Fix RandomX validation exploit with difficulty reset, improve build system
- One-time difficulty reset to minimum for 17 blocks at activation height - Separate RandomX build dirs for linux/win64 cross-compilation - Add build target tracking to auto-clean on target switch - Automated win64 release packaging to release-win64/ - Add build artifacts to .gitignore - Miner memory diagnostics and large-page dataset fallback
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dan_s
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doc/CHANGELOG-randomx-optimization.md
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doc/CHANGELOG-randomx-optimization.md
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# Changelog: RandomX Mining Optimization
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## Summary
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Optimizes RandomX miner memory usage by replacing per-thread dataset/cache allocation with a shared `RandomXDatasetManager`. Reduces memory footprint from ~2.3GB × N threads to ~2.3GB total.
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## Problem
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The original RandomX miner implementation allocated a full RandomX dataset (~2GB) and cache (~256MB) for each mining thread. With multiple threads, this quickly exhausted available memory:
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- 4 threads: ~9.2GB
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- 8 threads: ~18.4GB
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- 16 threads: ~36.8GB
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## Solution
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Implemented a shared `RandomXDatasetManager` that allocates a single dataset and cache, shared by all miner threads via read-only access (explicitly supported by RandomX design).
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## Changes
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### `src/miner.cpp`
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- **Added `RandomXDatasetManager` class:**
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- Manages a single shared RandomX cache and dataset.
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- Thread-safe key updates using `boost::shared_mutex` (readers-writer lock).
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- `Initialize(key)`: Allocates cache and dataset, initializes with key, builds dataset using all CPU cores.
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- `UpdateKey(newKey)`: Acquires exclusive lock, reinitializes cache with new key, rebuilds dataset.
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- `GetDataset()`: Returns pointer to shared dataset for VM creation.
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- `AcquireSharedLock()` / `ReleaseSharedLock()`: Miner threads hold shared lock while hashing to prevent key updates mid-hash.
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- `Shutdown()`: Releases all RandomX resources.
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- **Modified `GenerateBitcoins()`:**
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- Initializes `RandomXDatasetManager` with initial key before spawning miner threads.
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- Calls `Shutdown()` when mining stops.
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- **Modified `RandomXMiner()`:**
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- Creates lightweight per-thread VM using shared dataset (`randomx_create_vm(..., manager.GetDataset())`).
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- Acquires shared lock before hashing, releases after.
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- On key rotation: releases shared lock, calls `manager.UpdateKey()`, reacquires shared lock, recreates VM.
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- Cleanup only destroys thread's VM — dataset/cache owned by manager.
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## Memory Usage
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| Threads | Before | After |
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|---------|--------|-------|
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| 1 | ~2.3GB | ~2.3GB |
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| 4 | ~9.2GB | ~2.3GB |
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| 8 | ~18.4GB | ~2.3GB |
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| 16 | ~36.8GB | ~2.3GB |
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## Thread Safety
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- RandomX dataset is read-only after initialization — safe to share across threads.
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- `boost::shared_mutex` ensures:
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- Multiple threads can hash concurrently (shared lock).
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- Key updates are exclusive (exclusive lock blocks until all shared locks release).
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- No thread hashes with stale dataset during key change.
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## Files Modified
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| File | Lines Added | Lines Removed |
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|------|-------------|---------------|
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| `src/miner.cpp` | ~80 | ~20 |
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doc/CHANGELOG-randomx-validation.md
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doc/CHANGELOG-randomx-validation.md
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# Changelog: RandomX Validation Bug Fix
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## Summary
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Fixes a critical exploit allowing miners on RandomX-based Hush Arrakis Chains (HACs) to bypass RandomX proof-of-work validation entirely. Adds proper RandomX solution verification to the block validation pipeline, fixes the miner's RandomX input construction, and introduces per-chain activation heights.
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## Bug Description
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Three issues combined to allow the bypass:
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1. `CheckEquihashSolution()` returned `true` immediately for non-Equihash chains, never verifying the RandomX solution stored in `nSolution`.
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2. `CheckProofOfWork()` checked the standard SHA-256d `GetHash()` against the difficulty target instead of a RandomX hash, allowing miners to brute-force the cheap hash.
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3. The miner passed `&randomxInput, sizeof randomxInput` (the address and size of a `CDataStream` struct) to `randomx_calculate_hash()` instead of the actual serialized data, producing non-deterministic hashes.
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A malicious miner could put arbitrary bytes in `nSolution`, iterate nonces until the standard header hash met the target, and the block would pass all validation — completely bypassing RandomX CPU-hardness.
