X.509 Policy Constraints Double Locking

If an X.509 certificate contains a malformed policy constraint and

policy processing is enabled, then a write lock will be taken twice

recursively. On some operating systems (most widely: Windows) this

results in a denial of service when the affected process hangs. Policy

processing being enabled on a publicly facing server is not considered

to be a common setup.

Policy processing is enabled by passing the `-policy'

argument to the command line utilities or by calling the

`X509_VERIFY_PARAM_set1_policies()' function.

Update (31 March 2023): The description of the policy processing enablement

was corrected based on CVE-2023-0466.