SecurityEngineering/Removing Compatibility Workarounds in mozilla::pkix

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In the process of implementing mozilla::pkix, a number of compatibility issues were encountered involving certificates that did not conform to the Baseline Requirements. To maintain interoperability, some workarounds were added to allow these malformed or improper certificates to validate successfully. However, to improve the state of the web PKI, these workarounds will be removed. As of Firefox 49, if a certificate has a notBefore time after 0:00 23 August 2016 and is affected by any of these workarounds (see below), it will not validate successfully. This document will track the implementation work necessary to remove those workarounds.

Completed

  • use of subject CN for naming information (Firefox 48)
  • id-Netscape-stepUp in Extended Key Usage extension instead of id-kp-serverAuth (Firefox 49)

Ready to be Removed

  • DER: pathLenConstraint included when cA:False
    • Workaround introduced in bug 985021
    • Workaround to be removed in bug 985025
    • Code affected: CheckIssuerIndependentProperties -> CheckBasicConstraints (pkixcheck.cpp)
    • Expected difficulty: easy
  • nameConstraints/subjectAlternativeName encoding mismatches
    • Workaround introduced in bug 1150114
    • Workaround to be removed in bug 1256073
    • Code affected: pkixnames.cpp
    • Expected difficulty: moderate
  • keyUsage lacking keyEncipherment for certs with RSA keys
    • Workaround introduced in n/a
    • Workaround to be removed in bug 970760
    • See also bug 1133562
    • Code affected: CertVerifier.cpp
    • Expected difficulty: moderate

Potentially Ready to be Removed

  • empty SEQUENCE in OCSP responses
    • Workaround introduced in bug 991898
    • Workaround to be removed in bug 997994
    • Code affected: pkixocsp.cpp, pkixder.h
    • Expected difficulty: moderate

Not Ready to be Removed

  • DER: default value of OPTIONAL BOOLEAN explicitly encoded
    • Workaround introduced in bug 989516 for Basic Constraints (cA field)
    • Workaround introduced in bug 1060929 for Extension (critical field)
    • Workaround to be removed in bug 989518
    • Code affected: pkixcheck.cpp, pkixder.h, pkixcert.cpp, pkixocsp.cpp
    • Expected difficulty: difficult
  • Non-PrintableString/UTF8String in DNs
    • Workaround introduced in bug 1089104
    • Workaround to be removed in bug 1256071
    • Code affected: pkixnames.cpp
    • Expected difficulty: moderate
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