/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * 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.
 */

package android.hardware.security.keymint;

import android.hardware.security.keymint.BeginResult;
import android.hardware.security.keymint.ByteArray;
import android.hardware.security.keymint.HardwareAuthToken;
import android.hardware.security.keymint.IKeyMintOperation;
import android.hardware.security.keymint.KeyCreationResult;
import android.hardware.security.keymint.KeyFormat;
import android.hardware.security.keymint.KeyParameter;
import android.hardware.security.keymint.KeyMintHardwareInfo;
import android.hardware.security.keymint.KeyPurpose;
import android.hardware.security.keymint.SecurityLevel;
import android.hardware.security.keymint.VerificationToken;

/**
 * KeyMint device definition.
 *
 * == Features ==
 *
 * An IKeyMintDevice provides cryptographic services, including the following categories of
 * operations:
 *
 * o   Key generation
 * o   Import of asymmetric keys
 * o   Import of raw symmetric keys
 * o   Asymmetric decryption with appropriate padding modes
 * o   Asymmetric signing with digesting and appropriate padding modes
 * o   Symmetric encryption and decryption in appropriate modes, including an AEAD mode
 * o   Generation and verification of symmetric message authentication codes
 * o   Attestation to the presence and configuration of asymmetric keys.
 *
 * Protocol elements, such as purpose, mode and padding, as well as access control constraints, must
 * be specified by the caller when keys are generated or imported and must be permanently bound to
 * the key, ensuring that the key cannot be used in any other way.
 *
 * In addition to the list above, IKeyMintDevice implementations must provide one more service
 * which is not exposed as an API but used internally: Random number generation.  The random number
 * generator must be high-quality and must be used for generation of keys, initialization vectors,
 * random padding and other elements of secure protocols that require randomness.
 *
 * == Types of IKeyMintDevices ==
 *
 * All of the operations and storage of key material must occur in a secure environment.  Secure
 * environments may be either:
 *
 * 1.  Isolated execution environments, such as a separate virtual machine, hypervisor or
 *      purpose-built trusted execution environment like ARM TrustZone.  The isolated environment
 *      must provide complete separation from the Android kernel and user space (collectively called
 *      the "non-secure world", or NSW) so that nothing running in the NSW can observe or manipulate
 *      the results of any computation in the isolated environment.  Isolated execution environments
 *      are identified by the SecurityLevel TRUSTED_ENVIRONMENT.
 *
 * 2.  Completely separate, purpose-built and certified secure CPUs, called "StrongBox" devices.
 *      Examples of StrongBox devices are embedded Secure Elements (eSE) or on-SoC secure processing
 *      units (iSE).  StrongBox environments are identified by the SecurityLevel STRONGBOX.  To
 *      qualify as a StrongBox, a device must meet the requirements specified in CDD 9.11.2.
 *
 * == Necessary Primitives ==
 *
 * All IKeyMintDevice implementations must provide support for the following:
 *
 * o   RSA
 *
 *      - TRUSTED_ENVIRONMENT IKeyMintDevices must support 2048, 3072 and 4096-bit keys.
 *        STRONGBOX IKeyMintDevices must support 2048-bit keys.
 *      - Public exponent F4 (2^16+1)
 *      - Unpadded, RSASSA-PSS and RSASSA-PKCS1-v1_5 padding modes for RSA signing
 *      - TRUSTED_ENVIRONMENT IKeyMintDevices must support MD5, SHA1, SHA-2 224, SHA-2 256, SHA-2
 *        384 and SHA-2 512 digest modes for RSA signing.  STRONGBOX IKeyMintDevices must support
 *        SHA-2 256.
 *      - Unpadded, RSAES-OAEP and RSAES-PKCS1-v1_5 padding modes for RSA encryption.
 *
 * o   ECDSA
 *
 *      - TRUSTED_ENVIRONMENT IKeyMintDevices must support NIST curves P-224, P-256, P-384 and
 *        P-521.  STRONGBOX IKeyMintDevices must support NIST curve P-256.
 *      - TRUSTED_ENVIRONMENT IKeyMintDevices must support SHA1, SHA-2 224, SHA-2 256, SHA-2
 *        384 and SHA-2 512 digest modes.  STRONGBOX IKeyMintDevices must support SHA-2 256.
 *
 * o   AES
 *
 *      - 128 and 256-bit keys
 *      - CBC, CTR, ECB and GCM modes.  The GCM mode must not allow the use of tags smaller than 96
 *        bits or nonce lengths other than 96 bits.
 *      - CBC and ECB modes must support unpadded and PKCS7 padding modes.  With no padding CBC and
 *        ECB-mode operations must fail with ErrorCode::INVALID_INPUT_LENGTH if the input isn't a
 *        multiple of the AES block size.  With PKCS7 padding, GCM and CTR operations must fail with
 *        ErrorCode::INCOMPATIBLE_PADDING_MODE.
 *
 * o   3DES
 *
 *      - 168-bit keys.
 *      - CBC and ECB mode.

