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/*
* Copyright (C) 2017 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.keymaster@4.0;
import android.hardware.keymaster@3.0::ErrorCode;
import android.hardware.keymaster@3.0::KeyFormat;
/**
* Keymaster device definition.
*
* == Features ==
*
* An IKeymasterDevice provides cryptographic services, including the following categories of
* operations:
*
* o Key generation
* o Import and export (public only) of asymmetric keys
* o Import of raw symmetric keys
* o Asymmetric encryption and decryption with appropriate padding modes
* o Asymmetric signing and verification 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, IKeymasterDevice 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 IKeymasterDevices ==
*
* 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 (SPU). 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 IKeymasterDevice implementations must provide support for the following:
*
* o RSA
*
* - TRUSTED_ENVIRONMENT IKeymasterDevices must support 2048, 3072 and 4096-bit keys.
* STRONGBOX IKeymasterDevices 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 IKeymasterDevices must support MD5, SHA1, SHA-2 224, SHA-2 256, SHA-2
* 384 and SHA-2 512 digest modes for RSA signing. STRONGBOX IKeymasterDevices must support
* SHA-2 256.
* - Unpadded, RSAES-OAEP and RSAES-PKCS1-v1_5 padding modes for RSA encryption.
*
* o ECDSA
*
* - TRUSTED_ENVIRONMENT IKeymasterDevices must support NIST curves P-224, P-256, P-384 and
* P-521. STRONGBOX IKeymasterDevices must support NIST curve P-256.
* - TRUSTED_ENVIRONMENT IKeymasterDevices must support SHA1, SHA-2 224, SHA-2 256, SHA-2
* 384 and SHA-2 512 digest modes. STRONGBOX IKeymasterDevices 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 IKeymasterDevices must not support keys larger than 512 bits.
* - TRUSTED_ENVIRONMENT IKeymasterDevices must support MD-5, SHA1, SHA-2-224, SHA-2-256,
* SHA-2-384 and SHA-2-512. STRONGBOX IKeymasterDevices 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, IKeymasterDevice must enforce access controls.
*
* Access controls are defined as an "authorization list" 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 an authorization list. The IKeymasterDevice must divide the
* caller-provided authorizations into two lists, those it enforces in hardware and those it does
* not. These two lists are returned as the "hardwareEnforced" and "softwareEnforced" elements of
* the KeyCharacteristics struct. The IKeymasterDevice must also add the following authorizations
* to the appropriate list:
*
* o Tag::OS_VERSION, must be hardware-enforced.
* o Tag::OS_PATCHLEVEL, must be hardware-enforced.
* o Tag::VENDOR_PATCHLEVEL, must be hardware-enforced.
* o Tag::BOOT_PATCHLEVEL, must be hardware-enforced.
* o Tag::CREATION_DATETIME, must be software-enforced, unless the IKeymasterDevice has access to
* a secure time service.
* o Tag::ORIGIN, must be hardware-enforced.
*
* The IKeymasterDevice must accept arbitrary, unknown tags and return them in the softwareEnforced
* list.
*
* All authorization tags and their values, both hardwareEnforced and softwareEnforced, including
* unknown tags, 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 that is used to encrypt the
* private/secret key material.
*
* IKeymasterDevice implementations must place any tags they cannot fully and completely enforce in
* the softwareEnforced list. 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
* IKeymasterDevice has access to a secure source of current date/time information, it is not
* possible for the IKeymasterDevice to enforce this tag. An IKeymasterDevice implementation may
* 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.
*
* It is recommended that IKeymasterDevices not enforce any tags they place in the softwareEnforced
* list. The IKeymasterDevice caller must enforce them, and it is unnecessary to enforce them
* twice.
*
* Some tags must be enforced by the IKeymasterDevice. See the detailed documentation on each Tag
* in types.hal.
*
* == Root of Trust Binding ==
*
* IKeymasterDevice 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 IKeymasterDevice. 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 encrypt 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 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 IKeymasterDevice-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 IKeymasterDevice 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 IKeymasterDevice::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
* IKeymasterDevice key, as described in the Key Access Control section above.
*/
interface IKeymasterDevice {
/**
* Returns information about the underlying IKeymasterDevice hardware.
*
* @return security level of the IKeymasterDevice implementation accessed through this HAL.
*
* @return keymasterName is the name of the IKeymasterDevice implementation.
*
* @return keymasterAuthorName is the name of the author of the IKeymasterDevice implementation
* (organization name, not individual).
*/
getHardwareInfo()
generates (SecurityLevel securityLevel, string keymasterName, string keymasterAuthorName);
/**
* Start the creation of an HMAC key, shared with another IKeymasterDevice implementation. Any
* device with a StrongBox IKeymasterDevice has two IKeymasterDevice instances, because there
* must be a TEE Keymaster as well. The HMAC key used to MAC and verify authentication tokens
* (HardwareAuthToken, VerificationToken and ConfirmationToken all use this HMAC key) must be
* shared between TEE and StrongBox so they can each validate tokens produced by the other.
