apparmor: add the ability to mediate signals
Add signal mediation where the signal can be mediated based on the
signal, direction, or the label or the peer/target. The signal perms
are verified on a cross check to ensure policy consistency in the case
of incremental policy load/replacement.
The optimization of skipping the cross check when policy is guaranteed
to be consistent (single compile unit) remains to be done.
policy rules have the form of
SIGNAL_RULE = [ QUALIFIERS ] 'signal' [ SIGNAL ACCESS PERMISSIONS ]
[ SIGNAL SET ] [ SIGNAL PEER ]
SIGNAL ACCESS PERMISSIONS = SIGNAL ACCESS | SIGNAL ACCESS LIST
SIGNAL ACCESS LIST = '(' Comma or space separated list of SIGNAL
ACCESS ')'
SIGNAL ACCESS = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'send' |
'receive' )
SIGNAL SET = 'set' '=' '(' SIGNAL LIST ')'
SIGNAL LIST = Comma or space separated list of SIGNALS
SIGNALS = ( 'hup' | 'int' | 'quit' | 'ill' | 'trap' | 'abrt' |
'bus' | 'fpe' | 'kill' | 'usr1' | 'segv' | 'usr2' |
'pipe' | 'alrm' | 'term' | 'stkflt' | 'chld' | 'cont' |
'stop' | 'stp' | 'ttin' | 'ttou' | 'urg' | 'xcpu' |
'xfsz' | 'vtalrm' | 'prof' | 'winch' | 'io' | 'pwr' |
'sys' | 'emt' | 'exists' | 'rtmin+0' ... 'rtmin+32'
)
SIGNAL PEER = 'peer' '=' AARE
eg.
signal, # allow all signals
signal send set=(hup, kill) peer=foo,
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
This commit is contained in:
John Johansen
Родитель
c5561700c9
Коммит
cd1dbf76b2
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@ -32,6 +32,7 @@
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#include "include/audit.h"
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#include "include/context.h"
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#include "include/crypto.h"
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#include "include/ipc.h"
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#include "include/policy_ns.h"
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#include "include/label.h"
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#include "include/policy.h"
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@ -2129,6 +2130,11 @@ static struct aa_sfs_entry aa_sfs_entry_ptrace[] = {
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{ }
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};
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static struct aa_sfs_entry aa_sfs_entry_signal[] = {
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AA_SFS_FILE_STRING("mask", AA_SFS_SIG_MASK),
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{ }
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};
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static struct aa_sfs_entry aa_sfs_entry_domain[] = {
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AA_SFS_FILE_BOOLEAN("change_hat", 1),
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AA_SFS_FILE_BOOLEAN("change_hatv", 1),
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@ -2179,6 +2185,7 @@ static struct aa_sfs_entry aa_sfs_entry_features[] = {
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AA_SFS_DIR("rlimit", aa_sfs_entry_rlimit),
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AA_SFS_DIR("caps", aa_sfs_entry_caps),
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AA_SFS_DIR("ptrace", aa_sfs_entry_ptrace),
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AA_SFS_DIR("signal", aa_sfs_entry_signal),
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AA_SFS_DIR("query", aa_sfs_entry_query),
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{ }
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};
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@ -28,6 +28,7 @@
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#define AA_CLASS_RLIMITS 5
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#define AA_CLASS_DOMAIN 6
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#define AA_CLASS_PTRACE 9
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#define AA_CLASS_SIGNAL 10
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#define AA_CLASS_LABEL 16
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#define AA_CLASS_LAST AA_CLASS_LABEL
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@ -86,6 +86,7 @@ enum audit_type {
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#define OP_SHUTDOWN "socket_shutdown"
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#define OP_PTRACE "ptrace"
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#define OP_SIGNAL "signal"
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#define OP_EXEC "exec"
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@ -126,6 +127,7 @@ struct apparmor_audit_data {
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long pos;
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const char *ns;
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} iface;
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int signal;
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struct {
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int rlim;
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unsigned long max;
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@ -27,8 +27,14 @@ struct aa_profile;
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#define AA_PTRACE_PERM_MASK (AA_PTRACE_READ | AA_PTRACE_TRACE | \
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AA_MAY_BE_READ | AA_MAY_BE_TRACED)
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#define AA_SIGNAL_PERM_MASK (MAY_READ | MAY_WRITE)
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#define AA_SFS_SIG_MASK "hup int quit ill trap abrt bus fpe kill usr1 " \
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"segv usr2 pipe alrm term stkflt chld cont stop stp ttin ttou urg " \
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"xcpu xfsz vtalrm prof winch io pwr sys emt lost"
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int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee,
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u32 request);
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int aa_may_signal(struct aa_label *sender, struct aa_label *target, int sig);
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#endif /* __AA_IPC_H */
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@ -0,0 +1,95 @@
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#include <linux/signal.h>
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#define SIGUNKNOWN 0
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#define MAXMAPPED_SIG 35
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/* provide a mapping of arch signal to internal signal # for mediation
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* those that are always an alias SIGCLD for SIGCLHD and SIGPOLL for SIGIO
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* map to the same entry those that may/or may not get a separate entry
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*/
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static const int sig_map[MAXMAPPED_SIG] = {
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[0] = MAXMAPPED_SIG, /* existence test */
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[SIGHUP] = 1,
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[SIGINT] = 2,
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[SIGQUIT] = 3,
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[SIGILL] = 4,
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[SIGTRAP] = 5, /* -, 5, - */
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[SIGABRT] = 6, /* SIGIOT: -, 6, - */
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[SIGBUS] = 7, /* 10, 7, 10 */
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[SIGFPE] = 8,
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[SIGKILL] = 9,
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[SIGUSR1] = 10, /* 30, 10, 16 */
