1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390
//! Re-exporting Ed25519 implementations, and related utilities.
//!
//! Here we re-export types from [`ed25519_dalek`] that implement the
//! Ed25519 signature algorithm. (TODO: Eventually, this module
//! should probably be replaced with a wrapper that uses the ed25519
//! trait and the Signature trait.)
//!
//! We additionally provide an `Ed25519Identity` type to represent the
//! unvalidated Ed25519 "identity keys" that we use throughout the Tor
//! protocol to uniquely identify a relay.
use base64ct::{Base64Unpadded, Encoding as _};
use curve25519_dalek::Scalar;
use sha2::Sha512;
use std::fmt::{self, Debug, Display, Formatter};
use subtle::{Choice, ConstantTimeEq};
use ed25519_dalek::hazmat::ExpandedSecretKey;
// NOTE: We are renaming a few types here to maintain consistency with
// our variable names, and with the nomenclature we use elsewhere for public
// keys.
pub use ed25519_dalek::{
Signature, Signer, SigningKey as Keypair, Verifier, VerifyingKey as PublicKey,
};
use crate::util::ct::CtByteArray;
/// The length of an ED25519 identity, in bytes.
pub const ED25519_ID_LEN: usize = 32;
/// The length of an ED25519 signature, in bytes.
pub const ED25519_SIGNATURE_LEN: usize = 64;
/// A variant of [`Keypair`] containing an [`ExpandedSecretKey`].
///
/// In the Tor protocol, we use this type for blinded onion service identity keys
/// (KS_hs_blind_id). Since their scalar values are computed, rather than taken
/// directly from a
/// SHA-512 transformation of a SecretKey, we cannot use the regular `Keypair`
/// type.
#[allow(clippy::exhaustive_structs)]
pub struct ExpandedKeypair {
/// The secret part of the key.
pub(crate) secret: ExpandedSecretKey,
/// The public part of this key.
///
/// NOTE: As with [`ed25519_dalek::SigningKey`], this public key _must_ be
/// the public key matching `secret`. Putting a different public key in
/// here would enable a class of attacks against ed25519 and enable secret
/// key recovery.
pub(crate) public: PublicKey,
}
impl ExpandedKeypair {
/// Return the public part of this expanded keypair.
pub fn public(&self) -> &PublicKey {
&self.public
}
// NOTE: There is deliberately no secret() function. If we had one, we
// would be exposing an unescorted secret key, which is part of
// ed25519::hazmat.
/// Compute a signature over a message using this keypair.
pub fn sign(&self, message: &[u8]) -> Signature {
// See notes on ExpandedKeypair about why this hazmat is okay to use.
ed25519_dalek::hazmat::raw_sign::<Sha512>(&self.secret, message, &self.public)
}
/// Return a representation of the secret key in this keypair.
///
/// (Since it is an expanded secret key, we represent it as its scalar part
/// followed by its hash_prefix.)
pub fn to_secret_key_bytes(&self) -> [u8; 64] {
let mut output = [0_u8; 64];
output[0..32].copy_from_slice(&self.secret.scalar.to_bytes());
output[32..64].copy_from_slice(&self.secret.hash_prefix);
output
}
/// Reconstruct a key from its byte representation as returned by
/// `to_secret_key_bytes()`.
///
/// Return None if the input cannot be the output of `to_secret_key_bytes()`.
//
// NOTE: Returning None is a bit silly, but that's what Dalek does.
pub fn from_secret_key_bytes(bytes: [u8; 64]) -> Option<Self> {
let scalar = Option::from(Scalar::from_bytes_mod_order(
bytes[0..32].try_into().expect("wrong length on slice"),
))?;
let hash_prefix = bytes[32..64].try_into().expect("wrong length on slice");
let secret = ExpandedSecretKey {
scalar,
hash_prefix,
};
let public = PublicKey::from(&secret);
Some(Self { secret, public })
}
// NOTE: There is deliberately no constructor here that takes a (secret,
// public) pair. If there were, you could construct a pair with a
// mismatched public key.
}
impl<'a> From<&'a Keypair> for ExpandedKeypair {
fn from(kp: &'a Keypair) -> ExpandedKeypair {
ExpandedKeypair {
secret: kp.as_bytes().into(),
public: kp.into(),
}
}
}
/// An unchecked, unvalidated Ed25519 key.
