1========================== 2Trusted and Encrypted Keys 3========================== 4 5Trusted and Encrypted Keys are two new key types added to the existing kernel 6key ring service. Both of these new types are variable length symmetric keys, 7and in both cases all keys are created in the kernel, and user space sees, 8stores, and loads only encrypted blobs. Trusted Keys require the availability 9of a Trust Source for greater security, while Encrypted Keys can be used on any 10system. All user level blobs, are displayed and loaded in hex ASCII for 11convenience, and are integrity verified. 12 13Trusted Keys as Protected key 14============================= 15It is the secure way of keeping the keys in the kernel key-ring as Trusted-Key, 16such that: 17 18- Key-blob, an encrypted key-data, created to be stored, loaded and seen by 19 userspace. 20- Key-data, the plain-key text in the system memory, to be used by 21 kernel space only. 22 23Though key-data is not accessible to the user-space in plain-text, but it is in 24plain-text in system memory, when used in kernel space. Even though kernel-space 25attracts small surface attack, but with compromised kernel or side-channel 26attack accessing the system memory can lead to a chance of the key getting 27compromised/leaked. 28 29In order to protect the key in kernel space, the concept of "protected-keys" is 30introduced which will act as an added layer of protection. The key-data of the 31protected keys is encrypted with Key-Encryption-Key(KEK), and decrypted inside 32the trust source boundary. The plain-key text never available out-side in the 33system memory. Thus, any crypto operation that is to be executed using the 34protected key, can only be done by the trust source, which generated the 35key blob. 36 37Hence, if the protected-key is leaked or compromised, it is of no use to the 38hacker. 39 40Trusted keys as protected keys, with trust source having the capability of 41generating: 42 43- Key-Blob, to be loaded, stored and seen by user-space. 44 45Trust Source 46============ 47 48A trust source provides the source of security for Trusted Keys. This 49section lists currently supported trust sources, along with their security 50considerations. Whether or not a trust source is sufficiently safe depends 51on the strength and correctness of its implementation, as well as the threat 52environment for a specific use case. Since the kernel doesn't know what the 53environment is, and there is no metric of trust, it is dependent on the 54consumer of the Trusted Keys to determine if the trust source is sufficiently 55safe. 56 57 * Root of trust for storage 58 59 (1) TPM (Trusted Platform Module: hardware device) 60 61 Rooted to Storage Root Key (SRK) which never leaves the TPM that 62 provides crypto operation to establish root of trust for storage. 63 64 (2) TEE (Trusted Execution Environment: OP-TEE based on Arm TrustZone) 65 66 Rooted to Hardware Unique Key (HUK) which is generally burnt in on-chip 67 fuses and is accessible to TEE only. 68 69 (3) CAAM (Cryptographic Acceleration and Assurance Module: IP on NXP SoCs) 70 71 When High Assurance Boot (HAB) is enabled and the CAAM is in secure 72 mode, trust is rooted to the OTPMK, a never-disclosed 256-bit key 73 randomly generated and fused into each SoC at manufacturing time. 74 Otherwise, a common fixed test key is used instead. 75 76 (4) DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs) 77 78 Rooted to a one-time programmable key (OTP) that is generally burnt 79 in the on-chip fuses and is accessible to the DCP encryption engine only. 80 DCP provides two keys that can be used as root of trust: the OTP key 81 and the UNIQUE key. Default is to use the UNIQUE key, but selecting 82 the OTP key can be done via a module parameter (dcp_use_otp_key). 83 84 (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore) 85 86 Rooted to a unique, per-LPAR key, which is derived from a system-wide, 87 randomly generated LPAR root key. Both the per-LPAR keys and the LPAR 88 root key are stored in hypervisor-owned secure memory at runtime, 89 and the LPAR root key is additionally persisted in secure locations 90 such as the processor SEEPROMs and encrypted NVRAM. 91 92 * Execution isolation 93 94 (1) TPM 95 96 Fixed set of operations running in isolated execution environment. 97 98 (2) TEE 99 100 Customizable set of operations running in isolated execution 101 environment verified via Secure/Trusted boot process. 102 103 (3) CAAM 104 105 Fixed set of operations running in isolated execution environment. 106 107 (4) DCP 108 109 Fixed set of cryptographic operations running in isolated execution 110 environment. Only basic blob key encryption is executed there. 111 The actual key sealing/unsealing is done on main processor/kernel space. 