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/* $Id$ 
 */ 
 
//! Assorted stronger or weaker randomnumber generators. 
//! These devices try 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 
 
#pike __REAL_VERSION__ 
 
static constant RANDOM_DEVICE = "/dev/random"; 
static constant PRANDOM_DEVICE = "/dev/urandom"; 
 
/* Collect somewhat random data from the environment. Unfortunately, 
 * this is quite system dependent 
 */ 
static constant PATH = "/usr/sbin:/usr/etc:/usr/bin/:/sbin/:/etc:/bin"; 
 
#ifndef __NT__ 
static constant 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 
static constant SYSTEM_COMMANDS = ({ 
  "mem /c", "arp -a", "vol", "dir", "net view", 
  "net statistics workstation","net statistics server", 
  "net user" 
}); 
#endif 
 
// *****************************                       
#define private 
                       
private object global_arcfour; 
 
//    Executes several programs to generate some entropy from their output. 
private string some_entropy() 
{ 
#ifdef __NT__ 
  object ctx = Crypto.nt.CryptAcquireContext(0, 0, Crypto.nt.PROV_RSA_FULL, 
                                             Crypto.nt.CRYPT_VERIFYCONTEXT 
                                             /*|Crypto.nt.CRYPT_SILENT*/); 
  if(!ctx) 
    error( "Crypto.random: couldn't create crypto context.\n" ); 
 
  string res = ctx->CryptGenRandom(8192); 
 
  if(!res) 
    error( "Crypto.random: couldn't generate randomness.\n" ); 
 
  destruct(ctx); 
 
  return res; 
#else /* !__NT__ */ 
  string res; 
  object parent_pipe, child_pipe; 
  mapping env=getenv()+([]); 
 
  parent_pipe = Stdio.File(); 
  child_pipe = parent_pipe->pipe(); 
  if (!child_pipe) 
    error( "Crypto.random->popen: couldn't create pipe.\n" ); 
 
  object null=Stdio.File("/dev/null","rw"); 
  env["PATH"]=PATH; 
   
  foreach(SYSTEM_COMMANDS, string cmd) 
    { 
      catch { 
        Process.create_process(Process.split_quoted_string(cmd), 
                                       (["stdin":null, 
                                        "stdout":child_pipe, 
                                        "stderr":null, 
                                        "env":env])); 
      }; 
    } 
 
  destruct(child_pipe); 
   
  return parent_pipe->read(); 
#endif 
} 
 
 
//! A pseudo random generator based on the ordinary random() function. 
class pike_random { 
 
  //! Returns a string of length len with pseudo random values. 
  string read(int len) 
  { 
#if 1 // major optimization /Hubbe 
      return random_string(len); 
#else 
#if 1 // 30% optimization /Hubbe 
    string ret=""; 
    if(len>=16384) 
    { 
      array x=allocate(16384,random); 
      for(int e=0;e<(len/16384);e++) ret+=(string)x(256); 
    } 
    ret+=(string)allocate(len % 16384, random)(256); 
    return ret; 
#else 
    if (len > 16384) return read(len/2)+read(len-len/2); 
    return (string)allocate(len, random)(256); 
#endif 
#endif 
  } 
} 
 
#if constant(Crypto.arcfour) 
//! A pseudo random generator based on the arcfour crypto. 
class arcfour_random { 
 
  inherit Crypto.arcfour : arcfour; 
 
  //! Initialize and seed the arcfour random generator. 
  void create(string secret) 
  { 
    object hash = Crypto.sha(); 
    hash->update(secret); 
     
    arcfour::set_encrypt_key(hash->digest()); 
  } 
 
  //! Return a string of the next len random characters from the 
  //! arcfour random generator. 
  string read(int len) 
  { 
    if (len > 16384) return read(len/2)+read(len-len/2); 
    return arcfour::crypt("\47" * len); 
  } 
} 
 
#endif /* constant(Crypto.arcfour) */ 
 
//! 
object reasonably_random() 
{ 
  if (file_stat(PRANDOM_DEVICE)) 
  { 
    object res = Stdio.File(); 
    if (res->open(PRANDOM_DEVICE, "r")) 
      return res; 
  } 
 
  if (global_arcfour) 
    return global_arcfour; 
 
#if constant(Crypto.arcfour)   
  string seed = some_entropy(); 
  if (strlen(seed) > 2000) 
    return (global_arcfour = arcfour_random(sprintf("%4c%O%s", time(), _memory_usage(), seed))); 
#else /* !constant(Crypto.arcfour) */ 
  /* Not very random, but at least a fallback... */ 
  return global_arcfour = pike_random(); 
#endif /* constant(Crypto.arcfour) */ 
  error( "Crypto.randomness.reasonably_random: No source found.\n" ); 
} 
 
//! 
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; 
  } 
     
  error( "Crypto.randomness.really_random: No source found.\n" ); 
}