Add specific errors for sealing failures

[nick-mobilecoin]

Add errors that provide more information on why a failure to seal data
occurs.

[nick-mobilecoin]

Current dependencies on/for this PR:

• main
  • PR (cargo-release) version 0.2.0 #158
    • PR (cargo-release) start next development iteration 0.2.1-pre #159
      • PR Only support sim in test_enclave #163
        • PR Add specific errors for sealing failures #164 👈
          • PR Add validation of data and aad values #165
            • PR Add PathInitializer to mc-sgx-dcap-ql #166
              • PR Add explicit errors for failures to set_path #171
                • PR mc-sgx-dcap-ql limits the enclave load policy to one call #173
                  • PR Add mc-sgx-dcap-quoteverify::PathInitializer #174
                  • PR Add LoadPolicyInitializer to mc-sgx-dcap-quoteverify #175

This comment was auto-generated by Graphite.

[nick-mobilecoin]

This initial change only updates the current error handling in sealing to use a seal specific error.
Subsequent commits will provide mirror parameter validation that sgx_seal_data_ex performs.

[NotGyro]

Looks good to me - I can see ways that it could be more specific, but having these broader categories of errors could be much easier to work with.

[jcape]

I think these errors are pointing in the wrong direction, unfortunately. The real issue that needs solving is "give the caller a more descriptive/fine-grained error code when the SDK would return something obtuse like INVALID_PARAMETER."

Like, INVALID_PARAMETER could mean "buffer not in enclave" or "buffer length too short" or "plaintext + mac length > u32::MAX" or any number of things, I'm saying you shouldn't have to read the SGX FFI PDF to figure that out, it should be immediately evident, even if that means duplicating the input validation that the SDK is doing in our rust code.

[codecov-commenter]

Codecov Report

Merging #164 (296ff6f) into main (428e87c) will decrease coverage by 0.51%.
The diff coverage is 56.66%.

@@            Coverage Diff             @@
##             main     #164      +/-   ##
==========================================
- Coverage   84.31%   83.79%   -0.52%     
==========================================
  Files          44       44              
  Lines        2397     2444      +47     
==========================================
+ Hits         2021     2048      +27     
- Misses        376      396      +20     

Impacted Files	Coverage Δ
tservice/src/seal.rs	52.54% <56.66%> (+1.77%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[jcape]

LGTM, some minor rewording of the Display format strings. For the logging case, it's generally prefered to keep them as a single sentence with no line breaks, due to how nested errors are displayed. e.g. an error hierarchy like:

FooError::Frobnicate(FrobnicateError::BlahBityBlah(BlahError::WastefulAlloc)

will end up getting printed as:

"Foo error while frobnicating: Frobincating requires blahbityblah: Blah is larger than necessary."

[nick-mobilecoin]

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Current status: ✅ Merged

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