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-rw-r--r--Documentation/userspace-api/seccomp_filter.rst9
-rw-r--r--include/uapi/linux/seccomp.h1
-rw-r--r--kernel/seccomp.c23
-rw-r--r--tools/testing/selftests/seccomp/seccomp_bpf.c98
4 files changed, 125 insertions, 6 deletions
diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst
index 2d1d8ab04ac5..f4977357daf2 100644
--- a/Documentation/userspace-api/seccomp_filter.rst
+++ b/Documentation/userspace-api/seccomp_filter.rst
@@ -141,6 +141,15 @@ In precedence order, they are:
allow use of ptrace, even of other sandboxed processes, without
extreme care; ptracers can use this mechanism to escape.)
+``SECCOMP_RET_LOG``:
+ Results in the system call being executed after it is logged. This
+ should be used by application developers to learn which syscalls their
+ application needs without having to iterate through multiple test and
+ development cycles to build the list.
+
+ This action will only be logged if "log" is present in the
+ actions_logged sysctl string.
+
``SECCOMP_RET_ALLOW``:
Results in the system call being executed.
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index 19a611d0712e..f94433263e4b 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -31,6 +31,7 @@
#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */
#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */
#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */
+#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */
#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
/* Masks for the return value sections. */
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index ed9fde418fc4..59cde2ed3b92 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -533,10 +533,12 @@ static void seccomp_send_sigsys(int syscall, int reason)
#define SECCOMP_LOG_TRAP (1 << 2)
#define SECCOMP_LOG_ERRNO (1 << 3)
#define SECCOMP_LOG_TRACE (1 << 4)
-#define SECCOMP_LOG_ALLOW (1 << 5)
+#define SECCOMP_LOG_LOG (1 << 5)
+#define SECCOMP_LOG_ALLOW (1 << 6)
static u32 seccomp_actions_logged = SECCOMP_LOG_KILL | SECCOMP_LOG_TRAP |
- SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE;
+ SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE |
+ SECCOMP_LOG_LOG;
static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
bool requested)
@@ -555,15 +557,18 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
case SECCOMP_RET_TRACE:
log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
break;
+ case SECCOMP_RET_LOG:
+ log = seccomp_actions_logged & SECCOMP_LOG_LOG;
+ break;
case SECCOMP_RET_KILL:
default:
log = seccomp_actions_logged & SECCOMP_LOG_KILL;
}
/*
- * Force an audit message to be emitted when the action is RET_KILL or
- * the FILTER_FLAG_LOG bit was set and the action is allowed to be
- * logged by the admin.
+ * Force an audit message to be emitted when the action is RET_KILL,
+ * RET_LOG, or the FILTER_FLAG_LOG bit was set and the action is
+ * allowed to be logged by the admin.
*/
if (log)
return __audit_seccomp(syscall, signr, action);
@@ -699,6 +704,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
return 0;
+ case SECCOMP_RET_LOG:
+ seccomp_log(this_syscall, 0, action, true);
+ return 0;
+
case SECCOMP_RET_ALLOW:
/*
* Note that the "match" filter will always be NULL for
@@ -873,6 +882,7 @@ static long seccomp_get_action_avail(const char __user *uaction)
case SECCOMP_RET_TRAP:
case SECCOMP_RET_ERRNO:
case SECCOMP_RET_TRACE:
+ case SECCOMP_RET_LOG:
case SECCOMP_RET_ALLOW:
break;
default:
@@ -1023,12 +1033,14 @@ out:
#define SECCOMP_RET_TRAP_NAME "trap"
#define SECCOMP_RET_ERRNO_NAME "errno"
#define SECCOMP_RET_TRACE_NAME "trace"
+#define SECCOMP_RET_LOG_NAME "log"
#define SECCOMP_RET_ALLOW_NAME "allow"
static const char seccomp_actions_avail[] = SECCOMP_RET_KILL_NAME " "
SECCOMP_RET_TRAP_NAME " "
SECCOMP_RET_ERRNO_NAME " "
SECCOMP_RET_TRACE_NAME " "
+ SECCOMP_RET_LOG_NAME " "
SECCOMP_RET_ALLOW_NAME;
struct seccomp_log_name {
@@ -1041,6 +1053,7 @@ static const struct seccomp_log_name seccomp_log_names[] = {
{ SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
{ SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
{ SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
+ { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
{ SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
{ }
};
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 1c8c22ce7740..7372958eccb5 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -74,7 +74,12 @@
#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */
#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */
#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
+#endif
+#ifndef SECCOMP_RET_LOG
+#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */
+#endif
+#ifndef SECCOMP_RET_ACTION
/* Masks for the return value sections. */
