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d55201ce08
Here's a set of patches that changes how certificates/keys are determined to be trusted. That's currently a two-step process: (1) Up until recently, when an X.509 certificate was parsed - no matter the source - it was judged against the keys in .system_keyring, assuming those keys to be trusted if they have KEY_FLAG_TRUSTED set upon them. This has just been changed such that any key in the .ima_mok keyring, if configured, may also be used to judge the trustworthiness of a new certificate, whether or not the .ima_mok keyring is meant to be consulted for whatever process is being undertaken. If a certificate is determined to be trustworthy, KEY_FLAG_TRUSTED will be set upon a key it is loaded into (if it is loaded into one), no matter what the key is going to be loaded for. (2) If an X.509 certificate is loaded into a key, then that key - if KEY_FLAG_TRUSTED gets set upon it - can be linked into any keyring with KEY_FLAG_TRUSTED_ONLY set upon it. This was meant to be the system keyring only, but has been extended to various IMA keyrings. A user can at will link any key marked KEY_FLAG_TRUSTED into any keyring marked KEY_FLAG_TRUSTED_ONLY if the relevant permissions masks permit it. These patches change that: (1) Trust becomes a matter of consulting the ring of trusted keys supplied when the trust is evaluated only. (2) Every keyring can be supplied with its own manager function to restrict what may be added to that keyring. This is called whenever a key is to be linked into the keyring to guard against a key being created in one keyring and then linked across. This function is supplied with the keyring and the key type and payload[*] of the key being linked in for use in its evaluation. It is permitted to use other data also, such as the contents of other keyrings such as the system keyrings. [*] The type and payload are supplied instead of a key because as an optimisation this function may be called whilst creating a key and so may reject the proposed key between preparse and allocation. (3) A default manager function is provided that permits keys to be restricted to only asymmetric keys that are vouched for by the contents of the system keyring. A second manager function is provided that just rejects with EPERM. (4) A key allocation flag, KEY_ALLOC_BYPASS_RESTRICTION, is made available so that the kernel can initialise keyrings with keys that form the root of the trust relationship. (5) KEY_FLAG_TRUSTED and KEY_FLAG_TRUSTED_ONLY are removed, along with key_preparsed_payload::trusted. This change also makes it possible in future for userspace to create a private set of trusted keys and then to have it sealed by setting a manager function where the private set is wholly independent of the kernel's trust relationships. Further changes in the set involve extracting certain IMA special keyrings and making them generally global: (*) .system_keyring is renamed to .builtin_trusted_keys and remains read only. It carries only keys built in to the kernel. It may be where UEFI keys should be loaded - though that could better be the new secondary keyring (see below) or a separate UEFI keyring. (*) An optional secondary system keyring (called .secondary_trusted_keys) is added to replace the IMA MOK keyring. (*) Keys can be added to the secondary keyring by root if the keys can be vouched for by either ring of system keys. (*) Module signing and kexec only use .builtin_trusted_keys and do not use the new secondary keyring. (*) Config option SYSTEM_TRUSTED_KEYS now depends on ASYMMETRIC_KEY_TYPE as that's the only type currently permitted on the system keyrings. (*) A new config option, IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY, is provided to allow keys to be added to IMA keyrings, subject to the restriction that such keys are validly signed by a key already in the system keyrings. If this option is enabled, but secondary keyrings aren't, additions to the IMA keyrings will be restricted to signatures verifiable by keys in the builtin system keyring only. Signed-off-by: David Howells <dhowells@redhat.com> |
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.. | ||
encrypted-keys | ||
big_key.c | ||
compat.c | ||
dh.c | ||
gc.c | ||
internal.h | ||
Kconfig | ||
key.c | ||
keyctl.c | ||
keyring.c | ||
Makefile | ||
permission.c | ||
persistent.c | ||
proc.c | ||
process_keys.c | ||
request_key_auth.c | ||
request_key.c | ||
sysctl.c | ||
trusted.c | ||
trusted.h | ||
user_defined.c |