store key id for hardware keys (#284)

Signed-off-by: Berend Sliedrecht <[email protected]>

askar-crypto/src/alg/any.rs

@@ -43,7 +43,7 @@ use super::p256_hardware::P256HardwareKeyPair;
 use super::{HasKeyAlg, HasKeyBackend, KeyAlg};
 use crate::{
     backend::KeyBackend,
-    buffer::{ResizeBuffer, WriteBuffer},
+    buffer::{ResizeBuffer, SecretBytes, WriteBuffer},
     encrypt::{KeyAeadInPlace, KeyAeadParams},
     error::Error,
     jwk::{FromJwk, JwkEncoder, JwkParts, ToJwk},
@@ -92,6 +92,11 @@ impl AnyKey {
     pub fn key_type_id(&self) -> TypeId {
         self.0.as_any().type_id()
     }
+
+    #[inline]
+    pub fn key_id(&self) -> Result<SecretBytes, Error> {
+        get_key_id_any(self)
+    }
 }
 
 /// Create `AnyKey` instances from various sources
@@ -570,6 +575,18 @@ fn convert_key_any<R: AllocKey>(key: &AnyKey, alg: KeyAlg) -> Result<R, Error> {
     }
 }
 
+#[inline]
+fn get_key_id_any(key: &AnyKey) -> Result<SecretBytes, Error> {
+    match key.algorithm() {
+        #[cfg(feature = "p256_hardware")]
+        KeyAlg::EcCurve(EcCurves::Secp256r1) => {
+            Ok(key.assume::<P256HardwareKeyPair>().key_id.clone())
+        }
+        #[allow(unreachable_patterns)]
+        _ => Err(err_msg!(Unsupported, "Unsupported get key id operation")),
+    }
+}
+
 impl FromJwk for Box<AnyKey> {
     fn from_jwk_parts(jwk: JwkParts<'_>) -> Result<Self, Error> {
         from_jwk_any(jwk)

askar-crypto/src/alg/p256_hardware.rs

@@ -8,7 +8,7 @@ use super::{
     EcCurves, HasKeyAlg, HasKeyBackend, KeyAlg, KeyBackend,
 };
 use crate::{
-    buffer::WriteBuffer,
+    buffer::{SecretBytes, WriteBuffer},
     error::{Error, ErrorKind},
     generic_array::typenum::{U32, U33, U65},
     jwk::ToJwk,
@@ -50,17 +50,23 @@ impl From<SecureEnvError> for Error {
 
 /// A P-256 (secp256r1) reference to a key pair stored in hardware
 #[derive(Debug)]
-pub struct P256HardwareKeyPair(P256HardwareKeyReference);
+pub struct P256HardwareKeyPair {
+    pub(crate) inner: P256HardwareKeyReference,
+    pub(crate) key_id: SecretBytes,
+}
 
 impl P256HardwareKeyPair {
     pub(crate) fn get_p256_keypair(&self) -> Result<P256KeyPair, Error> {
-        let public_key = self.0.get_public_key()?;
+        let public_key = self.inner.get_public_key()?;
         P256KeyPair::from_public_bytes(&public_key)
     }
 
     /// Sign a message with the secret key
     pub fn sign(&self, message: &[u8]) -> Option<[u8; ES256_SIGNATURE_LENGTH]> {
-        self.0.sign(message).ok().and_then(|s| s.try_into().ok())
+        self.inner
+            .sign(message)
+            .ok()
+            .and_then(|s| s.try_into().ok())
     }
 
     /// Verify a signature with the public key
@@ -75,12 +81,18 @@ impl P256HardwareKeyPair {
     /// For this method the `rng` source is disregarded and the Secure Elements source will be
     /// used.
     pub fn generate(id: &str) -> Result<Self, Error> {
-        Ok(Self(SecureEnvironment::generate_keypair(id)?))
+        Ok(Self {
+            inner: SecureEnvironment::generate_keypair(id)?,
+            key_id: SecretBytes::from_slice(id.as_bytes()),
+        })
     }
 
     /// Fetch the keypair from the Secure Element via the id
     pub fn from_id(id: &str) -> Result<Self, Error> {
-        Ok(Self(SecureEnvironment::get_keypair_by_id(id)?))
+        Ok(Self {
+            inner: SecureEnvironment::get_keypair_by_id(id)?,
+            key_id: SecretBytes::from_slice(id.as_bytes()),
+        })
     }
 }
 
@@ -90,7 +102,7 @@ impl ToPublicBytes for P256HardwareKeyPair {
     }
 
     fn write_public_bytes(&self, out: &mut dyn WriteBuffer) -> Result<(), Error> {
-        let public_key = self.0.get_public_key()?;
+        let public_key = self.inner.get_public_key()?;
         out.buffer_write(&public_key)
     }
 }

src/ffi/key.rs

@@ -597,7 +597,6 @@ pub extern "C" fn askar_key_get_supported_backends(out: *mut StringListHandle) -
 
         let string_list = StringListHandle::create(FfiStringList::from(backends));
 
-
         unsafe { *out = string_list };
 
         Ok(ErrorCode::Success)

src/store.rs

@@ -345,7 +345,11 @@ impl Session {
         tags: Option<&[EntryTag]>,
         expiry_ms: Option<i64>,
     ) -> Result<(), Error> {
-        let data = key.encode()?;
+        let data = if key.is_hardware_backed() {
+            key.inner.key_id()?
+        } else {
+            key.encode()?
+        };
         let params = KeyParams {
             metadata: metadata.map(str::to_string),
             reference,