security/apps/AppSignatureVerification.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=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 "nsNSSCertificateDB.h"

#include "AppTrustDomain.h"
#include "CryptoTask.h"
#include "NSSCertDBTrustDomain.h"
#include "ScopedNSSTypes.h"
#include "SharedCertVerifier.h"
#include "certdb.h"
#include "cms.h"
#include "cosec.h"
#include "mozilla/Base64.h"
#include "mozilla/Casting.h"
#include "mozilla/Logging.h"
#include "mozilla/Preferences.h"
#include "mozilla/RefPtr.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
#include "nsCOMPtr.h"
#include "nsComponentManagerUtils.h"
#include "nsDependentString.h"
#include "nsHashKeys.h"
#include "nsIFile.h"
#include "nsIInputStream.h"
#include "nsIStringEnumerator.h"
#include "nsIZipReader.h"
#include "nsNSSCertificate.h"
#include "nsNetUtil.h"
#include "nsProxyRelease.h"
#include "nsString.h"
#include "nsTHashtable.h"
#include "mozpkix/pkix.h"
#include "mozpkix/pkixnss.h"
#include "mozpkix/pkixutil.h"
#include "secerr.h"
#include "secmime.h"

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

extern mozilla::LazyLogModule gPIPNSSLog;

namespace {

// A convenient way to pair the bytes of a digest with the algorithm that
// purportedly produced those bytes. Only SHA-1 and SHA-256 are supported.
struct DigestWithAlgorithm {
  nsresult ValidateLength() const {
    size_t hashLen;
    switch (mAlgorithm) {
      case SEC_OID_SHA256:
        hashLen = SHA256_LENGTH;
        break;
      case SEC_OID_SHA1:
        hashLen = SHA1_LENGTH;
        break;
      default:
        MOZ_ASSERT_UNREACHABLE(
            "unsupported hash type in DigestWithAlgorithm::ValidateLength");
        return NS_ERROR_FAILURE;
    }
    if (mDigest.Length() != hashLen) {
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
    }
    return NS_OK;
  }

  nsAutoCString mDigest;
  SECOidTag mAlgorithm;
};

// The digest must have a lifetime greater than or equal to the returned string.
inline nsDependentCSubstring DigestToDependentString(
    nsTArray<uint8_t>& digest) {
  return nsDependentCSubstring(BitwiseCast<char*, uint8_t*>(digest.Elements()),
                               digest.Length());
}

// Reads a maximum of 8MB from a stream into the supplied buffer.
// The reason for the 8MB limit is because this function is used to read
// signature-related files and we want to avoid OOM. The uncompressed length of
// an entry can be hundreds of times larger than the compressed version,
// especially if someone has specifically crafted the entry to cause OOM or to
// consume massive amounts of disk space.
//
// @param stream  The input stream to read from.
// @param buf     The buffer that we read the stream into, which must have
//                already been allocated.
nsresult ReadStream(const nsCOMPtr<nsIInputStream>& stream,
                    /*out*/ SECItem& buf) {
  // The size returned by Available() might be inaccurate so we need
  // to check that Available() matches up with the actual length of
  // the file.
  uint64_t length;
  nsresult rv = stream->Available(&length);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  // Cap the maximum accepted size of signature-related files at 8MB (which
  // should be much larger than necessary for our purposes) to avoid OOM.
  static const uint32_t MAX_LENGTH = 8 * 1000 * 1000;
  if (length > MAX_LENGTH) {
    return NS_ERROR_FILE_TOO_BIG;
  }

  // With bug 164695 in mind we +1 to leave room for null-terminating
  // the buffer.
  SECITEM_AllocItem(buf, static_cast<uint32_t>(length + 1));

  // buf.len == length + 1. We attempt to read length + 1 bytes
  // instead of length, so that we can check whether the metadata for
  // the entry is incorrect.
  uint32_t bytesRead;
  rv = stream->Read(BitwiseCast<char*, unsigned char*>(buf.data), buf.len,
                    &bytesRead);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }
  if (bytesRead != length) {
    return NS_ERROR_FILE_CORRUPTED;
  }

  buf.data[buf.len - 1] = 0;  // null-terminate

  return NS_OK;
}

// Finds exactly one (signature metadata) JAR entry that matches the given
// search pattern, and then loads it. Fails if there are no matches or if
// there is more than one match. If bufDigest is not null then on success
// bufDigest will contain the digeset of the entry using the given digest
// algorithm.
nsresult FindAndLoadOneEntry(
    nsIZipReader* zip, const nsACString& searchPattern,
    /*out*/ nsACString& filename,
    /*out*/ SECItem& buf,
    /*optional, in*/ SECOidTag digestAlgorithm = SEC_OID_SHA1,
    /*optional, out*/ nsTArray<uint8_t>* bufDigest = nullptr) {
  nsCOMPtr<nsIUTF8StringEnumerator> files;
  nsresult rv = zip->FindEntries(searchPattern, getter_AddRefs(files));
  if (NS_FAILED(rv) || !files) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }

  bool more;
  rv = files->HasMore(&more);
  NS_ENSURE_SUCCESS(rv, rv);
  if (!more) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }

  rv = files->GetNext(filename);
  NS_ENSURE_SUCCESS(rv, rv);

  // Check if there is more than one match, if so then error!
  rv = files->HasMore(&more);
  NS_ENSURE_SUCCESS(rv, rv);
  if (more) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }

  nsCOMPtr<nsIInputStream> stream;
  rv = zip->GetInputStream(filename, getter_AddRefs(stream));
  NS_ENSURE_SUCCESS(rv, rv);

  rv = ReadStream(stream, buf);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return NS_ERROR_SIGNED_JAR_ENTRY_INVALID;
  }

  if (bufDigest) {
    rv = Digest::DigestBuf(digestAlgorithm,
                           Span<uint8_t>{buf.data, buf.len - 1}, *bufDigest);
    NS_ENSURE_SUCCESS(rv, rv);
  }

  return NS_OK;
}

// Verify the digest of an entry. We avoid loading the entire entry into memory
// at once, which would require memory in proportion to the size of the largest
// entry. Instead, we require only a small, fixed amount of memory.
//
// @param stream  an input stream from a JAR entry or file depending on whether
//                it is from a signed archive or unpacked into a directory
// @param digestFromManifest The digest that we're supposed to check the file's
//                           contents against, from the manifest
// @param buf A scratch buffer that we use for doing the I/O, which must have
//            already been allocated. The size of this buffer is the unit
//            size of our I/O.
nsresult VerifyStreamContentDigest(
    nsIInputStream* stream, const DigestWithAlgorithm& digestFromManifest,
    SECItem& buf) {
  MOZ_ASSERT(buf.len > 0);
  nsresult rv = digestFromManifest.ValidateLength();
  if (NS_FAILED(rv)) {
    return rv;
  }

  uint64_t len64;
  rv = stream->Available(&len64);
  NS_ENSURE_SUCCESS(rv, rv);
  if (len64 > UINT32_MAX) {
    return NS_ERROR_SIGNED_JAR_ENTRY_TOO_LARGE;
  }

