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diff --git a/doc/man/pam.conf-syntax.xml b/doc/man/pam.conf-syntax.xml new file mode 100644 index 0000000..5112f93 --- /dev/null +++ b/doc/man/pam.conf-syntax.xml @@ -0,0 +1,427 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" + "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"> + +<section id='pam.conf-syntax'> + <para> + The syntax of the <filename>/etc/pam.conf</filename> + configuration file is as follows. The file is made up of a list + of rules, each rule is typically placed on a single line, + but may be extended with an escaped end of line: `\<LF>'. + Comments are preceded with `#' marks and extend to the next end of + line. + </para> + + <para> + The format of each rule is a space separated collection of tokens, + the first three being case-insensitive: + </para> + + <para> + <emphasis remap='B'> service type control module-path module-arguments</emphasis> + </para> + + <para> + The syntax of files contained in the <filename>/etc/pam.d/</filename> + directory, are identical except for the absence of any + <emphasis>service</emphasis> field. In this case, the + <emphasis>service</emphasis> is the name of the file in the + <filename>/etc/pam.d/</filename> directory. This filename must be + in lower case. + </para> + + <para> + An important feature of <emphasis>PAM</emphasis>, is that a + number of rules may be <emphasis>stacked</emphasis> to combine + the services of a number of PAMs for a given authentication task. + </para> + + <para> + The <emphasis>service</emphasis> is typically the familiar name of + the corresponding application: <emphasis>login</emphasis> and + <emphasis>su</emphasis> are good examples. The + <emphasis>service</emphasis>-name, <emphasis>other</emphasis>, + is reserved for giving <emphasis>default</emphasis> rules. + Only lines that mention the current service (or in the absence + of such, the <emphasis>other</emphasis> entries) will be associated + with the given service-application. + </para> + + <para> + The <emphasis>type</emphasis> is the management group that the rule + corresponds to. It is used to specify which of the management groups + the subsequent module is to be associated with. Valid entries are: + </para> + <variablelist> + <varlistentry> + <term>account</term> + <listitem> + <para> + this module type performs non-authentication based account + management. It is typically used to restrict/permit access + to a service based on the time of day, currently available + system resources (maximum number of users) or perhaps the + location of the applicant user -- 'root' login only on the + console. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>auth</term> + <listitem> + <para> + this module type provides two aspects of authenticating + the user. Firstly, it establishes that the user is who they + claim to be, by instructing the application to prompt the user + for a password or other means of identification. Secondly, the + module can grant group membership or other privileges through + its credential granting properties. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>password</term> + <listitem> + <para> + this module type is required for updating the authentication + token associated with the user. Typically, there is one module + for each 'challenge/response' based authentication (auth) type. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>session</term> + <listitem> + <para> + this module type is associated with doing things that need to + be done for the user before/after they can be given service. + Such things include the logging of information concerning the + opening/closing of some data exchange with a user, mounting + directories, etc. + </para> + </listitem> + </varlistentry> + </variablelist> + <para> + If the <emphasis>type</emphasis> value from the list above is prepended + with a <emphasis>-</emphasis> character the PAM library will not log to + the system log if it is not possible to load the module because it is + missing in the system. This can be useful especially for modules which + are not always installed on the system and are not required for correct + authentication and authorization of the login session. + </para> + + <para> + The third field, <emphasis>control</emphasis>, indicates the + behavior of the PAM-API should the module fail to succeed in its + authentication task. There are two types of syntax for this control + field: the simple one has a single simple keyword; the more + complicated one involves a square-bracketed selection of + <emphasis>value=action</emphasis> pairs. + </para> + + <para> + For the simple (historical) syntax valid <emphasis>control</emphasis> + values are: + </para> + <variablelist> + <varlistentry> + <term>required</term> + <listitem> + <para> + failure of such a PAM will ultimately lead to the PAM-API + returning failure but only after the remaining + <emphasis>stacked</emphasis> modules (for this + <emphasis>service</emphasis> and <emphasis>type</emphasis>) + have been invoked. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>requisite</term> + <listitem> + <para> + like <emphasis>required</emphasis>, however, in the case that + such a module returns a failure, control is directly returned + to the application or to the superior PAM stack. + The return value is that associated with + the first required or requisite module to fail. Note, this flag + can be used to protect against the possibility of a user getting + the opportunity to enter a password over an unsafe medium. It is + conceivable that such behavior might inform an attacker of valid + accounts on a system. This possibility should be weighed against + the not insignificant concerns of exposing a sensitive password + in a hostile environment. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>sufficient</term> + <listitem> + <para> + if such a module succeeds and no prior <emphasis>required</emphasis> + module has failed the PAM framework returns success to + the application or to the superior PAM stack immediately without + calling any further modules in the stack. A failure of a + <emphasis>sufficient</emphasis> module is ignored and processing + of the PAM module stack continues unaffected. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>optional</term> + <listitem> + <para> + the success or failure of this module is only important if + it is the only module in the stack associated with this + <emphasis>service</emphasis>+<emphasis>type</emphasis>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>include</term> + <listitem> + <para> + include all lines of given type from the configuration + file specified as an argument to this control. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>substack</term> + <listitem> + <para> + include all lines of given type from the configuration + file specified as an argument to this control. This differs from + <emphasis>include</emphasis> in that evaluation of the + <emphasis>done</emphasis> and <emphasis>die</emphasis> actions + in a substack does not cause skipping the rest of the complete + module stack, but only of the substack. Jumps in a substack + also can not make evaluation jump out of it, and the whole substack + is counted as one module when the jump is done in a parent stack. + The <emphasis>reset</emphasis> action will reset the state of a + module stack to the state it was in as of beginning of the substack + evaluation. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + For the more complicated syntax valid <emphasis>control</emphasis> + values have the following form: + </para> + <programlisting> + [value1=action1 value2=action2 ...] + </programlisting> + + <para> + Where <emphasis>valueN</emphasis> corresponds to the return code + from the function invoked in the module for which the line is + defined. It is selected from one of these: + <emphasis>success</emphasis>, <emphasis>open_err</emphasis>, + <emphasis>symbol_err</emphasis>, <emphasis>service_err</emphasis>, + <emphasis>system_err</emphasis>, <emphasis>buf_err</emphasis>, + <emphasis>perm_denied</emphasis>, <emphasis>auth_err</emphasis>, + <emphasis>cred_insufficient</emphasis>, + <emphasis>authinfo_unavail</emphasis>, + <emphasis>user_unknown</emphasis>, <emphasis>maxtries</emphasis>, + <emphasis>new_authtok_reqd</emphasis>, + <emphasis>acct_expired</emphasis>, <emphasis>session_err</emphasis>, + <emphasis>cred_unavail</emphasis>, <emphasis>cred_expired</emphasis>, + <emphasis>cred_err</emphasis>, <emphasis>no_module_data</emphasis>, + <emphasis>conv_err</emphasis>, <emphasis>authtok_err</emphasis>, + <emphasis>authtok_recover_err</emphasis>, + <emphasis>authtok_lock_busy</emphasis>, + <emphasis>authtok_disable_aging</emphasis>, + <emphasis>try_again</emphasis>, <emphasis>ignore</emphasis>, + <emphasis>abort</emphasis>, <emphasis>authtok_expired</emphasis>, + <emphasis>module_unknown</emphasis>, <emphasis>bad_item</emphasis>, + <emphasis>conv_again</emphasis>, <emphasis>incomplete</emphasis>, + and <emphasis>default</emphasis>. + </para> + <para> + The last of these, <emphasis>default</emphasis>, implies 'all + <emphasis>valueN</emphasis>'s not mentioned explicitly. Note, the + full list of PAM errors is available in + <filename>/usr/include/security/_pam_types.h</filename>. The + <emphasis>actionN</emphasis> can take one of the following forms: + </para> + <variablelist> + <varlistentry> + <term>ignore</term> + <listitem> + <para> + when used with a stack of modules, the module's return + status will not contribute to the return code the application + obtains. