[linux-2.6-block.git] / Documentation / security / keys / trusted-encrypted.rst

==========================
Trusted and Encrypted Keys
==========================

Trusted and Encrypted Keys are two new key types added to the existing kernel
key ring service.  Both of these new types are variable length symmetric keys,
and in both cases all keys are created in the kernel, and user space sees,
stores, and loads only encrypted blobs.  Trusted Keys require the availability
of a Trust Source for greater security, while Encrypted Keys can be used on any
system. All user level blobs, are displayed and loaded in hex ASCII for
convenience, and are integrity verified.


Trust Source
============

A trust source provides the source of security for Trusted Keys.  This
section lists currently supported trust sources, along with their security
considerations.  Whether or not a trust source is sufficiently safe depends
on the strength and correctness of its implementation, as well as the threat
environment for a specific use case.  Since the kernel doesn't know what the
environment is, and there is no metric of trust, it is dependent on the
consumer of the Trusted Keys to determine if the trust source is sufficiently
safe.

  *  Root of trust for storage

     (1) TPM (Trusted Platform Module: hardware device)

         Rooted to Storage Root Key (SRK) which never leaves the TPM that
         provides crypto operation to establish root of trust for storage.

     (2) TEE (Trusted Execution Environment: OP-TEE based on Arm TrustZone)

         Rooted to Hardware Unique Key (HUK) which is generally burnt in on-chip
         fuses and is accessible to TEE only.

     (3) CAAM (Cryptographic Acceleration and Assurance Module: IP on NXP SoCs)

         When High Assurance Boot (HAB) is enabled and the CAAM is in secure
         mode, trust is rooted to the OTPMK, a never-disclosed 256-bit key
         randomly generated and fused into each SoC at manufacturing time.
         Otherwise, a common fixed test key is used instead.

  *  Execution isolation

     (1) TPM

         Fixed set of operations running in isolated execution environment.

     (2) TEE

         Customizable set of operations running in isolated execution
         environment verified via Secure/Trusted boot process.

     (3) CAAM

         Fixed set of operations running in isolated execution environment.

  * Optional binding to platform integrity state

     (1) TPM

         Keys can be optionally sealed to specified PCR (integrity measurement)
         values, and only unsealed by the TPM, if PCRs and blob integrity
         verifications match. A loaded Trusted Key can be updated with new
         (future) PCR values, so keys are easily migrated to new PCR values,
         such as when the kernel and initramfs are updated. The same key can
         have many saved blobs under different PCR values, so multiple boots are
         easily supported.

     (2) TEE

         Relies on Secure/Trusted boot process for platform integrity. It can
         be extended with TEE based measured boot process.

     (3) CAAM

         Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs
         for platform integrity.

  *  Interfaces and APIs

     (1) TPM

         TPMs have well-documented, standardized interfaces and APIs.

     (2) TEE

         TEEs have well-documented, standardized client interface and APIs. For
         more details refer to ``Documentation/staging/tee.rst``.

     (3) CAAM

         Interface is specific to silicon vendor.

  *  Threat model

     The strength and appropriateness of a particular trust source for a given
     purpose must be assessed when using them to protect security-relevant data.


Key Generation
==============

Trusted Keys
------------

New keys are created from random numbers. They are encrypted/decrypted using
a child key in the storage key hierarchy. Encryption and decryption of the
child key must be protected by a strong access control policy within the
trust source. The random number generator in use differs according to the
selected trust source:

  *  TPM: hardware device based RNG

     Keys are generated within the TPM. Strength of random numbers may vary
     from one device manufacturer to another.

  *  TEE: OP-TEE based on Arm TrustZone based RNG

     RNG is customizable as per platform needs. It can either be direct output
     from platform specific hardware RNG or a software based Fortuna CSPRNG
     which can be seeded via multiple entropy sources.

  *  CAAM: Kernel RNG

     The normal kernel random number generator is used. To seed it from the
     CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device
     is probed.

Users may override this by specifying ``trusted.rng=kernel`` on the kernel
command-line to override the used RNG with the kernel's random number pool.

