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curve25519-dalek-source/src/ed25519.rs
Isis Lovecruft e6528bd683
Create new module for public key code.
2018-12-30 03:53:42 +00:00

508 lines
17 KiB
Rust
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// -*- mode: rust; -*-
//
// This file is part of ed25519-dalek.
// Copyright (c) 2017-2018 isis lovecruft
// See LICENSE for licensing information.
//
// Authors:
// - isis agora lovecruft <isis@patternsinthevoid.net>
//! A Rust implementation of ed25519 key generation, signing, and verification.
use core::default::Default;
use rand::CryptoRng;
use rand::Rng;
#[cfg(feature = "serde")]
use serde::{Serialize, Deserialize};
#[cfg(feature = "serde")]
use serde::{Serializer, Deserializer};
#[cfg(feature = "serde")]
use serde::de::Error as SerdeError;
#[cfg(feature = "serde")]
use serde::de::Visitor;
pub use sha2::Sha512;
pub use curve25519_dalek::digest::Digest;
use curve25519_dalek::digest::generic_array::typenum::U64;
use curve25519_dalek::constants;
use curve25519_dalek::edwards::EdwardsPoint;
use curve25519_dalek::scalar::Scalar;
pub use crate::constants::*;
pub use crate::errors::*;
pub use crate::public::*;
pub use crate::secret::*;
pub use crate::signature::*;
/// Verify a batch of `signatures` on `messages` with their respective `public_keys`.
///
/// # Inputs
///
/// * `messages` is a slice of byte slices, one per signed message.
/// * `signatures` is a slice of `Signature`s.
/// * `public_keys` is a slice of `PublicKey`s.
/// * `csprng` is an implementation of `Rng + CryptoRng`, such as
/// `rand::rngs::ThreadRng`.
///
/// # Panics
///
/// This function will panic if the `messages, `signatures`, and `public_keys`
/// slices are not equal length.
///
/// # Returns
///
/// * A `Result` whose `Ok` value is an emtpy tuple and whose `Err` value is a
/// `SignatureError` containing a description of the internal error which
/// occured.
///
/// # Examples
///
/// ```
/// extern crate ed25519_dalek;
/// extern crate rand;
///
/// use ed25519_dalek::verify_batch;
/// use ed25519_dalek::Keypair;
/// use ed25519_dalek::PublicKey;
/// use ed25519_dalek::Signature;
/// use rand::thread_rng;
/// use rand::rngs::ThreadRng;
///
/// # fn main() {
/// let mut csprng: ThreadRng = thread_rng();
/// let keypairs: Vec<Keypair> = (0..64).map(|_| Keypair::generate(&mut csprng)).collect();
/// let msg: &[u8] = b"They're good dogs Brant";
/// let messages: Vec<&[u8]> = (0..64).map(|_| msg).collect();
/// let signatures: Vec<Signature> = keypairs.iter().map(|key| key.sign(&msg)).collect();
/// let public_keys: Vec<PublicKey> = keypairs.iter().map(|key| key.public).collect();
///
/// let result = verify_batch(&messages[..], &signatures[..], &public_keys[..]);
/// assert!(result.is_ok());
/// # }
/// ```
#[cfg(any(feature = "alloc", feature = "std"))]
#[allow(non_snake_case)]
pub fn verify_batch(
messages: &[&[u8]],
signatures: &[Signature],
public_keys: &[PublicKey],
) -> Result<(), SignatureError>
{
const ASSERT_MESSAGE: &'static [u8] = b"The number of messages, signatures, and public keys must be equal.";
assert!(signatures.len() == messages.len(), ASSERT_MESSAGE);
assert!(signatures.len() == public_keys.len(), ASSERT_MESSAGE);
assert!(public_keys.len() == messages.len(), ASSERT_MESSAGE);
#[cfg(feature = "alloc")]
use alloc::vec::Vec;
#[cfg(feature = "std")]
use std::vec::Vec;
use core::iter::once;
use rand::thread_rng;
use curve25519_dalek::traits::IsIdentity;
use curve25519_dalek::traits::VartimeMultiscalarMul;
// Select a random 128-bit scalar for each signature.
