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using System;
using System.Threading;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Prng;
using Org.BouncyCastle.Crypto.Utilities;
namespace Org.BouncyCastle.Security
{
public class SecureRandom
: Random
{
private static long counter = DateTime.UtcNow.Ticks;
private static long NextCounterValue()
{
return Interlocked.Increment(ref counter);
}
private static readonly SecureRandom master = new SecureRandom(new CryptoApiRandomGenerator());
private static SecureRandom Master
{
get { return master; }
}
private static DigestRandomGenerator CreatePrng(string digestName, bool autoSeed)
{
IDigest digest = DigestUtilities.GetDigest(digestName);
if (digest == null)
return null;
DigestRandomGenerator prng = new DigestRandomGenerator(digest);
if (autoSeed)
{
prng.AddSeedMaterial(NextCounterValue());
prng.AddSeedMaterial(GetNextBytes(Master, digest.GetDigestSize()));
}
return prng;
}
public static byte[] GetNextBytes(SecureRandom secureRandom, int length)
{
byte[] result = new byte[length];
secureRandom.NextBytes(result);
return result;
}
/// <summary>
/// Create and auto-seed an instance based on the given algorithm.
/// </summary>
/// <remarks>Equivalent to GetInstance(algorithm, true)</remarks>
/// <param name="algorithm">e.g. "SHA256PRNG"</param>
public static SecureRandom GetInstance(string algorithm)
{
return GetInstance(algorithm, true);
}
/// <summary>
/// Create an instance based on the given algorithm, with optional auto-seeding
/// </summary>
/// <param name="algorithm">e.g. "SHA256PRNG"</param>
/// <param name="autoSeed">If true, the instance will be auto-seeded.</param>
public static SecureRandom GetInstance(string algorithm, bool autoSeed)
{
if (algorithm == null)
throw new ArgumentNullException(nameof(algorithm));
if (algorithm.EndsWith("PRNG", StringComparison.OrdinalIgnoreCase))
{
string digestName = algorithm.Substring(0, algorithm.Length - "PRNG".Length);
DigestRandomGenerator prng = CreatePrng(digestName, autoSeed);
if (prng != null)
return new SecureRandom(prng);
}
throw new ArgumentException("Unrecognised PRNG algorithm: " + algorithm, "algorithm");
}
protected readonly IRandomGenerator generator;
public SecureRandom()
: this(CreatePrng("SHA256", true))
{
}
/// <summary>Use the specified instance of IRandomGenerator as random source.</summary>
/// <remarks>
/// This constructor performs no seeding of either the <c>IRandomGenerator</c> or the
/// constructed <c>SecureRandom</c>. It is the responsibility of the client to provide
/// proper seed material as necessary/appropriate for the given <c>IRandomGenerator</c>
/// implementation.
/// </remarks>
/// <param name="generator">The source to generate all random bytes from.</param>
public SecureRandom(IRandomGenerator generator)
: base(0)
{
this.generator = generator;
}
public virtual byte[] GenerateSeed(int length)
{
return GetNextBytes(Master, length);
}
public virtual void SetSeed(byte[] seed)
{
generator.AddSeedMaterial(seed);
}
public virtual void SetSeed(long seed)
{
generator.AddSeedMaterial(seed);
}
public override int Next()
{
return NextInt() & int.MaxValue;
}
public override int Next(int maxValue)
{
if (maxValue < 2)
{
if (maxValue < 0)
throw new ArgumentOutOfRangeException("maxValue", "cannot be negative");
return 0;
}
int bits;
// Test whether maxValue is a power of 2
if ((maxValue & (maxValue - 1)) == 0)
{
bits = NextInt() & int.MaxValue;
return (int)(((long)bits * maxValue) >> 31);
}
int result;
do
{
bits = NextInt() & int.MaxValue;
result = bits % maxValue;
}
while (bits - result + (maxValue - 1) < 0); // Ignore results near overflow
return result;
}
public override int Next(int minValue, int maxValue)
{
if (maxValue <= minValue)
{
if (maxValue == minValue)
return minValue;
throw new ArgumentException("maxValue cannot be less than minValue");
}
int diff = maxValue - minValue;
if (diff > 0)
return minValue + Next(diff);
for (;;)
{
int i = NextInt();
if (i >= minValue && i < maxValue)
return i;
}
}
public override void NextBytes(byte[] buf)
{
generator.NextBytes(buf);
}
public virtual void NextBytes(byte[] buf, int off, int len)
{
generator.NextBytes(buf, off, len);
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public override void NextBytes(Span<byte> buffer)
{
if (generator != null)
{
generator.NextBytes(buffer);
}
else
{
byte[] tmp = new byte[buffer.Length];
NextBytes(tmp);
tmp.CopyTo(buffer);
}
}
#endif
private static readonly double DoubleScale = 1.0 / Convert.ToDouble(1L << 53);
public override double NextDouble()
{
ulong x = (ulong)NextLong() >> 11;
return Convert.ToDouble(x) * DoubleScale;
}
public virtual int NextInt()
{
byte[] bytes = new byte[4];
NextBytes(bytes);
return (int)Pack.BE_To_UInt32(bytes, 0);
}
public virtual long NextLong()
{
byte[] bytes = new byte[8];
NextBytes(bytes);
return (long)Pack.BE_To_UInt64(bytes, 0);
}
}
}
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