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diff --git a/doc/man/pam_conv.3.xml b/doc/man/pam_conv.3.xml new file mode 100644 index 0000000..5106ddf --- /dev/null +++ b/doc/man/pam_conv.3.xml @@ -0,0 +1,228 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" + "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"> +<refentry id='pam_conv'> + <refmeta> + <refentrytitle>pam_conv</refentrytitle> + <manvolnum>3</manvolnum> + <refmiscinfo class='setdesc'>Linux-PAM Manual</refmiscinfo> + </refmeta> + + <refnamediv id="pam_conv-name"> + <refname>pam_conv</refname> + <refpurpose>PAM conversation function</refpurpose> + </refnamediv> + +<!-- body begins here --> + + <refsynopsisdiv> + <funcsynopsis id="pam_conv-synopsis"> + <funcsynopsisinfo>#include <security/pam_appl.h></funcsynopsisinfo> + </funcsynopsis> + <programlisting> +struct pam_message { + int msg_style; + const char *msg; +}; + +struct pam_response { + char *resp; + int resp_retcode; +}; + +struct pam_conv { + int (*conv)(int num_msg, const struct pam_message **msg, + struct pam_response **resp, void *appdata_ptr); + void *appdata_ptr; +}; + </programlisting> + </refsynopsisdiv> + + <refsect1 id='pam_conv-description'> + <title>DESCRIPTION</title> + <para> + The PAM library uses an application-defined callback to allow + a direct communication between a loaded module and the application. + This callback is specified by the + <emphasis>struct pam_conv</emphasis> passed to + <citerefentry> + <refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum> + </citerefentry> + at the start of the transaction. + </para> + <para> + When a module calls the referenced conv() function, the argument + <emphasis>appdata_ptr</emphasis> is set to the second element of + this structure. + </para> + <para> + The other arguments of a call to conv() concern the information + exchanged by module and application. That is to say, + <emphasis>num_msg</emphasis> holds the length of the array of + pointers, <emphasis>msg</emphasis>. After a successful return, the + pointer <emphasis>resp</emphasis> points to an array of pam_response + structures, holding the application supplied text. The + <emphasis>resp_retcode</emphasis> member of this struct is unused and + should be set to zero. It is the caller's responsibility to release + both, this array and the responses themselves, using + <citerefentry> + <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>. Note, <emphasis>*resp</emphasis> is a + <emphasis>struct pam_response</emphasis> array and not an array of + pointers. + </para> + <para> + The number of responses is always equal to the + <emphasis>num_msg</emphasis> conversation function argument. + This does require that the response array is + <citerefentry> + <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>'d after + every call to the conversation function. The index of the + responses corresponds directly to the prompt index in the + pam_message array. + </para> + <para> + On failure, the conversation function should release any resources + it has allocated, and return one of the predefined PAM error codes. + </para> + <para> + Each message can have one of four types, specified by the + <emphasis>msg_style</emphasis> member of + <emphasis>struct pam_message</emphasis>: + </para> + <variablelist> + <varlistentry> + <term>PAM_PROMPT_ECHO_OFF</term> + <listitem> + <para> + Obtain a string without echoing any text. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>PAM_PROMPT_ECHO_ON</term> + <listitem> + <para> + Obtain a string whilst echoing text. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>PAM_ERROR_MSG</term> + <listitem> + <para> + Display an error message. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>PAM_TEXT_INFO</term> + <listitem> + <para> + Display some text. + </para> + </listitem> + </varlistentry> + </variablelist> + <para> + The point of having an array of messages is that it becomes possible + to pass a number of things to the application in a single call from + the module. It can also be convenient for the application that related + things come at once: a windows based application can then present a + single form with many messages/prompts on at once. + </para> + <para> + In passing, it is worth noting that there is a discrepancy between + the way Linux-PAM handles the const struct pam_message **msg + conversation function argument and the way that Solaris' PAM + (and derivatives, known to include HP/UX, are there others?) does. + Linux-PAM interprets the msg argument as entirely equivalent to the + following prototype + const struct pam_message *msg[] (which, in spirit, is consistent with + the commonly used prototypes for argv argument to the familiar main() + function: char **argv; and char *argv[]). Said another way Linux-PAM + interprets the msg argument as a pointer to an array of num_msg read + only 'struct pam_message' pointers. Solaris' PAM implementation + interprets this argument as a pointer to a pointer to an array of + num_msg pam_message structures. Fortunately, perhaps, for most + module/application developers when num_msg has a value of one these + two definitions are entirely equivalent. Unfortunately, casually + raising this number to two has led to unanticipated compatibility + problems. + </para> + <para> + For what its worth the two known module writer work-arounds for trying + to maintain source level compatibility with both PAM implementations + are: + </para> + <itemizedlist> + <listitem> + <para> + never call the conversation function with num_msg greater than one. + </para> + </listitem> + <listitem> + <para> + set up msg as doubly referenced so both types of conversation + function can find the messages. That is, make + </para> + <programlisting> + msg[n] = & (( *msg )[n]) + </programlisting> + </listitem> + </itemizedlist> + </refsect1> + + <refsect1 id="pam_conv-return_values"> + <title>RETURN VALUES</title> + <variablelist> + <varlistentry> + <term>PAM_BUF_ERR</term> + <listitem> + <para> + Memory buffer error. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>PAM_CONV_ERR</term> + <listitem> + <para> + Conversation failure. The application should not set + <emphasis>*resp</emphasis>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>PAM_SUCCESS</term> + <listitem> + <para> + Success. + </para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1 id='pam_conv-see_also'> + <title>SEE ALSO</title> + <para> + <citerefentry> + <refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>pam_set_item</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>pam_get_item</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>pam_strerror</refentrytitle><manvolnum>3</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum> + </citerefentry> + </para> + </refsect1> +</refentry> |