1 /*===---- ptrauth.h - Pointer authentication -------------------------------=== 2 * 3 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 * See https://llvm.org/LICENSE.txt for license information. 5 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 * 7 *===-----------------------------------------------------------------------=== 8 */ 9 10 #ifndef __PTRAUTH_H 11 #define __PTRAUTH_H 12 13 typedef enum { 14 ptrauth_key_asia = 0, 15 ptrauth_key_asib = 1, 16 ptrauth_key_asda = 2, 17 ptrauth_key_asdb = 3, 18 19 /* A process-independent key which can be used to sign code pointers. */ 20 ptrauth_key_process_independent_code = ptrauth_key_asia, 21 22 /* A process-specific key which can be used to sign code pointers. */ 23 ptrauth_key_process_dependent_code = ptrauth_key_asib, 24 25 /* A process-independent key which can be used to sign data pointers. */ 26 ptrauth_key_process_independent_data = ptrauth_key_asda, 27 28 /* A process-specific key which can be used to sign data pointers. */ 29 ptrauth_key_process_dependent_data = ptrauth_key_asdb, 30 31 /* The key used to sign return addresses on the stack. 32 The extra data is based on the storage address of the return address. 33 On AArch64, that is always the storage address of the return address + 8 34 (or, in other words, the value of the stack pointer on function entry) */ 35 ptrauth_key_return_address = ptrauth_key_process_dependent_code, 36 37 /* The key used to sign C function pointers. 38 The extra data is always 0. */ 39 ptrauth_key_function_pointer = ptrauth_key_process_independent_code, 40 41 /* The key used to sign C++ v-table pointers. 42 The extra data is always 0. */ 43 ptrauth_key_cxx_vtable_pointer = ptrauth_key_process_independent_data, 44 45 /* The key used to sign metadata pointers to Objective-C method-lists. */ 46 ptrauth_key_method_list_pointer = ptrauth_key_asda, 47 48 /* The key used to sign Objective-C isa and super pointers. */ 49 ptrauth_key_objc_isa_pointer = ptrauth_key_process_independent_data, 50 ptrauth_key_objc_super_pointer = ptrauth_key_process_independent_data, 51 52 /* The key used to sign selector pointers */ 53 ptrauth_key_objc_sel_pointer = ptrauth_key_process_dependent_data, 54 55 /* The key used to sign Objective-C class_ro_t pointers. */ 56 ptrauth_key_objc_class_ro_pointer = ptrauth_key_process_independent_data, 57 58 /* The key used to sign pointers in ELF .init_array/.fini_array. */ 59 ptrauth_key_init_fini_pointer = ptrauth_key_process_independent_code, 60 61 /* Other pointers signed under the ABI use private ABI rules. */ 62 63 } ptrauth_key; 64 65 /* An integer type of the appropriate size for a discriminator argument. */ 66 typedef __UINTPTR_TYPE__ ptrauth_extra_data_t; 67 68 /* An integer type of the appropriate size for a generic signature. */ 69 typedef __UINTPTR_TYPE__ ptrauth_generic_signature_t; 70 71 /* A signed pointer value embeds the original pointer together with 72 a signature that attests to the validity of that pointer. Because 73 this signature must use only "spare" bits of the pointer, a 74 signature's validity is probabilistic in practice: it is unlikely 75 but still plausible that an invalidly-derived signature will 76 somehow equal the correct signature and therefore successfully 77 authenticate. Nonetheless, this scheme provides a strong degree 78 of protection against certain kinds of attacks. */ 79 80 /* Authenticating a pointer that was not signed with the given key 81 and extra-data value will (likely) fail by trapping. */ 82 83 /* The null function pointer is always the all-zero bit pattern. 84 Signing an all-zero bit pattern will embed a (likely) non-zero 85 signature in the result, and so the result will not seem to be 86 a null function pointer. Authenticating this value will yield 87 a null function pointer back. However, authenticating an 88 all-zero bit pattern will probably fail, because the 89 authentication will expect a (likely) non-zero signature to 90 embedded in the value. 