Tracefs or debugfs were causing hundreds to thousands of PATH records to
be associated with the init_module and finit_module SYSCALL records on a
few modules when the following rule was in place for startup:
-a always,exit -F arch=x86_64 -S init_module -F key=mod-load
Add the new "path" filter list anchored in __audit_inode_child() to
filter out PATH records from uninteresting filesystem types, "fstype",
keying on their kernel hexadecimal 4-octet magic identifier.
An example rule would look like:
-a never,path -F fstype=0x74726163 -F key=ignore_tracefs
-a never,path -F fstype=0x64626720 -F key=ignore_debugfs
Note: "always,path" will log the PATH record anyways and add latency.
See: https://github.com/linux-audit/audit-userspace/issues/15
See: https://github.com/linux-audit/audit-kernel/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42
Signed-off-by: Richard Guy Briggs <[email protected]>
---
docs/audit_add_rule_data.3 | 3 +++
lib/errormsg.h | 5 +++++
lib/fieldtab.h | 2 ++
lib/flagtab.h | 2 ++
lib/libaudit.c | 26 ++++++++++++++++++++++++--
lib/libaudit.h | 10 ++++++++++
lib/private.h | 1 +
src/auditctl-listing.c | 6 ++++--
src/auditctl.c | 14 +++++++++++++-
9 files changed, 64 insertions(+), 5 deletions(-)
diff --git a/docs/audit_add_rule_data.3 b/docs/audit_add_rule_data.3
index 2321f39..4867e8c 100644
--- a/docs/audit_add_rule_data.3
+++ b/docs/audit_add_rule_data.3
@@ -22,6 +22,9 @@ AUDIT_FILTER_EXIT - Apply rule at syscall exit.
.TP
\(bu
AUDIT_FILTER_TYPE - Apply rule at audit_log_start.
+.TP
+\(bu
+AUDIT_FILTER_PATH - Apply rule at __audit_inode_child.
.LP
.PP
diff --git a/lib/errormsg.h b/lib/errormsg.h
index 50c7d50..2a6e4d6 100644
--- a/lib/errormsg.h
+++ b/lib/errormsg.h
@@ -20,6 +20,7 @@
* Authors:
* Zhang Xiliang <[email protected]>
* Steve Grubb <[email protected]>
+ * Richard Guy Briggs <[email protected]>
*/
struct msg_tab {
@@ -70,6 +71,8 @@ static const struct msg_tab err_msgtab[] = {
{ -32, 0, "field data is missing" },
{ -33, 2, "-C field incompatible" },
{ -34, 2, "-C value incompatible" },
+ { -35, 1, "field is not valid for the filter" },
+ { -36, 1, "filter is not supported ty kernel" },
};
#define EAU_OPMISSING 1
#define EAU_FIELDUNKNOWN 2
@@ -103,4 +106,6 @@ static const struct msg_tab err_msgtab[] = {
#define EAU_DATAMISSING 32
#define EAU_COMPFIELDINCOMPAT 33
#define EAU_COMPVALINCOMPAT 34
+#define EAU_FIELDUNAVAIL 35
+#define EAU_FILTERNOSUPPORT 36
#endif
diff --git a/lib/fieldtab.h b/lib/fieldtab.h
index 0c5e39d..c425d5b 100644
--- a/lib/fieldtab.h
+++ b/lib/fieldtab.h
@@ -18,6 +18,7 @@
*
* Authors:
* Steve Grubb <[email protected]>
+ * Richard Guy Briggs <[email protected]>
*/
_S(AUDIT_PID, "pid" )
@@ -56,6 +57,7 @@ _S(AUDIT_WATCH, "path" )
_S(AUDIT_PERM, "perm" )
_S(AUDIT_DIR, "dir" )
_S(AUDIT_FILETYPE, "filetype" )
+_S(AUDIT_FSTYPE, "fstype" )
_S(AUDIT_OBJ_UID, "obj_uid" )
_S(AUDIT_OBJ_GID, "obj_gid" )
_S(AUDIT_FIELD_COMPARE, "field_compare" )
diff --git a/lib/flagtab.h b/lib/flagtab.h
index 4b04692..ed3e729 100644
--- a/lib/flagtab.h
+++ b/lib/flagtab.h
@@ -18,8 +18,10 @@
*
* Authors:
* Steve Grubb <[email protected]>
+ * Richard Guy Briggs <[email protected]>
*/
_S(AUDIT_FILTER_TASK, "task" )
_S(AUDIT_FILTER_EXIT, "exit" )
_S(AUDIT_FILTER_USER, "user" )