 *      - CBC and ECB modes must support unpadded and PKCS7 padding modes.  With no padding CBC and
 *        ECB-mode operations must fail with ErrorCode::INVALID_INPUT_LENGTH if the input isn't a
 *        multiple of the DES block size.
 *
 * o   HMAC
 *
 *      - Any key size that is between 64 and 512 bits (inclusive) and a multiple of 8 must be
 *        supported.  STRONGBOX IKeyMintDevices must not support keys larger than 512 bits.
 *      - TRUSTED_ENVIRONMENT IKeyMintDevices must support MD-5, SHA1, SHA-2-224, SHA-2-256,
 *        SHA-2-384 and SHA-2-512.  STRONGBOX IKeyMintDevices must support SHA-2-256.
 *
 * == Key Access Control ==
 *
 * Hardware-based keys that can never be extracted from the device don't provide much security if an
 * attacker can use them at will (though they're more secure than keys which can be
 * exfiltrated).  Therefore, IKeyMintDevice must enforce access controls.
 *
 * Access controls are defined as "authorization lists" of tag/value pairs.  Authorization tags are
 * 32-bit integers from the Tag enum, and the values are a variety of types, defined in the TagType
 * enum.  Some tags may be repeated to specify multiple values.  Whether a tag may be repeated is
 * specified in the documentation for the tag and in the TagType.  When a key is created or
 * imported, the caller specifies a `key_description` authorization list.  The IKeyMintDevice must
 * determine which tags it can and cannot enforce, and at what SecurityLevel, and return an array of
 * `KeyCharacteristics` structures that contains everything it will enforce, associated with the
 * appropriate security level, which is one of SOFTWARE, TRUSTED_ENVIRONMENT and STRONGBOX.
 * Typically, implementations will only return a single KeyCharacteristics structure, because
 * everything they enforce is enforced at the same security level.  There may be cases, however, for
 * which multiple security levels are relevant. One example is that of a StrongBox IKeyMintDevice
 * that relies on a TEE to enforce biometric user authentication.  In that case, the generate/import
 * methods must return two KeyCharacteristics structs, one with SecurityLevel::TRUSTED_ENVIRONMENT
 * and the biometric authentication-related tags, and another with SecurityLevel::STRONGBOX and
 * everything else.  The IKeyMintDevice must also add the following authorizations to the
 * appropriate list:
 *
 * o    Tag::OS_VERSION
 * o    Tag::OS_PATCHLEVEL
 * o    Tag::VENDOR_PATCHLEVEL
 * o    Tag::BOOT_PATCHLEVEL
 * o    Tag::ORIGIN
 *
 * The IKeyMintDevice must ignore unknown tags.
 *
 * The caller must always provide the current date time in the keyParameter CREATION_DATETIME
 * tags.
 *
 * All authorization tags and their values enforced by an IKeyMintDevice must be cryptographically
 * bound to the private/secret key material such that any modification of the portion of the key
 * blob that contains the authorization list makes it impossible for the secure environment to
 * obtain the private/secret key material.  The recommended approach to meet this requirement is to
 * use the full set of authorization tags associated with a key as input to a secure key derivation
 * function used to derive a key (the KEK) that is used to encrypt the private/secret key material.
 * Note that it is NOT acceptable to use a static KEK to encrypt the private/secret key material
 * with an AEAD cipher mode, using the enforced authorization tags as AAD.  This is because
 * Tag::APPLICATION_DATA must not be included in the authorization tags stored in the key blob, but
 * must be provided by the caller for every use.  Assuming the Tag::APPLICATION_DATA value has
 * sufficient entropy, this provides a cryptographic guarantee that an attacker cannot use a key
 * without knowing the Tag::APPLICATION_DATA value, even if they compromise the IKeyMintDevice.
 *
 * IKeyMintDevice implementations must ignore any tags they cannot enforce and must not return them
 * in KeyCharacteristics.  For example, Tag::ORIGINATION_EXPIRE_DATETIME provides the date and time
 * after which a key may not be used to encrypt or sign new messages.  Unless the IKeyMintDevice has
 * access to a secure source of current date/time information, it is not possible for the
 * IKeyMintDevice to enforce this tag.  An IKeyMintDevice implementation will not rely on the
 * non-secure world's notion of time, because it could be controlled by an attacker. Similarly, it
 * cannot rely on GPSr time, even if it has exclusive control of the GPSr, because that might be
 * spoofed by attacker RF signals.
 *
 * Some tags must be enforced by the IKeyMintDevice.  See the detailed documentation on each Tag
 * in Tag.aidl.
 *
 * == Root of Trust Binding ==
 *
 * IKeyMintDevice keys must be bound to a root of trust, which is a bitstring that must be
 * provided to the secure environment (by an unspecified, implementation-defined mechanism) during
 * startup, preferably by the bootloader.  This bitstring must be cryptographically bound to every
 * key managed by the IKeyMintDevice.  As above, the recommended mechanism for this cryptographic
 * binding is to include the Root of Trust data in the input to the key derivation function used to
 * derive a key that is used to encryp the private/secret key material.
 *
 * The root of trust consists of a bitstring that must be derived from the public key used by
 * Verified Boot to verify the signature on the boot image and from the lock state of the
 * device.  If the public key is changed to allow a different system image to be used or if the
 * lock state is changed, then all of the IKeyMintDevice-protected keys created by the previous
 * system state must be unusable, unless the previous state is restored.  The goal is to increase
 * the value of the software-enforced key access controls by making it impossible for an attacker-
 * installed operating system to use IKeyMintDevice keys.
 *
 * == Version Binding ==
 *
 * All keys must also be bound to the operating system and patch level of the system image and the
 * patch levels of the vendor image and boot image.  This ensures that an attacker who discovers a
 * weakness in an old version of the software cannot roll a device back to the vulnerable version
 * and use keys created with the newer version.  In addition, when a key with a given version and
 * patch level is used on a device that has been upgraded to a newer version or patch level, the
 * key must be upgraded (See IKeyMintDevice::upgradeKey()) before it can be used, and the previous
 * version of the key must be invalidated.  In this way, as the device is upgraded, the keys will
 * "ratchet" forward along with the device, but any reversion of the device to a previous release
 * will cause the keys to be unusable.
 *
 * This version information must be associated with every key as a set of tag/value pairs in the
 * hardwareEnforced authorization list.  Tag::OS_VERSION, Tag::OS_PATCHLEVEL,
 * Tag::VENDOR_PATCHLEVEL, and Tag::BOOT_PATCHLEVEL must be cryptographically bound to every
 * IKeyMintDevice key, as described in the Key Access Control section above.
 */
@VintfStability
interface IKeyMintDevice {
    const int AUTH_TOKEN_MAC_LENGTH = 32;

