feat(server): UserAgent seal/unseal

server/crates/arbiter-server/src/actors/keyholder/v1.rs

@@ -0,0 +1,241 @@
+use std::ops::Deref as _;
+
+use argon2::{Algorithm, Argon2, password_hash::Salt as ArgonSalt};
+use chacha20poly1305::{
+    AeadInPlace, Key, KeyInit as _, XChaCha20Poly1305, XNonce,
+    aead::{AeadMut, Error, Payload},
+};
+use memsafe::MemSafe;
+use rand::{
+    Rng as _, SeedableRng,
+    rngs::{StdRng, SysRng},
+};
+
+pub const ROOT_KEY_TAG: &[u8] = "arbiter/seal/v1".as_bytes();
+pub const TAG: &[u8] = "arbiter/private-key/v1".as_bytes();
+pub const NONCE_LENGTH: usize = 24;
+
+#[derive(Default)]
+pub struct Nonce([u8; NONCE_LENGTH]);
+impl Nonce {
+    pub fn increment(&mut self) {
+        for i in (0..self.0.len()).rev() {
+            if self.0[i] == 0xFF {
+                self.0[i] = 0;
+            } else {
+                self.0[i] += 1;
+                break;
+            }
+        }
+    }
+
+    pub fn to_vec(&self) -> Vec<u8> {
+        self.0.to_vec()
+    }
+}
+impl<'a> TryFrom<&'a [u8]> for Nonce {
+    type Error = ();
+
+    fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
+        if value.len() != NONCE_LENGTH {
+            return Err(());
+        }
+        let mut nonce = [0u8; NONCE_LENGTH];
+        nonce.copy_from_slice(&value);
+        Ok(Self(nonce))
+    }
+}
+
+pub struct KeyCell(pub(super) MemSafe<Key>);
+impl From<MemSafe<Key>> for KeyCell {
+    fn from(value: MemSafe<Key>) -> Self {
+        Self(value)
+    }
+}
+impl TryFrom<MemSafe<Vec<u8>>> for KeyCell {
+    type Error = ();
+
+    fn try_from(mut value: MemSafe<Vec<u8>>) -> Result<Self, Self::Error> {
+        let value = value.read().unwrap();
+        if value.len() != size_of::<Key>() {
+            return Err(());
+        }
+        let mut cell = MemSafe::new(Key::default()).unwrap();
+        {
+            let mut cell_write = cell.write().unwrap();
+            let cell_slice: &mut [u8] = cell_write.as_mut();
+            cell_slice.copy_from_slice(&value);
+        }
+        Ok(Self(cell))
+    }
+}
+
+impl KeyCell {
+    pub fn new_secure_random() -> Self {
+        let mut key = MemSafe::new(Key::default()).unwrap();
+        {
+            let mut key_buffer = key.write().unwrap();
+            let key_buffer: &mut [u8] = key_buffer.as_mut();
+
+            let mut rng = StdRng::try_from_rng(&mut SysRng).unwrap();
+            rng.fill_bytes(key_buffer);
+        }
+
+        key.into()
+    }
+
+    pub fn into_inner(self) -> MemSafe<Key> {
+        self.0
+    }
+
+    pub fn encrypt_in_place(
+        &mut self,
+        nonce: &Nonce,
+        associated_data: &[u8],
+        mut buffer: impl AsMut<Vec<u8>>,
+    ) -> Result<(), Error> {
+        let key_reader = self.0.read().unwrap();
+        let key_ref = key_reader.deref();
+        let cipher = XChaCha20Poly1305::new(key_ref);
+        let nonce = XNonce::from_slice(nonce.0.as_ref());
+        let buffer = buffer.as_mut();
+        cipher.encrypt_in_place(nonce, associated_data, buffer)
+    }
+    pub fn decrypt_in_place(
+        &mut self,
+        nonce: &Nonce,
+        associated_data: &[u8],
+        buffer: &mut MemSafe<Vec<u8>>,
+    ) -> Result<(), Error> {
+        let key_reader = self.0.read().unwrap();
+        let key_ref = key_reader.deref();
+        let cipher = XChaCha20Poly1305::new(key_ref);
+        let nonce = XNonce::from_slice(nonce.0.as_ref());
+        let mut buffer = buffer.write().unwrap();
+        let buffer: &mut Vec<u8> = buffer.as_mut();
+        cipher.decrypt_in_place(nonce, associated_data, buffer)
+    }
+
+    pub fn encrypt(
+        &mut self,
+        nonce: &Nonce,
+        associated_data: &[u8],
+        plaintext: impl AsRef<[u8]>,
