[crypto] Migrate Operational Keys from mbedTLS to PSA ITS

Implemented a mechanism to detect all existing mbedTLS-related
operational keys stored in non-secure storage and move them to
the PSA ITS secure storage.

After the migration all keys will be removed from non-secure
storage.

src/app/server/Server.cpp

@@ -655,7 +655,11 @@ void Server::ResumeSubscriptions()
 Credentials::IgnoreCertificateValidityPeriodPolicy Server::sDefaultCertValidityPolicy;
 
 KvsPersistentStorageDelegate CommonCaseDeviceServerInitParams::sKvsPersistenStorageDelegate;
+#if CHIP_CRYPTO_PSA
+PSAOperationalKeystore CommonCaseDeviceServerInitParams::sPSAOperationalKeystore;
+#else
 PersistentStorageOperationalKeystore CommonCaseDeviceServerInitParams::sPersistentStorageOperationalKeystore;
+#endif
 Credentials::PersistentStorageOpCertStore CommonCaseDeviceServerInitParams::sPersistentStorageOpCertStore;
 Credentials::GroupDataProviderImpl CommonCaseDeviceServerInitParams::sGroupDataProvider;
 app::DefaultTimerDelegate CommonCaseDeviceServerInitParams::sTimerDelegate;

src/app/server/Server.h

@@ -41,7 +41,11 @@
 #include <credentials/PersistentStorageOpCertStore.h>
 #include <crypto/DefaultSessionKeystore.h>
 #include <crypto/OperationalKeystore.h>
+#if CHIP_CRYPTO_PSA
+#include <crypto/PSAOperationalKeystore.h>
+#else
 #include <crypto/PersistentStorageOperationalKeystore.h>
+#endif
 #include <inet/InetConfig.h>
 #include <lib/core/CHIPConfig.h>
 #include <lib/support/SafeInt.h>
@@ -214,10 +218,15 @@ struct CommonCaseDeviceServerInitParams : public ServerInitParams
         // PersistentStorageDelegate "software-based" operational key access injection
         if (this->operationalKeystore == nullptr)
         {
+#if CHIP_CRYPTO_PSA
+            ReturnErrorOnFailure(sPSAOperationalKeystore.Init(this->persistentStorageDelegate));
+            this->operationalKeystore = &sPSAOperationalKeystore;
+#else
             // WARNING: PersistentStorageOperationalKeystore::Finish() is never called. It's fine for
             //          for examples and for now.
             ReturnErrorOnFailure(sPersistentStorageOperationalKeystore.Init(this->persistentStorageDelegate));
             this->operationalKeystore = &sPersistentStorageOperationalKeystore;
+#endif
         }
 
         // OpCertStore can be injected but default to persistent storage default
@@ -273,7 +282,11 @@ struct CommonCaseDeviceServerInitParams : public ServerInitParams
 
 private:
     static KvsPersistentStorageDelegate sKvsPersistenStorageDelegate;
+#if CHIP_CRYPTO_PSA
+    static PSAOperationalKeystore sPSAOperationalKeystore;
+#else
     static PersistentStorageOperationalKeystore sPersistentStorageOperationalKeystore;
+#endif
     static Credentials::PersistentStorageOpCertStore sPersistentStorageOpCertStore;
     static Credentials::GroupDataProviderImpl sGroupDataProvider;
     static chip::app::DefaultTimerDelegate sTimerDelegate;

src/crypto/PSAOperationalKeystore.cpp

@@ -17,13 +17,22 @@
 
 #include "PSAOperationalKeystore.h"
 
+#include <lib/core/TLV.h>
 #include <lib/support/CHIPMem.h>
+#include <lib/support/DefaultStorageKeyAllocator.h>
 
