integrity: IMA policy
Support for a user loadable policy through securityfs
with support for LSM specific policy data.
- free invalid rule in ima_parse_add_rule()
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 7c3d1ff..bd45360 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -15,6 +15,7 @@
#include <linux/audit.h>
#include <linux/security.h>
#include <linux/magic.h>
+#include <linux/parser.h>
#include "ima.h"
@@ -24,7 +25,12 @@
#define IMA_FSMAGIC 0x0004
#define IMA_UID 0x0008
-enum ima_action { DONT_MEASURE, MEASURE };
+enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
+
+#define MAX_LSM_RULES 6
+enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
+ LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
+};
struct ima_measure_rule_entry {
struct list_head list;
@@ -34,8 +40,15 @@
int mask;
unsigned long fsmagic;
uid_t uid;
+ struct {
+ void *rule; /* LSM file metadata specific */
+ int type; /* audit type */
+ } lsm[MAX_LSM_RULES];
};
+/* Without LSM specific knowledge, the default policy can only be
+ * written in terms of .action, .func, .mask, .fsmagic, and .uid
+ */
static struct ima_measure_rule_entry default_rules[] = {
{.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,
.flags = IMA_FSMAGIC},
@@ -54,8 +67,11 @@
};
static LIST_HEAD(measure_default_rules);
+static LIST_HEAD(measure_policy_rules);
static struct list_head *ima_measure;
+static DEFINE_MUTEX(ima_measure_mutex);
+
/**
* ima_match_rules - determine whether an inode matches the measure rule.
* @rule: a pointer to a rule
@@ -69,6 +85,7 @@
struct inode *inode, enum ima_hooks func, int mask)
{
struct task_struct *tsk = current;
+ int i;
if ((rule->flags & IMA_FUNC) && rule->func != func)
return false;
@@ -79,6 +96,39 @@
return false;
if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
return false;
+ for (i = 0; i < MAX_LSM_RULES; i++) {
+ int rc;
+ u32 osid, sid;
+
+ if (!rule->lsm[i].rule)
+ continue;
+
+ switch (i) {
+ case LSM_OBJ_USER:
+ case LSM_OBJ_ROLE:
+ case LSM_OBJ_TYPE:
+ security_inode_getsecid(inode, &osid);
+ rc = security_filter_rule_match(osid,
+ rule->lsm[i].type,
+ AUDIT_EQUAL,
+ rule->lsm[i].rule,
+ NULL);
+ break;
+ case LSM_SUBJ_USER:
+ case LSM_SUBJ_ROLE:
+ case LSM_SUBJ_TYPE:
+ security_task_getsecid(tsk, &sid);
+ rc = security_filter_rule_match(sid,
+ rule->lsm[i].type,
+ AUDIT_EQUAL,
+ rule->lsm[i].rule,
+ NULL);
+ default:
+ break;
+ }
+ if (!rc)
+ return false;
+ }
return true;
}
@@ -112,9 +162,8 @@
/**
* ima_init_policy - initialize the default measure rules.
*
- * (Could use the default_rules directly, but in policy patch
* ima_measure points to either the measure_default_rules or the
- * the new measure_policy_rules.)
+ * the new measure_policy_rules.
*/
void ima_init_policy(void)
{
@@ -124,3 +173,241 @@
list_add_tail(&default_rules[i].list, &measure_default_rules);
ima_measure = &measure_default_rules;
}
+
+/**
+ * ima_update_policy - update default_rules with new measure rules
+ *
+ * Called on file .release to update the default rules with a complete new
+ * policy. Once updated, the policy is locked, no additional rules can be
+ * added to the policy.
+ */
+void ima_update_policy(void)
+{
+ const char *op = "policy_update";
+ const char *cause = "already exists";
+ int result = 1;
+ int audit_info = 0;
+
+ if (ima_measure == &measure_default_rules) {
+ ima_measure = &measure_policy_rules;
+ cause = "complete";
+ result = 0;
+ }
+ integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
+ NULL, op, cause, result, audit_info);
+}
+
+enum {
+ Opt_err = -1,
+ Opt_measure = 1, Opt_dont_measure,
+ Opt_obj_user, Opt_obj_role, Opt_obj_type,
+ Opt_subj_user, Opt_subj_role, Opt_subj_type,
+ Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
+};
+
+static match_table_t policy_tokens = {
+ {Opt_measure, "measure"},
+ {Opt_dont_measure, "dont_measure"},
+ {Opt_obj_user, "obj_user=%s"},
+ {Opt_obj_role, "obj_role=%s"},
+ {Opt_obj_type, "obj_type=%s"},
+ {Opt_subj_user, "subj_user=%s"},
+ {Opt_subj_role, "subj_role=%s"},
+ {Opt_subj_type, "subj_type=%s"},
+ {Opt_func, "func=%s"},
+ {Opt_mask, "mask=%s"},
+ {Opt_fsmagic, "fsmagic=%s"},
+ {Opt_uid, "uid=%s"},
+ {Opt_err, NULL}
+};
+
+static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
+ char *args, int lsm_rule, int audit_type)
+{
+ int result;
+
+ entry->lsm[lsm_rule].type = audit_type;
+ result = security_filter_rule_init(entry->lsm[lsm_rule].type,
+ AUDIT_EQUAL, args,
+ &entry->lsm[lsm_rule].rule);
+ return result;
+}
+
+static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
