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Message-Id: <20200930094934.32144-4-richard_c_haines@btinternet.com>
Date: Wed, 30 Sep 2020 10:49:34 +0100
From: Richard Haines <richard_c_haines@...nternet.com>
To: selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
osmocom-net-gprs@...ts.osmocom.org, netdev@...r.kernel.org
Cc: stephen.smalley.work@...il.com, paul@...l-moore.com,
pablo@...filter.org, laforge@...monks.org, jmorris@...ei.org,
Richard Haines <richard_c_haines@...nternet.com>
Subject: [PATCH 3/3] selinux: Add SELinux GTP support
The SELinux GTP implementation is explained in:
Documentation/security/GTP.rst
Signed-off-by: Richard Haines <richard_c_haines@...nternet.com>
---
Documentation/security/GTP.rst | 61 ++++++++++++++++++++++++++
security/selinux/hooks.c | 66 +++++++++++++++++++++++++++++
security/selinux/include/classmap.h | 2 +
security/selinux/include/objsec.h | 4 ++
4 files changed, 133 insertions(+)
diff --git a/Documentation/security/GTP.rst b/Documentation/security/GTP.rst
index c748587ec..433fcb688 100644
--- a/Documentation/security/GTP.rst
+++ b/Documentation/security/GTP.rst
@@ -15,6 +15,9 @@ For security module support, three GTP specific hooks have been implemented::
security_gtp_dev_free()
security_gtp_dev_cmd()
+The usage of these hooks are described below with the SELinux implementation
+described in the `GTP SELinux Support`_ chapter.
+
security_gtp_dev_alloc()
~~~~~~~~~~~~~~~~~~~~~~
@@ -37,3 +40,61 @@ zero on success, negative values on failure. The commands are based on values
from ``include/uapi/linux/gtp.h`` as follows::
``enum gtp_genl_cmds { GTP_CMD_NEWPDP, GTP_CMD_DELPDP, GTP_CMD_GETPDP };``
+
+
+GTP SELinux Support
+===================
+
+Policy Statements
+-----------------
+The following class and permissions to support GTP are available within the
+kernel::
+
+ class gtp { add del get }
+
+The permissions are described in the sections that follow.
+
+
+Security Hooks
+--------------
+
+The `GTP LSM Support`_ chapter above describes the following GTP security
+hooks with the SELinux specifics expanded below::
+
+ security_gtp_dev_alloc -> selinux_gtp_dev_alloc_security(gtp)
+ security_gtp_dev_free -> selinux_gtp_dev_free_security(gtp)
+ security_gtp_dev_cmd -> selinux_gtp_dev_cmd(gtp, cmd)
+
+
+selinux_gtp_dev_alloc_security()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Allocates a security structure for a GTP device provided the caller has the
+``gtp { add }`` permission. Can return errors ``-ENOMEM`` or ``-EACCES``.
+Returns zero if the security structure has been allocated.
+
+
+selinux_gtp_dev_free_security()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Frees a security structure for a GTP device provided the caller has the
+``gtp { del }`` permission. Can return error ``-EACCES``. Returns zero if the
+security structure has been freed.
+
+
+selinux_gtp_dev_cmd()
+~~~~~~~~~~~~~~~~~~~~~
+Validate if the caller (current SID) and the GTP device SID have the required
+permission to perform the operation. The GTP/SELinux permission map is
+as follow::
+
+ GTP_CMD_NEWPDP = gtp { add }
+ GTP_CMD_DELPDP = gtp { del }
+ GTP_CMD_GETPDP = gtp { get }
+
+Returns ``-EACCES`` if denied or zero if allowed.
+
+NOTES::
+ 1) If the GTP device has the ``{ add }`` permission it can add device and
+ also add PDP's (packet data protocol).
