[PATCH] filter: add path filter with fstype
Steve Grubb
sgrubb at redhat.com
Tue Jun 13 00:28:20 UTC 2017
Hello,
This patch needs to be refactored to match the current count of error messages
in err_msgtab.
What error message is emitted when run on a kernel that does not support the
new filter?
On Tuesday, April 4, 2017 6:40:18 AM 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 "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
Are we sure path is the best name for this filter? Is there something more
precise like filesystem?
> 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 <rgb at redhat.com>
> ---
> 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.
I don't think this is real clear. Maybe some others need touching up here as
well. But we should say something someone with a casual knowledge of audit
would understand.
> .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 <zhangxiliang at cn.fujitsu.com>
> * Steve Grubb <sgrubb at redhat.com>
> + * Richard Guy Briggs <rgb at redhat.com>
> */
>
> 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" },
> };
Numbers need re-aligning.
-Steve
> #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 <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..ed3e729 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_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 <sgrubb at redhat.com>
> * Rickard E. (Rik) Faith <faith at redhat.com>
> + * Richard Guy Briggs <rgb at redhat.com>
> */
>
> #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 <sgrubb at redhat.com>
> * Rickard E. (Rik) Faith <faith at redhat.com>
> + * Richard Guy Briggs <rgb at redhat.com>
> */
>
> #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");
More information about the Linux-audit
mailing list