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[SIGSEGV] = 11,
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[SIGUSR2] = 12, /* 31, 12, 17 */
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[SIGPIPE] = 13,
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[SIGALRM] = 14,
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[SIGTERM] = 15,
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[SIGSTKFLT] = 16, /* -, 16, - */
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[SIGCHLD] = 17, /* 20, 17, 18. SIGCHLD -, -, 18 */
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[SIGCONT] = 18, /* 19, 18, 25 */
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[SIGSTOP] = 19, /* 17, 19, 23 */
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[SIGTSTP] = 20, /* 18, 20, 24 */
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[SIGTTIN] = 21, /* 21, 21, 26 */
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[SIGTTOU] = 22, /* 22, 22, 27 */
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[SIGURG] = 23, /* 16, 23, 21 */
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[SIGXCPU] = 24, /* 24, 24, 30 */
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[SIGXFSZ] = 25, /* 25, 25, 31 */
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[SIGVTALRM] = 26, /* 26, 26, 28 */
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[SIGPROF] = 27, /* 27, 27, 29 */
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[SIGWINCH] = 28, /* 28, 28, 20 */
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[SIGIO] = 29, /* SIGPOLL: 23, 29, 22 */
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[SIGPWR] = 30, /* 29, 30, 19. SIGINFO 29, -, - */
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#ifdef SIGSYS
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[SIGSYS] = 31, /* 12, 31, 12. often SIG LOST/UNUSED */
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#endif
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#ifdef SIGEMT
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[SIGEMT] = 32, /* 7, - , 7 */
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#endif
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#if defined(SIGLOST) && SIGPWR != SIGLOST /* sparc */
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[SIGLOST] = 33, /* unused on Linux */
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#endif
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#if defined(SIGLOST) && defined(SIGSYS) && SIGLOST != SIGSYS
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[SIGUNUSED] = 34, /* -, 31, - */
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#endif
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};
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/* this table is ordered post sig_map[sig] mapping */
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static const char *const sig_names[MAXMAPPED_SIG + 1] = {
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"unknown",
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"hup",
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"int",
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"quit",
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"ill",
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"trap",
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"abrt",
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"bus",
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"fpe",
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"kill",
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"usr1",
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"segv",
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"usr2",
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"pipe",
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"alrm",
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"term",
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"stkflt",
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"chld",
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"cont",
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"stop",
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"stp",
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"ttin",
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"ttou",
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"urg",
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"xcpu",
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"xfsz",
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"vtalrm",
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"prof",
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"winch",
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"io",
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"pwr",
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"sys",
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"emt",
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"lost",
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"unused",
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"exists", /* always last existence test mapped to MAXMAPPED_SIG */
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};
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@ -20,6 +20,7 @@
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#include "include/context.h"
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#include "include/policy.h"
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#include "include/ipc.h"
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#include "include/sig_names.h"
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/**
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* audit_ptrace_mask - convert mask to permission string
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@ -121,3 +122,101 @@ int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee,
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}
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static inline int map_signal_num(int sig)
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{
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if (sig > SIGRTMAX)
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return SIGUNKNOWN;
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else if (sig >= SIGRTMIN)
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return sig - SIGRTMIN + 128; /* rt sigs mapped to 128 */
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else if (sig <= MAXMAPPED_SIG)
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return sig_map[sig];
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return SIGUNKNOWN;
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}
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/**
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* audit_file_mask - convert mask to permission string
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* @buffer: buffer to write string to (NOT NULL)
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* @mask: permission mask to convert
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*/
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static void audit_signal_mask(struct audit_buffer *ab, u32 mask)
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{
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if (mask & MAY_READ)
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audit_log_string(ab, "receive");
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if (mask & MAY_WRITE)
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audit_log_string(ab, "send");
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}
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/**
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* audit_cb - call back for signal specific audit fields
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* @ab: audit_buffer (NOT NULL)