  Digest digest;

  rv = digest.Begin(digestFromManifest.mAlgorithm);
  NS_ENSURE_SUCCESS(rv, rv);

  uint64_t totalBytesRead = 0;
  for (;;) {
    uint32_t bytesRead;
    rv = stream->Read(BitwiseCast<char*, unsigned char*>(buf.data), buf.len,
                      &bytesRead);
    NS_ENSURE_SUCCESS(rv, rv);

    if (bytesRead == 0) {
      break;  // EOF
    }

    totalBytesRead += bytesRead;
    if (totalBytesRead >= UINT32_MAX) {
      return NS_ERROR_SIGNED_JAR_ENTRY_TOO_LARGE;
    }

    rv = digest.Update(buf.data, bytesRead);
    NS_ENSURE_SUCCESS(rv, rv);
  }

  if (totalBytesRead != len64) {
    // The metadata we used for Available() doesn't match the actual size of
    // the entry.
    return NS_ERROR_SIGNED_JAR_ENTRY_INVALID;
  }

  // Verify that the digests match.
  nsTArray<uint8_t> outArray;
  rv = digest.End(outArray);
  NS_ENSURE_SUCCESS(rv, rv);

  nsDependentCSubstring digestStr(DigestToDependentString(outArray));
  if (!digestStr.Equals(digestFromManifest.mDigest)) {
    return NS_ERROR_SIGNED_JAR_MODIFIED_ENTRY;
  }

  return NS_OK;
}

nsresult VerifyEntryContentDigest(nsIZipReader* zip,
                                  const nsACString& aFilename,
                                  const DigestWithAlgorithm& digestFromManifest,
                                  SECItem& buf) {
  nsCOMPtr<nsIInputStream> stream;
  nsresult rv = zip->GetInputStream(aFilename, getter_AddRefs(stream));
  if (NS_FAILED(rv)) {
    return NS_ERROR_SIGNED_JAR_ENTRY_MISSING;
  }

  return VerifyStreamContentDigest(stream, digestFromManifest, buf);
}

// On input, nextLineStart is the start of the current line. On output,
// nextLineStart is the start of the next line.
nsresult ReadLine(/*in/out*/ const char*& nextLineStart,
                  /*out*/ nsCString& line, bool allowContinuations = true) {
  line.Truncate();
  size_t previousLength = 0;
  size_t currentLength = 0;
  for (;;) {
    const char* eol = strpbrk(nextLineStart, "\r\n");

    if (!eol) {  // Reached end of file before newline
      eol = nextLineStart + strlen(nextLineStart);
    }

    previousLength = currentLength;
    line.Append(nextLineStart, eol - nextLineStart);
    currentLength = line.Length();

    // The spec says "No line may be longer than 72 bytes (not characters)"
    // in its UTF8-encoded form.
    static const size_t lineLimit = 72;
    if (currentLength - previousLength > lineLimit) {
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
    }

    // The spec says: "Implementations should support 65535-byte
    // (not character) header values..."
    if (currentLength > 65535) {
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
    }

    if (*eol == '\r') {
      ++eol;
    }
    if (*eol == '\n') {
      ++eol;
    }

    nextLineStart = eol;

    if (*eol != ' ') {
      // not a continuation
      return NS_OK;
    }

    // continuation
    if (!allowContinuations) {
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
    }

    ++nextLineStart;  // skip space and keep appending
  }
}

// The header strings are defined in the JAR specification.
#define JAR_MF_SEARCH_STRING "(M|/M)ETA-INF/(M|m)(ANIFEST|anifest).(MF|mf)$"
#define JAR_COSE_MF_SEARCH_STRING "(M|/M)ETA-INF/cose.manifest$"
#define JAR_SF_SEARCH_STRING "(M|/M)ETA-INF/*.(SF|sf)$"
#define JAR_RSA_SEARCH_STRING "(M|/M)ETA-INF/*.(RSA|rsa)$"
#define JAR_COSE_SEARCH_STRING "(M|/M)ETA-INF/cose.sig$"
#define JAR_META_DIR "META-INF"
#define JAR_MF_HEADER "Manifest-Version: 1.0"
#define JAR_SF_HEADER "Signature-Version: 1.0"

nsresult ParseAttribute(const nsAutoCString& curLine,
                        /*out*/ nsAutoCString& attrName,
                        /*out*/ nsAutoCString& attrValue) {
  // Find the colon that separates the name from the value.
  int32_t colonPos = curLine.FindChar(':');
  if (colonPos == kNotFound) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }

  // set attrName to the name, skipping spaces between the name and colon
  int32_t nameEnd = colonPos;
  for (;;) {
    if (nameEnd == 0) {
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;  // colon with no name
    }
    if (curLine[nameEnd - 1] != ' ') break;
    --nameEnd;
  }
  curLine.Left(attrName, nameEnd);

  // Set attrValue to the value, skipping spaces between the colon and the
  // value. The value may be empty.
  int32_t valueStart = colonPos + 1;
  int32_t curLineLength = curLine.Length();
  while (valueStart != curLineLength && curLine[valueStart] == ' ') {
    ++valueStart;
  }
  curLine.Right(attrValue, curLineLength - valueStart);

  return NS_OK;
}

// Parses the version line of the MF or SF header.
nsresult CheckManifestVersion(const char*& nextLineStart,
                              const nsACString& expectedHeader) {
  // The JAR spec says: "Manifest-Version and Signature-Version must be first,
  // and in exactly that case (so that they can be recognized easily as magic
  // strings)."
  nsAutoCString curLine;
  nsresult rv = ReadLine(nextLineStart, curLine, false);
  if (NS_FAILED(rv)) {
    return rv;
  }
  if (!curLine.Equals(expectedHeader)) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }
  return NS_OK;
}

