/* ISC license. */

#include <unistd.h>
#include <stdint.h>
#include <skalibs/uint32.h>
#include <skalibs/tai.h>
#include <skalibs/sha1.h>

/*
   Writes 160 bytes of crap into s.
   Certainly not cryptographically secure or 100% unpredictable,
   but we're only using this to help shuffle the entropy of
   /dev/urandom or to init an internal SURF PRNG. 
   iow: we are CS iff the system's RNG is CS.
*/

void random_makeseed (char *s)
{
  SHA1Schedule bak = SHA1_INIT() ;
  {
    tain_t now ;
    char tmp[256] ;
    uint32_t x = getpid() ;
    uint32_pack(tmp, x) ;
    x = getppid() ;
    uint32_pack(tmp + 4, x) ;
    tain_now(&now) ;
    tain_pack(tmp + 8, &now) ;
    sha1_update(&bak, tmp, 8 + TAIN_PACK) ;
    gethostname(tmp, 256) ;
    sha1_update(&bak, tmp, 256) ;
    sha1_final(&bak, tmp) ;
    sha1_init(&bak) ;
    sha1_update(&bak, tmp, 20) ;
  }  
  {
    char i = 0 ;
    for (; i < 8 ; i++)
    {
      SHA1Schedule ctx = bak ;
      sha1_update(&ctx, &i, 1) ;
      sha1_final(&ctx, s + 20*i) ;
    }
  }
}