#include <stdio.h>
#include <string.h>

unsigned long hashcode = 0x21DD09EC;

unsigned long check_password(const char *p) {
    int *ip = (int *) p;
    int res = 0;
    for (int i = 0; i < 5; i++) {
        res += ip[i];
    }
    return res;
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("usage : %s [passcode]\n", argv[0]);
        return 0;
    }

    if (strlen(argv[1]) != 20) {
        printf("passcode length should be 20 bytes\n");
        return 0;
    }

    if (hashcode == check_password(argv[1])) {
        system("/bin/cat flag");
        return 0;
    } else
        printf("wrong passcode.\n");
    return 0;
}

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void func(int key) {
    char overflowme[32];
    printf("overflow me : ");
    gets(overflowme);    // smash me!
    if (key == 0xcafebabe) {
        system("/bin/sh");
    } else {
        printf("Nah..\n");
    }
}

int main(int argc, char *argv[]) {
    func(0xdeadbeef);
    return 0;
}

int __cdecl main(int argc, const char **argv, const char **envp)
{
  char *dest; // [rsp+8h] [rbp-8h]

  puts("I will malloc() and strcpy the flag there. take it.", argv, envp);
  dest = (char *)malloc(100LL);
  strcpy(dest, flag);
  return 0;
}

#include <stdio.h>
#include <stdlib.h>

void login() {
    int passcode1;
    int passcode2;

    printf("enter passcode1 : ");
    scanf("%d", passcode1);
    fflush(stdin);

    // ha! mommy told me that 32bit is vulnerable to bruteforcing :)
    printf("enter passcode2 : ");
    scanf("%d", passcode2);

    printf("checking...\n");
    if (passcode1 == 338150 && passcode2 == 13371337) {
        printf("Login OK!\n");
        system("/bin/cat flag");
    } else {
        printf("Login Failed!\n");
        exit(0);
    }
}

void welcome() {
    char name[100];
    printf("enter you name : ");
    scanf("%100s", name);
    printf("Welcome %s!\n", name);
}

int main() {
    printf("Toddler's Secure Login System 1.0 beta.\n");

    welcome();
    login();

    // something after login...
    printf("Now I can safely trust you that you have credential :)\n");
    return 0;
}

scanf("%100s", name);

#include <stdio.h>

int main() {
    unsigned int random;
    random = rand();  // random value!

    unsigned int key = 0;
    scanf("%d", &key);

    if ((key ^ random) == 0xdeadbeef) {
        printf("Good!\n");
        system("/bin/cat flag");
        return 0;
    }

    printf("Wrong, maybe you should try 2^32 cases.\n");
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>

int main(int argc, char *argv[], char *envp[]) {
    printf("Welcome to pwnable.kr\n");
    printf("Let's see if you know how to give input to program\n");
    printf("Just give me correct inputs then you will get the flag :)\n");

    // argv
    if (argc != 100) return 0;
    if (strcmp(argv['A'], "\x00")) return 0;
    if (strcmp(argv['B'], "\x20\x0a\x0d")) return 0;
    printf("Stage 1 clear!\n");

    // stdio
    char buf[4];
    read(0, buf, 4);
    if (memcmp(buf, "\x00\x0a\x00\xff", 4)) return 0;
    read(2, buf, 4);
    if (memcmp(buf, "\x00\x0a\x02\xff", 4)) return 0;
    printf("Stage 2 clear!\n");

    // env
    if (strcmp("\xca\xfe\xba\xbe", getenv("\xde\xad\xbe\xef"))) return 0;
    printf("Stage 3 clear!\n");

    // file
    FILE *fp = fopen("\x0a", "r");
    if (!fp) return 0;
    if (fread(buf, 4, 1, fp) != 1) return 0;
    if (memcmp(buf, "\x00\x00\x00\x00", 4)) return 0;
    fclose(fp);
    printf("Stage 4 clear!\n");

    // network
    int sd, cd;
    struct sockaddr_in saddr, caddr;
    sd = socket(AF_INET, SOCK_STREAM, 0);
    if (sd == -1) {
        printf("socket error, tell admin\n");
        return 0;
    }
    saddr.sin_family = AF_INET;
    saddr.sin_addr.s_addr = INADDR_ANY;
    saddr.sin_port = htons(atoi(argv['C']));
    if (bind(sd, (struct sockaddr *) &saddr, sizeof(saddr)) < 0) {
        printf("bind error, use another port\n");
        return 1;
    }
    listen(sd, 1);
    int c = sizeof(struct sockaddr_in);
    cd = accept(sd, (struct sockaddr *) &caddr, (socklen_t * ) & c);
    if (cd < 0) {
        printf("accept error, tell admin\n");
        return 0;
    }
    if (recv(cd, buf, 4, 0) != 4) return 0;
    if (memcmp(buf, "\xde\xad\xbe\xef", 4)) return 0;
    printf("Stage 5 clear!\n");

