src/controller/ExampleOperationalCredentialsIssuer.cpp - third_party/github/project-chip/connectedhomeip - Git at Google

 /*
  *
  *    Copyright (c) 2021-2022 Project CHIP Authors
  *    All rights reserved.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
  *    You may obtain a copy of the License at
  *
  *        http://www.apache.org/licenses/LICENSE-2.0
  *
  *    Unless required by applicable law or agreed to in writing, software
  *    distributed under the License is distributed on an "AS IS" BASIS,
  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *    See the License for the specific language governing permissions and
  *    limitations under the License.
  */

 #include <algorithm>
 #include <controller/ExampleOperationalCredentialsIssuer.h>
 #include <credentials/CHIPCert.h>
 #include <lib/core/TLV.h>
 #include <lib/support/CHIPMem.h>
 #include <lib/support/CodeUtils.h>
 #include <lib/support/PersistentStorageMacros.h>
 #include <lib/support/SafeInt.h>
 #include <lib/support/ScopedBuffer.h>
 #include <lib/support/TestGroupData.h>

 namespace chip {
 namespace Controller {

 constexpr const char kOperationalCredentialsIssuerKeypairStorage[]             = "ExampleOpCredsCAKey";
 constexpr const char kOperationalCredentialsIntermediateIssuerKeypairStorage[] = "ExampleOpCredsICAKey";
 constexpr const char kOperationalCredentialsRootCertificateStorage[]           = "ExampleCARootCert";
 constexpr const char kOperationalCredentialsIntermediateCertificateStorage[]   = "ExampleCAIntermediateCert";

 using namespace Credentials;
 using namespace Crypto;
 using namespace TLV;

 namespace {

 enum CertType : uint8_t
 {
     kRcac = 0,
     kIcac = 1,
     kNoc  = 2
 };

 CHIP_ERROR IssueX509Cert(uint32_t now, uint32_t validity, ChipDN issuerDn, ChipDN desiredDn, CertType certType, bool maximizeSize,
                          const Crypto::P256PublicKey & subjectPublicKey, Crypto::P256Keypair & issuerKeypair,
                          MutableByteSpan & outX509Cert)
 {
     constexpr size_t kDERCertFutureExtEncodingOverhead = 12;
     constexpr size_t kTLVCertFutureExtEncodingOverhead = kDERCertFutureExtEncodingOverhead + 5;
     constexpr size_t kMaxCertPaddingLength             = 200;
     constexpr size_t kTLVDesiredSize                   = kMaxCHIPCertLength;
     constexpr uint8_t sOID_Extension_SubjectAltName[]  = { 0x55, 0x1d, 0x11 };

     Platform::ScopedMemoryBuffer<uint8_t> derBuf;
     ReturnErrorCodeIf(!derBuf.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
     MutableByteSpan derSpan{ derBuf.Get(), kMaxDERCertLength };

     int64_t serialNumber = 1;

     switch (certType)
     {
     case CertType::kRcac: {
         X509CertRequestParams rcacRequest = { serialNumber, now, now + validity, desiredDn, desiredDn };
         ReturnErrorOnFailure(NewRootX509Cert(rcacRequest, issuerKeypair, derSpan));
         break;
     }
     case CertType::kIcac: {
         X509CertRequestParams icacRequest = { serialNumber, now, now + validity, desiredDn, issuerDn };
         ReturnErrorOnFailure(NewICAX509Cert(icacRequest, subjectPublicKey, issuerKeypair, derSpan));
         break;
     }
     case CertType::kNoc: {
         X509CertRequestParams nocRequest = { serialNumber, now, now + validity, desiredDn, issuerDn };
         ReturnErrorOnFailure(NewNodeOperationalX509Cert(nocRequest, subjectPublicKey, issuerKeypair, derSpan));
         break;
     }
     default:
         return CHIP_ERROR_INVALID_ARGUMENT;
     }

     if (maximizeSize)
     {
         Platform::ScopedMemoryBuffer<uint8_t> paddedTlvBuf;
         ReturnErrorCodeIf(!paddedTlvBuf.Alloc(kMaxCHIPCertLength + kMaxCertPaddingLength), CHIP_ERROR_NO_MEMORY);
         MutableByteSpan paddedTlvSpan{ paddedTlvBuf.Get(), kMaxCHIPCertLength + kMaxCertPaddingLength };
         ReturnErrorOnFailure(ConvertX509CertToChipCert(derSpan, paddedTlvSpan));

         Platform::ScopedMemoryBuffer<uint8_t> paddedDerBuf;
         ReturnErrorCodeIf(!paddedDerBuf.Alloc(kMaxDERCertLength + kMaxCertPaddingLength), CHIP_ERROR_NO_MEMORY);
         MutableByteSpan paddedDerSpan{ paddedDerBuf.Get(), kMaxDERCertLength + kMaxCertPaddingLength };