 #include <psa/crypto.h>
 
 namespace chip {
 namespace Crypto {
 
+namespace {
+// Tags for our operational keypair storage copied from PersistentStorageOperationalKeystore.cpp
+constexpr TLV::Tag kOpKeyVersionTag = TLV::ContextTag(0);
+constexpr TLV::Tag kOpKeyDataTag    = TLV::ContextTag(1);
+constexpr uint16_t kOpKeyVersion    = 1;
+} // namespace
+
 PSAOperationalKeystore::PersistentP256Keypair::PersistentP256Keypair(FabricIndex fabricIndex)
 {
     ToPsaContext(mKeypair).key_id = MakeOperationalKeyId(fabricIndex);
@@ -135,6 +144,40 @@ CHIP_ERROR PSAOperationalKeystore::NewOpKeypairForFabric(FabricIndex fabricIndex
     return CHIP_NO_ERROR;
 }
 
+CHIP_ERROR PSAOperationalKeystore::PersistentP256Keypair::Deserialize(P256SerializedKeypair & input)
+{
+    CHIP_ERROR error                = CHIP_NO_ERROR;
+    psa_status_t status             = PSA_SUCCESS;
+    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
+    psa_key_id_t keyId              = 0;
+    Encoding::BufferWriter bbuf(mPublicKey, mPublicKey.Length());
+
+    Destroy();
+
+    // Type based on ECC with the elliptic curve SECP256r1 -> PSA_ECC_FAMILY_SECP_R1
+    psa_set_key_type(&attributes, PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1));
+    psa_set_key_bits(&attributes, kP256_PrivateKey_Length * 8);
+    psa_set_key_algorithm(&attributes, PSA_ALG_ECDSA(PSA_ALG_SHA_256));
+    psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_SIGN_MESSAGE);
+    psa_set_key_lifetime(&attributes, PSA_KEY_LIFETIME_PERSISTENT);
+    psa_set_key_id(&attributes, GetKeyId());
+
+    status = psa_import_key(&attributes, input.ConstBytes() + mPublicKey.Length(), kP256_PrivateKey_Length, &keyId);
+    VerifyOrExit(status == PSA_SUCCESS, error = CHIP_ERROR_INTERNAL);
+
+    bbuf.Put(input.ConstBytes(), mPublicKey.Length());
+    if (!bbuf.Fit())
+    {
+        psa_destroy_key(keyId);
+        error = CHIP_ERROR_NO_MEMORY;
+    }
+
+exit:
+    psa_reset_key_attributes(&attributes);
+
+    return error;
+}
+
 CHIP_ERROR PSAOperationalKeystore::ActivateOpKeypairForFabric(FabricIndex fabricIndex, const Crypto::P256PublicKey & nocPublicKey)
 {
     VerifyOrReturnError(IsValidFabricIndex(fabricIndex) && mPendingFabricIndex == fabricIndex, CHIP_ERROR_INVALID_FABRIC_INDEX);
@@ -209,5 +252,56 @@ void PSAOperationalKeystore::ReleasePendingKeypair()
     mIsPendingKeypairActive = false;
 }
 
