rustls/crypto/cipher/
messages.rs

1use alloc::vec::Vec;
2use core::fmt;
3use core::ops::{Deref, DerefMut, Range};
4
5use crate::crypto::cipher::EncryptionState;
6use crate::enums::{ContentType, ProtocolVersion};
7use crate::error::{Error, InvalidMessage, PeerMisbehaved};
8use crate::msgs::{Codec, HEADER_SIZE, MAX_FRAGMENT_LEN, Reader, hex, read_opaque_message_header};
9
10/// A TLS message with encoded (but not necessarily encrypted) payload.
11#[expect(clippy::exhaustive_structs)]
12#[derive(Clone, Debug)]
13pub struct EncodedMessage<P> {
14    /// The content type of this message.
15    pub typ: ContentType,
16    /// The protocol version of this message.
17    pub version: ProtocolVersion,
18    /// The payload of this message.
19    pub payload: P,
20}
21
22impl<P> EncodedMessage<P> {
23    /// Create a new `EncodedMessage` with the given fields.
24    pub fn new(typ: ContentType, version: ProtocolVersion, payload: P) -> Self {
25        Self {
26            typ,
27            version,
28            payload,
29        }
30    }
31}
32
33impl<'a> EncodedMessage<Payload<'a>> {
34    /// Construct by decoding from a [`Reader`].
35    ///
36    /// `MessageError` allows callers to distinguish between valid prefixes (might
37    /// become valid if we read more data) and invalid data.
38    pub(crate) fn read(r: &mut Reader<'a>) -> Result<Self, MessageError> {
39        let (typ, version, len) = read_opaque_message_header(r)?;
40
41        let content = r
42            .take(len as usize)
43            .ok_or(MessageError::TooShortForLength)?;
44
45        Ok(Self {
46            typ,
47            version,
48            payload: Payload::Borrowed(content),
49        })
50    }
51
52    /// Convert into an unencrypted [`EncodedMessage<OutboundOpaque>`] (without decrypting).
53    pub fn into_unencrypted_opaque(self) -> EncodedMessage<OutboundOpaque> {
54        EncodedMessage {
55            typ: self.typ,
56            version: self.version,
57            payload: OutboundOpaque::from(self.payload.bytes()),
58        }
59    }
60
61    /// Borrow as an [`EncodedMessage<OutboundPlain<'a>>`].
62    pub fn borrow_outbound(&'a self) -> EncodedMessage<OutboundPlain<'a>> {
63        EncodedMessage {
64            typ: self.typ,
65            version: self.version,
66            payload: self.payload.bytes().into(),
67        }
68    }
69
70    /// Convert into an owned `EncodedMessage<Plain<'static>>`.
71    pub fn into_owned(self) -> Self {
72        Self {
73            typ: self.typ,
74            version: self.version,
75            payload: self.payload.into_owned(),
76        }
77    }
78}
79
80impl EncodedMessage<&'_ [u8]> {
81    /// Returns true if the payload is a CCS message.
82    ///
83    /// We passthrough ChangeCipherSpec messages in the deframer without decrypting them.
84    /// Note: this is prior to the record layer, so is unencrypted. See
85    /// third paragraph of section 5 in RFC8446.
86    pub(crate) fn is_valid_ccs(&self) -> bool {
87        self.typ == ContentType::ChangeCipherSpec && self.payload == [0x01]
88    }
89}
90
91impl<'a> EncodedMessage<InboundOpaque<'a>> {
92    /// For TLS1.3 (only), checks the length msg.payload is valid and removes the padding.
93    ///
94    /// Returns an error if the message (pre-unpadding) is too long, or the padding is invalid,
95    /// or the message (post-unpadding) is too long.
96    pub fn into_tls13_unpadded_message(mut self) -> Result<EncodedMessage<&'a [u8]>, Error> {
97        let payload = &mut self.payload;
98
99        if payload.len() > MAX_FRAGMENT_LEN + 1 {
100            return Err(Error::PeerSentOversizedRecord);
101        }
102
103        self.typ = unpad_tls13_payload(payload);
104        if self.typ == ContentType::Unknown(0) {
105            return Err(PeerMisbehaved::IllegalTlsInnerPlaintext.into());
106        }
107
108        if payload.len() > MAX_FRAGMENT_LEN {
109            return Err(Error::PeerSentOversizedRecord);
110        }
111
112        self.version = ProtocolVersion::TLSv1_3;
113        Ok(self.into_plain_message())
114    }
115
116    /// Force conversion into a plaintext message.