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>bad</term> + <listitem> + <para> + this action indicates that the return code should be thought + of as indicative of the module failing. If this module is the + first in the stack to fail, its status value will be used for + that of the whole stack. This is the default action for + all return codes. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>die</term> + <listitem> + <para> + equivalent to <emphasis>bad</emphasis> with the side effect of + terminating the module stack and PAM immediately returning to + the application. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ok</term> + <listitem> + <para> + this tells PAM that the administrator thinks this return code + should contribute directly to the return code of the full + stack of modules. In other words, if the former state of the + stack would lead to a return of <emphasis>PAM_SUCCESS</emphasis>, + the module's return code will override this value. Note, if + the former state of the stack holds some value that is + indicative of a modules failure, this 'ok' value will not be + used to override that value. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>done</term> + <listitem> + <para> + equivalent to <emphasis>ok</emphasis> with the side effect of + terminating the module stack and PAM immediately returning to the + application unless there was a non-ignored module failure before. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>N (an unsigned integer)</term> + <listitem> + <para> + jump over the next N modules in the stack. + Note that N equal to 0 is not allowed, + it would be treated as <emphasis>ignore</emphasis> in such case. + The side effect depends on the PAM function call: + for <emphasis>pam_authenticate</emphasis>, + <emphasis>pam_acct_mgmt</emphasis>, + <emphasis>pam_chauthtok</emphasis>, and + <emphasis>pam_open_session</emphasis> + it is <emphasis>ignore</emphasis>; + for <emphasis>pam_setcred</emphasis> and + <emphasis>pam_close_session</emphasis> it is + one of <emphasis>ignore</emphasis>, <emphasis>ok</emphasis>, + or <emphasis>bad</emphasis> depending on the module's return value. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>reset</term> + <listitem> + <para> + clear all memory of the state of the module stack and + start again with the next stacked module. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + If a return code's action is not specifically defined via a + <emphasis>valueN</emphasis> token, and the + <emphasis>default</emphasis> value is not specified, that return + code's action defaults to <emphasis>bad</emphasis>. + </para> + + <para> + Each of the four keywords: required; requisite; sufficient; and + optional, have an equivalent expression in terms of the [...] + syntax. They are as follows: + </para> + <variablelist> + <varlistentry> + <term>required</term> + <listitem> + <para> + [success=ok new_authtok_reqd=ok ignore=ignore default=bad] + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>requisite</term> + <listitem> + <para> + [success=ok new_authtok_reqd=ok ignore=ignore default=die] + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>sufficient</term> + <listitem> + <para> + [success=done new_authtok_reqd=done default=ignore] + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>optional</term> + <listitem> + <para> + [success=ok new_authtok_reqd=ok default=ignore] + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + <emphasis>module-path</emphasis> is either the full filename + of the PAM to be used by the application (it begins with a '/'), + or a relative pathname from the default module location: + <filename>/lib/security/</filename> or + <filename>/lib64/security/</filename>, depending on the architecture. + </para> + + <para> + <emphasis>module-arguments</emphasis> are a space separated list + of tokens that can be used to modify the specific behavior of the + given PAM. Such arguments will be documented for each individual + module. Note, if you wish to include spaces in an argument, you + should surround that argument with square brackets. + </para> + <programlisting> + squid auth required pam_mysql.so user=passwd_query passwd=mada \ + db=eminence [query=select user_name from internet_service \ + where user_name='%u' and password=PASSWORD('%p') and \ + service='web_proxy'] + </programlisting> + <para> + When using this convention, you can include `[' characters + inside the string, and if you wish to include a `]' character + inside the string that will survive the argument parsing, you + should use `\]'. In other words: + </para> + <programlisting> + [..[..\]..] --> ..[..].. + </programlisting> + + <para> + Any line in (one of) the configuration file(s), that is not formatted + correctly, will generally tend (erring on the side of caution) to make + the authentication process fail. A corresponding error is written to + the system log files with a call to + <citerefentry> + <refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>. + </para> + +</section> |