Public commit record
78/100 · Adequate
What the developer wrote
Authored by SomberNight
crypto: add runtime sanity checks
- if one of the critical hash functions is broken, we should panic early
(sha256/sha512/hash160), as the consequences could be devastating.
- sha512 is used for bip32
- sha256/hash160 are used for deriving addresses
- but we might as well also test the symmetric ciphers
- though those checks are a bit slower
- but I would prefer erring on the side of paranoia and doing the check
naive benchmarks:
(it's not AES that is slow, but the first invocations of the symmetric ciphers)
```
>>> from electrum.crypto import *
backends: HAS_CRYPTODOME=True, HAS_CRYPTOGRAPHY=False
time taken by 'hash functions1': 0.065 msec
time taken by 'aes1': 3.377 msec
time taken by 'aes2': 0.047 msec
time taken by 'chacha20': 0.182 msec
time taken by 'chacha20-poly1305': 0.405 msec
total time taken: 4.235 msec
```
```
>>> from electrum.crypto import *
backends: HAS_CRYPTODOME=False, HAS_CRYPTOGRAPHY=True
time taken by 'hash functions1': 0.064 msec
time taken by 'aes1': 7.131 msec
time taken by 'aes2': 0.040 msec
time taken by 'chacha20': 0.056 msec
time taken by 'chacha20-poly1305': 0.023 msec
total time taken: 7.446 msec
```
✓ Descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context✓ Mentions testing or verification
What changed, and why it matters
This commit adds self-tests to Electrum's cryptography code. When the program starts, it now runs a few known test vectors through hash and encryption functions and crashes immediately if the results are wrong. This is a defensive hardening change, not a fix for an active security flaw.
Recommended action
No immediate action required. Treat as routine hardening. Review whether assert-based failures are surfaced clearly to users in release builds.
Security signals we found
01
defensive runtime self-tests for cryptographic primitives
02
fail-fast assertions on hash and cipher backends
03
no change to protocol logic, parsing, or wallet handling
Evidence from the diff
The patch appends runtime sanity checks to electrum/crypto.py. It uses Python assert statements to verify that sha256, sha512, ripemd, AES-128, AES-256, chacha20, and chacha20-poly1305 produce expected outputs for fixed test inputs. The checks run at module import time and are designed to fail fast if a backend is broken or miswired. No existing behavior is changed and no vulnerability is patched.
Changed components
electrum/crypto.pyInspect captured patch +61 / −0
### electrum/crypto.py
@@ -504,3 +504,64 @@ def get_ecdh(priv: bytes, pub: bytes) -> bytes:
def privkey_to_pubkey(priv: bytes) -> bytes:
return ecc.ECPrivkey(priv[:32]).get_public_key_bytes()
+
+
+########################################
+# Run-time sanity checks.
+# - If one of the important cryptographic primitives is broken, we better panic.
+# - For several primitives we support multiple backends. By now at runtime,
+# we have already selected the backend: check if it really works and fail early if not.
+# - This whole section takes 5-10 msec.
+#
+# Hash functions. SHA2. single backend: hashlib
+assert sha256(b"satoshi_nakamoto").hex() == "5f94a8490efe9e06c590dd34e37b5ab8f482f1af7578c6a41542761938a42426"
+assert hashlib.sha512(b"satoshi_nakamoto").digest().hex() \
+ == "cae681a7f07bd26128f8536c59a38f10c9e648898426cd1dd94144c7d3ea0512186400edc5d38ac677d43e97ebb877bf76d69c44de1f6e074435adc79caf8f14"
+# Hash functions. ripemd. two supported backends: hashlib, ripemd.py
+assert ripemd(b"satoshi_nakamoto").hex() == "a9a1c16007c20fa031f97f712c5eabd6f2ec54c4"
+# AES-128: three supported backends: pycryptodomex, cryptography, pyaes
+assert aes_encrypt_with_iv(
+ key=b"satoshi_nakamoto",
+ iv=b"thetimes20090103",
+ data=b"The quick brown fox jumps over the lazy dog").hex() \
+ == "9128466a087892f5f945ca48fe8c4b1d34e126d19fb0c50ce7f127a19508146734152f38d65377cd0add2599042a55e2"
+assert aes_decrypt_with_iv(
+ key=b"satoshi_nakamoto",
+ iv=b"thetimes20090103",
+ data=bytes.fromhex("9128466a087892f5f945ca48fe8c4b1d34e126d19fb0c50ce7f127a19508146734152f38d65377cd0add2599042a55e2")) \
+ == b"The quick brown fox jumps over the lazy dog"
+# AES-256: three supported backends: pycryptodomex, cryptography, pyaes
+assert aes_encrypt_with_iv(
+ key=b"satoshi_nakamoto_wanted_32_bytes",
+ iv=b"thetimes20090103",
+ data=b"The quick brown fox jumps over the lazy dog").hex() \
+ == "65e532e8fb643e192d66cfebd3328ea6d52c9d43b18c8c8c7754b6a7c5927b7395201ff221315b51bfb1ad1c6184afce"
+assert aes_decrypt_with_iv(
+ key=b"satoshi_nakamoto_wanted_32_bytes",
+ iv=b"thetimes20090103",
+ data=bytes.fromhex("65e532e8fb643e192d66cfebd3328ea6d52c9d43b18c8c8c7754b6a7c5927b7395201ff221315b51bfb1ad1c6184afce")) \
+ == b"The quick brown fox jumps over the lazy dog"
+# chacha20: two supported backends: pycryptodomex, cryptography
+assert chacha20_encrypt(
+ key=b"satoshi_nakamoto_wanted_32_bytes",
+ nonce=b"thetimes2009",
+ data=b"The quick brown fox jumps over the lazy dog").hex() \
+ == "b34faa354952d09a5c052e490678866f0d1ad37e567b2ea9247438c0d91f5a00343dc8a681a60bb4b2973b"
+assert chacha20_decrypt(
+ key=b"satoshi_nakamoto_wanted_32_bytes",
+ nonce=b"thetimes2009",
+ data=bytes.fromhex("b34faa354952d09a5c052e490678866f0d1ad37e567b2ea9247438c0d91f5a00343dc8a681a60bb4b2973b")) \
+ == b"The quick brown fox jumps over the lazy dog"
+# chacha20-poly1305: two supported backends: pycryptodomex, cryptography
+assert chacha20_poly1305_encrypt(
+ key=b"satoshi_nakamoto_wanted_32_bytes",
+ nonce=b"thetimes2009",
+ associated_data=b"loremipsum",
+ data=b"The quick brown fox jumps over the lazy dog").hex() \
+ == "10861cab9d587356da776c6bca2320f39f6f0a5111a74929108ba27fda87e8777dcf6416a4ca9d443dba94b9891e48a1618a7347ac648970a38265"
+assert chacha20_poly1305_decrypt(
+ key=b"satoshi_nakamoto_wanted_32_bytes",
+ nonce=b"thetimes2009",
+ associated_data=b"loremipsum",
+ data=bytes.fromhex("10861cab9d587356da776c6bca2320f39f6f0a5111a74929108ba27fda87e8777dcf6416a4ca9d443dba94b9891e48a1618a7347ac648970a38265")) \
+ == b"The quick brown fox jumps over the lazy dog"Risk score
Our methodology →Why this scored 15/100
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