gecko-dev/security/manager/ssl/PublicKeyPinningService.cpp

/* 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 "PublicKeyPinningService.h"

#include "RootCertificateTelemetryUtils.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/Base64.h"
#include "mozilla/BinarySearch.h"
#include "mozilla/Casting.h"
#include "mozilla/Logging.h"
#include "mozilla/Telemetry.h"
#include "nsDependentString.h"
#include "nsISiteSecurityService.h"
#include "nsServiceManagerUtils.h"
#include "nsSiteSecurityService.h"
#include "mozpkix/pkixtypes.h"
#include "seccomon.h"
#include "sechash.h"

#include "StaticHPKPins.h"  // autogenerated by genHPKPStaticpins.js

using namespace mozilla;
using namespace mozilla::pkix;
using namespace mozilla::psm;

LazyLogModule gPublicKeyPinningLog("PublicKeyPinningService");

/**
 Computes in the location specified by base64Out the SHA256 digest
 of the DER Encoded subject Public Key Info for the given cert
*/
static nsresult GetBase64HashSPKI(const CERTCertificate* cert,
                                  nsACString& hashSPKIDigest) {
  hashSPKIDigest.Truncate();
  Digest digest;
  nsresult rv = digest.DigestBuf(SEC_OID_SHA256, cert->derPublicKey.data,
                                 cert->derPublicKey.len);
  if (NS_FAILED(rv)) {
    return rv;
  }
  return Base64Encode(nsDependentCSubstring(
                          BitwiseCast<char*, unsigned char*>(digest.get().data),
                          digest.get().len),
                      hashSPKIDigest);
}

/*
 * Sets certMatchesPinset to true if a given cert matches any fingerprints from
 * the given pinset or the dynamicFingerprints array, or to false otherwise.
 */
static nsresult EvalCert(const CERTCertificate* cert,
                         const StaticFingerprints* fingerprints,
                         const nsTArray<nsCString>* dynamicFingerprints,
                         /*out*/ bool& certMatchesPinset) {
  certMatchesPinset = false;
  if (!fingerprints && !dynamicFingerprints) {
    MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
            ("pkpin: No hashes found\n"));
    return NS_ERROR_INVALID_ARG;
  }

  nsAutoCString base64Out;
  nsresult rv = GetBase64HashSPKI(cert, base64Out);
  if (NS_FAILED(rv)) {
    MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
            ("pkpin: GetBase64HashSPKI failed!\n"));
    return rv;
  }

  if (fingerprints) {
    for (size_t i = 0; i < fingerprints->size; i++) {
      if (base64Out.Equals(fingerprints->data[i])) {
        MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
                ("pkpin: found pin base_64 ='%s'\n", base64Out.get()));
        certMatchesPinset = true;
        return NS_OK;
      }
    }
  }
  if (dynamicFingerprints) {
    for (size_t i = 0; i < dynamicFingerprints->Length(); i++) {
      if (base64Out.Equals((*dynamicFingerprints)[i])) {
        MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
                ("pkpin: found pin base_64 ='%s'\n", base64Out.get()));
        certMatchesPinset = true;
        return NS_OK;
      }
    }
  }
  return NS_OK;
}

/*
 * Sets certListIntersectsPinset to true if a given chain matches any
 * fingerprints from the given static fingerprints or the
 * dynamicFingerprints array, or to false otherwise.
 */
static nsresult EvalChain(const RefPtr<nsNSSCertList>& certList,
                          const StaticFingerprints* fingerprints,
                          const nsTArray<nsCString>* dynamicFingerprints,
                          /*out*/ bool& certListIntersectsPinset) {
  certListIntersectsPinset = false;
  if (!fingerprints && !dynamicFingerprints) {
    MOZ_ASSERT(false, "Must pass in at least one type of pinset");
    return NS_ERROR_FAILURE;
  }

  certList->ForEachCertificateInChain(
      [&certListIntersectsPinset, &fingerprints, &dynamicFingerprints](
          nsCOMPtr<nsIX509Cert> aCert, bool aHasMore,
          /* out */ bool& aContinue) {
        // We need an owning handle when calling nsIX509Cert::GetCert().
        UniqueCERTCertificate nssCert(aCert->GetCert());
        MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
                ("pkpin: certArray subject: '%s'\n", nssCert->subjectName));
        MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
                ("pkpin: certArray issuer: '%s'\n", nssCert->issuerName));
        nsresult rv = EvalCert(nssCert.get(), fingerprints, dynamicFingerprints,
                               certListIntersectsPinset);
        if (NS_FAILED(rv)) {
          return rv;
        }

        if (certListIntersectsPinset) {
          aContinue = false;
        }
        return NS_OK;
      });

  if (!certListIntersectsPinset) {
    MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
            ("pkpin: no matches found\n"));
  }
  return NS_OK;
}

class TransportSecurityPreloadBinarySearchComparator {
 public:
  explicit TransportSecurityPreloadBinarySearchComparator(
      const char* aTargetHost)
      : mTargetHost(aTargetHost) {}

  int operator()(const TransportSecurityPreload& val) const {
    return strcmp(mTargetHost, val.mHost);
  }

 private:
  const char* mTargetHost;  // non-owning
};

nsresult PublicKeyPinningService::ChainMatchesPinset(
    const RefPtr<nsNSSCertList>& certList,
    const nsTArray<nsCString>& aSHA256keys,
    /*out*/ bool& chainMatchesPinset) {
  return EvalChain(certList, nullptr, &aSHA256keys, chainMatchesPinset);
}

