[nrf fromtree] [crypto] Migrate Operational Keys from mbedTLS to PSA ITS

- Extended the OperationalKeystore API by mechanism for migration of operational keys stored in one Operational Keystore implementation to another. - Extended the OperationalKeystore API by exporting keypair for Fabric. - Added Unit tests to PersistentStorageOpKeyStore and PSAOpKeystore regarding the new OperationalKeystore for migration and exporting OpKeys. Added first unit tests, created export method
nrfconnect · Jan 16, 2024 · ffbfd48 · ffbfd48
1 parent e54423d
commit ffbfd48
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Showing 11 changed files with 526 additions and 52 deletions.
diff --git a/src/app/server/Server.cpp b/src/app/server/Server.cpp
@@ -163,6 +163,27 @@ CHIP_ERROR Server::Init(const ServerInitParams & initParams)
         SuccessOrExit(err);
     }
 
+#if CHIP_CRYPTO_PSA
+    {
+        PersistentStorageOperationalKeystore persistentStorageOperationalKeystore;
+        if (CHIP_NO_ERROR == persistentStorageOperationalKeystore.Init(mDeviceStorage))
+        {
+            for (const FabricInfo & fabric : mFabrics)
+            {
+                if (CHIP_NO_ERROR !=
+                    mOperationalKeystore->MigrateOpKeypairForFabric(fabric.GetFabricIndex(), persistentStorageOperationalKeystore))
+                {
+                    ChipDeviceEvent event;
+                    event.Type                                           = DeviceEventType::kOperationalKeystoreMigrationFailed;
+                    event.OperationalKeystoreMigrationFailed.fabricIndex = fabric.GetFabricIndex();
+                    // Post event and ignore the result to not block server Init flow
+                    err = PlatformMgr().PostEvent(&event);
+                }
+            }
+        }
+    }
+#endif
+
     SuccessOrExit(err = mAccessControl.Init(initParams.accessDelegate, sDeviceTypeResolver));
     Access::SetAccessControl(mAccessControl);
 

diff --git a/src/app/server/Server.h b/src/app/server/Server.h
@@ -42,9 +42,8 @@
 #include <crypto/OperationalKeystore.h>
 #if CHIP_CRYPTO_PSA
 #include <crypto/PSAOperationalKeystore.h>
-#else
-#include <crypto/PersistentStorageOperationalKeystore.h>
 #endif
+#include <crypto/PersistentStorageOperationalKeystore.h>
 #include <inet/InetConfig.h>
 #include <lib/core/CHIPConfig.h>
 #include <lib/support/SafeInt.h>

diff --git a/src/crypto/OperationalKeystore.h b/src/crypto/OperationalKeystore.h
@@ -119,6 +119,41 @@ class OperationalKeystore
      */
     virtual CHIP_ERROR CommitOpKeypairForFabric(FabricIndex fabricIndex) = 0;
 
+    /**
+     * @brief Try to read out the permanently commited operational keypair and save it to the buffer.
+     *
+     * @param fabricIndex - FabricIndex from which the keypair will be exported
+     * @param outKeypair - a reference to P256SerializedKeypair object to store the exported key.
+     * @retval CHIP_ERROR on success.
+     * @retval CHIP_ERROR_UNSUPPORTED_CHIP_FEATURE if the key cannot be exported due to security restrictions.
+     * @retval CHIP_ERROR_NOT_IMPLEMENTED if the exporting is not implemented for the crypto engine.
+     * @retval CHIP_ERROR_INVALID_FABRIC_INDEX if provided wrong value of `fabricIndex`.
+     * @retval CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND if there is no keypair found for `fabricIndex`.
+     * @retval CHIP_ERROR_BUFFER_TOO_SMALL if `outKeyPair` buffer is too small to store the read out keypair.
+     * @retval other CHIP_ERROR value on internal storage or crypto engine errors.
+     */
+    virtual CHIP_ERROR ExportOpKeypairForFabric(FabricIndex fabricIndex, Crypto::P256SerializedKeypair & outKeypair) = 0;
+
+    /**
+     * @brief Migrate the operational keypair from the extern Operational keystore (`operationalKeystore`) to this one.
+     *
+     * This method assumes that the operational key for given `fabricIndex` exists in the `operationalKeystore` storage or it has
+     * been already migrated to the new Operational Storage. If a key for the given `fabricIndex` does not exist in any of those
+     * keystores, then the method retuns CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND.
+     *
+     * @param fabricIndex - FabricIndex for which to migrate the operational key
+     * @param operationalKeystore - a reference to the operationalKeystore implementation that may contain saved operational key
+     * for Fabric
+     * @retval CHIP_ERROR on success
+     * @retval CHIP_ERROR_UNSUPPORTED_CHIP_FEATURE if the key cannot be exported due to security restrictions.
+     * @retval CHIP_ERROR_NOT_IMPLEMENTED if the exporting is not implemented for the crypto engine.
+     * @retval CHIP_ERROR_INVALID_FABRIC_INDEX if there is no keypair found for `fabricIndex`.
+     * @retval CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND if there is no keypair found for `fabricIndex`.
+     * @retval CHIP_ERROR_BUFFER_TOO_SMALL if `keyPair` buffer is too small to store the read out keypair.
+     * @retval other CHIP_ERROR value on internal storage or crypto engine errors.
+     */
+    virtual CHIP_ERROR MigrateOpKeypairForFabric(FabricIndex fabricIndex, OperationalKeystore & operationalKeystore) const = 0;
+
     /**
      * @brief Permanently remove the keypair associated with a fabric
      *

diff --git a/src/crypto/PSAOperationalKeystore.cpp b/src/crypto/PSAOperationalKeystore.cpp
@@ -16,6 +16,7 @@
  */
 
