Use Cryptographically Secure Pseudo-Random Generator for Order Salt Generation

py_clob_client_v2/order_utils/utils.py

@@ -1,6 +1,30 @@
-import random
-import time
+import secrets
+
+# Number of random bits used for an order salt.
+#
+# Capped at 53 because the CLOB wire contract carries `salt` as a JSON number.
+# JSON numbers are IEEE-754 doubles for many consumers and represent integers
+# exactly only up to 2**53 - 1, so a wider salt could be rounded during transport
+# while the EIP-712 signature was produced over the original value. The server
+# would then reconstruct a different digest and reject the order as having an
+# invalid signature. 53 bits still gives roughly 9.0e15 of collision space.
+SALT_BITS = 53
 
 
 def generate_order_salt() -> str:
-    return str(int(random.random() * (time.time_ns() // 1_000_000)))
+    """
+    Generate a cryptographically random order salt.
+
+    The salt is the only entropy that distinguishes two otherwise identical
+    orders in the EIP-712 digest, so it is a security-relevant value: a
+    predictable salt lets a third party precompute an order hash before it is
+    broadcast, and a colliding salt produces a duplicate order hash.
+
+    This previously returned ``int(random.random() * time.time_ns() // 1_000_000)``.
+    ``random.random()`` is the Mersenne Twister, which is not a cryptographically
+    secure generator -- its entire 19937-bit state can be recovered from 624
+    consecutive outputs, after which every future salt is predictable -- and the
+    millisecond clock it was multiplied by is close to public knowledge.
+    ``secrets`` draws from the operating system CSPRNG and needs no clock input.
+    """
+    return str(secrets.randbits(SALT_BITS))