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Diffstat (limited to 'doc/man/pam_conv.3')
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diff --git a/doc/man/pam_conv.3 b/doc/man/pam_conv.3 new file mode 100644 index 00000000..626d47af --- /dev/null +++ b/doc/man/pam_conv.3 @@ -0,0 +1,145 @@ +.\" Title: pam_conv +.\" Author: +.\" Generator: DocBook XSL Stylesheets v1.73.1 <http://docbook.sf.net/> +.\" Date: 04/16/2008 +.\" Manual: Linux-PAM Manual +.\" Source: Linux-PAM Manual +.\" +.TH "PAM_CONV" "3" "04/16/2008" "Linux-PAM Manual" "Linux-PAM Manual" +.\" disable hyphenation +.nh +.\" disable justification (adjust text to left margin only) +.ad l +.SH "NAME" +pam_conv - PAM conversation function +.SH "SYNOPSIS" +.sp +.ft B +.nf +#include <security/pam_appl\.h> +.fi +.ft +.sp +.RS 4 +.nf +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; +}; + +.fi +.RE +.SH "DESCRIPTION" +.PP +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 +\fIstruct pam_conv\fR +passed to +\fBpam_start\fR(3) +at the start of the transaction\. +.PP +When a module calls the referenced conv() function, the argument +\fIappdata_ptr\fR +is set to the second element of this structure\. +.PP +The other arguments of a call to conv() concern the information exchanged by module and application\. That is to say, +\fInum_msg\fR +holds the length of the array of pointers, +\fImsg\fR\. After a successful return, the pointer +\fIresp\fR +points to an array of pam_response structures, holding the application supplied text\. The +\fIresp_retcode\fR +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 +\fBfree\fR(3)\. Note, +\fI*resp\fR +is a +\fIstruct pam_response\fR +array and not an array of pointers\. +.PP +The number of responses is always equal to the +\fInum_msg\fR +conversation function argument\. This does require that the response array is +\fBfree\fR(3)\'d after every call to the conversation function\. The index of the responses corresponds directly to the prompt index in the pam_message array\. +.PP +On failure, the conversation function should release any resources it has allocated, and return one of the predefined PAM error codes\. +.PP +Each message can have one of four types, specified by the +\fImsg_style\fR +member of +\fIstruct pam_message\fR: +.PP +PAM_PROMPT_ECHO_OFF +.RS 4 +Obtain a string without echoing any text\. +.RE +.PP +PAM_PROMPT_ECHO_ON +.RS 4 +Obtain a string whilst echoing text\. +.RE +.PP +PAM_ERROR_MSG +.RS 4 +Display an error message\. +.RE +.PP +PAM_TEXT_INFO +.RS 4 +Display some text\. +.RE +.PP +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\. +.PP +In passing, it is worth noting that there is a descrepency between the way Linux\-PAM handles the const struct pam_message **msg conversation function argument from the way that Solaris\' PAM (and derivitives, 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\. +.PP +For what its worth the two known module writer work\-arounds for trying to maintain source level compatibility with both PAM implementations are: +.sp +.RS 4 +\h'-04'\(bu\h'+03'never call the conversation function with num_msg greater than one\. +.RE +.sp +.RS 4 +\h'-04'\(bu\h'+03'set up msg as doubly referenced so both types of conversation function can find the messages\. That is, make +.sp +.RS 4 +.nf + msg[n] = & (( *msg )[n]) + +.fi +.RE +.RE +.SH "RETURN VALUES" +.PP +PAM_BUF_ERR +.RS 4 +Memory buffer error\. +.RE +.PP +PAM_CONV_ERR +.RS 4 +Conversation failure\. The application should not set +\fI*resp\fR\. +.RE +.PP +PAM_SUCCESS +.RS 4 +Success\. +.RE +.SH "SEE ALSO" +.PP + +\fBpam_start\fR(3), +\fBpam_set_item\fR(3), +\fBpam_get_item\fR(3), +\fBpam_strerror\fR(3), +\fBpam\fR(8) |