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integrity: machine keyring CA configuration 

Add machine keyring CA restriction options to control the type of
keys that may be added to it. The motivation is separation of
certificate signing from code signing keys. Subsquent work will
limit certificates being loaded into the IMA keyring to code
signing keys used for signature verification.

When no restrictions are selected, all Machine Owner Keys (MOK) are added
to the machine keyring.  When CONFIG_INTEGRITY_CA_MACHINE_KEYRING is
selected, the CA bit must be true.  Also the key usage must contain
keyCertSign, any other usage field may be set as well.

When CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX is selected, the CA bit must
be true. Also the key usage must contain keyCertSign and the
digitialSignature usage may not be set.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Eric Snowberg 2023-03-02 11:46:52 -05:00 committed by Jarkko Sakkinen
parent 76adb2fbc6
commit 099f26f22f
3 changed files with 30 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
crypto/asymmetric_keys/restrict.c
View File

@ -140,6 +140,8 @@ int restrict_link_by_ca(struct key *dest_keyring,
return -ENOKEY;
if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags))
return -ENOKEY;
if (!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX))
return 0;
if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags))
return -ENOKEY;

23
security/integrity/Kconfig
View File

@ -68,13 +68,34 @@ config INTEGRITY_MACHINE_KEYRING
depends on INTEGRITY_ASYMMETRIC_KEYS
depends on SYSTEM_BLACKLIST_KEYRING
depends on LOAD_UEFI_KEYS
depends on !IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
help
If set, provide a keyring to which Machine Owner Keys (MOK) may
be added. This keyring shall contain just MOK keys. Unlike keys
in the platform keyring, keys contained in the .machine keyring will
be trusted within the kernel.
config INTEGRITY_CA_MACHINE_KEYRING
bool "Enforce Machine Keyring CA Restrictions"
depends on INTEGRITY_MACHINE_KEYRING
default n
help
The .machine keyring can be configured to enforce CA restriction
on any key added to it. By default no restrictions are in place
and all Machine Owner Keys (MOK) are added to the machine keyring.
If enabled only CA keys are added to the machine keyring, all
other MOK keys load into the platform keyring.
config INTEGRITY_CA_MACHINE_KEYRING_MAX
bool "Only CA keys without DigitialSignature usage set"
depends on INTEGRITY_CA_MACHINE_KEYRING
default n
help
When selected, only load CA keys are loaded into the machine
keyring that contain the CA bit set along with the keyCertSign
Usage field. Keys containing the digitialSignature Usage field
will not be loaded. The remaining MOK keys are loaded into the
.platform keyring.
config LOAD_UEFI_KEYS
depends on INTEGRITY_PLATFORM_KEYRING
depends on EFI

8
security/integrity/digsig.c
View File

@ -132,7 +132,8 @@ int __init integrity_init_keyring(const unsigned int id)
| KEY_USR_READ | KEY_USR_SEARCH;
if (id == INTEGRITY_KEYRING_PLATFORM ||
id == INTEGRITY_KEYRING_MACHINE) {
(id == INTEGRITY_KEYRING_MACHINE &&
!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
restriction = NULL;
goto out;
}
@ -144,7 +145,10 @@ int __init integrity_init_keyring(const unsigned int id)
if (!restriction)
return -ENOMEM;
restriction->check = restrict_link_to_ima;
if (id == INTEGRITY_KEYRING_MACHINE)
restriction->check = restrict_link_by_ca;
else
restriction->check = restrict_link_to_ima;
/*
* MOK keys can only be added through a read-only runtime services