trussed 0.1.0

Modern Cryptographic Firmware
Documentation 
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// use core::convert::{TryFrom, TryInto};

use crate::api::*;
use crate::error::Error;
use crate::service::*;
use crate::types::*;

#[inline(never)]
fn load_secret_key(keystore: &mut impl Keystore, key_id: &KeyId)
    -> Result<p256_cortex_m4::SecretKey, Error>
{

    // info_now!("loading keypair");
    let secret_scalar: [u8; 32] = keystore
        .load_key(key::Secrecy::Secret, Some(key::Kind::P256), &key_id)?
        .material.as_slice()
        .try_into()
        .map_err(|_| Error::InternalError)?;

    let secret_key = p256_cortex_m4::SecretKey::from_bytes(&secret_scalar)
        .map_err(|_| Error::InternalError)?;
    Ok(secret_key)
}

#[inline(never)]
fn load_public_key(keystore: &mut impl Keystore, key_id: &KeyId)
    -> Result<p256_cortex_m4::PublicKey, Error>
{
    let compressed_public_key: [u8; 33] = keystore
        .load_key(key::Secrecy::Public, Some(key::Kind::P256), &key_id)?
        .material.as_slice()
        .try_into()
        .map_err(|_| Error::InternalError)?;

    p256_cortex_m4::PublicKey::from_sec1_bytes(&compressed_public_key)
        .map_err(|_| Error::InternalError)
}

#[cfg(feature = "p256")]
impl Agree for super::P256
{
    #[inline(never)]
    fn agree(keystore: &mut impl Keystore, request: &request::Agree)
        -> Result<reply::Agree, Error>
    {
        let private_id = request.private_key;
        let public_id = request.public_key;

        let secret_key = load_secret_key(keystore, &private_id)?;
        let public_key = load_public_key(keystore, &public_id)?;

        let shared_secret = secret_key.agree(&public_key);

        let key_id = keystore.store_key(
            request.attributes.persistence,
            key::Secrecy::Secret, key::Kind::Shared(32),
            shared_secret.as_bytes())?;

        // return handle
        Ok(reply::Agree { shared_secret: key_id })
    }
}

#[cfg(feature = "p256")]
impl DeriveKey for super::P256
{
    #[inline(never)]
    fn derive_key(keystore: &mut impl Keystore, request: &request::DeriveKey)
        -> Result<reply::DeriveKey, Error>
    {
        let base_id = request.base_key;

        let secret_key = load_secret_key(keystore, &base_id)?;
        let public_key = secret_key.public_key();

        let public_id = keystore.store_key(
            request.attributes.persistence,
            key::Secrecy::Public, key::Kind::P256,
            &public_key.to_compressed_sec1_bytes())?;

        Ok(reply::DeriveKey {
            key: public_id
        })
    }
}

#[cfg(feature = "p256")]
impl DeserializeKey for super::P256
{
    #[inline(never)]
    fn deserialize_key(keystore: &mut impl Keystore, request: &request::DeserializeKey)
        -> Result<reply::DeserializeKey, Error>
    {
          // - mechanism: Mechanism
          // - serialized_key: Message
          // - attributes: StorageAttributes

        let public_key = match request.format {
            KeySerialization::Cose => {
                // TODO: this should all be done upstream
                let cose_public_key: cosey::P256PublicKey = crate::cbor_deserialize(
                    &request.serialized_key).map_err(|_| Error::CborError)?;
                let mut serialized_key = [0u8; 64];
                if cose_public_key.x.len() != 32 || cose_public_key.y.len() != 32 {
                    return Err(Error::InvalidSerializedKey);
                }

                serialized_key[..32].copy_from_slice(&cose_public_key.x);
                serialized_key[32..].copy_from_slice(&cose_public_key.y);

                p256_cortex_m4::PublicKey::from_untagged_bytes(&serialized_key)
                    .map_err(|_| Error::InvalidSerializedKey)?
            }

            KeySerialization::EcdhEsHkdf256 => {
                // TODO: this should all be done upstream
                let cose_public_key: cosey::EcdhEsHkdf256PublicKey = crate::cbor_deserialize(
                    &request.serialized_key).map_err(|_| Error::CborError)?;
                let mut serialized_key = [0u8; 64];
                if cose_public_key.x.len() != 32 || cose_public_key.y.len() != 32 {
                    return Err(Error::InvalidSerializedKey);
                }

                serialized_key[..32].copy_from_slice(&cose_public_key.x);
                serialized_key[32..].copy_from_slice(&cose_public_key.y);

                p256_cortex_m4::PublicKey::from_untagged_bytes(&serialized_key)
                    .map_err(|_| Error::InvalidSerializedKey)?
            }

            KeySerialization::Raw => {
                if request.serialized_key.len() != 64 {
                    return Err(Error::InvalidSerializedKey);
                }

                let mut serialized_key = [0u8; 64];
                serialized_key.copy_from_slice(&request.serialized_key[..64]);

                p256_cortex_m4::PublicKey::from_untagged_bytes(&serialized_key)
                    .map_err(|_| Error::InvalidSerializedKey)?
            }

            _ => { return Err(Error::InternalError); }
        };

        let public_id = keystore.store_key(
            request.attributes.persistence,
            key::Secrecy::Public, key::Kind::P256,
            &public_key.to_compressed_sec1_bytes())?;


        Ok(reply::DeserializeKey { key: public_id })
    }
}

#[cfg(feature = "p256")]
impl GenerateKey for super::P256
{
    #[inline(never)]
    fn generate_key(keystore: &mut impl Keystore, request: &request::GenerateKey)
        -> Result<reply::GenerateKey, Error>
    {
        let keypair = p256_cortex_m4::Keypair::random(&mut keystore.rng());

