From 26a029d407be480d791972afb5975cf62c9360a6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Fri, 19 Apr 2024 02:47:55 +0200 Subject: Adding upstream version 124.0.1. Signed-off-by: Daniel Baumann --- security/ct/CTPolicyEnforcer.cpp | 277 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 277 insertions(+) create mode 100644 security/ct/CTPolicyEnforcer.cpp (limited to 'security/ct/CTPolicyEnforcer.cpp') diff --git a/security/ct/CTPolicyEnforcer.cpp b/security/ct/CTPolicyEnforcer.cpp new file mode 100644 index 0000000000..0cacb25da6 --- /dev/null +++ b/security/ct/CTPolicyEnforcer.cpp @@ -0,0 +1,277 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "CTPolicyEnforcer.h" + +#include +#include +#include + +namespace mozilla { +namespace ct { + +using namespace mozilla::pkix; + +// Returns the number of embedded SCTs required to be present on a +// certificate for Qualification Case #2 (embedded SCTs). +static size_t GetRequiredEmbeddedSctsCount( + size_t certLifetimeInFullCalendarMonths) { + // "there are Embedded SCTs from AT LEAST N+1 once or currently qualified + // logs, where N is the lifetime of the certificate in years (normally + // rounding up, but rounding down when up to 3 months over), and must be + // at least 1" + return 1 + (certLifetimeInFullCalendarMonths + 9) / 12; +} + +// Whether a valid embedded SCT is present in the list. +static bool HasValidEmbeddedSct(const VerifiedSCTList& verifiedScts) { + for (const VerifiedSCT& verifiedSct : verifiedScts) { + if (verifiedSct.status == VerifiedSCT::Status::Valid && + verifiedSct.origin == VerifiedSCT::Origin::Embedded) { + return true; + } + } + return false; +} + +// Whether a valid non-embedded SCT is present in the list. +static bool HasValidNonEmbeddedSct(const VerifiedSCTList& verifiedScts) { + for (const VerifiedSCT& verifiedSct : verifiedScts) { + if (verifiedSct.status == VerifiedSCT::Status::Valid && + (verifiedSct.origin == VerifiedSCT::Origin::TLSExtension || + verifiedSct.origin == VerifiedSCT::Origin::OCSPResponse)) { + return true; + } + } + return false; +} + +// Given a list of verified SCTs, counts the number of distinct CA-independent +// log operators running the CT logs that issued the SCTs which satisfy +// the provided boolean predicate. +template +void CountIndependentLogOperatorsForSelectedScts( + const VerifiedSCTList& verifiedScts, + const CTLogOperatorList& dependentOperators, size_t& count, + SelectFunc selected) { + CTLogOperatorList operatorIds; + for (const VerifiedSCT& verifiedSct : verifiedScts) { + CTLogOperatorId sctLogOperatorId = verifiedSct.logOperatorId; + // Check if |sctLogOperatorId| is CA-dependent. + bool isDependentOperator = false; + for (CTLogOperatorId dependentOperator : dependentOperators) { + if (sctLogOperatorId == dependentOperator) { + isDependentOperator = true; + break; + } + } + if (isDependentOperator || !selected(verifiedSct)) { + continue; + } + // Check if |sctLogOperatorId| is in |operatorIds|... + bool alreadyAdded = false; + for (CTLogOperatorId id : operatorIds) { + if (id == sctLogOperatorId) { + alreadyAdded = true; + break; + } + } + // ...and if not, add it. + if (!alreadyAdded) { + operatorIds.push_back(sctLogOperatorId); + } + } + count = operatorIds.size(); +} + +// Given a list of verified SCTs, counts the number of distinct CT logs +// that issued the SCTs that satisfy the |selected| predicate. +template +static void CountLogsForSelectedScts(const VerifiedSCTList& verifiedScts, + size_t& count, SelectFunc selected) { + // Keep pointers to log ids (of type Buffer) from |verifiedScts| to save on + // memory allocations. + std::vector logIds; + for (const VerifiedSCT& verifiedSct : verifiedScts) { + if (!selected(verifiedSct)) { + continue; + } + + const Buffer* sctLogId = &verifiedSct.sct.logId; + // Check if |sctLogId| points to data already in |logIds|... + bool alreadyAdded = false; + for (const Buffer* logId : logIds) { + if (*logId == *sctLogId) { + alreadyAdded = true; + break; + } + } + // ...and if not, add it. + if (!alreadyAdded) { + logIds.push_back(sctLogId); + } + } + count = logIds.size(); +} + +// Calculates the effective issuance time of connection's certificate using +// the SCTs present on the connection (we can't rely on notBefore validity +// field of the certificate since it can be backdated). +// Used to determine whether to accept SCTs issued by past qualified logs. +// The effective issuance time is defined as the earliest of all SCTs, +// rather than the latest of embedded SCTs, in order to give CAs the benefit +// of the doubt in the event a log is revoked in the midst of processing +// a precertificate and issuing the certificate. +// It is acceptable to ignore the origin of the SCTs because SCTs +// delivered via OCSP/TLS extension will cover the full certificate, +// which necessarily will exist only after the precertificate +// has been logged and the actual certificate issued. +static uint64_t GetEffectiveCertIssuanceTime( + const VerifiedSCTList& verifiedScts) { + uint64_t result = UINT64_MAX; + for (const VerifiedSCT& verifiedSct : verifiedScts) { + if (verifiedSct.status == VerifiedSCT::Status::Valid) { + result = std::min(result, verifiedSct.sct.timestamp); + } + } + return result; +} + +// Checks