         Platform::ScopedMemoryBuffer<char> fillerBuf;
         ReturnErrorCodeIf(!fillerBuf.Alloc(kMaxCertPaddingLength), CHIP_ERROR_NO_MEMORY);
         memset(fillerBuf.Get(), 'A', kMaxCertPaddingLength);

         int derPaddingLen = static_cast<int>(kMaxDERCertLength - kDERCertFutureExtEncodingOverhead - derSpan.size());
         int tlvPaddingLen = static_cast<int>(kTLVDesiredSize - kTLVCertFutureExtEncodingOverhead - paddedTlvSpan.size());
         size_t paddingLen = 0;
         if (derPaddingLen >= 1 && tlvPaddingLen >= 1)
         {
             paddingLen = std::min(static_cast<size_t>(std::min(derPaddingLen, tlvPaddingLen)), kMaxCertPaddingLength);
         }

         for (; paddingLen > 0; paddingLen--)
         {
             paddedDerSpan = MutableByteSpan{ paddedDerBuf.Get(), kMaxDERCertLength + kMaxCertPaddingLength };
             paddedTlvSpan = MutableByteSpan{ paddedTlvBuf.Get(), kMaxCHIPCertLength + kMaxCertPaddingLength };

             Optional<FutureExtension> futureExt;
             FutureExtension ext = { ByteSpan(sOID_Extension_SubjectAltName),
                                     ByteSpan(reinterpret_cast<uint8_t *>(fillerBuf.Get()), paddingLen) };
             futureExt.SetValue(ext);

             switch (certType)
             {
             case CertType::kRcac: {
                 X509CertRequestParams rcacRequest = { serialNumber, now, now + validity, desiredDn, desiredDn, futureExt };
                 ReturnErrorOnFailure(NewRootX509Cert(rcacRequest, issuerKeypair, paddedDerSpan));
                 break;
             }
             case CertType::kIcac: {
                 X509CertRequestParams icacRequest = { serialNumber, now, now + validity, desiredDn, issuerDn, futureExt };
                 ReturnErrorOnFailure(NewICAX509Cert(icacRequest, subjectPublicKey, issuerKeypair, paddedDerSpan));
                 break;
             }
             case CertType::kNoc: {
                 X509CertRequestParams nocRequest = { serialNumber, now, now + validity, desiredDn, issuerDn, futureExt };
                 ReturnErrorOnFailure(NewNodeOperationalX509Cert(nocRequest, subjectPublicKey, issuerKeypair, paddedDerSpan));
                 break;
             }
             default:
                 return CHIP_ERROR_INVALID_ARGUMENT;
             }

             ReturnErrorOnFailure(ConvertX509CertToChipCert(paddedDerSpan, paddedTlvSpan));

             if (paddedDerSpan.size() <= kMaxDERCertLength && paddedTlvSpan.size() <= kMaxCHIPCertLength)
             {
                 ChipLogProgress(Controller, "Generated maximized certificate with %u DER bytes, %u TLV bytes",
                                 static_cast<unsigned>(paddedDerSpan.size()), static_cast<unsigned>(paddedTlvSpan.size()));
                 return CopySpanToMutableSpan(paddedDerSpan, outX509Cert);
             }
         }
     }

     return CopySpanToMutableSpan(derSpan, outX509Cert);
 }

 } // namespace

 CHIP_ERROR ExampleOperationalCredentialsIssuer::Initialize(PersistentStorageDelegate & storage)
 {
     using namespace ASN1;
     ASN1UniversalTime effectiveTime;
     CHIP_ERROR err;

     // Initializing the default start validity to start of 2021. The default validity duration is 10 years.
     CHIP_ZERO_AT(effectiveTime);
     effectiveTime.Year  = 2021;
     effectiveTime.Month = 1;
     effectiveTime.Day   = 1;
     ReturnErrorOnFailure(ASN1ToChipEpochTime(effectiveTime, mNow));

     Crypto::P256SerializedKeypair serializedKey;
     {
         // Scope for keySize, because we use it as an in/out param.
         uint16_t keySize = static_cast<uint16_t>(serializedKey.Capacity());

         PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIssuerKeypairStorage, key,
                           err = storage.SyncGetKeyValue(key, serializedKey.Bytes(), keySize));
         serializedKey.SetLength(keySize);
     }

     if (err != CHIP_NO_ERROR)
     {
         ChipLogProgress(Controller, "Couldn't get %s from storage: %s", kOperationalCredentialsIssuerKeypairStorage, ErrorStr(err));
         // Storage doesn't have an existing keypair. Let's create one and add it to the storage.
         ReturnErrorOnFailure(mIssuer.Initialize(Crypto::ECPKeyTarget::ECDSA));
         ReturnErrorOnFailure(mIssuer.Serialize(serializedKey));

         PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIssuerKeypairStorage, key,
                           ReturnErrorOnFailure(
                               storage.SyncSetKeyValue(key, serializedKey.Bytes(), static_cast<uint16_t>(serializedKey.Length()))));
     }
     else
     {
         // Use the keypair from the storage
         ReturnErrorOnFailure(mIssuer.Deserialize(serializedKey));
     }

     {
         // Scope for keySize, because we use it as an in/out param.
         uint16_t keySize = static_cast<uint16_t>(serializedKey.Capacity());

         PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateIssuerKeypairStorage, key,
                           err = storage.SyncGetKeyValue(key, serializedKey.Bytes(), keySize));
         serializedKey.SetLength(keySize);
     }

     if (err != CHIP_NO_ERROR)
     {
         ChipLogProgress(Controller, "Couldn't get %s from storage: %s", kOperationalCredentialsIntermediateIssuerKeypairStorage,
                         ErrorStr(err));
         // Storage doesn't have an existing keypair. Let's create one and add it to the storage.
         ReturnErrorOnFailure(mIntermediateIssuer.Initialize(Crypto::ECPKeyTarget::ECDSA));
         ReturnErrorOnFailure(mIntermediateIssuer.Serialize(serializedKey));

         PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateIssuerKeypairStorage, key,
                           ReturnErrorOnFailure(
                               storage.SyncSetKeyValue(key, serializedKey.Bytes(), static_cast<uint16_t>(serializedKey.Length()))));
     }
     else
     {
         // Use the keypair from the storage
         ReturnErrorOnFailure(mIntermediateIssuer.Deserialize(serializedKey));
     }

     mStorage     = &storage;
     mInitialized = true;
     return CHIP_NO_ERROR;
 }

 CHIP_ERROR ExampleOperationalCredentialsIssuer::GenerateNOCChainAfterValidation(NodeId nodeId, FabricId fabricId,
                                                                                 const CATValues & cats,
                                                                                 const Crypto::P256PublicKey & pubkey,
                                                                                 MutableByteSpan & rcac, MutableByteSpan & icac,
                                                                                 MutableByteSpan & noc)
 {
     ChipDN rcac_dn;
     CHIP_ERROR err      = CHIP_NO_ERROR;
     uint16_t rcacBufLen = static_cast<uint16_t>(std::min(rcac.size(), static_cast<size_t>(UINT16_MAX)));
     PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsRootCertificateStorage, key,
                       err = mStorage->SyncGetKeyValue(key, rcac.data(), rcacBufLen));
     // Always regenerate RCAC on maximally sized certs. The keys remain the same, so everything is fine.
     if (mUseMaximallySizedCerts)
     {
         err = CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND;
     }

     if (err == CHIP_NO_ERROR)
     {
         uint64_t rcacId;
         // Found root certificate in the storage.
         rcac.reduce_size(rcacBufLen);
         ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(rcac, rcac_dn));
         ReturnErrorOnFailure(rcac_dn.GetCertChipId(rcacId));
         VerifyOrReturnError(rcacId == mIssuerId, CHIP_ERROR_INTERNAL);
     }
     // If root certificate not found in the storage, generate new root certificate.
     else
     {
         ReturnErrorOnFailure(rcac_dn.AddAttribute_MatterRCACId(mIssuerId));

         ChipLogProgress(Controller, "Generating RCAC");
         ReturnErrorOnFailure(IssueX509Cert(mNow, mValidity, rcac_dn, rcac_dn, CertType::kRcac, mUseMaximallySizedCerts,
                                            mIssuer.Pubkey(), mIssuer, rcac));
         VerifyOrReturnError(CanCastTo<uint16_t>(rcac.size()), CHIP_ERROR_INTERNAL);

         // Re-extract DN based on final generated cert
         rcac_dn = ChipDN{};
         ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(rcac, rcac_dn));

         PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsRootCertificateStorage, key,
                           ReturnErrorOnFailure(mStorage->SyncSetKeyValue(key, rcac.data(), static_cast<uint16_t>(rcac.size()))));
     }

     ChipDN icac_dn;
     uint16_t icacBufLen = static_cast<uint16_t>(std::min(icac.size(), static_cast<size_t>(UINT16_MAX)));
     PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateCertificateStorage, key,
                       err = mStorage->SyncGetKeyValue(key, icac.data(), icacBufLen));
     // Always regenerate ICAC on maximally sized certs. The keys remain the same, so everything is fine.
     if (mUseMaximallySizedCerts)
     {
         err = CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND;
     }
     if (err == CHIP_NO_ERROR)
     {
         uint64_t icacId;
         // Found intermediate certificate in the storage.
         icac.reduce_size(icacBufLen);
         ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(icac, icac_dn));
         ReturnErrorOnFailure(icac_dn.GetCertChipId(icacId));
         VerifyOrReturnError(icacId == mIntermediateIssuerId, CHIP_ERROR_INTERNAL);
     }
     // If intermediate certificate not found in the storage, generate new intermediate certificate.
     else
     {
         ReturnErrorOnFailure(icac_dn.AddAttribute_MatterICACId(mIntermediateIssuerId));

         ChipLogProgress(Controller, "Generating ICAC");
         ReturnErrorOnFailure(IssueX509Cert(mNow, mValidity, rcac_dn, icac_dn, CertType::kIcac, mUseMaximallySizedCerts,
                                            mIntermediateIssuer.Pubkey(), mIssuer, icac));
         VerifyOrReturnError(CanCastTo<uint16_t>(icac.size()), CHIP_ERROR_INTERNAL);

         // Re-extract DN based on final generated cert
         icac_dn = ChipDN{};
         ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(icac, icac_dn));

         PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateCertificateStorage, key,
                           ReturnErrorOnFailure(mStorage->SyncSetKeyValue(key, icac.data(), static_cast<uint16_t>(icac.size()))));
     }

