Don't panic on bad nonce_size#2584
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jamesmunns
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Jul 2, 2026
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This LGTM, modulo one tiny style nit and one "made me look".
| // Ensure the requester didn't send a bad nonce_size that's | ||
| // larger than the actual blob. | ||
| let nonce_size = nonce_size as usize; | ||
| if nonce_size > req.blob.len() { |
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Tiny nit, I usually prefer something like:
let Some(nonce) = req.blob.get(..nonce_size) else {
return Err(SprotError::Protocol(
SprotProtocolError::BadMessageLength,
));
};
Ok((
RspBody::Attest(Ok(AttestRsp::Attest)),
Some(TrailingData::Attest { nonce, write_size }),
))which lets you do the "length check" and "subslice" in one step.
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I have also begun to find joy in let / else
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Yeah that's nicer!
| /// Unknown message | ||
| BadMessageType, | ||
| /// Transfer size is outside of maximum and minimum lenghts for message type. | ||
| /// Transfer size is outside of maximum and minimum lengths for message |
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I did go and check, we do check that the nonce is a valid size elsewhere (I think min and max are checked in different places?).
labbott
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Jul 2, 2026
| // Ensure the requester didn't send a bad nonce_size that's | ||
| // larger than the actual blob. | ||
| let nonce_size = nonce_size as usize; | ||
| if nonce_size > req.blob.len() { |
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I have also begun to find joy in let / else
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Before, the SP could cause the RoT to panic by sending it an
attestrequest with anonce_sizelarger than the actual blob of nonce data. Now the RoT replies with aBadMessageLengtherror instead.This is slightly different than the other uses of
BadMessageLength, but I don't think it's worth making a new error variant just for this case and plumbing it through MGS. Tell me if you disagree.Tested on a grapefruit.