address sanitizer

boa_asan.py

# usage:
# install asan fork of vyper 0.3.10 (`pip install git+https://github.com/charles-cooper/vyper@asan`)
# change `import boa` to `import boa; import boa_asan` in scripts

from eth.exceptions import VMError
import boa.environment

class MemoryAccessViolation(VMError):
    pass


def _unpack_asan_ptr(asan_ptr, size):
    lo, hi, ptr = (asan_ptr >> 192), ((asan_ptr >> 128) & (2**64 - 1)), asan_ptr & (2**128 - 1)

    if lo == hi == 0:
        # raw pointers, not generated by the allocator
        return asan_ptr

    if lo >= hi:
        raise MemoryAccessViolation(f"bad asan ptr. | {lo} | {ptr} | {hi} | ({asan_ptr}) |")

    if ptr < lo:
        raise MemoryAccessViolation(f"tried to access {ptr} but bounds are | {lo} | ... | {hi} |")

    if ptr + size > hi:
        raise MemoryAccessViolation(f"tried to access {ptr + size} but bounds are | {lo} | ... | {hi} |")

    return ptr

# a py-evm eth.vm.Memory compatible implementation of memory
# which takes special pointers generated in vyper's `--asan`
# mode and sanitizes before every read and write
class SanitizingComputation(boa.environment.titanoboa_computation):
    def extend_memory(self, asan_ptr, size):
        start_position = _unpack_asan_ptr(asan_ptr, size)
        super().extend_memory(start_position, size)

    def memory_read(self, asan_ptr, size):
        start_position = _unpack_asan_ptr(asan_ptr, size)
        return super().memory_read(start_position, size)

    def memory_read_bytes(self, asan_ptr, size):
        start_position = _unpack_asan_ptr(asan_ptr, size)
        return super().memory_read_bytes(start_position, size)

    def memory_write(self, asan_ptr, size, value):
        start_position = _unpack_asan_ptr(asan_ptr, size)
        return super().memory_write(start_position, size, value)

# monkey patch
boa.environment.titanoboa_computation = SanitizingComputation
boa.env._init_vm()  # reinitialize vm.state.computation_class