     ChipDN noc_dn;
     ReturnErrorOnFailure(noc_dn.AddAttribute_MatterFabricId(fabricId));
     ReturnErrorOnFailure(noc_dn.AddAttribute_MatterNodeId(nodeId));
     ReturnErrorOnFailure(noc_dn.AddCATs(cats));

     ChipLogProgress(Controller, "Generating NOC");
     return IssueX509Cert(mNow, mValidity, icac_dn, noc_dn, CertType::kNoc, mUseMaximallySizedCerts, pubkey, mIntermediateIssuer,
                          noc);
 }

 CHIP_ERROR ExampleOperationalCredentialsIssuer::GenerateNOCChain(const ByteSpan & csrElements, const ByteSpan & csrNonce,
                                                                  const ByteSpan & attestationSignature,
                                                                  const ByteSpan & attestationChallenge, const ByteSpan & DAC,
                                                                  const ByteSpan & PAI,
                                                                  Callback::Callback<OnNOCChainGeneration> * onCompletion)
 {
     VerifyOrReturnError(mInitialized, CHIP_ERROR_WELL_UNINITIALIZED);
     // At this point, Credential issuer may wish to validate the CSR information
     (void) attestationChallenge;
     (void) csrNonce;

     NodeId assignedId;
     if (mNodeIdRequested)
     {
         assignedId       = mNextRequestedNodeId;
         mNodeIdRequested = false;
     }
     else
     {
         assignedId = mNextAvailableNodeId++;
     }

     ChipLogProgress(Controller, "Verifying Certificate Signing Request");
     TLVReader reader;
     reader.Init(csrElements);

     if (reader.GetType() == kTLVType_NotSpecified)
     {
         ReturnErrorOnFailure(reader.Next());
     }

     VerifyOrReturnError(reader.GetType() == kTLVType_Structure, CHIP_ERROR_WRONG_TLV_TYPE);
     VerifyOrReturnError(reader.GetTag() == AnonymousTag(), CHIP_ERROR_UNEXPECTED_TLV_ELEMENT);

     TLVType containerType;
     ReturnErrorOnFailure(reader.EnterContainer(containerType));
     ReturnErrorOnFailure(reader.Next(kTLVType_ByteString, TLV::ContextTag(1)));

     ByteSpan csr(reader.GetReadPoint(), reader.GetLength());
     reader.ExitContainer(containerType);

     P256PublicKey pubkey;
     ReturnErrorOnFailure(VerifyCertificateSigningRequest(csr.data(), csr.size(), pubkey));

     chip::Platform::ScopedMemoryBuffer<uint8_t> noc;
     ReturnErrorCodeIf(!noc.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
     MutableByteSpan nocSpan(noc.Get(), kMaxDERCertLength);

     chip::Platform::ScopedMemoryBuffer<uint8_t> icac;
     ReturnErrorCodeIf(!icac.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
     MutableByteSpan icacSpan(icac.Get(), kMaxDERCertLength);

     chip::Platform::ScopedMemoryBuffer<uint8_t> rcac;
     ReturnErrorCodeIf(!rcac.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
     MutableByteSpan rcacSpan(rcac.Get(), kMaxDERCertLength);

     ReturnErrorOnFailure(
         GenerateNOCChainAfterValidation(assignedId, mNextFabricId, mNextCATs, pubkey, rcacSpan, icacSpan, nocSpan));

     // TODO(#13825): Should always generate some IPK. Using a temporary fixed value until APIs are plumbed in to set it end-to-end
     // TODO: Force callers to set IPK if used before GenerateNOCChain will succeed.
     ByteSpan defaultIpkSpan = chip::GroupTesting::DefaultIpkValue::GetDefaultIpk();

     // The below static assert validates a key assumption in types used (needed for public API conformance)
     static_assert(CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES == kAES_CCM128_Key_Length, "IPK span sizing must match");

     // Prepare IPK to be sent back. A more fully-fledged operational credentials delegate
     // would obtain a suitable key per fabric.
     uint8_t ipkValue[CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES];
     Crypto::IdentityProtectionKeySpan ipkSpan(ipkValue);

     ReturnErrorCodeIf(defaultIpkSpan.size() != sizeof(ipkValue), CHIP_ERROR_INTERNAL);
     memcpy(&ipkValue[0], defaultIpkSpan.data(), defaultIpkSpan.size());

     // Callback onto commissioner.
     ChipLogProgress(Controller, "Providing certificate chain to the commissioner");
     onCompletion->mCall(onCompletion->mContext, CHIP_NO_ERROR, nocSpan, icacSpan, rcacSpan, MakeOptional(ipkSpan),
                         Optional<NodeId>());
     return CHIP_NO_ERROR;
 }

 CHIP_ERROR ExampleOperationalCredentialsIssuer::GetRandomOperationalNodeId(NodeId * aNodeId)
 {
     for (int i = 0; i < 10; ++i)
     {
         CHIP_ERROR err = DRBG_get_bytes(reinterpret_cast<uint8_t *>(aNodeId), sizeof(*aNodeId));
         if (err != CHIP_NO_ERROR)
         {
             return err;
         }

         if (IsOperationalNodeId(*aNodeId))
         {
             return CHIP_NO_ERROR;
         }
     }