// Parses a signature file (SF) based on the JDK 8 JAR Specification.
//
// The SF file must contain a SHA*-Digest-Manifest attribute in the main
// section (where the * is either 1 or 256, depending on the given digest
// algorithm). All other sections are ignored. This means that this will NOT
// parse old-style signature files that have separate digests per entry.
// The JDK8 x-Digest-Manifest variant is better because:
//
//   (1) It allows us to follow the principle that we should minimize the
//       processing of data that we do before we verify its signature. In
//       particular, with the x-Digest-Manifest style, we can verify the digest
//       of MANIFEST.MF before we parse it, which prevents malicious JARs
//       exploiting our MANIFEST.MF parser.
//   (2) It is more time-efficient and space-efficient to have one
//       x-Digest-Manifest instead of multiple x-Digest values.
//
// filebuf must be null-terminated. On output, mfDigest will contain the
// decoded value of the appropriate SHA*-DigestManifest, if found.
nsresult ParseSF(const char* filebuf, SECOidTag digestAlgorithm,
                 /*out*/ nsAutoCString& mfDigest) {
  const char* digestNameToFind = nullptr;
  switch (digestAlgorithm) {
    case SEC_OID_SHA256:
      digestNameToFind = "sha256-digest-manifest";
      break;
    case SEC_OID_SHA1:
      digestNameToFind = "sha1-digest-manifest";
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("bad argument to ParseSF");
      return NS_ERROR_FAILURE;
  }

  const char* nextLineStart = filebuf;
  nsresult rv =
      CheckManifestVersion(nextLineStart, nsLiteralCString(JAR_SF_HEADER));
  if (NS_FAILED(rv)) {
    return rv;
  }

  for (;;) {
    nsAutoCString curLine;
    rv = ReadLine(nextLineStart, curLine);
    if (NS_FAILED(rv)) {
      return rv;
    }

    if (curLine.Length() == 0) {
      // End of main section (blank line or end-of-file). We didn't find the
      // SHA*-Digest-Manifest we were looking for.
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
    }

    nsAutoCString attrName;
    nsAutoCString attrValue;
    rv = ParseAttribute(curLine, attrName, attrValue);
    if (NS_FAILED(rv)) {
      return rv;
    }

    if (attrName.EqualsIgnoreCase(digestNameToFind)) {
      rv = Base64Decode(attrValue, mfDigest);
      if (NS_FAILED(rv)) {
        return rv;
      }

      // There could be multiple SHA*-Digest-Manifest attributes, which
      // would be an error, but it's better to just skip any erroneous
      // duplicate entries rather than trying to detect them, because:
      //
      //   (1) It's simpler, and simpler generally means more secure
      //   (2) An attacker can't make us accept a JAR we would otherwise
      //       reject just by adding additional SHA*-Digest-Manifest
      //       attributes.
      return NS_OK;
    }

    // ignore unrecognized attributes
  }

  MOZ_ASSERT_UNREACHABLE("somehow exited loop in ParseSF without returning");
  return NS_ERROR_FAILURE;
}

// Parses MANIFEST.MF. The filenames of all entries will be returned in
// mfItems. buf must be a pre-allocated scratch buffer that is used for doing
// I/O. Each file's contents are verified against the entry in the manifest with
// the digest algorithm that matches the given one. This algorithm comes from
// the signature file. If the signature file has a SHA-256 digest, then SHA-256
// entries must be present in the manifest file. If the signature file only has
// a SHA-1 digest, then only SHA-1 digests will be used in the manifest file.
nsresult ParseMF(const char* filebuf, nsIZipReader* zip,
                 SECOidTag digestAlgorithm,
                 /*out*/ nsTHashtable<nsCStringHashKey>& mfItems,
                 ScopedAutoSECItem& buf) {
  const char* digestNameToFind = nullptr;
  switch (digestAlgorithm) {
    case SEC_OID_SHA256:
      digestNameToFind = "sha256-digest";
      break;
    case SEC_OID_SHA1:
      digestNameToFind = "sha1-digest";
      break;
    default:
      MOZ_ASSERT_UNREACHABLE("bad argument to ParseMF");
      return NS_ERROR_FAILURE;
  }

  const char* nextLineStart = filebuf;
  nsresult rv =
      CheckManifestVersion(nextLineStart, nsLiteralCString(JAR_MF_HEADER));
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Skip the rest of the header section, which ends with a blank line.
  {
    nsAutoCString line;
    do {
      rv = ReadLine(nextLineStart, line);
      if (NS_FAILED(rv)) {
        return rv;
      }
    } while (line.Length() > 0);

    // Manifest containing no file entries is OK, though useless.
    if (*nextLineStart == '\0') {
      return NS_OK;
    }
  }

  nsAutoCString curItemName;
  nsAutoCString digest;

  for (;;) {
    nsAutoCString curLine;
    rv = ReadLine(nextLineStart, curLine);
    if (NS_FAILED(rv)) {
      return rv;
    }

    if (curLine.Length() == 0) {
      // end of section (blank line or end-of-file)

      if (curItemName.Length() == 0) {
        // '...Each section must start with an attribute with the name as
        // "Name",...', so every section must have a Name attribute.
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
      }

      if (digest.IsEmpty()) {
        // We require every entry to have a digest, since we require every
        // entry to be signed and we don't allow duplicate entries.
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
      }

      if (mfItems.Contains(curItemName)) {
        // Duplicate entry
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
      }

      // Verify that the entry's content digest matches the digest from this
      // MF section.
      DigestWithAlgorithm digestWithAlgorithm = {digest, digestAlgorithm};
      rv = VerifyEntryContentDigest(zip, curItemName, digestWithAlgorithm, buf);
      if (NS_FAILED(rv)) {
        return rv;
      }

      mfItems.PutEntry(curItemName);

      if (*nextLineStart == '\0') {
        // end-of-file
        break;
      }

      // reset so we know we haven't encountered either of these for the next
      // item yet.
      curItemName.Truncate();
      digest.Truncate();

      continue;  // skip the rest of the loop below
    }

    nsAutoCString attrName;
    nsAutoCString attrValue;
    rv = ParseAttribute(curLine, attrName, attrValue);
    if (NS_FAILED(rv)) {
      return rv;
    }

    // Lines to look for:

    // (1) Digest:
    if (attrName.EqualsIgnoreCase(digestNameToFind)) {
      if (!digest.IsEmpty()) {  // multiple SHA* digests in section
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
      }

      rv = Base64Decode(attrValue, digest);
      if (NS_FAILED(rv)) {
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
      }

      continue;
    }

    // (2) Name: associates this manifest section with a file in the jar.
    if (attrName.LowerCaseEqualsLiteral("name")) {
      if (MOZ_UNLIKELY(curItemName.Length() > 0))  // multiple names in section
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;

      if (MOZ_UNLIKELY(attrValue.Length() == 0))
        return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;

      curItemName = attrValue;

      continue;
    }

    // (3) Magic: the only other must-understand attribute
    if (attrName.LowerCaseEqualsLiteral("magic")) {
      // We don't understand any magic, so we can't verify an entry that
      // requires magic. Since we require every entry to have a valid
      // signature, we have no choice but to reject the entry.
      return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
    }

