Add security hooks to binder and implement the hooks for SELinux.

Add security hooks to the binder and implement the hooks for SELinux.
The security hooks enable security modules such as SELinux to implement
controls over binder IPC.  The security hooks include support for
controlling what process can become the binder context manager
(binder_set_context_mgr), controlling the ability of a process
to invoke a binder transaction/IPC to another process (binder_transaction),
controlling the ability a process to transfer a binder reference to
another process (binder_transfer_binder), and controlling the ability
of a process to transfer an open file to another process (binder_transfer_file).

This support is used by SE Android, http://selinuxproject.org/page/SEAndroid.

Change-Id: I34266b66320b6a3df9ac01833d7f94daf742920e
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 3d07507..c048624 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -38,6 +38,7 @@
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
 #include <linux/pid_namespace.h>
+#include <linux/security.h>
 
 #ifdef CONFIG_ANDROID_BINDER_IPC_32BIT
 #define BINDER_IPC_32BIT 1
@@ -1404,6 +1405,10 @@
 			return_error = BR_DEAD_REPLY;
 			goto err_dead_binder;
 		}
+		if (security_binder_transaction(proc->tsk, target_proc->tsk) < 0) {
+			return_error = BR_FAILED_REPLY;
+			goto err_invalid_target_handle;
+		}
 		if (!(tr->flags & TF_ONE_WAY) && thread->transaction_stack) {
 			struct binder_transaction *tmp;
 
@@ -1561,6 +1566,10 @@
 				return_error = BR_FAILED_REPLY;
 				goto err_binder_get_ref_for_node_failed;
 			}
+			if (security_binder_transfer_binder(proc->tsk, target_proc->tsk)) {
+				return_error = BR_FAILED_REPLY;
+				goto err_binder_get_ref_for_node_failed;
+			}
 			ref = binder_get_ref_for_node(target_proc, node);
 			if (ref == NULL) {
 				return_error = BR_FAILED_REPLY;
@@ -1591,6 +1600,10 @@
 				return_error = BR_FAILED_REPLY;
 				goto err_binder_get_ref_failed;
 			}
+			if (security_binder_transfer_binder(proc->tsk, target_proc->tsk)) {
+				return_error = BR_FAILED_REPLY;
+				goto err_binder_get_ref_failed;
+			}
 			if (ref->node->proc == target_proc) {
 				if (fp->type == BINDER_TYPE_HANDLE)
 					fp->type = BINDER_TYPE_BINDER;
@@ -1648,6 +1661,11 @@
 				return_error = BR_FAILED_REPLY;
 				goto err_fget_failed;
 			}
+			if (security_binder_transfer_file(proc->tsk, target_proc->tsk, file) < 0) {
+				fput(file);
+				return_error = BR_FAILED_REPLY;
+				goto err_get_unused_fd_failed;
+			}
 			target_fd = task_get_unused_fd_flags(target_proc, O_CLOEXEC);
 			if (target_fd < 0) {
 				fput(file);
@@ -2685,6 +2703,9 @@
 		ret = -EBUSY;
 		goto out;
 	}
+	ret = security_binder_set_context_mgr(proc->tsk);
+	if (ret < 0)
+		goto out;
 	if (uid_valid(binder_context_mgr_uid)) {
 		if (!uid_eq(binder_context_mgr_uid, curr_euid)) {
 			pr_err("BINDER_SET_CONTEXT_MGR bad uid %d != %d\n",
diff --git a/include/linux/security.h b/include/linux/security.h
index 4686491..17e1888 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1402,6 +1402,11 @@
 struct security_operations {
 	char name[SECURITY_NAME_MAX + 1];
 
+	int (*binder_set_context_mgr) (struct task_struct *mgr);
+	int (*binder_transaction) (struct task_struct *from, struct task_struct *to);
+	int (*binder_transfer_binder) (struct task_struct *from, struct task_struct *to);
+	int (*binder_transfer_file) (struct task_struct *from, struct task_struct *to, struct file *file);
+
 	int (*ptrace_access_check) (struct task_struct *child, unsigned int mode);
 	int (*ptrace_traceme) (struct task_struct *parent);
 	int (*capget) (struct task_struct *target,
@@ -1690,6 +1695,10 @@
 
 
 /* Security operations */
+int security_binder_set_context_mgr(struct task_struct *mgr);
+int security_binder_transaction(struct task_struct *from, struct task_struct *to);
+int security_binder_transfer_binder(struct task_struct *from, struct task_struct *to);
+int security_binder_transfer_file(struct task_struct *from, struct task_struct *to, struct file *file);
 int security_ptrace_access_check(struct task_struct *child, unsigned int mode);
 int security_ptrace_traceme(struct task_struct *parent);
 int security_capget(struct task_struct *target,
@@ -1869,6 +1878,26 @@
 	return 0;
 }
 
+static inline int security_binder_set_context_mgr(struct task_struct *mgr)
+{
+	return 0;
+}
+
+static inline int security_binder_transaction(struct task_struct *from, struct task_struct *to)
+{
+	return 0;
+}
+
+static inline int security_binder_transfer_binder(struct task_struct *from, struct task_struct *to)
+{
+	return 0;
+}
+
+static inline int security_binder_transfer_file(struct task_struct *from, struct task_struct *to, struct file *file)
+{
+	return 0;
+}
+
 static inline int security_ptrace_access_check(struct task_struct *child,
 					     unsigned int mode)
 {
diff --git a/security/capability.c b/security/capability.c
index 1728d4e..6e4fc77 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -12,6 +12,26 @@
 
