rustls/msgs/message/
inbound.rs

1use core::ops::{Deref, DerefMut};
2
3use crate::enums::{ContentType, ProtocolVersion};
4use crate::error::{Error, PeerMisbehaved};
5use crate::msgs::fragmenter::MAX_FRAGMENT_LEN;
6
7/// A TLS frame, named TLSPlaintext in the standard.
8///
9/// This inbound type borrows its encrypted payload from a buffer elsewhere.
10/// It is used for joining and is consumed by decryption.
11pub struct InboundOpaqueMessage<'a> {
12    pub typ: ContentType,
13    pub version: ProtocolVersion,
14    pub payload: BorrowedPayload<'a>,
15}
16
17impl<'a> InboundOpaqueMessage<'a> {
18    /// Construct a new `InboundOpaqueMessage` from constituent fields.
19    ///
20    /// `payload` is borrowed.
21    pub fn new(typ: ContentType, version: ProtocolVersion, payload: &'a mut [u8]) -> Self {
22        Self {
23            typ,
24            version,
25            payload: BorrowedPayload(payload),
26        }
27    }
28
29    /// Force conversion into a plaintext message.
30    ///
31    /// This should only be used for messages that are known to be in plaintext. Otherwise, the
32    /// `InboundOpaqueMessage` should be decrypted into a `PlainMessage` using a `MessageDecrypter`.
33    pub fn into_plain_message(self) -> InboundPlainMessage<'a> {
34        InboundPlainMessage {
35            typ: self.typ,
36            version: self.version,
37            payload: self.payload.into_inner(),
38        }
39    }
40
41    /// For TLS1.3 (only), checks the length msg.payload is valid and removes the padding.
42    ///
43    /// Returns an error if the message (pre-unpadding) is too long, or the padding is invalid,
44    /// or the message (post-unpadding) is too long.
45    pub fn into_tls13_unpadded_message(mut self) -> Result<InboundPlainMessage<'a>, Error> {
46        let payload = &mut self.payload;
47
48        if payload.len() > MAX_FRAGMENT_LEN + 1 {
49            return Err(Error::PeerSentOversizedRecord);
50        }
51
52        self.typ = unpad_tls13_payload(payload);
53        if self.typ == ContentType::Unknown(0) {
54            return Err(PeerMisbehaved::IllegalTlsInnerPlaintext.into());
55        }
56
57        if payload.len() > MAX_FRAGMENT_LEN {
58            return Err(Error::PeerSentOversizedRecord);
59        }
60
61        self.version = ProtocolVersion::TLSv1_3;
62        Ok(self.into_plain_message())
63    }
64}
65
66pub struct BorrowedPayload<'a>(&'a mut [u8]);
67
68impl Deref for BorrowedPayload<'_> {
69    type Target = [u8];
70
71    fn deref(&self) -> &Self::Target {
72        self.0
73    }
74}
75
76impl<'a> DerefMut for BorrowedPayload<'a> {
77    fn deref_mut(&mut self) -> &mut Self::Target {
78        self.0
79    }
80}
81
82impl<'a> BorrowedPayload<'a> {
83    pub fn truncate(&mut self, len: usize) {
84        if len >= self.len() {
85            return;
86        }
87
88        self.0 = core::mem::take(&mut self.0)
89            .split_at_mut(len)
90            .0;
91    }
92
93    pub(crate) fn into_inner(self) -> &'a mut [u8] {
94        self.0
95    }
96
97    pub(crate) fn pop(&mut self) -> Option<u8> {
98        if self.is_empty() {
99            return None;
100        }
101
102        let len = self.len();
103        let last = self[len - 1];
104        self.truncate(len - 1);
105        Some(last)
106    }
107}
108
109/// A TLS frame, named `TLSPlaintext` in the standard.
110///
111/// This inbound type borrows its decrypted payload from the original buffer.
112/// It results from decryption.
113#[derive(Debug)]
114pub struct InboundPlainMessage<'a> {
115    pub typ: ContentType,
116    pub version: ProtocolVersion,
117    pub payload: &'a [u8],
118}
119
120impl InboundPlainMessage<'_> {
121    /// Returns true if the payload is a CCS message.
122    ///
123    /// We passthrough ChangeCipherSpec messages in the deframer without decrypting them.
124    /// Note: this is prior to the record layer, so is unencrypted. See
125    /// third paragraph of section 5 in RFC8446.
126    pub(crate) fn is_valid_ccs(&self) -> bool {
127        self.typ == ContentType::ChangeCipherSpec && self.payload == [0x01]
128    }
129}
130
131/// Decode a TLS1.3 `TLSInnerPlaintext` encoding.
132///
133/// `p` is a message payload, immediately post-decryption.  This function
134/// removes zero padding bytes, until a non-zero byte is encountered which is
135/// the content type, which is returned.  See RFC8446 s5.2.
136///
137/// ContentType(0) is returned if the message payload is empty or all zeroes.
138fn unpad_tls13_payload(p: &mut BorrowedPayload<'_>) -> ContentType {
139    loop {
140        match p.pop() {
141            Some(0) => {}
142            Some(content_type) => return ContentType::from(content_type),
143            None => return ContentType::Unknown(0),
144        }
145    }
146}
rustls/msgs/message/inbound.rs

rustls/msgs/message/
inbound.rs
