ima: add appraise action keywords and default rules
Unlike the IMA measurement policy, the appraise policy can not be dependent
on runtime process information, such as the task uid, as the 'security.ima'
xattr is written on file close and must be updated each time the file changes,
regardless of the current task uid.
This patch extends the policy language with 'fowner', defines an appraise
policy, which appraises all files owned by root, and defines 'ima_appraise_tcb',
a new boot command line option, to enable the appraise policy.
Changelog v3:
- separate the measure from the appraise rules in order to support measuring
without appraising and appraising without measuring.
- change appraisal default for filesystems without xattr support to fail
- update default appraise policy for cgroups
Changelog v1:
- don't appraise RAMFS (Dmitry Kasatkin)
- merged rest of "ima: ima_must_appraise_or_measure API change" commit
(Dmtiry Kasatkin)
ima_must_appraise_or_measure() called ima_match_policy twice, which
searched the policy for a matching rule. Once for a matching measurement
rule and subsequently for an appraisal rule. Searching the policy twice
is unnecessary overhead, which could be noticeable with a large policy.
The new version of ima_must_appraise_or_measure() does everything in a
single iteration using a new version of ima_match_policy(). It returns
IMA_MEASURE, IMA_APPRAISE mask.
With the use of action mask only one efficient matching function
is enough. Removed other specific versions of matching functions.
Changelog:
- change 'owner' to 'fowner' to conform to the new LSM conditions posted by
Roberto Sassu.
- fix calls to ima_log_string()
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 3e22e17..0d6d60b 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -24,6 +24,7 @@
#define IMA_MASK 0x0002
#define IMA_FSMAGIC 0x0004
#define IMA_UID 0x0008
+#define IMA_FOWNER 0x0010
#define UNKNOWN 0
#define MEASURE 1 /* same as IMA_MEASURE */
@@ -38,7 +39,7 @@
LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
};
-struct ima_measure_rule_entry {
+struct ima_rule_entry {
struct list_head list;
int action;
unsigned int flags;
@@ -46,6 +47,7 @@
int mask;
unsigned long fsmagic;
uid_t uid;
+ uid_t fowner;
struct {
void *rule; /* LSM file metadata specific */
int type; /* audit type */
@@ -54,7 +56,7 @@
/*
* Without LSM specific knowledge, the default policy can only be
- * written in terms of .action, .func, .mask, .fsmagic, and .uid
+ * written in terms of .action, .func, .mask, .fsmagic, .uid, and .fowner
*/
/*
@@ -63,7 +65,7 @@
* normal users can easily run the machine out of memory simply building
* and running executables.
*/
-static struct ima_measure_rule_entry default_rules[] = {
+static struct ima_rule_entry default_rules[] = {
{.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
{.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
@@ -81,19 +83,41 @@
.flags = IMA_FUNC | IMA_MASK | IMA_UID},
};
-static LIST_HEAD(measure_default_rules);
-static LIST_HEAD(measure_policy_rules);
-static struct list_head *ima_measure;
+static struct ima_rule_entry default_appraise_rules[] = {
+ {.action = DONT_APPRAISE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = RAMFS_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = DEVPTS_SUPER_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = BINFMTFS_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = DONT_APPRAISE,.fsmagic = CGROUP_SUPER_MAGIC,.flags = IMA_FSMAGIC},
+ {.action = APPRAISE,.fowner = 0,.flags = IMA_FOWNER},
+};
-static DEFINE_MUTEX(ima_measure_mutex);
+static LIST_HEAD(ima_default_rules);
+static LIST_HEAD(ima_policy_rules);
+static struct list_head *ima_rules;
+
+static DEFINE_MUTEX(ima_rules_mutex);
static bool ima_use_tcb __initdata;
-static int __init default_policy_setup(char *str)
+static int __init default_measure_policy_setup(char *str)
{
ima_use_tcb = 1;
return 1;
}
-__setup("ima_tcb", default_policy_setup);
+__setup("ima_tcb", default_measure_policy_setup);
+
+static bool ima_use_appraise_tcb __initdata;
+static int __init default_appraise_policy_setup(char *str)
+{
+ ima_use_appraise_tcb = 1;
+ return 1;
+}
+__setup("ima_appraise_tcb", default_appraise_policy_setup);
/**
* ima_match_rules - determine whether an inode matches the measure rule.
