1:46 p.m.
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 "filesystem" 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,filesystem -F fstype=0x74726163 -F key=ignore_tracefs
-a never,filesystem -F fstype=0x64626720 -F key=ignore_debugfs
Note: "always,filesystem" will log the PATH record anyways and add latency.
See: https://github.com/linux-audit/audit-kernel/issues/8
See: https://github.com/linux-audit/audit-userspace/issues/15
Test case: https://github.com/linux-audit/audit-testsuite/issues/42
Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com>
---
v3:
Update feature bitmap macros to reflect filter name change.
v2:
Change filter name from "path" to "filesystem".
Rebase onto other patches accepted upstream.
docs/audit_add_rule_data.3 | 3 +++
lib/errormsg.h | 5 +++++
lib/fieldtab.h | 2 ++
lib/flagtab.h | 10 ++++++----
lib/libaudit.c | 26 ++++++++++++++++++++++++--
lib/libaudit.h | 10 ++++++++++
lib/private.h | 1 +
src/auditctl-listing.c | 6 ++++--
src/auditctl.c | 16 ++++++++++++++--
9 files changed, 69 insertions(+), 10 deletions(-)
diff --git a/docs/audit_add_rule_data.3 b/docs/audit_add_rule_data.3
index a0802c0..1e7540c 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. This is the main filter
that is
.TP
\(bu
AUDIT_FILTER_TYPE - Apply rule at audit_log_start. This is the exclude filter which
discards any records that match.
+.TP
+\(bu
+AUDIT_FILTER_FS - Apply rule when adding PATH auxiliary records to SYSCALL events. This
is the filesystem filter. This is used to ignore PATH records that are not of interest.
.LP
.PP
diff --git a/lib/errormsg.h b/lib/errormsg.h
index 91d8252..ef54589 100644
--- a/lib/errormsg.h
+++ b/lib/errormsg.h
@@ -20,6 +20,7 @@
* Authors:
* Zhang Xiliang <zhangxiliang(a)cn.fujitsu.com>
* Steve Grubb <sgrubb(a)redhat.com>
+ * Richard Guy Briggs <rgb(a)redhat.com>
*/
struct msg_tab {
@@ -66,6 +67,8 @@ struct msg_tab {
#define EAU_FIELDNOFILTER 31
#define EAU_FILTERMISSING 32
#define EAU_COMPINCOMPAT 33
+#define EAU_FIELDUNAVAIL 34
+#define EAU_FILTERNOSUPPORT 35
static const struct msg_tab err_msgtab[] = {
{ -EAU_OPMISSING, 2, "-F missing operation for" },
{ -EAU_FIELDUNKNOWN, 2, "-F unknown field:" },
@@ -100,5 +103,7 @@ static const struct msg_tab err_msgtab[] = {
{ -EAU_FIELDNOFILTER, 1, "must be used with exclude, user, or exit filter"
},
{ -EAU_FILTERMISSING, 0, "filter is missing from rule" },
{ -EAU_COMPINCOMPAT, 2, "-C incompatible comparison" },
+ { -EAU_FIELDUNAVAIL, 1, "field is not valid for the filter" },
+ { -EAU_FILTERNOSUPPORT, 1, "filter is not supported ty kernel" },
};
#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 <sgrubb(a)redhat.com>
+ * Richard Guy Briggs <rgb(a)redhat.com>
*/
_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..7a618e0 100644
--- a/lib/flagtab.h
+++ b/lib/flagtab.h
@@ -18,8 +18,10 @@
*
* Authors:
* Steve Grubb <sgrubb(a)redhat.com>
+ * Richard Guy Briggs <rgb(a)redhat.com>
*/
-_S(AUDIT_FILTER_TASK, "task" )
-_S(AUDIT_FILTER_EXIT, "exit" )
-_S(AUDIT_FILTER_USER, "user" )
-_S(AUDIT_FILTER_EXCLUDE, "exclude" )
+_S(AUDIT_FILTER_TASK, "task" )
+_S(AUDIT_FILTER_EXIT, "exit" )
+_S(AUDIT_FILTER_USER, "user" )
+_S(AUDIT_FILTER_EXCLUDE, "exclude" )
+_S(AUDIT_FILTER_FS, "filesystem")
diff --git a/lib/libaudit.c b/lib/libaudit.c
index 18cd384..58134a2 100644
--- a/lib/libaudit.c
+++ b/lib/libaudit.c
@@ -19,6 +19,7 @@
* Authors:
* Steve Grubb <sgrubb(a)redhat.com>
* Rickard E. (Rik) Faith <faith(a)redhat.com>
+ * Richard Guy Briggs <rgb(a)redhat.com>
*/
#include "config.h"
@@ -85,6 +86,7 @@ int _audit_permadded = 0;
