xen/xsm: Add new SILO mode for XSM

When SILO is enabled, there would be no page-sharing or event notifications
between unprivileged VMs (no grant tables or event channels).

Signed-off-by: Xin Li <xin.li@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index d03830f837c9bd34f69d0f6f1292313b98cc2be3..a3194cadc3bcc5ba75eb2c47a560b350a68c3928 100644 (file)
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -791,7 +791,7 @@ Note that specifying zero as domU value means zero, while for dom0 it means
 to use the default.
 
 ### xsm
-> `= dummy | flask`
+> `= dummy | flask | silo`
 
 > Default: `dummy`
 
@@ -802,6 +802,9 @@ the hypervisor was compiled with XSM support.
   (the dummy module) will be applied.  It's also used when XSM is compiled out.
 * `flask`: this is the policy based access control.  To choose this, the
   separated option in kconfig must also be enabled.
+* `silo`: this will deny any unmediated communication channels between
+  unprivileged VMs.  To choose this, the separated option in kconfig must also
+  be enabled.
 
 ### flask
 > `= permissive | enforcing | late | disabled`

diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index c87422282f49d91899a2a552c1c8fb6bd37fcfa5..c129cfbdc24e193d4475b09ed032ed7ca2ab0780 100644 (file)
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -137,15 +137,30 @@ config XSM_POLICY
 
          If unsure, say Y.
 
+config XSM_SILO
+       def_bool y
+       prompt "SILO support"
+       depends on XSM
+       ---help---
+         Enables SILO as the access control mechanism used by the XSM framework.
+         This is not the default module, add boot parameter xsm=silo to choose
+         it. This will deny any unmediated communication channels (grant tables
+         and event channels) between unprivileged VMs.
+
+         If unsure, say Y.
+
 choice
        prompt "Default XSM implementation"
        depends on XSM
        default XSM_FLASK_DEFAULT if XSM_FLASK
+       default XSM_SILO_DEFAULT if XSM_SILO
        default XSM_DUMMY_DEFAULT
        config XSM_DUMMY_DEFAULT
                bool "Match non-XSM behavior"
        config XSM_FLASK_DEFAULT
                bool "FLux Advanced Security Kernel" if XSM_FLASK
+       config XSM_SILO_DEFAULT
+               bool "SILO" if XSM_SILO
 endchoice
 
 config LATE_HWDOM

diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index b565a02d444f10a39e91721f6d61611d95e16f91..a25ce30a8a76a5a063d26d41008affe89fe94858 100644 (file)
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -34,7 +34,8 @@ void __xsm_action_mismatch_detected(void);
  * There is no xsm_default_t argument available, so the value from the assertion
  * is used to initialize the variable.
  */
-#define XSM_INLINE /* */
+#define XSM_INLINE __maybe_unused
+
 #define XSM_DEFAULT_ARG /* */
 #define XSM_DEFAULT_VOID void
 #define XSM_ASSERT_ACTION(def) xsm_default_t action = def; (void)action

diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
index 60c0fd6a62e0257ef79885230b6e7895ae88c45c..ef6ff3a78653f82028a8fff12f4546979d22156c 100644 (file)
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -742,6 +742,12 @@ extern const unsigned char xsm_init_policy[];
 extern const unsigned int xsm_init_policy_size;
 #endif
 
+#ifdef CONFIG_XSM_SILO
+extern void silo_init(void);
+#else
+static inline void silo_init(void) {}
+#endif
+
 #else /* CONFIG_XSM */
 
 #include <xsm/dummy.h>

diff --git a/xen/xsm/Makefile b/xen/xsm/Makefile
index 3252c46e64f5dd8c65cf5a132f45c47c7895d617..50e21303b3363af4fbc27f2f058ccc3b7daa466e 100644 (file)
--- a/xen/xsm/Makefile
+++ b/xen/xsm/Makefile
@@ -1,5 +1,6 @@
 obj-y += xsm_core.o
 obj-$(CONFIG_XSM) += xsm_policy.o
 obj-$(CONFIG_XSM) += dummy.o
+obj-$(CONFIG_XSM_SILO) += silo.o
 