* This method is the first step in the process for agreeing on a shared key. It is called by
* Android during startup. The system calls it on each of the HAL instances and collects the
* results in preparation for the second step.
*
* @return error ErrorCode::OK on success, ErrorCode::UNIMPLEMENTED if HMAC agreement is not
* implemented (note that all 4.0::IKeymasterDevice HALS must implement HMAC agreement,
* regardless of whether or not the HAL will be used on a device with StrongBox), or
* ErrorCode::UNKNOWN_ERROR if the parameters cannot be returned.
*
* @return params The HmacSharingParameters to use. As specified in the HmacSharingParameters
* documentation in types.hal, the seed must contain the same value in every invocation
* of the method on a given device, and the nonce must return the same value for every
* invocation during a boot session.
*/
getHmacSharingParameters() generates (ErrorCode error, HmacSharingParameters params);
/**
* Complete the creation of an HMAC key, shared with another IKeymasterDevice implementation.
* Any device with a StrongBox IKeymasterDevice has two IKeymasterDevice instances, because
* there must be a TEE IKeymasterDevice as well. The HMAC key used to MAC and verify
* authentication tokens must be shared between TEE and StrongBox so they can each validate
* tokens produced by the other. This method is the second and final step in the process for
* agreeing on a shared key. It is called by Android during startup. The system calls it on
* each of the HAL instances, and sends to it all of the HmacSharingParameters returned by all
* HALs.
*
* To ensure consistent ordering of the HmacSharingParameters, the caller must sort the
* parameters lexicographically. See the support/keymaster_utils.cpp for an operator< that
* defines the appropriate ordering.
*
* This method computes the shared 32-byte HMAC ``H'' as follows (all IKeymasterDevice instances
* perform the same computation to arrive at the same result):
*
* H = CKDF(key = K,
* context = P1 || P2 || ... || Pn,
* label = "KeymasterSharedMac")
*
* where:
*
* ``CKDF'' is the standard AES-CMAC KDF from NIST SP 800-108 in counter mode (see Section
* 5.1 of the referenced publication). ``key'', ``context'', and ``label'' are
* defined in the standard. The counter is prefixed and length L appended, as shown
* in the construction on page 12 of the standard. The label string is UTF-8 encoded.
*
* ``K'' is a pre-established shared secret, set up during factory reset. The mechanism for
* establishing this shared secret is implementation-defined, but see below for a
* recommended approach, which assumes that the TEE IKeymasterDevice does not have
* storage available to it, but the StrongBox IKeymasterDevice does.
*
* CRITICAL SECURITY REQUIREMENT: All keys created by a IKeymasterDevice instance must
* be cryptographically bound to the value of K, such that establishing a new K
* permanently destroys them.
*
* ``||'' represents concatenation.
*
* ``Pi'' is the i'th HmacSharingParameters value in the params vector. Note that at
* present only two IKeymasterDevice implementations are supported, but this mechanism
* extends without modification to any number of implementations. Encoding of an
* HmacSharingParameters is the concatenation of its two fields, i.e. seed || nonce.
*
* Note that the label "KeymasterSharedMac" is the 18-byte UTF-8 encoding of the string.
*
* Process for establishing K:
*
* Any method of securely establishing K that ensures that an attacker cannot obtain or
* derive its value is acceptable. What follows is a recommended approach, to be executed
* during each factory reset. It relies on use of the factory-installed attestation keys to
* mitigate man-in-the-middle attacks. This protocol requires that one of the instances
* have secure persistent storage. This model was chosen because StrongBox has secure
* persistent storage (by definition), but the TEE may not. The instance without storage is
* assumed to be able to derive a unique hardware-bound key (HBK) which is used only for
* this purpose, and is not derivable outside the secure environment.
*
* In what follows, T is the IKeymasterDevice instance without storage, S is the
* IKeymasterDevice instance with storage:
*
* 1. T generates an ephemeral EC P-256 key pair K1.
* 2. T sends K1_pub to S, signed with T's attestation key.
* 3. S validates the signature on K1_pub.
* 4. S generates an ephemeral EC P-256 key pair K2.
* 5. S sends {K1_pub, K2_pub}, to T, signed with S's attestation key.
* 6. T validates the signature on {K1_pub, K2_pub}.
* 7. T uses {K1_priv, K2_pub} with ECDH to compute session secret Q.
* 8. T generates a random seed S.
* 9. T computes K = KDF(HBK, S), where KDF is some secure key derivation function.
* 10. T sends M = AES-GCM-ENCRYPT(Q, {S || K}) to S.
* 10. S uses {K2_priv, K1_pub} with ECDH to compute session secret Q.
* 11. S computes S || K = AES-GCM-DECRYPT(Q, M) and stores S and K.
*
* When S receives the getHmacSharingParameters call, it returns the stored S as the seed
* and a nonce. When T receives the same call, it returns an empty seed and a nonce. When
* T receives the computeSharedHmac call, it uses the seed provided by S to compute K. S,
* of course, has K stored.