+CHIP_ERROR PSAOperationalKeystore::MoveOpKeysFromKVSToITS(PersistentStorageDelegate * storage)
+{
+    Crypto::SensitiveDataBuffer<TLV::EstimateStructOverhead(sizeof(uint16_t), P256SerializedKeypair::Capacity())> buf;
+    uint16_t keySize = static_cast<uint16_t>(buf.Capacity());
+
+    for (FabricIndex index = 0; index < CHIP_CONFIG_MAX_FABRICS; index++)
+    {
+        CHIP_ERROR err = storage->SyncGetKeyValue(DefaultStorageKeyAllocator::FabricOpKey(index).KeyName(), buf.Bytes(), keySize);
+        if (CHIP_NO_ERROR == err)
+        {
+            PersistentP256Keypair keyPair(index);
+
+            // Do not allow overwriting the existing key and just remove it from KVS
+            if (keyPair.Exists())
+            {
+                ReturnErrorOnFailure(storage->SyncDeleteKeyValue(DefaultStorageKeyAllocator::FabricOpKey(index).KeyName()));
+                continue;
+            }
+
+            // Read the operational private and public keys from the TLV entry
+            buf.SetLength(static_cast<size_t>(keySize));
+            TLV::ContiguousBufferTLVReader reader;
+            reader.Init(buf.Bytes(), buf.Length());
+            ReturnErrorOnFailure(reader.Next(TLV::kTLVType_Structure, TLV::AnonymousTag()));
+            TLV::TLVType containerType;
+            ReturnErrorOnFailure(reader.EnterContainer(containerType));
+            ReturnErrorOnFailure(reader.Next(kOpKeyVersionTag));
+            uint16_t opKeyVersion;
+            ReturnErrorOnFailure(reader.Get(opKeyVersion));
+            VerifyOrReturnError(opKeyVersion == kOpKeyVersion, CHIP_ERROR_VERSION_MISMATCH);
+            ReturnErrorOnFailure(reader.Next(kOpKeyDataTag));
+
+            ByteSpan keyData;
+            ReturnErrorOnFailure(reader.GetByteView(keyData));
+            ReturnErrorOnFailure(reader.ExitContainer(containerType));
+            ReturnErrorOnFailure(reader.VerifyEndOfContainer());
+
+            if (keyData.size() == kP256_PrivateKey_Length + kP256_PublicKey_Length)
+            {
+                P256SerializedKeypair serializedKeypair;
+                ReturnErrorOnFailure(serializedKeypair.SetLength(kP256_PrivateKey_Length + kP256_PublicKey_Length));
+                memcpy(serializedKeypair.Bytes(), keyData.data(), kP256_PrivateKey_Length + kP256_PublicKey_Length);
+                ReturnErrorOnFailure(keyPair.Deserialize(serializedKeypair));
+                ReturnErrorOnFailure(storage->SyncDeleteKeyValue(DefaultStorageKeyAllocator::FabricOpKey(index).KeyName()));
+            }
+        }
+    }
+
+    return CHIP_NO_ERROR;
+}
+
 } // namespace Crypto
 } // namespace chip

src/crypto/PSAOperationalKeystore.h

@@ -19,13 +19,29 @@
 
 #include <crypto/CHIPCryptoPALPSA.h>
 #include <crypto/OperationalKeystore.h>
+#include <lib/core/CHIPPersistentStorageDelegate.h>
 
 namespace chip {
 namespace Crypto {
 
 class PSAOperationalKeystore final : public OperationalKeystore
 {
 public:
+    /**
+     * @brief Initialize the PSA Operational Keystore and move all sensitive keys from storage to ITS secure storage.
+     *
+     * After moving all sensitive keys to ITS, the old one stored in the storage will be removed and not available anymore.
+     *
+     * @param storage Pointer to persistent storage delegate to use.
+     * @retval CHIP_NO_ERROR on success
+     * @retval CHIP_ERROR_INCORRECT_STATE if already initialized
+     */
+    CHIP_ERROR Init(PersistentStorageDelegate * storage)
+    {
+        VerifyOrReturnError(storage != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
+        return MoveOpKeysFromKVSToITS(storage);
+    }
+
     bool HasPendingOpKeypair() const override;
     bool HasOpKeypairForFabric(FabricIndex fabricIndex) const override;
     CHIP_ERROR NewOpKeypairForFabric(FabricIndex fabricIndex, MutableByteSpan & outCertificateSigningRequest) override;
@@ -53,13 +69,17 @@ class PSAOperationalKeystore final : public OperationalKeystore
         bool Exists() const;
         CHIP_ERROR Generate();
         CHIP_ERROR Destroy();
+        CHIP_ERROR Deserialize(P256SerializedKeypair & input);
     };
 
     void ReleasePendingKeypair();
 
     PersistentP256Keypair * mPendingKeypair = nullptr;
     FabricIndex mPendingFabricIndex         = kUndefinedFabricIndex;
     bool mIsPendingKeypairActive            = false;
+
+private:
+    CHIP_ERROR MoveOpKeysFromKVSToITS(PersistentStorageDelegate * storage);
 };
 
 } // namespace Crypto