 subdir-$(CONFIG_FLASK) += flask

diff --git a/xen/xsm/silo.c b/xen/xsm/silo.c
new file mode 100644 (file)
index 0000000..4850756
--- /dev/null
+++ b/xen/xsm/silo.c
@@ -0,0 +1,108 @@
+/******************************************************************************
+ * xsm/silo.c
+ *
+ * SILO module for XSM (Xen Security Modules)
+ *
+ * Copyright (c) 2018 Citrix Systems Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+#define XSM_NO_WRAPPERS
+#include <xsm/dummy.h>
+
+/*
+ * Check if inter-domain communication is allowed.
+ * Return true when pass check.
+ */
+static bool silo_mode_dom_check(const struct domain *ldom,
+                                const struct domain *rdom)
+{
+    const struct domain *currd = current->domain;
+
+    return (is_control_domain(currd) || is_control_domain(ldom) ||
+            is_control_domain(rdom) || ldom == rdom);
+}
+
+static int silo_evtchn_unbound(struct domain *d1, struct evtchn *chn,
+                               domid_t id2)
+{
+    int rc = -EPERM;
+    struct domain *d2 = rcu_lock_domain_by_any_id(id2);
+
+    if ( d2 == NULL )
+        rc = -ESRCH;
+    else
+    {
+        if ( silo_mode_dom_check(d1, d2) )
+            rc = xsm_evtchn_unbound(d1, chn, id2);
+        rcu_unlock_domain(d2);
+    }
+
+    return rc;
+}
+
+static int silo_evtchn_interdomain(struct domain *d1, struct evtchn *chan1,
+                                   struct domain *d2, struct evtchn *chan2)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_evtchn_interdomain(d1, chan1, d2, chan2);
+    return -EPERM;
+}
+
+static int silo_grant_mapref(struct domain *d1, struct domain *d2,
+                             uint32_t flags)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_grant_mapref(d1, d2, flags);
+    return -EPERM;
+}
+
+static int silo_grant_transfer(struct domain *d1, struct domain *d2)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_grant_transfer(d1, d2);
+    return -EPERM;
+}
+
+static int silo_grant_copy(struct domain *d1, struct domain *d2)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_grant_copy(d1, d2);
+    return -EPERM;
+}
+
+static struct xsm_operations silo_xsm_ops = {
+    .evtchn_unbound = silo_evtchn_unbound,
+    .evtchn_interdomain = silo_evtchn_interdomain,
+    .grant_mapref = silo_grant_mapref,
+    .grant_transfer = silo_grant_transfer,
+    .grant_copy = silo_grant_copy,
+};
+
+void __init silo_init(void)
+{
+    printk("Initialising XSM SILO mode\n");
+
+    if ( register_xsm(&silo_xsm_ops) )
+        panic("SILO: Unable to register with XSM\n");
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

diff --git a/xen/xsm/xsm_core.c b/xen/xsm/xsm_core.c
index e78f7d8ca2d56ce5086743e893bae930b5198ea9..91ef8a70b77bf057b8ffa40d78222573ceec3418 100644 (file)
--- a/xen/xsm/xsm_core.c
+++ b/xen/xsm/xsm_core.c
@@ -30,11 +30,14 @@ struct xsm_operations *xsm_ops;
 enum xsm_bootparam {
     XSM_BOOTPARAM_DUMMY,
     XSM_BOOTPARAM_FLASK,
+    XSM_BOOTPARAM_SILO,
 };
 
 static enum xsm_bootparam __initdata xsm_bootparam =
 #ifdef CONFIG_XSM_FLASK_DEFAULT
     XSM_BOOTPARAM_FLASK;
+#elif CONFIG_XSM_SILO_DEFAULT
+    XSM_BOOTPARAM_SILO;
 #else
     XSM_BOOTPARAM_DUMMY;
 #endif
@@ -48,6 +51,10 @@ static int __init parse_xsm_param(const char *s)
 #ifdef CONFIG_XSM_FLASK
     else if ( !strcmp(s, "flask") )
         xsm_bootparam = XSM_BOOTPARAM_FLASK;
+#endif
+#ifdef CONFIG_XSM_SILO
+    else if ( !strcmp(s, "silo") )
+        xsm_bootparam = XSM_BOOTPARAM_SILO;
 #endif
     else
         rc = -EINVAL;
@@ -92,6 +99,10 @@ static int __init xsm_core_init(const void *policy_buffer, size_t policy_size)
         flask_init(policy_buffer, policy_size);
         break;
 
+    case XSM_BOOTPARAM_SILO:
+        silo_init();
+        break;
+
     default:
         ASSERT_UNREACHABLE();
         break;