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#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <pwd.h>
#define PAM_SM_AUTH
#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_mod_misc.h>
#define TTY_PREFIX "/dev/"
#define SECURETTY "/etc/securetty"
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t * pamh, int flags,
int argc, const char * argv[])
{
struct passwd *pwd;
struct stat ttyfileinfo;
const char *user;
const char *tty;
char ttyfileline[256];
FILE *ttyfile;
int pam_err;
if ( ( (pam_err = pam_get_user(pamh, &user, NULL)) != PAM_SUCCESS )
|| ( user == NULL ) ) {
PAM_ERROR("Error recovering username.");
return (pam_err);
}
if ( (pwd = getpwnam(user)) == NULL ) {
PAM_ERROR("Could not get passwd entry for user [%s]",user);
return (PAM_SERVICE_ERR);
}
if ( pwd->pw_uid != 0 ) {
/* secure tty applies only to root */
return (PAM_SUCCESS);
}
if ( (pam_err = pam_get_item(pamh, PAM_TTY,(void *) &tty) ) != PAM_SUCCESS ) {
PAM_ERROR("Could not determine user's tty");
return (pam_err);
}
if (tty != NULL && strncmp(TTY_PREFIX, tty, sizeof(TTY_PREFIX)) == 0) {
PAM_LOG("tty starts with " TTY_PREFIX);
/* get rid of prefix */
tty = (const char *)tty + sizeof(TTY_PREFIX) - 1;
}
if ( stat(SECURETTY, &ttyfileinfo) ) {
PAM_ERROR("Could not open SECURETTY file :%s", SECURETTY);
/* From LinuxPAM, they say that for compatibility issues,
* this needs to succeed. */
return (PAM_SUCCESS);
}
if ((ttyfileinfo.st_mode & S_IWOTH) || !S_ISREG(ttyfileinfo.st_mode)) {
/* File is either world writable or not a regural file */
PAM_ERROR("SECURETTY file cannot be trusted!");
return (PAM_AUTH_ERR);
}
/* Open read-only file with securettys */
if ( (ttyfile = fopen(SECURETTY,"r")) == NULL ) {
PAM_ERROR("Could not open SECURETTY file :%s", SECURETTY);
return (PAM_AUTH_ERR);
}
pam_err = 1;
/* Search in SECURETTY for tty */
while (fgets(ttyfileline, sizeof(ttyfileline)-1, ttyfile) != NULL
&& pam_err) {
if (ttyfileline[strlen(ttyfileline) - 1] == '\n')
ttyfileline[strlen(ttyfileline) - 1] = '\0';
pam_err = strcmp(ttyfileline, tty);
}
fclose(ttyfile);
if (!pam_err) {
/* tty found in SECURETTY. Allow access */
PAM_LOG("Access granted for %s on tty %s.", user, tty);
return (PAM_SUCCESS);
}
PAM_ERROR("Access denied: tty %s is not secure", tty);
return (PAM_AUTH_ERR);
}
PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh , int flags ,
int argc , const char *argv[])
{
return (PAM_SUCCESS);
}
PAM_MODULE_ENTRY("pam_securetty");
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