*
* @param params The HmacSharingParameters data returned by all IKeymasterDevice instances when
* getHmacSharingParameters was called.
*
* @return error ErrorCode::OK in the event that there is no error. ErrorCode::INVALID_ARGUMENT
* if one of the provided parameters is not the value returned by the prior call to
* getHmacParameters().
*
* @return sharingCheck A 32-byte value used to verify that all IKeymasterDevice instances have
* computed the same shared HMAC key. The sharingCheck value is computed as follows:
*
* sharingCheck = HMAC(H, "Keymaster HMAC Verification")
*
* The string is UTF-8 encoded, 27 bytes in length. If the returned values of all
* IKeymasterDevice instances don't match, clients must assume that HMAC agreement
* failed.
*/
computeSharedHmac(vec<HmacSharingParameters> params)
generates (ErrorCode error, vec<uint8_t> sharingCheck);
/**
* Verify authorizations for another IKeymasterDevice instance.
*
* On systems with both a StrongBox and a TEE IKeymasterDevice instance it is sometimes useful
* to ask the TEE IKeymasterDevice to verify authorizations for a key hosted in StrongBox.
*
* For every StrongBox operation, Keystore is required to call this method on the TEE Keymaster,
* passing in the StrongBox key's hardwareEnforced authorization list and the operation handle
* returned by StrongBox begin(). The TEE IKeymasterDevice must validate all of the
* authorizations it can and return those it validated in the VerificationToken. If it cannot
* verify any, the parametersVerified field of the VerificationToken must be empty. Keystore
* must then pass the VerificationToken to the subsequent invocations of StrongBox update() and
* finish().
*
* StrongBox implementations must return ErrorCode::UNIMPLEMENTED.
*
* @param operationHandle the operation handle returned by StrongBox Keymaster's begin().
*
* @param parametersToVerify Set of authorizations to verify. The caller may provide an empty
* vector if the only required information is the TEE timestamp.
*
* @param authToken A HardwareAuthToken if needed to authorize key usage.
*
* @return error ErrorCode::OK on success or ErrorCode::UNIMPLEMENTED if the IKeymasterDevice is
* a StrongBox. If the IKeymasterDevice 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 types.hal for details.
*/
verifyAuthorization(uint64_t operationHandle, vec<KeyParameter> parametersToVerify,
HardwareAuthToken authToken)
generates (ErrorCode error, VerificationToken token);
/**
* Adds entropy to the RNG used by Keymaster. 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.
*
* @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.
*/
addRngEntropy(vec<uint8_t> data) generates (ErrorCode error);
/**
* Generates a new cryptographic key, specifying associated parameters, which must be
* cryptographically bound to the key. IKeymasterDevice 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 environment's
* obligation is limited to ensuring that the unenforceable parameters associated with the key
* cannot be modified, so that every call to getKeyCharacteristics returns the original
* values. In addition, the characteristics returned by generateKey places parameters correctly
* in the hardware-enforced and software-enforced lists. See getKeyCharacteristics for more
* details.
*
* 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
* types.hal).
*
* o Tag::CREATION_DATETIME with the appropriate value. Note that it is expected that this will
* generally be added by the HAL, not by the secure environment, and that it will be in the
* software-enforced list. It must be cryptographically bound to the key, like all tags.
*
* 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 IKeymasterDevice
* implementations are 1024, 2048, 3072 and 4096. StrongBox IKeymasterDevice 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 types.hal) must be
* supported for RSA keys.
*
* o Tag::DIGEST specifies digest algorithms that may be used with the new key. TEE
* IKeymasterDevice implementations must support all Digest values (see types.hal) for RSA
* keys. StrongBox IKeymasterDevice implementations must support SHA_2_256.
*
* o Tag::PADDING specifies the padding modes that may be used with the new
* key. IKeymasterDevice 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 IKeymasterDevice 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 IKeymasterDevice tag/value pairs,
* provided in params. See above for detailed specifications of which tags are required
* for which types of keys.
*
* @return keyBlob Opaque descriptor of the generated key. The recommended implementation
* strategy is to include an encrypted copy of the key material, wrapped in a key
* unavailable outside secure hardware.
*
* @return keyCharacteristics Description of the generated key. See the getKeyCharacteristics
* method below.
*/
generateKey(vec<KeyParameter> keyParams)
generates (ErrorCode error, vec<uint8_t> keyBlob, KeyCharacteristics keyCharacteristics);
/**
* Imports key material into an IKeymasterDevice. 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
* IKeymasterDevice 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 IKeymasterDevice 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 IKeymasterDevice 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 IKeymasterDevice 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 keyParams Key generation parameters are defined as IKeymasterDevice tag/value pairs,
* provided in params.
*
* @param keyFormat The format of the key material to import. See KeyFormat in types.hal.
*
* @pram keyData The key material to import, in the format specified in keyFormat.
*
* @return keyBlob Opaque descriptor of the imported key. The recommended implementation
* strategy is to include an encrypted copy of the key material, wrapped in a key
* unavailable outside secure hardware.