Encrypted Keys
--------------

Encrypted keys do not depend on a trust source, and are faster, as they use AES
for encryption/decryption. New keys are created either from kernel-generated
random numbers or user-provided decrypted data, and are encrypted/decrypted
using a specified ‘master’ key. The ‘master’ key can either be a trusted-key or
user-key type. The main disadvantage of encrypted keys is that if they are not
rooted in a trusted key, they are only as secure as the user key encrypting
them. The master user key should therefore be loaded in as secure a way as
possible, preferably early in boot.


Usage
=====

Trusted Keys usage: TPM
-----------------------

TPM 1.2: By default, trusted keys are sealed under the SRK, which has the
default authorization value (20 bytes of 0s).  This can be set at takeownership
time with the TrouSerS utility: "tpm_takeownership -u -z".

TPM 2.0: The user must first create a storage key and make it persistent, so the
key is available after reboot. This can be done using the following commands.

With the IBM TSS 2 stack::

  #> tsscreateprimary -hi o -st
  Handle 80000000
  #> tssevictcontrol -hi o -ho 80000000 -hp 81000001

Or with the Intel TSS 2 stack::

  #> tpm2_createprimary --hierarchy o -G rsa2048 -c key.ctxt
  [...]
  #> tpm2_evictcontrol -c key.ctxt 0x81000001
  persistentHandle: 0x81000001

Usage::

    keyctl add trusted name "new keylen [options]" ring
    keyctl add trusted name "load hex_blob [pcrlock=pcrnum]" ring
    keyctl update key "update [options]"
    keyctl print keyid

    options:
       keyhandle=    ascii hex value of sealing key
                       TPM 1.2: default 0x40000000 (SRK)
                       TPM 2.0: no default; must be passed every time
       keyauth=	     ascii hex auth for sealing key default 0x00...i
                     (40 ascii zeros)
       blobauth=     ascii hex auth for sealed data default 0x00...
                     (40 ascii zeros)
       pcrinfo=	     ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
       pcrlock=	     pcr number to be extended to "lock" blob
       migratable=   0|1 indicating permission to reseal to new PCR values,
                     default 1 (resealing allowed)
       hash=         hash algorithm name as a string. For TPM 1.x the only
                     allowed value is sha1. For TPM 2.x the allowed values
                     are sha1, sha256, sha384, sha512 and sm3-256.
       policydigest= digest for the authorization policy. must be calculated
                     with the same hash algorithm as specified by the 'hash='
                     option.
       policyhandle= handle to an authorization policy session that defines the
                     same policy and with the same hash algorithm as was used to
                     seal the key.

"keyctl print" returns an ascii hex copy of the sealed key, which is in standard
TPM_STORED_DATA format.  The key length for new keys are always in bytes.
Trusted Keys can be 32 - 128 bytes (256 - 1024 bits), the upper limit is to fit
within the 2048 bit SRK (RSA) keylength, with all necessary structure/padding.

Trusted Keys usage: TEE
-----------------------

Usage::

    keyctl add trusted name "new keylen" ring
    keyctl add trusted name "load hex_blob" ring
    keyctl print keyid

"keyctl print" returns an ASCII hex copy of the sealed key, which is in format
specific to TEE device implementation.  The key length for new keys is always
in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).

Trusted Keys usage: CAAM
------------------------

Usage::

    keyctl add trusted name "new keylen" ring
    keyctl add trusted name "load hex_blob" ring
    keyctl print keyid

"keyctl print" returns an ASCII hex copy of the sealed key, which is in a
CAAM-specific format.  The key length for new keys is always in bytes.
Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).

Encrypted Keys usage
--------------------

The decrypted portion of encrypted keys can contain either a simple symmetric
key or a more complex structure. The format of the more complex structure is
application specific, which is identified by 'format'.

Usage::

    keyctl add encrypted name "new [format] key-type:master-key-name keylen"
        ring
    keyctl add encrypted name "new [format] key-type:master-key-name keylen
        decrypted-data" ring
    keyctl add encrypted name "load hex_blob" ring
    keyctl update keyid "update key-type:master-key-name"

Where::

	format:= 'default | ecryptfs | enc32'
	key-type:= 'trusted' | 'user'

Examples of trusted and encrypted key usage
-------------------------------------------

Create and save a trusted key named "kmk" of length 32 bytes.

Note: When using a TPM 2.0 with a persistent key with handle 0x81000001,
append 'keyhandle=0x81000001' to statements between quotes, such as
"new 32 keyhandle=0x81000001".