    // unrecognized attributes must be ignored
  }

  return NS_OK;
}

nsresult VerifyCertificate(Span<const uint8_t> signerCert,
                           AppTrustedRoot trustedRoot,
                           nsTArray<Span<const uint8_t>>&& collectedCerts) {
  AppTrustDomain trustDomain(std::move(collectedCerts));
  nsresult rv = trustDomain.SetTrustedRoot(trustedRoot);
  if (NS_FAILED(rv)) {
    return rv;
  }
  Input certDER;
  mozilla::pkix::Result result =
      certDER.Init(signerCert.Elements(), signerCert.Length());
  if (result != Success) {
    return mozilla::psm::GetXPCOMFromNSSError(MapResultToPRErrorCode(result));
  }

  result = BuildCertChain(
      trustDomain, certDER, Now(), EndEntityOrCA::MustBeEndEntity,
      KeyUsage::digitalSignature, KeyPurposeId::id_kp_codeSigning,
      CertPolicyId::anyPolicy, nullptr /*stapledOCSPResponse*/);
  if (result == mozilla::pkix::Result::ERROR_EXPIRED_CERTIFICATE ||
      result == mozilla::pkix::Result::ERROR_NOT_YET_VALID_CERTIFICATE) {
    // For code-signing you normally need trusted 3rd-party timestamps to
    // handle expiration properly. The signer could always mess with their
    // system clock so you can't trust the certificate was un-expired when
    // the signing took place. The choice is either to ignore expiration
    // or to enforce expiration at time of use. The latter leads to the
    // user-hostile result that perfectly good code stops working.
    //
    // Our package format doesn't support timestamps (nor do we have a
    // trusted 3rd party timestamper), but since we sign all of our apps and
    // add-ons ourselves we can trust ourselves not to mess with the clock
    // on the signing systems. We also have a revocation mechanism if we
    // need it. Under these conditions it's OK to ignore cert  errors related
    // to time validity (expiration and "not yet valid").
    //
    // This is an invalid approach if
    //  * we issue certs to let others sign their own packages
    //  * mozilla::pkix returns "expired" when there are "worse" problems
    //    with the certificate or chain.
    // (see bug 1267318)
    result = Success;
  }
  if (result != Success) {
    return mozilla::psm::GetXPCOMFromNSSError(MapResultToPRErrorCode(result));
  }

  return NS_OK;
}

// Given a SECOidTag representing a digest algorithm (either SEC_OID_SHA1 or
// SEC_OID_SHA256), returns the first signerInfo in the given signedData that
// purports to have been created using that digest algorithm, or nullptr if
// there is none.
// The returned signerInfo is owned by signedData, so the caller must ensure
// that the lifetime of the signerInfo is contained by the lifetime of the
// signedData.
NSSCMSSignerInfo* GetSignerInfoForDigestAlgorithm(NSSCMSSignedData* signedData,
                                                  SECOidTag digestAlgorithm) {
  MOZ_ASSERT(digestAlgorithm == SEC_OID_SHA1 ||
             digestAlgorithm == SEC_OID_SHA256);
  if (digestAlgorithm != SEC_OID_SHA1 && digestAlgorithm != SEC_OID_SHA256) {
    return nullptr;
  }

  int numSigners = NSS_CMSSignedData_SignerInfoCount(signedData);
  if (numSigners < 1) {
    return nullptr;
  }
  for (int i = 0; i < numSigners; i++) {
    NSSCMSSignerInfo* signerInfo =
        NSS_CMSSignedData_GetSignerInfo(signedData, i);
    // NSS_CMSSignerInfo_GetDigestAlgTag isn't exported from NSS.
    SECOidData* digestAlgOID = SECOID_FindOID(&signerInfo->digestAlg.algorithm);
    if (!digestAlgOID) {
      continue;
    }
    if (digestAlgorithm == digestAlgOID->offset) {
      return signerInfo;
    }
  }
  return nullptr;
}

Span<const uint8_t> GetPKCS7SignerCert(
    NSSCMSSignerInfo* signerInfo,
    nsTArray<Span<const uint8_t>>& collectedCerts) {
  if (!signerInfo) {
    return {};
  }
  // The NSS APIs use the term "CMS", but since these are all signed by Mozilla
  // infrastructure, we know they are actually PKCS7. This means that this only
  // needs to handle issuer/serial number signer identifiers.
  if (signerInfo->signerIdentifier.identifierType != NSSCMSSignerID_IssuerSN) {
    return {};
  }
  CERTIssuerAndSN* issuerAndSN = signerInfo->signerIdentifier.id.issuerAndSN;
  if (!issuerAndSN) {
    return {};
  }
  Input issuer;
  mozilla::pkix::Result result =
      issuer.Init(issuerAndSN->derIssuer.data, issuerAndSN->derIssuer.len);
  if (result != Success) {
    return {};
  }
  Input serialNumber;
  result = serialNumber.Init(issuerAndSN->serialNumber.data,
                             issuerAndSN->serialNumber.len);
  if (result != Success) {
    return {};
  }
  for (const auto& certDER : collectedCerts) {
    Input certInput;
    result = certInput.Init(certDER.Elements(), certDER.Length());
    if (result != Success) {
      continue;  // probably too big
    }
    // Since this only decodes the certificate and doesn't attempt to build a
    // verified chain with it, the EndEntityOrCA parameter doesn't matter.
    BackCert cert(certInput, EndEntityOrCA::MustBeEndEntity, nullptr);
    result = cert.Init();
    if (result != Success) {
      continue;
    }
    if (InputsAreEqual(issuer, cert.GetIssuer()) &&
        InputsAreEqual(serialNumber, cert.GetSerialNumber())) {
      return certDER;
    }
  }
  return {};
}

nsresult VerifySignature(AppTrustedRoot trustedRoot, const SECItem& buffer,
                         nsTArray<uint8_t>& detachedSHA1Digest,
                         nsTArray<uint8_t>& detachedSHA256Digest,
                         /*out*/ SECOidTag& digestAlgorithm,
                         /*out*/ nsTArray<uint8_t>& signerCert) {
  if (NS_WARN_IF(!buffer.data || buffer.len == 0 ||
                 detachedSHA1Digest.Length() == 0 ||
                 detachedSHA256Digest.Length() == 0)) {
    return NS_ERROR_INVALID_ARG;
  }

