diff options
author | Jonas Nick <jonasd.nick@gmail.com> | 2019-11-04 12:53:37 +0000 |
---|---|---|
committer | Pieter Wuille <pieter.wuille@gmail.com> | 2020-01-19 14:47:33 -0800 |
commit | c8281deec64dcd06b49efd278c322f13f7b13de7 (patch) | |
tree | 2bdfcd620932b0a8037db7b1f5bbdb02522db826 /bip-schnorr | |
parent | 9b5ba158c1ee8fc87b6c21de8af58754a7ea3069 (diff) |
Fix point_from_bytes accepting out-of-range pubkeys and add test vector
Diffstat (limited to 'bip-schnorr')
-rw-r--r-- | bip-schnorr/reference.py | 2 | ||||
-rw-r--r-- | bip-schnorr/test-vectors.py | 26 |
2 files changed, 27 insertions, 1 deletions
diff --git a/bip-schnorr/reference.py b/bip-schnorr/reference.py index 79be690..f2a944f 100644 --- a/bip-schnorr/reference.py +++ b/bip-schnorr/reference.py @@ -53,6 +53,8 @@ def bytes_from_point(P): def point_from_bytes(b): x = int_from_bytes(b) + if x >= p: + return None y_sq = (pow(x, 3, p) + 7) % p y = pow(y_sq, (p + 1) // 4, p) if pow(y, 2, p) != y_sq: diff --git a/bip-schnorr/test-vectors.py b/bip-schnorr/test-vectors.py index da7aec6..195b61b 100644 --- a/bip-schnorr/test-vectors.py +++ b/bip-schnorr/test-vectors.py @@ -69,12 +69,14 @@ def vector4(): default_seckey = bytes_from_int(0xB7E151628AED2A6ABF7158809CF4F3C762E7160F38B4DA56A784D9045190CFEF) default_msg = bytes_from_int(0x243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89) +# Public key is not on the curve def vector5(): + # This creates a dummy signature that doesn't have anything to do with the + # public key. seckey = default_seckey msg = default_msg sig = schnorr_sign(msg, seckey) - # Public key is not on the curve pubkey = bytes_from_int(0xEEFDEA4CDB677750A420FEE807EACF21EB9898AE79B9768766E4FAA04A2D4A34) assert(point_from_bytes(pubkey) is None) @@ -185,6 +187,27 @@ def vector13(): return (None, pubkey_gen(seckey), msg, sig, "FALSE", "sig[32:64] is equal to curve order") +# Test out of range pubkey +# It's cryptographically impossible to create a test vector that fails if run +# in an implementation which accepts out of range pubkeys because we can't find +# a secret key for such a public key and therefore can not create a signature. +# This test vector just increases test coverage. +def vector14(): + # This creates a dummy signature that doesn't have anything to do with the + # public key. + seckey = default_seckey + msg = default_msg + sig = schnorr_sign(msg, seckey) + + pubkey_int = p + 1 + pubkey = bytes_from_int(pubkey_int) + assert(point_from_bytes(pubkey) is None) + # If an implementation would reduce a given public key modulo p then the + # pubkey would be valid + assert(point_from_bytes(bytes_from_int(pubkey_int % p)) is not None) + + return (None, pubkey, msg, sig, "FALSE", "public key is not a valid X coordinate because it exceeds the field size") + vectors = [ vector0(), vector1(), @@ -200,6 +223,7 @@ vectors = [ vector11(), vector12(), vector13(), + vector14() ] # Converts the byte strings of a test vector into hex strings |