112 113 (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore) 114 115 Fixed set of cryptographic operations done on on-chip hardware 116 cryptographic acceleration unit NX. Keys for wrapping and unwrapping 117 are managed by PowerVM Platform KeyStore, which stores keys in an 118 isolated in-memory copy in secure hypervisor memory, as well as in a 119 persistent copy in hypervisor-encrypted NVRAM. 120 121 * Optional binding to platform integrity state 122 123 (1) TPM 124 125 Keys can be optionally sealed to specified PCR (integrity measurement) 126 values, and only unsealed by the TPM, if PCRs and blob integrity 127 verifications match. A loaded Trusted Key can be updated with new 128 (future) PCR values, so keys are easily migrated to new PCR values, 129 such as when the kernel and initramfs are updated. The same key can 130 have many saved blobs under different PCR values, so multiple boots are 131 easily supported. 132 133 (2) TEE 134 135 Relies on Secure/Trusted boot process for platform integrity. It can 136 be extended with TEE based measured boot process. 137 138 (3) CAAM 139 140 Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs 141 for platform integrity. 142 143 (4) DCP 144 145 Relies on Secure/Trusted boot process (called HAB by vendor) for 146 platform integrity. 147 148 (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore) 149 150 Relies on secure and trusted boot process of IBM Power systems for 151 platform integrity. 152 153 * Interfaces and APIs 154 155 (1) TPM 156 157 TPMs have well-documented, standardized interfaces and APIs. 158 159 (2) TEE 160 161 TEEs have well-documented, standardized client interface and APIs. For 162 more details refer to ``Documentation/driver-api/tee.rst``. 163 164 (3) CAAM 165 166 Interface is specific to silicon vendor. 167 168 (4) DCP 169 170 Vendor-specific API that is implemented as part of the DCP crypto driver in 171 ``drivers/crypto/mxs-dcp.c``. 172 173 (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore) 174 175 Platform Keystore has well documented interfaces in PAPR document. 176 Refer to ``Documentation/arch/powerpc/papr_hcalls.rst`` 177 178 * Threat model 179 180 The strength and appropriateness of a particular trust source for a given 181 purpose must be assessed when using them to protect security-relevant data. 182 183 184Key Generation 185============== 186 187Trusted Keys 188------------ 189 190New keys are created from random numbers. They are encrypted/decrypted using 191a child key in the storage key hierarchy. Encryption and decryption of the 192child key must be protected by a strong access control policy within the 193trust source. The random number generator in use differs according to the 194selected trust source: 195 196 * TPM: hardware device based RNG 197 198 Keys are generated within the TPM. Strength of random numbers may vary 199 from one device manufacturer to another. 200 201 * TEE: OP-TEE based on Arm TrustZone based RNG 202 203 RNG is customizable as per platform needs. It can either be direct output 204 from platform specific hardware RNG or a software based Fortuna CSPRNG 205 which can be seeded via multiple entropy sources. 206 207 * CAAM: Kernel RNG 208 209 The normal kernel random number generator is used. To seed it from the 210 CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device 211 is probed. 212 213 * DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs) 214 215 The DCP hardware device itself does not provide a dedicated RNG interface, 216 so the kernel default RNG is used. SoCs with DCP like the i.MX6ULL do have 217 a dedicated hardware RNG that is independent from DCP which can be enabled 218 to back the kernel RNG. 219 220 * PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore) 221 222 The normal kernel random number generator is used to generate keys. 223 224Users may override this by specifying ``trusted.rng=kernel`` on the kernel 225command-line to override the used RNG with the kernel's random number pool. 226 227Encrypted Keys 228-------------- 229 230Encrypted keys do not depend on a trust source, and are faster, as they use AES 231for encryption/decryption. New keys are created either from kernel-generated 232random numbers or user-provided decrypted data, and are encrypted/decrypted 233using a specified ‘master’ key. The ‘master’ key can either be a trusted-key or 234user-key type. The main disadvantage of encrypted keys is that if they are not 235rooted in a trusted key, they are only as secure as the user key encrypting 236them. The master user key should therefore be loaded in as secure a way as 237possible, preferably early in boot. 238 239 240Usage 241===== 242 243Trusted Keys usage: TPM 244----------------------- 245 246TPM 1.2: By default, trusted keys are sealed under the SRK, which has the 247default authorization value (20 bytes of 0s). This can be set at takeownership 248time with the TrouSerS utility: "tpm_takeownership -u -z". 