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fix: return false rather than panicking on invalid ECDSA signatures
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@TomAFrench
TomAFrench committed Sep 20, 2023
1 parent 2f503c4 commit 043451f
Showing 1 changed file with 173 additions and 62 deletions.
235 changes: 173 additions & 62 deletions blackbox_solver/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -117,15 +117,27 @@ fn verify_secp256k1_ecdsa_signature(
};
// Convert the inputs into k256 data structures

let signature = Signature::try_from(signature.as_slice()).unwrap();
let Ok(signature) = Signature::try_from(signature.as_slice()) else {
// Signature `r` and `s` are forbidden from being zero.
return false;
};

let point = EncodedPoint::from_affine_coordinates(
public_key_x_bytes.into(),
public_key_y_bytes.into(),
true,
);
let pubkey = PublicKey::from_encoded_point(&point).unwrap();

let pubkey = PublicKey::from_encoded_point(&point);
let pubkey = if pubkey.is_some().into() {
pubkey.unwrap()
} else {
// Public key must lie on the Secp256k1 curve.
return false;
};

// Note: This is incorrect as it will panic if `hashed_msg >= k256::Secp256k1::ORDER`.
// In this scenario we should just take the leftmost bits from `hashed_msg` up to the group order length.
let z = Scalar::from_repr(*GenericArray::from_slice(hashed_msg)).unwrap();

// Finished converting bytes into data structures
Expand Down Expand Up @@ -173,15 +185,27 @@ fn verify_secp256r1_ecdsa_signature(

// Convert the inputs into k256 data structures

let signature = Signature::try_from(signature.as_slice()).unwrap();
let Ok(signature) = Signature::try_from(signature.as_slice()) else {
// Signature `r` and `s` are forbidden from being zero.
return false;
};

let point = EncodedPoint::from_affine_coordinates(
public_key_x_bytes.into(),
public_key_y_bytes.into(),
true,
);
let pubkey = PublicKey::from_encoded_point(&point).unwrap();

let pubkey = PublicKey::from_encoded_point(&point);
let pubkey = if pubkey.is_some().into() {
pubkey.unwrap()
} else {
// Public key must lie on the Secp256r1 curve.
return false;
};

// Note: This is incorrect as it will panic if `hashed_msg >= p256::NistP256::ORDER`.
// In this scenario we should just take the leftmost bits from `hashed_msg` up to the group order length.
let z = Scalar::from_repr(*GenericArray::from_slice(hashed_msg)).unwrap();

// Finished converting bytes into data structures
Expand Down Expand Up @@ -210,75 +234,162 @@ fn verify_secp256r1_ecdsa_signature(
}

#[cfg(test)]
mod test {
use super::{verify_secp256k1_ecdsa_signature, verify_secp256r1_ecdsa_signature};
mod secp256k1_tests {
use super::verify_secp256k1_ecdsa_signature;