::

    $ keyctl add trusted kmk "new 32" @u
    440502848

    $ keyctl show
    Session Keyring
           -3 --alswrv    500   500  keyring: _ses
     97833714 --alswrv    500    -1   \_ keyring: _uid.500
    440502848 --alswrv    500   500       \_ trusted: kmk

    $ keyctl print 440502848
    0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
    3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
    27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
    a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
    d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
    dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
    f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
    e4a8aea2b607ec96931e6f4d4fe563ba

    $ keyctl pipe 440502848 > kmk.blob

Load a trusted key from the saved blob::

    $ keyctl add trusted kmk "load `cat kmk.blob`" @u
    268728824

    $ keyctl print 268728824
    0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
    3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
    27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
    a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
    d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
    dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
    f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
    e4a8aea2b607ec96931e6f4d4fe563ba

Reseal (TPM specific) a trusted key under new PCR values::

    $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
    $ keyctl print 268728824
    010100000000002c0002800093c35a09b70fff26e7a98ae786c641e678ec6ffb6b46d805
    77c8a6377aed9d3219c6dfec4b23ffe3000001005d37d472ac8a44023fbb3d18583a4f73
    d3a076c0858f6f1dcaa39ea0f119911ff03f5406df4f7f27f41da8d7194f45c9f4e00f2e
    df449f266253aa3f52e55c53de147773e00f0f9aca86c64d94c95382265968c354c5eab4
    9638c5ae99c89de1e0997242edfb0b501744e11ff9762dfd951cffd93227cc513384e7e6
    e782c29435c7ec2edafaa2f4c1fe6e7a781b59549ff5296371b42133777dcc5b8b971610
    94bc67ede19e43ddb9dc2baacad374a36feaf0314d700af0a65c164b7082401740e489c9
    7ef6a24defe4846104209bf0c3eced7fa1a672ed5b125fc9d8cd88b476a658a4434644ef
    df8ae9a178e9f83ba9f08d10fa47e4226b98b0702f06b3b8


The initial consumer of trusted keys is EVM, which at boot time needs a high
quality symmetric key for HMAC protection of file metadata. The use of a
trusted key provides strong guarantees that the EVM key has not been
compromised by a user level problem, and when sealed to a platform integrity
state, protects against boot and offline attacks. Create and save an
encrypted key "evm" using the above trusted key "kmk":

option 1: omitting 'format'::

    $ keyctl add encrypted evm "new trusted:kmk 32" @u
    159771175

option 2: explicitly defining 'format' as 'default'::

    $ keyctl add encrypted evm "new default trusted:kmk 32" @u
    159771175

    $ keyctl print 159771175
    default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3
    82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
    24717c64 5972dcb82ab2dde83376d82b2e3c09ffc

    $ keyctl pipe 159771175 > evm.blob

Load an encrypted key "evm" from saved blob::

    $ keyctl add encrypted evm "load `cat evm.blob`" @u
    831684262

    $ keyctl print 831684262
    default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3
    82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
    24717c64 5972dcb82ab2dde83376d82b2e3c09ffc

Instantiate an encrypted key "evm" using user-provided decrypted data::

    $ evmkey=$(dd if=/dev/urandom bs=1 count=32 | xxd -c32 -p)
    $ keyctl add encrypted evm "new default user:kmk 32 $evmkey" @u
    794890253

    $ keyctl print 794890253
    default user:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382d
    bbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0247
    17c64 5972dcb82ab2dde83376d82b2e3c09ffc

Other uses for trusted and encrypted keys, such as for disk and file encryption
are anticipated.  In particular the new format 'ecryptfs' has been defined
in order to use encrypted keys to mount an eCryptfs filesystem.  More details
about the usage can be found in the file
``Documentation/security/keys/ecryptfs.rst``.

Another new format 'enc32' has been defined in order to support encrypted keys
with payload size of 32 bytes. This will initially be used for nvdimm security
but may expand to other usages that require 32 bytes payload.


