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+ 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 symmetic 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 Trusted Platform Module (TPM) chip 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.
+
+Trusted Keys use a TPM both to generate and to seal the keys. Keys are sealed
+under a 2048 bit RSA key in the TPM, and 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.
+
+By default, trusted keys are sealed under the SRK, which has the default
+authorization value (20 zeros). This can be set at takeownership time with the
+trouser's utility: "tpm_takeownership -u -z".
+
+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 default 0x40000000 (SRK)
+ 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)
+ 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)
+
+"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.
+
+Encrypted keys do not depend on a TPM, and are faster, as they use AES for
+encryption/decryption. New keys are created from kernel generated random
+numbers, 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:
+ keyctl add encrypted name "new key-type:master-key-name keylen" ring
+ keyctl add encrypted name "load hex_blob" ring
+ keyctl update keyid "update key-type:master-key-name"
+
+where 'key-type' is either 'trusted' or 'user'.
+
+Examples of trusted and encrypted key usage:
+
+Create and save a trusted key named "kmk" of length 32 bytes:
+
+ $ 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 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
+
+Create and save an encrypted key "evm" using the above trusted key "kmk":
+
+ $ keyctl add encrypted evm "new trusted:kmk 32" @u
+ 159771175
+
+ $ keyctl print 159771175
+ trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382dbbc55
+ be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e024717c64
+ 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
+ trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382dbbc55
+ be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e024717c64
+ 5972dcb82ab2dde83376d82b2e3c09ffc
+
+
+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 specific boot PCR
+values, protects against boot and offline attacks. Other uses for trusted and
+encrypted keys, such as for disk and file encryption are anticipated.

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