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* @va: audit struct to audit values of (NOT NULL)
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*/
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static void audit_signal_cb(struct audit_buffer *ab, void *va)
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{
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struct common_audit_data *sa = va;
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if (aad(sa)->request & AA_SIGNAL_PERM_MASK) {
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audit_log_format(ab, " requested_mask=");
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audit_signal_mask(ab, aad(sa)->request);
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if (aad(sa)->denied & AA_SIGNAL_PERM_MASK) {
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audit_log_format(ab, " denied_mask=");
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audit_signal_mask(ab, aad(sa)->denied);
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}
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}
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if (aad(sa)->signal <= MAXMAPPED_SIG)
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audit_log_format(ab, " signal=%s", sig_names[aad(sa)->signal]);
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else
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audit_log_format(ab, " signal=rtmin+%d",
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aad(sa)->signal - 128);
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audit_log_format(ab, " peer=");
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aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
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FLAGS_NONE, GFP_ATOMIC);
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}
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/* TODO: update to handle compound name&name2, conditionals */
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static void profile_match_signal(struct aa_profile *profile, const char *label,
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int signal, struct aa_perms *perms)
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{
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unsigned int state;
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/* TODO: secondary cache check <profile, profile, perm> */
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state = aa_dfa_next(profile->policy.dfa,
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profile->policy.start[AA_CLASS_SIGNAL],
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signal);
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state = aa_dfa_match(profile->policy.dfa, state, label);
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aa_compute_perms(profile->policy.dfa, state, perms);
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}
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static int profile_signal_perm(struct aa_profile *profile,
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struct aa_profile *peer, u32 request,
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struct common_audit_data *sa)
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{
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struct aa_perms perms;
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if (profile_unconfined(profile) ||
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!PROFILE_MEDIATES(profile, AA_CLASS_SIGNAL))
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return 0;
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aad(sa)->peer = &peer->label;
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profile_match_signal(profile, peer->base.hname, aad(sa)->signal,
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&perms);
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aa_apply_modes_to_perms(profile, &perms);
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return aa_check_perms(profile, &perms, request, sa, audit_signal_cb);
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}
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static int aa_signal_cross_perm(struct aa_profile *sender,
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struct aa_profile *target,
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struct common_audit_data *sa)
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{
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return xcheck(profile_signal_perm(sender, target, MAY_WRITE, sa),
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profile_signal_perm(target, sender, MAY_READ, sa));
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}
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int aa_may_signal(struct aa_label *sender, struct aa_label *target, int sig)
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{
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DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, OP_SIGNAL);
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aad(&sa)->signal = map_signal_num(sig);
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return xcheck_labels_profiles(sender, target, aa_signal_cross_perm,
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&sa);
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}
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@ -656,6 +656,26 @@ static int apparmor_task_setrlimit(struct task_struct *task,
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return error;
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}
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static int apparmor_task_kill(struct task_struct *target, struct siginfo *info,
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int sig, u32 secid)
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{
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struct aa_label *cl, *tl;
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int error;
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if (secid)
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/* TODO: after secid to label mapping is done.
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* Dealing with USB IO specific behavior
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*/
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return 0;
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cl = __begin_current_label_crit_section();
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tl = aa_get_task_label(target);
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error = aa_may_signal(cl, tl, sig);
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aa_put_label(tl);
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__end_current_label_crit_section(cl);
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return error;
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}
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static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
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LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check),
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LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme),
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@ -697,6 +717,7 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
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LSM_HOOK_INIT(bprm_secureexec, apparmor_bprm_secureexec),
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LSM_HOOK_INIT(task_setrlimit, apparmor_task_setrlimit),
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LSM_HOOK_INIT(task_kill, apparmor_task_kill),
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};
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/*
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