Some hardening of isolated processes by restricting access to services.

Services now must explicitly opt in to being accessed by isolated
processes.  Currently only the activity manager and surface flinger
allow this.  Activity manager is needed so that we can actually
bring up the process; SurfaceFlinger is needed to be able to get the
display information for creating the Configuration.  The SurfaceFlinger
should be safe because the app doesn't have access to the window
manager so can't actually get a surface to do anything with.

The activity manager now protects most of its entry points against
isolated processes.

Change-Id: I0dad8cb2c873575c4c7659c3c2a7eda8e98f46b0

1 files changed, 18 insertions, 5 deletions

diff --git a/cmds/servicemanager/service_manager.c b/cmds/servicemanager/service_manager.c
index 4ed2489..cfc2d16 100644
--- a/cmds/servicemanager/service_manager.c
+++ b/cmds/servicemanager/service_manager.c
@@ -90,6 +90,7 @@ struct svcinfo
     struct svcinfo *next;
     void *ptr;
     struct binder_death death;
+    int allow_isolated;
     unsigned len;
     uint16_t name[0];
 };
@@ -125,13 +126,21 @@ uint16_t svcmgr_id[] = {
 };
   
 
-void *do_find_service(struct binder_state *bs, uint16_t *s, unsigned len)
+void *do_find_service(struct binder_state *bs, uint16_t *s, unsigned len, unsigned uid)
 {
     struct svcinfo *si;
     si = find_svc(s, len);
 
 //    ALOGI("check_service('%s') ptr = %p\n", str8(s), si ? si->ptr : 0);
     if (si && si->ptr) {
+        if (!si->allow_isolated) {
+            // If this service doesn't allow access from isolated processes,
+            // then check the uid to see if it is isolated.
+            unsigned appid = uid % AID_USER;
+            if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END) {
+                return 0;
+            }
+        }
         return si->ptr;
     } else {
         return 0;
@@ -140,10 +149,11 @@ void *do_find_service(struct binder_state *bs, uint16_t *s, unsigned len)
 
 int do_add_service(struct binder_state *bs,
                    uint16_t *s, unsigned len,
-                   void *ptr, unsigned uid)
+                   void *ptr, unsigned uid, int allow_isolated)
 {
     struct svcinfo *si;
-//    ALOGI("add_service('%s',%p) uid=%d\n", str8(s), ptr, uid);
+    //ALOGI("add_service('%s',%p,%s) uid=%d\n", str8(s), ptr,
+    //        allow_isolated ? "allow_isolated" : "!allow_isolated", uid);
 
     if (!ptr || (len == 0) || (len > 127))
         return -1;
@@ -175,6 +185,7 @@ int do_add_service(struct binder_state *bs,
         si->name[len] = '\0';
         si->death.func = svcinfo_death;
         si->death.ptr = si;
+        si->allow_isolated = allow_isolated;
         si->next = svclist;
         svclist = si;
     }
@@ -194,6 +205,7 @@ int svcmgr_handler(struct binder_state *bs,
     unsigned len;
     void *ptr;
     uint32_t strict_policy;
+    int allow_isolated;
 
 //    ALOGI("target=%p code=%d pid=%d uid=%d\n",
 //         txn->target, txn->code, txn->sender_pid, txn->sender_euid);
@@ -217,7 +229,7 @@ int svcmgr_handler(struct binder_state *bs,
     case SVC_MGR_GET_SERVICE:
     case SVC_MGR_CHECK_SERVICE:
         s = bio_get_string16(msg, &len);
-        ptr = do_find_service(bs, s, len);
+        ptr = do_find_service(bs, s, len, txn->sender_euid);
         if (!ptr)
             break;
         bio_put_ref(reply, ptr);
@@ -226,7 +238,8 @@ int svcmgr_handler(struct binder_state *bs,
     case SVC_MGR_ADD_SERVICE:
         s = bio_get_string16(msg, &len);
         ptr = bio_get_ref(msg);
-        if (do_add_service(bs, s, len, ptr, txn->sender_euid))
+        allow_isolated = bio_get_uint32(msg) ? 1 : 0;
+        if (do_add_service(bs, s, len, ptr, txn->sender_euid, allow_isolated))
             return -1;
         break;