/*
 * Copyright 2014 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.
 */

#ifndef SYSTEM_VOLD_KEYMASTER_TAGS_H_
#define SYSTEM_VOLD_KEYMASTER_TAGS_H_

/**
 * This header contains various definitions that make working with keymaster tags safer and easier.
 *
 * It makes use of a fair amount of template metaprogramming. The metaprogramming serves the purpose
 * of making it impossible to make certain classes of mistakes when operating on keymaster
 * authorizations.  For example, it's an error to create a KeyParameter with tag == Tag::PURPOSE
 * and then to assign Algorithm::RSA to algorithm element of its union. But because the user
 * must choose the union field, there could be a mismatch which the compiler has now way to
 * diagnose.
 *
 * The machinery in this header solves these problems by describing which union field corresponds
 * to which Tag. Central to this mechanism is the template TypedTag. It has zero size and binds a
 * numeric Tag to a type that the compiler understands. By means of the macro DECLARE_TYPED_TAG,
 * we declare types for each of the tags defined in hardware/interfaces/keymaster/2.0/types.hal.
 *
 * The macro DECLARE_TYPED_TAG(name) generates a typename TAG_name_t and a zero sized instance
 * TAG_name. Once these typed tags have been declared we define metafunctions mapping the each tag
 * to its value c++ type and the correct union element of KeyParameter. This is done by means of
 * the macros MAKE_TAG_*VALUE_ACCESSOR, which generates TypedTag2ValueType, a metafunction mapping
 * a typed tag to the corresponding c++ type, and access function, accessTagValue returning a
 * reference to the correct element of KeyParameter.
 * E.g.:
 *      given "KeyParameter param;" then "accessTagValue(TAG_PURPOSE, param)"
 *      yields a reference to param.f.purpose
 * If used in an assignment the compiler can now check the compatibility of the assigned value.
 *
 * For convenience we also provide the constructor like function Authorization().
 * Authorization takes a typed tag and a value and checks at compile time whether the value given
 * is suitable for the given tag. At runtime it creates a new KeyParameter initialized with the
 * given tag and value and returns it by value.
 *
 * The second convenience function, authorizationValue, allows access to the KeyParameter value in
 * a safe way. It takes a typed tag and a KeyParameter and returns a reference to the value wrapped
 * by NullOr. NullOr has out-of-band information about whether it is save to access the wrapped
 * reference.
 * E.g.:
 *      auto param = Authorization(TAG_ALGORITM, Algorithm::RSA);
 *      auto value1 = authorizationValue(TAG_PURPOSE, param);
 *      auto value2 = authorizationValue(TAG_ALGORITM, param);
 * value1.isOk() yields false, but value2.isOk() yields true, thus value2.value() is save to access.
 */

#include <android/hardware/keymaster/3.0/IHwKeymasterDevice.h>
#include <hardware/hw_auth_token.h>
#include <type_traits>

namespace keystore {

using ::android::hardware::keymaster::V3_0::Algorithm;
using ::android::hardware::keymaster::V3_0::BlockMode;
using ::android::hardware::keymaster::V3_0::Digest;
using ::android::hardware::keymaster::V3_0::EcCurve;
using ::android::hardware::keymaster::V3_0::ErrorCode;
using ::android::hardware::keymaster::V3_0::HardwareAuthToken;
using ::android::hardware::keymaster::V3_0::HardwareAuthenticatorType;
using ::android::hardware::keymaster::V3_0::IKeymasterDevice;
using ::android::hardware::keymaster::V3_0::KeyBlobUsageRequirements;
using ::android::hardware::keymaster::V3_0::KeyCharacteristics;
using ::android::hardware::keymaster::V3_0::KeyDerivationFunction;
using ::android::hardware::keymaster::V3_0::KeyFormat;
using ::android::hardware::keymaster::V3_0::KeyOrigin;
using ::android::hardware::keymaster::V3_0::KeyParameter;
using ::android::hardware::keymaster::V3_0::KeyPurpose;
using ::android::hardware::keymaster::V3_0::PaddingMode;
using ::android::hardware::keymaster::V3_0::Tag;
using ::android::hardware::keymaster::V3_0::TagType;

using ::android::hardware::hidl_vec;
using ::android::hardware::Return;

// The following create the numeric values that KM_TAG_PADDING and KM_TAG_DIGEST used to have.  We
// need these old values to be able to support old keys that use them.
static const int32_t KM_TAG_DIGEST_OLD = static_cast<int32_t>(TagType::ENUM) | 5;
static const int32_t KM_TAG_PADDING_OLD = static_cast<int32_t>(TagType::ENUM) | 7;

constexpr TagType typeFromTag(Tag tag) {
    return static_cast<TagType>(static_cast<uint32_t>(tag) & static_cast<uint32_t>(0xf0000000));
}