+{
+ struct audit_buffer *ab;
+ char *p;
+ int result = 0;
+
+ ab = audit_log_start(current->audit_context, GFP_KERNEL,
+ AUDIT_INTEGRITY_STATUS);
+
+ entry->action = -1;
+ while ((p = strsep(&rule, " \n")) != NULL) {
+ substring_t args[MAX_OPT_ARGS];
+ int token;
+ unsigned long lnum;
+
+ if (result < 0)
+ break;
+ if (!*p)
+ continue;
+ token = match_token(p, policy_tokens, args);
+ switch (token) {
+ case Opt_measure:
+ audit_log_format(ab, "%s ", "measure");
+ entry->action = MEASURE;
+ break;
+ case Opt_dont_measure:
+ audit_log_format(ab, "%s ", "dont_measure");
+ entry->action = DONT_MEASURE;
+ break;
+ case Opt_func:
+ audit_log_format(ab, "func=%s ", args[0].from);
+ if (strcmp(args[0].from, "PATH_CHECK") == 0)
+ entry->func = PATH_CHECK;
+ else if (strcmp(args[0].from, "FILE_MMAP") == 0)
+ entry->func = FILE_MMAP;
+ else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
+ entry->func = BPRM_CHECK;
+ else
+ result = -EINVAL;
+ if (!result)
+ entry->flags |= IMA_FUNC;
+ break;
+ case Opt_mask:
+ audit_log_format(ab, "mask=%s ", args[0].from);
+ if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
+ entry->mask = MAY_EXEC;
+ else if (strcmp(args[0].from, "MAY_WRITE") == 0)
+ entry->mask = MAY_WRITE;
+ else if (strcmp(args[0].from, "MAY_READ") == 0)
+ entry->mask = MAY_READ;
+ else if (strcmp(args[0].from, "MAY_APPEND") == 0)
+ entry->mask = MAY_APPEND;
+ else
+ result = -EINVAL;
+ if (!result)
+ entry->flags |= IMA_MASK;
+ break;
+ case Opt_fsmagic:
+ audit_log_format(ab, "fsmagic=%s ", args[0].from);
+ result = strict_strtoul(args[0].from, 16,
+ &entry->fsmagic);
+ if (!result)
+ entry->flags |= IMA_FSMAGIC;
+ break;
+ case Opt_uid:
+ audit_log_format(ab, "uid=%s ", args[0].from);
+ result = strict_strtoul(args[0].from, 10, &lnum);
+ if (!result) {
+ entry->uid = (uid_t) lnum;
+ if (entry->uid != lnum)
+ result = -EINVAL;
+ else
+ entry->flags |= IMA_UID;
+ }
+ break;
+ case Opt_obj_user:
+ audit_log_format(ab, "obj_user=%s ", args[0].from);
+ result = ima_lsm_rule_init(entry, args[0].from,
+ LSM_OBJ_USER,
+ AUDIT_OBJ_USER);
+ break;
+ case Opt_obj_role:
+ audit_log_format(ab, "obj_role=%s ", args[0].from);
+ result = ima_lsm_rule_init(entry, args[0].from,
+ LSM_OBJ_ROLE,
+ AUDIT_OBJ_ROLE);
+ break;
+ case Opt_obj_type:
+ audit_log_format(ab, "obj_type=%s ", args[0].from);
+ result = ima_lsm_rule_init(entry, args[0].from,
+ LSM_OBJ_TYPE,
+ AUDIT_OBJ_TYPE);
+ break;
+ case Opt_subj_user:
+ audit_log_format(ab, "subj_user=%s ", args[0].from);
+ result = ima_lsm_rule_init(entry, args[0].from,
+ LSM_SUBJ_USER,
+ AUDIT_SUBJ_USER);
+ break;
+ case Opt_subj_role:
+ audit_log_format(ab, "subj_role=%s ", args[0].from);
+ result = ima_lsm_rule_init(entry, args[0].from,
+ LSM_SUBJ_ROLE,
+ AUDIT_SUBJ_ROLE);
+ break;
+ case Opt_subj_type:
+ audit_log_format(ab, "subj_type=%s ", args[0].from);
+ result = ima_lsm_rule_init(entry, args[0].from,
+ LSM_SUBJ_TYPE,
+ AUDIT_SUBJ_TYPE);
+ break;
+ case Opt_err:
+ printk(KERN_INFO "%s: unknown token: %s\n",
+ __FUNCTION__, p);
+ break;
+ }
+ }
+ if (entry->action == UNKNOWN)
+ result = -EINVAL;
+
+ audit_log_format(ab, "res=%d", result);
+ audit_log_end(ab);
+ return result;
+}
+
+/**
+ * ima_parse_add_rule - add a rule to measure_policy_rules
+ * @rule - ima measurement policy rule
+ *
+ * Uses a mutex to protect the policy list from multiple concurrent writers.
+ * Returns 0 on success, an error code on failure.
+ */
+int ima_parse_add_rule(char *rule)
+{
+ const char *op = "add_rule";
+ struct ima_measure_rule_entry *entry;
+ int result = 0;
+ int audit_info = 0;
+
+ /* Prevent installed policy from changing */
+ if (ima_measure != &measure_default_rules) {
+ integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
+ NULL, op, "already exists",
+ -EACCES, audit_info);
+ return -EACCES;
+ }
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
+ NULL, op, "-ENOMEM", -ENOMEM, audit_info);
+ return -ENOMEM;
+ }
+
+ INIT_LIST_HEAD(&entry->list);
+
+ result = ima_parse_rule(rule, entry);
+ if (!result) {
+ mutex_lock(&ima_measure_mutex);
+ list_add_tail(&entry->list, &measure_policy_rules);
+ mutex_unlock(&ima_measure_mutex);
+ } else
+ kfree(entry);
+ return result;
+}
+
+/* ima_delete_rules called to cleanup invalid policy */
+void ima_delete_rules()
+{
+ struct ima_measure_rule_entry *entry, *tmp;
+
+ mutex_lock(&ima_measure_mutex);
+ list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
+ list_del(&entry->list);
+ kfree(entry);
+ }
+ mutex_unlock(&ima_measure_mutex);
+}