  UniqueNSSCMSMessage cmsMsg(NSS_CMSMessage_CreateFromDER(
      const_cast<SECItem*>(&buffer), nullptr, nullptr, nullptr, nullptr,
      nullptr, nullptr));
  if (!cmsMsg) {
    return NS_ERROR_CMS_VERIFY_NOT_SIGNED;
  }

  if (!NSS_CMSMessage_IsSigned(cmsMsg.get())) {
    return NS_ERROR_CMS_VERIFY_NOT_SIGNED;
  }

  NSSCMSContentInfo* cinfo = NSS_CMSMessage_ContentLevel(cmsMsg.get(), 0);
  if (!cinfo) {
    return NS_ERROR_CMS_VERIFY_NO_CONTENT_INFO;
  }

  // We're expecting this to be a PKCS#7 signedData content info.
  if (NSS_CMSContentInfo_GetContentTypeTag(cinfo) !=
      SEC_OID_PKCS7_SIGNED_DATA) {
    return NS_ERROR_CMS_VERIFY_NO_CONTENT_INFO;
  }

  // signedData is non-owning
  NSSCMSSignedData* signedData =
      static_cast<NSSCMSSignedData*>(NSS_CMSContentInfo_GetContent(cinfo));
  if (!signedData) {
    return NS_ERROR_CMS_VERIFY_NO_CONTENT_INFO;
  }

  nsTArray<Span<const uint8_t>> collectedCerts;
  if (signedData->rawCerts) {
    for (size_t i = 0; signedData->rawCerts[i]; ++i) {
      Span<const uint8_t> cert(signedData->rawCerts[i]->data,
                               signedData->rawCerts[i]->len);
      collectedCerts.AppendElement(std::move(cert));
    }
  }

  NSSCMSSignerInfo* signerInfo =
      GetSignerInfoForDigestAlgorithm(signedData, SEC_OID_SHA256);
  nsTArray<uint8_t>* tmpDetachedDigest = &detachedSHA256Digest;
  digestAlgorithm = SEC_OID_SHA256;
  if (!signerInfo) {
    signerInfo = GetSignerInfoForDigestAlgorithm(signedData, SEC_OID_SHA1);
    if (!signerInfo) {
      return NS_ERROR_CMS_VERIFY_NOT_SIGNED;
    }
    tmpDetachedDigest = &detachedSHA1Digest;
    digestAlgorithm = SEC_OID_SHA1;
  }

  const SECItem detachedDigest = {
      siBuffer, tmpDetachedDigest->Elements(),
      static_cast<unsigned int>(tmpDetachedDigest->Length())};

  // Get the certificate that issued the PKCS7 signature.
  Span<const uint8_t> signerCertSpan =
      GetPKCS7SignerCert(signerInfo, collectedCerts);
  if (signerCertSpan.IsEmpty()) {
    return NS_ERROR_CMS_VERIFY_ERROR_PROCESSING;
  }

  nsresult rv =
      VerifyCertificate(signerCertSpan, trustedRoot, std::move(collectedCerts));
  if (NS_FAILED(rv)) {
    return rv;
  }
  signerCert.Clear();
  signerCert.AppendElements(signerCertSpan);

  // Ensure that the PKCS#7 data OID is present as the PKCS#9 contentType.
  const char* pkcs7DataOidString = "1.2.840.113549.1.7.1";
  ScopedAutoSECItem pkcs7DataOid;
  if (SEC_StringToOID(nullptr, &pkcs7DataOid, pkcs7DataOidString, 0) !=
      SECSuccess) {
    return NS_ERROR_CMS_VERIFY_ERROR_PROCESSING;
  }

  // NSS_CMSSignerInfo_Verify relies on NSS_CMSSignerInfo_GetSigningCertificate
  // having been called already. This relies on the signing certificate being
  // decoded as a CERTCertificate.
  // This assertion should never fail, as this certificate has been
  // successfully verified, which means it fits in the size of an unsigned int.
  SECItem signingCertificateItem = {
      siBuffer, const_cast<unsigned char*>(signerCertSpan.Elements()),
      AssertedCast<unsigned int>(signerCertSpan.Length())};
  UniqueCERTCertificate signingCertificateHandle(CERT_NewTempCertificate(
      CERT_GetDefaultCertDB(), &signingCertificateItem, nullptr, false, true));
  if (!signingCertificateHandle) {
    return mozilla::psm::GetXPCOMFromNSSError(SEC_ERROR_PKCS7_BAD_SIGNATURE);
  }
  // NB: This function does not return an owning reference, unlike with many
  // other NSS APIs.
  if (!NSS_CMSSignerInfo_GetSigningCertificate(signerInfo,
                                               CERT_GetDefaultCertDB())) {
    return mozilla::psm::GetXPCOMFromNSSError(SEC_ERROR_PKCS7_BAD_SIGNATURE);
  }
  return MapSECStatus(NSS_CMSSignerInfo_Verify(
      signerInfo, const_cast<SECItem*>(&detachedDigest), &pkcs7DataOid));
}

class CoseVerificationContext {
 public:
  explicit CoseVerificationContext(AppTrustedRoot aTrustedRoot)
      : mTrustedRoot(aTrustedRoot) {}
  ~CoseVerificationContext() = default;

  AppTrustedRoot GetTrustedRoot() { return mTrustedRoot; }
  void SetCert(Span<const uint8_t> certDER) {
    mCertDER.Clear();
    mCertDER.AppendElements(certDER);
  }

  nsTArray<uint8_t> TakeCert() { return std::move(mCertDER); }

 private:
  AppTrustedRoot mTrustedRoot;
  nsTArray<uint8_t> mCertDER;
};

// Verification function called from cose-rust.
// Returns true if everything goes well and the signature and certificate chain
// are good, false in any other case.
bool CoseVerificationCallback(const uint8_t* aPayload, size_t aPayloadLen,
                              const uint8_t** aCertChain, size_t aCertChainLen,
                              const size_t* aCertsLen, const uint8_t* aEECert,
                              size_t aEECertLen, const uint8_t* aSignature,
                              size_t aSignatureLen, uint8_t aSignatureAlgorithm,
                              void* ctx) {
  if (!ctx || !aPayload || !aEECert || !aSignature) {
    return false;
  }
  // The ctx here is a pointer to a CoseVerificationContext object
  CoseVerificationContext* context = static_cast<CoseVerificationContext*>(ctx);
  AppTrustedRoot aTrustedRoot = context->GetTrustedRoot();