@@ -104,7 +128,7 @@
*
* Returns true on rule match, false on failure.
*/
-static bool ima_match_rules(struct ima_measure_rule_entry *rule,
+static bool ima_match_rules(struct ima_rule_entry *rule,
struct inode *inode, enum ima_hooks func, int mask)
{
struct task_struct *tsk = current;
@@ -120,6 +144,8 @@
return false;
if ((rule->flags & IMA_UID) && rule->uid != cred->uid)
return false;
+ if ((rule->flags & IMA_FOWNER) && rule->fowner != inode->i_uid)
+ return false;
for (i = 0; i < MAX_LSM_RULES; i++) {
int rc = 0;
u32 osid, sid;
@@ -172,10 +198,10 @@
int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
int flags)
{
- struct ima_measure_rule_entry *entry;
+ struct ima_rule_entry *entry;
int action = 0, actmask = flags | (flags << 1);
- list_for_each_entry(entry, ima_measure, list) {
+ list_for_each_entry(entry, ima_rules, list) {
if (!(entry->action & actmask))
continue;
@@ -196,22 +222,31 @@
/**
* ima_init_policy - initialize the default measure rules.
*
- * ima_measure points to either the measure_default_rules or the
- * the new measure_policy_rules.
+ * ima_rules points to either the ima_default_rules or the
+ * the new ima_policy_rules.
*/
void __init ima_init_policy(void)
{
- int i, entries;
+ int i, measure_entries, appraise_entries;
/* if !ima_use_tcb set entries = 0 so we load NO default rules */
- if (ima_use_tcb)
- entries = ARRAY_SIZE(default_rules);
- else
- entries = 0;
+ measure_entries = ima_use_tcb ? ARRAY_SIZE(default_rules) : 0;
+ appraise_entries = ima_use_appraise_tcb ?
+ ARRAY_SIZE(default_appraise_rules) : 0;
+
+ for (i = 0; i < measure_entries + appraise_entries; i++) {
+ if (i < measure_entries)
+ list_add_tail(&default_rules[i].list,
+ &ima_default_rules);
+ else {
+ int j = i - measure_entries;
- for (i = 0; i < entries; i++)
- list_add_tail(&default_rules[i].list, &measure_default_rules);
- ima_measure = &measure_default_rules;
+ list_add_tail(&default_appraise_rules[j].list,
+ &ima_default_rules);
+ }
+ }
+
+ ima_rules = &ima_default_rules;
}
/**
@@ -228,8 +263,8 @@
int result = 1;
int audit_info = 0;
- if (ima_measure == &measure_default_rules) {
- ima_measure = &measure_policy_rules;
+ if (ima_rules == &ima_default_rules) {
+ ima_rules = &ima_policy_rules;
cause = "complete";
result = 0;
}
@@ -240,14 +275,17 @@
enum {
Opt_err = -1,
Opt_measure = 1, Opt_dont_measure,
+ Opt_appraise, Opt_dont_appraise,
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
+ Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner
};
static match_table_t policy_tokens = {
{Opt_measure, "measure"},
{Opt_dont_measure, "dont_measure"},
+ {Opt_appraise, "appraise"},
+ {Opt_dont_appraise, "dont_appraise"},
{Opt_obj_user, "obj_user=%s"},
{Opt_obj_role, "obj_role=%s"},
{Opt_obj_type, "obj_type=%s"},
@@ -258,10 +296,11 @@
{Opt_mask, "mask=%s"},
{Opt_fsmagic, "fsmagic=%s"},
{Opt_uid, "uid=%s"},
+ {Opt_fowner, "fowner=%s"},
{Opt_err, NULL}
};
-static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
+static int ima_lsm_rule_init(struct ima_rule_entry *entry,