+    ) -> Result<Vec<u8>, Error> {
+        let key_reader = self.0.read().unwrap();
+        let key_ref = key_reader.deref();
+        let mut cipher = XChaCha20Poly1305::new(key_ref);
+        let nonce = XNonce::from_slice(nonce.0.as_ref());
+
+
+        let ciphertext = cipher.encrypt(
+            &nonce,
+            Payload {
+                msg: plaintext.as_ref(),
+                aad: associated_data,
+            },
+        )?;
+        Ok(ciphertext)
+    }
+}
+
+pub type Salt = [u8; ArgonSalt::RECOMMENDED_LENGTH];
+
+pub(super) fn generate_salt() -> Salt {
+    let mut salt = Salt::default();
+    let mut rng = StdRng::try_from_rng(&mut SysRng).unwrap();
+    rng.fill_bytes(&mut salt);
+    salt
+}
+
+/// User password might be of different length, have not enough entropy, etc...
+/// Derive a fixed-length key from the password using Argon2id, which is designed for password hashing and key derivation.
+pub(super) fn derive_seal_key(mut password: MemSafe<Vec<u8>>, salt: &Salt) -> KeyCell {
+    let params = argon2::Params::new(262_144, 3, 4, None).unwrap();
+    let hasher = Argon2::new(Algorithm::Argon2id, argon2::Version::V0x13, params);
+    let mut key = MemSafe::new(Key::default()).unwrap();
+    {
+        let password_source = password.read().unwrap();
+        let mut key_buffer = key.write().unwrap();
+        let key_buffer: &mut [u8] = key_buffer.as_mut();
+
+        hasher
+            .hash_password_into(password_source.deref(), salt, key_buffer)
+            .unwrap();
+    }
+
+    key.into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use memsafe::MemSafe;
+
+    #[test]
+    pub fn derive_seal_key_deterministic() {
+        static PASSWORD: &[u8] = b"password";
+        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let password2 = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let salt = generate_salt();
+
+        let mut key1 = derive_seal_key(password, &salt);
+        let mut key2 = derive_seal_key(password2, &salt);
+
+        let key1_reader = key1.0.read().unwrap();
+        let key2_reader = key2.0.read().unwrap();
+
+        assert_eq!(key1_reader.deref(), key2_reader.deref());
+    }
+
+    #[test]
+    pub fn successful_derive() {
+        static PASSWORD: &[u8] = b"password";
+        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let salt = generate_salt();
+
+        let mut key = derive_seal_key(password, &salt);
+        let key_reader = key.0.read().unwrap();
+        let key_ref = key_reader.deref();
+
+        assert_ne!(key_ref.as_slice(), &[0u8; 32][..]);
+    }
+
+    #[test]
+    pub fn encrypt_decrypt() {
+        static PASSWORD: &[u8] = b"password";
+        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let salt = generate_salt();
+
+        let mut key = derive_seal_key(password, &salt);
+        let nonce = Nonce(*b"unique nonce 123 1231233"); // 24 bytes for XChaCha20Poly1305
+        let associated_data = b"associated data";
+        let mut buffer = b"secret data".to_vec();
+
+        key.encrypt_in_place(&nonce, associated_data, &mut buffer)
+            .unwrap();
+        assert_ne!(buffer, b"secret data");
+
+        let mut buffer = MemSafe::new(buffer).unwrap();
+
+        key.decrypt_in_place(&nonce, associated_data, &mut buffer)
+            .unwrap();
+
+        let buffer = buffer.read().unwrap();
+        assert_eq!(*buffer, b"secret data");
+    }
+
+    #[test]
+    // We should fuzz this
+    pub fn test_nonce_increment() {
+        let mut nonce = Nonce([0u8; NONCE_LENGTH]);
+        nonce.increment();
+
+        assert_eq!(
+            nonce.0,
+            [
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
+            ]
+        );
+    }
+}