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// -*- mode: rust; -*- // // This file is part of ed25519-dalek. // Copyright (c) 2017-2019 isis lovecruft // See LICENSE for licensing information. // // Authors: // - isis agora lovecruft <isis@patternsinthevoid.net> //! ed25519 keypairs and batch verification. #[allow(unused_imports)] use core::default::Default; use rand_core::{CryptoRng, RngCore}; #[cfg(feature = "serde")] use serde::de::Error as SerdeError; #[cfg(feature = "serde")] use serde::de::Visitor; #[cfg(feature = "serde")] use serde::{Deserialize, Serialize}; #[cfg(feature = "serde")] use serde::{Deserializer, Serializer}; pub use sha2::Sha512; use curve25519_dalek::digest::generic_array::typenum::U64; pub use curve25519_dalek::digest::Digest; #[cfg(all(feature = "batch", any(feature = "alloc", feature = "std")))] use curve25519_dalek::constants; #[cfg(all(feature = "batch", any(feature = "alloc", feature = "std")))] use curve25519_dalek::edwards::EdwardsPoint; #[cfg(all(feature = "batch", any(feature = "alloc", feature = "std")))] 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`. /// /// # 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_os; /// /// use ed25519_dalek::verify_batch; /// use ed25519_dalek::Keypair; /// use ed25519_dalek::PublicKey; /// use ed25519_dalek::Signature; /// use rand_os::OsRng; /// /// # fn main() { /// let mut csprng: OsRng = OsRng::new().unwrap(); /// 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(all(feature = "batch", 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 str = "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::{Rng, 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_core; /// extern crate rand_os; /// extern crate ed25519_dalek; /// /// # #[cfg(feature = "std")] /// # fn main() { /// /// use rand_core::{CryptoRng, RngCore}; /// use rand_os::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_os::OsRng`. /// /// 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 + RngCore, { 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_os; /// /// use ed25519_dalek::Digest; /// use ed25519_dalek::Keypair; /// use ed25519_dalek::Sha512; /// use ed25519_dalek::Signature; /// use rand_os::OsRng; /// /// # #[cfg(feature = "std")] /// # fn main() { /// let mut csprng = OsRng::new().unwrap(); /// 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_os; /// # /// # use ed25519_dalek::Digest; /// # use ed25519_dalek::Keypair; /// # use ed25519_dalek::Signature; /// # use ed25519_dalek::Sha512; /// # use rand_os::OsRng; /// # /// # #[cfg(feature = "std")] /// # fn main() { /// # let mut csprng: OsRng = OsRng::new().unwrap(); /// # 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_os; /// /// use ed25519_dalek::Digest; /// use ed25519_dalek::Keypair; /// use ed25519_dalek::Signature; /// use ed25519_dalek::Sha512; /// use rand_os::OsRng; /// /// # #[cfg(feature = "std")] /// # fn main() { /// let mut csprng: OsRng = OsRng::new().unwrap(); /// 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)); /// /// // 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)); } }