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>

diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
index 48457c6..276bdb6 100644 (file)
--- a/crypto/asymmetric_keys/restrict.c
+++ b/crypto/asymmetric_keys/restrict.c
@@ -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;
 

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
index 599429f..ec6e0d7 100644 (file)
--- a/security/integrity/Kconfig
+++ b/security/integrity/Kconfig
@@ -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

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index f2193c5..6f31ffe 100644 (file)
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -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