Preparation work to write/encrypt response

Signed-off-by: Luca Fulchir <luca.fulchir@runesauth.com>

src/connection/handshake/dirsync.rs

@@ -14,7 +14,7 @@ use crate::{
     connection::ID,
     enc::{
         asym::{ExchangePubKey, KeyExchange, KeyID},
-        sym::CipherKind,
+        sym::{CipherKind, Secret},
     },
 };
 use ::std::{collections::VecDeque, num::NonZeroU64, vec::Vec};
@@ -250,16 +250,16 @@ impl super::HandshakeParsing for Resp {
 }
 
 /// Decrypted response data
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone)]
 pub struct RespData {
     /// Client nonce, copied from the request
-    client_nonce: Nonce,
+    pub client_nonce: Nonce,
     /// Server Connection ID
-    id: ID,
+    pub id: ID,
     /// Service Connection ID
-    service_id: ID,
+    pub service_id: ID,
     /// Service encryption key
-    service_key: [u8; 32],
+    pub service_key: Secret,
 }
 
 impl RespData {
@@ -282,6 +282,6 @@ impl RespData {
         self.service_id.serialize(&mut out[start..end]);
         start = end;
         end = end + Self::NONCE_LEN;
-        out[start..end].copy_from_slice(&self.service_key);
+        out[start..end].copy_from_slice(self.service_key.as_ref());
     }
 }

src/enc/errors.rs

@@ -9,6 +9,9 @@ pub enum Error {
     /// Not enough data
     #[error("not enough data")]
     NotEnoughData,
+    /// buffer too small
+    #[error("buffer too small")]
+    InsufficientBuffer,
     /// Wrong Key type found.
     /// You might have passed rsa keys where x25519 was expected
     #[error("wrong key type")]

src/enc/hkdf.rs

@@ -30,9 +30,19 @@ impl Drop for HkdfInner {
         }
     }
 }
+impl Clone for HkdfInner {
+    fn clone(&self) -> Self {
+        #[allow(unsafe_code)]
+        unsafe {
+            Self {
+                hkdf: self.hkdf.clone(),
+            }
+        }
+    }
+}
 
 /// Sha3 based HKDF
-#[allow(missing_debug_implementations)]
+#[derive(Clone)]
 pub struct HkdfSha3 {
     inner: HkdfInner,
 }
@@ -60,3 +70,13 @@ impl HkdfSha3 {
         out.into()
     }
 }
+
+// Fake debug implementation to avoid leaking secrets
+impl ::core::fmt::Debug for HkdfSha3 {
+    fn fmt(
+        &self,
+        f: &mut core::fmt::Formatter<'_>,
+    ) -> Result<(), ::std::fmt::Error> {
+        ::core::fmt::Debug::fmt("[hidden hkdf]", f)
+    }
+}

src/enc/sym.rs

@@ -6,10 +6,18 @@ use ::zeroize::Zeroize;
 
 /// Secret, used for keys.
 /// Grants that on drop() we will zero out memory
-#[derive(Zeroize)]
+#[derive(Zeroize, Clone)]
 #[zeroize(drop)]
-#[allow(missing_debug_implementations)]
 pub struct Secret([u8; 32]);
+// Fake debug implementation to avoid leaking secrets
+impl ::core::fmt::Debug for Secret {
+    fn fmt(
+        &self,
+        f: &mut core::fmt::Formatter<'_>,
+    ) -> Result<(), ::std::fmt::Error> {
+        ::core::fmt::Debug::fmt("[hidden secret]", f)
+    }
+}
 
