ima: update builtin policies

This patch defines a builtin measurement policy "tcb", similar to the
existing "ima_tcb", but with additional rules to also measure files
based on the effective uid and to measure files opened with the "read"
mode bit set (eg. read, read-write).

Changing the builtin "ima_tcb" policy could potentially break existing
users.  Instead of defining a new separate boot command line option each
time the builtin measurement policy is modified, this patch defines a
single generic boot command line option "ima_policy=" to specify the
builtin policy and deprecates the use of the builtin ima_tcb policy.

[The "ima_policy=" boot command line option is based on Roberto Sassu's
"ima: added new policy type exec" patch.]

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Dr. Greg Wettstein <gw@idfusion.org>
Cc: stable@vger.kernel.org

1 files changed, 56 insertions, 9 deletions

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index b3a2038ed424..3997e206f82d 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -44,6 +44,8 @@ enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
         LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
 };
 
+enum policy_types { ORIGINAL_TCB = 1, DEFAULT_TCB };
+
 struct ima_rule_entry {
         struct list_head list;
         int action;
@@ -72,7 +74,7 @@ struct ima_rule_entry {
  * normal users can easily run the machine out of memory simply building
  * and running executables.
  */
-static struct ima_rule_entry default_rules[] = {
+static struct ima_rule_entry dont_measure_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},
@@ -83,13 +85,29 @@ static struct ima_rule_entry default_rules[] = {
         {.action = DONT_MEASURE, .fsmagic = SELINUX_MAGIC, .flags = IMA_FSMAGIC},
         {.action = DONT_MEASURE, .fsmagic = CGROUP_SUPER_MAGIC,
          .flags = IMA_FSMAGIC},
-        {.action = DONT_MEASURE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC},
+        {.action = DONT_MEASURE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC}
+};
+
+static struct ima_rule_entry original_measurement_rules[] = {
+        {.action = MEASURE, .func = MMAP_CHECK, .mask = MAY_EXEC,
+         .flags = IMA_FUNC | IMA_MASK},
+        {.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
+         .flags = IMA_FUNC | IMA_MASK},
+        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
+         .uid = GLOBAL_ROOT_UID, .flags = IMA_FUNC | IMA_MASK | IMA_UID},
+        {.action = MEASURE, .func = MODULE_CHECK, .flags = IMA_FUNC},
+        {.action = MEASURE, .func = FIRMWARE_CHECK, .flags = IMA_FUNC},
+};
+
+static struct ima_rule_entry default_measurement_rules[] = {
         {.action = MEASURE, .func = MMAP_CHECK, .mask = MAY_EXEC,
          .flags = IMA_FUNC | IMA_MASK},
         {.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
          .flags = IMA_FUNC | IMA_MASK},
-        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ, .uid = GLOBAL_ROOT_UID,
-         .flags = IMA_FUNC | IMA_MASK | IMA_UID},
+        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
+         .uid = GLOBAL_ROOT_UID, .flags = IMA_FUNC | IMA_INMASK | IMA_EUID},
+        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
+         .uid = GLOBAL_ROOT_UID, .flags = IMA_FUNC | IMA_INMASK | IMA_UID},
         {.action = MEASURE, .func = MODULE_CHECK, .flags = IMA_FUNC},
         {.action = MEASURE, .func = FIRMWARE_CHECK, .flags = IMA_FUNC},
 };
@@ -121,14 +139,29 @@ static struct list_head *ima_rules;
 
 static DEFINE_MUTEX(ima_rules_mutex);
 
-static bool ima_use_tcb __initdata;
+static int ima_policy __initdata;
 static int __init default_measure_policy_setup(char *str)
 {
-        ima_use_tcb = 1;
+        if (ima_policy)
+                return 1;
+
+        ima_policy = ORIGINAL_TCB;
         return 1;
 }
 __setup("ima_tcb", default_measure_policy_setup);
 
+static int __init policy_setup(char *str)
+{
+        if (ima_policy)
+                return 1;
+
+        if (strcmp(str, "tcb") == 0)
+                ima_policy = DEFAULT_TCB;
+
+        return 1;
+}
+__setup("ima_policy=", policy_setup);
+
 static bool ima_use_appraise_tcb __initdata;
 static int __init default_appraise_policy_setup(char *str)
 {
@@ -352,13 +385,27 @@ void __init ima_init_policy(void)
 {
         int i, measure_entries, appraise_entries;
 
-        /* if !ima_use_tcb set entries = 0 so we load NO default rules */
-        measure_entries = ima_use_tcb ? ARRAY_SIZE(default_rules) : 0;
+        /* if !ima_policy set entries = 0 so we load NO default rules */
+        measure_entries = ima_policy ? ARRAY_SIZE(dont_measure_rules) : 0;
         appraise_entries = ima_use_appraise_tcb ?
                          ARRAY_SIZE(default_appraise_rules) : 0;
 
         for (i = 0; i < measure_entries; i++)
-                list_add_tail(&default_rules[i].list, &ima_default_rules);
+                list_add_tail(&dont_measure_rules[i].list, &ima_default_rules);
+
+        switch (ima_policy) {
+        case ORIGINAL_TCB:
+                for (i = 0; i < ARRAY_SIZE(original_measurement_rules); i++)
+                        list_add_tail(&original_measurement_rules[i].list,
+                                      &ima_default_rules);
+                break;
+        case DEFAULT_TCB:
+                for (i = 0; i < ARRAY_SIZE(default_measurement_rules); i++)
+                        list_add_tail(&default_measurement_rules[i].list,
+                                      &ima_default_rules);
+        default:
+                break;
+        }
 
         for (i = 0; i < appraise_entries; i++) {
                 list_add_tail(&default_appraise_rules[i].list,