[PATCH] audit: add support for session ID user filter

[Richard Guy Briggs]

Define AUDIT_SESSIONID in the uapi and add support for specifying user
filters based on the session ID.

https://github.com/linux-audit/audit-kernel/issues/4
RFE: add a session ID filter to the kernel's user filter

Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
Like loginuid (auid), should this have a seperate field type
(AUDIT_SESSIONID_UNDEFINED maybe?) to explicitly indicate that this
value should be undefined rather than depending on an in-band value of
-1 (or 4294967295)?  If so, now would be the time to fix it.
---

 include/uapi/linux/audit.h |    1 +
 kernel/auditfilter.c       |    2 ++
 kernel/auditsc.c           |    5 +++++
 3 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 843540c..b6feaa7 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -251,6 +251,7 @@
 #define AUDIT_OBJ_LEV_LOW	22
 #define AUDIT_OBJ_LEV_HIGH	23
 #define AUDIT_LOGINUID_SET	24
+#define AUDIT_SESSIONID	25	/* Session ID */
 
 				/* These are ONLY useful when checking
 				 * at syscall exit time (AUDIT_AT_EXIT). */
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index b8ff9e1..23d076c 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -363,6 +363,7 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
 	case AUDIT_EXIT:
 	case AUDIT_SUCCESS:
 	case AUDIT_INODE:
+	case AUDIT_SESSIONID:
 		/* bit ops are only useful on syscall args */
 		if (f->op == Audit_bitmask || f->op == Audit_bittest)
 			return -EINVAL;
@@ -476,6 +477,7 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 			if (!gid_valid(f->gid))
 				goto exit_free;
 			break;
+		case AUDIT_SESSIONID:
 		case AUDIT_ARCH:
 			entry->rule.arch_f = f;
 			break;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b5daaa0..a82b1d9 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -445,6 +445,7 @@ static int audit_filter_rules(struct task_struct *tsk,
 	const struct cred *cred;
 	int i, need_sid = 1;
 	u32 sid;
+	unsigned int sessionid;
 
 	cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation);
 
@@ -507,6 +508,10 @@ static int audit_filter_rules(struct task_struct *tsk,
 		case AUDIT_FSGID:
 			result = audit_gid_comparator(cred->fsgid, f->op, f->gid);
 			break;
+		case AUDIT_SESSIONID:
+			sessionid = audit_get_sessionid(current);
+			result = audit_comparator(sessionid, f->op, f->val);
+			break;
 		case AUDIT_PERS:
 			result = audit_comparator(tsk->personality, f->op, f->val);
 			break;
-- 
1.7.1