/**
 * TypedTag is a templatized version of Tag, which provides compile-time checking of
 * keymaster tag types. Instances are convertible to Tag, so they can be used wherever
 * Tag is expected, and because they encode the tag type it's possible to create
 * function overloads that only operate on tags with a particular type.
 */
template <TagType tag_type, Tag tag>
struct TypedTag {
    inline TypedTag() {
        // Ensure that it's impossible to create a TypedTag instance whose 'tag' doesn't have type
        // 'tag_type'.  Attempting to instantiate a tag with the wrong type will result in a compile
        // error (no match for template specialization StaticAssert<false>), with no run-time cost.
        static_assert(typeFromTag(tag) == tag_type, "mismatch between tag and tag_type");
    }
    operator Tag() const { return tag; }
};

template <Tag tag>
struct Tag2TypedTag {
    typedef TypedTag<typeFromTag(tag), tag> type;
};

template <Tag tag>
struct Tag2String;

#define _TAGS_STRINGIFY(x) #x
#define TAGS_STRINGIFY(x) _TAGS_STRINGIFY(x)

#define DECLARE_TYPED_TAG(name)                                             \
    typedef typename Tag2TypedTag<Tag::name>::type TAG_##name##_t;          \
    extern TAG_##name##_t TAG_##name;                                       \
    template <>                                                             \
    struct Tag2String<Tag::name> {                                          \
        static const char* value() { return "Tag::" TAGS_STRINGIFY(name); } \
    }

DECLARE_TYPED_TAG(INVALID);
DECLARE_TYPED_TAG(KEY_SIZE);
DECLARE_TYPED_TAG(MAC_LENGTH);
DECLARE_TYPED_TAG(CALLER_NONCE);
DECLARE_TYPED_TAG(MIN_MAC_LENGTH);
DECLARE_TYPED_TAG(RSA_PUBLIC_EXPONENT);
DECLARE_TYPED_TAG(ECIES_SINGLE_HASH_MODE);
DECLARE_TYPED_TAG(INCLUDE_UNIQUE_ID);
DECLARE_TYPED_TAG(ACTIVE_DATETIME);
DECLARE_TYPED_TAG(ORIGINATION_EXPIRE_DATETIME);
DECLARE_TYPED_TAG(USAGE_EXPIRE_DATETIME);
DECLARE_TYPED_TAG(MIN_SECONDS_BETWEEN_OPS);
DECLARE_TYPED_TAG(MAX_USES_PER_BOOT);
DECLARE_TYPED_TAG(ALL_USERS);
DECLARE_TYPED_TAG(USER_ID);
DECLARE_TYPED_TAG(USER_SECURE_ID);
DECLARE_TYPED_TAG(NO_AUTH_REQUIRED);
DECLARE_TYPED_TAG(AUTH_TIMEOUT);
DECLARE_TYPED_TAG(ALLOW_WHILE_ON_BODY);
DECLARE_TYPED_TAG(ALL_APPLICATIONS);
DECLARE_TYPED_TAG(APPLICATION_ID);
DECLARE_TYPED_TAG(APPLICATION_DATA);
DECLARE_TYPED_TAG(CREATION_DATETIME);
DECLARE_TYPED_TAG(ROLLBACK_RESISTANT);
DECLARE_TYPED_TAG(ROOT_OF_TRUST);
DECLARE_TYPED_TAG(ASSOCIATED_DATA);
DECLARE_TYPED_TAG(NONCE);
DECLARE_TYPED_TAG(AUTH_TOKEN);
DECLARE_TYPED_TAG(BOOTLOADER_ONLY);
DECLARE_TYPED_TAG(OS_VERSION);
DECLARE_TYPED_TAG(OS_PATCHLEVEL);
DECLARE_TYPED_TAG(UNIQUE_ID);
DECLARE_TYPED_TAG(ATTESTATION_CHALLENGE);
DECLARE_TYPED_TAG(ATTESTATION_APPLICATION_ID);
DECLARE_TYPED_TAG(RESET_SINCE_ID_ROTATION);

