121 lines
3.7 KiB
C
Executable File
121 lines
3.7 KiB
C
Executable File
/* $Header: https://svn.ita.chalmers.se/repos/security/edu/course/computer_security/trunk/lab/login_linux/login_linux.c 585 2013-01-19 10:31:04Z pk@CHALMERS.SE $ */
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/* gcc -std=gnu99 -Wall -g -o mylogin login_linux.c -lcrypt */
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#include <stdlib.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdio_ext.h>
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#include <string.h>
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#include <signal.h>
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#include <pwd.h>
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#include <sys/types.h>
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#include <crypt.h>
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#include "pwent.h" /* Step 2 */
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#define TRUE 1
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#define FALSE 0
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#define LENGTH 16
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void sighandler() {
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//sigset_t mask;
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//sigfillset(&mask);
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//sigprocmask(SIG_SETMASK, &mask, NULL);
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signal(SIGINT, SIG_IGN); /* This will catch ctrl+c and ignore it*/
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//signal(SIGTSTP, SIG_IGN); /* This will catch ctrl+z and ignore it*/
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/* add signalhandling routines here */
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/* see 'man 2 signal' */
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}
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int main(int argc, char *argv[]) {
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//struct passwd *passwddata /* Step 1 */
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mypwent *passwddata; /* Step 2 */
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/* see pwent.h */
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char important1[LENGTH] = "**IMPORTANT 1**";
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char user[LENGTH];
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char important2[LENGTH] = "**IMPORTANT 2**";
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//char *c_pass; //you might want to use this variable later...
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char prompt[] = "password: ";
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char *user_pass;
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sighandler();
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while (TRUE) {
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/* check what important variable contains - do not remove, part of buffer overflow test */
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printf("Value of variable 'important1' before input of login name: %s\n",
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important1);
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printf("Value of variable 'important2' before input of login name: %s\n",
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important2);
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printf("login: ");
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fflush(NULL); /* Flush all output buffers */
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__fpurge(stdin); /* Purge any data in stdin buffer */
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if (fgets(user,sizeof(user),stdin) == NULL ) {
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clearerr(stdin); //if EOF only, clear error
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continue; ///* overflow attacks. */
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}
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user[strlen(user)-1] = '\0'; //replacing \n with \0
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/* check to see if important variable is intact after input of login name - do not remove */
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printf("Value of variable 'important 1' after input of login name: %*.*s\n",
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LENGTH - 1, LENGTH - 1, important1);
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printf("Value of variable 'important 2' after input of login name: %*.*s\n",
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LENGTH - 1, LENGTH - 1, important2);
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// using makepass.c to create hashed password -> saving it manually in passdb
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user_pass = getpass(prompt); //enter password using deprecated function :/
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passwddata = mygetpwnam(user); //get user info from passdb
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if (passwddata != NULL) {
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/* You have to encrypt user_pass for this to work */
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/* Don't forget to include the salt */
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char *user_pass_encrypted = crypt(user_pass, passwddata->passwd_salt);
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if (&user_pass_encrypted == NULL) {
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perror("Error");exit(EXIT_FAILURE);
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}
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printf("encryption of typed pass: %s \n", user_pass_encrypted);
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if (passwddata->pwfailed >= 10) {
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printf("Too many failed login attempts. Your account has been locked.\nContact and Admin to unlock your account.\n");
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} else if (!strcmp(user_pass_encrypted, passwddata->passwd)) {
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printf(" You're in !\n");
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passwddata->pwfailed = 0;
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passwddata->pwage = passwddata->pwage + 1;
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if (mysetpwent(user, passwddata) < 0) { /* execute the command */
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perror("Error");exit(EXIT_FAILURE);
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}
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if (passwddata->pwage > 100) {
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printf(" Your password is OLD!!!!\n");
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}
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/* check UID, see setuid(2) */
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if (setuid(passwddata->uid) < 0) { /* execute the command */
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perror("Error");exit(EXIT_FAILURE);
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}
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/* start a shell, use execve(2) */
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if (execve("/bin/bash",NULL,NULL) < 0) { /* execute the command */
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perror("Error");exit(EXIT_FAILURE);
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}
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} else {
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passwddata->pwfailed = passwddata->pwfailed + 1;
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if (mysetpwent(user, passwddata) < 0) { /* execute the command */
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perror("Error");exit(EXIT_FAILURE);
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}
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}
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}
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printf("Login Incorrect \n");
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}
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return 0;
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}
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