int _audit_archadded = 0;
int _audit_syscalladded = 0;
int _audit_exeadded = 0;
+int _audit_filterfsadded = 0;
unsigned int _audit_elf = 0U;
static struct libaudit_conf config;
@@ -1466,6 +1468,23 @@ int audit_rule_fieldpair_data(struct audit_rule_data **rulep, const
char *pair,
}
}
+ /* FS filter can be used only with FSTYPE field */
+ if (flags == AUDIT_FILTER_FS) {
+ uint32_t features = audit_get_features();
+ if ((features & AUDIT_FEATURE_BITMAP_FILTER_FS) == 0) {
+ return -EAU_FILTERNOSUPPORT;
+ } else {
+ switch(field) {
+ case AUDIT_FSTYPE:
+ _audit_filterfsadded = 1;
+ case AUDIT_FILTERKEY:
+ break;
+ default:
+ return -EAU_FIELDUNAVAIL;
+ }
+ }
+ }
+
rule->fields[rule->field_count] = field;
rule->fieldflags[rule->field_count] = op;
switch (field)
@@ -1580,7 +1599,8 @@ int audit_rule_fieldpair_data(struct audit_rule_data **rulep, const
char *pair,
}
if (field == AUDIT_FILTERKEY &&
!(_audit_syscalladded || _audit_permadded ||
- _audit_exeadded))
+ _audit_exeadded ||
+ _audit_filterfsadded))
return -EAU_KEYDEP;
vlen = strlen(v);
if (field == AUDIT_FILTERKEY &&
@@ -1715,7 +1735,7 @@ 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;
@@ -1727,6 +1747,8 @@ 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_FS)
+ 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..70646cd 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_FS
+#define AUDIT_FILTER_FS 0x06 /* FS 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_FS
+#define AUDIT_FEATURE_BITMAP_FILTER_FS 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 cde1906..bd5e8b3 100644
--- a/lib/private.h
+++ b/lib/private.h
@@ -139,6 +139,7 @@ extern int _audit_permadded;
extern int _audit_archadded;
extern int _audit_syscalladded;
extern int _audit_exeadded;
+extern int _audit_filterfsadded;
extern unsigned int _audit_elf;
#ifdef __cplusplus
diff --git a/src/auditctl-listing.c b/src/auditctl-listing.c
index 3bc8e71..50bc0b8 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_FS)) {
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_FS))
return 0;
/* See if its all or specific syscalls */
diff --git a/src/auditctl.c b/src/auditctl.c
index 04765f4..b99c957 100644
--- a/src/auditctl.c
+++ b/src/auditctl.c
@@ -19,6 +19,7 @@
* Authors:
* Steve Grubb <sgrubb(a)redhat.com>
* Rickard E. (Rik) Faith <faith(a)redhat.com>
+ * Richard Guy Briggs <rgb(a)redhat.com>
*/
#include "config.h"
@@ -74,6 +75,7 @@ static int reset_vars(void)
_audit_permadded = 0;
_audit_archadded = 0;
_audit_exeadded = 0;
+ _audit_filterfsadded = 0;
_audit_elf = 0;
add = AUDIT_FILTER_UNSET;
del = AUDIT_FILTER_UNSET;
@@ -151,6 +153,8 @@ 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, "filesystem") == 0)
+ *filter = AUDIT_FILTER_FS;
else if (strcmp(str, "exclude") == 0) {
*filter = AUDIT_FILTER_EXCLUDE;
exclude = 1;
@@ -760,6 +764,13 @@ 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_FS || (del &
+ (AUDIT_FILTER_MASK|AUDIT_FILTER_UNSET)) ==
+ AUDIT_FILTER_FS)) {
+ audit_msg(LOG_ERR,
+ "Error: syscall auditing being added to filesystem list");
+ return -1;
} else if (exclude) {
audit_msg(LOG_ERR,
"Error: syscall auditing cannot be put on exclude list");
@@ -936,8 +947,9 @@ static int setopt(int count, int lineno, char *vars[])
break;
case 'k':
if (!(_audit_syscalladded || _audit_permadded ||
- _audit_exeadded) || (add==AUDIT_FILTER_UNSET &&
- del==AUDIT_FILTER_UNSET)) {
+ _audit_exeadded ||
+ _audit_filterfsadded) ||
+ (add==AUDIT_FILTER_UNSET && del==AUDIT_FILTER_UNSET)) {
audit_msg(LOG_ERR,
"key option needs a watch or syscall given prior to it");
retval = -1;
--
1.7.1