        // store keys
        let key_id = keystore.store_key(
            request.attributes.persistence,
            key::Secrecy::Secret,
            key::Info::from(key::Kind::P256).with_local_flag(),
            &unsafe { keypair.secret.to_bytes()  },
        )?;

        // return handle
        Ok(reply::GenerateKey { key: key_id })
    }

}

#[cfg(feature = "p256")]
impl SerializeKey for super::P256
{
    #[inline(never)]
    fn serialize_key(keystore: &mut impl Keystore, request: &request::SerializeKey)
        -> Result<reply::SerializeKey, Error>
    {

        let key_id = request.key;

        let public_key = load_public_key(keystore, &key_id)?;

        let serialized_key = match request.format {
            KeySerialization::EcdhEsHkdf256 => {
                let cose_pk = cosey::EcdhEsHkdf256PublicKey {
                    x: Bytes::from_slice(&public_key.x()).unwrap(),
                    y: Bytes::from_slice(&public_key.y()).unwrap(),
                };
                crate::cbor_serialize_bytes(&cose_pk).map_err(|_| Error::CborError)?
            }
            KeySerialization::Cose => {
                let cose_pk = cosey::P256PublicKey {
                    x: Bytes::from_slice(&public_key.x()).unwrap(),
                    y: Bytes::from_slice(&public_key.y()).unwrap(),
                };
                crate::cbor_serialize_bytes(&cose_pk).map_err(|_| Error::CborError)?
            }
            KeySerialization::Raw => {
                let mut serialized_key = Message::new();
                serialized_key.extend_from_slice(&public_key.x()).map_err(|_| Error::InternalError)?;
                serialized_key.extend_from_slice(&public_key.y()).map_err(|_| Error::InternalError)?;
                serialized_key
            }
            KeySerialization::Sec1 => {
                let mut serialized_key = Message::new();
                serialized_key.extend_from_slice(&public_key.to_compressed_sec1_bytes()).map_err(|_| Error::InternalError)?;
                serialized_key
            }
        };

        Ok(reply::SerializeKey { serialized_key })
    }
}

#[cfg(feature = "p256")]
impl Exists for super::P256
{
    #[inline(never)]
    fn exists(keystore: &mut impl Keystore, request: &request::Exists)
        -> Result<reply::Exists, Error>
    {
        let key_id = request.key;
        let exists = keystore.exists_key(key::Secrecy::Secret, Some(key::Kind::P256), &key_id);
        Ok(reply::Exists { exists })
    }
}

#[cfg(feature = "p256")]
impl Sign for super::P256
{
    #[inline(never)]
    fn sign(keystore: &mut impl Keystore, request: &request::Sign)
        -> Result<reply::Sign, Error>
    {
        let key_id = request.key;

        let secret_key = load_secret_key(keystore, &key_id)?;
        let signature = secret_key.sign(&request.message, keystore.rng());

        // debug_now!("making signature");
        let serialized_signature = match request.format {
            SignatureSerialization::Asn1Der => {
                let mut buffer = [0u8; 72];
                let l = signature.to_sec1_bytes(&mut buffer);
                Signature::from_slice(&buffer[..l]).unwrap()
            }
            SignatureSerialization::Raw => {
                Signature::from_slice(&signature.to_untagged_bytes()).unwrap()
            }
        };

        // return signature
        Ok(reply::Sign { signature: serialized_signature })
    }

}

#[cfg(feature = "p256")]
impl Sign for super::P256Prehashed
{
    #[inline(never)]
    fn sign(keystore: &mut impl Keystore, request: &request::Sign)
        -> Result<reply::Sign, Error>
    {
        let key_id = request.key;

        let secret_key = load_secret_key(keystore, &key_id)?;
        let signature = secret_key.sign_prehashed(&request.message, keystore.rng());

        // debug_now!("making signature");
        let serialized_signature = match request.format {
            SignatureSerialization::Asn1Der => {
                let mut buffer = [0u8; 72];
                let l = signature.to_sec1_bytes(&mut buffer);
                Signature::from_slice(&buffer[..l]).unwrap()
            }
            SignatureSerialization::Raw => {
                Signature::from_slice(&signature.to_untagged_bytes()).unwrap()
            }
        };

        // return signature
        Ok(reply::Sign { signature: serialized_signature })
    }

}

#[cfg(feature = "p256")]
impl Verify for super::P256
{
    #[inline(never)]
    fn verify(keystore: &mut impl Keystore, request: &request::Verify)
        -> Result<reply::Verify, Error>
    {
        let key_id = request.key;

        let public_key = load_public_key(keystore, &key_id)?;

        let signature = p256_cortex_m4::Signature::from_untagged_bytes(&request.signature)
            // well... or wrong encoding, need r,s in range 1..=n-1
            .map_err(|_| Error::WrongSignatureLength)?;

        if let SignatureSerialization::Raw = request.format {
        } else {
            // well more TODO
            return Err(Error::InvalidSerializationFormat);
        }

        let valid = public_key.verify(&request.message, &signature);
        Ok(reply::Verify { valid } )
    }
}

#[cfg(not(feature = "p256"))]
impl Agree for super::P256 {}
#[cfg(not(feature = "p256"))]
impl DeriveKey for super::P256 {}
#[cfg(not(feature = "p256"))]
impl GenerateKey for super::P256 {}
#[cfg(not(feature = "p256"))]
impl Sign for super::P256 {}
#[cfg(not(feature = "p256"))]
impl Verify for super::P256 {}