  CK_MECHANISM_TYPE mechanism;
  SECOidTag oid;
  uint32_t hash_length;
  SECItem param = {siBuffer, nullptr, 0};
  switch (aSignatureAlgorithm) {
    case ES256:
      mechanism = CKM_ECDSA;
      oid = SEC_OID_SHA256;
      hash_length = SHA256_LENGTH;
      break;
    case ES384:
      mechanism = CKM_ECDSA;
      oid = SEC_OID_SHA384;
      hash_length = SHA384_LENGTH;
      break;
    case ES512:
      mechanism = CKM_ECDSA;
      oid = SEC_OID_SHA512;
      hash_length = SHA512_LENGTH;
      break;
    default:
      return false;
  }

  uint8_t hashBuf[HASH_LENGTH_MAX];
  SECStatus rv = PK11_HashBuf(oid, hashBuf, aPayload, aPayloadLen);
  if (rv != SECSuccess) {
    return false;
  }
  SECItem hashItem = {siBuffer, hashBuf, hash_length};
  Input certInput;
  if (certInput.Init(aEECert, aEECertLen) != Success) {
    return false;
  }
  // Since this only decodes the certificate and doesn't attempt to build a
  // verified chain with it, the EndEntityOrCA parameter doesn't matter.
  BackCert backCert(certInput, EndEntityOrCA::MustBeEndEntity, nullptr);
  if (backCert.Init() != Success) {
    return false;
  }
  Input spkiInput = backCert.GetSubjectPublicKeyInfo();
  SECItem spkiItem = {siBuffer, const_cast<uint8_t*>(spkiInput.UnsafeGetData()),
                      spkiInput.GetLength()};
  UniqueCERTSubjectPublicKeyInfo spki(
      SECKEY_DecodeDERSubjectPublicKeyInfo(&spkiItem));
  if (!spki) {
    return false;
  }
  UniqueSECKEYPublicKey key(SECKEY_ExtractPublicKey(spki.get()));
  SECItem signatureItem = {siBuffer, const_cast<uint8_t*>(aSignature),
                           static_cast<unsigned int>(aSignatureLen)};
  rv = PK11_VerifyWithMechanism(key.get(), mechanism, &param, &signatureItem,
                                &hashItem, nullptr);
  if (rv != SECSuccess) {
    return false;
  }

  nsTArray<Span<const uint8_t>> collectedCerts;
  for (size_t i = 0; i < aCertChainLen; ++i) {
    Span<const uint8_t> cert(aCertChain[i], aCertsLen[i]);
    collectedCerts.AppendElement(std::move(cert));
  }

  Span<const uint8_t> certSpan = {aEECert, aEECertLen};
  nsresult nrv =
      VerifyCertificate(certSpan, aTrustedRoot, std::move(collectedCerts));
  bool result = true;
  if (NS_FAILED(nrv)) {
    result = false;
  }

  // Passing back the signing certificate in form of the DER cert.
  context->SetCert(certSpan);
  if (NS_FAILED(nrv)) {
    result = false;
  }

  return result;
}

nsresult VerifyAppManifest(SECOidTag aDigestToUse, nsCOMPtr<nsIZipReader> aZip,
                           nsTHashtable<nsCStringHashKey>& aIgnoredFiles,
                           const SECItem& aManifestBuffer) {
  // Allocate the I/O buffer only once per JAR, instead of once per entry, in
  // order to minimize malloc/free calls and in order to avoid fragmenting
  // memory.
  ScopedAutoSECItem buf(128 * 1024);

  nsTHashtable<nsCStringHashKey> items;

  nsresult rv =
      ParseMF(BitwiseCast<char*, unsigned char*>(aManifestBuffer.data), aZip,
              aDigestToUse, items, buf);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Verify every entry in the file.
  nsCOMPtr<nsIUTF8StringEnumerator> entries;
  rv = aZip->FindEntries(""_ns, getter_AddRefs(entries));
  if (NS_FAILED(rv)) {
    return rv;
  }
  if (!entries) {
    return NS_ERROR_UNEXPECTED;
  }

  for (;;) {
    bool hasMore;
    rv = entries->HasMore(&hasMore);
    NS_ENSURE_SUCCESS(rv, rv);

    if (!hasMore) {
      break;
    }

    nsAutoCString entryFilename;
    rv = entries->GetNext(entryFilename);
    NS_ENSURE_SUCCESS(rv, rv);

    MOZ_LOG(gPIPNSSLog, LogLevel::Debug,
            ("Verifying digests for %s", entryFilename.get()));

    if (entryFilename.Length() == 0) {
      return NS_ERROR_SIGNED_JAR_ENTRY_INVALID;
    }

    // The files that comprise the signature mechanism are not covered by the
    // signature. Ignore these files.
    if (aIgnoredFiles.Contains(entryFilename)) {
      continue;
    }

    // Entries with names that end in "/" are directory entries, which are not
    // signed.
    //
    // Since bug 1415991 we don't support unpacked JARs. The "/" entries are
    // therefore harmless.
    if (entryFilename.Last() == '/') {
      continue;
    }

    nsCStringHashKey* item = items.GetEntry(entryFilename);
    if (!item) {
      return NS_ERROR_SIGNED_JAR_UNSIGNED_ENTRY;
    }

    // Remove the item so we can check for leftover items later
    items.RemoveEntry(item);
  }

  // We verified that every entry that we require to be signed is signed. But,
  // were there any missing entries--that is, entries that are mentioned in the
  // manifest but missing from the archive?
  if (items.Count() != 0) {
    return NS_ERROR_SIGNED_JAR_ENTRY_MISSING;
  }