117    ///
118    /// `range` restricts the resulting message: this function panics if it is out of range for
119    /// the underlying message payload.
120    ///
121    /// This should only be used for messages that are known to be in plaintext. Otherwise, the
122    /// [`EncodedMessage<InboundOpaque<'_>>`] should be decrypted into an
123    /// `EncodedMessage<&'_ [u8]>` using a `MessageDecrypter`.
124    pub fn into_plain_message_range(self, range: Range<usize>) -> EncodedMessage<&'a [u8]> {
125        EncodedMessage {
126            typ: self.typ,
127            version: self.version,
128            payload: &self.payload.into_inner()[range],
129        }
130    }
131
132    /// Force conversion into a plaintext message.
133    ///
134    /// This should only be used for messages that are known to be in plaintext. Otherwise, the
135    /// [`EncodedMessage<InboundOpaque<'a>>`] should be decrypted into a
136    /// `EncodedMessage<&'a [u8]>` using a `MessageDecrypter`.
137    pub fn into_plain_message(self) -> EncodedMessage<&'a [u8]> {
138        EncodedMessage {
139            typ: self.typ,
140            version: self.version,
141            payload: self.payload.into_inner(),
142        }
143    }
144}
145
146impl EncodedMessage<OutboundPlain<'_>> {
147    pub(crate) fn to_unencrypted_opaque(&self) -> EncodedMessage<OutboundOpaque> {
148        let mut payload = OutboundOpaque::with_capacity(self.payload.len());
149        payload.extend_from_chunks(&self.payload);
150        EncodedMessage {
151            typ: self.typ,
152            version: self.version,
153            payload,
154        }
155    }
156
157    pub(crate) fn encoded_len(&self, record_layer: &EncryptionState) -> usize {
158        HEADER_SIZE + record_layer.encrypted_len(self.payload.len())
159    }
160}
161
162impl EncodedMessage<OutboundOpaque> {
163    /// Encode this message to a vector of bytes.
164    pub fn encode(self) -> Vec<u8> {
165        let length = self.payload.len() as u16;
166        let mut encoded_payload = self.payload.0;
167        encoded_payload[0] = self.typ.into();
168        encoded_payload[1..3].copy_from_slice(&self.version.to_array());
169        encoded_payload[3..5].copy_from_slice(&(length).to_be_bytes());
170        encoded_payload
171    }
172}
173
174/// A collection of borrowed plaintext slices.
175///
176/// Warning: OutboundChunks does not guarantee that the simplest variant is used.
177/// Multiple can hold non fragmented or empty payloads.
178#[non_exhaustive]
179#[derive(Debug, Clone)]
180pub enum OutboundPlain<'a> {
181    /// A single byte slice.
182    ///
183    /// Contrary to `Multiple`, this uses a single pointer indirection
184    Single(&'a [u8]),
185    /// A collection of chunks (byte slices).
186    Multiple {
187        /// A collection of byte slices that hold the buffered data.
188        chunks: &'a [&'a [u8]],
189        /// The start cursor into the first chunk.
190        start: usize,
191        /// The end cursor into the last chunk.
192        end: usize,
193    },
194}
195
196impl<'a> OutboundPlain<'a> {
197    /// Create a payload from a slice of byte slices.
198    /// If fragmented the cursors are added by default: start = 0, end = length
199    pub fn new(chunks: &'a [&'a [u8]]) -> Self {
200        if chunks.len() == 1 {
201            Self::Single(chunks[0])
202        } else {
203            Self::Multiple {
204                chunks,
205                start: 0,
206                end: chunks
207                    .iter()
208                    .map(|chunk| chunk.len())
209                    .sum(),
210            }
211        }
212    }
213
214    /// Create a payload with a single empty slice
215    pub fn new_empty() -> Self {
216        Self::Single(&[])
217    }
218
219    /// Flatten the slice of byte slices to an owned vector of bytes
220    pub fn to_vec(&self) -> Vec<u8> {
221        let mut vec = Vec::with_capacity(self.len());
222        self.copy_to_vec(&mut vec);
223        vec
224    }
225
226    /// Append all bytes to a vector
227    pub fn copy_to_vec(&self, vec: &mut Vec<u8>) {
228        match *self {
229            Self::Single(chunk) => vec.extend_from_slice(chunk),
230            Self::Multiple { chunks, start, end } => {
231                let mut size = 0;
232                for chunk in chunks.iter() {
233                    let psize = size;
234                    let len = chunk.len();
235                    size += len;
236                    if size <= start || psize >= end {
237                        continue;
238                    }
239                    let start = start.saturating_sub(psize);
240                    let end = if end - psize < len { end - psize } else { len };
241                    vec.extend_from_slice(&chunk[start..end]);
242                }
243            }
244        }
245    }
246
247    /// Split self in two, around an index
248    /// Works similarly to `split_at` in the core library, except it doesn't panic if out of bound
249    pub(crate) fn split_at(&self, mid: usize) -> (Self, Self) {
250        match *self {
251            Self::Single(chunk) => {
252                let mid = Ord::min(mid, chunk.len());
253                (Self::Single(&chunk[..mid]), Self::Single(&chunk[mid..]))