// 0x3a73f4123a5cd2121f21cd7e8d358835476949d035d9c2da6806b4633ac8c1e2,
const HASHED_MESSAGE: [u8; 32] = [
0x3a, 0x73, 0xf4, 0x12, 0x3a, 0x5c, 0xd2, 0x12, 0x1f, 0x21, 0xcd, 0x7e, 0x8d, 0x35, 0x88,
0x35, 0x47, 0x69, 0x49, 0xd0, 0x35, 0xd9, 0xc2, 0xda, 0x68, 0x06, 0xb4, 0x63, 0x3a, 0xc8,
0xc1, 0xe2,
];
// 0xa0434d9e47f3c86235477c7b1ae6ae5d3442d49b1943c2b752a68e2a47e247c7
const PUB_KEY_X: [u8; 32] = [
0xa0, 0x43, 0x4d, 0x9e, 0x47, 0xf3, 0xc8, 0x62, 0x35, 0x47, 0x7c, 0x7b, 0x1a, 0xe6, 0xae,
0x5d, 0x34, 0x42, 0xd4, 0x9b, 0x19, 0x43, 0xc2, 0xb7, 0x52, 0xa6, 0x8e, 0x2a, 0x47, 0xe2,
0x47, 0xc7,
];
// 0x893aba425419bc27a3b6c7e693a24c696f794c2ed877a1593cbee53b037368d7
const PUB_KEY_Y: [u8; 32] = [
0x89, 0x3a, 0xba, 0x42, 0x54, 0x19, 0xbc, 0x27, 0xa3, 0xb6, 0xc7, 0xe6, 0x93, 0xa2, 0x4c,
0x69, 0x6f, 0x79, 0x4c, 0x2e, 0xd8, 0x77, 0xa1, 0x59, 0x3c, 0xbe, 0xe5, 0x3b, 0x03, 0x73,
0x68, 0xd7,
];
// 0xe5081c80ab427dc370346f4a0e31aa2bad8d9798c38061db9ae55a4e8df454fd28119894344e71b78770cc931d61f480ecbb0b89d6eb69690161e49a715fcd55
const SIGNATURE: [u8; 64] = [
0xe5, 0x08, 0x1c, 0x80, 0xab, 0x42, 0x7d, 0xc3, 0x70, 0x34, 0x6f, 0x4a, 0x0e, 0x31, 0xaa,
0x2b, 0xad, 0x8d, 0x97, 0x98, 0xc3, 0x80, 0x61, 0xdb, 0x9a, 0xe5, 0x5a, 0x4e, 0x8d, 0xf4,
0x54, 0xfd, 0x28, 0x11, 0x98, 0x94, 0x34, 0x4e, 0x71, 0xb7, 0x87, 0x70, 0xcc, 0x93, 0x1d,
0x61, 0xf4, 0x80, 0xec, 0xbb, 0x0b, 0x89, 0xd6, 0xeb, 0x69, 0x69, 0x01, 0x61, 0xe4, 0x9a,
0x71, 0x5f, 0xcd, 0x55,
];

#[test]
fn verifies_valid_k1_signature_with_low_s_value() {
// 0x3a73f4123a5cd2121f21cd7e8d358835476949d035d9c2da6806b4633ac8c1e2,
let hashed_message: [u8; 32] = [
0x3a, 0x73, 0xf4, 0x12, 0x3a, 0x5c, 0xd2, 0x12, 0x1f, 0x21, 0xcd, 0x7e, 0x8d, 0x35,
0x88, 0x35, 0x47, 0x69, 0x49, 0xd0, 0x35, 0xd9, 0xc2, 0xda, 0x68, 0x06, 0xb4, 0x63,
0x3a, 0xc8, 0xc1, 0xe2,
];

// 0xa0434d9e47f3c86235477c7b1ae6ae5d3442d49b1943c2b752a68e2a47e247c7
let pub_key_x: [u8; 32] = [
0xa0, 0x43, 0x4d, 0x9e, 0x47, 0xf3, 0xc8, 0x62, 0x35, 0x47, 0x7c, 0x7b, 0x1a, 0xe6,
0xae, 0x5d, 0x34, 0x42, 0xd4, 0x9b, 0x19, 0x43, 0xc2, 0xb7, 0x52, 0xa6, 0x8e, 0x2a,
0x47, 0xe2, 0x47, 0xc7,
];

// 0x893aba425419bc27a3b6c7e693a24c696f794c2ed877a1593cbee53b037368d7
let pub_key_y: [u8; 32] = [
0x89, 0x3a, 0xba, 0x42, 0x54, 0x19, 0xbc, 0x27, 0xa3, 0xb6, 0xc7, 0xe6, 0x93, 0xa2,
0x4c, 0x69, 0x6f, 0x79, 0x4c, 0x2e, 0xd8, 0x77, 0xa1, 0x59, 0x3c, 0xbe, 0xe5, 0x3b,
0x03, 0x73, 0x68, 0xd7,
];

