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/* Copyright (c) 2023, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
use crate::CSlice;
/// The length in bytes of an Ed25519 public key.
pub const PUBLIC_KEY_LENGTH: usize = bssl_sys::ED25519_PUBLIC_KEY_LEN as usize;
/// The length in bytes of an Ed25519 seed which is the 32-byte private key representation defined
/// in RFC 8032.
pub const SEED_LENGTH: usize =
(bssl_sys::ED25519_PRIVATE_KEY_LEN - bssl_sys::ED25519_PUBLIC_KEY_LEN) as usize;
/// The length in bytes of an Ed25519 signature.
pub const SIGNATURE_LENGTH: usize = bssl_sys::ED25519_SIGNATURE_LEN as usize;
// The length in bytes of an Ed25519 keypair. In boringssl the private key is suffixed with the
// public key, so the keypair length is the same as the private key length.
const KEYPAIR_LENGTH: usize = bssl_sys::ED25519_PRIVATE_KEY_LEN as usize;
/// An Ed25519 private key.
pub struct PrivateKey([u8; KEYPAIR_LENGTH]);
/// An Ed25519 signature created by signing a message with a private key.
pub struct Signature([u8; SIGNATURE_LENGTH]);
/// An Ed25519 public key used to verify a signature + message.
pub struct PublicKey([u8; PUBLIC_KEY_LENGTH]);
/// Error returned if the verification on the signature + message fails.
#[derive(Debug)]
pub struct SignatureError;
impl PrivateKey {
/// Generates a new Ed25519 keypair.
pub fn generate() -> Self {
let mut public_key = [0u8; PUBLIC_KEY_LENGTH];
let mut private_key = [0u8; KEYPAIR_LENGTH];
// Safety:
// - Public key and private key are the correct length.
unsafe { bssl_sys::ED25519_keypair(public_key.as_mut_ptr(), private_key.as_mut_ptr()) }
PrivateKey(private_key)
}
/// Converts the key-pair to an array of bytes consisting of the bytes of the private key
/// followed by the bytes of the public key.
pub fn to_seed(&self) -> [u8; SEED_LENGTH] {
// This code will never panic because a length 32 slice will always fit into a
// size 32 byte array. The private key is the first 32 bytes of the keypair.
#[allow(clippy::expect_used)]
self.0[..SEED_LENGTH].try_into().expect(
"A slice of length SEED_LENGTH will always fit into an array of length SEED_LENGTH",
)
}
/// Builds this key-pair from `seed`, which is the 32-byte private key representation defined
/// in RFC 8032.
pub fn new_from_seed(seed: &[u8; SEED_LENGTH]) -> Self {
let mut public_key = [0u8; PUBLIC_KEY_LENGTH];
let mut private_key = [0u8; KEYPAIR_LENGTH];
// Safety:
// - Public key, private key, and seed are the correct lengths.
unsafe {
bssl_sys::ED25519_keypair_from_seed(
public_key.as_mut_ptr(),
private_key.as_mut_ptr(),
seed.as_ptr(),
)
}
PrivateKey(private_key)
}
/// Signs the given message and returns a digital signature.
pub fn sign(&self, msg: &[u8]) -> Signature {
let mut sig_bytes = [0u8; SIGNATURE_LENGTH];
// Safety:
// - On allocation failure we panic.
// - Signature and private keys are always the correct length.
let result = unsafe {
bssl_sys::ED25519_sign(
sig_bytes.as_mut_ptr(),
msg.as_ptr(),
msg.len(),
self.0.as_ptr(),
)
};
assert_eq!(result, 1, "allocation failure in bssl_sys::ED25519_sign");
Signature(sig_bytes)
}
/// Returns the PublicKey of the KeyPair.
pub fn public(&self) -> PublicKey {
let keypair_bytes = self.0;
// This code will never panic because a length 32 slice will always fit into a
// size 32 byte array. The public key is the last 32 bytes of the keypair.