*
* @return keyCharacteristics Description of the generated key. See the getKeyCharacteristics
* method below.
*/
importKey(vec<KeyParameter> keyParams, KeyFormat keyFormat, vec<uint8_t> keyData)
generates (ErrorCode error, vec<uint8_t> keyBlob, KeyCharacteristics keyCharacteristics);
/**
* Securely imports a key, or key pair, returning a key blob and a description of the imported
* key.
*
* @param wrappedKeyData The wrapped key material to import. The wrapped key is in DER-encoded
* ASN.1 format, specified by the following schema:
*
* 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 @3.0::IKeymasterDevice::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
* appropriate error 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_ID
* with 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 keyBlob Opaque descriptor of the imported key. It is recommended that the keyBlob
* contain a copy of the key material, wrapped in a key unavailable outside secure
* hardware.
*/
importWrappedKey(vec<uint8_t> wrappedKeyData, vec<uint8_t> wrappingKeyBlob,
vec<uint8_t> maskingKey, vec<KeyParameter> unwrappingParams,
uint64_t passwordSid, uint64_t biometricSid)
generates(ErrorCode error, vec<uint8_t> keyBlob, KeyCharacteristics keyCharacteristics);
/**
* Returns parameters associated with the provided key, divided into two sets: hardware-enforced
* and software-enforced. The description here applies equally to the key characteristics lists
* returned by generateKey, importKey and importWrappedKey. The characteristics returned by
* this method completely describe the type and usage of the specified key.
*
* The rule that IKeymasterDevice implementations must use for deciding whether a given tag
* belongs in the hardware-enforced or software-enforced list is that if the meaning of the tag
* is fully assured by secure hardware, it is hardware enforced. Otherwise, it's software
* enforced.
*
*
* @param keyBlob The opaque descriptor returned by generateKey, importKey or importWrappedKey.
*
* @param clientId An opaque byte string identifying the client. This value must match the
* Tag::APPLICATION_ID data provided during key generation/import. Without the correct
* value, it must be computationally infeasible for the secure hardware to obtain the key
* material.
*
* @param appData An opaque byte string provided by the application. This value must match the
* Tag::APPLICATION_DATA data provided during key generation/import. Without the correct
* value, it must be computationally infeasible for the secure hardware to obtain the key
* material.
*
* @return keyCharacteristics Description of the generated key. See KeyCharacteristics in
* types.hal.
*/
getKeyCharacteristics(vec<uint8_t> keyBlob, vec<uint8_t> clientId, vec<uint8_t> appData)
generates (ErrorCode error, KeyCharacteristics keyCharacteristics);
/**
* Exports a public key, returning the key in the specified format.
*
* @parm keyFormat The format used for export. Must be KeyFormat::X509.
*
* @param keyBlob The opaque descriptor returned by generateKey() or importKey(). The
* referenced key must be asymmetric.
*
* @param clientId An opaque byte string identifying the client. This value must match the
* Tag::APPLICATION_ID data provided during key generation/import. Without the correct
* value, it must be computationally infeasible for the secure hardware to obtain the key
* material.
*
* @param appData An opaque byte string provided by the application. This value must match the
* Tag::APPLICATION_DATA data provided during key generation/import. Without the correct
* value, it must be computationally infeasible for the secure hardware to obtain the key
* material.
*
* @return keyMaterial The public key material in X.509 format.
*/
exportKey(KeyFormat keyFormat, vec<uint8_t> keyBlob, vec<uint8_t> clientId,
vec<uint8_t> appData) generates (ErrorCode error, vec<uint8_t> keyMaterial);
/**
* Generates a signed X.509 certificate chain attesting to the presence of keyToAttest in
* Keymaster.
*
* The certificates in the chain must be ordered such that each certificate is signed by the
* subsequent one, up to the root which must be self-signed. The first certificate in the chain
* signs the public key info of the attested key and must contain the following entries (see RFC
* 5280 for details on each):
*
* o version -- with value 2
*
* o serialNumber -- with value 1 (same value for all keys)
*
* o signature -- contains an the AlgorithmIdentifier of the algorithm used to sign, must be
* ECDSA for EC keys, RSA for RSA keys.
*
* o issuer -- must contain the same value as the Subject field of the next certificate.
*
* o validity -- SEQUENCE of two dates, containing the values of Tag::ACTIVE_DATETIME and
* Tag::USAGE_EXPIRE_DATETIME. The tag values are in milliseconds since Jan 1, 1970; see RFD
* 5280 for the correct representation in certificates. If Tag::ACTIVE_DATETIME is not
* present in the key, the IKeymasterDevice must use the value of Tag::CREATION_DATETIME. If
* Tag::USAGE_EXPIRE_DATETIME is not present, the IKeymasterDevice must use the expiration
* date of the batch attestation certificate (see below).
*
* o subject -- CN="Android Keystore Key" (same value for all keys)
*
* o subjectPublicKeyInfo -- X.509 SubjectPublicKeyInfo containing the attested public key.