TPM 2.0 ASN.1 Key Format
------------------------

The TPM 2.0 ASN.1 key format is designed to be easily recognisable,
even in binary form (fixing a problem we had with the TPM 1.2 ASN.1
format) and to be extensible for additions like importable keys and
policy::

    TPMKey ::= SEQUENCE {
        type		OBJECT IDENTIFIER
        emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL
        parent		INTEGER
        pubkey		OCTET STRING
        privkey		OCTET STRING
    }

type is what distinguishes the key even in binary form since the OID
is provided by the TCG to be unique and thus forms a recognizable
binary pattern at offset 3 in the key.  The OIDs currently made
available are::

    2.23.133.10.1.3 TPM Loadable key.  This is an asymmetric key (Usually
                    RSA2048 or Elliptic Curve) which can be imported by a
                    TPM2_Load() operation.

    2.23.133.10.1.4 TPM Importable Key.  This is an asymmetric key (Usually
                    RSA2048 or Elliptic Curve) which can be imported by a
                    TPM2_Import() operation.

    2.23.133.10.1.5 TPM Sealed Data.  This is a set of data (up to 128
                    bytes) which is sealed by the TPM.  It usually
                    represents a symmetric key and must be unsealed before
                    use.

The trusted key code only uses the TPM Sealed Data OID.

emptyAuth is true if the key has well known authorization "".  If it
is false or not present, the key requires an explicit authorization
phrase.  This is used by most user space consumers to decide whether
to prompt for a password.

parent represents the parent key handle, either in the 0x81 MSO space,
like 0x81000001 for the RSA primary storage key.  Userspace programmes
also support specifying the primary handle in the 0x40 MSO space.  If
this happens the Elliptic Curve variant of the primary key using the
TCG defined template will be generated on the fly into a volatile
object and used as the parent.  The current kernel code only supports
the 0x81 MSO form.

pubkey is the binary representation of TPM2B_PRIVATE excluding the
initial TPM2B header, which can be reconstructed from the ASN.1 octet
string length.