///
/// This key is an "identity" in the sense that it identifies (up to) one
/// Ed25519 key. It may also represent the identity for a particular entity,
/// such as a relay or an onion service.
///
/// This type is distinct from an Ed25519 [`PublicKey`] for several reasons:
/// * We're storing it in a compact format, whereas the public key
/// implementation might want an expanded form for more efficient key
/// validation.
/// * This type hasn't checked whether the bytes here actually _are_ a valid
/// Ed25519 public key.
#[derive(Clone, Copy, Hash, PartialOrd, Ord, Eq, PartialEq)]
pub struct Ed25519Identity {
/// A raw unchecked Ed25519 public key.
id: CtByteArray<ED25519_ID_LEN>,
}
impl Ed25519Identity {
/// Construct a new Ed25519 identity from a 32-byte sequence.
///
/// This might or might not actually be a valid Ed25519 public key.
///
/// ```
/// use tor_llcrypto::pk::ed25519::{Ed25519Identity, PublicKey};
///
/// let bytes = b"klsadjfkladsfjklsdafkljasdfsdsd!";
/// let id = Ed25519Identity::new(*bytes);
/// let pk: Result<PublicKey,_> = (&id).try_into();
/// assert!(pk.is_ok());
///
/// let bytes = b"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
/// let id = Ed25519Identity::new(*bytes);
/// let pk: Result<PublicKey,_> = (&id).try_into();
/// assert!(pk.is_err());
/// ```
pub fn new(id: [u8; 32]) -> Self {
Ed25519Identity { id: id.into() }
}
/// If `id` is of the correct length, wrap it in an Ed25519Identity.
pub fn from_bytes(id: &[u8]) -> Option<Self> {
Some(Ed25519Identity::new(id.try_into().ok()?))
}
/// Return a reference to the bytes in this key.
pub fn as_bytes(&self) -> &[u8] {
&self.id.as_ref()[..]
}
}
impl From<[u8; ED25519_ID_LEN]> for Ed25519Identity {
fn from(id: [u8; ED25519_ID_LEN]) -> Self {
Ed25519Identity::new(id)
}
}
impl From<Ed25519Identity> for [u8; ED25519_ID_LEN] {
fn from(value: Ed25519Identity) -> Self {
value.id.into()
}
}
impl From<PublicKey> for Ed25519Identity {
fn from(pk: PublicKey) -> Self {
(&pk).into()
}
}
impl From<&PublicKey> for Ed25519Identity {
fn from(pk: &PublicKey) -> Self {
// This unwrap is safe because the public key is always 32 bytes
// long.
Ed25519Identity::from_bytes(pk.as_bytes()).expect("Ed25519 public key had wrong length?")
}
}
impl TryFrom<&Ed25519Identity> for PublicKey {
type Error = ed25519_dalek::SignatureError;
fn try_from(id: &Ed25519Identity) -> Result<PublicKey, Self::Error> {
PublicKey::from_bytes(id.id.as_ref())
}
}
impl TryFrom<Ed25519Identity> for PublicKey {
type Error = ed25519_dalek::SignatureError;
fn try_from(id: Ed25519Identity) -> Result<PublicKey, Self::Error> {
(&id).try_into()
}
}
impl ConstantTimeEq for Ed25519Identity {
fn ct_eq(&self, other: &Self) -> Choice {
self.id.ct_eq(&other.id)
}
}
impl Display for Ed25519Identity {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
write!(f, "{}", Base64Unpadded::encode_string(self.id.as_ref()))
}
}
impl Debug for Ed25519Identity {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
write!(f, "Ed25519Identity {{ {} }}", self)
}
}
impl safelog::Redactable for Ed25519Identity {
/// Warning: This displays 12 bits of the ed25519 identity, which is
/// enough to narrow down a public relay by a great deal.
fn display_redacted(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(
f,
"{}…",
&Base64Unpadded::encode_string(self.id.as_ref())[..2]
)
}
fn debug_redacted(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "Ed25519Identity {{ {} }}", self.redacted())
}
}
impl serde::Serialize for Ed25519Identity {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
if serializer.is_human_readable() {
serializer.serialize_str(&Base64Unpadded::encode_string(self.id.as_ref()))
} else {
serializer.serialize_bytes(&self.id.as_ref()[..])