_S(AUDIT_FILTER_EXCLUDE, "exclude" )
+_S(AUDIT_FILTER_PATH, "path" )
diff --git a/lib/libaudit.c b/lib/libaudit.c
index 028483d..f28238a 100644
--- a/lib/libaudit.c
+++ b/lib/libaudit.c
@@ -19,6 +19,7 @@
* Authors:
* Steve Grubb <[email protected]>
* Rickard E. (Rik) Faith <[email protected]>
+ * Richard Guy Briggs <[email protected]>
*/
#include "config.h"
@@ -86,6 +87,7 @@ int _audit_archadded = 0;
int _audit_syscalladded = 0;
int _audit_exeadded = 0;
int _audit_filterexcladded = 0;
+int _audit_filterpathadded = 0;
unsigned int _audit_elf = 0U;
static struct libaudit_conf config;
@@ -1475,6 +1477,23 @@ int audit_rule_fieldpair_data(struct audit_rule_data
**rulep, const char *pair,
}
}
+ /* PATH filter can be used only with FSTYPE field */
+ if (flags == AUDIT_FILTER_PATH) {
+ uint32_t features = audit_get_features();
+ if ((features & AUDIT_FEATURE_BITMAP_FILTER_PATH) == 0) {
+ return -EAU_FILTERNOSUPPORT;
+ } else {
+ switch(field) {
+ case AUDIT_FSTYPE:
+ _audit_filterpathadded = 1;
+ case AUDIT_FILTERKEY:
+ break;
+ default:
+ return -EAU_FIELDUNAVAIL;
+ }
+ }
+ }
+
rule->fields[rule->field_count] = field;
rule->fieldflags[rule->field_count] = op;
switch (field)
@@ -1589,7 +1608,8 @@ int audit_rule_fieldpair_data(struct audit_rule_data
**rulep, const char *pair,
}
if (field == AUDIT_FILTERKEY &&
!(_audit_syscalladded || _audit_permadded ||
- _audit_exeadded || _audit_filterexcladded))
+ _audit_exeadded || _audit_filterexcladded ||
+ _audit_filterpathadded))
return -EAU_KEYDEP;
vlen = strlen(v);
if (field == AUDIT_FILTERKEY &&
@@ -1724,7 +1744,7 @@ int audit_rule_fieldpair_data(struct audit_rule_data
**rulep, const char *pair,
return -EAU_EXITONLY;
/* fallthrough */
default:
- if (field == AUDIT_INODE) {
+ if (field == AUDIT_INODE || field == AUDIT_FSTYPE) {
if (!(op == AUDIT_NOT_EQUAL ||
op == AUDIT_EQUAL))
return -EAU_OPEQNOTEQ;
@@ -1736,6 +1756,8 @@ int audit_rule_fieldpair_data(struct audit_rule_data
**rulep, const char *pair,
if (!isdigit((char)*(v)))
return -EAU_FIELDVALNUM;
+ if (field == AUDIT_FSTYPE && flags != AUDIT_FILTER_PATH)
+ return -EAU_FIELDUNAVAIL;
if (field == AUDIT_INODE)
rule->values[rule->field_count] =
strtoul(v, NULL, 0);
diff --git a/lib/libaudit.h b/lib/libaudit.h
index e5c7a4d..e9c4973 100644
--- a/lib/libaudit.h
+++ b/lib/libaudit.h
@@ -277,6 +277,9 @@ extern "C" {
#define AUDIT_KEY_SEPARATOR 0x01
/* These are used in filter control */
+#ifndef AUDIT_FILTER_PATH
+#define AUDIT_FILTER_PATH 0x06 /* PATH record filter in
__audit_inode_child */
+#endif
#define AUDIT_FILTER_EXCLUDE AUDIT_FILTER_TYPE
#define AUDIT_FILTER_MASK 0x07 /* Mask to get actual filter */
#define AUDIT_FILTER_UNSET 0x80 /* This value means filter is unset */
@@ -305,6 +308,9 @@ extern "C" {
#ifndef AUDIT_FEATURE_BITMAP_LOST_RESET
#define AUDIT_FEATURE_BITMAP_LOST_RESET 0x00000020
#endif
+#ifndef AUDIT_FEATURE_BITMAP_FILTER_PATH
+#define AUDIT_FEATURE_BITMAP_FILTER_PATH 0x00000040
+#endif
/* Defines for interfield comparison update */
#ifndef AUDIT_OBJ_UID
@@ -324,6 +330,10 @@ extern "C" {
#define AUDIT_SESSIONID 25
#endif
+#ifndef AUDIT_FSTYPE
+#define AUDIT_FSTYPE 26
+#endif
+
#ifndef AUDIT_COMPARE_UID_TO_OBJ_UID
#define AUDIT_COMPARE_UID_TO_OBJ_UID 1
#endif
diff --git a/lib/private.h b/lib/private.h