     // Terrible, universe-ending luck (chances are 1 in 2^280 or so here, if our
     // DRBG is good).
     return CHIP_ERROR_INTERNAL;
 }

 } // namespace Controller
 } // namespace chip
	/*
	*
	* Copyright (c) 2021-2022 Project CHIP Authors
	* All rights reserved.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <algorithm>
	#include <controller/ExampleOperationalCredentialsIssuer.h>
	#include <credentials/CHIPCert.h>
	#include <lib/core/TLV.h>
	#include <lib/support/CHIPMem.h>
	#include <lib/support/CodeUtils.h>
	#include <lib/support/PersistentStorageMacros.h>
	#include <lib/support/SafeInt.h>
	#include <lib/support/ScopedBuffer.h>
	#include <lib/support/TestGroupData.h>

	namespace chip {
	namespace Controller {

	constexpr const char kOperationalCredentialsIssuerKeypairStorage[] = "ExampleOpCredsCAKey";
	constexpr const char kOperationalCredentialsIntermediateIssuerKeypairStorage[] = "ExampleOpCredsICAKey";
	constexpr const char kOperationalCredentialsRootCertificateStorage[] = "ExampleCARootCert";
	constexpr const char kOperationalCredentialsIntermediateCertificateStorage[] = "ExampleCAIntermediateCert";

	using namespace Credentials;
	using namespace Crypto;
	using namespace TLV;

	namespace {

	enum CertType : uint8_t
	{
	kRcac = 0,
	kIcac = 1,
	kNoc = 2
	};

	CHIP_ERROR IssueX509Cert(uint32_t now, uint32_t validity, ChipDN issuerDn, ChipDN desiredDn, CertType certType, bool maximizeSize,
	const Crypto::P256PublicKey & subjectPublicKey, Crypto::P256Keypair & issuerKeypair,
	MutableByteSpan & outX509Cert)
	{
	constexpr size_t kDERCertFutureExtEncodingOverhead = 12;
	constexpr size_t kTLVCertFutureExtEncodingOverhead = kDERCertFutureExtEncodingOverhead + 5;
	constexpr size_t kMaxCertPaddingLength = 200;
	constexpr size_t kTLVDesiredSize = kMaxCHIPCertLength;
	constexpr uint8_t sOID_Extension_SubjectAltName[] = { 0x55, 0x1d, 0x11 };

	Platform::ScopedMemoryBuffer<uint8_t> derBuf;
	ReturnErrorCodeIf(!derBuf.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
	MutableByteSpan derSpan{ derBuf.Get(), kMaxDERCertLength };

	int64_t serialNumber = 1;

	switch (certType)
	{
	case CertType::kRcac: {
	X509CertRequestParams rcacRequest = { serialNumber, now, now + validity, desiredDn, desiredDn };
	ReturnErrorOnFailure(NewRootX509Cert(rcacRequest, issuerKeypair, derSpan));
	break;
	}
	case CertType::kIcac: {
	X509CertRequestParams icacRequest = { serialNumber, now, now + validity, desiredDn, issuerDn };
	ReturnErrorOnFailure(NewICAX509Cert(icacRequest, subjectPublicKey, issuerKeypair, derSpan));
	break;
	}
	case CertType::kNoc: {
	X509CertRequestParams nocRequest = { serialNumber, now, now + validity, desiredDn, issuerDn };
	ReturnErrorOnFailure(NewNodeOperationalX509Cert(nocRequest, subjectPublicKey, issuerKeypair, derSpan));
	break;
	}
	default:
	return CHIP_ERROR_INVALID_ARGUMENT;
	}

	if (maximizeSize)
	{
	Platform::ScopedMemoryBuffer<uint8_t> paddedTlvBuf;
	ReturnErrorCodeIf(!paddedTlvBuf.Alloc(kMaxCHIPCertLength + kMaxCertPaddingLength), CHIP_ERROR_NO_MEMORY);
	MutableByteSpan paddedTlvSpan{ paddedTlvBuf.Get(), kMaxCHIPCertLength + kMaxCertPaddingLength };
	ReturnErrorOnFailure(ConvertX509CertToChipCert(derSpan, paddedTlvSpan));

	Platform::ScopedMemoryBuffer<uint8_t> paddedDerBuf;
	ReturnErrorCodeIf(!paddedDerBuf.Alloc(kMaxDERCertLength + kMaxCertPaddingLength), CHIP_ERROR_NO_MEMORY);
	MutableByteSpan paddedDerSpan{ paddedDerBuf.Get(), kMaxDERCertLength + kMaxCertPaddingLength };

