[RFC PATCH v3 5/5] selinux: introduce kdbus access controls

Paul Moore
2015-10-07T23:08:48Z

Add the SELinux access control implementation for the new kdbus LSM
hooks using the new kdbus object class and the following permissions:

[NOTE: permissions below are based on kdbus code from Aug 2015]

* kdbus:impersonate
Send a different security label to kdbus peers.
* kdbus:fakecreds
Send different DAC credentials to kdbus peers.
* kdbus:fakepids
Send a different PID to kdbus peers.
* kdbus:owner
Act as a kdbus bus owner.
* kdbus:privileged
Act as a privileged endpoint.
* kdbus:activator
Act as a kdbus activator.
* kdbus:monitor
Act as a kdbus monitor.
* kdbus:policy_holder
Act as a kdbus policy holder.
* kdbus:connect
Create a new kdbus connection.
* kdbus:own
Own a kdbus service name.
* kdbus:talk
Talk between two kdbus endpoints.
* kdbus:see
See another kdbus endpoint.
* kdbus:see_name
See a kdbus service name.
* kdbus:see_notification
See a kdbus notification.

Signed-off-by: Paul Moore <pmoore@redhat.com>

---
ChangeLog:
- v3
* Ported to the 4.3-rc4 based kdbus tree
* Fix the missing NULL terminator in the kdbus obj class definition
- v2
* Add the selinux_kdbus_init_inode() hook
* Add some very basic info on the permissions to the description
* Add kdbus service name auditing in the AVC records
- v1
* Initial draft
---
security/selinux/hooks.c | 153 +++++++++++++++++++++++++++++++++++
security/selinux/include/classmap.h | 4 +
2 files changed, 155 insertions(+), 2 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e4369d8..5581990 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -9,8 +9,10 @@
* James Morris <jmorris@redhat.com>
*
* Copyright (C) 2001,2002 Networks Associates Technology, Inc.
- * Copyright (C) 2003-2008 Red Hat, Inc., James Morris <jmorris@redhat.com>
- * Eric Paris <eparis@redhat.com>
+ * Copyright (C) 2003-2008,2015 Red Hat, Inc.
+ * James Morris <jmorris@redhat.com>
+ * Eric Paris <eparis@redhat.com>
+ * Paul Moore <paul@paul-moore.com>
* Copyright (C) 2004-2005 Trusted Computer Solutions, Inc.
* <dgoeddel@trustedcs.com>
* Copyright (C) 2006, 2007, 2009 Hewlett-Packard Development Company, L.P.
@@ -2035,6 +2037,143 @@ static int selinux_binder_transfer_file(struct task_struct *from,
&ad);
}