if the log that issued the given SCT is "once or currently qualified" +// (i.e. was qualified at the time of the certificate issuance). In addition, +// makes sure the SCT is before the disqualification. +static bool LogWasQualifiedForSct(const VerifiedSCT& verifiedSct, + uint64_t certIssuanceTime) { + if (verifiedSct.status == VerifiedSCT::Status::Valid) { + return true; + } + if (verifiedSct.status == VerifiedSCT::Status::ValidFromDisqualifiedLog) { + uint64_t logDisqualificationTime = verifiedSct.logDisqualificationTime; + return certIssuanceTime < logDisqualificationTime && + verifiedSct.sct.timestamp < logDisqualificationTime; + } + return false; +} + +// "A certificate is CT Qualified if it is presented with at least two SCTs +// from once or currently qualified logs run by a minimum of two entities +// independent of the CA and of each other." +// By the preexisting certificate exception provision (not currently +// implemented), certificates "are CT Qualified if they are presented with SCTs +// from once or currently qualified logs run by a minimum of one entity +// independent of the CA." +static void CheckOperatorDiversityCompliance( + const VerifiedSCTList& verifiedScts, uint64_t certIssuanceTime, + const CTLogOperatorList& dependentOperators, bool& compliant) { + size_t independentOperatorsCount; + CountIndependentLogOperatorsForSelectedScts( + verifiedScts, dependentOperators, independentOperatorsCount, + [certIssuanceTime](const VerifiedSCT& verifiedSct) -> bool { + return LogWasQualifiedForSct(verifiedSct, certIssuanceTime); + }); + // Having at least 2 operators implies we have at least 2 SCTs. + // For the preexisting certificate exception provision (1 operator) we will + // need to include an additional SCTs count check using + // CountLogsForSelectedScts(verifiedScts, sctsCount, + // [certIssuanceTime](const VerifiedSCT& verifiedSct)->bool { + // return LogWasQualifiedForSct(verifiedSct, certIssuanceTime); + // }); + compliant = independentOperatorsCount >= 2; +} + +// Qualification Case #1 (non-embedded SCTs) - the following must hold: +// a. An SCT from a log qualified at the time of check is presented via the +// TLS extension OR is embedded within a stapled OCSP response; +// AND +// b. There are at least two SCTs from logs qualified at the time of check, +// presented via any method. +static void CheckNonEmbeddedCompliance(const VerifiedSCTList& verifiedScts, + bool& compliant) { + if (!HasValidNonEmbeddedSct(verifiedScts)) { + compliant = false; + return; + } + + size_t validSctsCount; + CountLogsForSelectedScts( + verifiedScts, validSctsCount, [](const VerifiedSCT& verifiedSct) -> bool { + return verifiedSct.status == VerifiedSCT::Status::Valid; + }); + + compliant = validSctsCount >= 2; +} + +// Qualification Case #2 (embedded SCTs) - the following must hold: +// a. An Embedded SCT from a log qualified at the time of check is presented; +// AND +// b. There are Embedded SCTs from AT LEAST N + 1 once or currently qualified +// logs, where N is the lifetime of the certificate in years (normally +// rounding up, but rounding down when up to 3 months over), and must be +// at least 1. +static void CheckEmbeddedCompliance(const VerifiedSCTList& verifiedScts, + size_t certLifetimeInCalendarMonths, + uint64_t certIssuanceTime, + bool& compliant) { + if (!HasValidEmbeddedSct(verifiedScts)) { + compliant = false; + return; + } + + // Count the compliant embedded SCTs. Only a single SCT from each log + // is accepted. Note that a given log might return several different SCTs + // for the same precertificate (it is permitted, but advised against). + size_t embeddedSctsCount; + CountLogsForSelectedScts( + verifiedScts, embeddedSctsCount, + [certIssuanceTime](const VerifiedSCT& verifiedSct) -> bool { + return verifiedSct.origin == VerifiedSCT::Origin::Embedded && + LogWasQualifiedForSct(verifiedSct, certIssuanceTime); + }); + + size_t requiredSctsCount = + GetRequiredEmbeddedSctsCount(certLifetimeInCalendarMonths); + + compliant = embeddedSctsCount >= requiredSctsCount; +} + +void CTPolicyEnforcer::CheckCompliance( + const VerifiedSCTList& verifiedScts, size_t certLifetimeInCalendarMonths, + const CTLogOperatorList& dependentOperators, + CTPolicyCompliance& compliance) { + uint64_t certIssuanceTime = GetEffectiveCertIssuanceTime(verifiedScts); + + bool diversityOK; + CheckOperatorDiversityCompliance(verifiedScts, certIssuanceTime, + dependentOperators, diversityOK); + + bool nonEmbeddedCaseOK; + CheckNonEmbeddedCompliance(verifiedScts, nonEmbeddedCaseOK); + + bool embeddedCaseOK; + CheckEmbeddedCompliance(verifiedScts, certLifetimeInCalendarMonths, + certIssuanceTime, embeddedCaseOK); + + if (nonEmbeddedCaseOK || embeddedCaseOK) { + compliance = diversityOK ? CTPolicyCompliance::Compliant + : CTPolicyCompliance::NotDiverseScts; + } else { + // Not enough SCTs are present to satisfy either case of the policy. + compliance = CTPolicyCompliance::NotEnoughScts; + } + + switch (compliance) { + case CTPolicyCompliance::Compliant: + case CTPolicyCompliance::NotEnoughScts: + case CTPolicyCompliance::NotDiverseScts: + break; + case CTPolicyCompliance::Unknown: + default: + assert(false); + } +} + +} // namespace ct +} // namespace mozilla -- cgit v1.2.3