// Returns via one of the output parameters the most relevant pinning
// information that is valid for the given host at the given time.
// Dynamic pins are prioritized over static pins.
static nsresult FindPinningInformation(
    const char* hostname, mozilla::pkix::Time time,
    const OriginAttributes& originAttributes,
    /*out*/ nsTArray<nsCString>& dynamicFingerprints,
    /*out*/ const TransportSecurityPreload*& staticFingerprints) {
  if (!hostname || hostname[0] == 0) {
    return NS_ERROR_INVALID_ARG;
  }
  staticFingerprints = nullptr;
  dynamicFingerprints.Clear();
  nsCOMPtr<nsISiteSecurityService> sssService =
      do_GetService(NS_SSSERVICE_CONTRACTID);
  if (!sssService) {
    return NS_ERROR_FAILURE;
  }
  const TransportSecurityPreload* foundEntry = nullptr;
  const char* evalHost = hostname;
  const char* evalPart;
  // Notice how the (xx = strchr) prevents pins for unqualified domain names.
  while (!foundEntry && (evalPart = strchr(evalHost, '.'))) {
    MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
            ("pkpin: Querying pinsets for host: '%s'\n", evalHost));
    // Attempt dynamic pins first
    nsresult rv;
    bool found;
    bool includeSubdomains;
    nsTArray<nsCString> pinArray;
    rv = sssService->GetKeyPinsForHostname(nsDependentCString(evalHost), time,
                                           originAttributes, pinArray,
                                           &includeSubdomains, &found);
    if (NS_FAILED(rv)) {
      return rv;
    }
    if (found && (evalHost == hostname || includeSubdomains)) {
      MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
              ("pkpin: Found dyn match for host: '%s'\n", evalHost));
      dynamicFingerprints = pinArray;
      return NS_OK;
    }

    size_t foundEntryIndex;
    if (BinarySearchIf(kPublicKeyPinningPreloadList, 0,
                       ArrayLength(kPublicKeyPinningPreloadList),
                       TransportSecurityPreloadBinarySearchComparator(evalHost),
                       &foundEntryIndex)) {
      foundEntry = &kPublicKeyPinningPreloadList[foundEntryIndex];
      MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
              ("pkpin: Found pinset for host: '%s'\n", evalHost));
      if (evalHost != hostname) {
        if (!foundEntry->mIncludeSubdomains) {
          // Does not apply to this host, continue iterating
          foundEntry = nullptr;
        }
      }
    } else {
      MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
              ("pkpin: Didn't find pinset for host: '%s'\n", evalHost));
    }
    // Add one for '.'
    evalHost = evalPart + 1;
  }

  if (foundEntry && foundEntry->pinset) {
    if (time > TimeFromEpochInSeconds(kPreloadPKPinsExpirationTime /
                                      PR_USEC_PER_SEC)) {
      return NS_OK;
    }
    staticFingerprints = foundEntry;
  }
  return NS_OK;
}

// Returns true via the output parameter if the given certificate list meets
// pinning requirements for the given host at the given time. It must be the
// case that either there is an intersection between the set of hashes of
// subject public key info data in the list and the most relevant non-expired
// pinset for the host or there is no pinning information for the host.
static nsresult CheckPinsForHostname(
    const RefPtr<nsNSSCertList>& certList, const char* hostname,
    bool enforceTestMode, mozilla::pkix::Time time,
    const OriginAttributes& originAttributes,
    /*out*/ bool& chainHasValidPins,
    /*optional out*/ PinningTelemetryInfo* pinningTelemetryInfo) {
  chainHasValidPins = false;
  if (!certList) {
    return NS_ERROR_INVALID_ARG;
  }
  if (!hostname || hostname[0] == 0) {
    return NS_ERROR_INVALID_ARG;
  }

