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Cap maximum response length from KDC #48572

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Cap maximum response length from KDC #48572

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13 changes: 13 additions & 0 deletions lib/srv/desktop/rdp/rdpclient/src/network_client.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,11 @@ impl NetworkClient {

const DEFAULT_KERBEROS_PORT: u16 = 88;

// Maximum response size from KDC we accept, Windows uses maximum token size of 48kB and recommends
// not to exceed 64kB
// https://learn.microsoft.com/en-us/troubleshoot/windows-server/windows-security/kerberos-authentication-problems-if-user-belongs-to-groups#calculating-the-maximum-token-size
const MAX_RESPONSE_LENGTH: u32 = 65535;

impl NetworkClient {
async fn send_tcp(&self, url: &Url, data: &[u8]) -> ConnectorResult<Vec<u8>> {
let addr = format!(
Expand All @@ -77,6 +82,14 @@ impl NetworkClient {
reason_err!("NLA", "reading data from Key Distribution Center failed")
})?;

if len > MAX_RESPONSE_LENGTH {
error!("KDC response too large: {} > {}", len, MAX_RESPONSE_LENGTH);
return Err(reason_err!(
"NLA",
"response from Key Distribution Center was too large"
));
}

let mut buf = vec![0; len as usize + 4];
buf[0..4].copy_from_slice(&(len.to_be_bytes()));

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