1 /* 2 * Copyright 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SYSTEM_KEYMASTER_KEYMASTER_TAGS_H_ 18 #define SYSTEM_KEYMASTER_KEYMASTER_TAGS_H_ 19 20 /** 21 * This header contains various definitions that make working with keymaster tags safer and easier. 22 * It makes use of a fair amount of template metaprogramming, which is genarally a bad idea for 23 * maintainability, but in this case all of the metaprogramming serves the purpose of making it 24 * impossible to make certain classes of mistakes when operating on keymaster authorizations. For 25 * example, it's an error to create a keymaster_param_t with tag == KM_TAG_PURPOSE and then to 26 * assign KM_ALGORITHM_RSA to the enumerated element of its union, but because "enumerated" is a 27 * uint32_t, there's no way for the compiler, ordinarily, to diagnose it. Also, generic functions 28 * to manipulate authorizations of multiple types can't be written, because they need to know which 29 * union parameter to modify. 30 * 31 * The machinery in this header solves these problems. The core elements are two templated classes, 32 * TypedTag and TypedEnumTag. These classes are templated on a tag type and a tag value, and in the 33 * case of TypedEnumTag, an enumeration type as well. Specializations are created for each 34 * keymaster tag, associating the tag type with the tag, and an instance of each specialization is 35 * created, and named the same as the keymaster tag, but with the KM_ prefix omitted. Because the 36 * classes include a conversion operator to keymaster_tag_t, they can be used anywhere a 37 * keymaster_tag_t is expected. 38 * 39 * They also define a "value_type" typedef, which specifies the type of values associated with that 40 * particular tag. This enables template functions to be written that check that the correct 41 * parameter type is used for a given tag, and that use the correct union entry for the tag type. A 42 * very useful example is the overloaded "Authorization" function defined below, which takes tag and 43 * value arguments and correctly constructs a keyamster_param_t struct. 44 * 45 * Because the classes have no data members and all of their methods are inline, they have ZERO 46 * run-time cost in and of themselves. The one way in which they can create code bloat is when 47 * template functions using them are expanded multiple times. The standard method of creating 48 * trivial, inlined template functions which call non-templated functions which are compact but not 49 * type-safe, allows the program to have both the type-safety of the templates and the compactness 50 * of the non-templated functions, at the same time. 51 */ 52 53 #include <hardware/hw_auth_token.h> 54 #include <hardware/keymaster_defs.h> 55 56 namespace keymaster { 57 58 // The following create the numeric values that KM_TAG_PADDING and KM_TAG_DIGEST used to have. We 59 // need these old values to be able to support old keys that use them. 60 static const keymaster_tag_t KM_TAG_DIGEST_OLD = static_cast<keymaster_tag_t>(KM_ENUM | 5); 61 static const keymaster_tag_t KM_TAG_PADDING_OLD = static_cast<keymaster_tag_t>(KM_ENUM | 7); 62 63 // Until we have C++11, fake std::static_assert. 64 template <bool b> struct StaticAssert {}; 65 template <> struct StaticAssert<true> { 66 static void check() {} 67 }; 68 69 // An unusable type that we can associate with tag types that don't have a simple value type. 70 // That will prevent the associated type from being used inadvertently. 71 class Void { 72 Void(); 73 ~Void(); 74 }; 75 76 /** 77 * A template that defines the association between non-enumerated tag types and their value 78 * types. For each tag type we define a specialized struct that contains a typedef "value_type". 79 */ 80 template <keymaster_tag_type_t tag_type> struct TagValueType {}; 81 template <> struct TagValueType<KM_ULONG> { typedef uint64_t value_type; }; 82 template <> struct TagValueType<KM_ULONG_REP> { typedef uint64_t value_type; }; 83 template <> struct TagValueType<KM_DATE> { typedef uint64_t value_type; }; 84 template <> struct TagValueType<KM_UINT> { typedef uint32_t value_type; }; 85 template <> struct TagValueType<KM_UINT_REP> { typedef uint32_t value_type; }; 86 template <> struct TagValueType<KM_INVALID> { typedef Void value_type; }; 87 template <> struct TagValueType<KM_BOOL> { typedef bool value_type; }; 88 template <> struct TagValueType<KM_BYTES> { typedef