[PATCH] filter: add filesystem filter with fstype
Steve Grubb
sgrubb at redhat.com
Mon Jun 19 16:46:03 UTC 2017
On Friday, June 16, 2017 4:29:46 PM EDT Richard Guy Briggs wrote:
> 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
> Test case: https://github.com/linux-audit/audit-testsuite/issues/42
>
> Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
> ---
> 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 at cn.fujitsu.com>
> * Steve Grubb <sgrubb at redhat.com>
> + * Richard Guy Briggs <rgb at 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 at redhat.com>
> + * Richard Guy Briggs <rgb at 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 at redhat.com>
> + * Richard Guy Briggs <rgb at 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" )
Why are these ^^^ in the patch?
> +_S(AUDIT_FILTER_FS, "filesystem")
> diff --git a/lib/libaudit.c b/lib/libaudit.c
> index 18cd384..34677b9 100644
> --- a/lib/libaudit.c
> +++ b/lib/libaudit.c
> @@ -19,6 +19,7 @@
> * Authors:
> * Steve Grubb <sgrubb at redhat.com>
> * Rickard E. (Rik) Faith <faith at redhat.com>
> + * Richard Guy Briggs <rgb at 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_PATH) == 0) {
Doesn't the kernel feature bitmap names need updating?
> + 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..d7336fd 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_PATH
> +#define AUDIT_FEATURE_BITMAP_FILTER_PATH 0x00000040
> +#endif
Same comment. Otherwise, it looks OK.
-Steve
> /* 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 at redhat.com>
> * Rickard E. (Rik) Faith <faith at redhat.com>
> + * Richard Guy Briggs <rgb at 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;
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