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Pin the readout frame bound with a deterministic envelope (nonce width varies the frame)

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Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
Meta Vens 2026-10-29 19:25:36 +01:00
commit 167bca6673
1 changed files with 21 additions and 11 deletions
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32
crates/model-connector/src/service.rs
View file

@ -679,7 +679,7 @@ impl TransportService {
&readout,
&asker.security,
)?;
if encode_spend_readout_response_frame(&sealed)?.len() > max_frame_bytes {
if !readout_fits_frame(&sealed, max_frame_bytes)? {
return Err(ServiceError::FrameBound);
}
Ok(sealed)
@ -1085,6 +1085,14 @@ fn fits_frame(envelope: &TransportEnvelope, max_frame_bytes: usize) -> Result<bo
encode_result_frame(envelope).map(|bytes| bytes.len() <= max_frame_bytes)
}
/// `fits_frame` for the frame a spend readout answer travels in.
fn readout_fits_frame(
envelope: &TransportEnvelope,
max_frame_bytes: usize,
) -> Result<bool, ServiceError> {
encode_spend_readout_response_frame(envelope).map(|bytes| bytes.len() <= max_frame_bytes)
}
/// The provider named on the stand-in failure, fixed so its size is bounded.
const STAND_IN_PROVIDER: &str = "model-connector";
@ -1838,6 +1846,17 @@ mod tests {
assert_eq!(fits_frame(&envelope, size - 1), Ok(false));
}
#[test]
fn a_readout_frame_check_is_inclusive_of_the_serialized_envelope() {
let readout = SpendReadout::new(1, Vec::new(), PlanQuotaSnapshot::default());
let envelope = encrypt_spend_readout(CALLER, "sized", &readout, &security(KEY)).unwrap();
let size = encode_spend_readout_response_frame(&envelope)
.unwrap()
.len();
assert_eq!(readout_fits_frame(&envelope, size), Ok(true));
assert_eq!(readout_fits_frame(&envelope, size - 1), Ok(false));
}
fn claim_for(
service: &mut TransportService,
request_id: &str,
@ -3837,19 +3856,10 @@ mod tests {
fn a_readout_that_cannot_fit_the_frame_is_a_frame_bound_failure() {
let store = TestStore::new();
let service = open_service(&store, 4);
let asked = encrypt_spend_readout_request(CALLER, "readout-1", &security(KEY)).unwrap();
let answer = service
.spend_readout(&asked, 1_000, PlanQuotaSnapshot::default(), FRAME)
.unwrap();
let exact = encode_spend_readout_response_frame(&answer).unwrap().len();
assert!(readout_as(&service, CALLER, KEY, 1_000, exact).is_ok());
assert_eq!(
readout_as(&service, CALLER, KEY, 1_000, exact - 1).unwrap_err(),
ServiceError::FrameBound
);
assert_eq!(
readout_as(&service, CALLER, KEY, 1_000, 64).unwrap_err(),
ServiceError::FrameBound
);
assert!(readout_as(&service, CALLER, KEY, 1_000, FRAME).is_ok());
}
}