keymaster_blob_t value_type; }; 89 template <> struct TagValueType<KM_BIGNUM> { typedef keymaster_blob_t value_type; }; 90 91 /** 92 * TypedTag is a templatized version of keymaster_tag_t, which provides compile-time checking of 93 * keymaster tag types. Instances are convertible to keymaster_tag_t, so they can be used wherever 94 * keymaster_tag_t is expected, and because they encode the tag type it's possible to create 95 * function overloadings that only operate on tags with a particular type. 96 */ 97 template <keymaster_tag_type_t tag_type, keymaster_tag_t tag> class TypedTag { 98 public: 99 typedef typename TagValueType<tag_type>::value_type value_type; 100 101 inline TypedTag() { 102 // Ensure that it's impossible to create a TypedTag instance whose 'tag' doesn't have type 103 // 'tag_type'. Attempting to instantiate a tag with the wrong type will result in a compile 104 // error (no match for template specialization StaticAssert<false>), with no run-time cost. 105 StaticAssert<(tag & tag_type) == tag_type>::check(); 106 StaticAssert<(tag_type != KM_ENUM) && (tag_type != KM_ENUM_REP)>::check(); 107 } 108 inline operator keymaster_tag_t() { return tag; } 109 inline long masked_tag() { return static_cast<long>(keymaster_tag_mask_type(tag)); } 110 }; 111 112 template <keymaster_tag_type_t tag_type, keymaster_tag_t tag, typename KeymasterEnum> 113 class TypedEnumTag { 114 public: 115 typedef KeymasterEnum value_type; 116 117 inline TypedEnumTag() { 118 // Ensure that it's impossible to create a TypedTag instance whose 'tag' doesn't have type 119 // 'tag_type'. Attempting to instantiate a tag with the wrong type will result in a compile 120 // error (no match for template specialization StaticAssert<false>), with no run-time cost. 121 StaticAssert<(tag & tag_type) == tag_type>::check(); 122 StaticAssert<(tag_type == KM_ENUM) || (tag_type == KM_ENUM_REP)>::check(); 123 } 124 inline operator keymaster_tag_t() { return tag; } 125 inline long masked_tag() { return static_cast<long>(keymaster_tag_mask_type(tag)); } 126 }; 127 128 #ifdef KEYMASTER_NAME_TAGS 129 const char* StringifyTag(keymaster_tag_t tag); 130 #endif 131 132 // DECLARE_KEYMASTER_TAG is used to declare TypedTag instances for each non-enum keymaster tag. 133 #define DECLARE_KEYMASTER_TAG(type, name) extern TypedTag<type, KM_##name> name 134 135 DECLARE_KEYMASTER_TAG(KM_INVALID, TAG_INVALID); 136 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_KEY_SIZE); 137 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_MAC_LENGTH); 138 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_CALLER_NONCE); 139 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_MIN_MAC_LENGTH); 140 DECLARE_KEYMASTER_TAG(KM_ULONG, TAG_RSA_PUBLIC_EXPONENT); 141 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_ECIES_SINGLE_HASH_MODE); 142 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_INCLUDE_UNIQUE_ID); 143 DECLARE_KEYMASTER_TAG(KM_DATE, TAG_ACTIVE_DATETIME); 144 DECLARE_KEYMASTER_TAG(KM_DATE, TAG_ORIGINATION_EXPIRE_DATETIME); 145 DECLARE_KEYMASTER_TAG(KM_DATE, TAG_USAGE_EXPIRE_DATETIME); 146 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_MIN_SECONDS_BETWEEN_OPS); 147 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_MAX_USES_PER_BOOT); 148 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_ALL_USERS); 149 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_USER_ID); 150 DECLARE_KEYMASTER_TAG(KM_ULONG_REP, TAG_USER_SECURE_ID); 151 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_NO_AUTH_REQUIRED); 152 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_AUTH_TIMEOUT); 153 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_ALLOW_WHILE_ON_BODY); 154 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_ALL_APPLICATIONS); 155 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_APPLICATION_ID); 156 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_APPLICATION_DATA); 157 DECLARE_KEYMASTER_TAG(KM_DATE, TAG_CREATION_DATETIME); 158 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_ROLLBACK_RESISTANT); 159 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_ROOT_OF_TRUST); 160 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_ASSOCIATED_DATA); 161 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_NONCE); 162 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_AUTH_TOKEN); 163 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_BOOTLOADER_ONLY); 