91 92 Because of this, if a pointer may validly be null, you should 93 check for null before attempting to authenticate it with one 94 of these intrinsics. This is not necessary when using the 95 __ptrauth qualifier; the compiler will perform this check 96 automatically. */ 97 98 #if __has_feature(ptrauth_intrinsics) || defined(__PTRAUTH__) 99 100 /* Strip the signature from a value without authenticating it. 101 102 If the value is a function pointer, the result will not be a 103 legal function pointer because of the missing signature, and 104 attempting to call it will result in an authentication failure. 105 106 The value must be an expression of pointer type. 107 The key must be a constant expression of type ptrauth_key. 108 The result will have the same type as the original value. */ 109 #define ptrauth_strip(__value, __key) __builtin_ptrauth_strip(__value, __key) 110 111 /* Blend a constant discriminator into the given pointer-like value 112 to form a new discriminator. Not all bits of the inputs are 113 guaranteed to contribute to the result. 114 115 On arm64e, the integer must fall within the range of a uint16_t; 116 other bits may be ignored. 117 118 For the purposes of ptrauth_sign_constant, the result of calling 119 this function is considered a constant expression if the arguments 120 are constant. Some restrictions may be imposed on the pointer. 121 122 The first argument must be an expression of pointer type. 123 The second argument must be an expression of integer type. 124 The result will have type uintptr_t. */ 125 #define ptrauth_blend_discriminator(__pointer, __integer) \ 126 __builtin_ptrauth_blend_discriminator(__pointer, __integer) 127 128 /* Return a signed pointer for a constant address in a manner which guarantees 129 a non-attackable sequence. 130 131 The value must be a constant expression of pointer type which evaluates to 132 a non-null pointer. 133 The key must be a constant expression of type ptrauth_key. 134 The extra data must be a constant expression of pointer or integer type; 135 if an integer, it will be coerced to ptrauth_extra_data_t. 136 The result will have the same type as the original value. 137 138 This can be used in constant expressions. */ 139 #define ptrauth_sign_constant(__value, __key, __data) \ 140 __builtin_ptrauth_sign_constant(__value, __key, __data) 141 142 /* Add a signature to the given pointer value using a specific key, 143 using the given extra data as a salt to the signing process. 144 145 This operation does not authenticate the original value and is 146 therefore potentially insecure if an attacker could possibly 147 control that value. 148 149 The value must be an expression of pointer type. 150 The key must be a constant expression of type ptrauth_key. 151 The extra data must be an expression of pointer or integer type; 152 if an integer, it will be coerced to ptrauth_extra_data_t. 153 The result will have the same type as the original value. */ 154 #define ptrauth_sign_unauthenticated(__value, __key, __data) \ 155 __builtin_ptrauth_sign_unauthenticated(__value, __key, __data) 156 157 /* Authenticate a pointer using one scheme and resign it using another. 158 159 If the result is subsequently authenticated using the new scheme, that 160 authentication is guaranteed to fail if and only if the initial 161 authentication failed. 162 163 The value must be an expression of pointer type. 164 The key must be a constant expression of type ptrauth_key. 165 The extra data must be an expression of pointer or integer type; 166 if an integer, it will be coerced to ptrauth_extra_data_t. 167 The result will have the same type as the original value. 168 169 This operation is guaranteed to not leave the intermediate value 170 available for attack before it is re-signed. 171 172 Do not pass a null pointer to this function. A null pointer 173 will not successfully authenticate. 