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af63f4193f
As systemd ramps up enabling NNP (NoNewPrivileges) for system services,
it is increasingly breaking SELinux domain transitions for those services
and their descendants. systemd enables NNP not only for services whose
unit files explicitly specify NoNewPrivileges=yes but also for services
whose unit files specify any of the following options in combination with
running without CAP_SYS_ADMIN (e.g. specifying User= or a
CapabilityBoundingSet= without CAP_SYS_ADMIN): SystemCallFilter=,
SystemCallArchitectures=, RestrictAddressFamilies=, RestrictNamespaces=,
PrivateDevices=, ProtectKernelTunables=, ProtectKernelModules=,
MemoryDenyWriteExecute=, or RestrictRealtime= as per the systemd.exec(5)
man page.
The end result is bad for the security of both SELinux-disabled and
SELinux-enabled systems. Packagers have to turn off these
options in the unit files to preserve SELinux domain transitions. For
users who choose to disable SELinux, this means that they miss out on
at least having the systemd-supported protections. For users who keep
SELinux enabled, they may still be missing out on some protections
because it isn't necessarily guaranteed that the SELinux policy for
that service provides the same protections in all cases.
commit 7b0d0b40cd ("selinux: Permit bounded transitions under
NO_NEW_PRIVS or NOSUID.") allowed bounded transitions under NNP in
order to support limited usage for sandboxing programs. However,
defining typebounds for all of the affected service domains
is impractical to implement in policy, since typebounds requires us
to ensure that each domain is allowed everything all of its descendant
domains are allowed, and this has to be repeated for the entire chain
of domain transitions. There is no way to clone all allow rules from
descendants to their ancestors in policy currently, and doing so would
be undesirable even if it were practical, as it requires leaking
permissions to objects and operations into ancestor domains that could
weaken their own security in order to allow them to the descendants
(e.g. if a descendant requires execmem permission, then so do all of
its ancestors; if a descendant requires execute permission to a file,
then so do all of its ancestors; if a descendant requires read to a
symbolic link or temporary file, then so do all of its ancestors...).
SELinux domains are intentionally not hierarchical / bounded in this
manner normally, and making them so would undermine their protections
and least privilege.
We have long had a similar tension with SELinux transitions and nosuid
mounts, albeit not as severe. Users often have had to choose between
retaining nosuid on a mount and allowing SELinux domain transitions on
files within those mounts. This likewise leads to unfortunate tradeoffs
in security.
Decouple NNP/nosuid from SELinux transitions, so that we don't have to
make a choice between them. Introduce a nnp_nosuid_transition policy
capability that enables transitions under NNP/nosuid to be based on
a permission (nnp_transition for NNP; nosuid_transition for nosuid)
between the old and new contexts in addition to the current support
for bounded transitions. Domain transitions can then be allowed in
policy without requiring the parent to be a strict superset of all of
its children.
With this change, systemd unit files can be left unmodified from upstream.
SELinux-disabled and SELinux-enabled users will benefit from retaining any
of the systemd-provided protections. SELinux policy will only need to
be adapted to enable the new policy capability and to allow the
new permissions between domain pairs as appropriate.
NB: Allowing nnp_transition between two contexts opens up the potential
for the old context to subvert the new context by installing seccomp
filters before the execve. Allowing nosuid_transition between two contexts
opens up the potential for a context transition to occur on a file from
an untrusted filesystem (e.g. removable media or remote filesystem). Use
with care.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
281 lines
8.3 KiB
C
281 lines
8.3 KiB
C
/*
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* Security server interface.