    /**
     * @return info which contains information about the underlying IKeyMintDevice hardware, such
     *         as version number, security level, keyMint name and author name.
     */
    KeyMintHardwareInfo getHardwareInfo();

    /**
     * Verify authorizations for another IKeyMintDevice instance.
     *
     * On systems with both a StrongBox and a TEE IKeyMintDevice instance it is sometimes useful
     * to ask the TEE KeyMintDevice to verify authorizations for a key hosted in StrongBox.
     *
     * For every StrongBox operation, Keystore is required to call this method on the TEE KeyMint,
     * passing in the StrongBox key's hardwareEnforced authorization list and the challenge
     * returned by StrongBox begin().  Keystore must then pass the VerificationToken to the
     * subsequent invocations of StrongBox update() and finish().
     *
     * StrongBox implementations must return ErrorCode::UNIMPLEMENTED.
     *
     * @param the challenge returned by StrongBox's keyMint's begin().
     *
     * @param authToken A HardwareAuthToken if needed to authorize key usage.
     *
     * @return error ErrorCode::OK on success or ErrorCode::UNIMPLEMENTED if the KeyMintDevice is
     *         a StrongBox.  If the IKeyMintDevice cannot verify one or more elements of
     *         parametersToVerify it must not return an error code, but just omit the unverified
     *         parameter from the VerificationToken.
     *
     * @return token the verification token.  See VerificationToken in VerificationToken.aidl for
     *         details.
     */
    VerificationToken verifyAuthorization(in long challenge,
                                          in HardwareAuthToken token);

    /**
     * Adds entropy to the RNG used by KeyMint.  Entropy added through this method must not be the
     * only source of entropy used, and a secure mixing function must be used to mix the entropy
     * provided by this method with internally-generated entropy.  The mixing function must be
     * secure in the sense that if any one of the mixing function inputs is provided with any data
     * the attacker cannot predict (or control), then the output of the seeded CRNG is
     * indistinguishable from random.  Thus, if the entropy from any source is good, the output
     * must be good.
     *
     * TODO(seleneh) specify what mixing functions and cprng we allow.
     *
     * @param data Bytes to be mixed into the CRNG seed.  The caller must not provide more than 2
     *        KiB of data per invocation.
     *
     * @return error ErrorCode::OK on success; ErrorCode::INVALID_INPUT_LENGTH if the caller
     *         provides more than 2 KiB of data.
     */
    void addRngEntropy(in byte[] data);

