1089665e31
This commit adds attribute expansion statements to the policy
language allowing compiler defaults to be overridden.
Always expands an attribute example:
expandattribute { foo } true;
CIL example:
(expandtypeattribute (foo) true)
Never expand an attribute example:
expandattribute { bar } false;
CIL example:
(expandtypeattribute (bar) false)
Adding the annotations directly to policy was chosen over other
methods as it is consistent with how targeted runtime optimizations
are specified in other languages. For example, in C the "inline"
command.
Motivation
expandattribute true:
Android has been moving away from a monolithic policy binary to
a two part split policy representing the Android platform and the
underlying vendor-provided hardware interface. The goal is a stable
API allowing these two parts to be updated independently of each
other. Attributes provide an important mechanism for compatibility.
For example, when the vendor provides a HAL for the platform,
permissions needed by clients of the HAL can be granted to an
attribute. Clients need only be assigned the attribute and do not
need to be aware of the underlying types and permissions being
granted.
Inheriting permissions via attribute creates a convenient mechanism
for independence between vendor and platform policy, but results
in the creation of many attributes, and the potential for performance
issues when processes are clients of many HALs. [1] Annotating these
attributes for expansion at compile time allows us to retain the
compatibility benefits of using attributes without the performance
costs. [2]
expandattribute false:
Commit 0be23c3f15 added the capability to aggresively remove unused
attributes. This is generally useful as too many attributes assigned
to a type results in lengthy policy look up times when there is a
cache miss. However, removing attributes can also result in loss of
information used in external tests. On Android, we're considering
stripping neverallow rules from on-device policy. This is consistent
with the kernel policy binary which also did not contain neverallows.
Removing neverallow rules results in a 5-10% decrease in on-device
policy build and load and a policy size decrease of ~250k. Neverallow
rules are still asserted at build time and during device
certification (CTS). If neverallow rules are absent when secilc is
run, some attributes are being stripped from policy and neverallow
tests in CTS may be violated. [3] This change retains the aggressive
attribute stripping behavior but adds an override mechanism to
preserve attributes marked as necessary.
[1] https://github.com/SELinuxProject/cil/issues/9
[2] Annotating all HAL client attributes for expansion resulted in
system_server's dropping from 19 attributes to 8. Because these
attributes were not widely applied to other types, the final
policy size change was negligible.
[3] data_file_type and service_manager_type are stripped from AOSP
policy when using secilc's -G option. This impacts 11 neverallow
tests in CTS.
Test: Build and boot Marlin with all hal_*_client attributes marked
for expansion. Verify (using seinfo and sesearch) that permissions
are correctly expanded from attributes to types.
Test: Mark types being stripped by secilc with "preserve" and verify
that they are retained in policy and applied to the same types.
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
75 lines
2.7 KiB
C
75 lines
2.7 KiB
C
/* Functions used to define policy grammar components. */
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#ifndef _POLICY_DEFINE_H_
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#define _POLICY_DEFINE_H_
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/*
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* We need the following so we have a valid error return code in yacc
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* when we have a parse error for a conditional rule. We can't check
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* for NULL (ie 0) because that is a potentially valid return.
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*/
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#define COND_ERR ((avrule_t *)-1)
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#define TRUE 1
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#define FALSE 0
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avrule_t *define_cond_compute_type(int which);
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avrule_t *define_cond_pol_list(avrule_t *avlist, avrule_t *stmt);
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avrule_t *define_cond_te_avtab(int which);
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avrule_t *define_cond_filename_trans(void);
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cond_expr_t *define_cond_expr(uint32_t expr_type, void *arg1, void* arg2);
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int define_attrib(void);
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int define_attrib_role(void);
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int define_av_perms(int inherits);
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int define_bool_tunable(int is_tunable);
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int define_category(void);
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int define_class(void);
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int define_default_user(int which);
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int define_default_role(int which);
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int define_default_type(int which);
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int define_default_range(int which);
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int define_common_perms(void);
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int define_compute_type(int which);
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int define_conditional(cond_expr_t *expr, avrule_t *t_list, avrule_t *f_list );
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int define_constraint(constraint_expr_t *expr);
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int define_dominance(void);
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int define_fs_context(unsigned int major, unsigned int minor);
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int define_fs_use(int behavior);
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int define_genfs_context(int has_type);
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int define_initial_sid_context(void);
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int define_initial_sid(void);
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int define_ipv4_node_context(void);
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int define_ipv6_node_context(void);
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int define_level(void);
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int define_netif_context(void);
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int define_permissive(void);
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int define_polcap(void);
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int define_port_context(unsigned int low, unsigned int high);
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int define_pirq_context(unsigned int pirq);
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int define_iomem_context(uint64_t low, uint64_t high);
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int define_ioport_context(unsigned long low, unsigned long high);
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int define_pcidevice_context(unsigned long device);
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int define_devicetree_context(void);
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int define_range_trans(int class_specified);
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int define_role_allow(void);
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int define_role_trans(int class_specified);
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int define_role_types(void);
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int define_role_attr(void);
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int define_roleattribute(void);
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int define_filename_trans(void);
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int define_sens(void);
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int define_te_avtab(int which);
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int define_te_avtab_extended_perms(int which);
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int define_typealias(void);
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int define_typeattribute(void);
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int define_typebounds(void);
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int define_type(int alias);
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int define_user(void);
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int define_validatetrans(constraint_expr_t *expr);
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int expand_attrib(void);
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int insert_id(const char *id,int push);
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int insert_separator(int push);
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role_datum_t *define_role_dom(role_datum_t *r);
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role_datum_t *merge_roles_dom(role_datum_t *r1,role_datum_t *r2);
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uintptr_t define_cexpr(uint32_t expr_type, uintptr_t arg1, uintptr_t arg2);
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#endif /* _POLICY_DEFINE_H_ */
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