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 * For debugging purposes, one additional element of TypedTag and TypedEnumTag can be conditionally 53 * compiled in. If the "KEYMASTER_NAME_TAGS" macro symbol is defined, both classes will have a 54 * name() method which returns a string equal to the tame of the tag (e.g. TAG_PURPOSE). Activating 55 * this option means the classes _do_ contain a data member, a pointer to the string, and also 56 * causes static data space to be allocated for the strings. So the run-time cost of these classes 57 * is no longer zero. Note that it can cause problems if KEYMASTER_NAME_TAGS is defined for some 58 * compilation units and not others. 59 */ 60 61 #include <hardware/hw_auth_token.h> 62 #include <hardware/keymaster_defs.h> 63 64 namespace keymaster { 65 66 // The following create the numeric values that KM_TAG_PADDING and KM_TAG_DIGEST used to have. We 67 // need these old values to be able to support old keys that use them. 68 static const keymaster_tag_t KM_TAG_DIGEST_OLD = static_cast<keymaster_tag_t>(KM_ENUM | 5); 69 static const keymaster_tag_t KM_TAG_PADDING_OLD = static_cast<keymaster_tag_t>(KM_ENUM | 7); 70 71 // Until we have C++11, fake std::static_assert. 72 template <bool b> struct StaticAssert {}; 73 template <> struct StaticAssert<true> { 74 static void check() {} 75 }; 76 77 // An unusable type that we can associate with tag types that don't have a simple value type. 78 // That will prevent the associated type from being used inadvertently. 79 class Void { 80 Void(); 81 ~Void(); 82 }; 83 84 /** 85 * A template that defines the association between non-enumerated tag types and their value 86 * types. For each tag type we define a specialized struct that contains a typedef "value_type". 87 */ 88 template <keymaster_tag_type_t tag_type> struct TagValueType {}; 89 template <> struct TagValueType<KM_ULONG> { typedef uint64_t value_type; }; 90 template <> struct TagValueType<KM_ULONG_REP> { typedef uint64_t value_type; }; 91 template <> struct TagValueType<KM_DATE> { typedef uint64_t value_type; }; 92 template <> struct TagValueType<KM_UINT> { typedef uint32_t value_type; }; 93 template <> struct TagValueType<KM_UINT_REP> { typedef uint32_t value_type; }; 94 template <> struct TagValueType<KM_INVALID> { typedef Void value_type; }; 95 template <> struct TagValueType<KM_BOOL> { typedef bool value_type; }; 96 template <> struct TagValueType<KM_BYTES> { typedef keymaster_blob_t value_type; }; 97 template <> struct TagValueType<KM_BIGNUM> { typedef keymaster_blob_t value_type; }; 98 99 /** 100 * TypedTag is a templatized version of keymaster_tag_t, which provides compile-time checking of 101 * keymaster tag types. Instances are convertible to keymaster_tag_t, so they can be used wherever 102 * keymaster_tag_t is expected, and because they encode the tag type it's possible to create 103 * function overloadings that only operate on tags with a particular type. 104 */ 105 template <keymaster_tag_type_t tag_type, keymaster_tag_t tag> class TypedTag { 106 public: 107 typedef typename TagValueType<tag_type>::value_type value_type; 108 109 #ifdef KEYMASTER_NAME_TAGS 110 inline TypedTag(const char* name) : name_(name) { 111 #else 112 inline TypedTag() { 113 #endif 114 // Ensure that it's impossible to create a TypedTag instance whose 'tag' doesn't have type 115 // 'tag_type'. Attempting to instantiate a tag with the wrong type will result in a compile 116 // error (no match for template specialization StaticAssert<false>), with no run-time cost. 117 