    /**
     * Generates a new cryptographic key, specifying associated parameters, which must be
     * cryptographically bound to the key.  IKeyMintDevice implementations must disallow any use
     * of a key in any way inconsistent with the authorizations specified at generation time.  With
     * respect to parameters that the secure environment cannot enforce, the secure envionment's
     * obligation is limited to ensuring that the unenforceable parameters associated with the key
     * cannot be modified.  In addition, the characteristics returned by generateKey places
     * parameters correctly in the tee-enforced and strongbox-enforced lists.
     *
     * In addition to the parameters provided, generateKey must add the following to the returned
     * characteristics.
     *
     * o Tag::ORIGIN with the value KeyOrigin::GENERATED.
     *
     * o Tag::BLOB_USAGE_REQUIREMENTS with the appropriate value (see KeyBlobUsageRequirements in
     *   Tag.aidl).
     *
     * o Tag::OS_VERSION, Tag::OS_PATCHLEVEL, Tag::VENDOR_PATCHLEVEL and Tag::BOOT_PATCHLEVEL with
     *   appropriate values.
     *
     * The parameters provided to generateKey depend on the type of key being generated.  This
     * section summarizes the necessary and optional tags for each type of key.  Tag::ALGORITHM is
     * always necessary, to specify the type.
     *
     * == RSA Keys ==
     *
     * The following parameters are required to generate an RSA key:
     *
     * o Tag::Key_SIZE specifies the size of the public modulus, in bits.  If omitted, generateKey
     *   must return ErrorCode::UNSUPPORTED_KEY_SIZE.  Required values for TEE IKeyMintDevice
     *   implementations are 1024, 2048, 3072 and 4096.  StrongBox IKeyMintDevice implementations
     *   must support 2048.
     *
     * o Tag::RSA_PUBLIC_EXPONENT specifies the RSA public exponent value.  If omitted, generateKey
     *   must return ErrorCode::INVALID_ARGUMENT.  The values 3 and 65537 must be supported.  It is
     *   recommended to support all prime values up to 2^64.  If provided with a non-prime value,
     *   generateKey must return ErrorCode::INVALID_ARGUMENT.
     *
     * The following parameters are not necessary to generate a usable RSA key, but generateKey must
     * not return an error if they are omitted:
     *
     * o Tag::PURPOSE specifies allowed purposes.  All KeyPurpose values (see KeyPurpose.aidl)
     *   except AGREE_KEY must be supported for RSA keys.
     *
     * o Tag::DIGEST specifies digest algorithms that may be used with the new key.  TEE
     *   IKeyMintDevice implementatiosn must support all Digest values (see digest.aidl) for RSA
     *   keys.  StrongBox IKeyMintDevice implementations must support SHA_2_256.
     *
     * o Tag::PADDING specifies the padding modes that may be used with the new
     *   key.  IKeyMintDevice implementations must support PaddingMode::NONE,
     *   PaddingMode::RSA_OAEP, PaddingMode::RSA_PSS, PaddingMode::RSA_PKCS1_1_5_ENCRYPT and
     *   PaddingMode::RSA_PKCS1_1_5_SIGN for RSA keys.
     *
     * == ECDSA Keys ==
     *
     * Either Tag::KEY_SIZE or Tag::EC_CURVE must be provided to generate an ECDSA key.  If neither
     * is provided, generateKey must return ErrorCode::UNSUPPORTED_KEY_SIZE.  If Tag::KEY_SIZE is
     * provided, the possible values are 224, 256, 384 and 521, and must be mapped to Tag::EC_CURVE
     * values P_224, P_256, P_384 and P_521, respectively.  TEE IKeyMintDevice implementations
     * must support all curves.  StrongBox implementations must support P_256.
     *
     * == AES Keys ==
     *
     * Only Tag::KEY_SIZE is required to generate an AES key.  If omitted, generateKey must return
     * ErrorCode::UNSUPPORTED_KEY_SIZE.  128 and 256-bit key sizes must be supported.
     *
     * If Tag::BLOCK_MODE is specified with value BlockMode::GCM, then the caller must also provide
     * Tag::MIN_MAC_LENGTH.  If omitted, generateKey must return ErrorCode::MISSING_MIN_MAC_LENGTH.
     *
     *
     * @param keyParams Key generation parameters are defined as KeyMintDevice tag/value pairs,
     *        provided in params.  See above for detailed specifications of which tags are required
     *        for which types of keys.
     *
     * @return The result of key creation.  See KeyCreationResult.aidl.
     */
    KeyCreationResult generateKey(in KeyParameter[] keyParams);

    /**
     * Imports key material into an IKeyMintDevice.  Key definition parameters and return values
     * are the same as for generateKey, with the following exceptions:
     *
     * o Tag::KEY_SIZE is not necessary in the input parameters.  If not provided, the
     *   IKeyMintDevice must deduce the value from the provided key material and add the tag and
     *   value to the key characteristics.  If Tag::KEY_SIZE is provided, the IKeyMintDevice must
     *   validate it against the key material.  In the event of a mismatch, importKey must return
     *   ErrorCode::IMPORT_PARAMETER_MISMATCH.
     *
     * o Tag::RSA_PUBLIC_EXPONENT (for RSA keys only) is not necessary in the input parameters.  If
     *   not provided, the IKeyMintDevice must deduce the value from the provided key material and
     *   add the tag and value to the key characteristics.  If Tag::RSA_PUBLIC_EXPONENT is provided,
     *   the IKeyMintDevice must validate it against the key material.  In the event of a
     *   mismatch, importKey must return ErrorCode::IMPORT_PARAMETER_MISMATCH.
     *
     * o Tag::ORIGIN (returned in keyCharacteristics) must have the value KeyOrigin::IMPORTED.
     *
     * @param inKeyParams Key generation parameters are defined as KeyMintDevice tag/value pairs,
     *        provided in params.
     *
     * @param inKeyFormat The format of the key material to import.  See KeyFormat in
     *        keyformat.aidl.
     *
     * @param inKeyData The key material to import, in the format specified in keyFormat.
     *
     * @return The result of key creation.  See KeyCreationResult.aidl.
     */
    KeyCreationResult importKey(in KeyParameter[] keyParams, in KeyFormat keyFormat,
                                in byte[] keyData);