#[allow(clippy::expect_used)]
PublicKey(
keypair_bytes[PUBLIC_KEY_LENGTH..]
.try_into()
.expect("The slice is always the correct size for a public key"),
)
}
}
impl PublicKey {
/// Builds the public key from an array of bytes.
pub fn from_bytes(bytes: [u8; PUBLIC_KEY_LENGTH]) -> Self {
PublicKey(bytes)
}
/// Returns the bytes of the public key.
pub fn to_bytes(&self) -> [u8; PUBLIC_KEY_LENGTH] {
self.0
}
/// Succeeds if the signature is a valid signature created by this keypair, otherwise returns an Error.
pub fn verify(&self, message: &[u8], signature: Signature) -> Result<(), SignatureError> {
let message_cslice = CSlice::from(message);
let ret = unsafe {
bssl_sys::ED25519_verify(
message_cslice.as_ptr(),
message_cslice.len(),
signature.0.as_ptr(),
self.0.as_ptr(),
)
};
if ret == 1 {
Ok(())
} else {
Err(SignatureError)
}
}
}
impl Signature {
/// Creates a signature from a byte array.
pub fn from_bytes(bytes: [u8; SIGNATURE_LENGTH]) -> Self {
Self(bytes)
}
/// Returns the bytes of the signature.
pub fn to_bytes(&self) -> [u8; SIGNATURE_LENGTH] {
self.0
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::test_helpers;
#[test]
fn ed25519_kp_gen_roundtrip() {
let private_key = PrivateKey::generate();
assert_ne!([0u8; 64], private_key.0);
let seed = private_key.to_seed();
let new_private_key = PrivateKey::new_from_seed(&seed);
assert_eq!(private_key.0, new_private_key.0);
}
#[test]
fn ed25519_empty_msg() {
// Test Case 1 from RFC test vectors: https://www.rfc-editor.org/rfc/rfc8032#section-7.1
let pk = test_helpers::decode_hex(
"d75a980182b10ab7d54bfed3c964073a0ee172f3daa62325af021a68f707511a",
);
let sk = test_helpers::decode_hex(
"9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60",
);
let msg = [0u8; 0];
let sig_expected = test_helpers::decode_hex("e5564300c360ac729086e2cc806e828a84877f1eb8e5d974d873e065224901555fb8821590a33bacc61e39701cf9b46bd25bf5f0595bbe24655141438e7a100b");
let kp = PrivateKey::new_from_seed(&sk);
let sig = kp.sign(&msg);
assert_eq!(sig_expected, sig.0);
let pub_key = PublicKey::from_bytes(pk);
assert_eq!(pub_key.to_bytes(), kp.public().to_bytes());
assert!(pub_key.verify(&msg, sig).is_ok());
}
#[test]
fn ed25519_sign_and_verify() {
// Test Case 15 from RFC test vectors: https://www.rfc-editor.org/rfc/rfc8032#section-7.1
let pk = test_helpers::decode_hex(
"cf3af898467a5b7a52d33d53bc037e2642a8da996903fc252217e9c033e2f291",
);
let sk = test_helpers::decode_hex(
"9acad959d216212d789a119252ebfe0c96512a23c73bd9f3b202292d6916a738",
);
let msg: [u8; 14] = test_helpers::decode_hex("55c7fa434f5ed8cdec2b7aeac173");
let sig_expected = test_helpers::decode_hex("6ee3fe81e23c60eb2312b2006b3b25e6838e02106623f844c44edb8dafd66ab0671087fd195df5b8f58a1d6e52af42908053d55c7321010092748795ef94cf06");
let kp = PrivateKey::new_from_seed(&sk);
let sig = kp.sign(&msg);
assert_eq!(sig_expected, sig.0);
let pub_key = PublicKey::from_bytes(pk);
assert_eq!(pub_key.to_bytes(), kp.public().to_bytes());
assert!(pub_key.verify(&msg, sig).is_ok());
}
}