ima: added policy support for 'security.ima' type
Dmitry Kasatkin [Fri, 8 Jun 2012 10:58:49 +0000 (13:58 +0300)]
The 'security.ima' extended attribute may contain either the file data's
hash or a digital signature.  This patch adds support for requiring a
specific extended attribute type.  It extends the IMA policy with a new
keyword 'appraise_type=imasig'.  (Default is hash.)

Changelog v2:
- Fixed Documentation/ABI/testing/ima_policy option syntax
Changelog v1:
- Differentiate between 'required' vs. 'actual' extended attribute

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Documentation/ABI/testing/ima_policy
security/integrity/ima/ima_appraise.c
security/integrity/ima/ima_main.c
security/integrity/ima/ima_policy.c
security/integrity/integrity.h

index 6a0fc80..de16de3 100644 (file)
@@ -18,10 +18,11 @@ Description:
                rule format: action [condition ...]
 
                action: measure | dont_measure | appraise | dont_appraise | audit
-               condition:= base | lsm
+               condition:= base | lsm  [option]
                        base:   [[func=] [mask=] [fsmagic=] [uid=] [fowner]]
                        lsm:    [[subj_user=] [subj_role=] [subj_type=]
                                 [obj_user=] [obj_role=] [obj_type=]]
+                       option: [[appraise_type=]]
 
                base:   func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
                        mask:= [MAY_READ] [MAY_WRITE] [MAY_APPEND] [MAY_EXEC]
@@ -29,6 +30,7 @@ Description:
                        uid:= decimal value
                        fowner:=decimal value
                lsm:    are LSM specific
+               option: appraise_type:= [imasig]
 
                default policy:
                        # PROC_SUPER_MAGIC
index fa675c9..8004332 100644 (file)
@@ -102,6 +102,11 @@ int ima_appraise_measurement(struct integrity_iint_cache *iint,
 
        switch (xattr_value->type) {
        case IMA_XATTR_DIGEST:
+               if (iint->flags & IMA_DIGSIG_REQUIRED) {
+                       cause = "IMA signature required";
+                       status = INTEGRITY_FAIL;
+                       break;
+               }
                rc = memcmp(xattr_value->digest, iint->ima_xattr.digest,
                            IMA_DIGEST_SIZE);
                if (rc) {
index cd00ba3..3cdd787 100644 (file)
@@ -169,6 +169,7 @@ static int process_measurement(struct file *file, const char *filename,
         * (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED,
         *  IMA_AUDIT, IMA_AUDITED) */
        iint->flags |= action;
+       action &= IMA_DO_MASK;
        action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 
        /* Nothing to do, just return existing appraised status */
index 9519453..1a2543a 100644 (file)
@@ -245,6 +245,8 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
                if (!ima_match_rules(entry, inode, func, mask))
                        continue;
 
+               action |= entry->flags & IMA_ACTION_FLAGS;
+
                action |= entry->action & IMA_DO_MASK;
                if (entry->action & IMA_DO_MASK)
                        actmask &= ~(entry->action | entry->action << 1);
@@ -318,7 +320,8 @@ enum {
        Opt_audit,
        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_fowner
+       Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner,
+       Opt_appraise_type
 };
 
 static match_table_t policy_tokens = {
@@ -338,6 +341,7 @@ static match_table_t policy_tokens = {
        {Opt_fsmagic, "fsmagic=%s"},
        {Opt_uid, "uid=%s"},
        {Opt_fowner, "fowner=%s"},
+       {Opt_appraise_type, "appraise_type=%s"},
        {Opt_err, NULL}
 };
 
@@ -560,6 +564,18 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
                                                   LSM_SUBJ_TYPE,
                                                   AUDIT_SUBJ_TYPE);
                        break;
+               case Opt_appraise_type:
+                       if (entry->action != APPRAISE) {
+                               result = -EINVAL;
+                               break;
+                       }
+
+                       ima_log_string(ab, "appraise_type", args[0].from);
+                       if ((strcmp(args[0].from, "imasig")) == 0)
+                               entry->flags |= IMA_DIGSIG_REQUIRED;
+                       else
+                               result = -EINVAL;
+                       break;
                case Opt_err:
                        ima_log_string(ab, "UNKNOWN", p);
                        result = -EINVAL;
index 0a298de..9334691 100644 (file)
@@ -26,7 +26,9 @@
 #define IMA_AUDITED            0x0080
 
 /* iint cache flags */
+#define IMA_ACTION_FLAGS       0xff00
 #define IMA_DIGSIG             0x0100
+#define IMA_DIGSIG_REQUIRED    0x0200
 
 #define IMA_DO_MASK            (IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT)
 #define IMA_DONE_MASK          (IMA_MEASURED | IMA_APPRAISED | IMA_AUDITED \