    // here's your flag
    system("/bin/cat flag");
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>

unsigned char submit[6];

void play() {
    printf("Submit your 6 lotto bytes : ");
    fflush(stdout);

    int r = read(0, submit, 6);

    printf("Lotto Start!\n");
    //sleep(1);

    // generate lotto numbers
    int fd = open("/dev/urandom", O_RDONLY);
    if (fd == -1) {
        printf("error. tell admin\n");
        exit(-1);
    }
    unsigned char lotto[6];
    if (read(fd, lotto, 6) != 6) {
        printf("error2. tell admin\n");
        exit(-1);
    }
    for (int i = 0; i < 6; i++) {
        lotto[i] = (lotto[i] % 45) + 1;         // 1 ~ 45
    }
    close(fd);

    // calculate lotto score
    int match = 0, j = 0;
    for (int i = 0; i < 6; i++) {
        for (j = 0; j < 6; j++) {
            if (lotto[i] == submit[j]) {
                match++;
            }
        }
    }

    // win!
    if (match == 6) {
        system("/bin/cat flag");
    } else {
        printf("bad luck...\n");
    }

}

void help() {
    printf("- nLotto Rule -\n");
    printf("nlotto is consisted with 6 random natural numbers less than 46\n");
    printf("your goal is to match lotto numbers as many as you can\n");
    printf("if you win lottery for *1st place*, you will get reward\n");
    printf("for more details, follow the link below\n");
    printf("http://www.nlotto.co.kr/counsel.do?method=playerGuide#buying_guide01\n\n");
    printf("mathematical chance to win this game is known to be 1/8145060.\n");
}

int main(int argc, char *argv[]) {
    // menu
    unsigned int menu;

    while (1) {
        printf("- Select Menu -\n");
        printf("1. Play Lotto\n");
        printf("2. Help\n");
        printf("3. Exit\n");

        scanf("%d", &menu);

        switch (menu) {
            case 1:
                play();
                break;
            case 2:
                help();
                break;
            case 3:
                printf("bye\n");
                return 0;
            default:
                printf("invalid menu\n");
                break;
        }
    }
    return 0;
}

#include <stdio.h>
#include <string.h>

int filter(char *cmd) {
    int r = 0;
    r += strstr(cmd, "flag") != 0;
    r += strstr(cmd, "sh") != 0;
    r += strstr(cmd, "tmp") != 0;
    return r;
}

int main(int argc, char *argv[], char **envp) {
    putenv("PATH=/thankyouverymuch");
    if (filter(argv[1])) return 0;
    system(argv[1]);
    return 0;
}

#include <stdio.h>
#include <string.h>

int filter(char *cmd) {
    int r = 0;
    r += strstr(cmd, "=") != 0;
    r += strstr(cmd, "PATH") != 0;
    r += strstr(cmd, "export") != 0;
    r += strstr(cmd, "/") != 0;
    r += strstr(cmd, "`") != 0;
    r += strstr(cmd, "flag") != 0;
    return r;
}

extern char **environ;

void delete_env() {
    char **p;
    for (p = environ; *p; p++) memset(*p, 0, strlen(*p));
}

int main(int argc, char *argv[], char **envp) {
    delete_env();
    putenv("PATH=/no_command_execution_until_you_become_a_hacker");
    if (filter(argv[1])) return 0;
    printf("%s\n", argv[1]);
    system(argv[1]);
    return 0;
}

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>

char flag[100];
char password[100];
char *key = "3\rG[S/%\x1c\x1d#0?\rIS\x0f\x1c\x1d\x18;,4\x1b\x00\x1bp;5\x0b\x1b\x08\x45+";

void calc_flag(char *s) {
    int i;
    for (i = 0; i < strlen(s); i++) {
        flag[i] = s[i] ^ key[i];
    }
    printf("%s\n", flag);
}

int main() {
    FILE *fp = fopen("/home/blukat/password", "r");
    fgets(password, 100, fp);
    char buf[100];
    printf("guess the password!\n");
    fgets(buf, 128, stdin);
    if (!strcmp(password, buf)) {
        printf("congrats! here is your flag: ");
        calc_flag(password);
    } else {
        printf("wrong guess!\n");
        exit(0);
    }
    return 0;
}