ytls_extensions/
alpns.rs

1//! yTLS Extension (51) Key Share
2//! https://datatracker.ietf.org/doc/html/draft-ietf-tls-rfc8446bis-14#section-4.2.8
3
4use crate::TlsExtError;
5use ytls_typed::Alpn;
6
7/// Downstream Key Share Processor
8pub trait ExtAlpnProcessor {
9    fn alpn<'r>(&mut self, _: Alpn<'r>) -> bool;
10}
11
12/// TLS Extension 51 Key Share handling
13pub struct TlsExtAlpn {}
14
15impl TlsExtAlpn {
16    #[inline]
17    pub fn client_alpn_cb<P: ExtAlpnProcessor>(
18        p: &mut P,
19        alpn_raw: &[u8],
20    ) -> Result<(), TlsExtError> {
21        if alpn_raw.len() < 2 {
22            return Err(TlsExtError::InvalidLength);
23        }
24
25        let alpns_expected_len = u16::from_be_bytes([alpn_raw[0], alpn_raw[1]]);
26
27        let alpns_raw_len_remaining = alpn_raw.len() - 2;
28
29        if alpns_raw_len_remaining == 0 {
30            return Err(TlsExtError::NoData);
31        }
32
33        if alpns_expected_len as usize != alpns_raw_len_remaining {
34            return Err(TlsExtError::InvalidLength);
35        }
36
37        let mut remaining = &alpn_raw[2..];
38
39        let expected_len: usize = remaining.len();
40
41        let mut processed: usize = 0;
42
43        loop {
44            if remaining.len() < 2 {
45                return Err(TlsExtError::InvalidLength);
46            }
47            let alpn_len = remaining[0] as usize;
48
49            remaining = &remaining[1..];
50            processed += 1;
51
52            if alpn_len > remaining.len() {
53                return Err(TlsExtError::EntryOverflow);
54            }
55
56            let (alpn, remaining_next) = remaining.split_at(alpn_len as usize);
57            processed += alpn_len as usize;
58
59            p.alpn(alpn.into());
60
61            remaining = remaining_next;
62
63            if processed > expected_len {
64                return Err(TlsExtError::EntryOverflow);
65            }
66
67            if remaining.len() == 0 {
68                break;
69            }
70        }
71
72        Ok(())
73    }
74}
ytls_extensions/alpns.rs

ytls_extensions/
alpns.rs
