verify_cert: enforce maximum number of signatures. #152
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Codecov Report
@@ Coverage Diff @@
## main #152 +/- ##
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+ Coverage 96.46% 96.54% +0.08%
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Files 15 15
Lines 4304 4376 +72
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+ Hits 4152 4225 +73
+ Misses 152 151 -1
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Pathbuilding complexity can be quadratic, particularly when the set of intermediates all have subjects matching a trust anchor. In these cases we need to bound the number of expensive signature validation operations that are performed to avoid a DoS on CPU usage. This commit implements a simple maximum signature check limit inspired by the approach taken in the Golang x509 package. No more than 100 signatures will be evaluated while pathbuilding. This limit works in practice for Go when processing real world certificate chains and so should be appropriate for our use case as well.
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djc
approved these changes
Aug 21, 2023
This was referenced Aug 31, 2023
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Pathbuilding complexity can be quadratic, particularly when the set of intermediates all have subjects matching a trust anchor. In these cases we need to bound the number of expensive signature validation operations that are performed to avoid a DoS on CPU usage.
This commit implements a simple maximum signature check limit inspired by the approach taken in the Golang x509 package. No more than 100 signatures will be evaluated while pathbuilding. This limit works in practice for Go when processing real world certificate chains and so should be appropriate for our use case as well.
Without the limit in place, the
test_too_many_signaturesunit test has very long runtime and quickly pegs my local CPU. With the limit in place the test returns the expected error quickly.