cipherstash-client 0.34.1-alpha.1

pub use recipher::{
    cipher::ProxyCipher,
    key::{Iv, Key},
    keyset::ProxyKeySet as KeySet,
};

use serde::{Deserialize, Deserializer, Serialize, Serializer};
use sha2::{Digest, Sha256};
use std::ops::Deref;
use uuid::Uuid;
use zeroize::{Zeroize, ZeroizeOnDrop};
use zerokms_protocol::ViturKeyMaterial;

/// NOTE: Debug is safe to implement because [KeySet] is opaque.
#[derive(Debug, Deserialize, Clone, Zeroize, ZeroizeOnDrop, Serialize)]
pub struct ClientKey {
    #[zeroize(skip)]
    #[serde(rename = "client_id")]
    pub key_id: Uuid,

    #[serde(rename = "client_key")]
    pub keyset: V1KeySet,
}

impl ClientKey {
    pub fn new_v1(key_id: Uuid, keyset: KeySet) -> Self {
        Self {
            key_id,
            keyset: V1KeySet(keyset),
        }
    }

    pub fn to_hex_v1(&self) -> serde_cbor::Result<String> {
        self.keyset.to_hex()
    }

    pub fn from_bytes(key_id: Uuid, bytes: &[u8]) -> serde_cbor::Result<Self> {
        Ok(Self {
            key_id,
            keyset: KeySet::from_bytes(bytes).map(V1KeySet)?,
        })
    }

    pub fn from_hex_v1(key_id: Uuid, hex: &str) -> serde_cbor::Result<Self> {
        Ok(Self {
            key_id,
            keyset: V1KeySet::from_hex(hex)?,
        })
    }
}

// FIXME: This shouldn't be Clone but it is needed right now for the JSONB indexer.
#[derive(PartialEq, Eq, Zeroize, ZeroizeOnDrop, Clone)]
#[cfg_attr(test, derive(Default))]
pub struct DataKey {
    pub iv: Iv,
    pub key: Key,
}
opaque_debug::implement!(DataKey);

impl DataKey {
    /// Create a DataKey for a specific [`ClientKey`] given a specific initialisation vector
    /// (IV) and key material obtained from Vitur.
    pub fn from_key_material(key: &ClientKey, iv: Iv, key_material: &ViturKeyMaterial) -> Self {
        let cipher = ProxyCipher::new(key.keyset.keyset());
        let rect = cipher.reencrypt::<16>(&iv, key_material);

        let mut hasher = Sha256::new();
        hasher.update(&rect);

        DataKey {
            iv,
            key: hasher.finalize().into(),
        }
    }

    pub fn key(&self) -> &Key {
        &self.key
    }
}

/// Key used specifically for generating index terms.
#[derive(Zeroize, ZeroizeOnDrop)]
pub struct IndexKey(Key);
opaque_debug::implement!(IndexKey);

impl IndexKey {
    /// Create a [`DataKey`] for a specific [`ClientKey`] given a specific initialisation vector
    /// (IV) and key material obtained from Vitur.
    pub fn from_key_material(key: &ClientKey, key_material: &ViturKeyMaterial) -> Self {
        // We use all zeros for the IV for the keyset index key.
        // This key is not used for encryption but for indexing using PRFs and similar constructions.
        // Even then, because all other datakeys are generated using random IVs, the likelihood of collision is negligible.
        let iv = Iv::default();
        let cipher = ProxyCipher::new(key.keyset.keyset());
        let rect = cipher.reencrypt::<16>(&iv, key_material);

        let mut hasher = blake3::Hasher::new();
        // Fixed info string
        hasher.update(b"ZEROKMS-INDEXKEY");
        hasher.update(&rect);

        let key: Key = {
            let mut key = Key::default();
            hasher.finalize_xof().fill(&mut key);
            key
        };

        hasher.zeroize();

        Self(key)
    }

    pub fn key(&self) -> &Key {
        &self.0
    }
}

impl From<Key> for IndexKey {
    fn from(key: Key) -> Self {
        Self(key)
    }
}

