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.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Change-Id: I9a64a87825df2e60b9c51400377af4a9cd1c4049

4 files changed, 109 insertions, 0 deletions

diff --git a/security/capability.c b/security/capability.c
index bbb51156261..ac5793cd3cd 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;
@@ -874,6 +894,10 @@ static void cap_audit_rule_free(void *lsmrule)
 
 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 f19f9456f16..6db15aa19a7 100644
--- a/security/security.c
+++ b/security/security.c
@@ -127,6 +127,26 @@ int __init register_security(struct security_operations *ops)
 
 /* 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)
 {
 	return security_ops->ptrace_access_check(child, mode);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 20219ef5439..49ddc59153a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1805,6 +1805,65 @@ static inline u32 open_file_to_av(struct file *file)
 
 /* 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;
+	int rc;
+
+	COMMON_AUDIT_DATA_INIT(&ad, PATH);
+	ad.u.path = file->f_path;
+
+	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)
 {
@@ -5457,6 +5516,11 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
 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 b8c53723e09..4a4a9aebca9 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -149,5 +149,6 @@ struct security_class_mapping secclass_map[] = {
 	{ "kernel_service", { "use_as_override", "create_files_as", NULL } },
 	{ "tun_socket",
 	  { COMMON_SOCK_PERMS, NULL } },
+	{ "binder", { "impersonate", "call", "set_context_mgr", "transfer", NULL } },
 	{ NULL }
   };