index 855187b..117d6e3 100644
--- a/lib/private.h
+++ b/lib/private.h
@@ -140,6 +140,7 @@ extern int _audit_archadded;
extern int _audit_syscalladded;
extern int _audit_exeadded;
extern int _audit_filterexcladded;
+extern int _audit_filterpathadded;
extern unsigned int _audit_elf;
#ifdef __cplusplus
diff --git a/src/auditctl-listing.c b/src/auditctl-listing.c
index 3bc8e71..e8640dd 100644
--- a/src/auditctl-listing.c
+++ b/src/auditctl-listing.c
@@ -91,7 +91,8 @@ static int is_watch(const struct audit_rule_data *r)
if (((r->flags & AUDIT_FILTER_MASK) != AUDIT_FILTER_USER) &&
((r->flags & AUDIT_FILTER_MASK) != AUDIT_FILTER_TASK) &&
- ((r->flags & AUDIT_FILTER_MASK) != AUDIT_FILTER_EXCLUDE)) {
+ ((r->flags & AUDIT_FILTER_MASK) != AUDIT_FILTER_EXCLUDE) &&
+ ((r->flags & AUDIT_FILTER_MASK) != AUDIT_FILTER_PATH)) {
for (i = 0; i < (AUDIT_BITMASK_SIZE-1); i++) {
if (r->mask[i] != (uint32_t)~0) {
all = 0;
@@ -139,7 +140,8 @@ static int print_syscall(const struct audit_rule_data *r,
unsigned int *sc)
/* Rules on the following filters do not take a syscall */
if (((r->flags & AUDIT_FILTER_MASK) == AUDIT_FILTER_USER) ||
((r->flags & AUDIT_FILTER_MASK) == AUDIT_FILTER_TASK) ||
- ((r->flags &AUDIT_FILTER_MASK) == AUDIT_FILTER_EXCLUDE))
+ ((r->flags &AUDIT_FILTER_MASK) == AUDIT_FILTER_EXCLUDE) ||
+ ((r->flags &AUDIT_FILTER_MASK) == AUDIT_FILTER_PATH))
return 0;
/* See if its all or specific syscalls */
diff --git a/src/auditctl.c b/src/auditctl.c
index c785087..c7e8f0f 100644
--- a/src/auditctl.c
+++ b/src/auditctl.c
@@ -19,6 +19,7 @@
* Authors:
* Steve Grubb <[email protected]>
* Rickard E. (Rik) Faith <[email protected]>
+ * Richard Guy Briggs <[email protected]>
*/
#include "config.h"
@@ -75,6 +76,7 @@ static int reset_vars(void)
_audit_archadded = 0;
_audit_exeadded = 0;
_audit_filterexcladded = 0;
+ _audit_filterpathadded = 0;
_audit_elf = 0;
add = AUDIT_FILTER_UNSET;
del = AUDIT_FILTER_UNSET;
@@ -152,6 +154,8 @@ static int lookup_filter(const char *str, int *filter)
*filter = AUDIT_FILTER_EXIT;
else if (strcmp(str, "user") == 0)
*filter = AUDIT_FILTER_USER;
+ else if (strcmp(str, "path") == 0)
+ *filter = AUDIT_FILTER_PATH;
else if (strcmp(str, "exclude") == 0) {
*filter = AUDIT_FILTER_EXCLUDE;
exclude = 1;
@@ -761,6 +765,13 @@ static int setopt(int count, int lineno, char *vars[])
audit_msg(LOG_ERR,
"Error: syscall auditing being added to user list");
return -1;
+ } else if (((add & (AUDIT_FILTER_MASK|AUDIT_FILTER_UNSET)) ==
+ AUDIT_FILTER_PATH || (del &
+ (AUDIT_FILTER_MASK|AUDIT_FILTER_UNSET)) ==
+ AUDIT_FILTER_PATH)) {
+ audit_msg(LOG_ERR,
+ "Error: syscall auditing being added to path list");
+ return -1;
} else if (exclude) {
audit_msg(LOG_ERR,
"Error: syscall auditing cannot be put on exclude list");
@@ -937,7 +948,8 @@ static int setopt(int count, int lineno, char *vars[])
break;
case 'k':
if (!(_audit_syscalladded || _audit_permadded ||
- _audit_exeadded || _audit_filterexcladded) ||
+ _audit_exeadded || _audit_filterexcladded ||
+ _audit_filterpathadded) ||
(add==AUDIT_FILTER_UNSET && del==AUDIT_FILTER_UNSET)) {
audit_msg(LOG_ERR,
"key option needs a watch or syscall given prior to it");
--
1.7.1
--
Linux-audit mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-audit