let zs: Vec<Scalar> = signatures
.iter()
.map(|_| Scalar::from(thread_rng().gen::<u128>()))
.collect();
// Compute the basepoint coefficient, ∑ s[i]z[i] (mod l)
let B_coefficient: Scalar = signatures
.iter()
.map(|sig| sig.s)
.zip(zs.iter())
.map(|(s, z)| z * s)
.sum();
// Compute H(R || A || M) for each (signature, public_key, message) triplet
let hrams = (0..signatures.len()).map(|i| {
let mut h: Sha512 = Sha512::default();
h.input(signatures[i].R.as_bytes());
h.input(public_keys[i].as_bytes());
h.input(&messages[i]);
Scalar::from_hash(h)
});
// Multiply each H(R || A || M) by the random value
let zhrams = hrams.zip(zs.iter()).map(|(hram, z)| hram * z);
let Rs = signatures.iter().map(|sig| sig.R.decompress());
let As = public_keys.iter().map(|pk| Some(pk.1));
let B = once(Some(constants::ED25519_BASEPOINT_POINT));
// Compute (-∑ z[i]s[i] (mod l)) B + ∑ z[i]R[i] + ∑ (z[i]H(R||A||M)[i] (mod l)) A[i] = 0
let id = EdwardsPoint::optional_multiscalar_mul(
once(-B_coefficient).chain(zs.iter().cloned()).chain(zhrams),
B.chain(Rs).chain(As),
).ok_or_else(|| SignatureError(InternalError::VerifyError))?;
if id.is_identity() {
Ok(())
} else {
Err(SignatureError(InternalError::VerifyError))
}
}
/// An ed25519 keypair.
#[derive(Debug, Default)] // we derive Default in order to use the clear() method in Drop
pub struct Keypair {
/// The secret half of this keypair.
pub secret: SecretKey,
/// The public half of this keypair.
pub public: PublicKey,
}
impl Keypair {
/// Convert this keypair to bytes.
///
/// # Returns
///
/// An array of bytes, `[u8; KEYPAIR_LENGTH]`. The first
/// `SECRET_KEY_LENGTH` of bytes is the `SecretKey`, and the next
/// `PUBLIC_KEY_LENGTH` bytes is the `PublicKey` (the same as other
/// libraries, such as [Adam Langley's ed25519 Golang
/// implementation](https://github.com/agl/ed25519/)).
pub fn to_bytes(&self) -> [u8; KEYPAIR_LENGTH] {
let mut bytes: [u8; KEYPAIR_LENGTH] = [0u8; KEYPAIR_LENGTH];
bytes[..SECRET_KEY_LENGTH].copy_from_slice(self.secret.as_bytes());
bytes[SECRET_KEY_LENGTH..].copy_from_slice(self.public.as_bytes());
bytes
}
/// Construct a `Keypair` from the bytes of a `PublicKey` and `SecretKey`.
///
/// # Inputs
///
/// * `bytes`: an `&[u8]` representing the scalar for the secret key, and a
/// compressed Edwards-Y coordinate of a point on curve25519, both as bytes.
/// (As obtained from `Keypair::to_bytes()`.)
///
/// # Warning
///
/// Absolutely no validation is done on the key. If you give this function
/// bytes which do not represent a valid point, or which do not represent
/// corresponding parts of the key, then your `Keypair` will be broken and
/// it will be your fault.
///
/// # Returns
///
/// A `Result` whose okay value is an EdDSA `Keypair` or whose error value
/// is an `SignatureError` describing the error that occurred.
pub fn from_bytes<'a>(bytes: &'a [u8]) -> Result<Keypair, SignatureError> {
if bytes.len() != KEYPAIR_LENGTH {
return Err(SignatureError(InternalError::BytesLengthError{
name: "Keypair", length: KEYPAIR_LENGTH}));
}
let secret = SecretKey::from_bytes(&bytes[..SECRET_KEY_LENGTH])?;
let public = PublicKey::from_bytes(&bytes[SECRET_KEY_LENGTH..])?;
Ok(Keypair{ secret: secret, public: public })
}
/// Generate an ed25519 keypair.
///
/// # Example
///
/// ```
/// extern crate rand;
/// extern crate ed25519_dalek;
///
/// # #[cfg(feature = "std")]
/// # fn main() {
///
/// use rand::Rng;
/// use rand::rngs::OsRng;
/// use ed25519_dalek::Keypair;
/// use ed25519_dalek::Signature;
///
/// let mut csprng: OsRng = OsRng::new().unwrap();
/// let keypair: Keypair = Keypair::generate(&mut csprng);
///
/// # }
/// #
/// # #[cfg(not(feature = "std"))]
/// # fn main() { }
/// ```
///
/// # Input
///
/// A CSPRNG with a `fill_bytes()` method, e.g. `rand_chacha::ChaChaRng`.