    /**
     * Securely imports a key, or key pair, returning a key blob and a description of the imported
     * key.
     *
     * @param inWrappedKeyData The wrapped key material to import.
     *     TODO(seleneh) Decide if we want the wrapped key in DER-encoded ASN.1 format or CBOR
     *     format or both.  And specify the standarized format.
     *
     *     KeyDescription ::= SEQUENCE(
     *         keyFormat INTEGER,                   # Values from KeyFormat enum.
     *         keyParams AuthorizationList,
     *     )
     *
     *     SecureKeyWrapper ::= SEQUENCE(
     *         version INTEGER,                     # Contains value 0
     *         encryptedTransportKey OCTET_STRING,
     *         initializationVector OCTET_STRING,
     *         keyDescription KeyDescription,
     *         encryptedKey OCTET_STRING,
     *         tag OCTET_STRING
     *     )
     *
     *     Where:
     *
     *     o keyFormat is an integer from the KeyFormat enum, defining the format of the plaintext
     *       key material.
     *     o keyParams is the characteristics of the key to be imported (as with generateKey or
     *       importKey).  If the secure import is successful, these characteristics must be
     *       associated with the key exactly as if the key material had been insecurely imported
     *       with the IKeyMintDevice::importKey.  See attestKey() for documentation of the
     *       AuthorizationList schema.
     *     o encryptedTransportKey is a 256-bit AES key, XORed with a masking key and then encrypted
     *       with the wrapping key specified by wrappingKeyBlob.
     *     o keyDescription is a KeyDescription, above.
     *     o encryptedKey is the key material of the key to be imported, in format keyFormat, and
     *       encrypted with encryptedEphemeralKey in AES-GCM mode, with the DER-encoded
     *       representation of keyDescription provided as additional authenticated data.
     *     o tag is the tag produced by the AES-GCM encryption of encryptedKey.
     *
     * So, importWrappedKey does the following:
     *
     *     1. Get the private key material for wrappingKeyBlob, verifying that the wrapping key has
     *        purpose KEY_WRAP, padding mode RSA_OAEP, and digest SHA_2_256, returning the
     *        error INCOMPATIBLE_PURPOSE, INCOMPATIBLE_PADDING_MODE, or INCOMPATIBLE_DIGEST if any
     *        of those requirements fail.
     *     2. Extract the encryptedTransportKey field from the SecureKeyWrapper, and decrypt
     *        it with the wrapping key.
     *     3. XOR the result of step 2 with maskingKey.
     *     4. Use the result of step 3 as an AES-GCM key to decrypt encryptedKey, using the encoded
     *        value of keyDescription as the additional authenticated data.  Call the result
     *        "keyData" for the next step.
     *     5. Perform the equivalent of calling importKey(keyParams, keyFormat, keyData), except
     *        that the origin tag should be set to SECURELY_IMPORTED.
     *
     * @param wrappingKeyBlob The opaque key descriptor returned by generateKey() or importKey().
     *        This key must have been created with Purpose::WRAP_KEY.
     *
     * @param maskingKey The 32-byte value XOR'd with the transport key in the SecureWrappedKey
     *        structure.
     *
     * @param unwrappingParams must contain any parameters needed to perform the unwrapping
     *        operation.  For example, if the wrapping key is an AES key the block and padding modes
     *        must be specified in this argument.
     *
     * @param passwordSid specifies the password secure ID (SID) of the user that owns the key being
     *        installed.  If the authorization list in wrappedKeyData contains a
     *        Tag::USER_SECURE_IDwith a value that has the HardwareAuthenticatorType::PASSWORD bit
     *        set, the constructed key must be bound to the SID value provided by this argument.  If
     *        the wrappedKeyData does not contain such a tag and value, this argument must be
     *        ignored.
     *
     * @param biometricSid specifies the biometric secure ID (SID) of the user that owns the key
     *        being installed.  If the authorization list in wrappedKeyData contains a
     *        Tag::USER_SECURE_ID with a value that has the HardwareAuthenticatorType::FINGERPRINT
     *        bit set, the constructed key must be bound to the SID value provided by this argument.
     *        If the wrappedKeyData does not contain such a tag and value, this argument must be
     *        ignored.
     *
     * @return The result of key creation.  See KeyCreationResult.aidl.
     */
     KeyCreationResult importWrappedKey(in byte[] wrappedKeyData,
                                        in byte[] wrappingKeyBlob,
                                        in byte[] maskingKey,
                                        in KeyParameter[] unwrappingParams,
                                        in long passwordSid,
                                        in long biometricSid);

    /**
     * Upgrades an old key blob.  Keys can become "old" in two ways: IKeyMintDevice can be
     * upgraded to a new version with an incompatible key blob format, or the system can be updated
     * to invalidate the OS version (OS_VERSION tag), system patch level (OS_PATCHLEVEL tag),
     * vendor patch level (VENDOR_PATCH_LEVEL tag), boot patch level (BOOT_PATCH_LEVEL tag) or
     * other, implementation-defined patch level (keyMint implementers are encouraged to extend
     * this HAL with a minor version extension to define validatable patch levels for other
     * images; tags must be defined in the implementer's namespace, starting at 10000).  In either
     * case, attempts to use an old key blob with begin() must result in IKeyMintDevice returning
     * ErrorCode::KEY_REQUIRES_UPGRADE.  The caller must use this method to upgrade the key blob.
     *
     * The upgradeKey method must examine each version or patch level associated with the key.  If
     * any one of them is higher than the corresponding current device value upgradeKey() must
     * return ErrorCode::INVALID_ARGUMENT.  There is one exception: it is always permissible to
     * "downgrade" from any OS_VERSION number to OS_VERSION 0.  For example, if the key has
     * OS_VERSION 080001, it is permisible to upgrade the key if the current system version is
     * 080100, because the new version is larger, or if the current system version is 0, because
     * upgrades to 0 are always allowed.  If the system version were 080000, however, keyMint must
     * return ErrorCode::INVALID_ARGUMENT because that value is smaller than 080001.  Values other
     * than OS_VERSION must never be downgraded.
     *
     * Note that Keymaster versions 2 and 3 required that the system and boot images have the same
     * patch level and OS version.  This requirement is relaxed for 4.0::IKeymasterDevice and
     * IKeyMintDevice, and the OS version in the boot image footer is no longer used.
     *
     * @param inKeyBlobToUpgrade The opaque descriptor returned by generateKey() or importKey();
     *
     * @param inUpgradeParams A parameter list containing any parameters needed to complete the
     *        upgrade, including Tag::APPLICATION_ID and Tag::APPLICATION_DATA.
     *
     * @return A new key blob that references the same key as keyBlobToUpgrade, but is in the new
     *         format, or has the new version data.
     */
    byte[] upgradeKey(in byte[] inKeyBlobToUpgrade, in KeyParameter[] inUpgradeParams);