*
* o Key Usage extension -- digitalSignature bit must be set iff the attested key has
* KeyPurpose::SIGN. dataEncipherment bit must be set iff the attested key has
* KeyPurpose::DECRYPT. keyEncipherment bit must be set iff the attested key has
* KeyPurpose::KEY_WRAP. All other bits must be clear.
*
* In addition to the above, the attestation certificate must contain an extension with OID
* 1.3.6.1.4.1.11129.2.1.17 and value according to the KeyDescription schema defined as:
*
* KeyDescription ::= SEQUENCE {
* attestationVersion INTEGER, # Value 3
* attestationSecurityLevel SecurityLevel, # See below
* keymasterVersion INTEGER, # Value 4
* keymasterSecurityLevel SecurityLevel, # See below
* attestationChallenge OCTET_STRING, # Tag::ATTESTATION_CHALLENGE from attestParams
* uniqueId OCTET_STRING, # Empty unless key has Tag::INCLUDE_UNIQUE_ID
* softwareEnforced AuthorizationList, # See below
* hardwareEnforced AuthorizationList, # See below
* }
*
* SecurityLevel ::= ENUMERATED {
* Software (0),
* TrustedEnvironment (1),
* StrongBox (2),
* }
*
* RootOfTrust ::= SEQUENCE {
* verifiedBootKey OCTET_STRING,
* deviceLocked BOOLEAN,
* verifiedBootState VerifiedBootState,
* # verifiedBootHash must contain 32-byte value that represents the state of all binaries
* # or other components validated by verified boot. Updating any verified binary or
* # component must cause this value to change.
* verifiedBootHash OCTET_STRING,
* }
*
* VerifiedBootState ::= ENUMERATED {
* Verified (0),
* SelfSigned (1),
* Unverified (2),
* Failed (3),
* }
*
* AuthorizationList ::= SEQUENCE {
* purpose [1] EXPLICIT SET OF INTEGER OPTIONAL,
* algorithm [2] EXPLICIT INTEGER OPTIONAL,
* keySize [3] EXPLICIT INTEGER OPTIONAL,
* blockMode [4] EXPLICIT SET OF INTEGER OPTIONAL,
* digest [5] EXPLICIT SET OF INTEGER OPTIONAL,
* padding [6] EXPLICIT SET OF INTEGER OPTIONAL,
* callerNonce [7] EXPLICIT NULL OPTIONAL,
* minMacLength [8] EXPLICIT INTEGER OPTIONAL,
* ecCurve [10] EXPLICIT INTEGER OPTIONAL,
* rsaPublicExponent [200] EXPLICIT INTEGER OPTIONAL,
* rollbackResistance [303] EXPLICIT NULL OPTIONAL,
* activeDateTime [400] EXPLICIT INTEGER OPTIONAL,
* originationExpireDateTime [401] EXPLICIT INTEGER OPTIONAL,
* usageExpireDateTime [402] EXPLICIT INTEGER OPTIONAL,
* userSecureId [502] EXPLICIT INTEGER OPTIONAL,
* noAuthRequired [503] EXPLICIT NULL OPTIONAL,
* userAuthType [504] EXPLICIT INTEGER OPTIONAL,
* authTimeout [505] EXPLICIT INTEGER OPTIONAL,
* allowWhileOnBody [506] EXPLICIT NULL OPTIONAL,
* trustedUserPresenceReq [507] EXPLICIT NULL OPTIONAL,
* trustedConfirmationReq [508] EXPLICIT NULL OPTIONAL,
* unlockedDeviceReq [509] EXPLICIT NULL OPTIONAL,
* creationDateTime [701] EXPLICIT INTEGER OPTIONAL,
* origin [702] EXPLICIT INTEGER OPTIONAL,
* rootOfTrust [704] EXPLICIT RootOfTrust OPTIONAL,
* osVersion [705] EXPLICIT INTEGER OPTIONAL,
* osPatchLevel [706] EXPLICIT INTEGER OPTIONAL,
* attestationApplicationId [709] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdBrand [710] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdDevice [711] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdProduct [712] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdSerial [713] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdImei [714] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdMeid [715] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdManufacturer [716] EXPLICIT OCTET_STRING OPTIONAL,
* attestationIdModel [717] EXPLICIT OCTET_STRING OPTIONAL,
* vendorPatchLevel [718] EXPLICIT INTEGER OPTIONAL,
* bootPatchLevel [719] EXPLICIT INTEGER OPTIONAL,
* }
*
* The above schema is mostly a straightforward translation of the IKeymasterDevice tag/value
* parameter lists to ASN.1:
*
* o TagType::ENUM, TagType::UINT, TagType::ULONG and TagType::DATE tags are represented as
* ASN.1 INTEGER.
*
* o TagType::ENUM_REP, TagType::UINT_REP and TagType::ULONG_REP tags are represented as ASN.1
* SET of INTEGER.