char *args, int lsm_rule, int audit_type)
{
int result;
@@ -285,7 +324,7 @@
audit_log_format(ab, " ");
}
-static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
+static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
{
struct audit_buffer *ab;
char *p;
@@ -294,6 +333,7 @@
ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
entry->uid = -1;
+ entry->fowner = -1;
entry->action = UNKNOWN;
while ((p = strsep(&rule, " \t")) != NULL) {
substring_t args[MAX_OPT_ARGS];
@@ -322,11 +362,27 @@
entry->action = DONT_MEASURE;
break;
+ case Opt_appraise:
+ ima_log_string(ab, "action", "appraise");
+
+ if (entry->action != UNKNOWN)
+ result = -EINVAL;
+
+ entry->action = APPRAISE;
+ break;
+ case Opt_dont_appraise:
+ ima_log_string(ab, "action", "dont_appraise");
+
+ if (entry->action != UNKNOWN)
+ result = -EINVAL;
+
+ entry->action = DONT_APPRAISE;
+ break;
case Opt_func:
ima_log_string(ab, "func", args[0].from);
if (entry->func)
- result = -EINVAL;
+ result = -EINVAL;
if (strcmp(args[0].from, "FILE_CHECK") == 0)
entry->func = FILE_CHECK;
@@ -391,6 +447,23 @@
entry->flags |= IMA_UID;
}
break;
+ case Opt_fowner:
+ ima_log_string(ab, "fowner", args[0].from);
+
+ if (entry->fowner != -1) {
+ result = -EINVAL;
+ break;
+ }
+
+ result = strict_strtoul(args[0].from, 10, &lnum);
+ if (!result) {
+ entry->fowner = (uid_t) lnum;
+ if (entry->fowner != lnum)
+ result = -EINVAL;
+ else
+ entry->flags |= IMA_FOWNER;
+ }
+ break;
case Opt_obj_user:
ima_log_string(ab, "obj_user", args[0].from);
result = ima_lsm_rule_init(entry, args[0].from,
@@ -442,7 +515,7 @@
}
/**
- * ima_parse_add_rule - add a rule to measure_policy_rules
+ * ima_parse_add_rule - add a rule to ima_policy_rules
* @rule - ima measurement policy rule
*
* Uses a mutex to protect the policy list from multiple concurrent writers.
@@ -452,12 +525,12 @@
{
const char *op = "update_policy";
char *p;
- struct ima_measure_rule_entry *entry;
+ struct ima_rule_entry *entry;
ssize_t result, len;
int audit_info = 0;
/* Prevent installed policy from changing */
- if (ima_measure != &measure_default_rules) {
+ if (ima_rules != &ima_default_rules) {
integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
NULL, op, "already exists",
-EACCES, audit_info);
@@ -490,9 +563,9 @@
return result;
}
- mutex_lock(&ima_measure_mutex);
- list_add_tail(&entry->list, &measure_policy_rules);
- mutex_unlock(&ima_measure_mutex);
+ mutex_lock(&ima_rules_mutex);
+ list_add_tail(&entry->list, &ima_policy_rules);
+ mutex_unlock(&ima_rules_mutex);
return len;
}
@@ -500,12 +573,12 @@
/* ima_delete_rules called to cleanup invalid policy */
void ima_delete_rules(void)
{
- struct ima_measure_rule_entry *entry, *tmp;
+ struct ima_rule_entry *entry, *tmp;
- mutex_lock(&ima_measure_mutex);
- list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
+ mutex_lock(&ima_rules_mutex);
+ list_for_each_entry_safe(entry, tmp, &ima_policy_rules, list) {
list_del(&entry->list);
kfree(entry);
}
- mutex_unlock(&ima_measure_mutex);
+ mutex_unlock(&ima_rules_mutex);
}