    /**
     * Deletes the key, or key pair, associated with the key blob.  Calling this function on
     * a key with Tag::ROLLBACK_RESISTANCE in its hardware-enforced authorization list must
     * render the key permanently unusable.  Keys without Tag::ROLLBACK_RESISTANCE may or
     * may not be rendered unusable.
     *
     * @param inKeyBlob The opaque descriptor returned by generateKey() or importKey();
     */
    void deleteKey(in byte[] inKeyBlob);

    /**
     * Deletes all keys in the hardware keystore.  Used when keystore is reset completely.  After
     * this function is called all keys with Tag::ROLLBACK_RESISTANCE in their hardware-enforced
     * authorization lists must be rendered permanently unusable.  Keys without
     * Tag::ROLLBACK_RESISTANCE may or may not be rendered unusable.
     *
     * @return error See the ErrorCode enum.
     */
    void deleteAllKeys();

    /**
     * Destroys knowledge of the device's ids.  This prevents all device id attestation in the
     * future.  The destruction must be permanent so that not even a factory reset will restore the
     * device ids.
     *
     * Device id attestation may be provided only if this method is fully implemented, allowing the
     * user to permanently disable device id attestation.  If this cannot be guaranteed, the device
     * must never attest any device ids.
     *
     * This is a NOP if device id attestation is not supported.
     */
    void destroyAttestationIds();

