third_party/WebKit/Source/wtf/CryptographicallyRandomNumber.cpp

   1 /*
   2  * Copyright (c) 1996, David Mazieres <dm@uun.org>
   3  * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 /*
  19  * Arc4 random number generator for OpenBSD.
  20  *
  21  * This code is derived from section 17.1 of Applied Cryptography,
  22  * second edition, which describes a stream cipher allegedly
  23  * compatible with RSA Labs "RC4" cipher (the actual description of
  24  * which is a trade secret).  The same algorithm is used as a stream
  25  * cipher called "arcfour" in Tatu Ylonen's ssh package.
  26  *
  27  * RC4 is a registered trademark of RSA Laboratories.
  28  */
  29
  30 #include "config.h"
  31 #include "wtf/CryptographicallyRandomNumber.h"
  32
  33 #include "wtf/StdLibExtras.h"
  34 #include "wtf/Threading.h"
  35 #include "wtf/ThreadingPrimitives.h"
  36
  37 namespace WTF {
  38
  39 static RandomNumberSource sourceFunction;
  40
  41 void setRandomSource(RandomNumberSource source)
  42 {
  43     sourceFunction = source;
  44 }
  45
  46 namespace {
  47
  48 class ARC4Stream {
  49 public:
  50     ARC4Stream();
  51
  52     uint8_t i;
  53     uint8_t j;
  54     uint8_t s[256];
  55 };
  56
  57 class ARC4RandomNumberGenerator {
  58     WTF_MAKE_FAST_ALLOCATED(ARC4RandomNumberGenerator);
  59 public:
  60     ARC4RandomNumberGenerator();
  61
  62     uint32_t randomNumber();
  63     void randomValues(void* buffer, size_t length);
  64
  65 private:
  66     inline void addRandomData(unsigned char *data, int length);
  67     void stir();
  68     void stirIfNeeded();
  69     inline uint8_t getByte();
  70     inline uint32_t getWord();
  71
  72     ARC4Stream m_stream;
  73     int m_count;
  74     Mutex m_mutex;
  75 };
  76
  77 ARC4Stream::ARC4Stream()
  78 {
  79     for (int n = 0; n < 256; n++)
  80         s[n] = static_cast<uint8_t>(n);
  81     i = 0;
  82     j = 0;
  83 }
  84
  85 ARC4RandomNumberGenerator::ARC4RandomNumberGenerator()
  86     : m_count(0)
  87 {
  88 }
  89
  90 void ARC4RandomNumberGenerator::addRandomData(unsigned char* data, int length)
  91 {
  92     m_stream.i--;
  93     for (int n = 0; n < 256; n++) {
  94         m_stream.i++;
  95         uint8_t si = m_stream.s[m_stream.i];
  96         m_stream.j += si + data[n % length];
  97         m_stream.s[m_stream.i] = m_stream.s[m_stream.j];
  98         m_stream.s[m_stream.j] = si;
  99     }
 100     m_stream.j = m_stream.i;
 101 }
 102
 103 void ARC4RandomNumberGenerator::stir()
 104 {
 105     unsigned char randomness[128];
 106     size_t length = sizeof(randomness);
 107     (*sourceFunction)(randomness, length);
 108     addRandomData(randomness, length);
 109
 110     // Discard early keystream, as per recommendations in:
 111     // http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
 112     for (int i = 0; i < 256; i++)
 113         getByte();
 114     m_count = 1600000;
 115 }
 116
 117 void ARC4RandomNumberGenerator::stirIfNeeded()
 118 {
 119     if (m_count <= 0)
 120         stir();
 121 }
 122
 123 uint8_t ARC4RandomNumberGenerator::getByte()
 124 {
 125     m_stream.i++;
 126     uint8_t si = m_stream.s[m_stream.i];
 127     m_stream.j += si;
 128     uint8_t sj = m_stream.s[m_stream.j];
 129     m_stream.s[m_stream.i] = sj;
 130     m_stream.s[m_stream.j] = si;
 131     return (m_stream.s[(si + sj) & 0xff]);
 132 }
 133
 134 uint32_t ARC4RandomNumberGenerator::getWord()
 135 {
 136     uint32_t val;
 137     val = getByte() << 24;
 138     val |= getByte() << 16;
 139     val |= getByte() << 8;
 140     val |= getByte();
 141     return val;
 142 }
 143
 144 uint32_t ARC4RandomNumberGenerator::randomNumber()
 145 {
 146     MutexLocker locker(m_mutex);
 147
 148     m_count -= 4;
 149     stirIfNeeded();
 150     return getWord();
 151 }
 152
 153 void ARC4RandomNumberGenerator::randomValues(void* buffer, size_t length)
 154 {
 155     MutexLocker locker(m_mutex);
 156
 157     unsigned char* result = reinterpret_cast<unsigned char*>(buffer);
 158     stirIfNeeded();
 159     while (length--) {
 160         m_count--;
 161         stirIfNeeded();
 162         result[length] = getByte();
 163     }
 164 }
 165
 166 ARC4RandomNumberGenerator& sharedRandomNumberGenerator()
 167 {
 168     AtomicallyInitializedStaticReference(ARC4RandomNumberGenerator, randomNumberGenerator, new ARC4RandomNumberGenerator);
 169     return randomNumberGenerator;
 170 }
 171
 172 }
 173
 174
 175 uint32_t cryptographicallyRandomNumber()
 176 {
 177     return sharedRandomNumberGenerator().randomNumber();
 178 }
 179
 180 void cryptographicallyRandomValues(void* buffer, size_t length)
 181 {
 182     sharedRandomNumberGenerator().randomValues(buffer, length);
 183 }
 184
 185 }