Changes were made in this patchset based on David Howell's comments. The
major technical change was converting from the crypto hash to shash API.
The remaining changes are listed in the individual patch changelogs.
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...
(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 master-key-name keylen" ring
keyctl add encrypted name "load key-type:master-key-name keylen hex_blob" ring
keyctl update keyid "update master-key-name"
where 'key-type' is either 'trusted' or 'user'.
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.
Mimi Zohar
David Safford
Mimi Zohar (5):
lib: hex2bin converts ascii hexadecimal string to binary
tpm: add module_put wrapper
key: add tpm_send command
keys: add new trusted key-type
keys: add new key-type encrypted
Documentation/keys-trusted-encrypted.txt | 68 ++
drivers/char/tpm/tpm.c | 20 +-
drivers/char/tpm/tpm.h | 5 +
include/keys/encrypted-type.h | 29 +
include/keys/trusted-type.h | 31 +
include/linux/kernel.h | 1 +
include/linux/tpm.h | 4 +
lib/hexdump.c | 16 +
security/Kconfig | 31 +
security/keys/Makefile | 2 +
security/keys/encrypted_defined.c | 876 +++++++++++++++++++++++
security/keys/encrypted_defined.h | 56 ++
security/keys/trusted_defined.c | 1136 ++++++++++++++++++++++++++++++
security/keys/trusted_defined.h | 147 ++++
14 files changed, 2420 insertions(+), 2 deletions(-)
create mode 100644 Documentation/keys-trusted-encrypted.txt
create mode 100644 include/keys/encrypted-type.h
create mode 100644 include/keys/trusted-type.h
create mode 100644 security/keys/encrypted_defined.c
create mode 100644 security/keys/encrypted_defined.h
create mode 100644 security/keys/trusted_defined.c
create mode 100644 security/keys/trusted_defined.h
--
1.7.2.2
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