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authorLinus Torvalds <torvalds@linux-foundation.org>2022-05-24 13:16:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-05-24 13:16:50 -0700
commit7cf6a8a17f5b134b7e783c2d45c53298faef82a7 (patch)
treee5a6346abf5d9efbe49b91e6291349afcacfb7d3 /Documentation/security
parentMerge tag 'Smack-for-5.19' of https://github.com/cschaufler/smack-next (diff)
parentMAINTAINERS: add KEYS-TRUSTED-CAAM (diff)
downloadlinux-dev-7cf6a8a17f5b134b7e783c2d45c53298faef82a7.tar.xz
linux-dev-7cf6a8a17f5b134b7e783c2d45c53298faef82a7.zip
Merge tag 'tpmdd-next-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd
Pull tpm updates from Jarkko Sakkinen: - Tightened validation of key hashes for SYSTEM_BLACKLIST_HASH_LIST. An invalid hash format causes a compilation error. Previously, they got included to the kernel binary but were silently ignored at run-time. - Allow root user to append new hashes to the blacklist keyring. - Trusted keys backed with Cryptographic Acceleration and Assurance Module (CAAM), which part of some of the new NXP's SoC's. Now there is total three hardware backends for trusted keys: TPM, ARM TEE and CAAM. - A scattered set of fixes and small improvements for the TPM driver. * tag 'tpmdd-next-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd: MAINTAINERS: add KEYS-TRUSTED-CAAM doc: trusted-encrypted: describe new CAAM trust source KEYS: trusted: Introduce support for NXP CAAM-based trusted keys crypto: caam - add in-kernel interface for blob generator crypto: caam - determine whether CAAM supports blob encap/decap KEYS: trusted: allow use of kernel RNG for key material KEYS: trusted: allow use of TEE as backend without TCG_TPM support tpm: Add field upgrade mode support for Infineon TPM2 modules tpm: Fix buffer access in tpm2_get_tpm_pt() char: tpm: cr50_i2c: Suppress duplicated error message in .remove() tpm: cr50: Add new device/vendor ID 0x504a6666 tpm: Remove read16/read32/write32 calls from tpm_tis_phy_ops tpm: ibmvtpm: Correct the return value in tpm_ibmvtpm_probe() tpm/tpm_ftpm_tee: Return true/false (not 1/0) from bool functions certs: Explain the rationale to call panic() certs: Allow root user to append signed hashes to the blacklist keyring certs: Check that builtin blacklist hashes are valid certs: Make blacklist_vet_description() more strict certs: Factor out the blacklist hash creation tools/certs: Add print-cert-tbs-hash.sh
Diffstat (limited to 'Documentation/security')
-rw-r--r--Documentation/security/keys/trusted-encrypted.rst60
1 files changed, 51 insertions, 9 deletions
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index f614dad7de12..0bfb4c339748 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -35,6 +35,13 @@ safe.
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
@@ -46,6 +53,10 @@ safe.
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
@@ -63,6 +74,11 @@ safe.
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
@@ -74,10 +90,13 @@ safe.
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 TPM or TEE for a given
+ The strength and appropriateness of a particular trust source for a given
purpose must be assessed when using them to protect security-relevant data.
@@ -87,22 +106,32 @@ Key Generation
Trusted Keys
------------
-New keys are created from random numbers generated in the trust source. 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.
+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
+ * TPM: hardware device based RNG
- Strength of random numbers may vary from one device manufacturer to
- another.
+ 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
+ * 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
--------------
@@ -189,6 +218,19 @@ Usage::
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
--------------------