privkey is the binary representation of TPM2B_PUBLIC excluding the
initial TPM2B header which can be reconstructed from the ASN.1 octed
string length.
Commit	Line	Data
5395d312 KC	1	==========================
	2	Trusted and Encrypted Keys
	3	==========================
d00a1c72 MZ	4
d00a1c72 MZ	5	Trusted and Encrypted Keys are two new key types added to the existing kernel
40e47125	6	key ring service. Both of these new types are variable length symmetric keys,
d00a1c72 MZ	7	and in both cases all keys are created in the kernel, and user space sees,
d00a1c72 MZ	8	stores, and loads only encrypted blobs. Trusted Keys require the availability
c429805f SG	9	of a Trust Source for greater security, while Encrypted Keys can be used on any
	10	system. All user level blobs, are displayed and loaded in hex ASCII for
	11	convenience, and are integrity verified.
d00a1c72	12
d00a1c72	13
c429805f SG	14	Trust Source
c429805f SG	15	============
4264f27a	16
c429805f SG	17	A trust source provides the source of security for Trusted Keys. This
	18	section lists currently supported trust sources, along with their security
	19	considerations. Whether or not a trust source is sufficiently safe depends
	20	on the strength and correctness of its implementation, as well as the threat
	21	environment for a specific use case. Since the kernel doesn't know what the
	22	environment is, and there is no metric of trust, it is dependent on the
	23	consumer of the Trusted Keys to determine if the trust source is sufficiently
	24	safe.
d00a1c72	25
c429805f	26	* Root of trust for storage
4264f27a	27
c429805f SG	28	(1) TPM (Trusted Platform Module: hardware device)
	29
	30	Rooted to Storage Root Key (SRK) which never leaves the TPM that
	31	provides crypto operation to establish root of trust for storage.
	32
	33	(2) TEE (Trusted Execution Environment: OP-TEE based on Arm TrustZone)
	34
	35	Rooted to Hardware Unique Key (HUK) which is generally burnt in on-chip
	36	fuses and is accessible to TEE only.
	37
5002426e AF	38	(3) CAAM (Cryptographic Acceleration and Assurance Module: IP on NXP SoCs)
	39
	40	When High Assurance Boot (HAB) is enabled and the CAAM is in secure
	41	mode, trust is rooted to the OTPMK, a never-disclosed 256-bit key
	42	randomly generated and fused into each SoC at manufacturing time.
	43	Otherwise, a common fixed test key is used instead.
	44
c429805f SG	45	* Execution isolation
	46
	47	(1) TPM
	48
	49	Fixed set of operations running in isolated execution environment.
	50
	51	(2) TEE
	52
	53	Customizable set of operations running in isolated execution
	54	environment verified via Secure/Trusted boot process.
	55
5002426e AF	56	(3) CAAM
	57
	58	Fixed set of operations running in isolated execution environment.
	59
c429805f SG	60	* Optional binding to platform integrity state
	61
	62	(1) TPM
	63
	64	Keys can be optionally sealed to specified PCR (integrity measurement)
	65	values, and only unsealed by the TPM, if PCRs and blob integrity
	66	verifications match. A loaded Trusted Key can be updated with new
	67	(future) PCR values, so keys are easily migrated to new PCR values,
	68	such as when the kernel and initramfs are updated. The same key can
	69	have many saved blobs under different PCR values, so multiple boots are
	70	easily supported.
	71
	72	(2) TEE
	73
	74	Relies on Secure/Trusted boot process for platform integrity. It can
	75	be extended with TEE based measured boot process.
	76
5002426e AF	77	(3) CAAM
	78
	79	Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs
	80	for platform integrity.
	81
c429805f SG	82	* Interfaces and APIs
	83
	84	(1) TPM
	85
	86	TPMs have well-documented, standardized interfaces and APIs.
	87
	88	(2) TEE
	89
	90	TEEs have well-documented, standardized client interface and APIs. For
	91	more details refer to ``Documentation/staging/tee.rst``.
	92
5002426e AF	93	(3) CAAM
	94
	95	Interface is specific to silicon vendor.
c429805f SG	96
	97	* Threat model
	98
5002426e	99	The strength and appropriateness of a particular trust source for a given
c429805f SG	100	purpose must be assessed when using them to protect security-relevant data.
	101
	102
	103	Key Generation
	104	==============
	105
	106	Trusted Keys
	107	------------
	108
fcd7c269 AF	109	New keys are created from random numbers. They are encrypted/decrypted using
	110	a child key in the storage key hierarchy. Encryption and decryption of the
	111	child key must be protected by a strong access control policy within the
	112	trust source. The random number generator in use differs according to the
	113	selected trust source:
c429805f	114
