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/* randomness.pmod 
 * 
 * Assorted stronger or weaker randomnumber generators. 
 */ 
 
/* These devices tries to collect entropy from the environment. 
 * They differ in behaviour when they run low on entropy, /dev/random 
 * will block if it can't provide enough random bits, while /dev/urandom 
 * will degenerate into a reasonably strong pseudo random generator */ 
 
#define RANDOM_DEVICE "/dev/random" 
#define PRANDOM_DEVICE "/dev/urandom" 
 
/* Collect somewhat random data from the environment. Unfortunately, 
 * this is quite system dependent */ 
#define PATH  "/usr/sbin:/usr/etc:/usr/bin/:/sbin/:/etc:/bin" 
 
#ifndef __NT__ 
#define SYSTEM_COMMANDS ({ "last -256", "arp -a", \ 
                        "netstat -anv","netstat -mv","netstat -sv", \ 
                        "uptime","ps -fel","ps aux", \ 
                        "vmstat -s","vmstat -M", \ 
                        "iostat","iostat -cdDItx"}) 
#else 
#define SYSTEM_COMMANDS ({ "mem /c", "arp -a", "vol", "dir", "net view", \ 
    "net statistics workstation","net statistics server", "net view" \ 
    "net user" }) 
#endif 
                       
#define PRIVATE 
                       
PRIVATE object global_rc4; 
 
PRIVATE string some_entropy() 
{ 
  string res; 
  object parent_pipe, child_pipe; 
  mapping env=getenv(); 
 
  parent_pipe = Stdio.File(); 
  child_pipe = parent_pipe->pipe(); 
  if (!child_pipe) 
    throw( ({ "Crypto.random->popen: couldn't create pipe\n", backtrace() }) ); 
 
 
#ifndef __NT__ 
  object null=Stdio.File("/dev/null","rw"); 
  env["PATH"]=PATH; 
#else 
  object null=Stdio.File("nul:","rw"); 
#endif 
   
  foreach(SYSTEM_COMMANDS, string cmd) 
    { 
      catch { 
        Process.create_process(Process.split_quoted_string(cmd), 
                               (["stdin":null,"stdout":child_pipe,"stderr":null])); 
      }; 
    } 
 
  destruct(child_pipe); 
   
  return parent_pipe->read(); 
} 
 
 
class pike_random { 
  string read(int len) 
  { 
    return sprintf("%@c", Array.map(allocate(len), lambda(int dummy) 
                                    { 
                                      return random(256); 
                                    } )); 
  } 
} 
 
class rc4_random { 
  inherit Crypto.rc4 : rc4; 
 
  void create(string secret) 
  { 
    object hash = Crypto.sha(); 
    hash->update(secret); 
     
    rc4::set_encrypt_key(hash->digest()); 
  } 
 
  string read(int len) 
  { 
    return rc4::crypt(replace(allocate(len), 0, "\47") * ""); 
  } 
} 
 
object reasonably_random() 
{ 
  if (file_stat(PRANDOM_DEVICE)) 
  { 
    object res = Stdio.File(); 
    if (res->open(PRANDOM_DEVICE, "r")) 
      return res; 
  } 
 
  if (global_rc4) 
    return global_rc4; 
   
  string seed = some_entropy(); 
  if (strlen(seed) > 2000) 
    return (global_rc4 = rc4_random(sprintf("%4c%O%s", time(), _memory_usage(), seed))); 
   
  throw( ({ "Crypto.randomness.reasonably_random: No source found\n", backtrace() }) ); 
} 
 
object really_random(int|void may_block) 
{ 
  object res = Stdio.File(); 
  if (may_block && file_stat(RANDOM_DEVICE)) 
  { 
    if (res->open(RANDOM_DEVICE, "r")) 
      return res; 
  } 
 
  if (file_stat(PRANDOM_DEVICE)) 
  { 
    if (res->open(PRANDOM_DEVICE, "r")) 
      return res; 
  } 
     
  throw( ({ "Crypto.randomness.really_random: No source found\n", backtrace() }) ); 
}