	Platform::ScopedMemoryBuffer<char> fillerBuf;
	ReturnErrorCodeIf(!fillerBuf.Alloc(kMaxCertPaddingLength), CHIP_ERROR_NO_MEMORY);
	memset(fillerBuf.Get(), 'A', kMaxCertPaddingLength);

	int derPaddingLen = static_cast<int>(kMaxDERCertLength - kDERCertFutureExtEncodingOverhead - derSpan.size());
	int tlvPaddingLen = static_cast<int>(kTLVDesiredSize - kTLVCertFutureExtEncodingOverhead - paddedTlvSpan.size());
	size_t paddingLen = 0;
	if (derPaddingLen >= 1 && tlvPaddingLen >= 1)
	{
	paddingLen = std::min(static_cast<size_t>(std::min(derPaddingLen, tlvPaddingLen)), kMaxCertPaddingLength);
	}

	for (; paddingLen > 0; paddingLen--)
	{
	paddedDerSpan = MutableByteSpan{ paddedDerBuf.Get(), kMaxDERCertLength + kMaxCertPaddingLength };
	paddedTlvSpan = MutableByteSpan{ paddedTlvBuf.Get(), kMaxCHIPCertLength + kMaxCertPaddingLength };

	Optional<FutureExtension> futureExt;
	FutureExtension ext = { ByteSpan(sOID_Extension_SubjectAltName),
	ByteSpan(reinterpret_cast<uint8_t *>(fillerBuf.Get()), paddingLen) };
	futureExt.SetValue(ext);

	switch (certType)
	{
	case CertType::kRcac: {
	X509CertRequestParams rcacRequest = { serialNumber, now, now + validity, desiredDn, desiredDn, futureExt };
	ReturnErrorOnFailure(NewRootX509Cert(rcacRequest, issuerKeypair, paddedDerSpan));
	break;
	}
	case CertType::kIcac: {
	X509CertRequestParams icacRequest = { serialNumber, now, now + validity, desiredDn, issuerDn, futureExt };
	ReturnErrorOnFailure(NewICAX509Cert(icacRequest, subjectPublicKey, issuerKeypair, paddedDerSpan));
	break;
	}
	case CertType::kNoc: {
	X509CertRequestParams nocRequest = { serialNumber, now, now + validity, desiredDn, issuerDn, futureExt };
	ReturnErrorOnFailure(NewNodeOperationalX509Cert(nocRequest, subjectPublicKey, issuerKeypair, paddedDerSpan));
	break;
	}
	default:
	return CHIP_ERROR_INVALID_ARGUMENT;
	}

	ReturnErrorOnFailure(ConvertX509CertToChipCert(paddedDerSpan, paddedTlvSpan));

	if (paddedDerSpan.size() <= kMaxDERCertLength && paddedTlvSpan.size() <= kMaxCHIPCertLength)
	{
	ChipLogProgress(Controller, "Generated maximized certificate with %u DER bytes, %u TLV bytes",
	static_cast<unsigned>(paddedDerSpan.size()), static_cast<unsigned>(paddedTlvSpan.size()));
	return CopySpanToMutableSpan(paddedDerSpan, outX509Cert);
	}
	}
	}

	return CopySpanToMutableSpan(derSpan, outX509Cert);
	}

	} // namespace

	CHIP_ERROR ExampleOperationalCredentialsIssuer::Initialize(PersistentStorageDelegate & storage)
	{
	using namespace ASN1;
	ASN1UniversalTime effectiveTime;
	CHIP_ERROR err;

	// Initializing the default start validity to start of 2021. The default validity duration is 10 years.
	CHIP_ZERO_AT(effectiveTime);
	effectiveTime.Year = 2021;
	effectiveTime.Month = 1;
	effectiveTime.Day = 1;
	ReturnErrorOnFailure(ASN1ToChipEpochTime(effectiveTime, mNow));

	Crypto::P256SerializedKeypair serializedKey;
	{
	// Scope for keySize, because we use it as an in/out param.
	uint16_t keySize = static_cast<uint16_t>(serializedKey.Capacity());

	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIssuerKeypairStorage, key,
	err = storage.SyncGetKeyValue(key, serializedKey.Bytes(), keySize));
	serializedKey.SetLength(keySize);
	}

	if (err != CHIP_NO_ERROR)
	{
	ChipLogProgress(Controller, "Couldn't get %s from storage: %s", kOperationalCredentialsIssuerKeypairStorage, ErrorStr(err));
	// Storage doesn't have an existing keypair. Let's create one and add it to the storage.
	ReturnErrorOnFailure(mIssuer.Initialize(Crypto::ECPKeyTarget::ECDSA));
	ReturnErrorOnFailure(mIssuer.Serialize(serializedKey));

	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIssuerKeypairStorage, key,
	ReturnErrorOnFailure(
	storage.SyncSetKeyValue(key, serializedKey.Bytes(), static_cast<uint16_t>(serializedKey.Length()))));
	}
	else
	{
	// Use the keypair from the storage
	ReturnErrorOnFailure(mIssuer.Deserialize(serializedKey));
	}

	{
	// Scope for keySize, because we use it as an in/out param.
	uint16_t keySize = static_cast<uint16_t>(serializedKey.Capacity());

	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateIssuerKeypairStorage, key,
	err = storage.SyncGetKeyValue(key, serializedKey.Bytes(), keySize));
	serializedKey.SetLength(keySize);
	}

	if (err != CHIP_NO_ERROR)
	{
	ChipLogProgress(Controller, "Couldn't get %s from storage: %s", kOperationalCredentialsIntermediateIssuerKeypairStorage,
	ErrorStr(err));
	// Storage doesn't have an existing keypair. Let's create one and add it to the storage.
	ReturnErrorOnFailure(mIntermediateIssuer.Initialize(Crypto::ECPKeyTarget::ECDSA));
	ReturnErrorOnFailure(mIntermediateIssuer.Serialize(serializedKey));