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*
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* Author : Stephen Smalley, <sds@epoch.ncsc.mil>
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*
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*/
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#ifndef _SELINUX_SECURITY_H_
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#define _SELINUX_SECURITY_H_
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#include <linux/compiler.h>
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#include <linux/dcache.h>
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#include <linux/magic.h>
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#include <linux/types.h>
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#include "flask.h"
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#define SECSID_NULL 0x00000000 /* unspecified SID */
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#define SECSID_WILD 0xffffffff /* wildcard SID */
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#define SECCLASS_NULL 0x0000 /* no class */
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/* Identify specific policy version changes */
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#define POLICYDB_VERSION_BASE 15
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#define POLICYDB_VERSION_BOOL 16
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#define POLICYDB_VERSION_IPV6 17
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#define POLICYDB_VERSION_NLCLASS 18
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#define POLICYDB_VERSION_VALIDATETRANS 19
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#define POLICYDB_VERSION_MLS 19
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#define POLICYDB_VERSION_AVTAB 20
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#define POLICYDB_VERSION_RANGETRANS 21
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#define POLICYDB_VERSION_POLCAP 22
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#define POLICYDB_VERSION_PERMISSIVE 23
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#define POLICYDB_VERSION_BOUNDARY 24
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#define POLICYDB_VERSION_FILENAME_TRANS 25
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#define POLICYDB_VERSION_ROLETRANS 26
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#define POLICYDB_VERSION_NEW_OBJECT_DEFAULTS 27
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#define POLICYDB_VERSION_DEFAULT_TYPE 28
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#define POLICYDB_VERSION_CONSTRAINT_NAMES 29
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#define POLICYDB_VERSION_XPERMS_IOCTL 30
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#define POLICYDB_VERSION_INFINIBAND 31
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/* Range of policy versions we understand*/
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#define POLICYDB_VERSION_MIN POLICYDB_VERSION_BASE
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#define POLICYDB_VERSION_MAX POLICYDB_VERSION_INFINIBAND
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/* Mask for just the mount related flags */
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#define SE_MNTMASK 0x0f
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/* Super block security struct flags for mount options */
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/* BE CAREFUL, these need to be the low order bits for selinux_get_mnt_opts */
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#define CONTEXT_MNT 0x01
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#define FSCONTEXT_MNT 0x02
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#define ROOTCONTEXT_MNT 0x04
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#define DEFCONTEXT_MNT 0x08
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#define SBLABEL_MNT 0x10
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/* Non-mount related flags */
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#define SE_SBINITIALIZED 0x0100
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#define SE_SBPROC 0x0200
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#define SE_SBGENFS 0x0400
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#define CONTEXT_STR "context="
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#define FSCONTEXT_STR "fscontext="
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#define ROOTCONTEXT_STR "rootcontext="
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#define DEFCONTEXT_STR "defcontext="
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#define LABELSUPP_STR "seclabel"
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struct netlbl_lsm_secattr;
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extern int selinux_enabled;
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/* Policy capabilities */
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enum {
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POLICYDB_CAPABILITY_NETPEER,
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POLICYDB_CAPABILITY_OPENPERM,
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POLICYDB_CAPABILITY_EXTSOCKCLASS,
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POLICYDB_CAPABILITY_ALWAYSNETWORK,
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POLICYDB_CAPABILITY_CGROUPSECLABEL,
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POLICYDB_CAPABILITY_NNP_NOSUID_TRANSITION,
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__POLICYDB_CAPABILITY_MAX
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};
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#define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
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extern char *selinux_policycap_names[__POLICYDB_CAPABILITY_MAX];
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extern int selinux_policycap_netpeer;
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extern int selinux_policycap_openperm;
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extern int selinux_policycap_extsockclass;
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extern int selinux_policycap_alwaysnetwork;
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extern int selinux_policycap_cgroupseclabel;
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extern int selinux_policycap_nnp_nosuid_transition;
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/*
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* type_datum properties
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* available at the kernel policy version >= POLICYDB_VERSION_BOUNDARY
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*/
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#define TYPEDATUM_PROPERTY_PRIMARY 0x0001
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#define TYPEDATUM_PROPERTY_ATTRIBUTE 0x0002
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/* limitation of boundary depth */
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#define POLICYDB_BOUNDS_MAXDEPTH 4
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int security_mls_enabled(void);
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int security_load_policy(void *data, size_t len);
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int security_read_policy(void **data, size_t *len);
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size_t security_policydb_len(void);
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int security_policycap_supported(unsigned int req_cap);
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#define SEL_VEC_MAX 32
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struct av_decision {
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u32 allowed;
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u32 auditallow;
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u32 auditdeny;
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u32 seqno;
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u32 flags;
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};
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#define XPERMS_ALLOWED 1
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#define XPERMS_AUDITALLOW 2
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#define XPERMS_DONTAUDIT 4
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#define security_xperm_set(perms, x) (perms[x >> 5] |= 1 << (x & 0x1f))
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#define security_xperm_test(perms, x) (1 & (perms[x >> 5] >> (x & 0x1f)))
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struct extended_perms_data {
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u32 p[8];
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};
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struct extended_perms_decision {
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u8 used;
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u8 driver;
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struct extended_perms_data *allowed;
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struct extended_perms_data *auditallow;
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struct extended_perms_data *dontaudit;
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};
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struct extended_perms {
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u16 len; /* length associated decision chain */
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struct extended_perms_data drivers; /* flag drivers that are used */
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};
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/* definitions of av_decision.flags */
