Re: [PATCH V3] filter: add filesystem filter with fstype

On Tuesday, June 27, 2017 2:46:29 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 > 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&gt; Applied. However, I don't like the idea of making people type in magic numbers. I'll start a fs name to magic translator and just add a few file systems.

-Steve > --- > 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&gt; > * Steve Grubb <sgrubb(a)redhat.com&gt; > + * Richard Guy Briggs <rgb(a)redhat.com&gt; > */ > > 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&gt; > + * Richard Guy Briggs <rgb(a)redhat.com&gt; > */ > > _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&gt; > + * Richard Guy Briggs <rgb(a)redhat.com&gt; > */ > -_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&gt; > * Rickard E. (Rik) Faith <faith(a)redhat.com&gt; > + * Richard Guy Briggs <rgb(a)redhat.com&gt; > */ > > #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&gt; > * Rickard E. (Rik) Faith <faith(a)redhat.com&gt; > + * Richard Guy Briggs <rgb(a)redhat.com&gt; > */ > > #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;