libpna 0.33.0

PNA(Portable-Network-Archive) decoding and encoding library
Documentation 
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//! Stream cipher encryption writer.

use block_buffer::BlockSizes;
use cipher::{KeyIvInit, StreamCipher, StreamCipherCore, StreamCipherCoreWrapper};
use std::io::{self, Write};

pub(crate) struct StreamCipherWriter<W, T>
where
    T: StreamCipherCore,
    T::BlockSize: BlockSizes,
{
    w: W,
    cipher: StreamCipherCoreWrapper<T>,
}

impl<W, T> StreamCipherWriter<W, T>
where
    W: Write,
    T: StreamCipherCore,
    T::BlockSize: BlockSizes,
    StreamCipherCoreWrapper<T>: KeyIvInit,
{
    pub(crate) fn new(w: W, key: &[u8], iv: &[u8]) -> io::Result<Self> {
        Ok(Self {
            w,
            cipher: StreamCipherCoreWrapper::<T>::new_from_slices(key, iv)
                .map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?,
        })
    }

    #[inline]
    pub(crate) fn get_mut(&mut self) -> &mut W {
        &mut self.w
    }

    pub(crate) fn finish(self) -> io::Result<W> {
        Ok(self.w)
    }
}

impl<W, T> Write for StreamCipherWriter<W, T>
where
    W: Write,
    T: StreamCipherCore,
    T::BlockSize: BlockSizes,
    StreamCipherCoreWrapper<T>: StreamCipher,
{
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        if buf.is_empty() {
            return Ok(0);
        }
        let mut buf = buf.to_vec();
        self.cipher.apply_keystream(&mut buf);
        self.w.write_all(&buf)?;
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        self.w.flush()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ctr::CtrCore;
    #[cfg(all(target_family = "wasm", target_os = "unknown"))]
    use wasm_bindgen_test::wasm_bindgen_test as test;

    type CtrWriter<W, C, F> = StreamCipherWriter<W, CtrCore<C, F>>;
    type Aes128Ctr64LEWriter<W> = CtrWriter<W, aes::Aes128, ctr::flavors::Ctr64LE>;

    #[test]
    fn write_aes128_ctr64le() {
        let key = [0x42u8; 16];
        let iv = [0x24u8; 16];
        let plaintext = *b"hello world! this is my plaintext.";
        let ciphertext = [
            51, 87, 18, 30, 187, 90, 41, 70, 139, 216, 97, 70, 117, 150, 206, 61, 165, 155, 222,
            228, 45, 204, 6, 20, 222, 169, 85, 54, 141, 138, 93, 192, 202, 212,
        ];
        // encrypt in-place
        let mut buf = [0u8; 34];
        let mut cipher = Aes128Ctr64LEWriter::new(buf.as_mut_slice(), &key, &iv).unwrap();
        cipher.write_all(&plaintext).unwrap();

        assert_eq!(buf[..], ciphertext[..]);

        // CTR mode can be used with streaming messages
        let mut out_buf = [0u8; 34];
        let mut cipher = Aes128Ctr64LEWriter::new(out_buf.as_mut_slice(), &key, &iv).unwrap();
        for chunk in buf.chunks_mut(3) {
            cipher.write_all(chunk).unwrap();
        }
        assert_eq!(out_buf[..], plaintext[..]);
    }

    struct ShortWriter<W> {
        inner: W,
        limit: usize,
    }

    impl<W> ShortWriter<W> {
        fn new(inner: W, limit: usize) -> Self {
            Self { inner, limit }
        }

        fn into_inner(self) -> W {
            self.inner
        }
    }

    impl<W> Write for ShortWriter<W>
    where
        W: Write,
    {
        fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
            if buf.is_empty() {
                return Ok(0);
            }
            let written = buf.len().min(self.limit.max(1));
            self.inner.write(&buf[..written])
        }

        fn flush(&mut self) -> io::Result<()> {
            self.inner.flush()
        }
    }

    #[test]
    fn write_handles_short_writes() {
        let key = [0x42u8; 16];
        let iv = [0x24u8; 16];
        let plaintext = *b"hello world! this is my plaintext.";
        let ciphertext = [
            51, 87, 18, 30, 187, 90, 41, 70, 139, 216, 97, 70, 117, 150, 206, 61, 165, 155, 222,
            228, 45, 204, 6, 20, 222, 169, 85, 54, 141, 138, 93, 192, 202, 212,
        ];

        let writer = ShortWriter::new(Vec::new(), 5);
        let mut cipher = Aes128Ctr64LEWriter::new(writer, &key, &iv).unwrap();
        cipher.write_all(&plaintext).unwrap();
        let writer = cipher.finish().unwrap();
        assert_eq!(writer.into_inner(), ciphertext);
    }
}