Commit b4650306 authored by Mimi Zohar's avatar Mimi Zohar
Browse files

certs: Only allow certs signed by keys on the builtin keyring 



Originally the secondary trusted keyring provided a keyring to which extra
keys may be added, provided those keys were not blacklisted and were
vouched for by a key built into the kernel or already in the secondary
trusted keyring.

On systems with the machine keyring configured, additional keys may also
be vouched for by a key on the machine keyring.

Prevent loading additional certificates directly onto the secondary
keyring, vouched for by keys on the machine keyring, yet allow these
certificates to be loaded onto other trusted keyrings.

Reviewed-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: default avatarMimi Zohar <zohar@linux.ibm.com>
parent 7b5c3086

certs/Kconfig

+15 −1
Original line number Diff line number Diff line
@@ -88,7 +88,21 @@ config SECONDARY_TRUSTED_KEYRING 
	help

	  If set, provide a keyring to which extra keys may be added, provided

	  those keys are not blacklisted and are vouched for by a key built

	  into the kernel or already in the secondary trusted keyring.

	  into the kernel, machine keyring (if configured), or already in the

	  secondary trusted keyring.



config SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN

	bool "Only allow additional certs signed by keys on the builtin trusted keyring"

	depends on SECONDARY_TRUSTED_KEYRING

	help

	  If set, only certificates signed by keys on the builtin trusted

	  keyring may be loaded onto the secondary trusted keyring.



	  Note: The machine keyring, if configured, will be linked to the

	  secondary keyring.  When enabling this option, it is recommended

	  to also configure INTEGRITY_CA_MACHINE_KEYRING_MAX to prevent

	  linking code signing keys with imputed trust to the secondary

	  trusted keyring.



config SYSTEM_BLACKLIST_KEYRING

	bool "Provide system-wide ring of blacklisted keys"

crypto/asymmetric_keys/restrict.c

+4 −0
Original line number Diff line number Diff line
@@ -102,6 +102,10 @@ int restrict_link_by_signature(struct key *dest_keyring, 


	if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))

		ret = -ENOKEY;

	else if (IS_BUILTIN(CONFIG_SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN) &&

		 !strcmp(dest_keyring->description, ".secondary_trusted_keys") &&

		 !test_bit(KEY_FLAG_BUILTIN, &key->flags))

		ret = -ENOKEY;

	else

		ret = verify_signature(key, sig);

	key_put(key);