#define SECCOMP_RET_ACTION 0x7fff0000U
#define SECCOMP_RET_DATA 0x0000ffffU
@@ -342,6 +347,28 @@ TEST(empty_prog)
EXPECT_EQ(EINVAL, errno);
}
+TEST(log_all)
+{
+ struct sock_filter filter[] = {
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_LOG),
+ };
+ struct sock_fprog prog = {
+ .len = (unsigned short)ARRAY_SIZE(filter),
+ .filter = filter,
+ };
+ long ret;
+ pid_t parent = getppid();
+
+ ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+ ASSERT_EQ(0, ret);
+
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+ ASSERT_EQ(0, ret);
+
+ /* getppid() should succeed and be logged (no check for logging) */
+ EXPECT_EQ(parent, syscall(__NR_getppid));
+}
+
TEST_SIGNAL(unknown_ret_is_kill_inside, SIGSYS)
{
struct sock_filter filter[] = {
@@ -756,6 +783,7 @@ TEST_F(TRAP, handler)
FIXTURE_DATA(precedence) {
struct sock_fprog allow;
+ struct sock_fprog log;
struct sock_fprog trace;
struct sock_fprog error;
struct sock_fprog trap;
@@ -767,6 +795,13 @@ FIXTURE_SETUP(precedence)
struct sock_filter allow_insns[] = {
BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
};
+ struct sock_filter log_insns[] = {
+ BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+ offsetof(struct seccomp_data, nr)),
+ BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_LOG),
+ };
struct sock_filter trace_insns[] = {
BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
offsetof(struct seccomp_data, nr)),
@@ -803,6 +838,7 @@ FIXTURE_SETUP(precedence)
memcpy(self->_x.filter, &_x##_insns, sizeof(_x##_insns)); \
self->_x.len = (unsigned short)ARRAY_SIZE(_x##_insns)
FILTER_ALLOC(allow);
+ FILTER_ALLOC(log);
FILTER_ALLOC(trace);
FILTER_ALLOC(error);
FILTER_ALLOC(trap);
@@ -813,6 +849,7 @@ FIXTURE_TEARDOWN(precedence)
{
#define FILTER_FREE(_x) if (self->_x.filter) free(self->_x.filter)
FILTER_FREE(allow);
+ FILTER_FREE(log);
FILTER_FREE(trace);
FILTER_FREE(error);
FILTER_FREE(trap);
@@ -830,6 +867,8 @@ TEST_F(precedence, allow_ok)
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
@@ -854,6 +893,8 @@ TEST_F_SIGNAL(precedence, kill_is_highest, SIGSYS)
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
@@ -885,6 +926,8 @@ TEST_F_SIGNAL(precedence, kill_is_highest_in_any_order, SIGSYS)
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
@@ -906,6 +949,8 @@ TEST_F_SIGNAL(precedence, trap_is_second, SIGSYS)
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
@@ -931,6 +976,8 @@ TEST_F_SIGNAL(precedence, trap_is_second_in_any_order, SIGSYS)
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
@@ -952,6 +999,8 @@ TEST_F(precedence, errno_is_third)
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
@@ -970,6 +1019,8 @@ TEST_F(precedence, errno_is_third_in_any_order)
ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
@@ -992,6 +1043,8 @@ TEST_F(precedence, trace_is_fourth)
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
ASSERT_EQ(0, ret);
/* Should work just fine. */
@@ -1013,12 +1066,54 @@ TEST_F(precedence, trace_is_fourth_in_any_order)
ASSERT_EQ(0, ret);
ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
/* Should work just fine. */
EXPECT_EQ(parent, syscall(__NR_getppid));
/* No ptracer */
EXPECT_EQ(-1, syscall(__NR_getpid));
}
+TEST_F(precedence, log_is_fifth)
+{
+ pid_t mypid, parent;
+ long ret;
+
+ mypid = getpid();
+ parent = getppid();
+ ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+ ASSERT_EQ(0, ret);
+
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+ ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
+ /* Should work just fine. */
+ EXPECT_EQ(parent, syscall(__NR_getppid));
+ /* Should also work just fine */
+ EXPECT_EQ(mypid, syscall(__NR_getpid));
+}
+
+TEST_F(precedence, log_is_fifth_in_any_order)
+{
+ pid_t mypid, parent;
+ long ret;
+
+ mypid = getpid();
+ parent = getppid();
+ ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+ ASSERT_EQ(0, ret);
+
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+ ASSERT_EQ(0, ret);
+ ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+ ASSERT_EQ(0, ret);
+ /* Should work just fine. */
+ EXPECT_EQ(parent, syscall(__NR_getppid));
+ /* Should also work just fine */
+ EXPECT_EQ(mypid, syscall(__NR_getpid));
+}
+
#ifndef PTRACE_O_TRACESECCOMP
#define PTRACE_O_TRACESECCOMP 0x00000080
#endif
@@ -2603,7 +2698,7 @@ TEST(get_action_avail)
{
__u32 actions[] = { SECCOMP_RET_KILL, SECCOMP_RET_TRAP,
SECCOMP_RET_ERRNO, SECCOMP_RET_TRACE,
- SECCOMP_RET_ALLOW };
+ SECCOMP_RET_LOG, SECCOMP_RET_ALLOW };
__u32 unknown_action = 0x10000000U;
int i;
long ret;
@@ -2640,6 +2735,7 @@ TEST(get_action_avail)
* - 64-bit arg prodding
* - arch value testing (x86 modes especially)
* - verify that FILTER_FLAG_LOG filters generate log messages
+ * - verify that RET_LOG generates log messages
* - ...
*/
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.