// 0xe5081c80ab427dc370346f4a0e31aa2bad8d9798c38061db9ae55a4e8df454fd28119894344e71b78770cc931d61f480ecbb0b89d6eb69690161e49a715fcd55
let signature: [u8; 64] = [
0xe5, 0x08, 0x1c, 0x80, 0xab, 0x42, 0x7d, 0xc3, 0x70, 0x34, 0x6f, 0x4a, 0x0e, 0x31,
0xaa, 0x2b, 0xad, 0x8d, 0x97, 0x98, 0xc3, 0x80, 0x61, 0xdb, 0x9a, 0xe5, 0x5a, 0x4e,
0x8d, 0xf4, 0x54, 0xfd, 0x28, 0x11, 0x98, 0x94, 0x34, 0x4e, 0x71, 0xb7, 0x87, 0x70,
0xcc, 0x93, 0x1d, 0x61, 0xf4, 0x80, 0xec, 0xbb, 0x0b, 0x89, 0xd6, 0xeb, 0x69, 0x69,
0x01, 0x61, 0xe4, 0x9a, 0x71, 0x5f, 0xcd, 0x55,
];
fn verifies_valid_signature_with_low_s_value() {
let valid =
verify_secp256k1_ecdsa_signature(&HASHED_MESSAGE, &PUB_KEY_X, &PUB_KEY_Y, &SIGNATURE);

assert!(valid)
}

#[test]
fn rejects_invalid_signature() {
// This signature is invalid as ECDSA specifies that `r` and `s` must be non-zero.
let invalid_signature: [u8; 64] = [0x00; 64];

let valid = verify_secp256k1_ecdsa_signature(
&HASHED_MESSAGE,
&PUB_KEY_X,
&PUB_KEY_Y,
&invalid_signature,
);
assert!(!valid);
}

#[test]
fn rejects_invalid_public_key() {
let invalid_pub_key_x: [u8; 32] = [0xff; 32];
let invalid_pub_key_y: [u8; 32] = [0xff; 32];

let valid = verify_secp256k1_ecdsa_signature(
&HASHED_MESSAGE,
&invalid_pub_key_x,
&invalid_pub_key_y,
&SIGNATURE,
);

assert!(!valid)
}

#[test]
#[ignore = "ECDSA verification does not currently handle long hashes correctly"]
fn trims_overly_long_hashes_to_correct_length() {
let mut long_hashed_message = HASHED_MESSAGE.to_vec();
long_hashed_message.push(0xff);

let valid = verify_secp256k1_ecdsa_signature(
&long_hashed_message,
&PUB_KEY_X,
&PUB_KEY_Y,
&SIGNATURE,
);

assert!(valid)
}
}

#[cfg(test)]
mod secp256r1_tests {
use super::verify_secp256r1_ecdsa_signature;

// 0x54705ba3baafdbdfba8c5f9a70f7a89bee98d906b53e31074da7baecdc0da9ad
const HASHED_MESSAGE: [u8; 32] = [
84, 112, 91, 163, 186, 175, 219, 223, 186, 140, 95, 154, 112, 247, 168, 155, 238, 152, 217,
6, 181, 62, 49, 7, 77, 167, 186, 236, 220, 13, 169, 173,
];
// 0x550f471003f3df97c3df506ac797f6721fb1a1fb7b8f6f83d224498a65c88e24
const PUB_KEY_X: [u8; 32] = [
85, 15, 71, 16, 3, 243, 223, 151, 195, 223, 80, 106, 199, 151, 246, 114, 31, 177, 161, 251,
123, 143, 111, 131, 210, 36, 73, 138, 101, 200, 142, 36,
];
// 0x136093d7012e509a73715cbd0b00a3cc0ff4b5c01b3ffa196ab1fb327036b8e6
const PUB_KEY_Y: [u8; 32] = [
19, 96, 147, 215, 1, 46, 80, 154, 115, 113, 92, 189, 11, 0, 163, 204, 15, 244, 181, 192,
27, 63, 250, 25, 106, 177, 251, 50, 112, 54, 184, 230,
];
// 0x2c70a8d084b62bfc5ce03641caf9f72ad4da8c81bfe6ec9487bb5e1bef62a13218ad9ee29eaf351fdc50f1520c425e9b908a07278b43b0ec7b872778c14e0784
const SIGNATURE: [u8; 64] = [
44, 112, 168, 208, 132, 182, 43, 252, 92, 224, 54, 65, 202, 249, 247, 42, 212, 218, 140,
129, 191, 230, 236, 148, 135, 187, 94, 27, 239, 98, 161, 50, 24, 173, 158, 226, 158, 175,
53, 31, 220, 80, 241, 82, 12, 66, 94, 155, 144, 138, 7, 39, 139, 67, 176, 236, 123, 135,
39, 120, 193, 78, 7, 132,
];