+static int selinux_kdbus_conn_new(const struct cred *creds,
+ const struct kdbus_creds *fake_creds,
+ const struct kdbus_pids *fake_pids,
+ const char *fake_seclabel,
+ bool owner, bool privileged,
+ bool is_activator, bool is_monitor,
+ bool is_policy_holder)
+{
+ int rc;
+ u32 tsid = current_sid();
+ u32 av = KDBUS__CONNECT;
+
+ if (fake_creds)
+ av |= KDBUS__FAKECREDS;
+ if (fake_pids)
+ av |= KDBUS__FAKEPIDS;
+ if (owner)
+ av |= KDBUS__OWNER;
+ if (privileged)
+ av |= KDBUS__PRIVILEGED;
+ if (is_activator)
+ av |= KDBUS__ACTIVATOR;
+ if (is_monitor)
+ av |= KDBUS__MONITOR;
+ if (is_policy_holder)
+ av |= KDBUS__POLICY_HOLDER;
+
+ rc = avc_has_perm(tsid, cred_sid(creds), SECCLASS_KDBUS, av, NULL);
+ if (rc)
+ return rc;
+
+ if (fake_seclabel) {
+ u32 sid;
+ if (security_context_to_sid(fake_seclabel,
+ strlen(fake_seclabel),
+ &sid, GFP_KERNEL))
+ return -EINVAL;
+
+ rc = avc_has_perm(tsid, sid,
+ SECCLASS_KDBUS, KDBUS__IMPERSONATE, NULL);
+ }
+
+ return rc;
+}
+
+static int selinux_kdbus_own_name(const struct cred *creds, const char *name)
+{
+ int rc;
+ u32 name_sid;
+ struct common_audit_data ad;
+
+ rc = security_kdbus_sid(name, &name_sid);
+ if (rc)
+ return rc;
+
+ ad.type = LSM_AUDIT_DATA_KDBUS;
+ ad.u.kdbus_name = name;
+
+ return avc_has_perm(cred_sid(creds), name_sid,
+ SECCLASS_KDBUS, KDBUS__OWN, &ad);
+}
+
+static int selinux_kdbus_conn_talk(const struct cred *creds,
+ const struct cred *creds_to)
+{
+ return avc_has_perm(cred_sid(creds), cred_sid(creds_to),
+ SECCLASS_KDBUS, KDBUS__TALK, NULL);
+}
+
+static int selinux_kdbus_conn_see(const struct cred *creds,
+ const struct cred *creds_whom)
+{
+ return avc_has_perm(cred_sid(creds), cred_sid(creds_whom),
+ SECCLASS_KDBUS, KDBUS__SEE, NULL);
+}
+
+static int selinux_kdbus_conn_see_name(const struct cred *creds,
+ const char *name)
+{
+ int rc;
+ u32 name_sid;
+ struct common_audit_data ad;
+
+ rc = security_kdbus_sid(name, &name_sid);
+ if (rc)
+ return rc;
+
+ ad.type = LSM_AUDIT_DATA_KDBUS;
+ ad.u.kdbus_name = name;
+
+ return avc_has_perm(cred_sid(creds), name_sid,
+ SECCLASS_KDBUS, KDBUS__SEE_NAME, &ad);
+}
+
+static int selinux_kdbus_conn_see_notification(const struct cred *creds)
+{
+ return avc_has_perm(SECINITSID_KERNEL, cred_sid(creds),
+ SECCLASS_KDBUS, KDBUS__SEE_NOTIFICATION, NULL);
+}
+
+static int selinux_kdbus_proc_permission(const struct cred *creds,
+ struct pid *pid)
+{
+ int rc;
+ struct task_struct *task;
+
+ rcu_read_lock();
+ task = pid_task(pid, PIDTYPE_PID);
+ rc = avc_has_perm(cred_sid(creds), task_sid(task),
+ SECCLASS_PROCESS, PROCESS__GETATTR, NULL);
+ rcu_read_unlock();
+
+ return rc;
+}
+
+static int selinux_kdbus_init_inode(struct inode *inode,
+ const struct cred *creds)
+{
+ struct inode_security_struct *isec = inode->i_security;
+ u32 sid = cred_sid(creds);
+
+ /* XXX - this is very simple, e.g. no transitions, no special object
+ * class, etc. since this inode is basically an IPC socket ...
+ * however, is this too simple? do we want transitions? if we
+ * do, we should do the transition in kdbus_node_init() and not
+ * here so that endpoint is labeled correctly and not just this
+ * inode */
+
+ isec->inode = inode;
+ isec->task_sid = sid;
+ isec->sid = sid;
+ isec->sclass = SECCLASS_FILE;
+ isec->initialized = 1;
+
+ return 0;
+}
+
static int selinux_ptrace_access_check(struct task_struct *child,
unsigned int mode)
{
@@ -5862,6 +6001,16 @@ static struct security_hook_list selinux_hooks[] = {
LSM_HOOK_INIT(binder_transfer_binder, selinux_binder_transfer_binder),
LSM_HOOK_INIT(binder_transfer_file, selinux_binder_transfer_file),

+ LSM_HOOK_INIT(kdbus_conn_new, selinux_kdbus_conn_new),
+ LSM_HOOK_INIT(kdbus_own_name, selinux_kdbus_own_name),
+ LSM_HOOK_INIT(kdbus_conn_talk, selinux_kdbus_conn_talk),
+ LSM_HOOK_INIT(kdbus_conn_see_name, selinux_kdbus_conn_see_name),
+ LSM_HOOK_INIT(kdbus_conn_see, selinux_kdbus_conn_see),
+ LSM_HOOK_INIT(kdbus_conn_see_notification,
+ selinux_kdbus_conn_see_notification),
+ LSM_HOOK_INIT(kdbus_proc_permission, selinux_kdbus_proc_permission),
+ LSM_HOOK_INIT(kdbus_init_inode, selinux_kdbus_init_inode),
+
LSM_HOOK_INIT(ptrace_access_check, selinux_ptrace_access_check),
LSM_HOOK_INIT(ptrace_traceme, selinux_ptrace_traceme),
LSM_HOOK_INIT(capget, selinux_capget),
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 5a4eef5..95eb6c3 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -157,5 +157,9 @@ struct security_class_mapping secclass_map[] = {
{ COMMON_SOCK_PERMS, "attach_queue", NULL } },
{ "binder", { "impersonate", "call", "set_context_mgr", "transfer",
NULL } },
+ { "kdbus", { "impersonate", "fakecreds", "fakepids", "owner",
+ "privileged", "activator", "monitor", "policy_holder",
+ "connect", "own", "talk", "see", "see_name",
+ "see_notification", NULL } },
{ NULL }
};