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/* Andrew Morgan (morgan@kernel.org) -- an example application
* that invokes a shell, based on blank.c */
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <security/pam_appl.h>
#include <security/pam_misc.h>
#include <pwd.h>
#include <sys/types.h>
#include <unistd.h>
/* ------ some local (static) functions ------- */
static void bail_out(pam_handle_t *pamh,int really, int code, const char *fn)
{
fprintf(stderr,"==> called %s()\n got: `%s'\n", fn,
pam_strerror(pamh,code));
if (really && code)
exit (1);
}
/* ------ some static data objects ------- */
static struct pam_conv conv = {
misc_conv,
NULL
};
/* ------- the application itself -------- */
int main(int argc, char **argv)
{
pam_handle_t *pamh=NULL;
const void *username=NULL;
const char *service="xsh";
int retcode;
/* did the user call with a username as an argument ?
* did they also */
if (argc > 3) {
fprintf(stderr,"usage: %s [username [service-name]]\n",argv[0]);
}
if ((argc >= 2) && (argv[1][0] != '-')) {
username = argv[1];
}
if (argc == 3) {
service = argv[2];
}
/* initialize the Linux-PAM library */
retcode = pam_start(service, username, &conv, &pamh);
bail_out(pamh,1,retcode,"pam_start");
/* fill in the RUSER and RHOST etc. fields */
{
char buffer[100];
struct passwd *pw;
const char *tty;
pw = getpwuid(getuid());
if (pw != NULL) {
retcode = pam_set_item(pamh, PAM_RUSER, pw->pw_name);
bail_out(pamh,1,retcode,"pam_set_item(PAM_RUSER)");
}
retcode = gethostname(buffer, sizeof(buffer)-1);
if (retcode) {
perror("failed to look up hostname");
retcode = pam_end(pamh, PAM_ABORT);
bail_out(pamh,1,retcode,"pam_end");
}
retcode = pam_set_item(pamh, PAM_RHOST, buffer);
bail_out(pamh,1,retcode,"pam_set_item(PAM_RHOST)");
tty = ttyname(fileno(stdin));
if (tty) {
retcode = pam_set_item(pamh, PAM_TTY, tty);
bail_out(pamh,1,retcode,"pam_set_item(PAM_RHOST)");
}
}
/* to avoid using goto we abuse a loop here */
for (;;) {
/* authenticate the user --- `0' here, could have been PAM_SILENT
* | PAM_DISALLOW_NULL_AUTHTOK */
retcode = pam_authenticate(pamh, 0);
bail_out(pamh,0,retcode,"pam_authenticate");
/* has the user proved themself valid? */
if (retcode != PAM_SUCCESS) {
fprintf(stderr,"%s: invalid request\n",argv[0]);
break;
}
/* the user is valid, but should they have access at this
time? */
retcode = pam_acct_mgmt(pamh, 0); /* `0' could be as above */
bail_out(pamh,0,retcode,"pam_acct_mgmt");
if (retcode == PAM_NEW_AUTHTOK_REQD) {
fprintf(stderr,"Application must request new password...\n");
retcode = pam_chauthtok(pamh,PAM_CHANGE_EXPIRED_AUTHTOK);
bail_out(pamh,0,retcode,"pam_chauthtok");
}
if (retcode != PAM_SUCCESS) {
fprintf(stderr,"%s: invalid request\n",argv[0]);
break;
}
/* `0' could be as above */
retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED);
bail_out(pamh,0,retcode,"pam_setcred");
if (retcode != PAM_SUCCESS) {
fprintf(stderr,"%s: problem setting user credentials\n"
,argv[0]);
break;
}
/* open a session for the user --- `0' could be PAM_SILENT */
retcode = pam_open_session(pamh,0);
bail_out(pamh,0,retcode,"pam_open_session");
if (retcode != PAM_SUCCESS) {
fprintf(stderr,"%s: problem opening a session\n",argv[0]);
break;
}
pam_get_item(pamh, PAM_USER, &username);
fprintf(stderr,
"The user [%s] has been authenticated and `logged in'\n",
(const char *)username);
/* this is always a really bad thing for security! */
retcode = system("/bin/sh");
/* close a session for the user --- `0' could be PAM_SILENT
* it is possible that this pam_close_call is in another program..
*/
retcode = pam_close_session(pamh,0);
bail_out(pamh,0,retcode,"pam_close_session");
if (retcode != PAM_SUCCESS) {
fprintf(stderr,"%s: problem closing a session\n",argv[0]);
break;
}
/* `0' could be as above */
retcode = pam_setcred(pamh, PAM_DELETE_CRED);
bail_out(pamh,0,retcode,"pam_setcred");
if (retcode != PAM_SUCCESS) {
fprintf(stderr,"%s: problem deleting user credentials\n"
,argv[0]);
break;
}
break; /* don't go on for ever! */
}
/* close the Linux-PAM library */
retcode = pam_end(pamh, PAM_SUCCESS);
pamh = NULL;
bail_out(pamh,1,retcode,"pam_end");
return (0);
}
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