From fb1096f9a30b106dce3b1b9cc765edb4d65d8f56 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Fri, 23 Apr 2021 15:52:29 +0100
Subject: [PATCH] begin future for exchanging chacha20 keys

---
 src/crypt.rs           | 15 ++++++++++++
 src/stream.rs          | 24 +++++++++++++++++--
 src/stream/exchange.rs | 40 ++++++++++++++++++++++++++++++++
 src/stream/traits.rs   | 52 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 129 insertions(+), 2 deletions(-)
 create mode 100644 src/stream/exchange.rs

diff --git a/src/crypt.rs b/src/crypt.rs
index a986111..aa1db11 100644
--- a/src/crypt.rs
+++ b/src/crypt.rs
@@ -1,4 +1,8 @@
 use super::*;
+use std::io::{
+    self,
+    Write,
+};
 
 /// TODO: RSA private key
 pub type RsaPrivateKey = ();
@@ -6,7 +10,18 @@ pub type RsaPrivateKey = ();
 /// TODO: RSA public key
 pub type RsaPublicKey = ();
 
+pub(crate) fn rsa_encrypt<W: io::Write>(with: &RsaPublicKey, to: &mut W, buf: &[u8]) -> io::Result<usize>
+{
+    todo!()
+}
+
 pub(crate) fn generate() -> RsaPrivateKey
 {
     todo!()
 }
+
+pub use chacha20stream::{
+    Key,
+    IV,
+    keygen as chacha_keygen,
+};
diff --git a/src/stream.rs b/src/stream.rs
index 85ec774..72935a3 100644
--- a/src/stream.rs
+++ b/src/stream.rs
@@ -21,6 +21,8 @@ use crypt::{
 mod traits;
 pub use traits::*;
 
+mod exchange;
+
 /// Combined Read + Write encryptable async stream.
 ///
 /// The `AsyncRead` and `AsyncWrite` impls of this type forward to the backing impls for `S`.
@@ -35,10 +37,28 @@ pub struct Stream<S>
     #[pin] stream: S,
 }
 
+/// `Stream` with enabled encryption.
+pub struct EncryptedStream<'a, S>
+{
+    read_cipher: Crypter,
+    write_cipher: Crypter,
+    
+    write_crypt_buf_ptr: SliceMeta<u8>,
+    write_crypt_buffer: Vec<u8>,
+    
+    backing: &'a mut Stream<S>,
+}
+
 impl<Tx, Rx> Stream<Merge<Tx, Rx>>
 where Tx: AsyncWrite,
       Rx: AsyncRead
 {
+    /// Exchange RSA keys through this stream.
+    pub async fn exchange(&mut self) -> io::Result<()>
+    {
+	todo!()
+    }
+    
     /// Merge an `AsyncWrite`, and `AsyncRead` stream into `Stream`.
     pub fn merged(tx: Tx, rx: Rx) -> Self
     {
@@ -48,7 +68,7 @@ where Tx: AsyncWrite,
 	}
     }
 }
-
+/*
 impl<S> Stream<S>
 where S: Split,
       S::First: AsyncWrite,
@@ -90,7 +110,7 @@ impl<S: AsyncStream> Stream<S>
 	    meta: self.meta
 	}.split()
     }
-}
+}*/
 
 impl<S> Split for Stream<S>
 where S: Split,
diff --git a/src/stream/exchange.rs b/src/stream/exchange.rs
new file mode 100644
index 0000000..3d41a61
--- /dev/null
+++ b/src/stream/exchange.rs
@@ -0,0 +1,40 @@
+//! RSA and chacha20 key exchange methods
+use super::*;
+/*
+use tokio::prelude::*;
+
+pub async fn write_cckey<W: AsyncWrite + Unpin>(mut to: W, rsa: &crypt::RsaPublicKey, key: &crypt::Key, iv: &crypt::IV) -> std::io::Result<()>
+{
+    let key = {
+	let mut buf = Vec::with_capacity(chacha20stream::key::KEY_SIZE);
+	crypt::rsa_encrypt(rsa, &mut buf, key.as_ref())?;
+	buf
+    };
+
+    to.write_all(&key[..]).await?; //TODO: Find size of `key` here.
+    to.write_all(iv.as_ref()).await?;
+    
+    Ok(())
+}
+ */
+
+/// A future that writes an RSA encrypted chacha20 key to a stream when awaited
+//TODO: Find size of RSA ecnrypted chacha `Key`.
+#[pin_project]
+struct CCKeyWrite<'a, W: AsyncWrite>{
+    /// The bytes of an **already encrypted** chacha20 key.
+    enc_key: Vec<u8>,
+    /// A non-encrypted chacha20 IV.
+    iv: [u8; chacha20stream::key::IV_SIZE],
+
+    /// Stream to write the data to when this future is awaited.
+    #[pin] stream: &'a mut W,
+}
+
+//TODO: impl `Future` for CCKeyWrite should `write_all` both `enc_key` and `iv` to `stream` when `.await`ed.
+impl<'a, W: AsyncWrite> Future for CCKeyWrite<'a, S>
+{
+    type Output = io::Result<()>;
+
+    //todo: how to we `write_all` in `poll`? implement it outselves with looping `poll_write` and `futures::ready!()`?
+}
diff --git a/src/stream/traits.rs b/src/stream/traits.rs
index f2a9e0b..602a43f 100644
--- a/src/stream/traits.rs
+++ b/src/stream/traits.rs
@@ -99,3 +99,55 @@ where Rx: AsyncRead
 	self.rx().poll_read_buf(cx, buf)
     }
 }
+
+/*
+pub(super) enum MaybeFullWrite<'a, S: AsyncWrite>
+{
+    Full(&'a mut Stream<S>),
+    Half(&'a mut WriteHalf<S>),
+}
+
+pub(super) enum MaybeFullRead<'a, S: AsyncRead>
+{
+    Full(&'a mut Stream<S>),
+    Half(&'a mut ReadHalf<S>),
+}
+
+impl<'a, S: AsyncRead> AsMut<dyn AsyncRead + 'a> for MaybeFullRead<'a, S>
+{
+    #[inline] fn as_mut(&mut self) -> &mut (dyn AsyncRead + 'a)
+    {
+	self.as_dyn()
+    }
+}
+
+impl<'a, S: AsyncWrite> AsMut<dyn AsyncWrite + 'a> for MaybeFullWrite<'a, S>
+{
+    #[inline] fn as_mut(&mut self) -> &mut (dyn AsyncWrite + 'a)
+    {
+	self.as_dyn()
+    }
+}
+
+
+impl<'a, S: AsyncRead> MaybeFullRead<'a, S>
+{
+    #[inline(always)] fn as_dyn(&mut self) -> &mut (dyn AsyncRead + 'a)
+    {
+	match self {
+	    Self::Full(f) => f,
+	    Self::Half(h) => h,
+	}
+    }
+}
+impl<'a, S: AsyncWrite> MaybeFullWrite<'a, S>
+{
+    #[inline(always)] fn as_dyn(&mut self) -> &mut (dyn AsyncWrite + 'a)
+    {
+	match self {
+	    Self::Full(f) => f,
+	    Self::Half(h) => h,
+	}
+    }
+}
+*/