1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136

// Copyright 2017 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

//! Individual messages decoding.

use super::{Hmac, StreamCipher};

use crate::error::SecioError;
use futures::prelude::*;
use log::debug;
use std::{cmp::min, pin::Pin, task::Context, task::Poll};

/// Wraps around a `Stream<Item = Vec<u8>>`. The buffers produced by the underlying stream
/// are decoded using the cipher and hmac.
///
/// This struct implements `Stream`, whose stream item are frames of data without the length
/// prefix. The mechanism for removing the length prefix and splitting the incoming data into
/// frames isn't handled by this module.
///
/// Also implements `Sink` for convenience.
#[pin_project::pin_project]
pub struct DecoderMiddleware<S> {
    cipher_state: StreamCipher,
    hmac: Hmac,
    #[pin]
    raw_stream: S,
    nonce: Vec<u8>
}

impl<S> DecoderMiddleware<S> {
    /// Create a new decoder for the given stream, using the provided cipher and HMAC.
    ///
    /// The `nonce` parameter denotes a sequence of bytes which are expected to be found at the
    /// beginning of the stream and are checked for equality.
    pub fn new(raw_stream: S, cipher: StreamCipher, hmac: Hmac, nonce: Vec<u8>) -> DecoderMiddleware<S> {
        DecoderMiddleware {
            cipher_state: cipher,
            hmac,
            raw_stream,
            nonce
        }
    }
}

impl<S> Stream for DecoderMiddleware<S>
where
    S: TryStream<Ok = Vec<u8>>,
    S::Error: Into<SecioError>,
{
    type Item = Result<Vec<u8>, SecioError>;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let this = self.project();

        let frame = match TryStream::try_poll_next(this.raw_stream, cx) {
            Poll::Ready(Some(Ok(t))) => t,
            Poll::Ready(None) => return Poll::Ready(None),
            Poll::Pending => return Poll::Pending,
            Poll::Ready(Some(Err(err))) => return Poll::Ready(Some(Err(err.into()))),
        };

        if frame.len() < this.hmac.num_bytes() {
            debug!("frame too short when decoding secio frame");
            return Poll::Ready(Some(Err(SecioError::FrameTooShort)));
        }
        let content_length = frame.len() - this.hmac.num_bytes();
        {
            let (crypted_data, expected_hash) = frame.split_at(content_length);
            debug_assert_eq!(expected_hash.len(), this.hmac.num_bytes());

            if this.hmac.verify(crypted_data, expected_hash).is_err() {
                debug!("hmac mismatch when decoding secio frame");
                return Poll::Ready(Some(Err(SecioError::HmacNotMatching)));
            }
        }

        let mut data_buf = frame;
        data_buf.truncate(content_length);
        this.cipher_state.decrypt(&mut data_buf);

        if !this.nonce.is_empty() {
            let n = min(data_buf.len(), this.nonce.len());
            if data_buf[.. n] != this.nonce[.. n] {
                return Poll::Ready(Some(Err(SecioError::NonceVerificationFailed)))
            }
            this.nonce.drain(.. n);
            data_buf.drain(.. n);
        }

        Poll::Ready(Some(Ok(data_buf)))
    }
}

impl<S, I> Sink<I> for DecoderMiddleware<S>
where
    S: Sink<I>,
{
    type Error = S::Error;

    fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        let this = self.project();
        Sink::poll_ready(this.raw_stream, cx)
    }

    fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
        let this = self.project();
        Sink::start_send(this.raw_stream, item)
    }

    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        let this = self.project();
        Sink::poll_flush(this.raw_stream, cx)
    }

    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        let this = self.project();
        Sink::poll_close(this.raw_stream, cx)
    }
}