fcd7c269	115	* TPM: hardware device based RNG
c429805f	116
fcd7c269 AF	117	Keys are generated within the TPM. Strength of random numbers may vary
fcd7c269 AF	118	from one device manufacturer to another.
c429805f	119
fcd7c269	120	* TEE: OP-TEE based on Arm TrustZone based RNG
c429805f SG	121
	122	RNG is customizable as per platform needs. It can either be direct output
	123	from platform specific hardware RNG or a software based Fortuna CSPRNG
	124	which can be seeded via multiple entropy sources.
	125
5002426e AF	126	* CAAM: Kernel RNG
	127
	128	The normal kernel random number generator is used. To seed it from the
	129	CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device
	130	is probed.
	131
fcd7c269 AF	132	Users may override this by specifying ``trusted.rng=kernel`` on the kernel
	133	command-line to override the used RNG with the kernel's random number pool.
	134
c429805f SG	135	Encrypted Keys
	136	--------------
	137
	138	Encrypted keys do not depend on a trust source, and are faster, as they use AES
cd3bc044 YT	139	for encryption/decryption. New keys are created either from kernel-generated
	140	random numbers or user-provided decrypted data, and are encrypted/decrypted
	141	using a specified ‘master’ key. The ‘master’ key can either be a trusted-key or
	142	user-key type. The main disadvantage of encrypted keys is that if they are not
	143	rooted in a trusted key, they are only as secure as the user key encrypting
	144	them. The master user key should therefore be loaded in as secure a way as
	145	possible, preferably early in boot.
c429805f SG	146
	147
	148	Usage
	149	=====
	150
	151	Trusted Keys usage: TPM
	152	-----------------------
	153
	154	TPM 1.2: By default, trusted keys are sealed under the SRK, which has the
	155	default authorization value (20 bytes of 0s). This can be set at takeownership
	156	time with the TrouSerS utility: "tpm_takeownership -u -z".
	157
	158	TPM 2.0: The user must first create a storage key and make it persistent, so the
	159	key is available after reboot. This can be done using the following commands.
4264f27a SB	160
	161	With the IBM TSS 2 stack::
	162
	163	#> tsscreateprimary -hi o -st
	164	Handle 80000000
	165	#> tssevictcontrol -hi o -ho 80000000 -hp 81000001
	166
	167	Or with the Intel TSS 2 stack::
	168
bb84bc51	169	#> tpm2_createprimary --hierarchy o -G rsa2048 -c key.ctxt
4264f27a	170	[...]
bb84bc51	171	#> tpm2_evictcontrol -c key.ctxt 0x81000001
4264f27a SB	172	persistentHandle: 0x81000001
4264f27a SB	173
5395d312 KC	174	Usage::
5395d312 KC	175
d00a1c72 MZ	176	keyctl add trusted name "new keylen [options]" ring
	177	keyctl add trusted name "load hex_blob [pcrlock=pcrnum]" ring
	178	keyctl update key "update [options]"
	179	keyctl print keyid
	180
	181	options:
4264f27a SB	182	keyhandle= ascii hex value of sealing key
	183	TPM 1.2: default 0x40000000 (SRK)
	184	TPM 2.0: no default; must be passed every time
5beb0c43 JS	185	keyauth= ascii hex auth for sealing key default 0x00...i
	186	(40 ascii zeros)
	187	blobauth= ascii hex auth for sealed data default 0x00...
	188	(40 ascii zeros)
5beb0c43 JS	189	pcrinfo= ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
	190	pcrlock= pcr number to be extended to "lock" blob
	191	migratable= 0\|1 indicating permission to reseal to new PCR values,
	192	default 1 (resealing allowed)
	193	hash= hash algorithm name as a string. For TPM 1.x the only
	194	allowed value is sha1. For TPM 2.x the allowed values
	195	are sha1, sha256, sha384, sha512 and sm3-256.
	196	policydigest= digest for the authorization policy. must be calculated
	197	with the same hash algorithm as specified by the 'hash='
	198	option.
	199	policyhandle= handle to an authorization policy session that defines the
	200	same policy and with the same hash algorithm as was used to
	201	seal the key.
d00a1c72 MZ	202
	203	"keyctl print" returns an ascii hex copy of the sealed key, which is in standard
	204	TPM_STORED_DATA format. The key length for new keys are always in bytes.
	205	Trusted Keys can be 32 - 128 bytes (256 - 1024 bits), the upper limit is to fit
	206	within the 2048 bit SRK (RSA) keylength, with all necessary structure/padding.
	207
c429805f SG	208	Trusted Keys usage: TEE
	209	-----------------------
	210
	211	Usage::
	212
	213	keyctl add trusted name "new keylen" ring
	214	keyctl add trusted name "load hex_blob" ring
	215	keyctl print keyid
	216
	217	"keyctl print" returns an ASCII hex copy of the sealed key, which is in format
	218	specific to TEE device implementation. The key length for new keys is always
	219	in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
