should be taken to ensure that the <function>conv()</function> + function is robust. Such a function is provided in the library + <command>libpam_misc</command> (see + <link linkend="adg-libpam-functions">below</link>). + </para> + </section> + + <section id="adg-security-usre-identity"> + <title>The identity of the user</title> + <para> + The <emphasis remap='B'>Linux-PAM</emphasis> modules will need + to determine the identity of the user who requests a service, + and the identity of the user who grants the service. These two + users will seldom be the same. Indeed there is generally a third + user identity to be considered, the new (assumed) identity of + the user once the service is granted. + </para> + <para> + The need for keeping tabs on these identities is clearly an + issue of security. One convention that is actively used by + some modules is that the identity of the user requesting a + service should be the current <emphasis>UID</emphasis> + (userid) of the running process; the identity of the + privilege granting user is the <emphasis>EUID</emphasis> + (effective userid) of the running process; the identity of + the user, under whose name the service will be executed, is + given by the contents of the <emphasis>PAM_USER</emphasis> + <citerefentry> + <refentrytitle>pam_get_item</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>. Note, modules can change the values of + <emphasis>PAM_USER</emphasis> and <emphasis>PAM_RUSER</emphasis> + during any of the <function>pam_*()</function> library calls. + For this reason, the application should take care to use the + <function>pam_get_item()</function> every time it wishes to + establish who the authenticated user is (or will currently be). + </para> + <para> + For network-serving databases and other applications that provide + their own security model (independent of the OS kernel) the above + scheme is insufficient to identify the requesting user. + </para> + <para> + A more portable solution to storing the identity of the requesting + user is to use the <emphasis>PAM_RUSER</emphasis> <citerefentry> + <refentrytitle>pam_get_item</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>. The application should supply this value before + attempting to authenticate the user with + <function>pam_authenticate()</function>. How well this name can be + trusted will ultimately be at the discretion of the local + administrator (who configures PAM for your application) and a + selected module may attempt to override the value where it can + obtain more reliable data. If an application is unable to determine + the identity of the requesting entity/user, it should not call + <citerefentry> + <refentrytitle>pam_set_item</refentrytitle><manvolnum>3</manvolnum> + </citerefentry> to set <emphasis>PAM_RUSER</emphasis>. + </para> + <para> + In addition to the <emphasis>PAM_RUSER</emphasis> item, the + application should supply the <emphasis>PAM_RHOST</emphasis> + (<emphasis>requesting host</emphasis>) item. As a general rule, + the following convention for its value can be assumed: + NULL = unknown; localhost = invoked directly from the local system; + <emphasis>other.place.xyz</emphasis> = some component of the + user's connection originates from this remote/requesting host. At + present, PAM has no established convention for indicating whether + the application supports a trusted path to communication from + this host. + </para> + </section> + + <section id="adg-security-resources"> + <title>Sufficient resources</title> + <para> + Care should be taken to ensure that the proper execution of an + application is not compromised by a lack of system resources. If an + application is unable to open sufficient files to perform its service, + it should fail gracefully, or request additional resources. + Specifically, the quantities manipulated by the <citerefentry> + <refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum> + </citerefentry> family of commands should be taken into consideration. + </para> + <para> + This is also true of conversation prompts. The application should not + accept prompts of arbitrary length with out checking for resource + allocation failure and dealing with such extreme conditions gracefully + and in a mannor that preserves the PAM API. Such tolerance may be + especially important when attempting to track a malicious adversary. + </para> + </section> + </chapter> + + <chapter id='adg-libpam_misc'> + <title>A library of miscellaneous helper functions</title> + <para> + To aid the work of the application developer a library of + miscellaneous functions is provided. It is called + <command>libpam_miscy</command>, and contains a text based + conversation function, and routines for enhancing the standard + PAM-environment variable support. + </para> + <para> + The functions, structures and macros, made available by this + library can be defined by including + <function><security/pam_misc.h></function>. It should be + noted that this library is specific to + <emphasis remap='B'>Linux-PAM</emphasis> and is not referred to in + the defining DCE-RFC (see <link linkend="adg-see-also">See also</link>) + below. + </para> + <section id='adg-libpam-functions'> + <title>Functions supplied</title> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_misc_conv.