249 250TPM 2.0: The user must first create a storage key and make it persistent, so the 251key is available after reboot. This can be done using the following commands. 252 253With the IBM TSS 2 stack:: 254 255 #> tsscreateprimary -hi o -st 256 Handle 80000000 257 #> tssevictcontrol -hi o -ho 80000000 -hp 81000001 258 259Or with the Intel TSS 2 stack:: 260 261 #> tpm2_createprimary --hierarchy o -G rsa2048 -c key.ctxt 262 [...] 263 #> tpm2_evictcontrol -c key.ctxt 0x81000001 264 persistentHandle: 0x81000001 265 266Usage:: 267 268 keyctl add trusted name "new keylen [options]" ring 269 keyctl add trusted name "load hex_blob [pcrlock=pcrnum]" ring 270 keyctl update key "update [options]" 271 keyctl print keyid 272 273 options: 274 keyhandle= ascii hex value of sealing key 275 TPM 1.2: default 0x40000000 (SRK) 276 TPM 2.0: no default; must be passed every time 277 keyauth= ascii hex auth for sealing key default 0x00...i 278 (40 ascii zeros) 279 blobauth= ascii hex auth for sealed data default 0x00... 280 (40 ascii zeros) 281 pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no default) 282 pcrlock= pcr number to be extended to "lock" blob 283 migratable= 0|1 indicating permission to reseal to new PCR values, 284 default 1 (resealing allowed) 285 hash= hash algorithm name as a string. For TPM 1.x the only 286 allowed value is sha1. For TPM 2.x the allowed values 287 are sha1, sha256, sha384, sha512 and sm3-256. 288 policydigest= digest for the authorization policy. must be calculated 289 with the same hash algorithm as specified by the 'hash=' 290 option. 291 policyhandle= handle to an authorization policy session that defines the 292 same policy and with the same hash algorithm as was used to 293 seal the key. 294 295"keyctl print" returns an ascii hex copy of the sealed key, which is in standard 296TPM_STORED_DATA format. The key length for new keys are always in bytes. 297Trusted Keys can be 32 - 128 bytes (256 - 1024 bits), the upper limit is to fit 298within the 2048 bit SRK (RSA) keylength, with all necessary structure/padding. 299 300Trusted Keys usage: TEE 301----------------------- 302 303Usage:: 304 305 keyctl add trusted name "new keylen" ring 306 keyctl add trusted name "load hex_blob" ring 307 keyctl print keyid 308 309"keyctl print" returns an ASCII hex copy of the sealed key, which is in format 310specific to TEE device implementation. The key length for new keys is always 311in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). 312 313Trusted Keys usage: CAAM 314------------------------ 315 316Trusted Keys Usage:: 317 318 keyctl add trusted name "new keylen" ring 319 keyctl add trusted name "load hex_blob" ring 320 keyctl print keyid 321 322"keyctl print" returns an ASCII hex copy of the sealed key, which is in a 323CAAM-specific format. The key length for new keys is always in bytes. 324Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). 325 326Trusted Keys as Protected Keys Usage:: 327 328 keyctl add trusted name "new keylen pk [options]" ring 329 keyctl add trusted name "load hex_blob [options]" ring 330 keyctl print keyid 331 332 where, 'pk' is used to direct trust source to generate protected key. 333 334 options: 335 key_enc_algo = For CAAM, supported enc algo are ECB(2), CCM(1). 336 337"keyctl print" returns an ASCII hex copy of the sealed key, which is in a 338CAAM-specific format. The key length for new keys is always in bytes. 339Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). 340 341Trusted Keys usage: DCP 342----------------------- 343 344Usage:: 345 346 keyctl add trusted name "new keylen" ring 347 keyctl add trusted name "load hex_blob" ring 348 keyctl print keyid 349 350"keyctl print" returns an ASCII hex copy of the sealed key, which is in format 351specific to this DCP key-blob implementation. The key length for new keys is 352always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). 353 354Trusted Keys usage: PKWM 355------------------------ 356 357Usage:: 358 359 keyctl add trusted name "new keylen [options]" ring 360 keyctl add trusted name "load hex_blob" ring 361 keyctl print keyid 362 363 options: 364 wrap_flags= ascii hex value of security policy requirement 365 0x00: no secure boot requirement (default) 366 0x01: require secure boot to be in either audit or 367 enforced mode 368 0x02: require secure boot to be in enforced mode 369 370"keyctl print" returns an ASCII hex copy of the sealed key, which is in format 371specific to PKWM key-blob implementation. The key length for new keys is 372always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). 