254            }
255            Self::Multiple { chunks, start, end } => {
256                let mid = Ord::min(start + mid, end);
257                (
258                    Self::Multiple {
259                        chunks,
260                        start,
261                        end: mid,
262                    },
263                    Self::Multiple {
264                        chunks,
265                        start: mid,
266                        end,
267                    },
268                )
269            }
270        }
271    }
272
273    /// Returns true if the payload is empty
274    pub(crate) fn is_empty(&self) -> bool {
275        self.len() == 0
276    }
277
278    /// Returns the cumulative length of all chunks
279    #[expect(clippy::len_without_is_empty)]
280    pub fn len(&self) -> usize {
281        match self {
282            Self::Single(chunk) => chunk.len(),
283            Self::Multiple { start, end, .. } => end - start,
284        }
285    }
286}
287
288impl<'a> From<&'a [u8]> for OutboundPlain<'a> {
289    fn from(payload: &'a [u8]) -> Self {
290        Self::Single(payload)
291    }
292}
293
294/// A payload buffer with space reserved at the front for a TLS message header.
295///
296/// `EncodedMessage<OutboundOpaque>` is named `TLSPlaintext` in the standard.
297///
298/// This outbound type owns all memory for its interior parts.
299/// It results from encryption and is used for io write.
300#[derive(Clone, Debug)]
301pub struct OutboundOpaque(Vec<u8>);
302
303impl OutboundOpaque {
304    /// Create a new value with the given payload capacity.
305    ///
306    /// (The actual capacity of the returned value will be at least `HEADER_SIZE + capacity`.)
307    pub fn with_capacity(capacity: usize) -> Self {
308        let mut prefixed_payload = Vec::with_capacity(HEADER_SIZE + capacity);
309        prefixed_payload.resize(HEADER_SIZE, 0);
310        Self(prefixed_payload)
311    }
312
313    /// Append bytes from a slice.
314    pub fn extend_from_slice(&mut self, slice: &[u8]) {
315        self.0.extend_from_slice(slice)
316    }
317
318    /// Append bytes from an `OutboundChunks`.
319    pub fn extend_from_chunks(&mut self, chunks: &OutboundPlain<'_>) {
320        chunks.copy_to_vec(&mut self.0)
321    }
322
323    /// Truncate the payload to the given length (plus header).
324    pub fn truncate(&mut self, len: usize) {
325        self.0.truncate(len + HEADER_SIZE)
326    }
327
328    fn len(&self) -> usize {
329        self.0.len() - HEADER_SIZE
330    }
331}
332
333impl AsRef<[u8]> for OutboundOpaque {
334    fn as_ref(&self) -> &[u8] {
335        &self.0[HEADER_SIZE..]
336    }
337}
338
339impl AsMut<[u8]> for OutboundOpaque {
340    fn as_mut(&mut self) -> &mut [u8] {
341        &mut self.0[HEADER_SIZE..]
342    }
343}
344
345impl<'a> Extend<&'a u8> for OutboundOpaque {
346    fn extend<T: IntoIterator<Item = &'a u8>>(&mut self, iter: T) {
347        self.0.extend(iter)
348    }
349}
350
351impl From<&[u8]> for OutboundOpaque {
352    fn from(content: &[u8]) -> Self {
353        let mut payload = Vec::with_capacity(HEADER_SIZE + content.len());
354        payload.extend(&[0u8; HEADER_SIZE]);
355        payload.extend(content);
356        Self(payload)
357    }
358}
359
360impl<const N: usize> From<&[u8; N]> for OutboundOpaque {
361    fn from(content: &[u8; N]) -> Self {
362        Self::from(&content[..])
363    }
364}
365
366/// An externally length'd payload
367///
368/// When encountered in an [`EncodedMessage`], it represents a plaintext payload. It can be
369/// decrypted from an [`InboundOpaque`] or encrypted into an [`OutboundOpaque`],
370/// and it is also used for joining and fragmenting.
