adds a signature::Signer implementation for ecc keys

Signed-off-by: Arthur Gautier <[email protected]>

tss-esapi/Cargo.toml

@@ -42,6 +42,7 @@ sha3 = { version = "0.10.8", optional = true }
 sm2 = { version = "0.13.3", optional = true }
 sm3 = { version = "0.4.2", optional = true }
 digest = "0.10.7"
+signature = { version = "2.2.0", optional = true }
 cfg-if = "1.0.0"
 strum = { version = "0.25.0", optional = true }
 strum_macros = { version = "0.25.0", optional = true }
@@ -59,5 +60,5 @@ semver = "1.0.7"
 [features]
 default = ["abstraction"]
 generate-bindings = ["tss-esapi-sys/generate-bindings"]
-abstraction = ["ecdsa", "elliptic-curve", "rsa", "x509-cert", "p192", "p224", "p256", "p384", "p521", "sha1", "sha2", "sha3", "sm2", "sm3"]
+abstraction = ["ecdsa", "elliptic-curve", "signature", "rsa", "x509-cert", "p192", "p224", "p256", "p384", "p521", "sha1", "sha2", "sha3", "sm2", "sm3"]
 integration-tests = ["strum", "strum_macros"]

tss-esapi/src/abstraction/transient/mod.rs

@@ -34,8 +34,10 @@ use std::convert::{AsMut, AsRef, TryFrom, TryInto};
 use zeroize::Zeroize;
 
 mod key_attestation;
+mod signer;
 
 pub use key_attestation::MakeCredParams;
+pub use signer::EcSigner;
 
 /// Parameters for the kinds of keys supported by the context
 #[derive(Debug, Clone, Copy)]

