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>

4 files changed, 386 insertions, 4 deletions

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 2a761c8ac996..3d2b6ee778a0 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -47,3 +47,9 @@ config IMA_AUDIT
           auditing messages can be enabled with 'ima_audit=1' on
           the kernel command line.
 
+config IMA_LSM_RULES
+        bool
+        depends on IMA && (SECURITY_SELINUX || SECURITY_SMACK)
+        default y
+        help
+          Disabling this option will disregard LSM based policy rules
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 9c280cc73004..42706b554921 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -137,4 +137,28 @@ enum ima_hooks { PATH_CHECK = 1, FILE_MMAP, BPRM_CHECK };
 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask);
 void ima_init_policy(void);
 void ima_update_policy(void);
+int ima_parse_add_rule(char *);
+void ima_delete_rules(void);
+
+/* LSM based policy rules require audit */
+#ifdef CONFIG_IMA_LSM_RULES
+
+#define security_filter_rule_init security_audit_rule_init
+#define security_filter_rule_match security_audit_rule_match
+
+#else
+
+static inline int security_filter_rule_init(u32 field, u32 op, char *rulestr,
+                                            void **lsmrule)
+{
+        return -EINVAL;
+}
+
+static inline int security_filter_rule_match(u32 secid, u32 field, u32 op,
+                                             void *lsmrule,
+                                             struct audit_context *actx)
+{
+        return -EINVAL;
+}
+#endif /* CONFIG_IMA_LSM_RULES */
 #endif
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 4f25be768b50..95ef1caa64b5 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -19,9 +19,11 @@
 #include <linux/seq_file.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
+#include <linux/parser.h>
 
 #include "ima.h"
 
+static int valid_policy = 1;
 #define TMPBUFLEN 12
 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
                                      loff_t *ppos, atomic_long_t *val)
@@ -237,11 +239,66 @@ static struct file_operations ima_ascii_measurements_ops = {
         .release = seq_release,
 };
 
+static ssize_t ima_write_policy(struct file *file, const char __user *buf,
+                                size_t datalen, loff_t *ppos)
+{
+        char *data;
+        int rc;
+
+        if (datalen >= PAGE_SIZE)
+                return -ENOMEM;
+        if (*ppos != 0) {
+                /* No partial writes. */
+                return -EINVAL;
+        }
+        data = kmalloc(datalen + 1, GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        if (copy_from_user(data, buf, datalen)) {
+                kfree(data);
+                return -EFAULT;
+        }
+        *(data + datalen) = '\0';
+        rc = ima_parse_add_rule(data);
+        if (rc < 0) {
+                datalen = -EINVAL;
+                valid_policy = 0;
+        }
+
+        kfree(data);
+        return datalen;
+}
+
 static struct dentry *ima_dir;
 static struct dentry *binary_runtime_measurements;
 static struct dentry *ascii_runtime_measurements;
 static struct dentry *runtime_measurements_count;
 static struct dentry *violations;
+static struct dentry *ima_policy;
+
+/*
+ * ima_release_policy - start using the new measure policy rules.
+ *
+ * Initially, ima_measure points to the default policy rules, now
+ * point to the new policy rules, and remove the securityfs policy file.
+ */
+static int ima_release_policy(struct inode *inode, struct file *file)
+{
+        if (!valid_policy) {
+                ima_delete_rules();
+                return 0;
+        }
+        ima_update_policy();
+        securityfs_remove(ima_policy);
+        ima_policy = NULL;
+        return 0;
+}
+
+static struct file_operations ima_measure_policy_ops = {
+        .write = ima_write_policy,
+        .release = ima_release_policy
+};
 
 int ima_fs_init(void)
 {
@@ -276,13 +333,20 @@ int ima_fs_init(void)
         if (IS_ERR(violations))
                 goto out;
 
-        return 0;
+        ima_policy = securityfs_create_file("policy",
+                                            S_IRUSR | S_IRGRP | S_IWUSR,
+                                            ima_dir, NULL,
+                                            &ima_measure_policy_ops);
+        if (IS_ERR(ima_policy))
+                goto out;
 
+        return 0;
 out:
         securityfs_remove(runtime_measurements_count);
         securityfs_remove(ascii_runtime_measurements);
         securityfs_remove(binary_runtime_measurements);
         securityfs_remove(ima_dir);
+        securityfs_remove(ima_policy);
         return -1;
 }
 
@@ -293,4 +357,5 @@ void __exit ima_fs_cleanup(void)
         securityfs_remove(ascii_runtime_measurements);
         securityfs_remove(binary_runtime_measurements);
         securityfs_remove(ima_dir);
+        securityfs_remove(ima_policy);
 }
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 7c3d1ffb1472..bd453603e2c3 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 @@ struct ima_measure_rule_entry {
         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 struct ima_measure_rule_entry default_rules[] = {
 };
 
 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 @@ static bool ima_match_rules(struct ima_measure_rule_entry *rule,
                             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 @@ static bool ima_match_rules(struct ima_measure_rule_entry *rule,
                 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 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
 /**
  * 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 @@ void ima_init_policy(void)
                 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);
+}