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Common: Add Random utilities

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This makes it easier to generate random numbers or fill a buffer with
random data in a cryptographically secure way.

This also replaces existing usages of RNG functions in the codebase:

* <random> is pretty hard to use correctly, and std::random_device does
  not give enough guarantees about its results (it's
  implementation-defined, non cryptographically secure and could be
  deterministic on some platforms).
  Doing things correctly is error prone and verbose.

* rand() is terrible and should not be used especially in crypto code.
This commit is contained in:
Léo Lam
2018-05-21 15:48:17 +02:00
parent dd77ace56a
commit fff1db9730
10 changed files with 91 additions and 71 deletions
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26
Source/Core/Common/Crypto/ec.cpp
View File

@ -15,6 +15,8 @@
#include "Common/Common.h"
#include "Common/Crypto/bn.h"
#include "Common/Crypto/ec.h"
#include "Common/Random.h"
#include "Common/StringUtil.h"
#ifdef _MSC_VER
#pragma warning(push)
@ -230,30 +232,18 @@ static Point operator*(const u8* a, const Point& b)
return d;
}
static void silly_random(u8* rndArea, u8 count)
{
u16 i;
srand((unsigned)(time(nullptr)));
for (i = 0; i < count; i++)
{
rndArea[i] = rand();
}
}
Signature Sign(const u8* key, const u8* hash)
{
u8 e[30]{};
memcpy(e + 10, hash, 20);
// Changing random number generator to a lame one...
u8 m[30];
silly_random(m, sizeof(m));
// fp = fopen("/dev/random", "rb");
// if (fread(m, sizeof m, 1, fp) != 1)
// fatal("reading random");
// fclose(fp);
m[0] = 0;
do
{
// Generate 240 bits and keep 233.
Common::Random::Generate(m, sizeof(m));
m[0] &= 1;
} while (bn_compare(m, ec_N, sizeof(m)) >= 0);
Elt r = (m * ec_G).X();
if (bn_compare(r.data.data(), ec_N, 30) >= 0)