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#define AVD_FLAGS_PERMISSIVE 0x0001
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void security_compute_av(u32 ssid, u32 tsid,
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u16 tclass, struct av_decision *avd,
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struct extended_perms *xperms);
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void security_compute_xperms_decision(u32 ssid, u32 tsid, u16 tclass,
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u8 driver, struct extended_perms_decision *xpermd);
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void security_compute_av_user(u32 ssid, u32 tsid,
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u16 tclass, struct av_decision *avd);
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int security_transition_sid(u32 ssid, u32 tsid, u16 tclass,
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const struct qstr *qstr, u32 *out_sid);
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int security_transition_sid_user(u32 ssid, u32 tsid, u16 tclass,
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const char *objname, u32 *out_sid);
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int security_member_sid(u32 ssid, u32 tsid,
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u16 tclass, u32 *out_sid);
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int security_change_sid(u32 ssid, u32 tsid,
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u16 tclass, u32 *out_sid);
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int security_sid_to_context(u32 sid, char **scontext,
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u32 *scontext_len);
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int security_sid_to_context_force(u32 sid, char **scontext, u32 *scontext_len);
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int security_context_to_sid(const char *scontext, u32 scontext_len,
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u32 *out_sid, gfp_t gfp);
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int security_context_str_to_sid(const char *scontext, u32 *out_sid, gfp_t gfp);
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int security_context_to_sid_default(const char *scontext, u32 scontext_len,
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u32 *out_sid, u32 def_sid, gfp_t gfp_flags);
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int security_context_to_sid_force(const char *scontext, u32 scontext_len,
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u32 *sid);
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int security_get_user_sids(u32 callsid, char *username,
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u32 **sids, u32 *nel);
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int security_port_sid(u8 protocol, u16 port, u32 *out_sid);
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int security_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *out_sid);
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int security_ib_endport_sid(const char *dev_name, u8 port_num, u32 *out_sid);
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int security_netif_sid(char *name, u32 *if_sid);
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int security_node_sid(u16 domain, void *addr, u32 addrlen,
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u32 *out_sid);
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int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
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u16 tclass);
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int security_validate_transition_user(u32 oldsid, u32 newsid, u32 tasksid,
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u16 tclass);
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int security_bounded_transition(u32 oldsid, u32 newsid);
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int security_sid_mls_copy(u32 sid, u32 mls_sid, u32 *new_sid);
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int security_net_peersid_resolve(u32 nlbl_sid, u32 nlbl_type,
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u32 xfrm_sid,
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u32 *peer_sid);
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int security_get_classes(char ***classes, int *nclasses);
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int security_get_permissions(char *class, char ***perms, int *nperms);
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int security_get_reject_unknown(void);
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int security_get_allow_unknown(void);
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#define SECURITY_FS_USE_XATTR 1 /* use xattr */
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#define SECURITY_FS_USE_TRANS 2 /* use transition SIDs, e.g. devpts/tmpfs */
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#define SECURITY_FS_USE_TASK 3 /* use task SIDs, e.g. pipefs/sockfs */
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#define SECURITY_FS_USE_GENFS 4 /* use the genfs support */
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#define SECURITY_FS_USE_NONE 5 /* no labeling support */
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#define SECURITY_FS_USE_MNTPOINT 6 /* use mountpoint labeling */
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#define SECURITY_FS_USE_NATIVE 7 /* use native label support */
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#define SECURITY_FS_USE_MAX 7 /* Highest SECURITY_FS_USE_XXX */
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int security_fs_use(struct super_block *sb);
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int security_genfs_sid(const char *fstype, char *name, u16 sclass,
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u32 *sid);
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#ifdef CONFIG_NETLABEL
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int security_netlbl_secattr_to_sid(struct netlbl_lsm_secattr *secattr,
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u32 *sid);
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int security_netlbl_sid_to_secattr(u32 sid,
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struct netlbl_lsm_secattr *secattr);
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#else
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static inline int security_netlbl_secattr_to_sid(
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struct netlbl_lsm_secattr *secattr,
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u32 *sid)
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{
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return -EIDRM;
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}
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static inline int security_netlbl_sid_to_secattr(u32 sid,
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struct netlbl_lsm_secattr *secattr)
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{
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return -ENOENT;
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}
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#endif /* CONFIG_NETLABEL */
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const char *security_get_initial_sid_context(u32 sid);
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/*
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* status notifier using mmap interface
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*/
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extern struct page *selinux_kernel_status_page(void);
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#define SELINUX_KERNEL_STATUS_VERSION 1
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struct selinux_kernel_status {
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u32 version; /* version number of thie structure */
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u32 sequence; /* sequence number of seqlock logic */
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u32 enforcing; /* current setting of enforcing mode */
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u32 policyload; /* times of policy reloaded */
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u32 deny_unknown; /* current setting of deny_unknown */
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/*
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* The version > 0 supports above members.
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*/
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} __packed;
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extern void selinux_status_update_setenforce(int enforcing);
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extern void selinux_status_update_policyload(int seqno);
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extern void selinux_complete_init(void);
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extern int selinux_disable(void);
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extern void exit_sel_fs(void);
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extern struct path selinux_null;
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extern struct vfsmount *selinuxfs_mount;
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extern void selnl_notify_setenforce(int val);
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extern void selnl_notify_policyload(u32 seqno);
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extern int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm);
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#endif /* _SELINUX_SECURITY_H_ */
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