• El cliente solo puede saber si su paquete fue aceptado o no.

• El servidor no Cambia de KEY utilizada durante el proceso de cifrado y descifrado.

• El servidor tiene algún leak de información ya sea por error o mediante otro tipo de ataque.
• El cliente solo podrá descifrar Una parte de la información, excepto por el Bloque inicial

/*
Desarollado por AlbertoBSD 
email alberto.bsd@gmail.com
g++ -O3 -o opk_example opk_example.c -Wint-to-pointer-cast  -pthread
*/
 
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include<pthread.h>
#include<unistd.h>
#include"ctaes/ctaes.c"
 
#define AES_BLOCKSIZE 16
 
struct timespec tim, tim2,sim,sim2;
 
void crear_server();
char *tohex(char *ptr,int length);
void *process_server(void *vargp);
 
int MyCBCEncrypt(AES256_ctx *ctx, const unsigned char iv[AES_BLOCKSIZE], const unsigned char* data, int size, bool pad, unsigned char* out);
int MyCBCDecrypt(AES256_ctx *ctx, const unsigned char iv[AES_BLOCKSIZE], const unsigned char* data, int size, bool pad, unsigned char* out);
 
/* Values between Server and client */
int values_do;
int values_pad;
int values_length;
int values_leaked;
char *values_enc;
char *values_leak;
 
pthread_mutex_t mtx_values;  //Mutex for those values
 
int main(){
  /*
    Set global values;
  */
  tim.tv_sec = 0;
  tim.tv_nsec = 50000;
 
  sim.tv_sec = 0;
  sim.tv_nsec = 50000;
  values_do = 0;
  values_pad = 0;
  values_length = 0;
  values_leaked = 0;
  values_enc = (char*) malloc(48);
  values_leak = (char*) malloc(48);
  crear_server();  //create child "server"
 
  //This main process is the client
  int i,j,k,entrar;
  char *secret,*temp,*try_enc;
  char *decrypted;
  unsigned char GUESS;
  secret = (char*) malloc(48);
  try_enc = (char*) malloc(48);
  decrypted = (char*) malloc(16);
  memset(decrypted,0,16);
  do  {  
    sleep(1);
  }while(values_leaked==0); //We need to wait to the leaked data
 
  memcpy(secret,values_leak,48);
 
  temp = tohex(secret,48);
  printf("process_client: leaked is %s\n",temp);
  free(temp);
  i = 0;
  j = 0;
  while(i < 16)  {
    memcpy(try_enc,secret,32);
 
    pthread_mutex_lock(&mtx_values);
    switch(values_do)  {
      case 0:
        GUESS = j;
        decrypted[15-i] = GUESS;
        for(k = 0; k <= i;k++)  {
          try_enc[15-k] = try_enc[15-k] ^ decrypted[15-k] ^ (unsigned char)(i+1);
        }
 
        values_do = 1;
        values_length = 32;
        memcpy(values_enc,try_enc,32);
      break;
      case 1:
      break;
      case 2:
        if(values_pad)  {
          i++;
          printf("Encontrado valor: %c : %.2x\n",GUESS,GUESS);
          j = 0;
        }
        else  {
          j++;
        }
        values_do = 0;
      break;
    }
    pthread_mutex_unlock(&mtx_values);
    nanosleep(&tim , &tim2);
  }
  printf("Decrypted data: %s\n",decrypted);
 
}
 
void *process_server(void *vargp)  {
  AES256_ctx ctx;
  FILE *urandom;
  const char *secret = "The password is: Ywgo/@g:2$0Qsz<";
  char *key,*dec,*enc,*iv,*temp;
  int length,i,pad_valid,outlen;
  unsigned char pad;
  key = (char*) malloc(32);
  dec = (char*) malloc(48);
  enc = (char*) malloc(48);
  iv  = (char*) malloc(16);
  urandom = fopen("/dev/urandom","rb");
  fread(key,1,32,urandom);
  fread(iv,1,16,urandom);
  fclose(urandom);
 
  AES256_init(&ctx,(const unsigned char*) key);
 
