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LibJS/LibCrypto: Cleanup JS Math random() RNG

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This commit adds a convenience method to secure random for initializing
single types. It changes the random number generator in JS math random()
to use newer constants by the author as well as initializes it with a
higher quality seed.
This commit is contained in:
R-Goc 2025-04-11 22:12:04 +02:00 • committed by Andrew Kaster
parent a01d6ba246
commit d60543c2cb
Notes: github-actions[bot] 2025-05-15 13:42:08 +00:00
2 changed files with 19 additions and 6 deletions
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17
Libraries/LibJS/Runtime/MathObject.cpp
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@ -10,6 +10,7 @@
#include <AK/BuiltinWrappers.h>
#include <AK/Function.h>
#include <AK/Random.h>
#include <LibCrypto/SecureRandom.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/Iterator.h>
@ -800,12 +801,15 @@ JS_DEFINE_NATIVE_FUNCTION(MathObject::pow)
return pow_impl(vm, vm.argument(0), vm.argument(1));
}
class XorShift128PlusPlusRNG {
// http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf
class XorShift128PlusRNG {
public:
XorShift128PlusPlusRNG()
XorShift128PlusRNG()
{
u64 seed = get_random<u32>();
// Splitmix64 is used as xorshift is sensitive to being seeded with all 0s
u64 seed = Crypto::get_secure_random<u64>();
m_low = splitmix64(seed);
seed = Crypto::get_secure_random<u64>();
m_high = splitmix64(seed);
}
@ -824,6 +828,7 @@ private:
return z ^ (z >> 31);
}
// Apparently this set of constants is better: https://stackoverflow.com/a/34432126
u64 advance()
{
u64 s1 = m_low;
@ -831,8 +836,8 @@ private:
u64 const result = s0 + s1;
m_low = s0;
s1 ^= s1 << 23;
s1 ^= s1 >> 17;
s1 ^= s0 ^ (s0 >> 26);
s1 ^= s1 >> 18;
s1 ^= s0 ^ (s0 >> 5);
m_high = s1;
return result + s1;
}
@ -846,7 +851,7 @@ Value MathObject::random_impl()
// This function returns a Number value with positive sign, greater than or equal to +0𝔽 but strictly less than 1𝔽,
// chosen randomly or pseudo randomly with approximately uniform distribution over that range, using an
// implementation-defined algorithm or strategy.
static XorShift128PlusPlusRNG rng;
static XorShift128PlusRNG rng;
return Value(rng.get());
}