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dtls13: stop creating malformed certificate_authorities extension #154

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dtls13: stop creating malformed certificate_authorities extension #154

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11 changes: 7 additions & 4 deletions src/dtls13/message/wrapped.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,13 +28,16 @@ macro_rules! wrapped_slice {

Ok((input, $name(start..end)))
}

pub fn as_slice<'a>(&self, buf: &'a [u8]) -> &'a [u8] {
&buf[self.0.clone()]
}
}
};
}

wrapped_slice!(Asn1Cert, be_u24, 0);
wrapped_slice!(DistinguishedName, be_u16, 1);

impl Asn1Cert {
/// Resolve this certificate's byte range within `buf`.
pub fn as_slice<'a>(&self, buf: &'a [u8]) -> &'a [u8] {
&buf[self.0.clone()]
}
}
29 changes: 2 additions & 27 deletions src/dtls13/server.rs
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Expand Up @@ -45,7 +45,6 @@ use crate::dtls13::engine::Engine;
use crate::dtls13::message::Body;
use crate::dtls13::message::CompressionMethod;
use crate::dtls13::message::ContentType;
use crate::dtls13::message::DistinguishedName;
use crate::dtls13::message::Dtls13CipherSuite;
use crate::dtls13::message::Extension;
use crate::dtls13::message::ExtensionType;
Expand Down Expand Up @@ -1460,15 +1459,8 @@ fn handshake_create_certificate_request(body: &mut Buf) -> Result<(), Error> {
extension_data_range: sa_start..sa_end,
});

// certificate_authorities extension (empty list)
let ca_start = ext_buf.len();
let cas: ArrayVec<DistinguishedName, 32> = ArrayVec::new();
serialize_certificate_authorities(&cas, &[], &mut ext_buf);
let ca_end = ext_buf.len();
extensions.push(Extension {
extension_type: ExtensionType::CertificateAuthorities,
extension_data_range: ca_start..ca_end,
});
// No certificate_authorities extension: it is optional, but if present, it
// must not be empty (RFC 8446 4.2.4).

// Calculate total extensions length
let mut extensions_len = 0usize;
Expand All @@ -1485,20 +1477,3 @@ fn handshake_create_certificate_request(body: &mut Buf) -> Result<(), Error> {

Ok(())
}

/// Serialize a list of DistinguishedNames for the certificate_authorities extension.
///
/// Format: DistinguishedName<3..2^16-1> (outer length + entries)
fn serialize_certificate_authorities(
cas: &ArrayVec<DistinguishedName, 32>,
buf: &[u8],
output: &mut Buf,
) {
let total_len: usize = cas.iter().map(|dn| 2 + dn.as_slice(buf).len()).sum();
output.extend_from_slice(&(total_len as u16).to_be_bytes());
for dn in cas {
let data = dn.as_slice(buf);
output.extend_from_slice(&(data.len() as u16).to_be_bytes());
output.extend_from_slice(data);
}
}
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