///
/// The caller must also supply a hash function which implements the
/// `Digest` and `Default` traits, and which returns 512 bits of output.
/// The standard hash function used for most ed25519 libraries is SHA-512,
/// which is available with `use sha2::Sha512` as in the example above.
/// Other suitable hash functions include Keccak-512 and Blake2b-512.
pub fn generate<R>(csprng: &mut R) -> Keypair
where R: CryptoRng + Rng,
{
let sk: SecretKey = SecretKey::generate(csprng);
let pk: PublicKey = (&sk).into();
Keypair{ public: pk, secret: sk }
}
/// Sign a message with this keypair's secret key.
pub fn sign(&self, message: &[u8]) -> Signature
{
let expanded: ExpandedSecretKey = (&self.secret).into();
expanded.sign(&message, &self.public)
}
/// Sign a `prehashed_message` with this `Keypair` using the
/// Ed25519ph algorithm defined in [RFC8032 §5.1][rfc8032].
///
/// # Inputs
///
/// * `prehashed_message` is an instantiated hash digest with 512-bits of
/// output which has had the message to be signed previously fed into its
/// state.
/// * `context` is an optional context string, up to 255 bytes inclusive,
/// which may be used to provide additional domain separation. If not
/// set, this will default to an empty string.
///
/// # Returns
///
/// An Ed25519ph [`Signature`] on the `prehashed_message`.
///
/// # Examples
///
/// ```
/// extern crate ed25519_dalek;
/// extern crate rand;
///
/// use ed25519_dalek::Digest;
/// use ed25519_dalek::Keypair;
/// use ed25519_dalek::Sha512;
/// use ed25519_dalek::Signature;
/// use rand::thread_rng;
///
/// # #[cfg(feature = "std")]
/// # fn main() {
/// let mut csprng = thread_rng();
/// let keypair: Keypair = Keypair::generate(&mut csprng);
/// let message: &[u8] = b"All I want is to pet all of the dogs.";
///
/// // Create a hash digest object which we'll feed the message into:
/// let mut prehashed: Sha512 = Sha512::new();
///
/// prehashed.input(message);
/// # }
/// #
/// # #[cfg(not(feature = "std"))]
/// # fn main() { }
/// ```
///
/// If you want, you can optionally pass a "context". It is generally a
/// good idea to choose a context and try to make it unique to your project
/// and this specific usage of signatures.
///
/// For example, without this, if you were to [convert your OpenPGP key
/// to a Bitcoin key][terrible_idea] (just as an example, and also Don't
/// Ever Do That) and someone tricked you into signing an "email" which was
/// actually a Bitcoin transaction moving all your magic internet money to
/// their address, it'd be a valid transaction.
///
/// By adding a context, this trick becomes impossible, because the context
/// is concatenated into the hash, which is then signed. So, going with the
/// previous example, if your bitcoin wallet used a context of
/// "BitcoinWalletAppTxnSigning" and OpenPGP used a context (this is likely
/// the least of their safety problems) of "GPGsCryptoIsntConstantTimeLol",
/// then the signatures produced by both could never match the other, even
/// if they signed the exact same message with the same key.
///
/// Let's add a context for good measure (remember, you'll want to choose
/// your own!):
///
/// ```
/// # extern crate ed25519_dalek;
/// # extern crate rand;
/// #
/// # use ed25519_dalek::Digest;
/// # use ed25519_dalek::Keypair;
/// # use ed25519_dalek::Signature;
/// # use ed25519_dalek::Sha512;
/// # use rand::thread_rng;
/// #
/// # #[cfg(feature = "std")]
/// # fn main() {
/// # let mut csprng = thread_rng();
/// # let keypair: Keypair = Keypair::generate(&mut csprng);
/// # let message: &[u8] = b"All I want is to pet all of the dogs.";
/// # let mut prehashed: Sha512 = Sha512::new();
/// # prehashed.input(message);
/// #
/// let context: &[u8] = b"Ed25519DalekSignPrehashedDoctest";
///
/// let sig: Signature = keypair.sign_prehashed(prehashed, Some(context));
/// # }
/// #
/// # #[cfg(not(feature = "std"))]
/// # fn main() { }
/// ```
///
/// [rfc8032]: https://tools.ietf.org/html/rfc8032#section-5.1
/// [terrible_idea]: https://github.com/isislovecruft/scripts/blob/master/gpgkey2bc.py
pub fn sign_prehashed<D>(
&self,
prehashed_message: D,
context: Option<&'static [u8]>
) -> Signature
where
D: Digest<OutputSize = U64>,
{
let expanded: ExpandedSecretKey = (&self.secret).into(); // xxx thanks i hate this
expanded.sign_prehashed(prehashed_message, &self.public, context)
}
/// Verify a signature on a message with this keypair's public key.
pub fn verify(
&self,
message: &[u8],
signature: &Signature
) -> Result<(), SignatureError>
{
self.public.verify(message, signature)
}
/// Verify a `signature` on a `prehashed_message` using the Ed25519ph algorithm.
