BROKEN: initial implementation of crypto

I think it's going to be necessary to implement buffered reading after all.

1 files changed, 78 insertions, 0 deletions

diff --git a/src/crypto.rs b/src/crypto.rs
new file mode 100644
index 0000000..726a420
--- /dev/null
+++ b/src/crypto.rs
@@ -0,0 +1,78 @@
+
+use std::{u8, u32};
+use std::io;
+use std::io::{Read,Write, ErrorKind};
+use sodiumoxide::crypto::secretbox;
+use sodiumoxide::crypto::secretbox::{Key, Nonce};
+use rustc_serialize::base64::{ToBase64, FromBase64, STANDARD};
+use std::mem::transmute;
+
+// TODO: handle case of splitting up writes > 2^32 bytes into multiple small writes
+
+pub struct SecretStream<S: Read+Write> {
+    read_nonce: Nonce,
+    write_nonce: Nonce,
+    pub key: Key,
+    inner: S,
+}
+
+impl<S: Read+Write> SecretStream<S> {
+    pub fn new(stream: S) -> SecretStream<S> {
+        SecretStream {
+            inner: stream,
+            read_nonce: secretbox::gen_nonce(),
+            write_nonce: secretbox::gen_nonce(),
+            key: secretbox::gen_key(),
+        }
+    }
+}
+
+impl<S: Read+Write> Read for SecretStream<S> {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let mut header_buf = [0; 4];
+        try!(self.inner.read_exact(&mut header_buf));
+        let len: u32 = unsafe { transmute(header_buf) };
+        let len = len.to_be();
+        if len as usize > buf.len() {
+            return Err(io::Error::new(ErrorKind::Other,
+                format!("Buffer not big enough ({} < {})", buf.len(), len)));
+        }
+        try!(self.inner.read_exact(buf));
+        let cleartext = match secretbox::open(buf, &self.read_nonce, &self.key) {
+            Ok(cleartext) => cleartext,
+            Err(_) => { return Err(io::Error::new(ErrorKind::InvalidData,
+                "Failed to decrypt message (could mean corruption or malicious attack"))},
+        };
+        self.read_nonce.increment_le_inplace();
+        let len = len as usize;
+        buf.clone_from_slice(&cleartext[..len]);
+        return Ok(len as usize);
+    }
+}
+
+impl<S: Read+Write> Write for SecretStream<S> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        assert!(buf.len() < u32::MAX as usize);
+        let len = buf.len() as u32;
+        let header_buf: [u8; 4] = unsafe { transmute(len.to_be()) };
+        try!(self.inner.write_all(&header_buf));
+        let ciphertext = secretbox::seal(buf, &self.write_nonce, &self.key);
+        self.write_nonce.increment_le_inplace();
+        try!(self.inner.write_all(&ciphertext[..]));
+        return Ok(len as usize);
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        return self.inner.flush();
+    }
+}
+
+pub fn key2string(key: &Key) -> String {
+    return (&(key[..])).to_base64(STANDARD);
+}
+
+pub fn string2key(s: &str) -> Result<Key, String> {
+    println!("KEYBYTES: {}", secretbox::KEYBYTES);
+    return Ok(Key::from_slice(&s.as_bytes().from_base64().unwrap()).unwrap());
+}
+