  return NS_OK;
}

// This corresponds to the preference "security.signed_app_signatures.policy".
// The lowest order bit determines which PKCS#7 algorithms are accepted.
// xxx_0_: SHA-1 and/or SHA-256 PKCS#7 allowed
// xxx_1_: SHA-256 PKCS#7 allowed
// The next two bits determine whether COSE is required and PKCS#7 is allowed
// x_00_x: COSE disabled, ignore files, PKCS#7 must verify
// x_01_x: COSE is verified if present, PKCS#7 must verify
// x_10_x: COSE is required, PKCS#7 must verify if present
// x_11_x: COSE is required, PKCS#7 disabled (fail when present)
class SignaturePolicy {
 public:
  explicit SignaturePolicy(int32_t preference)
      : mProcessCose(true),
        mCoseRequired(false),
        mProcessPK7(true),
        mPK7Required(true),
        mSHA1Allowed(true),
        mSHA256Allowed(true) {
    mCoseRequired = (preference & 0b100) != 0;
    mProcessCose = (preference & 0b110) != 0;
    mPK7Required = (preference & 0b100) == 0;
    mProcessPK7 = (preference & 0b110) != 0b110;
    if ((preference & 0b1) == 0) {
      mSHA1Allowed = true;
      mSHA256Allowed = true;
    } else {
      mSHA1Allowed = false;
      mSHA256Allowed = true;
    }
  }
  ~SignaturePolicy() = default;
  bool ProcessCOSE() { return mProcessCose; }
  bool COSERequired() { return mCoseRequired; }
  bool PK7Required() { return mPK7Required; }
  bool ProcessPK7() { return mProcessPK7; }
  bool IsPK7HashAllowed(SECOidTag aHashAlg) {
    if (aHashAlg == SEC_OID_SHA256 && mSHA256Allowed) {
      return true;
    }
    if (aHashAlg == SEC_OID_SHA1 && mSHA1Allowed) {
      return true;
    }
    return false;
  }

 private:
  bool mProcessCose;
  bool mCoseRequired;
  bool mProcessPK7;
  bool mPK7Required;
  bool mSHA1Allowed;
  bool mSHA256Allowed;
};

nsresult VerifyCOSESignature(AppTrustedRoot aTrustedRoot, nsIZipReader* aZip,
                             SignaturePolicy& aPolicy,
                             nsTHashtable<nsCStringHashKey>& aIgnoredFiles,
                             /* out */ bool& aVerified,
                             /* out */ nsTArray<uint8_t>& aCoseCertDER) {
  NS_ENSURE_ARG_POINTER(aZip);
  bool required = aPolicy.COSERequired();
  aVerified = false;

  // Read COSE signature file.
  nsAutoCString coseFilename;
  ScopedAutoSECItem coseBuffer;
  nsresult rv = FindAndLoadOneEntry(
      aZip, nsLiteralCString(JAR_COSE_SEARCH_STRING), coseFilename, coseBuffer);
  if (NS_FAILED(rv)) {
    return required ? NS_ERROR_SIGNED_JAR_WRONG_SIGNATURE : NS_OK;
  }

  // Verify COSE signature.
  nsAutoCString mfFilename;
  ScopedAutoSECItem manifestBuffer;
  rv = FindAndLoadOneEntry(aZip, nsLiteralCString(JAR_COSE_MF_SEARCH_STRING),
                           mfFilename, manifestBuffer);
  if (NS_FAILED(rv)) {
    return required ? NS_ERROR_SIGNED_JAR_WRONG_SIGNATURE : rv;
  }
  MOZ_ASSERT(manifestBuffer.len >= 1);
  MOZ_ASSERT(coseBuffer.len >= 1);
  CoseVerificationContext context(aTrustedRoot);
  bool coseVerification = verify_cose_signature_ffi(
      manifestBuffer.data, manifestBuffer.len - 1, coseBuffer.data,
      coseBuffer.len - 1, &context, CoseVerificationCallback);
  if (!coseVerification) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }
  // CoseVerificationCallback sets the context certificate to the first cert
  // it encounters.
  aCoseCertDER = context.TakeCert();

  // aIgnoredFiles contains the PKCS#7 manifest and signature files iff the
  // PKCS#7 verification was successful.
  aIgnoredFiles.PutEntry(mfFilename);
  aIgnoredFiles.PutEntry(coseFilename);
  rv = VerifyAppManifest(SEC_OID_SHA256, aZip, aIgnoredFiles, manifestBuffer);
  if (NS_FAILED(rv)) {
    return rv;
  }

  aVerified = true;
  return NS_OK;
}

nsresult VerifyPK7Signature(
    AppTrustedRoot aTrustedRoot, nsIZipReader* aZip, SignaturePolicy& aPolicy,
    /* out */ nsTHashtable<nsCStringHashKey>& aIgnoredFiles,
    /* out */ bool& aVerified,
    /* out */ nsTArray<uint8_t>& aSignerCert) {
  NS_ENSURE_ARG_POINTER(aZip);
  bool required = aPolicy.PK7Required();
  aVerified = false;

  // Signature (RSA) file
  nsAutoCString sigFilename;
  ScopedAutoSECItem sigBuffer;
  nsresult rv = FindAndLoadOneEntry(
      aZip, nsLiteralCString(JAR_RSA_SEARCH_STRING), sigFilename, sigBuffer);
  if (NS_FAILED(rv)) {
    return required ? NS_ERROR_SIGNED_JAR_NOT_SIGNED : NS_OK;
  }

  // Signature (SF) file
  nsAutoCString sfFilename;
  ScopedAutoSECItem sfBuffer;
  rv = FindAndLoadOneEntry(aZip, nsLiteralCString(JAR_SF_SEARCH_STRING),
                           sfFilename, sfBuffer);
  if (NS_FAILED(rv)) {
    return required ? NS_ERROR_SIGNED_JAR_MANIFEST_INVALID : NS_OK;
  }

  // Calculate both the SHA-1 and SHA-256 hashes of the signature file - we
  // don't know what algorithm the PKCS#7 signature used.
  nsTArray<uint8_t> sfCalculatedSHA1Digest;
  rv = Digest::DigestBuf(SEC_OID_SHA1, sfBuffer.data, sfBuffer.len - 1,
                         sfCalculatedSHA1Digest);
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsTArray<uint8_t> sfCalculatedSHA256Digest;
  rv = Digest::DigestBuf(SEC_OID_SHA256, sfBuffer.data, sfBuffer.len - 1,
                         sfCalculatedSHA256Digest);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Verify PKCS#7 signature.
  // If we get here, the signature has to verify even if PKCS#7 is not required.
  sigBuffer.type = siBuffer;
  SECOidTag digestToUse;
  rv = VerifySignature(aTrustedRoot, sigBuffer, sfCalculatedSHA1Digest,
                       sfCalculatedSHA256Digest, digestToUse, aSignerCert);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Check the digest used for the signature against the policy.
  if (!aPolicy.IsPK7HashAllowed(digestToUse)) {
    return NS_ERROR_SIGNED_JAR_WRONG_SIGNATURE;
  }

  nsAutoCString mfDigest;
  rv = ParseSF(BitwiseCast<char*, unsigned char*>(sfBuffer.data), digestToUse,
               mfDigest);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Read PK7 manifest (MF) file.
  ScopedAutoSECItem manifestBuffer;
  nsTArray<uint8_t> digestArray;
  nsAutoCString mfFilename;
  rv = FindAndLoadOneEntry(aZip, nsLiteralCString(JAR_MF_SEARCH_STRING),
                           mfFilename, manifestBuffer, digestToUse,
                           &digestArray);
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsDependentCSubstring calculatedDigest(
      BitwiseCast<char*, uint8_t*>(digestArray.Elements()),
      digestArray.Length());
  if (!mfDigest.Equals(calculatedDigest)) {
    return NS_ERROR_SIGNED_JAR_MANIFEST_INVALID;
  }