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## Changes
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### `src/primitives/block.h`
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- Added `CRandomXInput` class (modeled after `CEquihashInput`) that serializes the block header **including `nNonce`** but **excluding `nSolution`**, providing deterministic and reproducible input for RandomX hashing.
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### `src/hush_globals.h`
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- Added `int32_t ASSETCHAINS_RANDOMX_VALIDATION = -1` global variable to hold the per-chain activation height (`-1` = disabled).
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### `src/hush_defs.h`
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- Added `extern int32_t ASSETCHAINS_RANDOMX_VALIDATION` declaration.
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### `src/pow.h`
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- Added declaration for `bool CheckRandomXSolution(const CBlockHeader *pblock, int32_t height)`.
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- Added declarations for `int GetRandomXInterval()` and `int GetRandomXBlockLag()` (moved from `miner.cpp`).
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### `src/pow.cpp`
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- Added `#include "RandomX/src/randomx.h"` and `#include <mutex>`.
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- Moved `GetRandomXInterval()` and `GetRandomXBlockLag()` definitions here from `miner.cpp` so they are accessible from both the miner and the validator.
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- Implemented `CheckRandomXSolution()`:
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- Returns `true` immediately for non-RandomX chains, pre-activation heights, and when `HUSH_LOADINGBLOCKS != 0`.
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- Validates `nSolution` is exactly `RANDOMX_HASH_SIZE` (32) bytes.
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- Derives the correct RandomX key for the given height (initial key from chain params, or block-hash key after rotation interval).
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- Serializes the block header via `CRandomXInput` into a `CDataStream`.
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- Calls `randomx_calculate_hash()` with the correct data pointer (`&ss[0]`) and size (`ss.size()`).
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- Compares the computed hash against `pblock->nSolution`.
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- Caches the RandomX VM and cache between calls (protected by mutex), re-initializing only when the key changes.
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### `src/main.cpp`
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- In `CheckBlockHeader()`: added `CheckRandomXSolution()` call inside the `fCheckPOW` block, after the existing `CheckEquihashSolution()` call. Invalid RandomX solutions are rejected with `DoS(100)`.
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### `src/hush_bitcoind.h`
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- Added `#include "pow.h"`.
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- In `hush_checkPOW()`: added `CheckRandomXSolution()` call after the existing `CheckEquihashSolution()` call.
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### `src/miner.cpp`
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- Changed `GetRandomXInterval()` and `GetRandomXBlockLag()` from inline definitions to forward declarations (definitions moved to `pow.cpp`).
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- Fixed RandomX input construction in `RandomXMiner()`:
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- Uses `CRandomXInput` to serialize the block header without `nSolution` (instead of serializing the entire block).
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- Passes `&randomxInput[0], randomxInput.size()` to `randomx_calculate_hash()` (instead of `&randomxInput, sizeof randomxInput`).
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- Added `SetSkipRandomXValidation(true/false)` around `TestBlockValidity()` to avoid double-validation OOM.
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- Added null-checks before `randomx_destroy_vm()` to prevent double-free crashes.
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### `src/hush_utils.h`
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- After `ASSETCHAINS_ALGO` and `SMART_CHAIN_SYMBOL` are set during chain initialization, sets `ASSETCHAINS_RANDOMX_VALIDATION` per chain:
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- `DRAGONX`: `1` (TBD: set to coordinated upgrade height)
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- `TUMIN`: `1` (TBD: set to coordinated upgrade height)
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- All other RandomX HACs: `1` (enforced from height 1)
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- Non-RandomX chains: remains `-1` (disabled)
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## Activation Heights
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| Chain | Height | Notes |
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|-------|--------|-------|
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| DRAGONX | TBD | Existing chain, needs coordinated upgrade |
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| TUMIN | TBD | Existing chain, needs coordinated upgrade |
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| All other RandomX HACs | 1 | Enforced from genesis+1 |
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## Files Modified
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| File | Lines Added | Lines Removed |
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|------|-------------|---------------|
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| `src/primitives/block.h` | ~20 | 0 |
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| `src/hush_globals.h` | 1 | 0 |
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| `src/hush_defs.h` | 1 | 0 |
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| `src/pow.h` | 9 | 0 |
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| `src/pow.cpp` | ~105 | 0 |
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| `src/main.cpp` | 2 | 0 |
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| `src/hush_bitcoind.h` | 6 | 0 |
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| `src/miner.cpp` | 5 | 5 |
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| `src/hush_utils.h` | 10 | 0 |
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