 impl Secret {
     /// New randomly generated secret
@@ -49,12 +57,12 @@ impl CipherKind {
     /// required length of the nonce
     pub fn nonce_len(&self) -> usize {
         // TODO: how the hell do I take this from ::chacha20poly1305?
-        ::ring::aead::CHACHA20_POLY1305.nonce_len()
+        Nonce::len()
     }
     /// required length of the key
     pub fn key_len(&self) -> usize {
-        use ::chacha20poly1305::KeySizeUser;
-        ::chacha20poly1305::XChaCha20Poly1305::key_size()
+        use ::chacha20poly1305::{KeySizeUser, XChaCha20Poly1305};
+        XChaCha20Poly1305::key_size()
     }
     /// Length of the authentication tag
     pub fn tag_len(&self) -> usize {
@@ -109,11 +117,7 @@ impl Cipher {
             }
         }
     }
-    fn decrypt<'a>(
-        &self,
-        aad: AAD,
-        data: &mut VecDeque<u8>,
-    ) -> Result<(), Error> {
+    fn decrypt(&self, aad: AAD, data: &mut VecDeque<u8>) -> Result<(), Error> {
         match self {
             Cipher::XChaCha20Poly1305(cipher) => {
                 use ::chacha20poly1305::{
@@ -147,6 +151,32 @@ impl Cipher {
             }
         }
     }
+    fn encrypt(
+        &self,
+        aad: AAD,
+        nonce: Nonce,
+        data: &mut [u8],
+    ) -> Result<(), Error> {
+        match self {
+            Cipher::XChaCha20Poly1305(cipher) => {
+                use ::chacha20poly1305::{
+                    aead::generic_array::GenericArray, AeadInPlace,
+                };
+                let min_len: usize = CipherKind::XChaCha20Poly1305.nonce_len()
+                    + CipherKind::XChaCha20Poly1305.tag_len()
+                    + 1;
+                if data.len() < min_len {
+                    return Err(Error::InsufficientBuffer);
+                }
+                // write Nonce, then advance it
+
+                // encrypt data
+
+                // add tag
+            }
+        }
+        todo!()
+    }
 }
 
 /// Receive only cipher
@@ -254,7 +284,7 @@ impl Nonce {
         }
     }
     /// Length of this nonce in bytes
-    pub fn len() -> usize {
+    pub const fn len() -> usize {
         return 12;
     }
     /// Get reference to the nonce bytes

src/lib.rs

@@ -61,13 +61,24 @@ struct FenrirInner {
     keys: ArcSwapAny<Arc<Vec<HandshakeKey>>>,
 }
 
+/// Information needed to reply after the key exchange
+#[derive(Debug, Clone)]
+pub struct AuthNeededInfo {
+    /// Parsed handshake
+    pub handshake: Handshake,
+    /// hkdf generated from the handshake
+    pub hkdf: HkdfSha3,
+    /// cipher to be used in both directions
+    pub cipher: CipherKind,
+}
+
 /// Intermediate actions to be taken while parsing the handshake
 #[derive(Debug, Clone)]
 pub enum HandshakeAction {
     /// Parsing finished, all ok, nothing to do
     None,
     /// Packet parsed, now go perform authentication
-    AuthNeeded(Handshake),
+    AuthNeeded(AuthNeededInfo),
 }
 
 // No async here
@@ -144,7 +155,13 @@ impl FenrirInner {
                     }
                     req.set_data(dirsync::ReqData::deserialize(&req.data)?);
 
-                    return Ok(HandshakeAction::AuthNeeded(handshake));
+                    let cipher = req.cipher;
+
+                    return Ok(HandshakeAction::AuthNeeded(AuthNeededInfo {
+                        handshake,
+                        hkdf,
+                        cipher,
+                    }));
                 }
                 DirSync::Resp(resp) => {
                     todo!();
@@ -396,7 +413,7 @@ impl Fenrir {
                 }
             };
             match action {
-                HandshakeAction::AuthNeeded(hshake) => {
+                HandshakeAction::AuthNeeded(authinfo) => {
                     let tk_check = match token_check.load_full() {
                         Some(tk_check) => tk_check,
                         None => {
@@ -410,7 +427,7 @@ impl Fenrir {
                         dirsync::{self, DirSync},
                         HandshakeData,
                     };
-                    match hshake.data {
+                    match authinfo.handshake.data {
                         HandshakeData::DirSync(ds) => match ds {
                             DirSync::Req(req) => {
                                 use dirsync::ReqInner;
@@ -458,6 +475,29 @@ impl Fenrir {
                                 let srv_secret =
                                     enc::sym::Secret::new_rand(&fenrir.rand);
 
+                                let resp_data = dirsync::RespData {
+                                    client_nonce: req_data.nonce,
+                                    id: auth_conn_id,
+                                    service_id: srv_conn_id,
+                                    service_key: srv_secret,
+                                };
+                                // build response
+                                let secret_send =
+                                    authinfo.hkdf.get_secret(b"to_client");
+                                let cipher_send = CipherRecv::new(
+                                    authinfo.cipher,
+                                    secret_send,
+                                );
+                                use crate::enc::sym::AAD;
+                                let aad = AAD(&mut []); // no aad for now
+                                                        /*
+                                                        match cipher_send.encrypt(aad, &mut req.data.ciphertext()) {
+                                                            Ok(()) => req.data.mark_as_cleartext(),
+                                                            Err(e) => {
+                                                                return Err(handshake::Error::Key(e).into());
+                                                            }
+                                                        }
+                                                        */
                                 todo!()
                             }
                             _ => {