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/* 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 "nsDataSignatureVerifier.h"

#include "ScopedNSSTypes.h"
#include "SharedCertVerifier.h"
#include "cms.h"
#include "cryptohi.h"
#include "keyhi.h"
#include "mozilla/Base64.h"
#include "mozilla/Casting.h"
#include "mozilla/Unused.h"
#include "nsCOMPtr.h"
#include "nsNSSComponent.h"
#include "nsString.h"
#include "pkix/pkixnss.h"
#include "pkix/pkixtypes.h"
#include "secerr.h"

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

SEC_ASN1_MKSUB(SECOID_AlgorithmIDTemplate)

NS_IMPL_ISUPPORTS(nsDataSignatureVerifier, nsIDataSignatureVerifier)

const SEC_ASN1Template CERT_SignatureDataTemplate[] =
{
    { SEC_ASN1_SEQUENCE,
        0, nullptr, sizeof(CERTSignedData) },
    { SEC_ASN1_INLINE | SEC_ASN1_XTRN,
        offsetof(CERTSignedData,signatureAlgorithm),
        SEC_ASN1_SUB(SECOID_AlgorithmIDTemplate), },
    { SEC_ASN1_BIT_STRING,
        offsetof(CERTSignedData,signature), },
    { 0, }
};

nsDataSignatureVerifier::~nsDataSignatureVerifier()
{
  nsNSSShutDownPreventionLock locker;
  if (isAlreadyShutDown()) {
    return;
  }

  shutdown(ShutdownCalledFrom::Object);
}

NS_IMETHODIMP
nsDataSignatureVerifier::VerifyData(const nsACString& aData,
                                    const nsACString& aSignature,
                                    const nsACString& aPublicKey,
                                    bool* _retval)
{
  NS_ENSURE_ARG_POINTER(_retval);

  nsNSSShutDownPreventionLock locker;
  if (isAlreadyShutDown()) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  // Allocate an arena to handle the majority of the allocations
  UniquePLArenaPool arena(PORT_NewArena(DER_DEFAULT_CHUNKSIZE));
  if (!arena) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  // Base 64 decode the key
  // For compatibility reasons we need to remove all whitespace first, since
  // Base64Decode() will not accept invalid characters.
  nsAutoCString b64KeyNoWhitespace(aPublicKey);
  b64KeyNoWhitespace.StripWhitespace();
  nsAutoCString key;
  nsresult rv = Base64Decode(b64KeyNoWhitespace, key);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Extract the public key from the data
  SECItem keyItem = {
    siBuffer,
    BitwiseCast<unsigned char*, const char*>(key.get()),
    key.Length(),
  };
  UniqueCERTSubjectPublicKeyInfo pki(
    SECKEY_DecodeDERSubjectPublicKeyInfo(&keyItem));
  if (!pki) {
    return NS_ERROR_FAILURE;
  }

  UniqueSECKEYPublicKey publicKey(SECKEY_ExtractPublicKey(pki.get()));
  if (!publicKey) {
    return NS_ERROR_FAILURE;
  }

  // Base 64 decode the signature
  // For compatibility reasons we need to remove all whitespace first, since
  // Base64Decode() will not accept invalid characters.
  nsAutoCString b64SignatureNoWhitespace(aSignature);
  b64SignatureNoWhitespace.StripWhitespace();
  nsAutoCString signature;
  rv = Base64Decode(b64SignatureNoWhitespace, signature);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Decode the signature and algorithm
  CERTSignedData sigData;
  PORT_Memset(&sigData, 0, sizeof(CERTSignedData));
  SECItem signatureItem = {
    siBuffer,
    BitwiseCast<unsigned char*, const char*>(signature.get()),
    signature.Length(),
  };
  SECStatus srv = SEC_QuickDERDecodeItem(arena.get(), &sigData,
                                         CERT_SignatureDataTemplate,
                                         &signatureItem);
  if (srv != SECSuccess) {
    return NS_ERROR_FAILURE;
  }

  // Perform the final verification
  DER_ConvertBitString(&(sigData.signature));
  srv = VFY_VerifyDataWithAlgorithmID(
    BitwiseCast<const unsigned char*, const char*>(
      PromiseFlatCString(aData).get()),
    aData.Length(), publicKey.get(), &(sigData.signature),
    &(sigData.signatureAlgorithm), nullptr, nullptr);

  *_retval = (srv == SECSuccess);

  return NS_OK;
}

namespace mozilla {

nsresult
VerifyCMSDetachedSignatureIncludingCertificate(
  const SECItem& buffer, const SECItem& detachedDigest,
  nsresult (*verifyCertificate)(CERTCertificate* cert, void* context,
                                void* pinArg),
  void* verifyCertificateContext, void* pinArg,
  const nsNSSShutDownPreventionLock& /*proofOfLock*/)
{
  // XXX: missing pinArg is tolerated.
  if (NS_WARN_IF(!buffer.data && buffer.len > 0) ||
      NS_WARN_IF(!detachedDigest.data && detachedDigest.len > 0) ||
      (!verifyCertificate) ||
      NS_WARN_IF(!verifyCertificateContext)) {
    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_ERROR_PROCESSING;
  }

  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;
  }

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

  // Set digest value.
  if (NSS_CMSSignedData_SetDigestValue(signedData, SEC_OID_SHA1,
                                       const_cast<SECItem*>(&detachedDigest))) {
    return NS_ERROR_CMS_VERIFY_BAD_DIGEST;
  }