  nsTArray<nsCString> dynamicFingerprints;
  const TransportSecurityPreload* staticFingerprints = nullptr;
  nsresult rv = FindPinningInformation(hostname, time, originAttributes,
                                       dynamicFingerprints, staticFingerprints);
  // If we have no pinning information, the certificate chain trivially
  // validates with respect to pinning.
  if (dynamicFingerprints.Length() == 0 && !staticFingerprints) {
    chainHasValidPins = true;
    return NS_OK;
  }
  if (dynamicFingerprints.Length() > 0) {
    return EvalChain(certList, nullptr, &dynamicFingerprints,
                     chainHasValidPins);
  }
  if (staticFingerprints) {
    bool enforceTestModeResult;
    rv = EvalChain(certList, staticFingerprints->pinset, nullptr,
                   enforceTestModeResult);
    if (NS_FAILED(rv)) {
      return rv;
    }
    chainHasValidPins = enforceTestModeResult;
    Telemetry::HistogramID histogram = staticFingerprints->mIsMoz
                                           ? Telemetry::CERT_PINNING_MOZ_RESULTS
                                           : Telemetry::CERT_PINNING_RESULTS;
    if (staticFingerprints->mTestMode) {
      histogram = staticFingerprints->mIsMoz
                      ? Telemetry::CERT_PINNING_MOZ_TEST_RESULTS
                      : Telemetry::CERT_PINNING_TEST_RESULTS;
      if (!enforceTestMode) {
        chainHasValidPins = true;
      }
    }
    // We can collect per-host pinning violations for this host because it is
    // operationally critical to Firefox.
    if (pinningTelemetryInfo) {
      if (staticFingerprints->mId != kUnknownId) {
        int32_t bucket =
            staticFingerprints->mId * 2 + (enforceTestModeResult ? 1 : 0);
        histogram = staticFingerprints->mTestMode
                        ? Telemetry::CERT_PINNING_MOZ_TEST_RESULTS_BY_HOST
                        : Telemetry::CERT_PINNING_MOZ_RESULTS_BY_HOST;
        pinningTelemetryInfo->certPinningResultBucket = bucket;
      } else {
        pinningTelemetryInfo->certPinningResultBucket =
            enforceTestModeResult ? 1 : 0;
      }
      pinningTelemetryInfo->accumulateResult = true;
      pinningTelemetryInfo->certPinningResultHistogram = Some(histogram);
    }

    // We only collect per-CA pinning statistics upon failures.
    nsCOMPtr<nsIX509Cert> rootCert;
    rv = certList->GetRootCertificate(rootCert);
    if (NS_FAILED(rv)) {
      return rv;
    }

    // Only log telemetry if the certificate list is non-empty.
    if (rootCert && !enforceTestModeResult && pinningTelemetryInfo) {
      UniqueCERTCertificate rootCertObj =
          UniqueCERTCertificate(rootCert.get()->GetCert());
      if (rootCertObj) {
        int32_t binNumber = RootCABinNumber(&rootCertObj->derCert);
        if (binNumber != ROOT_CERTIFICATE_UNKNOWN) {
          pinningTelemetryInfo->accumulateForRoot = true;
          pinningTelemetryInfo->rootBucket = binNumber;
        }
      }
    }

    MOZ_LOG(gPublicKeyPinningLog, LogLevel::Debug,
            ("pkpin: Pin check %s for %s host '%s' (mode=%s)\n",
             enforceTestModeResult ? "passed" : "failed",
             staticFingerprints->mIsMoz ? "mozilla" : "non-mozilla", hostname,
             staticFingerprints->mTestMode ? "test" : "production"));
  }

  return NS_OK;
}

nsresult PublicKeyPinningService::ChainHasValidPins(
    const RefPtr<nsNSSCertList>& certList, const char* hostname,
    mozilla::pkix::Time time, bool enforceTestMode,
    const OriginAttributes& originAttributes,
    /*out*/ bool& chainHasValidPins,
    /*optional out*/ PinningTelemetryInfo* pinningTelemetryInfo) {
  chainHasValidPins = false;
  if (!certList) {
    return NS_ERROR_INVALID_ARG;
  }
  if (!hostname || hostname[0] == 0) {
    return NS_ERROR_INVALID_ARG;
  }
  nsAutoCString canonicalizedHostname(CanonicalizeHostname(hostname));
  return CheckPinsForHostname(certList, canonicalizedHostname.get(),
                              enforceTestMode, time, originAttributes,
                              chainHasValidPins, pinningTelemetryInfo);
}

nsresult PublicKeyPinningService::HostHasPins(
    const char* hostname, mozilla::pkix::Time time, bool enforceTestMode,
    const OriginAttributes& originAttributes,
    /*out*/ bool& hostHasPins) {
  hostHasPins = false;
  nsAutoCString canonicalizedHostname(CanonicalizeHostname(hostname));
  nsTArray<nsCString> dynamicFingerprints;
  const TransportSecurityPreload* staticFingerprints = nullptr;
  nsresult rv = FindPinningInformation(canonicalizedHostname.get(), time,
                                       originAttributes, dynamicFingerprints,
                                       staticFingerprints);
  if (NS_FAILED(rv)) {
    return rv;
  }
  if (dynamicFingerprints.Length() > 0) {
    hostHasPins = true;
  } else if (staticFingerprints) {
    hostHasPins = !staticFingerprints->mTestMode || enforceTestMode;
  }
  return NS_OK;
}

nsAutoCString PublicKeyPinningService::CanonicalizeHostname(
    const char* hostname) {
  nsAutoCString canonicalizedHostname(hostname);
  ToLowerCase(canonicalizedHostname);
  while (canonicalizedHostname.Length() > 0 &&
         canonicalizedHostname.Last() == '.') {
    canonicalizedHostname.Truncate(canonicalizedHostname.Length() - 1);
  }
  return canonicalizedHostname;
}