	220
5002426e AF	221	Trusted Keys usage: CAAM
	222	------------------------
	223
	224	Usage::
	225
	226	keyctl add trusted name "new keylen" ring
	227	keyctl add trusted name "load hex_blob" ring
	228	keyctl print keyid
	229
	230	"keyctl print" returns an ASCII hex copy of the sealed key, which is in a
	231	CAAM-specific format. The key length for new keys is always in bytes.
	232	Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
	233
c429805f SG	234	Encrypted Keys usage
c429805f SG	235	--------------------
d00a1c72	236
4e561d38 RS	237	The decrypted portion of encrypted keys can contain either a simple symmetric
	238	key or a more complex structure. The format of the more complex structure is
	239	application specific, which is identified by 'format'.
	240
5395d312 KC	241	Usage::
5395d312 KC	242
4e561d38 RS	243	keyctl add encrypted name "new [format] key-type:master-key-name keylen"
4e561d38 RS	244	ring
cd3bc044 YT	245	keyctl add encrypted name "new [format] key-type:master-key-name keylen
cd3bc044 YT	246	decrypted-data" ring
4e561d38 RS	247	keyctl add encrypted name "load hex_blob" ring
	248	keyctl update keyid "update key-type:master-key-name"
	249
5395d312 KC	250	Where::
5395d312 KC	251
9db67581	252	format:= 'default \| ecryptfs \| enc32'
5395d312	253	key-type:= 'trusted' \| 'user'
d00a1c72	254
c429805f SG	255	Examples of trusted and encrypted key usage
c429805f SG	256	-------------------------------------------
d00a1c72	257
6ad8b216	258	Create and save a trusted key named "kmk" of length 32 bytes.
d00a1c72	259
4264f27a SB	260	Note: When using a TPM 2.0 with a persistent key with handle 0x81000001,
	261	append 'keyhandle=0x81000001' to statements between quotes, such as
	262	"new 32 keyhandle=0x81000001".
	263
6ad8b216 MCC	264	::
6ad8b216 MCC	265
d00a1c72 MZ	266	$ keyctl add trusted kmk "new 32" @u
	267	440502848
	268
	269	$ keyctl show
	270	Session Keyring
	271	-3 --alswrv 500 500 keyring: _ses
	272	97833714 --alswrv 500 -1 \_ keyring: _uid.500
	273	440502848 --alswrv 500 500 \_ trusted: kmk
	274
	275	$ keyctl print 440502848
	276	0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
	277	3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
	278	27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
	279	a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
	280	d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
	281	dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
	282	f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
	283	e4a8aea2b607ec96931e6f4d4fe563ba
	284
	285	$ keyctl pipe 440502848 > kmk.blob
	286
5395d312	287	Load a trusted key from the saved blob::
d00a1c72 MZ	288
	289	$ keyctl add trusted kmk "load `cat kmk.blob`" @u
	290	268728824
	291
	292	$ keyctl print 268728824
	293	0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
	294	3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
	295	27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
	296	a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
	297	d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
	298	dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
	299	f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
	300	e4a8aea2b607ec96931e6f4d4fe563ba
	301
c429805f	302	Reseal (TPM specific) a trusted key under new PCR values::
d00a1c72 MZ	303
	304	$ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
	305	$ keyctl print 268728824
	306	010100000000002c0002800093c35a09b70fff26e7a98ae786c641e678ec6ffb6b46d805
	307	77c8a6377aed9d3219c6dfec4b23ffe3000001005d37d472ac8a44023fbb3d18583a4f73
	308	d3a076c0858f6f1dcaa39ea0f119911ff03f5406df4f7f27f41da8d7194f45c9f4e00f2e
	309	df449f266253aa3f52e55c53de147773e00f0f9aca86c64d94c95382265968c354c5eab4
	310	9638c5ae99c89de1e0997242edfb0b501744e11ff9762dfd951cffd93227cc513384e7e6
	311	e782c29435c7ec2edafaa2f4c1fe6e7a781b59549ff5296371b42133777dcc5b8b971610
	312	94bc67ede19e43ddb9dc2baacad374a36feaf0314d700af0a65c164b7082401740e489c9
	313	7ef6a24defe4846104209bf0c3eced7fa1a672ed5b125fc9d8cd88b476a658a4434644ef
	314	df8ae9a178e9f83ba9f08d10fa47e4226b98b0702f06b3b8
	315
c429805f	316
4e561d38	317	The initial consumer of trusted keys is EVM, which at boot time needs a high
c429805f	318	quality symmetric key for HMAC protection of file metadata. The use of a
4e561d38	319	trusted key provides strong guarantees that the EVM key has not been
c429805f SG	320	compromised by a user level problem, and when sealed to a platform integrity
c429805f SG	321	state, protects against boot and offline attacks. Create and save an
4e561d38	322	encrypted key "evm" using the above trusted key "kmk":