DECLARE_TYPED_TAG(PURPOSE);
DECLARE_TYPED_TAG(ALGORITHM);
DECLARE_TYPED_TAG(BLOCK_MODE);
DECLARE_TYPED_TAG(DIGEST);
DECLARE_TYPED_TAG(PADDING);
DECLARE_TYPED_TAG(BLOB_USAGE_REQUIREMENTS);
DECLARE_TYPED_TAG(ORIGIN);
DECLARE_TYPED_TAG(USER_AUTH_TYPE);
DECLARE_TYPED_TAG(KDF);
DECLARE_TYPED_TAG(EC_CURVE);

template <typename... Elems>
struct MetaList {};

using all_tags_t = MetaList<
    TAG_INVALID_t, TAG_KEY_SIZE_t, TAG_MAC_LENGTH_t, TAG_CALLER_NONCE_t, TAG_MIN_MAC_LENGTH_t,
    TAG_RSA_PUBLIC_EXPONENT_t, TAG_ECIES_SINGLE_HASH_MODE_t, TAG_INCLUDE_UNIQUE_ID_t,
    TAG_ACTIVE_DATETIME_t, TAG_ORIGINATION_EXPIRE_DATETIME_t, TAG_USAGE_EXPIRE_DATETIME_t,
    TAG_MIN_SECONDS_BETWEEN_OPS_t, TAG_MAX_USES_PER_BOOT_t, TAG_ALL_USERS_t, TAG_USER_ID_t,
    TAG_USER_SECURE_ID_t, TAG_NO_AUTH_REQUIRED_t, TAG_AUTH_TIMEOUT_t, TAG_ALLOW_WHILE_ON_BODY_t,
    TAG_ALL_APPLICATIONS_t, TAG_APPLICATION_ID_t, TAG_APPLICATION_DATA_t, TAG_CREATION_DATETIME_t,
    TAG_ROLLBACK_RESISTANT_t, TAG_ROOT_OF_TRUST_t, TAG_ASSOCIATED_DATA_t, TAG_NONCE_t,
    TAG_AUTH_TOKEN_t, TAG_BOOTLOADER_ONLY_t, TAG_OS_VERSION_t, TAG_OS_PATCHLEVEL_t, TAG_UNIQUE_ID_t,
    TAG_ATTESTATION_CHALLENGE_t, TAG_ATTESTATION_APPLICATION_ID_t, TAG_RESET_SINCE_ID_ROTATION_t,
    TAG_PURPOSE_t, TAG_ALGORITHM_t, TAG_BLOCK_MODE_t, TAG_DIGEST_t, TAG_PADDING_t,
    TAG_BLOB_USAGE_REQUIREMENTS_t, TAG_ORIGIN_t, TAG_USER_AUTH_TYPE_t, TAG_KDF_t, TAG_EC_CURVE_t>;

/* implementation in keystore_utils.cpp */
extern const char* stringifyTag(Tag tag);

template <typename TypedTagType>
struct TypedTag2ValueType;

#define MAKE_TAG_VALUE_ACCESSOR(tag_type, field_name)                              \
    template <Tag tag>                                                             \
    struct TypedTag2ValueType<TypedTag<tag_type, tag>> {                           \
        typedef decltype(static_cast<KeyParameter*>(nullptr)->field_name) type;    \
    };                                                                             \
    template <Tag tag>                                                             \
    inline auto accessTagValue(TypedTag<tag_type, tag>, const KeyParameter& param) \
        ->const decltype(param.field_name)& {                                      \
        return param.field_name;                                                   \
    }                                                                              \
    template <Tag tag>                                                             \
    inline auto accessTagValue(TypedTag<tag_type, tag>, KeyParameter& param)       \
        ->decltype(param.field_name)& {                                            \
        return param.field_name;                                                   \
    }

MAKE_TAG_VALUE_ACCESSOR(TagType::ULONG, f.longInteger)
MAKE_TAG_VALUE_ACCESSOR(TagType::ULONG_REP, f.longInteger)
MAKE_TAG_VALUE_ACCESSOR(TagType::DATE, f.dateTime)
MAKE_TAG_VALUE_ACCESSOR(TagType::UINT, f.integer)
MAKE_TAG_VALUE_ACCESSOR(TagType::UINT_REP, f.integer)
MAKE_TAG_VALUE_ACCESSOR(TagType::BOOL, f.boolValue)
MAKE_TAG_VALUE_ACCESSOR(TagType::BYTES, blob)
MAKE_TAG_VALUE_ACCESSOR(TagType::BIGNUM, blob)

#define MAKE_TAG_ENUM_VALUE_ACCESSOR(typed_tag, field_name)                     \
    template <>                                                                 \
    struct TypedTag2ValueType<decltype(typed_tag)> {                            \
        typedef decltype(static_cast<KeyParameter*>(nullptr)->field_name) type; \
    };                                                                          \
    inline auto accessTagValue(decltype(typed_tag), const KeyParameter& param)  \
        ->const decltype(param.field_name)& {                                   \
        return param.field_name;                                                \
    }                                                                           \
    inline auto accessTagValue(decltype(typed_tag), KeyParameter& param)        \
        ->decltype(param.field_name)& {                                         \
        return param.field_name;                                                \
    }

MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_ALGORITHM, f.algorithm)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_BLOB_USAGE_REQUIREMENTS, f.keyBlobUsageRequirements)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_BLOCK_MODE, f.blockMode)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_DIGEST, f.digest)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_EC_CURVE, f.ecCurve)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_KDF, f.keyDerivationFunction)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_ORIGIN, f.origin)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_PADDING, f.paddingMode)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_PURPOSE, f.purpose)
MAKE_TAG_ENUM_VALUE_ACCESSOR(TAG_USER_AUTH_TYPE, f.hardwareAuthenticatorType)

template <TagType tag_type, Tag tag, typename ValueT>
inline KeyParameter makeKeyParameter(TypedTag<tag_type, tag> ttag, ValueT&& value) {
    KeyParameter param;
    param.tag = tag;
    param.f.longInteger = 0;
    accessTagValue(ttag, param) = std::forward<ValueT>(value);
    return param;
}

// the boolean case
template <Tag tag>
inline KeyParameter makeKeyParameter(TypedTag<TagType::BOOL, tag>) {
    KeyParameter param;
    param.tag = tag;
    param.f.boolValue = true;
    return param;
}

template <typename... Pack>
struct FirstOrNoneHelper;
template <typename First>
struct FirstOrNoneHelper<First> {
    typedef First type;
};
template <>
struct FirstOrNoneHelper<> {
    struct type {};
};

template <typename... Pack>
using FirstOrNone = typename FirstOrNoneHelper<Pack...>::type;

template <TagType tag_type, Tag tag, typename... Args>
inline KeyParameter Authorization(TypedTag<tag_type, tag> ttag, Args&&... args) {
    static_assert(tag_type != TagType::BOOL || (sizeof...(args) == 0),
                  "TagType::BOOL Authorizations do not take parameters. Presence is truth.");
    static_assert(tag_type == TagType::BOOL || (sizeof...(args) == 1),
                  "Authorization other then TagType::BOOL take exactly one parameter.");
    static_assert(
        tag_type == TagType::BOOL ||
            std::is_convertible<std::remove_cv_t<std::remove_reference_t<FirstOrNone<Args...>>>,
                                typename TypedTag2ValueType<TypedTag<tag_type, tag>>::type>::value,
        "Invalid argument type for given tag.");

    return makeKeyParameter(ttag, std::forward<Args>(args)...);
}

/**
 * This class wraps a (mostly return) value and stores whether or not the wrapped value is valid out
 * of band. Note that if the wrapped value is a reference it is unsafe to access the value if
 * !isOk(). If the wrapped type is a pointer or value and !isOk(), it is still safe to access the
 * wrapped value. In this case the pointer will be NULL though, and the value will be default
 * constructed.
 */
template <typename ValueT>
class NullOr {
    template <typename T>
    struct reference_initializer {
        static T&& init() { return *static_cast<std::remove_reference_t<T>*>(nullptr); }
    };
    template <typename T>
    struct pointer_initializer {
        static T init() { return nullptr; }
    };
    template <typename T>
    struct value_initializer {
        static T init() { return T(); }
    };
    template <typename T>
    using initializer_t = std::conditional_t<
        std::is_lvalue_reference<T>::value, reference_initializer<T>,
        std::conditional_t<std::is_pointer<T>::value, pointer_initializer<T>, value_initializer<T>>>;

  public:
    NullOr() : value_(initializer_t<ValueT>::init()), null_(true) {}
    NullOr(ValueT&& value) : value_(std::forward<ValueT>(value)), null_(false) {}

    bool isOk() const { return !null_; }

    const ValueT& value() const & { return value_; }
    ValueT& value() & { return value_; }
    ValueT&& value() && { return std::move(value_); }

  private:
    ValueT value_;
    bool null_;
};

template <typename T>
std::remove_reference_t<T> NullOrOr(T&& v) {
    if (v.isOk()) return v;
    return {};
}

template <typename Head, typename... Tail>
std::remove_reference_t<Head> NullOrOr(Head&& head, Tail&&... tail) {
    if (head.isOk()) return head;
    return NullOrOr(std::forward<Tail>(tail)...);
}

template <typename Default, typename Wrapped>
std::remove_reference_t<Wrapped> defaultOr(NullOr<Wrapped>&& optional, Default&& def) {
    static_assert(
        std::is_convertible<std::remove_reference_t<Default>, std::remove_reference_t<Wrapped>>::value,
        "Type of default value must match the type wrapped by NullOr");
    if (optional.isOk()) return optional.value();
    return def;
}

template <TagType tag_type, Tag tag>
inline NullOr<const typename TypedTag2ValueType<TypedTag<tag_type, tag>>::type&> authorizationValue(
    TypedTag<tag_type, tag> ttag, const KeyParameter& param) {
    if (tag != param.tag) return {};
    return accessTagValue(ttag, param);
}

}  // namespace keystore

#endif  // SYSTEM_SECURITY_KEYSTORE_KEYMASTER_TAGS_H_