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| author | Adriano Cordova <adriano.cordova@canonical.com> | 2025-04-22 15:09:37 -0400 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2025-09-02 08:28:30 +0000 |
| commit | 2efffed93811a7c5d0e6d7d19f8ff112128ffd6a (patch) | |
| tree | 00ad5a89cbb236f988264b482e5a4f120d624392 | |
| parent | 77293f47116764abc7734bcef7dba69a9b83b696 (diff) | |
| download | edk2-2efffed93811a7c5d0e6d7d19f8ff112128ffd6a.zip edk2-2efffed93811a7c5d0e6d7d19f8ff112128ffd6a.tar.gz edk2-2efffed93811a7c5d0e6d7d19f8ff112128ffd6a.tar.bz2 | |
MdePkg/Library/BaseRngLib/Riscv: use CPU RNG instructions only
Generate random number using risc-v CPU RNG instructions only,
as for the other architectures. This is safer than using Mersenne
Twister from a seed, which is the current implementation, as the
latter is known to be cryptographically unsafe (e.g. see
https://www.schutzwerk.com/en/blog/attacking-a-rng/)
Signed-off-by: Adriano Cordova <adriano.cordova@canonical.com>
| -rw-r--r-- | MdePkg/Library/BaseRngLib/Riscv/Rng.c | 95 |
1 files changed, 3 insertions, 92 deletions
diff --git a/MdePkg/Library/BaseRngLib/Riscv/Rng.c b/MdePkg/Library/BaseRngLib/Riscv/Rng.c index 6a9b2ce..35b792f 100644 --- a/MdePkg/Library/BaseRngLib/Riscv/Rng.c +++ b/MdePkg/Library/BaseRngLib/Riscv/Rng.c @@ -19,75 +19,7 @@ #define SEED_RETRY_LOOPS 100
-// 64-bit Mersenne Twister implementation
-// A widely used pseudo random number generator. It performs bit shifts etc to
-// achieve the random number. It's output is determined by SEED value generated
-// by RISC-V SEED CSR"
-
-#define STATE_SIZE 312
-#define MIDDLE 156
-#define INIT_SHIFT 62
-#define TWIST_MASK 0xb5026f5aa96619e9ULL
-#define INIT_FACT 6364136223846793005ULL
-#define SHIFT1 29
-#define MASK1 0x5555555555555555ULL
-#define SHIFT2 17
-#define MASK2 0x71d67fffeda60000ULL
-#define SHIFT3 37
-#define MASK3 0xfff7eee000000000ULL
-#define SHIFT4 43
-
-#define LOWER_MASK 0x7fffffff
-#define UPPER_MASK (~(UINT64)LOWER_MASK)
-
-static UINT64 mState[STATE_SIZE];
-static UINTN mIndex = STATE_SIZE + 1;
-
-/**
- Initialize mState to defualt state.
-
- @param[in] S Input seed value
- **/
-STATIC
-VOID
-SeedRng (
- IN UINT64 S
- )
-{
- UINTN I;
-
- mIndex = STATE_SIZE;
- mState[0] = S;
-
- for (I = 1; I < STATE_SIZE; I++) {
- mState[I] = (INIT_FACT * (mState[I - 1] ^ (mState[I - 1] >> INIT_SHIFT))) + I;
- }
-}
-
-/**
- Initializes mState with entropy values. The initialization is based on the
- Seed value populated in mState[0] which then influences all the other values
- in the mState array. Later values are retrieved from the same array instead
- of calling trng instruction every time.
-
- **/
-STATIC
-VOID
-TwistRng (
- VOID
- )
-{
- UINTN I;
- UINT64 X;
-
- for (I = 0; I < STATE_SIZE; I++) {
- X = (mState[I] & UPPER_MASK) | (mState[(I + 1) % STATE_SIZE] & LOWER_MASK);
- X = (X >> 1) ^ (X & 1 ? TWIST_MASK : 0);
- mState[I] = mState[(I + MIDDLE) % STATE_SIZE] ^ X;
- }
-
- mIndex = 0;
-}
+// 64-bit CPU-based RNG using risc-v Zkr instruction
// Defined in Seed.S
extern UINT64
@@ -164,14 +96,7 @@ BaseRngLibConstructor ( VOID
)
{
- UINT64 Seed;
-
- if (Get64BitSeed (&Seed)) {
- SeedRng (Seed);
- return EFI_SUCCESS;
- } else {
- return EFI_UNSUPPORTED;
- }
+ return EFI_SUCCESS;
}
/**
@@ -241,24 +166,10 @@ ArchGetRandomNumber64 ( {
UINT64 Y;
- // Never initialized.
- if (mIndex > STATE_SIZE) {
+ if (!Get64BitSeed (&Y)) {
return FALSE;
}
- // Mersenne Twister
- if (mIndex == STATE_SIZE) {
- TwistRng ();
- }
-
- Y = mState[mIndex];
- Y ^= (Y >> SHIFT1) & MASK1;
- Y ^= (Y << SHIFT2) & MASK2;
- Y ^= (Y << SHIFT3) & MASK3;
- Y ^= Y >> SHIFT4;
-
- mIndex++;
-
*Rand = Y;
return TRUE;
}
|