+
+ 2) If the GTP device has the ``{ del }`` permission it can delete a device
+ and also delete PDP's.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index d6b182c11..5229a4f20 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -91,6 +91,7 @@
#include <uapi/linux/mount.h>
#include <linux/fsnotify.h>
#include <linux/fanotify.h>
+#include <net/gtp.h>
#include "avc.h"
#include "objsec.h"
@@ -5520,6 +5521,68 @@ static int selinux_tun_dev_open(void *security)
return 0;
}
+static int selinux_gtp_dev_alloc_security(struct gtp_dev *gtp)
+{
+ struct gtp_security_struct *gtpsec;
+ u32 sid = current_sid();
+ int err;
+
+ err = avc_has_perm(&selinux_state, sid, sid,
+ SECCLASS_GTP, GTP__ADD, NULL);
+ if (err < 0)
+ return err;
+
+ gtpsec = kzalloc(sizeof(*gtpsec), GFP_KERNEL);
+ if (!gtpsec)
+ return -ENOMEM;
+
+ gtpsec->sid = sid;
+ gtp->security = gtpsec;
+
+ return 0;
+}
+
+static int selinux_gtp_dev_free_security(struct gtp_dev *gtp)
+{
+ struct gtp_security_struct *gtpsec = gtp->security;
+ u32 sid = current_sid();
+ int err;
+
+ err = avc_has_perm(&selinux_state, sid, gtpsec->sid,
+ SECCLASS_GTP, GTP__DEL, NULL);
+ if (err < 0)
+ return err;
+
+ gtp->security = NULL;
+ kfree(gtpsec);
+
+ return 0;
+}
+
+static int selinux_gtp_dev_cmd(struct gtp_dev *gtp, enum gtp_genl_cmds cmd)
+{
+ struct gtp_security_struct *gtpsec = gtp->security;
+ u32 perm, sid = current_sid();
+
+ switch (cmd) {
+ case GTP_CMD_NEWPDP:
+ perm = GTP__ADD;
+ break;
+ case GTP_CMD_DELPDP:
+ perm = GTP__DEL;
+ break;
+ case GTP_CMD_GETPDP:
+ perm = GTP__GET;
+ break;
+ default:
+ WARN_ON(1);
+ return -EPERM;
+ }
+
+ return avc_has_perm(&selinux_state, sid, gtpsec->sid,
+ SECCLASS_GTP, perm, NULL);
+}
+
#ifdef CONFIG_NETFILTER
static unsigned int selinux_ip_forward(struct sk_buff *skb,
@@ -7130,6 +7193,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(tun_dev_attach_queue, selinux_tun_dev_attach_queue),
LSM_HOOK_INIT(tun_dev_attach, selinux_tun_dev_attach),
LSM_HOOK_INIT(tun_dev_open, selinux_tun_dev_open),
+ LSM_HOOK_INIT(gtp_dev_free_security, selinux_gtp_dev_free_security),
+ LSM_HOOK_INIT(gtp_dev_cmd, selinux_gtp_dev_cmd),
#ifdef CONFIG_SECURITY_INFINIBAND
LSM_HOOK_INIT(ib_pkey_access, selinux_ib_pkey_access),
LSM_HOOK_INIT(ib_endport_manage_subnet,
@@ -7204,6 +7269,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(inode_getsecctx, selinux_inode_getsecctx),
LSM_HOOK_INIT(sk_alloc_security, selinux_sk_alloc_security),
LSM_HOOK_INIT(tun_dev_alloc_security, selinux_tun_dev_alloc_security),
+ LSM_HOOK_INIT(gtp_dev_alloc_security, selinux_gtp_dev_alloc_security),
#ifdef CONFIG_SECURITY_INFINIBAND
LSM_HOOK_INIT(ib_alloc_security, selinux_ib_alloc_security),
#endif
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 40cebde62..3865a4549 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -249,6 +249,8 @@ struct security_class_mapping secclass_map[] = {
{"open", "cpu", "kernel", "tracepoint", "read", "write"} },
{ "lockdown",
{ "integrity", "confidentiality", NULL } },
+ { "gtp",
+ { "add", "del", "get", NULL } },
{ NULL }
};
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index 330b7b6d4..311ffb6ea 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -148,6 +148,10 @@ struct perf_event_security_struct {
u32 sid; /* SID of perf_event obj creator */
};
+struct gtp_security_struct {
+ u32 sid; /* SID of gtp obj creator */
+};
+
extern struct lsm_blob_sizes selinux_blob_sizes;
static inline struct task_security_struct *selinux_cred(const struct cred *cred)
{
--
2.26.2
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