}
}
}
impl<'de> serde::Deserialize<'de> for Ed25519Identity {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
if deserializer.is_human_readable() {
/// Helper for deserialization
struct EdIdentityVisitor;
impl<'de> serde::de::Visitor<'de> for EdIdentityVisitor {
type Value = Ed25519Identity;
fn expecting(&self, fmt: &mut std::fmt::Formatter<'_>) -> fmt::Result {
fmt.write_str("base64-encoded Ed25519 public key")
}
fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
let bytes = Base64Unpadded::decode_vec(s).map_err(E::custom)?;
Ed25519Identity::from_bytes(&bytes)
.ok_or_else(|| E::custom("wrong length for Ed25519 public key"))
}
}
deserializer.deserialize_str(EdIdentityVisitor)
} else {
/// Helper for deserialization
struct EdIdentityVisitor;
impl<'de> serde::de::Visitor<'de> for EdIdentityVisitor {
type Value = Ed25519Identity;
fn expecting(&self, fmt: &mut std::fmt::Formatter<'_>) -> fmt::Result {
fmt.write_str("ed25519 public key")
}
fn visit_bytes<E>(self, bytes: &[u8]) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ed25519Identity::from_bytes(bytes)
.ok_or_else(|| E::custom("wrong length for ed25519 public key"))
}
}
deserializer.deserialize_bytes(EdIdentityVisitor)
}
}
}
/// An ed25519 signature, plus the document that it signs and its
/// public key.
#[derive(Clone, Debug)]
pub struct ValidatableEd25519Signature {
/// The key that allegedly produced the signature
key: PublicKey,
/// The alleged signature
sig: Signature,
/// The entire body of text that is allegedly signed here.
///
/// TODO: It's not so good to have this included here; it
/// would be better to have a patch to ed25519_dalek to allow
/// us to pre-hash the signed thing, and just store a digest.
/// We can't use that with the 'prehash' variant of ed25519,
/// since that has different constants.
entire_text_of_signed_thing: Vec<u8>,
}
impl ValidatableEd25519Signature {
/// Create a new ValidatableEd25519Signature
pub fn new(key: PublicKey, sig: Signature, text: &[u8]) -> Self {
ValidatableEd25519Signature {
key,
sig,
entire_text_of_signed_thing: text.into(),
}
}
/// View the interior of this signature object.
pub(crate) fn as_parts(&self) -> (&PublicKey, &Signature, &[u8]) {
(&self.key, &self.sig, &self.entire_text_of_signed_thing[..])
}
/// Return a reference to the underlying Signature.
pub fn signature(&self) -> &Signature {
&self.sig
}
}
impl super::ValidatableSignature for ValidatableEd25519Signature {
fn is_valid(&self) -> bool {
self.key
.verify(&self.entire_text_of_signed_thing[..], &self.sig)
.is_ok()
}
fn as_ed25519(&self) -> Option<&ValidatableEd25519Signature> {
Some(self)
}
}
/// Perform a batch verification operation on the provided signatures
///
/// Return `true` if _every_ signature is valid; otherwise return `false`.
///
/// Note that the mathematics for batch validation are slightly
/// different than those for normal one-signature validation. Because
/// of this, it is possible for an ostensible signature that passes
/// one validation algorithm might fail the other. (Well-formed
/// signatures generated by a correct Ed25519 implementation will
/// always pass both kinds of validation, and an attacker should not
/// be able to forge a signature that passes either kind.)
pub fn validate_batch(sigs: &[&ValidatableEd25519Signature]) -> bool {
use crate::pk::ValidatableSignature;
if sigs.is_empty() {
// ed25519_dalek has nonzero cost for a batch-verification of
// zero sigs.
true
} else if sigs.len() == 1 {
// Validating one signature in the traditional way is faster.
sigs[0].is_valid()
} else {
let mut ed_msgs = Vec::new();
let mut ed_sigs = Vec::new();
let mut ed_pks = Vec::new();
for ed_sig in sigs {
let (pk, sig, msg) = ed_sig.as_parts();
ed_sigs.push(*sig);
ed_pks.push(*pk);
ed_msgs.push(msg);
}
ed25519_dalek::verify_batch(&ed_msgs[..], &ed_sigs[..], &ed_pks[..]).is_ok()
}
}
/// An object that has an Ed25519 [`PublicKey`].
pub trait Ed25519PublicKey {
/// Get the Ed25519 [`PublicKey`].
fn public_key(&self) -> &PublicKey;
}
impl Ed25519PublicKey for Keypair {
fn public_key(&self) -> &PublicKey {
self.as_ref()
}
}