es_ftw.cpp

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/*************************************************
* FTW EntropySource Source File                  *
* (C) 1999-2002 The Botan Project                *
*************************************************/

#ifndef _XOPEN_SOURCE
  #define _XOPEN_SOURCE 500
#endif
#ifndef _XOPEN_SOURCE_EXTENDED
  #define _XOPEN_SOURCE_EXTENDED 1
#endif

#include <botan/es_ftw.h>
#include <botan/util.h>
#include <fstream>
#include <cstring>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <dirent.h>

namespace Botan {

/*************************************************
* FTW_EntropySource Constructor                  *
*************************************************/
FTW_EntropySource::FTW_EntropySource(const std::string& p) : path(p)
   {
   do_poll(64);
   }

/*************************************************
* Fast Poll                                      *
*************************************************/
u32bit FTW_EntropySource::fast_poll(byte out[], u32bit length)
   {
   if(position == buffer.size())
      do_poll(128);
   u32bit copied = std::min(length, buffer.size() - position);
   copy_mem(out, buffer + position, copied);
   position += copied;
   return copied;
   }

/*************************************************
* Slow Poll                                      *
*************************************************/
u32bit FTW_EntropySource::slow_poll(byte out[], u32bit length)
   {
   do_poll(2*1024);

   u32bit copied = std::min(length, buffer.size());
   copy_mem(out, buffer + position, copied);
   position += copied;

   return copied;
   }

/*************************************************
* Gather Entropy                                 *
*************************************************/
void FTW_EntropySource::do_poll(u32bit limit)
   {
   files_read = 0;
   gather_from_dir(path, limit);
   position = 0;
   }

/*************************************************
* Gather Entropy From Directory Tree             *
*************************************************/
void FTW_EntropySource::gather_from_dir(const std::string& dirname,
                                        u32bit limit)
   {
   if(dirname == "")
      return;

   DIR* dir = opendir(dirname.c_str());
   if(dir == 0)
      return;

   dirent* entry = readdir(dir);
   while(entry && (files_read < limit))
      {
      if((std::strcmp(entry->d_name, ".") == 0) ||
         (std::strcmp(entry->d_name, "..") == 0))
         { entry = readdir(dir); continue; }

      std::string filename = dirname + '/' + entry->d_name;

      struct stat stat_buf;
      if(lstat(filename.c_str(), &stat_buf) == -1)
         { entry = readdir(dir); continue; }

      if(S_ISREG(stat_buf.st_mode))
         gather_from_file(filename);
      if(S_ISDIR(stat_buf.st_mode))
         gather_from_dir(filename, limit - files_read);
      entry = readdir(dir);
      }
   closedir(dir);
   }

/*************************************************
* Gather Entropy From A File                     *
*************************************************/
void FTW_EntropySource::gather_from_file(const std::string& filename)
   {
   int fd = open(filename.c_str(), O_RDONLY);
   if(fd == -1) return;

   files_read++;

   SecureVector<byte> read_buf(buffer.size());

   ssize_t got = read(fd, read_buf, buffer.size());
   if(got < 0) got = 0;
   xor_buf(buffer, read_buf, got);

   close(fd);
   }

}