  // Parse the certificates into CERTCertificate objects held in memory so
  // verifyCertificate will be able to find them during path building.
  UniqueCERTCertList certs(CERT_NewCertList());
  if (!certs) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  if (signedData->rawCerts) {
    for (size_t i = 0; signedData->rawCerts[i]; ++i) {
      UniqueCERTCertificate
        cert(CERT_NewTempCertificate(CERT_GetDefaultCertDB(),
                                     signedData->rawCerts[i], nullptr, false,
                                     true));
      // Skip certificates that fail to parse
      if (!cert) {
        continue;
      }

      if (CERT_AddCertToListTail(certs.get(), cert.get()) != SECSuccess) {
        return NS_ERROR_OUT_OF_MEMORY;
      }

      Unused << cert.release(); // Ownership transferred to the cert list.
    }
  }

  // Get the end-entity certificate.
  int numSigners = NSS_CMSSignedData_SignerInfoCount(signedData);
  if (NS_WARN_IF(numSigners != 1)) {
    return NS_ERROR_CMS_VERIFY_ERROR_PROCESSING;
  }
  // signer is non-owning.
  NSSCMSSignerInfo* signer = NSS_CMSSignedData_GetSignerInfo(signedData, 0);
  if (NS_WARN_IF(!signer)) {
    return NS_ERROR_CMS_VERIFY_ERROR_PROCESSING;
  }
  CERTCertificate* signerCert =
    NSS_CMSSignerInfo_GetSigningCertificate(signer, CERT_GetDefaultCertDB());
  if (!signerCert) {
    return NS_ERROR_CMS_VERIFY_ERROR_PROCESSING;
  }

  nsresult rv = verifyCertificate(signerCert, verifyCertificateContext, pinArg);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  // See NSS_CMSContentInfo_GetContentTypeOID, which isn't exported from NSS.
  SECOidData* contentTypeOidData =
    SECOID_FindOID(&signedData->contentInfo.contentType);
  if (!contentTypeOidData) {
    return NS_ERROR_CMS_VERIFY_ERROR_PROCESSING;
  }

  return MapSECStatus(NSS_CMSSignerInfo_Verify(signer,
                         const_cast<SECItem*>(&detachedDigest),
                         &contentTypeOidData->oid));
}

} // namespace mozilla

namespace {

struct VerifyCertificateContext
{
  nsCOMPtr<nsIX509Cert> signingCert;
  UniqueCERTCertList builtChain;
};

static nsresult
VerifyCertificate(CERTCertificate* cert, void* voidContext, void* pinArg)
{
  // XXX: missing pinArg is tolerated
  if (NS_WARN_IF(!cert) || NS_WARN_IF(!voidContext)) {
    return NS_ERROR_INVALID_ARG;
  }

  VerifyCertificateContext* context =
    static_cast<VerifyCertificateContext*>(voidContext);

  nsCOMPtr<nsIX509Cert> xpcomCert(nsNSSCertificate::Create(cert));
  if (!xpcomCert) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  context->signingCert = xpcomCert;

  RefPtr<SharedCertVerifier> certVerifier(GetDefaultCertVerifier());
  NS_ENSURE_TRUE(certVerifier, NS_ERROR_UNEXPECTED);

  mozilla::pkix::Result result =
    certVerifier->VerifyCert(cert,
                             certificateUsageObjectSigner,
                             Now(), pinArg,
                             nullptr, // hostname
                             context->builtChain);
  if (result != Success) {
    return GetXPCOMFromNSSError(MapResultToPRErrorCode(result));
  }

  return NS_OK;
}

} // namespace

NS_IMETHODIMP
nsDataSignatureVerifier::VerifySignature(const nsACString& aRSABuf,
                                         const nsACString& aPlaintext,
                                         int32_t* aErrorCode,
                                         nsIX509Cert** aSigningCert)
{
  if (!aErrorCode || !aSigningCert) {
    return NS_ERROR_INVALID_ARG;
  }

  nsNSSShutDownPreventionLock locker;
  if (isAlreadyShutDown()) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  *aErrorCode = VERIFY_ERROR_OTHER;
  *aSigningCert = nullptr;

  Digest digest;
  nsresult rv = digest.DigestBuf(
    SEC_OID_SHA1,
    BitwiseCast<const uint8_t*, const char*>(aPlaintext.BeginReading()),
    aPlaintext.Length());
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  SECItem buffer = {
    siBuffer,
    BitwiseCast<unsigned char*, const char*>(aRSABuf.BeginReading()),
    aRSABuf.Length(),
  };

  VerifyCertificateContext context;
  // XXX: pinArg is missing
  rv = VerifyCMSDetachedSignatureIncludingCertificate(buffer, digest.get(),
                                                      VerifyCertificate,
                                                      &context, nullptr, locker);
  if (NS_SUCCEEDED(rv)) {
    *aErrorCode = VERIFY_OK;
  } else if (NS_ERROR_GET_MODULE(rv) == NS_ERROR_MODULE_SECURITY) {
    if (rv == GetXPCOMFromNSSError(SEC_ERROR_UNKNOWN_ISSUER)) {
      *aErrorCode = VERIFY_ERROR_UNKNOWN_ISSUER;
    } else {
      *aErrorCode = VERIFY_ERROR_OTHER;
    }
    rv = NS_OK;
  }
  if (rv == NS_OK) {
    context.signingCert.forget(aSigningCert);
  }

  return rv;
}