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_misc_paste_env.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_misc_drop_env.xml"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" + href="pam_misc_setenv.xml"/> + </section> + </chapter> + + <chapter id='adg-porting'> + <title>Porting legacy applications</title> + <para> + The point of PAM is that the application is not supposed to + have any idea how the attached authentication modules will choose + to authenticate the user. So all they can do is provide a conversation + function that will talk directly to the user(client) on the modules' + behalf. + </para> + <para> + Consider the case that you plug a retinal scanner into the login + program. In this situation the user would be prompted: "please look + into the scanner". No username or password would be needed - all this + information could be deduced from the scan and a database lookup. The + point is that the retinal scanner is an ideal task for a "module". + </para> + <para> + While it is true that a pop-daemon program is designed with the POP + protocol in mind and no-one ever considered attaching a retinal + scanner to it, it is also the case that the "clean" PAM'ification of + such a daemon would allow for the possibility of a scanner module + being be attached to it. The point being that the "standard" + pop-authentication protocol(s) [which will be needed to satisfy + inflexible/legacy clients] would be supported by inserting an + appropriate pam_qpopper module(s). However, having rewritten popd + once in this way any new protocols can be implemented in-situ. + </para> + <para> + One simple test of a ported application would be to insert the + <command>pam_permit</command> module and see if the application + demands you type a password... In such a case, <command>xlock</command> + would fail to lock the terminal - or would at best be a screen-saver, + ftp would give password free access to all etc.. Neither of + these is a very secure thing to do, but they do illustrate how + much flexibility PAM puts in the hands of the local admin. + </para> + <para> + The key issue, in doing things correctly, is identifying what is part + of the authentication procedure (how many passwords etc..) the + exchange protocol (prefixes to prompts etc., numbers like 331 in the + case of ftpd) and what is part of the service that the application + delivers. PAM really needs to have total control in the + authentication "procedure", the conversation function should only + deal with reformatting user prompts and extracting responses from raw + input. + </para> + </chapter> + + <chapter id='adg-glossary'> + <title>Glossary of PAM related terms</title> + <para> + The following are a list of terms used within this document. + </para> + <variablelist> + <varlistentry> + <term>Authentication token</term> + <listitem> + <para> + Generally, this is a password. However, a user can authenticate + him/herself in a variety of ways. Updating the user's + authentication token thus corresponds to + <emphasis>refreshing</emphasis> the object they use to + authenticate themself with the system. The word password is + avoided to keep open the possibility that the authentication + involves a retinal scan or other non-textual mode of + challenge/response. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>Credentials</term> + <listitem> + <para> + Having successfully authenticated the user, PAM is able to + establish certain characteristics/attributes of the user. + These are termed <emphasis>credentials</emphasis>. Examples + of which are group memberships to perform privileged tasks + with, and <emphasis>tickets</emphasis> in the form of + environment variables etc. . Some user-credentials, such as + the user's UID and GID (plus default group memberships) are + not deemed to be PAM-credentials. It is the responsibility + of the application to grant these directly. + </para> + </listitem> + </varlistentry> + </variablelist> + </chapter> + + <chapter id='adg-example'> + <title>An example application</title> + <para> + To get a flavor of the way a <emphasis remap='B'>Linux-PAM</emphasis> + application is written we include the following example. It prompts + the user for their password and indicates whether their account + is valid on the standard output, its return code also indicates + the success (<returnvalue>0</returnvalue> for success; + <returnvalue>1</returnvalue> for failure). + </para> + <programlisting><![CDATA[ +/* + This program was contributed by Shane Watts + [modifications by AGM and kukuk] + + You need to add the following (or equivalent) to the + /etc/pam.d/check_user file: + # check authorization + auth required pam_unix.so + account required pam_unix.so + */ + +#include <security/pam_appl.h> +#include <security/pam_misc.h> +#include <stdio.h> + +static struct pam_conv conv = { + misc_conv, + NULL +}; + +int main(int argc, char *argv[]) +{ + pam_handle_t *pamh=NULL; + int retval; + const char *user="nobody"; + + if(argc == 2) { + user = argv[1]; + } + + if(argc > 2) { + fprintf(stderr, "Usage: check_user [username]\n"); + exit(1); + } + + retval = pam_start("check_user", user, &conv, &pamh); + + if (retval == PAM_SUCCESS) + retval = pam_authenticate(pamh, 0); /* is user really user? */ + + if (retval == PAM_SUCCESS) + retval = pam_acct_mgmt(pamh, 0); /* permitted access? */ + + /* This is where we have been authorized or not. */ + + if (retval == PAM_SUCCESS) { + fprintf(stdout, "Authenticated\n"); + } else { + fprintf(stdout, "Not Authenticated\n"); + } + + if (pam_end(pamh,retval) != PAM_SUCCESS) { /* close Linux-PAM */ + pamh = NULL; + fprintf(stderr, "check_user: failed to release authenticator\n"); + exit(1); + } + + return ( retval == PAM_SUCCESS ? 0:1 ); /* indicate success */ +} +]]> + </programlisting> + </chapter> + + <chapter id='adg-files'> + <title>Files</title> + <variablelist> + <varlistentry> + <term><filename>/usr/include/security/pam_appl.h</filename></term> + <listitem> + <para> + Header file with interfaces for + <emphasis remap='B'>Linux-PAM</emphasis> applications. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>/usr/include/security/pam_misc.h</filename></term> + <listitem> + <para> + Header file for useful library functions for making + applications easier to write. + </para> + </listitem> + </varlistentry> + </variablelist> + </chapter> + + <chapter id="adg-see-also"> + <title>See also</title> + <itemizedlist> + <listitem> + <para> + The Linux-PAM System Administrators' Guide. + </para> + </listitem> + <listitem> + <para> + The Linux-PAM Module Writers' Guide. + </para> + </listitem> + <listitem> + <para> + The V. Samar and R. Schemers (SunSoft), ``UNIFIED LOGIN WITH + PLUGGABLE AUTHENTICATION MODULES'', Open Software Foundation + Request For Comments 86.0, October 1995. + </para> + </listitem> + </itemizedlist> + </chapter> + + <chapter id='adg-author'> + <title>Author/acknowledgments</title> + <para> + This document was written by Andrew G. Morgan (morgan@kernel.org) + with many contributions from + Chris Adams, Peter Allgeyer, Tim Baverstock, Tim Berger, Craig S. Bell, + Derrick J. Brashear, Ben Buxton, Seth Chaiklin, Oliver Crow, Chris Dent, + Marc Ewing, Cristian Gafton, Emmanuel Galanos, Brad M. Garcia, + Eric Hester, Roger Hu, Eric Jacksch, Michael K. Johnson, David Kinchlea, + Olaf Kirch, Marcin Korzonek, Thorsten Kukuk, Stephen Langasek, + Nicolai Langfeldt, Elliot Lee, Luke Kenneth Casson Leighton, + Al Longyear, Ingo Luetkebohle, Marek Michalkiewicz, Robert Milkowski, + Aleph One, Martin Pool, Sean Reifschneider, Jan Rekorajski, Erik Troan, + Theodore Ts'o, Jeff Uphoff, Myles Uyema, Savochkin Andrey Vladimirovich, + Ronald Wahl, David Wood, John Wilmes, Joseph S. D. Yao + and Alex O. Yuriev. + </para> + <para> + Thanks are also due to Sun Microsystems, especially to Vipin Samar and + Charlie Lai for their advice. At an early stage in the development of + <emphasis remap='B'>Linux-PAM</emphasis>, Sun graciously made the + documentation for their implementation of PAM available. This act + greatly accelerated the development of + <emphasis remap='B'>Linux-PAM</emphasis>. + </para> + </chapter> + + <chapter id='adg-copyright'> + <title>Copyright information for this document</title> + <programlisting> +Copyright (c) 2006 Thorsten Kukuk <kukuk@thkukuk.de> +Copyright (c) 1996-2002 Andrew G. Morgan <morgan@kernel.org> + </programlisting> + <para> + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions are + met: + </para> + <programlisting> +1. Redistributions of source code must retain the above copyright + notice, and the entire permission notice in its entirety, + including the disclaimer of warranties. + +2. Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + +3. The name of the author may not be used to endorse or promote + products derived from this software without specific prior + written permission. + </programlisting> + <para> + Alternatively, this product may be distributed under the terms of + the GNU General Public License (GPL), in which case the provisions + of the GNU GPL are required instead of the above restrictions. + (This clause is necessary due to a potential bad interaction between + the GNU GPL and the restrictions contained in a BSD-style copyright.) + </para> + <programlisting> +THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED +WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF +MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, +INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS +OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR +TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE +USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH + </programlisting> + </chapter> +</book> |