Add a ChaChaReader adapter to read an encrypted stream & use it

[rust-lightning] / lightning / src / util / chacha20.rs

diff --git a/lightning/src/util/chacha20.rs b/lightning/src/util/chacha20.rs
index c96577da02c4a31ec1a3827b0ac38d9003e1a831..09e9a847598e10d51071ab1e3aa2d805d1f15860 100644 (file)
--- a/lightning/src/util/chacha20.rs
+++ b/lightning/src/util/chacha20.rs
@@ -9,6 +9,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::io;
+
 #[cfg(not(feature = "fuzztarget"))]
 mod real_chacha {
        use std::cmp;
@@ -249,6 +251,29 @@ mod real_chacha {
                                self.offset += count;
                        }
                }
+
+               pub fn process_in_place(&mut self, input_output: &mut [u8]) {
+                       let len = input_output.len();
+                       let mut i = 0;
+                       while i < len {
+                               // If there is no keystream available in the output buffer,
+                               // generate the next block.
+                               if self.offset == 64 {
+                                       self.update();
+                               }
+
+                               // Process the min(available keystream, remaining input length).
+                               let count = cmp::min(64 - self.offset, len - i);
+                               // explicitly assert lengths to avoid bounds checks:
+                               assert!(input_output.len() >= i + count);
+                               assert!(self.output.len() >= self.offset + count);
+                               for j in 0..count {
+                                       input_output[i + j] ^= self.output[self.offset + j];
+                               }
+                               i += count;
+                               self.offset += count;
+                       }
+               }
        }
 }
 #[cfg(not(feature = "fuzztarget"))]
@@ -268,11 +293,27 @@ mod fuzzy_chacha {
                pub fn process(&mut self, input: &[u8], output: &mut [u8]) {
                        output.copy_from_slice(input);
                }
+
+               pub fn process_in_place(&mut self, _input_output: &mut [u8]) {}
        }
 }
 #[cfg(feature = "fuzztarget")]
 pub use self::fuzzy_chacha::ChaCha20;
 
+pub(crate) struct ChaChaReader<'a, R: io::Read> {
+       pub chacha: &'a mut ChaCha20,
+       pub read: R,
+}
+impl<'a, R: io::Read> io::Read for ChaChaReader<'a, R> {
+       fn read(&mut self, dest: &mut [u8]) -> Result<usize, io::Error> {
+               let res = self.read.read(dest)?;
+               if res > 0 {
+                       self.chacha.process_in_place(&mut dest[0..res]);
+               }
+               Ok(res)
+       }
+}
+
 #[cfg(test)]
 mod test {
        use std::iter::repeat;