Protostar Net Writeup

#include "../common/common.c"

#define NAME "net0"
#define UID 999
#define GID 999
#define PORT 2999

void run()
{
  unsigned int i;
  unsigned int wanted;

  wanted = random();

  printf("Please send '%d' as a little endian 32bit int\n", wanted);

  if(fread(&i, sizeof(i), 1, stdin) == NULL) {
      errx(1, ":(\n");
  }

  if(i == wanted) {
      printf("Thank you sir/madam\n");
  } else {
      printf("I'm sorry, you sent %d instead\n", i);
  }
}

int main(int argc, char **argv, char **envp)
{
  int fd;
  char *username;

  /* Run the process as a daemon */
  background_process(NAME, UID, GID); 
  
  /* Wait for socket activity and return */
  fd = serve_forever(PORT);

  /* Set the client socket to STDIN, STDOUT, and STDERR */
  set_io(fd);

  /* Don't do this :> */
  srandom(time(NULL));

  run();
}

#include "../common/common.c"

#define NAME "net1"
#define UID 998
#define GID 998
#define PORT 2998

void run()
{
  char buf[12];
  char fub[12];
  char *q;

  unsigned int wanted;

  wanted = random();

  sprintf(fub, "%d", wanted);

  if(write(0, &wanted, sizeof(wanted)) != sizeof(wanted)) {
      errx(1, ":(\n");
  }

  if(fgets(buf, sizeof(buf)-1, stdin) == NULL) {
      errx(1, ":(\n");
  }

  q = strchr(buf, '\r'); if(q) *q = 0;
  q = strchr(buf, '\n'); if(q) *q = 0;

  if(strcmp(fub, buf) == 0) {
      printf("you correctly sent the data\n");
  } else {
      printf("you didn't send the data properly\n");
  }
}

int main(int argc, char **argv, char **envp)
{
  int fd;
  char *username;

  /* Run the process as a daemon */
  background_process(NAME, UID, GID); 
  
  /* Wait for socket activity and return */
  fd = serve_forever(PORT);

  /* Set the client socket to STDIN, STDOUT, and STDERR */
  set_io(fd);

  /* Don't do this :> */
  srandom(time(NULL));

  run();
}

#include "../common/common.c"

#define NAME "net2"
#define UID 997
#define GID 997
#define PORT 2997

void run()
{
  unsigned int quad[4];
  int i;
  unsigned int result, wanted;

  result = 0;
  for(i = 0; i < 4; i++) {
      quad[i] = random();
      result += quad[i];

      if(write(0, &(quad[i]), sizeof(result)) != sizeof(result)) {
          errx(1, ":(\n");
      }
  }

  if(read(0, &wanted, sizeof(result)) != sizeof(result)) {
      errx(1, ":<\n");
  }


  if(result == wanted) {
      printf("you added them correctly\n");
  } else {
      printf("sorry, try again. invalid\n");
  }
}

int main(int argc, char **argv, char **envp)
{
  int fd;
  char *username;

  /* Run the process as a daemon */
  background_process(NAME, UID, GID); 
  
  /* Wait for socket activity and return */
  fd = serve_forever(PORT);

  /* Set the client socket to STDIN, STDOUT, and STDERR */
  set_io(fd);

  /* Don't do this :> */
  srandom(time(NULL));

  run();
}

#include "../common/common.c"

#define NAME "net3"
#define UID 996
#define GID 996
#define PORT 2996

/*
 * Extract a null terminated string from the buffer 
*/

int get_string(char **result, unsigned char *buffer, u_int16_t len)
{
  unsigned char byte;

  byte = *buffer;

  if(byte > len) errx(1, "badly formed packet");
  *result = malloc(byte);
  strcpy(*result, buffer + 1);

  return byte + 1;
}

/*
 * Check to see if we can log into the host
 */

int login(unsigned char *buffer, u_int16_t len)
{
  char *resource, *username, *password;
  int deduct;
  int success;

  if(len < 3) errx(1, "invalid login packet length");

  resource = username = password = NULL;

  deduct = get_string(&resource, buffer, len);
  deduct += get_string(&username, buffer+deduct, len-deduct);
  deduct += get_string(&password, buffer+deduct, len-deduct);

  success = 0;
  success |= strcmp(resource, "net3");
  success |= strcmp(username, "awesomesauce");
  success |= strcmp(password, "password");

  free(resource);
  free(username);
  free(password);

  return ! success;
}

void send_string(int fd, unsigned char byte, char *string)
{
  struct iovec v[3];
  u_int16_t len;
  int expected;

  len = ntohs(1 + strlen(string));

  v[0].iov_base = &len;
  v[0].iov_len = sizeof(len);
  
  v[1].iov_base = &byte;
  v[1].iov_len = 1;

  v[2].iov_base = string;
  v[2].iov_len = strlen(string);

  expected = sizeof(len) + 1 + strlen(string);

  if(writev(fd, v, 3) != expected) errx(1, "failed to write correct amount of bytes");
  
}

void run(int fd)
{
  u_int16_t len;
  unsigned char *buffer;
  int loggedin;

  while(1) {
    nread(fd, &len, sizeof(len));
    len = ntohs(len);
    buffer = malloc(len);

    if(! buffer) errx(1, "malloc failure for %d bytes", len);

    nread(fd, buffer, len);

    switch(buffer[0]) {
      case 23: 
        loggedin = login(buffer + 1, len - 1);
        send_string(fd, 33, loggedin ? "successful" : "failed");
        break;
      
      default:
        send_string(fd, 58, "what you talkin about willis?");
        break;
    }
  }
}

int main(int argc, char **argv, char **envp)
{
  int fd;
  char *username;

  /* Run the process as a daemon */
  background_process(NAME, UID, GID);  
  
  /* Wait for socket activity and return */
  fd = serve_forever(PORT);

  /* Set the client socket to STDIN, STDOUT, and STDERR */
  set_io(fd);

  /* Don't do this :> */
  srandom(time(NULL));

  run(fd);
}