#[test]
fn verifies_valid_signature_with_low_s_value() {
let valid =
verify_secp256k1_ecdsa_signature(&hashed_message, &pub_key_x, &pub_key_y, &signature);
verify_secp256r1_ecdsa_signature(&HASHED_MESSAGE, &PUB_KEY_X, &PUB_KEY_Y, &SIGNATURE);

assert!(valid)
}

#[test]
fn verifies_valid_r1_signature_with_low_s_value() {
// 0x54705ba3baafdbdfba8c5f9a70f7a89bee98d906b53e31074da7baecdc0da9ad
let hashed_message = [
84, 112, 91, 163, 186, 175, 219, 223, 186, 140, 95, 154, 112, 247, 168, 155, 238, 152,
217, 6, 181, 62, 49, 7, 77, 167, 186, 236, 220, 13, 169, 173,
];
// 0x550f471003f3df97c3df506ac797f6721fb1a1fb7b8f6f83d224498a65c88e24
let pub_key_x = [
85, 15, 71, 16, 3, 243, 223, 151, 195, 223, 80, 106, 199, 151, 246, 114, 31, 177, 161,
251, 123, 143, 111, 131, 210, 36, 73, 138, 101, 200, 142, 36,
];
// 0x136093d7012e509a73715cbd0b00a3cc0ff4b5c01b3ffa196ab1fb327036b8e6
let pub_key_y = [
19, 96, 147, 215, 1, 46, 80, 154, 115, 113, 92, 189, 11, 0, 163, 204, 15, 244, 181,
192, 27, 63, 250, 25, 106, 177, 251, 50, 112, 54, 184, 230,
];

// 0x2c70a8d084b62bfc5ce03641caf9f72ad4da8c81bfe6ec9487bb5e1bef62a13218ad9ee29eaf351fdc50f1520c425e9b908a07278b43b0ec7b872778c14e0784
let signature: [u8; 64] = [
44, 112, 168, 208, 132, 182, 43, 252, 92, 224, 54, 65, 202, 249, 247, 42, 212, 218,
140, 129, 191, 230, 236, 148, 135, 187, 94, 27, 239, 98, 161, 50, 24, 173, 158, 226,
158, 175, 53, 31, 220, 80, 241, 82, 12, 66, 94, 155, 144, 138, 7, 39, 139, 67, 176,
236, 123, 135, 39, 120, 193, 78, 7, 132,
];
fn rejects_invalid_signature() {
// This signature is invalid as ECDSA specifies that `r` and `s` must be non-zero.
let invalid_signature: [u8; 64] = [0x00; 64];

let valid = verify_secp256r1_ecdsa_signature(
&HASHED_MESSAGE,
&PUB_KEY_X,
&PUB_KEY_Y,
&invalid_signature,
);
assert!(!valid);
}

#[test]
fn rejects_invalid_public_key() {
let invalid_pub_key_x: [u8; 32] = [0xff; 32];
let invalid_pub_key_y: [u8; 32] = [0xff; 32];

let valid = verify_secp256r1_ecdsa_signature(
&HASHED_MESSAGE,
&invalid_pub_key_x,
&invalid_pub_key_y,
&SIGNATURE,
);

assert!(!valid)
}

#[test]
#[ignore = "ECDSA verification does not currently handle long hashes correctly"]
fn trims_overly_long_hashes_to_correct_length() {
let mut long_hashed_message = HASHED_MESSAGE.to_vec();
long_hashed_message.push(0xff);

let valid =
verify_secp256r1_ecdsa_signature(&hashed_message, &pub_key_x, &pub_key_y, &signature);
verify_secp256r1_ecdsa_signature(&HASHED_MESSAGE, &PUB_KEY_X, &PUB_KEY_Y, &SIGNATURE);

assert!(valid)
}
Expand Down

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