174 175 This operation traps if the authentication fails. */ 176 #define ptrauth_auth_and_resign(__value, __old_key, __old_data, __new_key, \ 177 __new_data) \ 178 __builtin_ptrauth_auth_and_resign(__value, __old_key, __old_data, __new_key, \ 179 __new_data) 180 181 /* Authenticate a pointer using one scheme and resign it as a C 182 function pointer. 183 184 If the result is subsequently authenticated using the new scheme, that 185 authentication is guaranteed to fail if and only if the initial 186 authentication failed. 187 188 The value must be an expression of function pointer type. 189 The key must be a constant expression of type ptrauth_key. 190 The extra data must be an expression of pointer or integer type; 191 if an integer, it will be coerced to ptrauth_extra_data_t. 192 The result will have the same type as the original value. 193 194 This operation is guaranteed to not leave the intermediate value 195 available for attack before it is re-signed. Additionally, if this 196 expression is used syntactically as the function expression in a 197 call, only a single authentication will be performed. */ 198 #define ptrauth_auth_function(__value, __old_key, __old_data) \ 199 ptrauth_auth_and_resign(__value, __old_key, __old_data, \ 200 ptrauth_key_function_pointer, 0) 201 202 /* Authenticate a data pointer. 203 204 The value must be an expression of non-function pointer type. 205 The key must be a constant expression of type ptrauth_key. 206 The extra data must be an expression of pointer or integer type; 207 if an integer, it will be coerced to ptrauth_extra_data_t. 208 The result will have the same type as the original value. 209 210 This operation traps if the authentication fails. */ 211 #define ptrauth_auth_data(__value, __old_key, __old_data) \ 212 __builtin_ptrauth_auth(__value, __old_key, __old_data) 213 214 /* Compute a constant discriminator from the given string. 215 216 The argument must be a string literal of char character type. The result 217 has type ptrauth_extra_data_t. 218 219 The result value is never zero and always within range for both the 220 __ptrauth qualifier and ptrauth_blend_discriminator. 221 222 This can be used in constant expressions. 223 */ 224 #define ptrauth_string_discriminator(__string) \ 225 __builtin_ptrauth_string_discriminator(__string) 226 227 /* Compute a constant discriminator from the given type. 228 229 The result can be used as the second argument to 230 ptrauth_blend_discriminator or the third argument to the 231 __ptrauth qualifier. It has type size_t. 232 233 If the type is a C++ member function pointer type, the result is 234 the discriminator used to signed member function pointers of that 235 type. If the type is a function, function pointer, or function 236 reference type, the result is the discriminator used to sign 237 functions of that type. It is ill-formed to use this macro with any 238 other type. 239 240 A call to this function is an integer constant expression. */ 241 #define ptrauth_type_discriminator(__type) \ 242 __builtin_ptrauth_type_discriminator(__type) 243 244 /* Compute a signature for the given pair of pointer-sized values. 245 The order of the arguments is significant. 246 247 Like a pointer signature, the resulting signature depends on 248 private key data and therefore should not be reliably reproducible 249 by attackers. That means that this can be used to validate the 250 integrity of arbitrary data by storing a signature for that data 251 alongside it, then checking that the signature is still valid later. 252 Data which exceeds two pointers in size can be signed by either 253 computing a tree of generic signatures or just signing an ordinary 254 cryptographic hash of the data. 255 256 The result has type ptrauth_generic_signature_t. However, it may 257 not have as many bits of entropy as that type's width would suggest; 258 some implementations are known to compute a compressed signature as 259 if the arguments were a pointer and a discriminator. 