    /**
     * Begins a cryptographic operation using the specified key.  If all is well, begin() must
     * return ErrorCode::OK and create an operation handle which must be passed to subsequent calls
     * to update(), finish() or abort().
     *
     * It is critical that each call to begin() be paired with a subsequent call to finish() or
     * abort(), to allow the IKeyMintDevice implementation to clean up any internal operation
     * state.  The caller's failure to do this may leak internal state space or other internal
     * resources and may eventually cause begin() to return ErrorCode::TOO_MANY_OPERATIONS when it
     * runs out of space for operations.  Any result other than ErrorCode::OK from begin(), update()
     * or finish() implicitly aborts the operation, in which case abort() need not be called (and
     * must return ErrorCode::INVALID_OPERATION_HANDLE if called).  IKeyMintDevice implementations
     * must support 32 concurrent operations.
     *
     * If Tag::APPLICATION_ID or Tag::APPLICATION_DATA were specified during key generation or
     * import, calls to begin must include those tags with the originally-specified values in the
     * inParams argument to this method.  If not, begin() must return ErrorCode::INVALID_KEY_BLOB.
     *
     * == Authorization Enforcement ==
     *
     * The following key authorization parameters must be enforced by the IKeyMintDevice secure
     * environment if the tags were returned in the "hardwareEnforced" list in the
     * KeyCharacteristics.  Public key operations, meaning KeyPurpose::ENCRYPT and
     * KeyPurpose::VERIFY must be allowed to succeed even if authorization requirements are not met.
     *
     * -- All Key Types --
     *
     * The tags in this section apply to all key types.  See below for additional key type-specific
     * tags.
     *
     * o Tag::PURPOSE: The purpose specified in the begin() call must match one of the purposes in
     *   the key authorizations.  If the specified purpose does not match, begin() must return
     *   ErrorCode::UNSUPPORTED_PURPOSE.
     *
     * o Tag::ACTIVE_DATETIME can only be enforced if a trusted UTC time source is available.  If
     *   the current date and time is prior to the tag value, begin() must return
     *   ErrorCode::KEY_NOT_YET_VALID.
     *
     * o Tag::ORIGINATION_EXPIRE_DATETIME can only be enforced if a trusted UTC time source is
     *   available.  If the current date and time is later than the tag value and the purpose is
     *   KeyPurpose::ENCRYPT or KeyPurpose::SIGN, begin() must return ErrorCode::KEY_EXPIRED.
     *
     * o Tag::USAGE_EXPIRE_DATETIME can only be enforced if a trusted UTC time source is
     *   available.  If the current date and time is later than the tag value and the purpose is
     *   KeyPurpose::DECRYPT or KeyPurpose::VERIFY, begin() must return ErrorCode::KEY_EXPIRED.
     *
     * o Tag::MAX_USES_PER_BOOT must be compared against a secure counter that tracks the uses of
     *   the key since boot time.  If the count of previous uses exceeds the tag value, begin() must
     *   return ErrorCode::KEY_MAX_OPS_EXCEEDED.
     *
     * o Tag::USER_SECURE_ID must be enforced by this method if and only if the key also has
     *   Tag::AUTH_TIMEOUT (if it does not have Tag::AUTH_TIMEOUT, the Tag::USER_SECURE_ID
     *   requirement must be enforced by update() and finish()).  If the key has both, then this
     *   method must receive a non-empty HardwareAuthToken in the authToken argument.  For the auth
     *   token to be valid, all of the following have to be true:
     *
     *   o The HMAC field must validate correctly.
     *
     *   o At least one of the Tag::USER_SECURE_ID values from the key must match at least one of
     *     the secure ID values in the token.
     *
     *   o The key must have a Tag::USER_AUTH_TYPE that matches the auth type in the token.
     *
     *   o The timestamp in the auth token plus the value of the Tag::AUTH_TIMEOUT must be less than
     *     the current secure timestamp (which is a monotonic timer counting milliseconds since
     *     boot.)
     *
     *   If any of these conditions are not met, begin() must return
     *   ErrorCode::KEY_USER_NOT_AUTHENTICATED.
     *
     * o Tag::CALLER_NONCE allows the caller to specify a nonce or initialization vector (IV).  If
     *   the key doesn't have this tag, but the caller provided Tag::NONCE to this method,
     *   ErrorCode::CALLER_NONCE_PROHIBITED must be returned.
     *
     * o Tag::BOOTLOADER_ONLY specifies that only the bootloader may use the key.  If this method is
     *   called with a bootloader-only key after the bootloader has finished executing, it must
     *   return ErrorCode::INVALID_KEY_BLOB.  The mechanism for notifying the IKeyMintDevice that
     *   the bootloader has finished executing is implementation-defined.
     *
     * -- RSA Keys --
     *
     * All RSA key operations must specify exactly one padding mode in inParams.  If unspecified or
     * specified more than once, the begin() must return ErrorCode::UNSUPPORTED_PADDING_MODE.
     *
     * RSA signing and verification operations need a digest, as do RSA encryption and decryption
     * operations with OAEP padding mode.  For those cases, the caller must specify exactly one
     * digest in inParams.  If unspecified or specified more than once, begin() must return
     * ErrorCode::UNSUPPORTED_DIGEST.
     *
     * Private key operations (KeyPurpose::DECRYPT and KeyPurpose::SIGN) need authorization of
     * digest and padding, which means that the key authorizations need to contain the specified
     * values.  If not, begin() must return ErrorCode::INCOMPATIBLE_DIGEST or
     * ErrorCode::INCOMPATIBLE_PADDING, as appropriate.  Public key operations (KeyPurpose::ENCRYPT
     * and KeyPurpose::VERIFY) are permitted with unauthorized digest or padding modes.
     *
     * With the exception of PaddingMode::NONE, all RSA padding modes are applicable only to certain
     * purposes.  Specifically, PaddingMode::RSA_PKCS1_1_5_SIGN and PaddingMode::RSA_PSS only
     * support signing and verification, while PaddingMode::RSA_PKCS1_1_5_ENCRYPT and
     * PaddingMode::RSA_OAEP only support encryption and decryption.  begin() must return
     * ErrorCode::UNSUPPORTED_PADDING_MODE if the specified mode does not support the specified
     * purpose.
     *
     * There are some important interactions between padding modes and digests:
     *
     * o PaddingMode::NONE indicates that a "raw" RSA operation is performed.  If signing or
     *   verifying, Digest::NONE is specified for the digest.  No digest is necessary for unpadded
     *   encryption or decryption.