371#[non_exhaustive]
372#[derive(Clone, Eq, PartialEq)]
373pub enum Payload<'a> {
374    /// Borrowed payload
375    Borrowed(&'a [u8]),
376    /// Owned payload
377    Owned(Vec<u8>),
378}
379
380impl<'a> Payload<'a> {
381    /// A reference to the payload's bytes
382    pub fn bytes(&'a self) -> &'a [u8] {
383        match self {
384            Self::Borrowed(bytes) => bytes,
385            Self::Owned(bytes) => bytes,
386        }
387    }
388
389    pub(crate) fn into_owned(self) -> Payload<'static> {
390        Payload::Owned(self.into_vec())
391    }
392
393    pub(crate) fn into_vec(self) -> Vec<u8> {
394        match self {
395            Self::Borrowed(bytes) => bytes.to_vec(),
396            Self::Owned(bytes) => bytes,
397        }
398    }
399
400    pub(crate) fn read(r: &mut Reader<'a>) -> Self {
401        Self::Borrowed(r.rest())
402    }
403}
404
405impl Payload<'static> {
406    /// Create a new owned payload from the given `bytes`.
407    pub fn new(bytes: impl Into<Vec<u8>>) -> Self {
408        Self::Owned(bytes.into())
409    }
410}
411
412impl<'a> Codec<'a> for Payload<'a> {
413    fn encode(&self, bytes: &mut Vec<u8>) {
414        bytes.extend_from_slice(self.bytes());
415    }
416
417    fn read(r: &mut Reader<'a>) -> Result<Self, InvalidMessage> {
418        Ok(Self::read(r))
419    }
420}
421
422impl fmt::Debug for Payload<'_> {
423    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
424        hex(f, self.bytes())
425    }
426}
427
428/// A borrowed payload buffer.
429#[expect(clippy::exhaustive_structs)]
430pub struct InboundOpaque<'a>(pub &'a mut [u8]);
431
432impl<'a> InboundOpaque<'a> {
433    /// Truncate the payload to `len` bytes.
434    pub fn truncate(&mut self, len: usize) {
435        if len >= self.len() {
436            return;
437        }
438
439        self.0 = core::mem::take(&mut self.0)
440            .split_at_mut(len)
441            .0;
442    }
443
444    pub(crate) fn into_inner(self) -> &'a mut [u8] {
445        self.0
446    }
447
448    pub(crate) fn pop(&mut self) -> Option<u8> {
449        if self.is_empty() {
450            return None;
451        }
452
453        let len = self.len();
454        let last = self[len - 1];
455        self.truncate(len - 1);
456        Some(last)
457    }
458}
459
460impl Deref for InboundOpaque<'_> {
461    type Target = [u8];
462
463    fn deref(&self) -> &Self::Target {
464        self.0
465    }
466}
467
468impl DerefMut for InboundOpaque<'_> {
469    fn deref_mut(&mut self) -> &mut Self::Target {
470        self.0
471    }
472}
473
474/// Decode a TLS1.3 `TLSInnerPlaintext` encoding.
475///
476/// `p` is a message payload, immediately post-decryption.  This function
477/// removes zero padding bytes, until a non-zero byte is encountered which is
478/// the content type, which is returned.  See RFC8446 s5.2.
479///
480/// ContentType(0) is returned if the message payload is empty or all zeroes.
481fn unpad_tls13_payload(p: &mut InboundOpaque<'_>) -> ContentType {
482    loop {
483        match p.pop() {
484            Some(0) => {}
485            Some(content_type) => return ContentType::from(content_type),
486            None => return ContentType::Unknown(0),
487        }
488    }
489}
490
491/// Errors from trying to parse a TLS message.