StaticAssert<(tag & tag_type) == tag_type>::check(); 118 StaticAssert<(tag_type != KM_ENUM) && (tag_type != KM_ENUM_REP)>::check(); 119 } 120 inline operator keymaster_tag_t() { return tag; } 121 #ifdef KEYMASTER_NAME_TAGS 122 const char* name() { return name_; } 123 124 private: 125 const char* name_; 126 #endif 127 }; 128 129 template <keymaster_tag_type_t tag_type, keymaster_tag_t tag, typename KeymasterEnum> 130 class TypedEnumTag { 131 public: 132 typedef KeymasterEnum value_type; 133 134 #ifdef KEYMASTER_NAME_TAGS 135 inline TypedEnumTag(const char* name) : name_(name) { 136 #else 137 inline TypedEnumTag() { 138 #endif 139 // Ensure that it's impossible to create a TypedTag instance whose 'tag' doesn't have type 140 // 'tag_type'. Attempting to instantiate a tag with the wrong type will result in a compile 141 // error (no match for template specialization StaticAssert<false>), with no run-time cost. 142 StaticAssert<(tag & tag_type) == tag_type>::check(); 143 StaticAssert<(tag_type == KM_ENUM) || (tag_type == KM_ENUM_REP)>::check(); 144 } 145 inline operator keymaster_tag_t() { return tag; } 146 #ifdef KEYMASTER_NAME_TAGS 147 const char* name() { return name_; } 148 149 private: 150 const char* name_; 151 #endif 152 }; 153 154 // DEFINE_KEYMASTER_TAG is used to create TypedTag instances for each non-enum keymaster tag. 155 #ifdef KEYMASTER_NAME_TAGS 156 #define DEFINE_KEYMASTER_TAG(type, name) static TypedTag<type, KM_##name> name(#name) 157 #else 158 #define DEFINE_KEYMASTER_TAG(type, name) static TypedTag<type, KM_##name> name 159 #endif 160 161 DEFINE_KEYMASTER_TAG(KM_INVALID, TAG_INVALID); 162 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_KEY_SIZE); 163 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_MAC_LENGTH); 164 DEFINE_KEYMASTER_TAG(KM_BOOL, TAG_CALLER_NONCE); 165 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_MIN_MAC_LENGTH); 166 DEFINE_KEYMASTER_TAG(KM_ULONG, TAG_RSA_PUBLIC_EXPONENT); 167 DEFINE_KEYMASTER_TAG(KM_DATE, TAG_ACTIVE_DATETIME); 168 DEFINE_KEYMASTER_TAG(KM_DATE, TAG_ORIGINATION_EXPIRE_DATETIME); 169 DEFINE_KEYMASTER_TAG(KM_DATE, TAG_USAGE_EXPIRE_DATETIME); 170 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_MIN_SECONDS_BETWEEN_OPS); 171 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_MAX_USES_PER_BOOT); 172 DEFINE_KEYMASTER_TAG(KM_BOOL, TAG_ALL_USERS); 173 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_USER_ID); 174 DEFINE_KEYMASTER_TAG(KM_ULONG_REP, TAG_USER_SECURE_ID); 175 DEFINE_KEYMASTER_TAG(KM_BOOL, TAG_NO_AUTH_REQUIRED); 176 DEFINE_KEYMASTER_TAG(KM_UINT, TAG_AUTH_TIMEOUT); 177 DEFINE_KEYMASTER_TAG(KM_BOOL, TAG_ALL_APPLICATIONS); 178 DEFINE_KEYMASTER_TAG(KM_BYTES, TAG_APPLICATION_ID); 179 DEFINE_KEYMASTER_TAG(KM_BYTES, TAG_APPLICATION_DATA); 180 DEFINE_KEYMASTER_TAG(KM_DATE, TAG_CREATION_DATETIME); 181 DEFINE_KEYMASTER_TAG(KM_BOOL, TAG_ROLLBACK_RESISTANT); 182 DEFINE_KEYMASTER_TAG(KM_BYTES, TAG_ROOT_OF_TRUST); 183 DEFINE_KEYMASTER_TAG(KM_BYTES, TAG_ASSOCIATED_DATA); 184 DEFINE_KEYMASTER_TAG(KM_BYTES, TAG_NONCE); 185 DEFINE_KEYMASTER_TAG(KM_BYTES, TAG_AUTH_TOKEN); 186 DEFINE_KEYMASTER_TAG(KM_BOOL, TAG_BOOTLOADER_ONLY); 187 188 #ifdef KEYMASTER_NAME_TAGS 189 #define DEFINE_KEYMASTER_ENUM_TAG(type, name, enumtype) \ 190 static TypedEnumTag<type, KM_##name, enumtype> name(#name) 191 #else 192 #define DEFINE_KEYMASTER_ENUM_TAG(type, name, enumtype) \ 193 static TypedEnumTag<type, KM_##name, enumtype> name 194 #endif 195 196 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_PURPOSE, keymaster_purpose_t); 197 