     *
     * o PaddingMode::RSA_PKCS1_1_5_SIGN padding requires a digest.  The digest may be Digest::NONE,
     *   in which case the KeyMint implementation cannot build a proper PKCS#1 v1.5 signature
     *   structure, because it cannot add the DigestInfo structure.  Instead, the IKeyMintDevice
     *   must construct 0x00 || 0x01 || PS || 0x00 || M, where M is the provided message and PS is a
     *   random padding string at least eight bytes in length.  The size of the RSA key has to be at
     *   least 11 bytes larger than the message, otherwise begin() must return
     *   ErrorCode::INVALID_INPUT_LENGTH.
     *
     * o PaddingMode::RSA_PKCS1_1_1_5_ENCRYPT padding does not require a digest.
     *
     * o PaddingMode::RSA_PSS padding requires a digest, which may not be Digest::NONE.  If
     *   Digest::NONE is specified, the begin() must return ErrorCode::INCOMPATIBLE_DIGEST.  In
     *   addition, the size of the RSA key must be at least 2 + D bytes larger than the output size
     *   of the digest, where D is the size of the digest, in bytes.  Otherwise begin() must
     *   return ErrorCode::INCOMPATIBLE_DIGEST.  The salt size must be D.
     *
     * o PaddingMode::RSA_OAEP padding requires a digest, which may not be Digest::NONE.  If
     *   Digest::NONE is specified, begin() must return ErrorCode::INCOMPATIBLE_DIGEST.  The OAEP
     *   mask generation function must be MGF1 and the MGF1 digest must be SHA1, regardless of the
     *   OAEP digest specified.
     *
     * -- EC Keys --
     *
     * EC key operations must specify exactly one padding mode in inParams.  If unspecified or
     * specified more than once, begin() must return ErrorCode::UNSUPPORTED_PADDING_MODE.
     *
     * Private key operations (KeyPurpose::SIGN) need authorization of digest and padding, which
     * means that the key authorizations must contain the specified values.  If not, begin() must
     * return ErrorCode::INCOMPATIBLE_DIGEST.  Public key operations (KeyPurpose::VERIFY) are
     * permitted with unauthorized digest or padding.
     *
     * -- AES Keys --
     *
     * AES key operations must specify exactly one block mode (Tag::BLOCK_MODE) and one padding mode
     * (Tag::PADDING) in inParams.  If either value is unspecified or specified more than once,
     * begin() must return ErrorCode::UNSUPPORTED_BLOCK_MODE or
     * ErrorCode::UNSUPPORTED_PADDING_MODE.  The specified modes must be authorized by the key,
     * otherwise begin() must return ErrorCode::INCOMPATIBLE_BLOCK_MODE or
     * ErrorCode::INCOMPATIBLE_PADDING_MODE.
     *
     * If the block mode is BlockMode::GCM, inParams must specify Tag::MAC_LENGTH, and the specified
     * value must be a multiple of 8 that is not greater than 128 or less than the value of
     * Tag::MIN_MAC_LENGTH in the key authorizations.  For MAC lengths greater than 128 or
     * non-multiples of 8, begin() must return ErrorCode::UNSUPPORTED_MAC_LENGTH.  For values less
     * than the key's minimum length, begin() must return ErrorCode::INVALID_MAC_LENGTH.
     *
     * If the block mode is BlockMode::GCM or BlockMode::CTR, the specified padding mode must be
     * PaddingMode::NONE.  For BlockMode::ECB or BlockMode::CBC, the mode may be PaddingMode::NONE
     * or PaddingMode::PKCS7.  If the padding mode doesn't meet these conditions, begin() must
     * return ErrorCode::INCOMPATIBLE_PADDING_MODE.
     *
     * If the block mode is BlockMode::CBC, BlockMode::CTR, or BlockMode::GCM, an initialization
     * vector or nonce is required.  In most cases, callers shouldn't provide an IV or nonce and the
     * IKeyMintDevice implementation must generate a random IV or nonce and return it via
     * Tag::NONCE in outParams.  CBC and CTR IVs are 16 bytes.  GCM nonces are 12 bytes.  If the key
     * authorizations contain Tag::CALLER_NONCE, then the caller may provide an IV/nonce with
     * Tag::NONCE in inParams.  If a nonce is provided when Tag::CALLER_NONCE is not authorized,
     * begin() must return ErrorCode::CALLER_NONCE_PROHIBITED.  If a nonce is not provided when
     * Tag::CALLER_NONCE is authorized, IKeyMintDevice msut generate a random IV/nonce.
     *
     * -- HMAC keys --
     *
     * HMAC key operations must specify Tag::MAC_LENGTH in inParams.  The specified value must be a
     * multiple of 8 that is not greater than the digest length or less than the value of
     * Tag::MIN_MAC_LENGTH in the key authorizations.  For MAC lengths greater than the digest
     * length or non-multiples of 8, begin() must return ErrorCode::UNSUPPORTED_MAC_LENGTH.  For
     * values less than the key's minimum length, begin() must return ErrorCode::INVALID_MAC_LENGTH.
     *
     * @param inPurpose The purpose of the operation, one of KeyPurpose::ENCRYPT,
     *        KeyPurpose::DECRYPT, KeyPurpose::SIGN or KeyPurpose::VERIFY.  Note that for AEAD
     *        modes, encryption and decryption imply signing and verification, respectively, but
     *        must be specified as KeyPurpose::ENCRYPT and KeyPurpose::DECRYPT.
     *
     * @param inKeyBlob The opaque key descriptor returned by generateKey() or importKey().  The key
     *        must have a purpose compatible with purpose and all of its usage requirements must be
     *        satisfied, or begin() must return an appropriate error code (see above).
     *
     * @param inParams Additional parameters for the operation.  If Tag::APPLICATION_ID or
     *        Tag::APPLICATION_DATA were provided during generation, they must be provided here, or
     *        the operation must fail with ErrorCode::INVALID_KEY_BLOB.  For operations that require
     *        a nonce or IV, on keys that were generated with Tag::CALLER_NONCE, inParams may
     *        contain a tag Tag::NONCE.  If Tag::NONCE is provided for a key without
     *        Tag:CALLER_NONCE, ErrorCode::CALLER_NONCE_PROHIBITED must be returned.
     *
     * @param inAuthToken Authentication token.  Callers that provide no token must set all numeric
     *        fields to zero and the MAC must be an empty vector.  TODO: make this field nullable.
     *        b/173483024.
     *
     * @return BeginResult as output, which contains the challenge, KeyParameters which haves
     *         additional data from the operation initialization, notably to return the IV or nonce
     *         from operations that generate an IV or nonce, and IKeyMintOperation object pointer
     *         which is used to perform update(), finish() or abort() operations.
     */
    BeginResult begin(in KeyPurpose inPurpose,
               in byte[] inKeyBlob,
               in KeyParameter[] inParams,
               in HardwareAuthToken inAuthToken);
}