SE keys: fix psa_destroy_key; add Github issue numbers for missing code #221
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When a key slot is wiped, a copy of the key material may remain in operations. This is undesirable, but does not violate the safety of the code. Tracked in https://github.com/ARMmbed/mbed-crypto/issues/86
Adopt a simple method for tracking whether there was a failure: each fallible operation sets overall_status, unless overall_status is already non-successful. Thus in case of multiple failures, the function always reports whatever failed first. This may not always be the right thing, but it's simple. This revealed a bug whereby if the only failure was the call to psa_destroy_se_key(), i.e. if the driver reported a failure or if the driver lacked support for destroying keys, psa_destroy_key() would ignore that failure. For a key in a secure element, if creating a transaction file fails, don't touch storage, but close the key in memory. This may not be right, but it's no wronger than it was before. Tracked in ARMmbed#215
Drivers that allow destroying a key must have a destroy method. This test bug was previously not caught because of an implementation bug that lost the error triggered by the missing destroy method.
gilles-peskine-arm
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yanesca
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Aug 14, 2019
gilles-peskine-arm
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I went through FIXME/TODO comments in the code and added the corresponding issue numbers:
I also modified a comment relating to https://github.com/ARMmbed/mbed-crypto/issues/86 (not related to secure elements) but did not add an issue number because this is not exactly a bug and may even be resolved differently.
While doing this, I found two bugs in
psa_destroy_keywhich I fixed and added a test for (in one case, I actually fixed a test bug that was hidden by the implementation bug).I'm making this PR to
psa-api-1.0-betato be on top of the latest SE work. Once this PR is merged, we should do another merge frompsa-api-1.0-betafollowing #212.