  /* LEAK THE secret */
  pthread_mutex_lock(&mtx_values);
  memset(enc,0,48);
 
 
  outlen = MyCBCEncrypt(&ctx, (const unsigned char*) iv, (const unsigned char*) secret, strlen(secret), true, (unsigned char*) enc);
 
  memcpy(values_leak,enc,outlen);
  values_leaked = 1;
  pthread_mutex_unlock(&mtx_values);
  /*END LEAK*/
 
  do  {
    nanosleep(&sim , &sim2);
    pthread_mutex_lock(&mtx_values);
    if(values_do == 1)  {
      length = values_length;
      pad_valid = 0;
      if(length <= 48)  {
        memcpy(enc,values_enc,length);
 
        outlen = MyCBCDecrypt(&ctx,( const unsigned char*) iv, (const unsigned char*) enc, length, true, (unsigned char*) dec);
        if(outlen > 0)  {
          pad_valid =  1;
          printf("Decrypted data seems legit : %i bytes\n",outlen);
          temp = tohex(dec,length);
          printf("Decrypted data %s\n",temp);
          free(temp);
        }
        else  {
          printf("Decrypted data doesnt seems legit\n",outlen);
          temp = tohex(dec,length);
          printf("Decrypted data %s\n",temp);
          free(temp);
        }
      }
      values_do = 2;
      values_pad = pad_valid;
    }
    pthread_mutex_unlock(&mtx_values);
  }while(1);
  pthread_exit(NULL);
}
 
void crear_server()  {
  int s;
  pthread_t tid;
  pthread_attr_t attr;
  s = pthread_attr_init(&attr);
  if (s != 0)  {
    perror("pthread_attr_init");
    exit(6);
  }
  s = pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED);
  if(s != 0)  {
    perror("pthread_attr_setstacksize");
    exit(8);
  }
  s = pthread_create(&tid,&attr,process_server,NULL);
  if(s != 0)  {
    perror("pthread_create");
  }
  pthread_attr_destroy(&attr);
}
 
char *tohex(char *ptr,int length){
  char *buffer;
  int offset = 0;
  unsigned char c;
  buffer = (char *) malloc((length * 2)+1);
  for (int i = 0; i <length; i++) {
  c = ptr[i];
  sprintf((char*) (buffer + offset),"%.2x",c);
  offset+=2;
  }
  buffer[length*2] = 0;
  return buffer;
}
 
 
int MyCBCDecrypt(AES256_ctx *ctx, const unsigned char iv[AES_BLOCKSIZE], const unsigned char* data, int size, bool pad, unsigned char* out)
{
  int written = 0;
  bool fail = false;
  const unsigned char* prev = iv;
  if (!data || !size || !out)
    return 0;
  if (size % AES_BLOCKSIZE != 0)
    return 0;
  while (written != size) {
    AES256_decrypt(ctx, 1, out, data + written);
    for (int i = 0; i != AES_BLOCKSIZE; i++)
      *out++ ^= prev[i];
    prev = data + written;
    written += AES_BLOCKSIZE;
  }
  if (pad) {
    unsigned char padsize = *--out;
    fail = !padsize | (padsize > AES_BLOCKSIZE);
    padsize *= !fail;
    for (int i = AES_BLOCKSIZE; i != 0; i--)
      fail |= ((i > AES_BLOCKSIZE - padsize) & (*out-- != padsize));
    written -= padsize;
  }
  return written * !fail;
}
 
int MyCBCEncrypt(AES256_ctx *ctx, const unsigned char iv[AES_BLOCKSIZE], const unsigned char* data, int size, bool pad, unsigned char* out)
{
  int written = 0;
  int padsize = size % AES_BLOCKSIZE;
  unsigned char mixed[AES_BLOCKSIZE];
 
  if (!data || !size || !out)
    return 0;
 
  if (!pad && padsize != 0)
    return 0;
 
  memcpy(mixed, iv, AES_BLOCKSIZE);
 
  // Write all but the last block
  while (written + AES_BLOCKSIZE <= size) {
    for (int i = 0; i != AES_BLOCKSIZE; i++)
      mixed[i] ^= *data++;
    AES256_encrypt(ctx, 1, out + written, mixed);
    memcpy(mixed, out + written, AES_BLOCKSIZE);
    written += AES_BLOCKSIZE;
  }
  if (pad) {
    // For all that remains, pad each byte with the value of the remaining
    // space. If there is none, pad by a full block.
    for (int i = 0; i != padsize; i++)
      mixed[i] ^= *data++;
    for (int i = padsize; i != AES_BLOCKSIZE; i++)
      mixed[i] ^= AES_BLOCKSIZE - padsize;
    AES256_encrypt(ctx, 1, out + written, mixed);
    written += AES_BLOCKSIZE;
  }
  return written;
}
 

void arrancarPing(const char* ip)
{
    char command[255] = {0};
 
    sprintf(command, "ping %s > ping2.txt", ip);
    system(command);
}

void insertAfter(int llave, int dato) {
    struct node *l,*t;
 

     if (start == NULL) {				// Primera vez
      start = t;//t en este punto no esta inicializado a nada.