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kollade lite mer, setuid funkar inte remote på skoldatorerna alls....

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skrev in "TODO" på grejer vi bör kolla på också
This commit is contained in:
parken 2022-01-31 16:38:30 +01:00
parent 9df42871ff
commit 383abfc185
1 changed files with 97 additions and 27 deletions
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124
lab1/login_linux.c
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@ -2,6 +2,10 @@
/* gcc -std=gnu99 -Wall -g -o mylogin login_linux.c -lcrypt */
/* Note, makepass.c is first used to create hashed password
then, info is manually saved in file passdb */
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
@ -12,6 +16,8 @@
#include <sys/types.h>
#include <crypt.h>
#include "pwent.h" /* Step 2 */
#include <termios.h>
#include <stdbool.h>
#define TRUE 1
#define FALSE 0
@ -24,15 +30,14 @@ void sighandler() {
signal(SIGINT, SIG_IGN); /* This will catch ctrl+c and ignore it*/
//signal(SIGTSTP, SIG_IGN); /* This will catch ctrl+z and ignore it*/
/* add signalhandling routines here */
/* see 'man 2 signal' */
//signal(SIGTERM,SIG_IGN); //TODO block termios kanske...
}
int main(int argc, char *argv[]) {
//struct passwd *passwddata /* Step 1 */
mypwent *passwddata; /* Step 2 */
/* see pwent.h */
char important1[LENGTH] = "**IMPORTANT 1**";
@ -40,9 +45,10 @@ int main(int argc, char *argv[]) {
char important2[LENGTH] = "**IMPORTANT 2**";
//char *c_pass; //you might want to use this variable later...
char prompt[] = "password: ";
char *user_pass;
//char *c_pass; //you might want to use this variable later... TODO
//char prompt[] = "password: ";
//char *user_pass;
char user_pass[LENGTH]; // TODO la till denna
sighandler();
@ -53,68 +59,132 @@ int main(int argc, char *argv[]) {
printf("Value of variable 'important2' before input of login name: %s\n",
important2);
//////////////////////////////////////////////////////////////////////////////////////////
printf("login: ");
fflush(NULL); /* Flush all output buffers */
__fpurge(stdin); /* Purge any data in stdin buffer */
bool okusername = true;
/* using fgets instead of gets to avoid buffer overflow attacks*/
if (fgets(user,sizeof(user),stdin) == NULL ) {
clearerr(stdin); //if EOF only, clear error
continue; ///* overflow attacks. */
// if error or EOF (ctrl+d)
// TODO need for more error handling ?
clearerr(stdin);
okusername = false;
}
user[strlen(user)-1] = '\0'; //replacing \n with \0
if (strlen(user) == sizeof(user)-1 || strlen(user) == 1){
// too long username or no username was entered
okusername = false;
}
else{
// replacing \n with \0
user[strcspn(user,"\n")] = '\0';
}
//////////////////////////////////////////////////////////////////////////////////////////
/* check to see if important variable is intact after input of login name - do not remove */
printf("Value of variable 'important 1' after input of login name: %*.*s\n",
LENGTH - 1, LENGTH - 1, important1);
printf("Value of variable 'important 2' after input of login name: %*.*s\n",
LENGTH - 1, LENGTH - 1, important2);
// using makepass.c to create hashed password -> saving it manually in passdb
//////////////////////////////////////////////////////////////////////////////////////////
// using termios instead of the outdated getpass
// user_pass = getpass(prompt);
user_pass = getpass(prompt); //enter password using deprecated function :/
passwddata = mygetpwnam(user); //get user info from passdb
struct termios old_term_flags, new_term_flags;
/* Turn echoing off so password will not be shown in terminal */
if (tcgetattr(fileno(stdin), &old_term_flags) != 0){
perror("Error");
exit(EXIT_FAILURE);
}
new_term_flags = old_term_flags;
new_term_flags.c_lflag &= ~ECHO;
if (tcsetattr(fileno(stdin), TCSAFLUSH, &new_term_flags) != 0) {
perror("Error");
exit(EXIT_FAILURE);
}
bool okpassword = true;
printf("password: ");
if (fgets(user_pass,sizeof(user_pass),stdin) == NULL ) {
clearerr(stdin);
okpassword = false;
}
if (strlen(user_pass) == sizeof(user_pass)-1 || strlen(user_pass) == 1){
okpassword = false;
}
/* Restore terminal */
if (tcsetattr(fileno(stdin), TCSAFLUSH, &old_term_flags) != 0) {
perror("Error");exit(EXIT_FAILURE);
}
if (!okpassword || !okusername){
printf("\nLogin Incorrect \n \n");
continue;
}
user_pass[strcspn(user_pass, "\n")] = '\0'; // replacing \n with \0
//////////////////////////////////////////////////////////////////////////////////////////
//get user info from passdb
passwddata = mygetpwnam(user);
if (passwddata != NULL) {
/* You have to encrypt user_pass for this to work */
/* Don't forget to include the salt */
if (passwddata->pwfailed >= 10) {
printf("\nToo many failed login attempts. Your account has been locked.\nContact and Admin to unlock your account.\n");
continue;
}
/* Encryp user_pass with salt included */
char *user_pass_encrypted = crypt(user_pass, passwddata->passwd_salt);
if (&user_pass_encrypted == NULL) {
if (user_pass_encrypted == NULL) {
perror("Error");exit(EXIT_FAILURE);
}
printf("encryption of typed pass: %s \n", user_pass_encrypted);
if (passwddata->pwfailed >= 10) {
printf("Too many failed login attempts. Your account has been locked.\nContact and Admin to unlock your account.\n");
} else if (!strcmp(user_pass_encrypted, passwddata->passwd)) {
printf(" You're in !\n");
if (!strcmp(user_pass_encrypted, passwddata->passwd)) {
// successfull login
passwddata->pwfailed = 0;
passwddata->pwage = passwddata->pwage + 1;
if (mysetpwent(user, passwddata) < 0) { /* execute the command */
if (mysetpwent(user, passwddata) < 0) {
perror("Error");exit(EXIT_FAILURE);
}
if (passwddata->pwage > 100) {
printf(" Your password is OLD!!!!\n");
// TODO
}
/* check UID, see setuid(2) */
if (setuid(passwddata->uid) < 0) { /* execute the command */
if (setuid(passwddata->uid) < 0) {
printf(" always here !\n");
perror("Error");exit(EXIT_FAILURE);
}
printf(" cant get here !\n");
/* start a shell, use execve(2) */
if (execve("/bin/bash",NULL,NULL) < 0) { /* execute the command */
if (execve("/bin/bash",NULL,NULL) < 0) {
perror("Error");exit(EXIT_FAILURE);
}
} else {
}
else {
// user name exists but password does not match
passwddata->pwfailed = passwddata->pwfailed + 1;
if (mysetpwent(user, passwddata) < 0) { /* execute the command */
if (mysetpwent(user, passwddata) < 0) {
perror("Error");exit(EXIT_FAILURE);
}
}
}
printf("Login Incorrect \n");
printf("\nLogin Incorrect \n \n");
}
return 0;
}