util2: new load_fake_cryptodome() function

The eth-key and monero-python packages used in the test suite require the
keccak256() function provided by the pycryptodome (pycryptodomex) package.

pycryptodome is used in the MMGen code base only by these packages, and only for
testing.

This monkey-patch function eliminates dependency on pycryptodome on systems that
provide keccak256() via hashlib (>=OpenSSL 3.2, >=Python 3.13, latest MSYS2).

mmgen/util2.py

@@ -30,6 +30,23 @@ def die_pause(ev=0, s=''):
 	input('Press ENTER to exit')
 	sys.exit(ev)
 
+def load_fake_cryptodome():
+	import hashlib
+	try:
+		hashlib.new('keccak-256')
+	except ValueError:
+		return False
+
+	class FakeHash:
+		class keccak:
+			def new(data=b'', digest_bits=256):
+				assert digest_bits == 256
+				return hashlib.new('keccak-256', data=data)
+
+	sys.modules['Cryptodome.Hash'] = FakeHash
+	sys.modules['Crypto.Hash'] = FakeHash
+	return True
+
 def cffi_override_fixup():
 	from cffi import FFI
 	class FFI_override:
@@ -38,21 +55,26 @@ def cffi_override_fixup():
 	FFI.cdef = FFI_override.cdef
 
 # monkey-patch function: makes modules pycryptodome and pycryptodomex available to packages that
-# expect them (monero-python, eth-keys), regardless of which one is installed on system
+# expect them for the keccak256 function (monero-python, eth-keys), regardless of which one is
+# installed on the system
+#
+# if the hashlib keccak256 function is available (>=OpenSSL 3.2, >=Python 3.13), it’s used instead
+# and loaded as Crypto[dome].Hash via load_fake_cryptodome()
 def load_cryptodome(called=[]):
 	if not called:
-		cffi_override_fixup()
-		try:
-			import Crypto # Crypto == pycryptodome
-		except ImportError:
+		if not load_fake_cryptodome():
+			cffi_override_fixup()
 			try:
-				import Cryptodome # Crypto == pycryptodome
+				import Crypto # Crypto == pycryptodome
 			except ImportError:
-				die(2, 'Unable to import the ‘pycryptodome’ or ‘pycryptodomex’ package')
+				try:
+					import Cryptodome # Crypto == pycryptodome
+				except ImportError:
+					die(2, 'Unable to import the ‘pycryptodome’ or ‘pycryptodomex’ package')
+				else:
+					sys.modules['Crypto'] = Cryptodome # Crypto == pycryptodome
 			else:
-				sys.modules['Crypto'] = Cryptodome # Crypto == pycryptodome
-		else:
-			sys.modules['Cryptodome'] = Crypto # Cryptodome == pycryptodomex
+				sys.modules['Cryptodome'] = Crypto # Cryptodome == pycryptodomex
 		called.append(True)
 
 def get_hashlib_keccak():

test/gentest.py

@@ -582,7 +582,7 @@ vmsg = cfg._util.vmsg
 
 proto = cfg._proto
 
-if proto.coin == 'XMR':
+if proto.coin in ('ETH', 'ETC', 'XMR'):
 	from mmgen.util2 import load_cryptodome
 	load_cryptodome()