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use alloc::vec::Vec;
use core::mem;
use core::ops::Range;
#[cfg(feature = "std")]
use std::io;
#[cfg(feature = "std")]
use crate::msgs::message::MAX_WIRE_SIZE;
/// Conversion from a slice within a larger buffer into
/// a `Range` offset within.
#[derive(Debug)]
pub(crate) struct Locator {
bounds: Range<*const u8>,
}
impl Locator {
#[inline]
pub(crate) fn new(slice: &[u8]) -> Self {
Self {
bounds: slice.as_ptr_range(),
}
}
#[inline]
pub(crate) fn locate(&self, slice: &[u8]) -> Range<usize> {
let bounds = slice.as_ptr_range();
debug_assert!(self.fully_contains(slice));
let start = bounds.start as usize - self.bounds.start as usize;
let len = bounds.end as usize - bounds.start as usize;
Range {
start,
end: start + len,
}
}
#[inline]
pub(crate) fn fully_contains(&self, slice: &[u8]) -> bool {
let bounds = slice.as_ptr_range();
bounds.start >= self.bounds.start && bounds.end <= self.bounds.end
}
}
/// Conversion from a `Range` offset to the original slice.
pub(crate) struct Delocator<'b> {
slice: &'b [u8],
}
impl<'b> Delocator<'b> {
#[inline]
pub(crate) fn new(slice: &'b [u8]) -> Self {
Self { slice }
}
#[inline]
pub(crate) fn slice_from_range(&'_ self, range: &Range<usize>) -> &'b [u8] {
// safety: this unwrap is safe so long as `range` came from `locate()`
// for the same buffer
self.slice.get(range.clone()).unwrap()
}
#[inline]
pub(crate) fn locator(self) -> Locator {
Locator::new(self.slice)
}
}
/// Reordering the underlying buffer based on ranges.
pub(crate) struct Coalescer<'b> {
slice: &'b mut [u8],
}
impl<'b> Coalescer<'b> {
#[inline]
pub(crate) fn new(slice: &'b mut [u8]) -> Self {
Self { slice }
}
#[inline]
pub(crate) fn copy_within(&mut self, from: Range<usize>, to: Range<usize>) {
debug_assert!(from.len() == to.len());
debug_assert!(self.slice.get(from.clone()).is_some());
debug_assert!(self.slice.get(to.clone()).is_some());
self.slice.copy_within(from, to.start);
}
#[inline]
pub(crate) fn delocator(self) -> Delocator<'b> {
Delocator::new(self.slice)
}
}
/// Accounting structure tracking progress in parsing a single buffer.
#[derive(Clone, Debug, Default)]
pub(crate) struct BufferProgress {
/// Prefix of the buffer that has been processed so far.
///
/// `processed` may exceed `discard`, that means we have parsed
/// some buffer, but are still using it. This happens due to
/// in-place decryption of incoming records, and in-place
/// reassembly of handshake messages.
///
/// 0 <= processed <= len
processed: usize,
/// Prefix of the buffer that can be removed.
///
/// If `discard` exceeds `processed`, that means we are ignoring
/// data without processing it.
///
/// 0 <= discard <= len
discard: usize,
}
impl BufferProgress {
#[inline]
pub(crate) fn add_discard(&mut self, discard: usize) {
self.discard += discard;
}
#[inline]
pub(crate) fn add_processed(&mut self, processed: usize) {
self.processed += processed;
}
#[inline]
pub(crate) fn take_discard(&mut self) -> usize {
// the caller is about to discard `discard` bytes
// from the front of the buffer. adjust `processed`
// down by the same amount.
self.processed = self
.processed
.saturating_sub(self.discard);
mem::take(&mut self.discard)
}
#[inline]
pub(crate) fn processed(&self) -> usize {
self.processed
}
}
#[derive(Default, Debug)]
pub(crate) struct DeframerVecBuffer {
/// Buffer of data read from the socket, in the process of being parsed into messages.