	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateIssuerKeypairStorage, key,
	ReturnErrorOnFailure(
	storage.SyncSetKeyValue(key, serializedKey.Bytes(), static_cast<uint16_t>(serializedKey.Length()))));
	}
	else
	{
	// Use the keypair from the storage
	ReturnErrorOnFailure(mIntermediateIssuer.Deserialize(serializedKey));
	}

	mStorage = &storage;
	mInitialized = true;
	return CHIP_NO_ERROR;
	}

	CHIP_ERROR ExampleOperationalCredentialsIssuer::GenerateNOCChainAfterValidation(NodeId nodeId, FabricId fabricId,
	const CATValues & cats,
	const Crypto::P256PublicKey & pubkey,
	MutableByteSpan & rcac, MutableByteSpan & icac,
	MutableByteSpan & noc)
	{
	ChipDN rcac_dn;
	CHIP_ERROR err = CHIP_NO_ERROR;
	uint16_t rcacBufLen = static_cast<uint16_t>(std::min(rcac.size(), static_cast<size_t>(UINT16_MAX)));
	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsRootCertificateStorage, key,
	err = mStorage->SyncGetKeyValue(key, rcac.data(), rcacBufLen));
	// Always regenerate RCAC on maximally sized certs. The keys remain the same, so everything is fine.
	if (mUseMaximallySizedCerts)
	{
	err = CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND;
	}

	if (err == CHIP_NO_ERROR)
	{
	uint64_t rcacId;
	// Found root certificate in the storage.
	rcac.reduce_size(rcacBufLen);
	ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(rcac, rcac_dn));
	ReturnErrorOnFailure(rcac_dn.GetCertChipId(rcacId));
	VerifyOrReturnError(rcacId == mIssuerId, CHIP_ERROR_INTERNAL);
	}
	// If root certificate not found in the storage, generate new root certificate.
	else
	{
	ReturnErrorOnFailure(rcac_dn.AddAttribute_MatterRCACId(mIssuerId));

	ChipLogProgress(Controller, "Generating RCAC");
	ReturnErrorOnFailure(IssueX509Cert(mNow, mValidity, rcac_dn, rcac_dn, CertType::kRcac, mUseMaximallySizedCerts,
	mIssuer.Pubkey(), mIssuer, rcac));
	VerifyOrReturnError(CanCastTo<uint16_t>(rcac.size()), CHIP_ERROR_INTERNAL);

	// Re-extract DN based on final generated cert
	rcac_dn = ChipDN{};
	ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(rcac, rcac_dn));

	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsRootCertificateStorage, key,
	ReturnErrorOnFailure(mStorage->SyncSetKeyValue(key, rcac.data(), static_cast<uint16_t>(rcac.size()))));
	}

	ChipDN icac_dn;
	uint16_t icacBufLen = static_cast<uint16_t>(std::min(icac.size(), static_cast<size_t>(UINT16_MAX)));
	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateCertificateStorage, key,
	err = mStorage->SyncGetKeyValue(key, icac.data(), icacBufLen));
	// Always regenerate ICAC on maximally sized certs. The keys remain the same, so everything is fine.
	if (mUseMaximallySizedCerts)
	{
	err = CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND;
	}
	if (err == CHIP_NO_ERROR)
	{
	uint64_t icacId;
	// Found intermediate certificate in the storage.
	icac.reduce_size(icacBufLen);
	ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(icac, icac_dn));
	ReturnErrorOnFailure(icac_dn.GetCertChipId(icacId));
	VerifyOrReturnError(icacId == mIntermediateIssuerId, CHIP_ERROR_INTERNAL);
	}
	// If intermediate certificate not found in the storage, generate new intermediate certificate.
	else
	{
	ReturnErrorOnFailure(icac_dn.AddAttribute_MatterICACId(mIntermediateIssuerId));

	ChipLogProgress(Controller, "Generating ICAC");
	ReturnErrorOnFailure(IssueX509Cert(mNow, mValidity, rcac_dn, icac_dn, CertType::kIcac, mUseMaximallySizedCerts,
	mIntermediateIssuer.Pubkey(), mIssuer, icac));
	VerifyOrReturnError(CanCastTo<uint16_t>(icac.size()), CHIP_ERROR_INTERNAL);

	// Re-extract DN based on final generated cert
	icac_dn = ChipDN{};
	ReturnErrorOnFailure(ExtractSubjectDNFromX509Cert(icac, icac_dn));

	PERSISTENT_KEY_OP(mIndex, kOperationalCredentialsIntermediateCertificateStorage, key,
	ReturnErrorOnFailure(mStorage->SyncSetKeyValue(key, icac.data(), static_cast<uint16_t>(icac.size()))));
	}

	ChipDN noc_dn;
	ReturnErrorOnFailure(noc_dn.AddAttribute_MatterFabricId(fabricId));
	ReturnErrorOnFailure(noc_dn.AddAttribute_MatterNodeId(nodeId));
	ReturnErrorOnFailure(noc_dn.AddCATs(cats));

