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|
//! Asymmetric crypt operations.
use nettle::{dsa, ecc, ecdsa, ed25519, rsa, Yarrow};
use crate::packet::{self, key, Key};
use crate::crypto::SessionKey;
use crate::crypto::mpis::{self, MPI};
use crate::constants::{Curve, HashAlgorithm};
use crate::Error;
use crate::Result;
/// Creates a signature.
///
/// This is a low-level mechanism to produce an arbitrary OpenPGP
/// signature. Using this trait allows Sequoia to perform all
/// operations involving signing to use a variety of secret key
/// storage mechanisms (e.g. smart cards).
pub trait Signer<R>
where R: key::KeyRole
{
/// Returns a reference to the public key.
fn public(&self) -> &Key<key::PublicParts, R>;
/// Creates a signature over the `digest` produced by `hash_algo`.
fn sign(&mut self, hash_algo: HashAlgorithm, digest: &[u8])
-> Result<mpis::Signature>;
}
/// Decrypts a message.
///
/// This is a low-level mechanism to decrypt an arbitrary OpenPGP
/// ciphertext. Using this trait allows Sequoia to perform all
/// operations involving decryption to use a variety of secret key
/// storage mechanisms (e.g. smart cards).
pub trait Decryptor<R>
where R: key::KeyRole
{
/// Returns a reference to the public key.
fn public(&self) -> &Key<key::PublicParts, R>;
/// Decrypts `ciphertext`, returning the plain session key.
fn decrypt(&mut self, ciphertext: &mpis::Ciphertext)
-> Result<SessionKey>;
}
/// A cryptographic key pair.
///
/// A `KeyPair` is a combination of public and secret key. If both
/// are available in memory, a `KeyPair` is a convenient
/// implementation of [`Signer`] and [`Decryptor`].
///
/// [`Signer`]: trait.Signer.html
/// [`Decryptor`]: trait.Decryptor.html
#[derive(Clone)]
pub struct KeyPair<R>
where R: key::KeyRole
{
public: Key<key::PublicParts, R>,
secret: packet::key::Unencrypted,
}
impl<R> KeyPair<R>
where R: key::KeyRole
{
/// Creates a new key pair.
pub fn new(public: Key<key::PublicParts, R>,
secret: packet::key::Unencrypted)
-> Result<Self>
{
Ok(Self {
public: public,
secret: secret,
})
}
/// Returns a reference to the public key.
pub fn public(&self) -> &Key<key::PublicParts, R> {
&self.public
}
/// Returns a reference to the secret key.
pub fn secret(&self) -> &packet::key::Unencrypted {
&self.secret
}
}
impl<R> Signer<R> for KeyPair<R>
where R: key::KeyRole
{
fn public(&self) -> &Key<key::PublicParts, R> {
&self.public
}
fn sign(&mut self, hash_algo: HashAlgorithm, digest: &[u8])
-> Result<mpis::Signature>
{
use crate::PublicKeyAlgorithm::*;
use crate::crypto::mpis::PublicKey;
let mut rng = Yarrow::default();
self.secret.map(|secret| {
#[allow(deprecated)]
match (self.public.pk_algo(), self.public.mpis(), secret)
{
(RSASign,
&PublicKey::RSA { ref e, ref n },
&mpis::SecretKeyMaterial::RSA { ref p, ref q, ref d, .. }) |
(RSAEncryptSign,
&PublicKey::RSA { ref e, ref n },
&mpis::SecretKeyMaterial::RSA { ref p, ref q, ref d, .. }) => {
let public = rsa::PublicKey::new(n.value(), e.value())?;
let secret = rsa::PrivateKey::new(d.value(), p.value(),
q.value(), Option::None)?;
// The signature has the length of the modulus.
let mut sig = vec![0u8; n.value().len()];
// As described in [Section 5.2.2 and 5.2.3 of RFC 4880],
// to verify the signature, we need to encode the
// signature data in a PKCS1-v1.5 packet.
//
// [Section 5.2.2 and 5.2.3 of RFC 4880]:
// https://tools.ietf.org/html/rfc4880#section-5.2.2
rsa::sign_digest_pkcs1(&public, &secret, digest,
hash_algo.oid()?,
&mut rng, &mut sig)?;
Ok(mpis::Signature::RSA {
s: MPI::new(&sig),
})
},
(DSA,
&PublicKey::DSA { ref p, ref q, ref g, .. },
&mpis::SecretKeyMaterial::DSA { ref x }) => {
let params = dsa::Params::new(p.value(), q.value(), g.value());
let secret = dsa::PrivateKey::new(x.value());
let sig = dsa::sign(¶ms, &secret, digest, &mut rng)?;
Ok(mpis::Signature::DSA {
r: MPI::new(&sig.r()),
s: MPI::new(&sig.s()),
})
},
(EdDSA,
&PublicKey::EdDSA { ref curve, ref q },
&mpis::SecretKeyMaterial::EdDSA { ref scalar }) => match curve {
Curve::Ed25519 => {
let public = q.decode_point(&Curve::Ed25519)?.0;
let mut sig = vec![0; ed25519::ED25519_SIGNATURE_SIZE];
// Nettle expects the private key to be exactly
// ED25519_KEY_SIZE bytes long but OpenPGP allows leading
// zeros to be stripped.
// Padding has to be unconditional; otherwise we have a
// secret-dependent branch.
let missing = ed25519::ED25519_KEY_SIZE
.saturating_sub(scalar.value().len());
let mut sec = [0u8; ed25519::ED25519_KEY_SIZE];
sec[missing..].copy_from_slice(scalar.value());
let res = ed25519::sign(public, &sec[..], digest, &mut sig);
unsafe {
memsec::memzero(sec.as_mut_ptr(),
ed25519::ED25519_KEY_SIZE);
}
res?;
Ok(mpis::Signature::EdDSA {
r: MPI::new(&sig[..32]),
s: MPI::new(&sig[32..]),
})
},
_ => Err(
Error::UnsupportedEllipticCurve(curve.clone()).into()),
},
(ECDSA,
&PublicKey::ECDSA { ref curve, .. },
&mpis::SecretKeyMaterial::ECDSA { ref scalar }) => {
let secret = match curve {
Curve::NistP256 =>
ecc::Scalar::new::<
|