///
/// For buffer size management, checkout out the [`DeframerVecBuffer::prepare_read()`] method.
buf: Vec<u8>,
/// What size prefix of `buf` is used.
used: usize,
pub(crate) processed: usize,
}
impl DeframerVecBuffer {
/// Discard `taken` bytes from the start of our buffer.
pub(crate) fn discard(&mut self, taken: usize) {
#[allow(clippy::comparison_chain)]
if taken < self.used {
/* Before:
* +----------+----------+----------+
* | taken | pending |xxxxxxxxxx|
* +----------+----------+----------+
* 0 ^ taken ^ self.used
*
* After:
* +----------+----------+----------+
* | pending |xxxxxxxxxxxxxxxxxxxxx|
* +----------+----------+----------+
* 0 ^ self.used
*/
self.buf
.copy_within(taken..self.used, 0);
self.used -= taken;
self.processed = self.processed.saturating_sub(taken);
} else if taken == self.used {
self.used = 0;
self.processed = 0;
}
}
pub(crate) fn filled_mut(&mut self) -> &mut [u8] {
&mut self.buf[..self.used]
}
pub(crate) fn filled(&self) -> &[u8] {
&self.buf[..self.used]
}
}
#[cfg(feature = "std")]
impl DeframerVecBuffer {
/// Read some bytes from `rd`, and add them to the buffer.
pub(crate) fn read(&mut self, rd: &mut dyn io::Read, in_handshake: bool) -> io::Result<usize> {
if let Err(err) = self.prepare_read(in_handshake) {
return Err(io::Error::new(io::ErrorKind::InvalidData, err));
}
// Try to do the largest reads possible. Note that if
// we get a message with a length field out of range here,
// we do a zero length read. That looks like an EOF to
// the next layer up, which is fine.
let new_bytes = rd.read(&mut self.buf[self.used..])?;
self.used += new_bytes;
Ok(new_bytes)
}
/// Resize the internal `buf` if necessary for reading more bytes.
fn prepare_read(&mut self, is_joining_hs: bool) -> Result<(), &'static str> {
/// TLS allows for handshake messages of up to 16MB. We
/// restrict that to 64KB to limit potential for denial-of-
/// service.
const MAX_HANDSHAKE_SIZE: u32 = 0xffff;
const READ_SIZE: usize = 4096;
// We allow a maximum of 64k of buffered data for handshake messages only. Enforce this
// by varying the maximum allowed buffer size here based on whether a prefix of a
// handshake payload is currently being buffered. Given that the first read of such a
// payload will only ever be 4k bytes, the next time we come around here we allow a
// larger buffer size. Once the large message and any following handshake messages in
// the same flight have been consumed, `pop()` will call `discard()` to reset `used`.
// At this point, the buffer resizing logic below should reduce the buffer size.
let allow_max = match is_joining_hs {
true => MAX_HANDSHAKE_SIZE as usize,
false => MAX_WIRE_SIZE,
};
if self.used >= allow_max {
return Err("message buffer full");
}
// If we can and need to increase the buffer size to allow a 4k read, do so. After
// dealing with a large handshake message (exceeding `OutboundOpaqueMessage::MAX_WIRE_SIZE`),
// make sure to reduce the buffer size again (large messages should be rare).
// Also, reduce the buffer size if there are neither full nor partial messages in it,
// which usually means that the other side suspended sending data.
let need_capacity = Ord::min(allow_max, self.used + READ_SIZE);
if need_capacity > self.buf.len() {
self.buf.resize(need_capacity, 0);
} else if self.used == 0 || self.buf.len() > allow_max {
self.buf.resize(need_capacity, 0);
self.buf.shrink_to(need_capacity);
}
Ok(())
}
/// Append `bytes` to the end of this buffer.
///
/// Return a `Range` saying where it went.
pub(crate) fn extend(&mut self, bytes: &[u8]) -> Range<usize> {
let len = bytes.len();
let start = self.used;
let end = start + len;
if self.buf.len() < end {
self.buf.resize(end, 0);
}
self.buf[start..end].copy_from_slice(bytes);
self.used += len;
Range { start, end }
}
}
/// A borrowed version of [`DeframerVecBuffer`] that tracks discard operations
#[derive(Debug)]
pub(crate) struct DeframerSliceBuffer<'a> {
// a fully initialized buffer that will be deframed
buf: &'a mut [u8],
// number of bytes to discard from the front of `buf` at a later time
discard: usize,
}
impl<'a> DeframerSliceBuffer<'a> {
pub(crate) fn new(buf: &'a mut [u8]) -> Self {
Self { buf, discard: 0 }
}
/// Tracks a pending discard operation of `num_bytes`
pub(crate) fn queue_discard(&mut self, num_bytes: usize) {
self.discard += num_bytes;
}
pub(crate) fn pending_discard(&self) -> usize {
self.discard
}
pub(crate) fn filled_mut(&mut self) -> &mut [u8] {
&mut self.buf[self.discard..]
}
}