// FIXME: Making this Cloneable for now so that we can use the same key many times for the JSONB indexer.
// We should modifier the indexer so each value has a separate key.
#[derive(PartialEq, Eq, Clone)]
#[cfg_attr(test, derive(Default))]
pub struct DataKeyWithTag {
    pub key: DataKey,
    pub tag: Vec<u8>,
}
opaque_debug::implement!(DataKeyWithTag);

impl DataKeyWithTag {
    /// Create a DataKey for a specific [`ClientKey`] given a specific IV, key material and tag
    /// obtained from Vitur.
    pub fn from_key_material(
        key: &ClientKey,
        iv: Iv,
        key_material: &ViturKeyMaterial,
        tag: Vec<u8>,
    ) -> Self {
        Self {
            key: DataKey::from_key_material(key, iv, key_material),
            tag,
        }
    }
}

impl Deref for DataKeyWithTag {
    type Target = DataKey;

    fn deref(&self) -> &Self::Target {
        &self.key
    }
}

#[derive(Debug, Clone, Zeroize, ZeroizeOnDrop)]
pub struct V1KeySet(pub(super) KeySet);

impl V1KeySet {
    pub fn from_bytes(bytes: &[u8]) -> serde_cbor::Result<Self> {
        KeySet::from_bytes(bytes).map(Self)
    }

    pub(crate) fn to_hex(&self) -> serde_cbor::Result<String> {
        self.0.to_bytes().map(|mut bytes| {
            let hex = base16ct::lower::encode_string(&bytes);
            bytes.zeroize();
            hex
        })
    }

    pub(crate) fn from_hex(hex: &str) -> serde_cbor::Result<Self> {
        let mut bytes = base16ct::lower::decode_vec(hex).map_err(|e| {
            <serde_cbor::Error as serde::de::Error>::custom(format!("invalid hex: {e}"))
        })?;
        let result = Self::from_bytes(&bytes);
        bytes.zeroize();
        result
    }

    fn keyset(&self) -> &KeySet {
        &self.0
    }
}

impl Serialize for V1KeySet {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        let bytes = self.0.to_bytes().map_err(serde::ser::Error::custom)?;
        serdect::slice::serialize_hex_lower_or_bin(&bytes, serializer)
    }
}

impl<'de> Deserialize<'de> for V1KeySet {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        // CBOR encoded keyset is 168 bytes
        let mut buffer = [0; 168];
        serdect::array::deserialize_hex_or_bin(&mut buffer, deserializer)?;
        let keyset = KeySet::from_bytes(&buffer).map_err(serde::de::Error::custom)?;
        buffer.zeroize();

        Ok(Self(keyset))
    }
}

#[cfg(test)]
mod tests {
    use super::{ClientKey, DataKey, IndexKey};
    use recipher::keyset::{EncryptionKeySet, ProxyKeySet};

    #[test]
    fn test_opaque_debug_datakey() {
        let key = DataKey {
            iv: [0; 16],
            key: [0; 32],
        };
        assert_eq!(format!("{key:?}"), "DataKey { ... }");
    }

    #[test]
    fn test_opaque_debug_index_key() {
        let key = IndexKey([0; 32]);
        assert_eq!(format!("{key:?}"), "IndexKey { ... }");
    }

    #[test]
    fn test_v1_keyset_serde() {
        let ek_a = EncryptionKeySet::generate().unwrap();
        let ek_b = EncryptionKeySet::generate().unwrap();
        let keyset = ProxyKeySet::generate(&ek_a, &ek_b);
        let v1_keyset = super::V1KeySet(keyset);

        let serialized = serde_json::to_string(&v1_keyset).unwrap();
        let deserialized: super::V1KeySet = serde_json::from_str(&serialized).unwrap();

        // The current key implementation doesn't implement PartialEq because it can't do it safely.
        assert_eq!(
            v1_keyset.0.to_bytes().unwrap(),
            deserialized.0.to_bytes().unwrap()
        );
    }

    #[test]
    fn test_client_key_toml() {
        let ek_a = EncryptionKeySet::generate().unwrap();
        let ek_b = EncryptionKeySet::generate().unwrap();
        let keyset = ProxyKeySet::generate(&ek_a, &ek_b);
        let key_id = uuid::Uuid::new_v4();
        let client_key = ClientKey::new_v1(key_id, keyset);

        let toml = toml::to_string(&client_key).unwrap();

        let mut table = toml::Table::new();
        table.insert(
            String::from("client_id"),
            toml::Value::String(key_id.to_string()),
        );
        table.insert(
            String::from("client_key"),
            toml::Value::String(client_key.to_hex_v1().unwrap()),
        );

        assert_eq!(toml, table.to_string());
    }
}