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_ALGORITHM, keymaster_algorithm_t); 198 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_BLOCK_MODE, keymaster_block_mode_t); 199 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_DIGEST, keymaster_digest_t); 200 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_DIGEST_OLD, keymaster_digest_t); 201 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM_REP, TAG_PADDING, keymaster_padding_t); 202 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_PADDING_OLD, keymaster_padding_t); 203 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_BLOB_USAGE_REQUIREMENTS, 204 keymaster_key_blob_usage_requirements_t); 205 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_ORIGIN, keymaster_key_origin_t); 206 DEFINE_KEYMASTER_ENUM_TAG(KM_ENUM, TAG_USER_AUTH_TYPE, hw_authenticator_type_t); 207 208 // 209 // Overloaded function "Authorization" to create keymaster_key_param_t objects for all of tags. 210 // 211 212 template <keymaster_tag_t Tag> 213 inline keymaster_key_param_t Authorization(TypedTag<KM_BOOL, Tag> tag) { 214 return keymaster_param_bool(tag); 215 } 216 217 template <keymaster_tag_t Tag> 218 inline keymaster_key_param_t Authorization(TypedTag<KM_UINT, Tag> tag, uint32_t value) { 219 return keymaster_param_int(tag, value); 220 } 221 222 template <keymaster_tag_t Tag> 223 inline keymaster_key_param_t Authorization(TypedTag<KM_UINT_REP, Tag> tag, uint32_t value) { 224 return keymaster_param_int(tag, value); 225 } 226 227 template <keymaster_tag_t Tag> 228 inline keymaster_key_param_t Authorization(TypedTag<KM_ULONG, Tag> tag, uint64_t value) { 229 return keymaster_param_long(tag, value); 230 } 231 232 template <keymaster_tag_t Tag> 233 inline keymaster_key_param_t Authorization(TypedTag<KM_ULONG_REP, Tag> tag, uint64_t value) { 234 return keymaster_param_long(tag, value); 235 } 236 237 template <keymaster_tag_t Tag> 238 inline keymaster_key_param_t Authorization(TypedTag<KM_DATE, Tag> tag, uint64_t value) { 239 return keymaster_param_date(tag, value); 240 } 241 242 template <keymaster_tag_t Tag> 243 inline keymaster_key_param_t Authorization(TypedTag<KM_BYTES, Tag> tag, const void* bytes, 244 size_t bytes_len) { 245 return keymaster_param_blob(tag, reinterpret_cast<const uint8_t*>(bytes), bytes_len); 246 } 247 248 template <keymaster_tag_t Tag> 249 inline keymaster_key_param_t Authorization(TypedTag<KM_BYTES, Tag> tag, 250 const keymaster_blob_t& blob) { 251 return keymaster_param_blob(tag, blob.data, blob.data_length); 252 } 253 254 template <keymaster_tag_t Tag> 255 inline keymaster_key_param_t Authorization(TypedTag<KM_BIGNUM, Tag> tag, const void* bytes, 256 size_t bytes_len) { 257 return keymaster_param_blob(tag, reinterpret_cast<const uint8_t*>(bytes), bytes_len); 258 } 259 260 template <keymaster_tag_t Tag> 261 inline keymaster_key_param_t Authorization(TypedTag<KM_BIGNUM, Tag> tag, 262 const keymaster_blob_t& blob) { 263 return keymaster_param_blob(tag, blob.data, blob.data_length); 264 } 265 266 template <keymaster_tag_t Tag, typename KeymasterEnum> 267 inline keymaster_key_param_t Authorization(TypedEnumTag<KM_ENUM, Tag, KeymasterEnum> tag, 268 KeymasterEnum value) { 269 return keymaster_param_enum(tag, value); 270 } 271 272 template <keymaster_tag_t Tag, typename KeymasterEnum> 273 inline keymaster_key_param_t Authorization(TypedEnumTag<KM_ENUM_REP, Tag, KeymasterEnum> tag, 274 KeymasterEnum value) { 275 return keymaster_param_enum(tag, value); 276 } 277 278 } // namespace keymaster 279 280 #endif // SYSTEM_KEYMASTER_KEYMASTER_TAGS_H_ 281