 #include "PSAOperationalKeystore.h"
+#include "PersistentStorageOperationalKeystore.h"
 
 #include <lib/support/CHIPMem.h>
 
@@ -135,6 +136,35 @@ 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;
+    VerifyOrReturnError(input.Length() == mPublicKey.Length() + kP256_PrivateKey_Length, CHIP_ERROR_INVALID_ARGUMENT);
+
+    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);
+
+    memcpy(mPublicKey.Bytes(), input.ConstBytes(), mPublicKey.Length());
+
+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);
@@ -154,6 +184,40 @@ CHIP_ERROR PSAOperationalKeystore::CommitOpKeypairForFabric(FabricIndex fabricIn
     return CHIP_NO_ERROR;
 }
 
+CHIP_ERROR PSAOperationalKeystore::ExportOpKeypairForFabric(FabricIndex fabricIndex, Crypto::P256SerializedKeypair & outKeypair)
+{
+    // Currently exporting the key is forbidden in PSAOperationalKeystore because the PSA_KEY_USAGE_EXPORT usage flag is not set, so
+    // there is no need to compile the code for the device, but there should be an implementation for the test purposes to verify if
+    // the psa_export_key returns an error.
+#if CHIP_CONFIG_TEST
+    VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
+    VerifyOrReturnError(HasOpKeypairForFabric(fabricIndex), CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND);
+
+    size_t outSize = 0;
+    psa_status_t status =
+        psa_export_key(PersistentP256Keypair(fabricIndex).GetKeyId(), outKeypair.Bytes(), outKeypair.Capacity(), &outSize);
+
+    if (status == PSA_ERROR_BUFFER_TOO_SMALL)
+    {
+        return CHIP_ERROR_BUFFER_TOO_SMALL;
+    }
+    else if (status == PSA_ERROR_NOT_PERMITTED)
+    {
+        return CHIP_ERROR_UNSUPPORTED_CHIP_FEATURE;
+    }
+    else if (status != PSA_SUCCESS)
+    {
+        return CHIP_ERROR_INTERNAL;
+    }
+
+    outKeypair.SetLength(outSize);
+
+    return CHIP_NO_ERROR;
+#else
+    return CHIP_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
 CHIP_ERROR PSAOperationalKeystore::RemoveOpKeypairForFabric(FabricIndex fabricIndex)
 {
     VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
@@ -209,5 +273,31 @@ void PSAOperationalKeystore::ReleasePendingKeypair()
     mIsPendingKeypairActive = false;
 }
 
+CHIP_ERROR PSAOperationalKeystore::MigrateOpKeypairForFabric(FabricIndex fabricIndex,
+                                                             OperationalKeystore & operationalKeystore) const
+{
+    VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
+
+    P256SerializedKeypair serializedKeypair;
+
+    // Do not allow overwriting the existing key and just remove it from the previous Operational Keystore if needed.
+    if (!HasOpKeypairForFabric(fabricIndex))
+    {
+        ReturnErrorOnFailure(operationalKeystore.ExportOpKeypairForFabric(fabricIndex, serializedKeypair));
+
+        PersistentP256Keypair keypair(fabricIndex);
+        ReturnErrorOnFailure(keypair.Deserialize(serializedKeypair));
+
+        // Migrated key is not useful anymore, remove it from the previous keystore.
+        ReturnErrorOnFailure(operationalKeystore.RemoveOpKeypairForFabric(fabricIndex));
+    }
+    else if (operationalKeystore.HasOpKeypairForFabric(fabricIndex))
+    {
+        ReturnErrorOnFailure(operationalKeystore.RemoveOpKeypairForFabric(fabricIndex));
+    }
+
+    return CHIP_NO_ERROR;
+}
+
 } // namespace Crypto
 } // namespace chip
diff --git a/src/crypto/PSAOperationalKeystore.h b/src/crypto/PSAOperationalKeystore.h
@@ -19,6 +19,7 @@
 
 #include <crypto/CHIPCryptoPALPSA.h>
 #include <crypto/OperationalKeystore.h>
+#include <lib/core/CHIPPersistentStorageDelegate.h>
 
 namespace chip {
 namespace Crypto {
@@ -31,7 +32,9 @@ class PSAOperationalKeystore final : public OperationalKeystore
     CHIP_ERROR NewOpKeypairForFabric(FabricIndex fabricIndex, MutableByteSpan & outCertificateSigningRequest) override;
     CHIP_ERROR ActivateOpKeypairForFabric(FabricIndex fabricIndex, const Crypto::P256PublicKey & nocPublicKey) override;
     CHIP_ERROR CommitOpKeypairForFabric(FabricIndex fabricIndex) override;
+    CHIP_ERROR ExportOpKeypairForFabric(FabricIndex fabricIndex, Crypto::P256SerializedKeypair & outKeypair) override;
     CHIP_ERROR RemoveOpKeypairForFabric(FabricIndex fabricIndex) override;
+    CHIP_ERROR MigrateOpKeypairForFabric(FabricIndex fabricIndex, OperationalKeystore & operationalKeystore) const;
     void RevertPendingKeypair() override;
     CHIP_ERROR SignWithOpKeypair(FabricIndex fabricIndex, const ByteSpan & message,
                                  Crypto::P256ECDSASignature & outSignature) const override;
@@ -53,13 +56,15 @@ 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;
+    PersistentStorageDelegate * mStorage    = nullptr;
 };
 
 } // namespace Crypto