io_uring and userns mediation are encoding permissions on the class
byte. This is a mistake that should never have been allowed.
With the addition of rule priorities the class byte mediates rule,
that ensure the kernel can determine a class is being mediated is
given the highest priority possible, to ensure class mediation can not
be removed by a deny rule. See
61b7568e1 ("parser: bug fix mediates_X stub rules.")
for details.
Unfortunately this breaks rule classes that encode permissions on the
class byte, because those rules will always have a lower priority and
the class mediates rule will always be selected over them resulting in
only the class mediates permission being on the rule class state.
Fix this by adding the mediaties class rules for these rule classes
with the lowest priority possible. This means that any rule mediating
the class will wipe out the mediates class rule. So add a new mediates
class rule at the same priority, as the rule being added.
This is a naive implementation and does result in more mediates rules
being added than necessary. The rule class could keep track of the
highest priority rule that had been added, and use that to reduce the
number of mediates rules it adds for the class.
Technically we could also get away with not adding the rules for allow
rules, as the kernel doesn't actually check the encoded permission but
whether the class state is not the trap state. But it is required with
deny rules to ensure the deny rule doesn't result in permissions being
removed from the class, resulting in the kernel thinking it is
unmediated. We also want to ensure that mediation is encoded for other
rule types like prompt, and in the future the kernel could check the
permission so we do want to guarantee that the class state has the
MAY_READ permission on it.
Note: there is another set of classes (file, mqueue, dbus, ...) which
encodes a default rule permission as
class .* <perm>
this encoding is unfortunate in that it will also add the permission
to the class byte, but also sets up following states with the permission.
thankfully, this accespt anything, including nothing generally isn't
valid in the nothing case (eg. a file without any absolute name). For
this set of classes, the high priority mediates rule just ensures
that the null match case does not have permission.
Fixes: 61b7568e1 parser: bug fix mediates_X stub rules.
Signed-off-by: John Johansen <john.johansen@canonical.com>
Moving apply_and_clear_deny() before the first minimization pass, which
was necessary to propperly support building accept information for
older none extended permission dfas, allows us to also get rid of doing a
second minimization pass if we want to force clearing explicit deny
info from extended permission tables.
Signed-off-by: John Johansen <john.johansen@canonical.com>
There are two distinct declarations of perms_t.
rule.h: typedef uint32_t perms_t
hfa.h: class perms_t
these definitions clash when the front end and backend share more info.
To avoid this rename rule.h to perm32_t, and move the definition into
perms.h and use it in struct aa_perms.
Signed-off-by: John Johansen <john.johansen@canonical.com>
Extend the policy syntax to have a rule that allows specifying all
permissions for all rule types.
allow all,
This is useful for making blacklist based policy, but can also be
useful when combined with other rule prefixes, eg. to add audit
to all rules.
audit access all,
Signed-off-by: John Johansen <john.johansen@canonical.com>
Add the ability to control whether rule merging is done.
TODO: in the furture cleanup display of flags split accross two tables
Signed-off-by: John Johansen <john.johansen@canonical.com>
In preparation for more flags (not all of the backend dfa based),
rework the optimization and dump flag handling which has been exclusively
around the dfa up to this point.
- split dfa control and dump flags into separate fields. This gives more
room for new flags in the existing DFA set
- rename DFA_DUMP, and DFA_CONTROL to CONTROL_DFA and DUMP_DFA as
this will provide more uniform naming for none dfa flags
- group dump and control flags into a structure so they can be passed
together.
Signed-off-by: John Johansen <john.johansen@canonical.com>