260 261 The arguments must be either pointers or integers; if integers, they 262 will be coerce to uintptr_t. */ 263 #define ptrauth_sign_generic_data(__value, __data) \ 264 __builtin_ptrauth_sign_generic_data(__value, __data) 265 266 /* C++ vtable pointer signing class attribute */ 267 #define ptrauth_cxx_vtable_pointer(key, address_discrimination, \ 268 extra_discrimination...) \ 269 [[clang::ptrauth_vtable_pointer(key, address_discrimination, \ 270 extra_discrimination)]] 271 272 /* The value is ptrauth_string_discriminator("init_fini") */ 273 #define __ptrauth_init_fini_discriminator 0xd9d4 274 275 /* Objective-C pointer auth ABI qualifiers */ 276 #define __ptrauth_objc_method_list_imp \ 277 __ptrauth(ptrauth_key_function_pointer, 1, 0) 278 279 #if __has_feature(ptrauth_objc_method_list_pointer) 280 #define __ptrauth_objc_method_list_pointer \ 281 __ptrauth(ptrauth_key_method_list_pointer, 1, 0xC310) 282 #else 283 #define __ptrauth_objc_method_list_pointer 284 #endif 285 286 #define __ptrauth_isa_discriminator 0x6AE1 287 #define __ptrauth_super_discriminator 0xB5AB 288 #define __ptrauth_objc_isa_pointer \ 289 __ptrauth(ptrauth_key_objc_isa_pointer, 1, __ptrauth_isa_discriminator) 290 #if __has_feature(ptrauth_restricted_intptr_qualifier) 291 #define __ptrauth_objc_isa_uintptr \ 292 __ptrauth_restricted_intptr(ptrauth_key_objc_isa_pointer, 1, \ 293 __ptrauth_isa_discriminator) 294 #else 295 #define __ptrauth_objc_isa_uintptr \ 296 __ptrauth(ptrauth_key_objc_isa_pointer, 1, __ptrauth_isa_discriminator) 297 #endif 298 299 #define __ptrauth_objc_super_pointer \ 300 __ptrauth(ptrauth_key_objc_super_pointer, 1, __ptrauth_super_discriminator) 301 302 #define __ptrauth_objc_sel_discriminator 0x57c2 303 #if __has_feature(ptrauth_objc_interface_sel) 304 #define __ptrauth_objc_sel \ 305 __ptrauth(ptrauth_key_objc_sel_pointer, 1, __ptrauth_objc_sel_discriminator) 306 #else 307 #define __ptrauth_objc_sel 308 #endif 309 310 #define __ptrauth_objc_class_ro_discriminator 0x61f8 311 #define __ptrauth_objc_class_ro \ 312 __ptrauth(ptrauth_key_objc_class_ro_pointer, 1, \ 313 __ptrauth_objc_class_ro_discriminator) 314 315 #else 316 317 #define ptrauth_strip(__value, __key) \ 318 ({ \ 319 (void)__key; \ 320 __value; \ 321 }) 322 323 #define ptrauth_blend_discriminator(__pointer, __integer) \ 324 ({ \ 325 (void)__pointer; \ 326 (void)__integer; \ 327 ((ptrauth_extra_data_t)0); \ 328 }) 329 330 #define ptrauth_sign_constant(__value, __key, __data) \ 331 ({ \ 332 (void)__key; \ 333 (void)__data; \ 334 __value; \ 335 }) 336 337 #define ptrauth_sign_unauthenticated(__value, __key, __data) \ 338 ({ \ 339 (void)__key; \ 340 (void)__data; \ 341 __value; \ 342 }) 343 344 #define ptrauth_auth_and_resign(__value, __old_key, __old_data, __new_key, \ 345 __new_data) \ 346 ({ \ 347 (void)__old_key; \ 348 (void)__old_data; \ 349 (void)__new_key; \ 350 (void)__new_data; \ 351 __value; \ 352 }) 353 354 #define ptrauth_auth_function(__value, __old_key, __old_data) \ 355 ({ \ 356 (void)__old_key; \ 357 (void)__old_data; \ 358 __value; \ 359 }) 360 361 #define ptrauth_auth_data(__value, __old_key, __old_data) \ 362 ({ \ 363 (void)__old_key; \ 364 (void)__old_data; \ 365 __value; \ 366 }) 367 368 #define ptrauth_string_discriminator(__string) \ 369 ({ \ 370 (void)__string; \ 371 ((ptrauth_extra_data_t)0); \ 372 }) 373 374 #define ptrauth_type_discriminator(__type) ((ptrauth_extra_data_t)0) 375 376 #define ptrauth_sign_generic_data(__value, __data) \ 377 ({ \ 378 (void)__value; \ 379 (void)__data; \ 380 ((ptrauth_generic_signature_t)0); \ 381 }) 382 383 384 #define ptrauth_cxx_vtable_pointer(key, address_discrimination, \ 385 extra_discrimination...) 386 387 #define __ptrauth_objc_isa_pointer 388 #define __ptrauth_objc_isa_uintptr 389 #define __ptrauth_objc_super_pointer 390 391 #endif /* __has_feature(ptrauth_intrinsics) || defined(__PTRAUTH__) */ 392 393 #endif /* __PTRAUTH_H */ 394