*
* o TagType::BOOL tags are represented as ASN.1 NULL. All entries in AuthorizationList are
* OPTIONAL, so the presence of the tag means "true", absence means "false".
*
* o TagType::BYTES tags are represented as ASN.1 OCTET_STRING.
*
* The numeric ASN.1 tag numbers are the same values as the IKeymasterDevice Tag enum values,
* except with the TagType modifier stripped.
*
* The attestation certificate must be signed by a "batch" key, which must be securely
* pre-installed into the device, generally in the factory, and securely stored to prevent
* access or extraction. The batch key must be used only for signing attestation certificates.
* The batch attestation certificate must be signed by a chain or zero or more intermediates
* leading to a self-signed roots. The intermediate and root certificate signing keys must not
* exist anywhere on the device.
*
* == ID Attestation ==
*
* ID attestation is a special case of key attestation in which unique device ID values are
* included in the signed attestation certificate.
*
* @param keyToAttest The opaque descriptor returned by generateKey() or importKey(). The
* referenced key must be asymmetric.
*
* @param attestParams Parameters for the attestation. Must contain Tag::ATTESTATION_CHALLENGE,
* the value of which must be put in the attestationChallenge field of the KeyDescription
* ASN.1 structure defined above.
*
* @return certChain The attestation certificate, and additional certificates back to the root
* attestation certificate, which clients will need to check against a known-good value.
* The certificates must be DER-encoded.
*/
attestKey(vec<uint8_t> keyToAttest, vec<KeyParameter> attestParams)
generates (ErrorCode error, vec<vec<uint8_t>> certChain);
/**
* Upgrades an old key blob. Keys can become "old" in two ways: IKeymasterDevice 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 (keymaster 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 getKeyCharacteristics(), exportKey(), attestKey() or begin() must
* result in IKeymasterDevice 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 permissible 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, keymaster 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 the
* OS version in the boot image footer is no longer used.
*
* @param keyBlobToUpgrade The opaque descriptor returned by generateKey() or importKey();
*
* @param upgradeParams A parameter list containing any parameters needed to complete the
* upgrade, including Tag::APPLICATION_ID and Tag::APPLICATION_DATA.
*
* @return upgradedKeyBlob A new key blob that references the same key as keyBlobToUpgrade, but
* is in the new format, or has the new version data.
*/
upgradeKey(vec<uint8_t> keyBlobToUpgrade, vec<KeyParameter> upgradeParams)
generates (ErrorCode error, vec<uint8_t> upgradedKeyBlob);
/**
* 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 keyBlob The opaque descriptor returned by generateKey() or importKey();
*/
deleteKey(vec<uint8_t> keyBlob) generates (ErrorCode error);
/**
* 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.
*/
deleteAllKeys() generates (ErrorCode error);
/**
* 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.
*/
destroyAttestationIds() generates (ErrorCode error);
/**
* 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 IKeymasterDevice 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). IKeymasterDevice implementations
* must support 16 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 IKeymasterDevice 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::MIN_SECONDS_BETWEEN_OPS must be compared with a trusted relative timer indicating the
* last use of the key. If the last use time plus the tag value is less than the current
* time, begin() must return ErrorCode::KEY_RATE_LIMIT_EXCEEDED. See the tag description for
* important implementation details.
* 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 IKeymasterDevice 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 Keymaster implementation cannot build a proper PKCS#1 v1.5 signature
* structure, because it cannot add the DigestInfo structure. Instead, the IKeymasterDevice
* 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 private key operations must specify exactly one digest in inParams. If unspecified or
* specified more than once, begin() must return ErrorCode::UNSUPPORTED_DIGEST. For private key
* operations, (KeyPurpose::SIGN), if the specified digest is not in the key's authorization
* list, begin() must return ErrorCode::INCOMPATIBLE_DIGEST. Public key operations
* (KeyPurpose::VERIFY) are permitted with unauthorized digest.
*
* -- 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
* IKeymasterDevice 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, IKeymasterDevice must 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 purpose 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 keyBlob 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 authToken Authentication token. Callers that provide no token must set all numeric
* fields to zero and the MAC must be an empty vector.
*
* @return outParams Output parameters. Used to return additional data from the operation
* initialization, notably to return the IV or nonce from operations that generate an IV
* or nonce.
*
* @return operationHandle The newly-created operation handle which must be passed to update(),
* finish() or abort().
*/
begin(KeyPurpose purpose, vec<uint8_t> keyBlob, vec<KeyParameter> inParams,
HardwareAuthToken authToken)
generates (ErrorCode error, vec<KeyParameter> outParams, OperationHandle operationHandle);
/**
* Provides data to, and possibly receives output from, an ongoing cryptographic operation begun
* with begin(). The operation is specified by the operationHandle parameter.
*
* If operationHandle is invalid, update() must return ErrorCode::INVALID_OPERATION_HANDLE.