373 374Encrypted Keys usage 375-------------------- 376 377The decrypted portion of encrypted keys can contain either a simple symmetric 378key or a more complex structure. The format of the more complex structure is 379application specific, which is identified by 'format'. 380 381Usage:: 382 383 keyctl add encrypted name "new [format] key-type:master-key-name keylen" 384 ring 385 keyctl add encrypted name "new [format] key-type:master-key-name keylen 386 decrypted-data" ring 387 keyctl add encrypted name "load hex_blob" ring 388 keyctl update keyid "update key-type:master-key-name" 389 390Where:: 391 392 format:= 'default | ecryptfs | enc32' 393 key-type:= 'trusted' | 'user' 394 395Examples of trusted and encrypted key usage 396------------------------------------------- 397 398Create and save a trusted key named "kmk" of length 32 bytes. 399 400Note: When using a TPM 2.0 with a persistent key with handle 0x81000001, 401append 'keyhandle=0x81000001' to statements between quotes, such as 402"new 32 keyhandle=0x81000001". 403 404:: 405 406 $ keyctl add trusted kmk "new 32" @u 407 440502848 408 409 $ keyctl show 410 Session Keyring 411 -3 --alswrv 500 500 keyring: _ses 412 97833714 --alswrv 500 -1 \_ keyring: _uid.500 413 440502848 --alswrv 500 500 \_ trusted: kmk 414 415 $ keyctl print 440502848 416 0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915 417 3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b 418 27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722 419 a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec 420 d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d 421 dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0 422 f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b 423 e4a8aea2b607ec96931e6f4d4fe563ba 424 425 $ keyctl pipe 440502848 > kmk.blob 426 427Load a trusted key from the saved blob:: 428 429 $ keyctl add trusted kmk "load `cat kmk.blob`" @u 430 268728824 431 432 $ keyctl print 268728824 433 0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915 434 3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b 435 27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722 436 a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec 437 d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d 438 dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0 439 f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b 440 e4a8aea2b607ec96931e6f4d4fe563ba 441 442Create and save a trusted key as protected key named "kmk" of length 32 bytes. 443 444:: 445 446 $ keyctl add trusted kmk "new 32 pk key_enc_algo=1" @u 447 440502848 448 449 $ keyctl show 450 Session Keyring 451 -3 --alswrv 500 500 keyring: _ses 452 97833714 --alswrv 500 -1 \_ keyring: _uid.500 453 440502848 --alswrv 500 500 \_ trusted: kmk 454 455 $ keyctl print 440502848 456 0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915 457 3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b 458 27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722 459 a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec 460 d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d 461 dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0 462 f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b 463 e4a8aea2b607ec96931e6f4d4fe563ba 464 465 $ keyctl pipe 440502848 > kmk.blob 466 467Load a trusted key from the saved blob:: 468 469 $ keyctl add trusted kmk "load `cat kmk.blob` key_enc_algo=1" @u 470 268728824 471 472 $ keyctl print 268728824 473 0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915 474 3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b 475 27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722 476 a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec 477 d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d 478 dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0 479 f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b 480 e4a8aea2b607ec96931e6f4d4fe563ba 481 482Reseal (TPM specific) a trusted key under new PCR values:: 483 484 $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`" 485 $ keyctl print 268728824 486 010100000000002c0002800093c35a09b70fff26e7a98ae786c641e678ec6ffb6b46d805 487 77c8a6377aed9d3219c6dfec4b23ffe3000001005d37d472ac8a44023fbb3d18583a4f73 488 d3a076c0858f6f1dcaa39ea0f119911ff03f5406df4f7f27f41da8d7194f45c9f4e00f2e 489 df449f266253aa3f52e55c53de147773e00f0f9aca86c64d94c95382265968c354c5eab4 490 9638c5ae99c89de1e0997242edfb0b501744e11ff9762dfd951cffd93227cc513384e7e6 491 e782c29435c7ec2edafaa2f4c1fe6e7a781b59549ff5296371b42133777dcc5b8b971610 492 94bc67ede19e43ddb9dc2baacad374a36feaf0314d700af0a65c164b7082401740e489c9 493 7ef6a24defe4846104209bf0c3eced7fa1a672ed5b125fc9d8cd88b476a658a4434644ef 494 df8ae9a178e9f83ba9f08d10fa47e4226b98b0702f06b3b8 495 496 497The initial consumer of trusted keys is EVM, which