164 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_OS_VERSION); 165 DECLARE_KEYMASTER_TAG(KM_UINT, TAG_OS_PATCHLEVEL); 166 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_UNIQUE_ID); 167 DECLARE_KEYMASTER_TAG(KM_BYTES, TAG_ATTESTATION_CHALLENGE); 168 DECLARE_KEYMASTER_TAG(KM_BOOL, TAG_RESET_SINCE_ID_ROTATION); 169 170 // DECLARE_KEYMASTER_ENUM_TAG is used to declare TypedEnumTag instances for each enum keymaster tag. 171 #define DECLARE_KEYMASTER_ENUM_TAG(type, name, enumtype) \ 172 extern TypedEnumTag<type, KM_##name, enumtype> name 173 174 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_PURPOSE, keymaster_purpose_t); 175 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_ALGORITHM, keymaster_algorithm_t); 176 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_BLOCK_MODE, keymaster_block_mode_t); 177 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_DIGEST, keymaster_digest_t); 178 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_DIGEST_OLD, keymaster_digest_t); 179 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_PADDING, keymaster_padding_t); 180 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_PADDING_OLD, keymaster_padding_t); 181 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_BLOB_USAGE_REQUIREMENTS, 182 keymaster_key_blob_usage_requirements_t); 183 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_ORIGIN, keymaster_key_origin_t); 184 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_USER_AUTH_TYPE, hw_authenticator_type_t); 185 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_KDF, keymaster_kdf_t); 186 DECLARE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_EC_CURVE, keymaster_ec_curve_t); 187 188 // 189 // Overloaded function "Authorization" to create keymaster_key_param_t objects for all of tags. 190 // 191 192 template <keymaster_tag_t Tag> 193 inline keymaster_key_param_t Authorization(TypedTag<KM_BOOL, Tag> tag) { 194 return keymaster_param_bool(tag); 195 } 196 197 template <keymaster_tag_t Tag> 198 inline keymaster_key_param_t Authorization(TypedTag<KM_UINT, Tag> tag, uint32_t value) { 199 return keymaster_param_int(tag, value); 200 } 201 202 template <keymaster_tag_t Tag> 203 inline keymaster_key_param_t Authorization(TypedTag<KM_UINT_REP, Tag> tag, uint32_t value) { 204 return keymaster_param_int(tag, value); 205 } 206 207 template <keymaster_tag_t Tag> 208 inline keymaster_key_param_t Authorization(TypedTag<KM_ULONG, Tag> tag, uint64_t value) { 209 return keymaster_param_long(tag, value); 210 } 211 212 template <keymaster_tag_t Tag> 213 inline keymaster_key_param_t Authorization(TypedTag<KM_ULONG_REP, Tag> tag, uint64_t value) { 214 return keymaster_param_long(tag, value); 215 } 216 217 template <keymaster_tag_t Tag> 218 inline keymaster_key_param_t Authorization(TypedTag<KM_DATE, Tag> tag, uint64_t value) { 219 return keymaster_param_date(tag, value); 220 } 221 222 template <keymaster_tag_t Tag> 223 inline keymaster_key_param_t Authorization(TypedTag<KM_BYTES, Tag> tag, const void* bytes, 224 size_t bytes_len) { 225 return keymaster_param_blob(tag, reinterpret_cast<const uint8_t*>(bytes), bytes_len); 226 } 227 228 template <keymaster_tag_t Tag> 229 inline keymaster_key_param_t Authorization(TypedTag<KM_BYTES, Tag> tag, 230 const keymaster_blob_t& blob) { 231 return keymaster_param_blob(tag, blob.data, blob.data_length); 232 } 233 234 template <keymaster_tag_t Tag> 235 inline keymaster_key_param_t Authorization(TypedTag<KM_BIGNUM, Tag> tag, const void* bytes, 236 size_t bytes_len) { 237 return keymaster_param_blob(tag, reinterpret_cast<const uint8_t*>(bytes), bytes_len); 238 } 239 240 template <keymaster_tag_t Tag> 241 inline keymaster_key_param_t Authorization(TypedTag<KM_BIGNUM, Tag> tag, 242 const keymaster_blob_t& blob) { 243 return keymaster_param_blob(tag, blob.data, blob.data_length); 244 } 245 246 template <keymaster_tag_t Tag, typename KeymasterEnum> 247 inline keymaster_key_param_t Authorization(TypedEnumTag<KM_ENUM, Tag, KeymasterEnum> tag, 248 KeymasterEnum value) { 249 return keymaster_param_enum(tag, value); 250 } 251 252 template <keymaster_tag_t Tag, typename KeymasterEnum> 253 inline keymaster_key_param_t Authorization(TypedEnumTag<KM_ENUM_REP, Tag, KeymasterEnum> tag, 254 KeymasterEnum value) { 255 return keymaster_param_enum(tag, value); 256 } 257 258 } // namespace keymaster 259 260 #endif // SYSTEM_KEYMASTER_KEYMASTER_TAGS_H_ 261