*
* To provide more flexibility for buffer handling, implementations of this method have the
* option of consuming less data than was provided. The caller is responsible for looping to
* feed the rest of the data in subsequent calls. The amount of input consumed must be returned
* in the inputConsumed parameter. Implementations must always consume at least one byte, unless
* the operation cannot accept any more; if more than zero bytes are provided and zero bytes are
* consumed, callers must consider this an error and abort the operation.
*
* Implementations may also choose how much data to return, as a result of the update. This is
* only relevant for encryption and decryption operations, because signing and verification
* return no data until finish. It is recommended to return data as early as possible, rather
* than buffer it.
*
* If this method returns an error code other than ErrorCode::OK, the operation is aborted and
* the operation handle must be invalidated. Any future use of the handle, with this method,
* finish, or abort, must return ErrorCode::INVALID_OPERATION_HANDLE.
*
* == Authorization Enforcement ==
*
* Key authorization enforcement is performed primarily in begin(). The one exception is the
* case where the key has:
* o One or more Tag::USER_SECURE_IDs, and
*
* o Does not have a Tag::AUTH_TIMEOUT
*
* In this case, the key requires an authorization per operation, and the update method must
* receive a non-empty and valid HardwareAuthToken. For the auth token to be valid, all of the
* following has 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 challenge field in the auth token must contain the operationHandle
*
* If any of these conditions are not met, update() must return
* ErrorCode::KEY_USER_NOT_AUTHENTICATED.
*
* The caller must provide the auth token on every call to update() and finish().
*
* -- RSA keys --
*
* For signing and verification operations with Digest::NONE, this method must accept the entire
* block to be signed or verified in a single update. It may not consume only a portion of the
* block in these cases. However, the caller may choose to provide the data in multiple updates,
* and update() must accept the data this way as well. If the caller provides more data to sign
* than can be used (length of data exceeds RSA key size), update() must return
* ErrorCode::INVALID_INPUT_LENGTH.
*
* -- ECDSA keys --
*
* For signing and verification operations with Digest::NONE, this method must accept the entire
* block to be signed or verified in a single update. This method may not consume only a
* portion of the block. However, the caller may choose to provide the data in multiple updates
* and update() must accept the data this way as well. If the caller provides more data to sign
* than can be used, the data is silently truncated. (This differs from the handling of excess
* data provided in similar RSA operations. The reason for this is compatibility with legacy
* clients.)
*
* -- AES keys --
*
* AES GCM mode supports "associated authentication data," provided via the Tag::ASSOCIATED_DATA
* tag in the inParams argument. The associated data may be provided in repeated calls
* (important if the data is too large to send in a single block) but must always precede data
* to be encrypted or decrypted. An update call may receive both associated data and data to
* encrypt/decrypt, but subsequent updates must not include associated data. If the caller
* provides associated data to an update call after a call that includes data to
* encrypt/decrypt, update() must return ErrorCode::INVALID_TAG.
*
* For GCM encryption, the AEAD tag must be appended to the ciphertext by finish(). During
* decryption, the last Tag::MAC_LENGTH bytes of the data provided to the last update call must
* be the AEAD tag. Since a given invocation of update cannot know if it's the last invocation,
* it must process all but the tag length and buffer the possible tag data for processing during
* finish().
*
* @param operationHandle The operation handle returned by begin().
*
* @param inParams Additional parameters for the operation. For AEAD modes, this is used to
* specify Tag::ADDITIONAL_DATA. Note that additional data may be provided in multiple
* calls to update(), but only until input data has been provided.
*
* @param input Data to be processed. Note that update() may or may not consume all of the data
* provided. See inputConsumed.
*
* @param authToken Authentication token. Callers that provide no token must set all numeric
* fields to zero and the MAC must be an empty vector.
*
* @param verificationToken Verification token, used to prove that another IKeymasterDevice HAL
* has verified some parameters, and to deliver the other HAL's current timestamp, if
* needed. If not provided, all fields must be initialized to zero and vectors must be
* empty.
*
* @return error See the ErrorCode enum in types.hal.
*
* @return inputConsumed Amount of data that was consumed by update(). If this is less than the
* amount provided, the caller may provide the remainder in a subsequent call to
* update() or finish(). Every call to update must consume at least one byte, unless
* the input is empty, and implementations should consume as much data as reasonably
* possible for each call.
*
* @return outParams Output parameters, used to return additional data from the operation.
*
* @return output The output data, if any.
*/
update(OperationHandle operationHandle, vec<KeyParameter> inParams, vec<uint8_t> input,
HardwareAuthToken authToken, VerificationToken verificationToken)
generates (ErrorCode error, uint32_t inputConsumed, vec<KeyParameter> outParams,
vec<uint8_t> output);
/**
* Finalizes a cryptographic operation begun with begin() and invalidates operationHandle.
*
* This method is the last one called in an operation, so all processed data must be returned.
*
* Whether it completes successfully or returns an error, this method finalizes the operation
* and therefore must invalidate the provided operation handle. Any future use of the handle,
* with finish(), update(), or abort(), must return ErrorCode::INVALID_OPERATION_HANDLE.