tss-esapi/src/abstraction/transient/signer.rs

@@ -0,0 +1,234 @@
+// Copyright 2024 Contributors to the Parsec project.
+// SPDX-License-Identifier: Apache-2.0
+
+//! Module for exposing a [`signature::Signer`] interface for keys
+//!
+//! This modules presents objects held in a TPM over a [`signature::DigestSigner`] interface.
+use super::TransientKeyContext;
+use crate::{
+    abstraction::{
+        public::AssociatedTpmCurve,
+        transient::{KeyMaterial, KeyParams},
+        AssociatedHashingAlgorithm,
+    },
+    interface_types::algorithm::EccSchemeAlgorithm,
+    structures::{Auth, Digest as TpmDigest, EccScheme, Signature as TpmSignature},
+    Error,
+};
+
+use std::{convert::TryFrom, marker::PhantomData, ops::Add, sync::Mutex};
+
+use digest::{Digest, FixedOutput, Output};
+use ecdsa::{
+    der::{MaxOverhead, MaxSize, Signature as DerSignature},
+    hazmat::{DigestPrimitive, SignPrimitive},
+    Signature, SignatureSize, VerifyingKey,
+};
+use elliptic_curve::{
+    generic_array::ArrayLength,
+    ops::Invert,
+    sec1::{FromEncodedPoint, ModulusSize, ToEncodedPoint},
+    subtle::CtOption,
+    AffinePoint, CurveArithmetic, FieldBytesSize, PrimeCurve, PublicKey, Scalar,
+};
+use signature::{DigestSigner, Error as SigError, KeypairRef, Signer};
+
+/// [`EcSigner`] will sign a payload with an elliptic curve secret key stored on the TPM.
+///
+/// # Parameters
+///
+/// parameter `C` describes the curve that is of use (Nist P-256, Nist P-384, ...)
+///
+/// the hashing algorithm `D` is the digest that will be used for signatures (SHA-256, SHA3-256, ...).
+///
+/// ```no_run
+/// # use tss_esapi::{
+/// #     abstraction::transient::{EcSigner, TransientKeyContextBuilder},
+/// #     TctiNameConf
+/// # };
+/// use p256::NistP256;
+/// use signature::Signer;
+/// #
+/// # // Create context
+/// # let mut context = TransientKeyContextBuilder::new()
+/// #     .with_tcti(
+/// #         TctiNameConf::from_environment_variable().expect("Failed to get TCTI"),
+/// #     )
+/// #     .build()
+/// #     .expect("Failed to create Context");
+///
+/// let (tpm_km, _tpm_auth) = context
+///     .create_key(EcSigner::<NistP256>::key_params(), 0)
+///     .expect("Failed to create a private keypair");
+///
+/// let signer = EcSigner::<NistP256>::new(&mut context, tpm_km, None)
+///      .expect("Failed to create a signer");
+/// let signature: p256::ecdsa::Signature = signer.sign(b"Hello Bob, Alice here.");
+/// ```
+#[derive(Debug)]
+pub struct EcSigner<'ctx, C, D = <C as DigestPrimitive>::Digest>
+where
+    C: PrimeCurve + CurveArithmetic,
+    D: FixedOutput<OutputSize = FieldBytesSize<C>>,
+{
+    context: Mutex<&'ctx mut TransientKeyContext>,
+    key_material: KeyMaterial,
+    key_auth: Option<Auth>,
+    verifying_key: VerifyingKey<C>,
+    _digest: PhantomData<D>,
+}
+
+impl<'ctx, C, D> EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    D: FixedOutput<OutputSize = FieldBytesSize<C>>,
+    C: AssociatedTpmCurve,
+    FieldBytesSize<C>: ModulusSize,
+    AffinePoint<C>: FromEncodedPoint<C> + ToEncodedPoint<C>,
+{
+    pub fn new(
+        context: &'ctx mut TransientKeyContext,
+        key_material: KeyMaterial,
+        key_auth: Option<Auth>,
+    ) -> Result<Self, Error> {
+        let context = Mutex::new(context);
+
+        let public_key = PublicKey::try_from(key_material.public())?;
+        let verifying_key = VerifyingKey::from(public_key);
+
+        Ok(Self {
+            context,
+            key_material,
+            key_auth,
+            verifying_key,
+            _digest: PhantomData,
+        })
+    }
+}
+
+impl<'ctx, C, D> EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    C: AssociatedTpmCurve,
+    D: FixedOutput<OutputSize = FieldBytesSize<C>>,
+    D: AssociatedHashingAlgorithm,
+{
+    /// Key parameters for this curve
+    pub fn key_params() -> KeyParams {
+        KeyParams::Ecc {
+            curve: C::TPM_CURVE,
+            scheme: EccScheme::create(EccSchemeAlgorithm::EcDsa, Some(D::TPM_DIGEST), None)
+                .expect("Failed to create ecc scheme"),
+        }
+    }
+}
+
+impl<'ctx, C, D> AsRef<VerifyingKey<C>> for EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    D: FixedOutput<OutputSize = FieldBytesSize<C>>,
+    Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + SignPrimitive<C>,
+    SignatureSize<C>: ArrayLength<u8>,
+{
+    fn as_ref(&self) -> &VerifyingKey<C> {
+        &self.verifying_key
+    }
+}
+
+impl<'ctx, C, D> KeypairRef for EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    D: FixedOutput<OutputSize = FieldBytesSize<C>>,
+    Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + SignPrimitive<C>,
+    SignatureSize<C>: ArrayLength<u8>,
+{
+    type VerifyingKey = VerifyingKey<C>;
+}
+
+impl<'ctx, C, D> DigestSigner<D, Signature<C>> for EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    C: AssociatedTpmCurve,
+    D: Digest + FixedOutput<OutputSize = FieldBytesSize<C>>,
+    D: AssociatedHashingAlgorithm,
+    Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + SignPrimitive<C>,
+    SignatureSize<C>: ArrayLength<u8>,
+    TpmDigest: From<Output<D>>,
+{
+    fn try_sign_digest(&self, digest: D) -> Result<Signature<C>, SigError> {
+        let digest = TpmDigest::from(digest.finalize_fixed());
+
+        let key_params = Self::key_params();
+        let mut context = self.context.lock().expect("Mutex got poisoned");
+        let signature = context
+            .sign(
+                self.key_material.clone(),
+                key_params,
+                self.key_auth.clone(),
+                digest,
+            )
+            .map_err(SigError::from_source)?;
+        let TpmSignature::EcDsa(signature) = signature else {
+            todo!();
+        };
+
+        let signature = Signature::try_from(signature).map_err(SigError::from_source)?;
+
+        Ok(signature)
+    }
+}
+
+impl<'ctx, C, D> DigestSigner<D, DerSignature<C>> for EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    C: AssociatedTpmCurve,
+    D: Digest + FixedOutput<OutputSize = FieldBytesSize<C>>,
+    D: AssociatedHashingAlgorithm,
+    Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + SignPrimitive<C>,
+    SignatureSize<C>: ArrayLength<u8>,
+    TpmDigest: From<Output<D>>,
+
+    MaxSize<C>: ArrayLength<u8>,
+    <FieldBytesSize<C> as Add>::Output: Add<MaxOverhead> + ArrayLength<u8>,
+{
+    fn try_sign_digest(&self, digest: D) -> Result<DerSignature<C>, SigError> {
+        let signature: Signature<_> = self.try_sign_digest(digest)?;
+        Ok(signature.to_der())
+    }
+}
+
+// TODO: implementations of [`signature::Digest`] should be possible using a simple
+// `#[derive(Signer)]` on the struct, but due to a lack of support for lifetimes, this is not
+// possible yet and will need to be manually implemented
+impl<'ctx, C, D> Signer<Signature<C>> for EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    C: AssociatedTpmCurve,
+    D: Digest + FixedOutput<OutputSize = FieldBytesSize<C>>,
+    D: AssociatedHashingAlgorithm,
+    Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + SignPrimitive<C>,
+    SignatureSize<C>: ArrayLength<u8>,
+    TpmDigest: From<Output<D>>,
+{
+    fn try_sign(&self, msg: &[u8]) -> Result<Signature<C>, SigError> {
+        self.try_sign_digest(D::new_with_prefix(msg))
+    }
+}
+
+impl<'ctx, C, D> Signer<DerSignature<C>> for EcSigner<'ctx, C, D>
+where
+    C: PrimeCurve + CurveArithmetic,
+    C: AssociatedTpmCurve,
+    D: Digest + FixedOutput<OutputSize = FieldBytesSize<C>>,
+    D: AssociatedHashingAlgorithm,
+    Scalar<C>: Invert<Output = CtOption<Scalar<C>>> + SignPrimitive<C>,
+    SignatureSize<C>: ArrayLength<u8>,
+    TpmDigest: From<Output<D>>,
+
+    MaxSize<C>: ArrayLength<u8>,
+    <FieldBytesSize<C> as Add>::Output: Add<MaxOverhead> + ArrayLength<u8>,
+{
+    fn try_sign(&self, msg: &[u8]) -> Result<DerSignature<C>, SigError> {
+        self.try_sign_digest(D::new_with_prefix(msg))
+    }
+}