[PATCH V8 2/3] audit: implement audit by executable

From: Richard Guy Briggs
Date: Wed Aug 05 2015 - 05:27:08 EST

This adds the ability audit the actions of a not-yet-running process.

This patch implements the ability to filter on the executable path. Instead of
just hard coding the ino and dev of the executable we care about at the moment
the rule is inserted into the kernel, use the new audit_fsnotify
infrastructure to manage this dynamically. This means that if the filename
does not yet exist but the containing directory does, or if the inode in
question is unlinked and creat'd (aka updated) the rule will just continue to
work. If the containing directory is moved or deleted or the filesystem is
unmounted, the rule is deleted automatically. A future enhancement would be to
have the rule survive across directory disruptions.

This is a heavily modified version of a patch originally submitted by Eric
Paris with some ideas from Peter Moody.

Cc: Peter Moody <peter@xxxxxxxx>
Cc: Eric Paris <eparis@xxxxxxxxxx>
Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
include/linux/audit.h | 1 +
include/uapi/linux/audit.h | 5 +++-
kernel/audit.h | 4 +++
kernel/audit_tree.c | 2 +
kernel/audit_watch.c | 31 +++++++++++++++++++++++++++
kernel/auditfilter.c | 50 +++++++++++++++++++++++++++++++++++++++++++-
kernel/auditsc.c | 3 ++
7 files changed, 94 insertions(+), 2 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index c2e7e3a..aee456f 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -59,6 +59,7 @@ struct audit_krule {
struct audit_field *inode_f; /* quick access to an inode field */
struct audit_watch *watch; /* associated watch */
struct audit_tree *tree; /* associated watched tree */
+ struct audit_fsnotify_mark *exe;
struct list_head rlist; /* entry in audit_{watch,tree}.rules list */
struct list_head list; /* for AUDIT_LIST* purposes only */
u64 prio;
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 971df22..e2ca600 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -266,6 +266,7 @@
#define AUDIT_OBJ_UID 109
#define AUDIT_OBJ_GID 110
#define AUDIT_FIELD_COMPARE 111
+#define AUDIT_EXE 112

#define AUDIT_ARG0 200
#define AUDIT_ARG1 (AUDIT_ARG0+1)
@@ -324,8 +325,10 @@ enum {

#define AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT 0x00000001
#define AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME 0x00000002
+#define AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH 0x00000004
#define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
- AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME)
+ AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
+ AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH )

/* deprecated: AUDIT_VERSION_* */
#define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP_ALL
diff --git a/kernel/audit.h b/kernel/audit.h
index 46d10dd..dadf86a 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -277,6 +277,8 @@ extern char *audit_mark_path(struct audit_fsnotify_mark *mark);
extern void audit_remove_mark(struct audit_fsnotify_mark *audit_mark);
extern void audit_remove_mark_rule(struct audit_krule *krule);
extern int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long ino, dev_t dev);
+extern int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old);
+extern int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark);

#else
#define audit_put_watch(w) {}
@@ -292,6 +294,8 @@ extern int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long in
#define audit_remove_mark(m)
#define audit_remove_mark_rule(k)
#define audit_mark_compare(m, i, d) 0
+#define audit_exe_compare(t, m) (-EINVAL)
+#define audit_dupe_exe(n, o) (-EINVAL)
#endif /* CONFIG_AUDIT_WATCH */

#ifdef CONFIG_AUDIT_TREE
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index b0f9877..94ecdab 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -479,6 +479,8 @@ static void kill_rules(struct audit_tree *tree)
if (rule->tree) {
/* not a half-baked one */
audit_tree_log_remove_rule(rule);
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe);
rule->tree = NULL;
list_del_rcu(&entry->list);
list_del(&entry->rule.list);
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index c668bfc..1255dbf 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -312,6 +312,8 @@ static void audit_update_watch(struct audit_parent *parent,
list_replace(&oentry->rule.list,
&nentry->rule.list);
}
+ if (oentry->rule.exe)
+ audit_remove_mark(oentry->rule.exe);

audit_watch_log_rule_change(r, owatch, "updated_rules");