*
* Signing operations return the signature as the output. Verification operations accept the
* signature in the signature parameter, and return no output.
*
* == Authorization enforcement ==
*
* Key authorization enforcement is performed primarily in begin(). The exceptions are
* authorization per operation keys and confirmation-required keys.
*
* Authorization per operation keys are the case where the key has one or more
* Tag::USER_SECURE_IDs, and does not have a Tag::AUTH_TIMEOUT. In this case, the key requires
* an authorization per operation, and the finish method must receive a non-empty and valid
* authToken. For the auth token to be valid, all of the following has 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 challenge field in the auth token must contain the operationHandle
*
* If any of these conditions are not met, update() must return
* ErrorCode::KEY_USER_NOT_AUTHENTICATED.
*
* The caller must provide the auth token on every call to update() and finish().
*
* Confirmation-required keys are keys that were generated with
* Tag::TRUSTED_CONFIRMATION_REQUIRED. For these keys, when doing a signing operation the
* caller must pass a KeyParameter Tag::CONFIRMATION_TOKEN to finish(). Implementations must
* check the confirmation token by computing the 32-byte HMAC-SHA256 over all of the
* to-be-signed data, prefixed with the 18-byte UTF-8 encoded string "confirmation token". If
* the computed value does not match the Tag::CONFIRMATION_TOKEN parameter, finish() must not
* produce a signature and must return ErrorCode::NO_USER_CONFIRMATION.
*
* -- RSA keys --
*
* Some additional requirements, depending on the padding mode:
*
* o PaddingMode::NONE. For unpadded signing and encryption operations, if the provided data is
* shorter than the key, the data must be zero-padded on the left before
* signing/encryption. If the data is the same length as the key, but numerically larger,
* finish() must return ErrorCode::INVALID_ARGUMENT. For verification and decryption
* operations, the data must be exactly as long as the key. Otherwise, return
* ErrorCode::INVALID_INPUT_LENGTH.
*
* o PaddingMode::RSA_PSS. For PSS-padded signature operations, the PSS salt length must match
* the size of the PSS digest selected. The digest specified with Tag::DIGEST in inputParams
* on begin() must be used as the PSS digest algorithm, MGF1 must be used as the mask
* generation function and SHA1 must be used as the MGF1 digest algorithm.
*
* o PaddingMode::RSA_OAEP. The digest specified with Tag::DIGEST in inputParams on begin is
* used as the OAEP digest algorithm, MGF1 must be used as the mask generation function and
* and SHA1 must be used as the MGF1 digest algorithm.
*
* -- ECDSA keys --
*
* If the data provided for unpadded signing or verification is too long, truncate it.
*
* -- AES keys --
*
* Some additional conditions, depending on block mode:
*
* o BlockMode::ECB or BlockMode::CBC. If padding is PaddingMode::NONE and the data length is
* not a multiple of the AES block size, finish() must return
* ErrorCode::INVALID_INPUT_LENGTH. If padding is PaddingMode::PKCS7, pad the data per the
* PKCS#7 specification, including adding an additional padding block if the data is a multiple
* of the block length.
*
* o BlockMode::GCM. During encryption, after processing all plaintext, compute the tag
* (Tag::MAC_LENGTH bytes) and append it to the returned ciphertext. During decryption,
* process the last Tag::MAC_LENGTH bytes as the tag. If tag verification fails, finish()
* must return ErrorCode::VERIFICATION_FAILED.
*
* @param operationHandle The operation handle returned by begin(). This handle must be invalid
* when finish() returns.
*
* @param inParams Additional parameters for the operation. For AEAD modes, this is used to
* specify Tag::ADDITIONAL_DATA, but only if no input data was provided to update().
*
* @param input Data to be processed, per the parameters established in the call to begin().
* finish() must consume all provided data or return ErrorCode::INVALID_INPUT_LENGTH.
*
* @param signature The signature to be verified if the purpose specified in the begin() call
* was KeyPurpose::VERIFY.
*
* @param authToken Authentication token. Callers that provide no token must set all numeric
* fields to zero and the MAC must be an empty vector.
*
* @param verificationToken Verification token, used to prove that another IKeymasterDevice HAL
* has verified some parameters, and to deliver the other HAL's current timestamp, if
* needed. If not provided, all fields must be initialized to zero and vectors empty.
*
* @return outParams Any output parameters generated by finish().
*
* @return output The output data, if any.
*/
finish(OperationHandle operationHandle, vec<KeyParameter> inParams, vec<uint8_t> input,
vec<uint8_t> signature, HardwareAuthToken authToken, VerificationToken verificationToken)
generates (ErrorCode error, vec<KeyParameter> outParams, vec<uint8_t> output);
/**
* Aborts a cryptographic operation begun with begin(), freeing all internal resources and
* invalidating operationHandle.
*
* @param operationHandle The operation handle returned by begin(). This handle must be
* invalid when abort() returns.
*
* @return error See the ErrorCode enum in types.hal.
*/
abort(OperationHandle operationHandle) generates (ErrorCode error);
};