	ChipLogProgress(Controller, "Generating NOC");
	return IssueX509Cert(mNow, mValidity, icac_dn, noc_dn, CertType::kNoc, mUseMaximallySizedCerts, pubkey, mIntermediateIssuer,
	noc);
	}

	CHIP_ERROR ExampleOperationalCredentialsIssuer::GenerateNOCChain(const ByteSpan & csrElements, const ByteSpan & csrNonce,
	const ByteSpan & attestationSignature,
	const ByteSpan & attestationChallenge, const ByteSpan & DAC,
	const ByteSpan & PAI,
	Callback::Callback<OnNOCChainGeneration> * onCompletion)
	{
	VerifyOrReturnError(mInitialized, CHIP_ERROR_WELL_UNINITIALIZED);
	// At this point, Credential issuer may wish to validate the CSR information
	(void) attestationChallenge;
	(void) csrNonce;

	NodeId assignedId;
	if (mNodeIdRequested)
	{
	assignedId = mNextRequestedNodeId;
	mNodeIdRequested = false;
	}
	else
	{
	assignedId = mNextAvailableNodeId++;
	}

	ChipLogProgress(Controller, "Verifying Certificate Signing Request");
	TLVReader reader;
	reader.Init(csrElements);

	if (reader.GetType() == kTLVType_NotSpecified)
	{
	ReturnErrorOnFailure(reader.Next());
	}

	VerifyOrReturnError(reader.GetType() == kTLVType_Structure, CHIP_ERROR_WRONG_TLV_TYPE);
	VerifyOrReturnError(reader.GetTag() == AnonymousTag(), CHIP_ERROR_UNEXPECTED_TLV_ELEMENT);

	TLVType containerType;
	ReturnErrorOnFailure(reader.EnterContainer(containerType));
	ReturnErrorOnFailure(reader.Next(kTLVType_ByteString, TLV::ContextTag(1)));

	ByteSpan csr(reader.GetReadPoint(), reader.GetLength());
	reader.ExitContainer(containerType);

	P256PublicKey pubkey;
	ReturnErrorOnFailure(VerifyCertificateSigningRequest(csr.data(), csr.size(), pubkey));

	chip::Platform::ScopedMemoryBuffer<uint8_t> noc;
	ReturnErrorCodeIf(!noc.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
	MutableByteSpan nocSpan(noc.Get(), kMaxDERCertLength);

	chip::Platform::ScopedMemoryBuffer<uint8_t> icac;
	ReturnErrorCodeIf(!icac.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
	MutableByteSpan icacSpan(icac.Get(), kMaxDERCertLength);

	chip::Platform::ScopedMemoryBuffer<uint8_t> rcac;
	ReturnErrorCodeIf(!rcac.Alloc(kMaxDERCertLength), CHIP_ERROR_NO_MEMORY);
	MutableByteSpan rcacSpan(rcac.Get(), kMaxDERCertLength);

	ReturnErrorOnFailure(
	GenerateNOCChainAfterValidation(assignedId, mNextFabricId, mNextCATs, pubkey, rcacSpan, icacSpan, nocSpan));

	// TODO(#13825): Should always generate some IPK. Using a temporary fixed value until APIs are plumbed in to set it end-to-end
	// TODO: Force callers to set IPK if used before GenerateNOCChain will succeed.
	ByteSpan defaultIpkSpan = chip::GroupTesting::DefaultIpkValue::GetDefaultIpk();

	// The below static assert validates a key assumption in types used (needed for public API conformance)
	static_assert(CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES == kAES_CCM128_Key_Length, "IPK span sizing must match");

	// Prepare IPK to be sent back. A more fully-fledged operational credentials delegate
	// would obtain a suitable key per fabric.
	uint8_t ipkValue[CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES];
	Crypto::IdentityProtectionKeySpan ipkSpan(ipkValue);

	ReturnErrorCodeIf(defaultIpkSpan.size() != sizeof(ipkValue), CHIP_ERROR_INTERNAL);
	memcpy(&ipkValue[0], defaultIpkSpan.data(), defaultIpkSpan.size());

	// Callback onto commissioner.
	ChipLogProgress(Controller, "Providing certificate chain to the commissioner");
	onCompletion->mCall(onCompletion->mContext, CHIP_NO_ERROR, nocSpan, icacSpan, rcacSpan, MakeOptional(ipkSpan),
	Optional<NodeId>());
	return CHIP_NO_ERROR;
	}

	CHIP_ERROR ExampleOperationalCredentialsIssuer::GetRandomOperationalNodeId(NodeId * aNodeId)
	{
	for (int i = 0; i < 10; ++i)
	{
	CHIP_ERROR err = DRBG_get_bytes(reinterpret_cast<uint8_t >(aNodeId), sizeof(aNodeId));
	if (err != CHIP_NO_ERROR)
	{
	return err;
	}

	if (IsOperationalNodeId(*aNodeId))
	{
	return CHIP_NO_ERROR;
	}
	}

	// Terrible, universe-ending luck (chances are 1 in 2^280 or so here, if our
	// DRBG is good).
	return CHIP_ERROR_INTERNAL;
	}

	} // namespace Controller
	} // namespace chip