d00a1c72	323
5395d312 KC	324	option 1: omitting 'format'::
5395d312 KC	325
d00a1c72 MZ	326	$ keyctl add encrypted evm "new trusted:kmk 32" @u
	327	159771175
	328
5395d312 KC	329	option 2: explicitly defining 'format' as 'default'::
5395d312 KC	330
4e561d38 RS	331	$ keyctl add encrypted evm "new default trusted:kmk 32" @u
	332	159771175
	333
d00a1c72	334	$ keyctl print 159771175
4e561d38 RS	335	default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3
	336	82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
	337	24717c64 5972dcb82ab2dde83376d82b2e3c09ffc
d00a1c72 MZ	338
	339	$ keyctl pipe 159771175 > evm.blob
	340
5395d312	341	Load an encrypted key "evm" from saved blob::
d00a1c72 MZ	342
	343	$ keyctl add encrypted evm "load `cat evm.blob`" @u
	344	831684262
	345
	346	$ keyctl print 831684262
4e561d38 RS	347	default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3
	348	82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
	349	24717c64 5972dcb82ab2dde83376d82b2e3c09ffc
d00a1c72	350
cd3bc044 YT	351	Instantiate an encrypted key "evm" using user-provided decrypted data::
cd3bc044 YT	352
5adedd42 NV	353	$ evmkey=$(dd if=/dev/urandom bs=1 count=32 \| xxd -c32 -p)
5adedd42 NV	354	$ keyctl add encrypted evm "new default user:kmk 32 $evmkey" @u
cd3bc044 YT	355	794890253
	356
	357	$ keyctl print 794890253
	358	default user:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382d
	359	bbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0247
	360	17c64 5972dcb82ab2dde83376d82b2e3c09ffc
	361
4e561d38	362	Other uses for trusted and encrypted keys, such as for disk and file encryption
b216685b	363	are anticipated. In particular the new format 'ecryptfs' has been defined
79a73d18	364	in order to use encrypted keys to mount an eCryptfs filesystem. More details
395cf969	365	about the usage can be found in the file
adf31eeb	366	``Documentation/security/keys/ecryptfs.rst``.
9db67581 DJ	367
	368	Another new format 'enc32' has been defined in order to support encrypted keys
	369	with payload size of 32 bytes. This will initially be used for nvdimm security
	370	but may expand to other usages that require 32 bytes payload.
f2219745 JB	371
	372
	373	TPM 2.0 ASN.1 Key Format
	374	------------------------
	375
	376	The TPM 2.0 ASN.1 key format is designed to be easily recognisable,
	377	even in binary form (fixing a problem we had with the TPM 1.2 ASN.1
	378	format) and to be extensible for additions like importable keys and
	379	policy::
	380
	381	TPMKey ::= SEQUENCE {
	382	type OBJECT IDENTIFIER
	383	emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
	384	parent INTEGER
	385	pubkey OCTET STRING
	386	privkey OCTET STRING
	387	}
	388
	389	type is what distinguishes the key even in binary form since the OID
	390	is provided by the TCG to be unique and thus forms a recognizable
	391	binary pattern at offset 3 in the key. The OIDs currently made
	392	available are::
	393
	394	2.23.133.10.1.3 TPM Loadable key. This is an asymmetric key (Usually
	395	RSA2048 or Elliptic Curve) which can be imported by a
	396	TPM2_Load() operation.
	397
	398	2.23.133.10.1.4 TPM Importable Key. This is an asymmetric key (Usually
	399	RSA2048 or Elliptic Curve) which can be imported by a
	400	TPM2_Import() operation.
	401
	402	2.23.133.10.1.5 TPM Sealed Data. This is a set of data (up to 128
	403	bytes) which is sealed by the TPM. It usually
	404	represents a symmetric key and must be unsealed before
	405	use.
	406
	407	The trusted key code only uses the TPM Sealed Data OID.
	408
	409	emptyAuth is true if the key has well known authorization "". If it
	410	is false or not present, the key requires an explicit authorization
	411	phrase. This is used by most user space consumers to decide whether
	412	to prompt for a password.
	413
	414	parent represents the parent key handle, either in the 0x81 MSO space,
	415	like 0x81000001 for the RSA primary storage key. Userspace programmes
	416	also support specifying the primary handle in the 0x40 MSO space. If
	417	this happens the Elliptic Curve variant of the primary key using the
	418	TCG defined template will be generated on the fly into a volatile
	419	object and used as the parent. The current kernel code only supports
	420	the 0x81 MSO form.
	421
	422	pubkey is the binary representation of TPM2B_PRIVATE excluding the
	423	initial TPM2B header, which can be reconstructed from the ASN.1 octet
	424	string length.
	425
	426	privkey is the binary representation of TPM2B_PUBLIC excluding the
	427	initial TPM2B header which can be reconstructed from the ASN.1 octed
	428	string length.