492#[expect(missing_docs)]
493#[non_exhaustive]
494#[derive(Debug)]
495pub enum MessageError {
496    TooShortForHeader,
497    TooShortForLength,
498    InvalidEmptyPayload,
499    MessageTooLarge,
500    InvalidContentType,
501    UnknownProtocolVersion,
502}
503
504#[cfg(test)]
505mod tests {
506    use std::{println, vec};
507
508    use super::*;
509
510    #[test]
511    fn split_at_with_single_slice() {
512        let owner: &[u8] = &[0, 1, 2, 3, 4, 5, 6, 7];
513        let borrowed_payload = OutboundPlain::Single(owner);
514
515        let (before, after) = borrowed_payload.split_at(6);
516        println!("before:{before:?}\nafter:{after:?}");
517        assert_eq!(before.to_vec(), &[0, 1, 2, 3, 4, 5]);
518        assert_eq!(after.to_vec(), &[6, 7]);
519    }
520
521    #[test]
522    fn split_at_with_multiple_slices() {
523        let owner: Vec<&[u8]> = vec![&[0, 1, 2, 3], &[4, 5], &[6, 7, 8], &[9, 10, 11, 12]];
524        let borrowed_payload = OutboundPlain::new(&owner);
525
526        let (before, after) = borrowed_payload.split_at(3);
527        println!("before:{before:?}\nafter:{after:?}");
528        assert_eq!(before.to_vec(), &[0, 1, 2]);
529        assert_eq!(after.to_vec(), &[3, 4, 5, 6, 7, 8, 9, 10, 11, 12]);
530
531        let (before, after) = borrowed_payload.split_at(8);
532        println!("before:{before:?}\nafter:{after:?}");
533        assert_eq!(before.to_vec(), &[0, 1, 2, 3, 4, 5, 6, 7]);
534        assert_eq!(after.to_vec(), &[8, 9, 10, 11, 12]);
535
536        let (before, after) = borrowed_payload.split_at(11);
537        println!("before:{before:?}\nafter:{after:?}");
538        assert_eq!(before.to_vec(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
539        assert_eq!(after.to_vec(), &[11, 12]);
540    }
541
542    #[test]
543    fn split_out_of_bounds() {
544        let owner: Vec<&[u8]> = vec![&[0, 1, 2, 3], &[4, 5], &[6, 7, 8], &[9, 10, 11, 12]];
545
546        let single_payload = OutboundPlain::Single(owner[0]);
547        let (before, after) = single_payload.split_at(17);
548        println!("before:{before:?}\nafter:{after:?}");
549        assert_eq!(before.to_vec(), &[0, 1, 2, 3]);
550        assert!(after.is_empty());
551
552        let multiple_payload = OutboundPlain::new(&owner);
553        let (before, after) = multiple_payload.split_at(17);
554        println!("before:{before:?}\nafter:{after:?}");
555        assert_eq!(before.to_vec(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]);
556        assert!(after.is_empty());
557
558        let empty_payload = OutboundPlain::new_empty();
559        let (before, after) = empty_payload.split_at(17);
560        println!("before:{before:?}\nafter:{after:?}");
561        assert!(before.is_empty());
562        assert!(after.is_empty());
563    }
564
565    #[test]
566    fn empty_slices_mixed() {
567        let owner: Vec<&[u8]> = vec![&[], &[], &[0], &[], &[1, 2], &[], &[3], &[4], &[], &[]];
568        let mut borrowed_payload = OutboundPlain::new(&owner);
569        let mut fragment_count = 0;
570        let mut fragment;
571        let expected_fragments: &[&[u8]] = &[&[0, 1], &[2, 3], &[4]];
572
573        while !borrowed_payload.is_empty() {
574            (fragment, borrowed_payload) = borrowed_payload.split_at(2);
575            println!("{fragment:?}");
576            assert_eq!(&expected_fragments[fragment_count], &fragment.to_vec());
577            fragment_count += 1;
578        }
579        assert_eq!(fragment_count, expected_fragments.len());
580    }
581
582    #[test]
583    fn exhaustive_splitting() {
584        let owner: Vec<u8> = (0..127).collect();
585        let slices = (0..7)
586            .map(|i| &owner[((1 << i) - 1)..((1 << (i + 1)) - 1)])
587            .collect::<Vec<_>>();
588        let payload = OutboundPlain::new(&slices);
589
590        assert_eq!(payload.to_vec(), owner);
591        println!("{payload:#?}");
592
593        for start in 0..128 {
594            for end in start..128 {
595                for mid in 0..(end - start) {
596                    let witness = owner[start..end].split_at(mid);
597                    let split_payload = payload
598                        .split_at(end)
599                        .0
600                        .split_at(start)
601                        .1
602                        .split_at(mid);
603                    assert_eq!(
604                        witness.0,
605                        split_payload.0.to_vec(),
606                        "start: {start}, mid:{mid}, end:{end}"
607                    );
608                    assert_eq!(
609                        witness.1,
610                        split_payload.1.to_vec(),
611                        "start: {start}, mid:{mid}, end:{end}"
612                    );
613                }
614            }
615        }
616    }
617}
rustls/crypto/cipher/messages.rs

rustls/crypto/cipher/
messages.rs
