lockdown: Enforce module signatures if the kernel is locked down

If the kernel is locked down, require that all modules have valid
signatures that we can verify.

I have adjusted the errors generate

lockdown: Enforce module signatures if the kernel is locked down

If the kernel is locked down, require that all modules have valid
signatures that we can verify.

I have adjusted the errors generated:

(1) If there's no signature (ENODATA) or we can't check it (ENOPKG,
ENOKEY), then:

(a) If signatures are enforced then EKEYREJECTED is returned.

(b) If there's no signature or we can't check it, but the kernel is
locked down then EPERM is returned (this is then consistent with
other lockdown cases).

(2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails
the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we
return the error we got.

Note that the X.509 code doesn't check for key expiry as the RTC might not
be valid or might not have been transferred to the kernel's clock yet.

[Modified by Matthew Garrett to remove the IMA integration. This will
be replaced with integration with the IMA architecture policy
patchset.]

Signed-off-by: David Howells <[email protected]>
Signed-off-by: Matthew Garrett <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Jessica Yu <[email protected]>
Signed-off-by: James Morris <[email protected]>

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security: Add a static lockdown policy LSM

While existing LSMs can be extended to handle lockdown policy,
distributions generally want to be able to apply a straightforward
static policy. This patch

security: Add a static lockdown policy LSM

While existing LSMs can be extended to handle lockdown policy,
distributions generally want to be able to apply a straightforward
static policy. This patch adds a simple LSM that can be configured to
reject either integrity or all lockdown queries, and can be configured
at runtime (through securityfs), boot time (via a kernel parameter) or
build time (via a kconfig option). Based on initial code by David
Howells.

Signed-off-by: Matthew Garrett <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: David Howells <[email protected]>
Signed-off-by: James Morris <[email protected]>

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