///
/// # Inputs
///
/// * `prehashed_message` is an instantiated hash digest with 512-bits of
/// output which has had the message to be signed previously fed into its
/// state.
/// * `context` is an optional context string, up to 255 bytes inclusive,
/// which may be used to provide additional domain separation. If not
/// set, this will default to an empty string.
/// * `signature` is a purported Ed25519ph [`Signature`] on the `prehashed_message`.
///
/// # Returns
///
/// Returns `true` if the `signature` was a valid signature created by this
/// `Keypair` on the `prehashed_message`.
///
/// # Examples
///
/// ```
/// extern crate ed25519_dalek;
/// extern crate rand;
///
/// use ed25519_dalek::Digest;
/// use ed25519_dalek::Keypair;
/// use ed25519_dalek::Signature;
/// use ed25519_dalek::Sha512;
/// use rand::thread_rng;
///
/// # #[cfg(feature = "std")]
/// # fn main() {
/// let mut csprng = thread_rng();
/// let keypair: Keypair = Keypair::generate(&mut csprng);
/// let message: &[u8] = b"All I want is to pet all of the dogs.";
///
/// let mut prehashed: Sha512 = Sha512::default();
/// prehashed.input(message);
///
/// let context: &[u8] = b"Ed25519DalekSignPrehashedDoctest";
///
/// let sig: Signature = keypair.sign_prehashed(prehashed, Some(context));
///
/// // The sha2::Sha512 struct doesn't implement Copy, so we'll have to create a new one:
/// let mut prehashed_again: Sha512 = Sha512::default();
/// prehashed_again.input(message);
///
/// let verified = keypair.public.verify_prehashed(prehashed_again, Some(context), &sig);
///
/// assert!(verified.is_ok());
/// # }
/// #
/// # #[cfg(not(feature = "std"))]
/// # fn main() { }
/// ```
///
/// [rfc8032]: https://tools.ietf.org/html/rfc8032#section-5.1
pub fn verify_prehashed<D>(
&self,
prehashed_message: D,
context: Option<&[u8]>,
signature: &Signature
) -> Result<(), SignatureError>
where
D: Digest<OutputSize = U64>,
{
self.public.verify_prehashed(prehashed_message, context, signature)
}
}
#[cfg(feature = "serde")]
impl Serialize for Keypair {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer {
serializer.serialize_bytes(&self.to_bytes()[..])
}
}
#[cfg(feature = "serde")]
impl<'d> Deserialize<'d> for Keypair {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: Deserializer<'d> {
struct KeypairVisitor;
impl<'d> Visitor<'d> for KeypairVisitor {
type Value = Keypair;
fn expecting(&self, formatter: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
formatter.write_str("An ed25519 keypair, 64 bytes in total where the secret key is \
the first 32 bytes and is in unexpanded form, and the second \
32 bytes is a compressed point for a public key.")
}
fn visit_bytes<E>(self, bytes: &[u8]) -> Result<Keypair, E> where E: SerdeError {
let secret_key = SecretKey::from_bytes(&bytes[..SECRET_KEY_LENGTH]);
let public_key = PublicKey::from_bytes(&bytes[SECRET_KEY_LENGTH..]);
if secret_key.is_ok() && public_key.is_ok() {
Ok(Keypair{ secret: secret_key.unwrap(), public: public_key.unwrap() })
} else {
Err(SerdeError::invalid_length(bytes.len(), &self))
}
}
}
deserializer.deserialize_bytes(KeypairVisitor)
}
}
#[cfg(test)]
mod test {
use super::*;
use clear_on_drop::clear::Clear;
#[test]
fn keypair_clear_on_drop() {
let mut keypair: Keypair = Keypair::from_bytes(&[1u8; KEYPAIR_LENGTH][..]).unwrap();
keypair.clear();
fn as_bytes<T>(x: &T) -> &[u8] {
use std::mem;
use std::slice;
unsafe {
slice::from_raw_parts(x as *const T as *const u8, mem::size_of_val(x))
}
}
assert!(!as_bytes(&keypair).contains(&0x15));
}
}
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