  // Verify PKCS7 manifest file hashes.
  aIgnoredFiles.PutEntry(sfFilename);
  aIgnoredFiles.PutEntry(sigFilename);
  aIgnoredFiles.PutEntry(mfFilename);
  rv = VerifyAppManifest(digestToUse, aZip, aIgnoredFiles, manifestBuffer);
  if (NS_FAILED(rv)) {
    aIgnoredFiles.Clear();
    return rv;
  }

  aVerified = true;
  return NS_OK;
}

nsresult OpenSignedAppFile(AppTrustedRoot aTrustedRoot, nsIFile* aJarFile,
                           SignaturePolicy aPolicy,
                           /* out, optional */ nsIZipReader** aZipReader,
                           /* out, optional */ nsIX509Cert** aSignerCert) {
  NS_ENSURE_ARG_POINTER(aJarFile);

  if (aZipReader) {
    *aZipReader = nullptr;
  }

  if (aSignerCert) {
    *aSignerCert = nullptr;
  }

  nsresult rv;

  static NS_DEFINE_CID(kZipReaderCID, NS_ZIPREADER_CID);
  nsCOMPtr<nsIZipReader> zip = do_CreateInstance(kZipReaderCID, &rv);
  NS_ENSURE_SUCCESS(rv, rv);

  rv = zip->Open(aJarFile);
  NS_ENSURE_SUCCESS(rv, rv);

  bool pk7Verified = false;
  bool coseVerified = false;
  nsTHashtable<nsCStringHashKey> ignoredFiles;
  nsTArray<uint8_t> pkcs7CertDER;
  nsTArray<uint8_t> coseCertDER;

  // First we have to verify the PKCS#7 signature if there is one.
  // This signature covers all files (except for the signature files itself),
  // including the COSE signature files. Only when this verification is
  // successful the respective files will be ignored in the subsequent COSE
  // signature verification.
  if (aPolicy.ProcessPK7()) {
    rv = VerifyPK7Signature(aTrustedRoot, zip, aPolicy, ignoredFiles,
                            pk7Verified, pkcs7CertDER);
    if (NS_FAILED(rv)) {
      return rv;
    }
  }

  if (aPolicy.ProcessCOSE()) {
    rv = VerifyCOSESignature(aTrustedRoot, zip, aPolicy, ignoredFiles,
                             coseVerified, coseCertDER);
    if (NS_FAILED(rv)) {
      return rv;
    }
  }

  if ((aPolicy.PK7Required() && !pk7Verified) ||
      (aPolicy.COSERequired() && !coseVerified)) {
    return NS_ERROR_SIGNED_JAR_WRONG_SIGNATURE;
  }

  // Return the reader to the caller if they want it
  if (aZipReader) {
    zip.forget(aZipReader);
  }

  // Return the signer's certificate to the reader if they want it.
  if (aSignerCert) {
    // The COSE certificate is authoritative.
    if (aPolicy.COSERequired() || !coseCertDER.IsEmpty()) {
      if (coseCertDER.IsEmpty()) {
        return NS_ERROR_FAILURE;
      }
      nsCOMPtr<nsIX509Cert> signerCert(
          new nsNSSCertificate(std::move(coseCertDER)));
      signerCert.forget(aSignerCert);
    } else {
      if (pkcs7CertDER.IsEmpty()) {
        return NS_ERROR_FAILURE;
      }
      nsCOMPtr<nsIX509Cert> signerCert(
          new nsNSSCertificate(std::move(pkcs7CertDER)));
      signerCert.forget(aSignerCert);
    }
  }

  return NS_OK;
}

class OpenSignedAppFileTask final : public CryptoTask {
 public:
  OpenSignedAppFileTask(AppTrustedRoot aTrustedRoot, nsIFile* aJarFile,
                        SignaturePolicy aPolicy,
                        nsIOpenSignedAppFileCallback* aCallback)
      : mTrustedRoot(aTrustedRoot),
        mJarFile(aJarFile),
        mPolicy(aPolicy),
        mCallback(new nsMainThreadPtrHolder<nsIOpenSignedAppFileCallback>(
            "OpenSignedAppFileTask::mCallback", aCallback)) {}

 private:
  virtual nsresult CalculateResult() override {
    return OpenSignedAppFile(mTrustedRoot, mJarFile, mPolicy,
                             getter_AddRefs(mZipReader),
                             getter_AddRefs(mSignerCert));
  }

  virtual void CallCallback(nsresult rv) override {
    (void)mCallback->OpenSignedAppFileFinished(rv, mZipReader, mSignerCert);
  }

  const AppTrustedRoot mTrustedRoot;
  const nsCOMPtr<nsIFile> mJarFile;
  const SignaturePolicy mPolicy;
  nsMainThreadPtrHandle<nsIOpenSignedAppFileCallback> mCallback;
  nsCOMPtr<nsIZipReader> mZipReader;  // out
  nsCOMPtr<nsIX509Cert> mSignerCert;  // out
};

static const int32_t sDefaultSignaturePolicy = 0b10;

}  // unnamed namespace

NS_IMETHODIMP
nsNSSCertificateDB::OpenSignedAppFileAsync(
    AppTrustedRoot aTrustedRoot, nsIFile* aJarFile,
    nsIOpenSignedAppFileCallback* aCallback) {
  NS_ENSURE_ARG_POINTER(aJarFile);
  NS_ENSURE_ARG_POINTER(aCallback);
  if (!NS_IsMainThread()) {
    return NS_ERROR_NOT_SAME_THREAD;
  }
  int32_t policyInt =
      Preferences::GetInt("security.signed_app_signatures.policy",
                          static_cast<int32_t>(sDefaultSignaturePolicy));
  SignaturePolicy policy(policyInt);
  RefPtr<OpenSignedAppFileTask> task(
      new OpenSignedAppFileTask(aTrustedRoot, aJarFile, policy, aCallback));
  return task->Dispatch();
}