@@ -342,6 +344,8 @@ static void audit_remove_parent_watches(struct audit_parent *parent)
list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
e = container_of(r, struct audit_entry, rule);
audit_watch_log_rule_change(r, w, "remove_rule");
+ if (e->rule.exe)
+ audit_remove_mark(e->rule.exe);
list_del(&r->rlist);
list_del(&r->list);
list_del_rcu(&e->list);
@@ -514,3 +518,30 @@ static int __init audit_watch_init(void)
return 0;
}
device_initcall(audit_watch_init);
+
+int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
+{
+ struct audit_fsnotify_mark *audit_mark;
+ char *pathname;
+
+ pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
+ if (!pathname)
+ return -ENOMEM;
+
+ audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
+ if (IS_ERR(audit_mark)) {
+ kfree(pathname);
+ return PTR_ERR(audit_mark);
+ }
+ new->exe = audit_mark;
+
+ return 0;
+}
+
+int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
+{
+ unsigned long ino = tsk->mm->exe_file->f_inode->i_ino;
+ dev_t dev = tsk->mm->exe_file->f_inode->i_sb->s_dev;
+
+ return audit_mark_compare(mark, ino, dev);
+}
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 401bc1a..c662638 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -405,6 +405,12 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
if (f->val > AUDIT_MAX_FIELD_COMPARE)
return -EINVAL;
break;
+ case AUDIT_EXE:
+ if (f->op != Audit_equal)
+ return -EINVAL;
+ if (entry->rule.listnr != AUDIT_FILTER_EXIT)
+ return -EINVAL;
+ break;
};
return 0;
}
@@ -419,6 +425,7 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
size_t remain = datasz - sizeof(struct audit_rule_data);
int i;
char *str;
+ struct audit_fsnotify_mark *audit_mark;

entry = audit_to_entry_common(data);
if (IS_ERR(entry))
@@ -539,6 +546,24 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
entry->rule.buflen += f->val;
entry->rule.filterkey = str;
break;
+ case AUDIT_EXE:
+ if (entry->rule.exe || f->val > PATH_MAX)
+ goto exit_free;
+ str = audit_unpack_string(&bufp, &remain, f->val);
+ if (IS_ERR(str)) {
+ err = PTR_ERR(str);
+ goto exit_free;
+ }
+ entry->rule.buflen += f->val;
+
+ audit_mark = audit_alloc_mark(&entry->rule, str, f->val);
+ if (IS_ERR(audit_mark)) {
+ kfree(str);
+ err = PTR_ERR(audit_mark);
+ goto exit_free;
+ }
+ entry->rule.exe = audit_mark;
+ break;
}
}

@@ -551,6 +576,8 @@ exit_nofree:
exit_free:
if (entry->rule.tree)
audit_put_tree(entry->rule.tree); /* that's the temporary one */
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe); /* that's the template one */
audit_free_rule(entry);
return ERR_PTR(err);
}
@@ -615,6 +642,10 @@ static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule)
data->buflen += data->values[i] =
audit_pack_string(&bufp, krule->filterkey);
break;
+ case AUDIT_EXE:
+ data->buflen += data->values[i] =
+ audit_pack_string(&bufp, audit_mark_path(krule->exe));
+ break;
case AUDIT_LOGINUID_SET:
if (krule->pflags & AUDIT_LOGINUID_LEGACY && !f->val) {
data->fields[i] = AUDIT_LOGINUID;
@@ -678,6 +709,12 @@ static int audit_compare_rule(struct audit_krule *a, struct audit_krule *b)
if (strcmp(a->filterkey, b->filterkey))
return 1;
break;
+ case AUDIT_EXE:
+ /* both paths exist based on above type compare */
+ if (strcmp(audit_mark_path(a->exe),
+ audit_mark_path(b->exe)))
+ return 1;
+ break;
case AUDIT_UID:
case AUDIT_EUID:
case AUDIT_SUID:
@@ -799,8 +836,14 @@ struct audit_entry *audit_dupe_rule(struct audit_krule *old)
err = -ENOMEM;
else
new->filterkey = fk;
+ break;
+ case AUDIT_EXE:
+ err = audit_dupe_exe(new, old);
+ break;
}
if (err) {
+ if (new->exe)
+ audit_remove_mark(new->exe);
audit_free_rule(entry);
return ERR_PTR(err);
}
@@ -1070,8 +1113,11 @@ int audit_rule_change(int type, __u32 portid, int seq, void *data,
WARN_ON(1);
}

- if (err || type == AUDIT_DEL_RULE)
+ if (err || type == AUDIT_DEL_RULE) {
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe);
audit_free_rule(entry);
+ }

return err;
}
@@ -1363,6 +1409,8 @@ static int update_lsm_rule(struct audit_krule *r)
return 0;

nentry = audit_dupe_rule(r);
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe);
if (IS_ERR(nentry)) {
/* save the first error encountered for the
* return value */
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 701ea5c..e9bac2b 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -466,6 +466,9 @@ static int audit_filter_rules(struct task_struct *tsk,
result = audit_comparator(ctx->ppid, f->op, f->val);
}
break;
+ case AUDIT_EXE:
+ result = audit_exe_compare(tsk, rule->exe);
+ break;
case AUDIT_UID:
result = audit_uid_comparator(cred->uid, f->op, f->uid);
break;
--
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/