12b29f3455
Introduce SELinux support for deferred mapping of security contexts in
the SID table upon policy reload, and use this support for inode
security contexts when the context is not yet valid under the current
policy. Only processes with CAP_MAC_ADMIN + mac_admin permission in
policy can set undefined security contexts on inodes. Inodes with
such undefined contexts are treated as having the unlabeled context
until the context becomes valid upon a policy reload that defines the
context. Context invalidation upon policy reload also uses this
support to save the context information in the SID table and later
recover it upon a subsequent policy reload that defines the context
again.
This support is to enable package managers and similar programs to set
down file contexts unknown to the system policy at the time the file
is created in order to better support placing loadable policy modules
in packages and to support build systems that need to create images of
different distro releases with different policies w/o requiring all of
the contexts to be defined or legal in the build host policy.
With this patch applied, the following sequence is possible, although
in practice it is recommended that this permission only be allowed to
specific program domains such as the package manager.
# rmdir baz
# rm bar
# touch bar
# chcon -t foo_exec_t bar # foo_exec_t is not yet defined
chcon: failed to change context of `bar' to `system_u:object_r:foo_exec_t': Invalid argument
# mkdir -Z system_u:object_r:foo_exec_t baz
mkdir: failed to set default file creation context to `system_u:object_r:foo_exec_t': Invalid argument
# cat setundefined.te
policy_module(setundefined, 1.0)
require {
type unconfined_t;
type unlabeled_t;
}
files_type(unlabeled_t)
allow unconfined_t self:capability2 mac_admin;
# make -f /usr/share/selinux/devel/Makefile setundefined.pp
# semodule -i setundefined.pp
# chcon -t foo_exec_t bar # foo_exec_t is not yet defined
# mkdir -Z system_u:object_r:foo_exec_t baz
# ls -Zd bar baz
-rw-r--r-- root root system_u:object_r:unlabeled_t bar
drwxr-xr-x root root system_u:object_r:unlabeled_t baz
# cat foo.te
policy_module(foo, 1.0)
type foo_exec_t;
files_type(foo_exec_t)
# make -f /usr/share/selinux/devel/Makefile foo.pp
# semodule -i foo.pp # defines foo_exec_t
# ls -Zd bar baz
-rw-r--r-- root root user_u:object_r:foo_exec_t bar
drwxr-xr-x root root system_u:object_r:foo_exec_t baz
# semodule -r foo
# ls -Zd bar baz
-rw-r--r-- root root system_u:object_r:unlabeled_t bar
drwxr-xr-x root root system_u:object_r:unlabeled_t baz
# semodule -i foo.pp
# ls -Zd bar baz
-rw-r--r-- root root user_u:object_r:foo_exec_t bar
drwxr-xr-x root root system_u:object_r:foo_exec_t baz
# semodule -r setundefined foo
# chcon -t foo_exec_t bar # no longer defined and not allowed
chcon: failed to change context of `bar' to `system_u:object_r:foo_exec_t': Invalid argument
# rmdir baz
# mkdir -Z system_u:object_r:foo_exec_t baz
mkdir: failed to set default file creation context to `system_u:object_r:foo_exec_t': Invalid argument
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
/*
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* A security identifier table (sidtab) is a hash table
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* of security context structures indexed by SID value.
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*
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* Author : Stephen Smalley, <sds@epoch.ncsc.mil>
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*/
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#ifndef _SS_SIDTAB_H_
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#define _SS_SIDTAB_H_
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#include "context.h"
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struct sidtab_node {
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u32 sid; /* security identifier */
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struct context context; /* security context structure */
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struct sidtab_node *next;
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};
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#define SIDTAB_HASH_BITS 7
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#define SIDTAB_HASH_BUCKETS (1 << SIDTAB_HASH_BITS)
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#define SIDTAB_HASH_MASK (SIDTAB_HASH_BUCKETS-1)
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#define SIDTAB_SIZE SIDTAB_HASH_BUCKETS
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struct sidtab {
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struct sidtab_node **htable;
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unsigned int nel; /* number of elements */
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unsigned int next_sid; /* next SID to allocate */
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unsigned char shutdown;
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spinlock_t lock;
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};
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int sidtab_init(struct sidtab *s);
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int sidtab_insert(struct sidtab *s, u32 sid, struct context *context);
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struct context *sidtab_search(struct sidtab *s, u32 sid);
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struct context *sidtab_search_force(struct sidtab *s, u32 sid);
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int sidtab_map(struct sidtab *s,
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int (*apply) (u32 sid,
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struct context *context,
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void *args),
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void *args);
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int sidtab_context_to_sid(struct sidtab *s,
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struct context *context,
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u32 *sid);
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void sidtab_hash_eval(struct sidtab *h, char *tag);
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void sidtab_destroy(struct sidtab *s);
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void sidtab_set(struct sidtab *dst, struct sidtab *src);
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void sidtab_shutdown(struct sidtab *s);
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#endif /* _SS_SIDTAB_H_ */
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