 #include <linux/security.h>
 
+static int cap_binder_set_context_mgr(struct task_struct *mgr)
+{
+	return 0;
+}
+
+static int cap_binder_transaction(struct task_struct *from, struct task_struct *to)
+{
+	return 0;
+}
+
+static int cap_binder_transfer_binder(struct task_struct *from, struct task_struct *to)
+{
+	return 0;
+}
+
+static int cap_binder_transfer_file(struct task_struct *from, struct task_struct *to, struct file *file)
+{
+	return 0;
+}
+
 static int cap_syslog(int type)
 {
 	return 0;
@@ -903,6 +923,10 @@
 
 void __init security_fixup_ops(struct security_operations *ops)
 {
+	set_to_cap_if_null(ops, binder_set_context_mgr);
+	set_to_cap_if_null(ops, binder_transaction);
+	set_to_cap_if_null(ops, binder_transfer_binder);
+	set_to_cap_if_null(ops, binder_transfer_file);
 	set_to_cap_if_null(ops, ptrace_access_check);
 	set_to_cap_if_null(ops, ptrace_traceme);
 	set_to_cap_if_null(ops, capget);
diff --git a/security/security.c b/security/security.c
index a3dce87..d6ab2d2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -134,6 +134,26 @@
 
 /* Security operations */
 
+int security_binder_set_context_mgr(struct task_struct *mgr)
+{
+	return security_ops->binder_set_context_mgr(mgr);
+}
+
+int security_binder_transaction(struct task_struct *from, struct task_struct *to)
+{
+	return security_ops->binder_transaction(from, to);
+}
+
+int security_binder_transfer_binder(struct task_struct *from, struct task_struct *to)
+{
+	return security_ops->binder_transfer_binder(from, to);
+}
+
+int security_binder_transfer_file(struct task_struct *from, struct task_struct *to, struct file *file)
+{
+	return security_ops->binder_transfer_file(from, to, file);
+}
+
 int security_ptrace_access_check(struct task_struct *child, unsigned int mode)
 {
 #ifdef CONFIG_SECURITY_YAMA_STACKED
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 8908c36..a8de30b 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1844,6 +1844,67 @@
 
 /* Hook functions begin here. */
 
+static int selinux_binder_set_context_mgr(struct task_struct *mgr)
+{
+	u32 mysid = current_sid();
+	u32 mgrsid = task_sid(mgr);
+
+	return avc_has_perm(mysid, mgrsid, SECCLASS_BINDER, BINDER__SET_CONTEXT_MGR, NULL);
+}
+
+static int selinux_binder_transaction(struct task_struct *from, struct task_struct *to)
+{
+	u32 mysid = current_sid();
+	u32 fromsid = task_sid(from);
+	u32 tosid = task_sid(to);
+	int rc;
+
+	if (mysid != fromsid) {
+		rc = avc_has_perm(mysid, fromsid, SECCLASS_BINDER, BINDER__IMPERSONATE, NULL);
+		if (rc)
+			return rc;
+	}
+
+	return avc_has_perm(fromsid, tosid, SECCLASS_BINDER, BINDER__CALL, NULL);
+}
+
+static int selinux_binder_transfer_binder(struct task_struct *from, struct task_struct *to)
+{
+	u32 fromsid = task_sid(from);
+	u32 tosid = task_sid(to);
+	return avc_has_perm(fromsid, tosid, SECCLASS_BINDER, BINDER__TRANSFER, NULL);
+}
+
+static int selinux_binder_transfer_file(struct task_struct *from, struct task_struct *to, struct file *file)
+{
+	u32 sid = task_sid(to);
+	struct file_security_struct *fsec = file->f_security;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	struct inode_security_struct *isec = inode->i_security;
+	struct common_audit_data ad;
+	struct selinux_audit_data sad = {0,};
+	int rc;
+
+	ad.type = LSM_AUDIT_DATA_PATH;
+	ad.u.path = file->f_path;
+	ad.selinux_audit_data = &sad;
+
+	if (sid != fsec->sid) {
+		rc = avc_has_perm(sid, fsec->sid,
+				  SECCLASS_FD,
+				  FD__USE,
+				  &ad);
+		if (rc)
+			return rc;
+	}
+
+	if (unlikely(IS_PRIVATE(inode)))
+		return 0;
+
+	return avc_has_perm(sid, isec->sid, isec->sclass, file_to_av(file),
+			    &ad);
+}
+
 static int selinux_ptrace_access_check(struct task_struct *child,
 				     unsigned int mode)
 {
@@ -5556,6 +5617,11 @@
 static struct security_operations selinux_ops = {
 	.name =				"selinux",
 
+	.binder_set_context_mgr =	selinux_binder_set_context_mgr,
+	.binder_transaction =		selinux_binder_transaction,
+	.binder_transfer_binder =	selinux_binder_transfer_binder,
+	.binder_transfer_file =		selinux_binder_transfer_file,
+
 	.ptrace_access_check =		selinux_ptrace_access_check,
 	.ptrace_traceme =		selinux_ptrace_traceme,
 	.capget =			selinux_capget,
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 14d04e6..c32ff7b 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -151,5 +151,6 @@
 	{ "kernel_service", { "use_as_override", "create_files_as", NULL } },
 	{ "tun_socket",
 	  { COMMON_SOCK_PERMS, "attach_queue", NULL } },
+	{ "binder", { "impersonate", "call", "set_context_mgr", "transfer", NULL } },
 	{ NULL }
   };