at boot time needs a high 498quality symmetric key for HMAC protection of file metadata. The use of a 499trusted key provides strong guarantees that the EVM key has not been 500compromised by a user level problem, and when sealed to a platform integrity 501state, protects against boot and offline attacks. Create and save an 502encrypted key "evm" using the above trusted key "kmk": 503 504option 1: omitting 'format':: 505 506 $ keyctl add encrypted evm "new trusted:kmk 32" @u 507 159771175 508 509option 2: explicitly defining 'format' as 'default':: 510 511 $ keyctl add encrypted evm "new default trusted:kmk 32" @u 512 159771175 513 514 $ keyctl print 159771175 515 default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3 516 82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0 517 24717c64 5972dcb82ab2dde83376d82b2e3c09ffc 518 519 $ keyctl pipe 159771175 > evm.blob 520 521Load an encrypted key "evm" from saved blob:: 522 523 $ keyctl add encrypted evm "load `cat evm.blob`" @u 524 831684262 525 526 $ keyctl print 831684262 527 default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3 528 82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0 529 24717c64 5972dcb82ab2dde83376d82b2e3c09ffc 530 531Instantiate an encrypted key "evm" using user-provided decrypted data:: 532 533 $ evmkey=$(dd if=/dev/urandom bs=1 count=32 | xxd -c32 -p) 534 $ keyctl add encrypted evm "new default user:kmk 32 $evmkey" @u 535 794890253 536 537 $ keyctl print 794890253 538 default user:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382d 539 bbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0247 540 17c64 5972dcb82ab2dde83376d82b2e3c09ffc 541 542Other uses for trusted and encrypted keys, such as for disk and file encryption 543are anticipated. In particular the new format 'ecryptfs' has been defined 544in order to use encrypted keys to mount an eCryptfs filesystem. More details 545about the usage can be found in the file 546``Documentation/security/keys/ecryptfs.rst``. 547 548Another new format 'enc32' has been defined in order to support encrypted keys 549with payload size of 32 bytes. This will initially be used for nvdimm security 550but may expand to other usages that require 32 bytes payload. 551 552 553TPM 2.0 ASN.1 Key Format 554------------------------ 555 556The TPM 2.0 ASN.1 key format is designed to be easily recognisable, 557even in binary form (fixing a problem we had with the TPM 1.2 ASN.1 558format) and to be extensible for additions like importable keys and 559policy:: 560 561 TPMKey ::= SEQUENCE { 562 type OBJECT IDENTIFIER 563 emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL 564 parent INTEGER 565 pubkey OCTET STRING 566 privkey OCTET STRING 567 } 568 569type is what distinguishes the key even in binary form since the OID 570is provided by the TCG to be unique and thus forms a recognizable 571binary pattern at offset 3 in the key. The OIDs currently made 572available are:: 573 574 2.23.133.10.1.3 TPM Loadable key. This is an asymmetric key (Usually 575 RSA2048 or Elliptic Curve) which can be imported by a 576 TPM2_Load() operation. 577 578 2.23.133.10.1.4 TPM Importable Key. This is an asymmetric key (Usually 579 RSA2048 or Elliptic Curve) which can be imported by a 580 TPM2_Import() operation. 581 582 2.23.133.10.1.5 TPM Sealed Data. This is a set of data (up to 128 583 bytes) which is sealed by the TPM. It usually 584 represents a symmetric key and must be unsealed before 585 use. 586 587The trusted key code only uses the TPM Sealed Data OID. 588 589emptyAuth is true if the key has well known authorization "". If it 590is false or not present, the key requires an explicit authorization 591phrase. This is used by most user space consumers to decide whether 592to prompt for a password. 593 594parent represents the parent key handle, either in the 0x81 MSO space, 595like 0x81000001 for the RSA primary storage key. Userspace programmes 596also support specifying the primary handle in the 0x40 MSO space. If 597this happens the Elliptic Curve variant of the primary key using the 598TCG defined template will be generated on the fly into a volatile 599object and used as the parent. The current kernel code only supports 600the 0x81 MSO form. 601 602pubkey is the binary representation of TPM2B_PRIVATE excluding the 603initial TPM2B header, which can be reconstructed from the ASN.1 octet 604string length. 605 606privkey is the binary representation of TPM2B_PUBLIC excluding the 607initial TPM2B header which can be reconstructed from the ASN.1 octed 608string length. 609 610DCP Blob Format 611--------------- 612 613.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c 614 :doc: dcp blob format 615 616.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c 617 :identifiers: struct dcp_blob_fmt 618