dns_random.c

Go to the documentation of this file.

#include <unistd.h>
#include "taia.h"
#include "uint_t.h"
#include "dns.h"
#include "open.h"
#include "logmsg.h"
#include "curve.h"
 
static uint32 seed[32];
static uint32 in[12];
static uint32 out[8];
static int outleft = 0;
 
#define ROTATE(x,b) (((x) << (b)) | ((x) >> (32 - (b))))
#define MUSH(i,b) x = t[i] += (((x ^ seed[i]) + sum) ^ ROTATE(x,b));
 
void surf(void)
{
  uint32 t[12]; uint32 x; uint32 sum = 0;
  int r; int i; int loop;
 
  for (i = 0; i < 12; ++i) t[i] = in[i] ^ seed[12 + i];
  for (i = 0; i < 8; ++i) out[i] = seed[24 + i];
  x = t[11];
  for (loop = 0; loop < 2; ++loop) {
    for (r = 0; r < 16; ++r) {
      sum += 0x9e3779b9;
      MUSH(0,5) MUSH(1,7) MUSH(2,9) MUSH(3,13)
      MUSH(4,5) MUSH(5,7) MUSH(6,9) MUSH(7,13)
      MUSH(8,5) MUSH(9,7) MUSH(10,9) MUSH(11,13)
    }
    for (i = 0; i < 8; ++i) out[i] ^= t[i + 4];
  }
}
 
void dns_random_init(const char data[128])
{
  int i;
  struct taia t;
  char tpack[16];
 
  for (i = 0; i < 32; ++i)
    uint32_unpack((char *)data + 4 * i,seed + i);
 
  taia_now(&t);
  taia_pack(tpack,&t);
  for (i = 0; i < 4; ++i)
    uint32_unpack(tpack + 4 * i,in + 4 + i);
 
  in[8] = getpid();
  in[9] = getppid();
  /* more space in 10 and 11, but this is probably enough */
}
 
unsigned int dns_random(unsigned int n)
{
  if (!n) return 0;
 
  if (!outleft) {
    if (!++in[0]) if (!++in[1]) if (!++in[2]) ++in[3];
    surf();
    outleft = 8;
  }
 
  return out[--outleft] % n;
}
 
int global_urandom_fd;
 
/* All needed for cryptography random functions, taken from djbdns */
 
void randombytes(uint8 *x,unsigned long long xlen) 
{
  int i;
 
  while (xlen > 0) {
    if (xlen < 1048576) i = xlen; 
    else i = 1048576;
 
    i = read(global_urandom_fd,x,i);
    if (i < 1) { sleep(1); continue; }
 
    x += i;
    xlen -= i;
  }
}
 
int crypto_random_init(void) 
{
   global_urandom_fd = open_read("/dev/urandom");
   if (global_urandom_fd < 0) {
     log_anon("opening /dev/urandom failed");
     return 0;
   }   
   randombytes((uint8 *) in,sizeof(in));
   return 1;
}
 
unsigned int crypto_random(unsigned int n)  
{
   if (!n) return 0;
 
   if (!outleft) {
     if (!++in[0]) if (!++in[1]) if (!++in[2]) ++in[3];
     surf();
     outleft = 8;
   }   
 
   return out[--outleft] % n;
}