[PATCH v4 03/34] xsm/xen_version: Add XSM for the xen_version hypercall

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

All of XENVER_* have now an XSM check for their sub-ops.

The subop for XENVER_commandline is now a priviliged operation.
To not break guests we still return an string - but it is
just '<denied>\0'.

The rest: XENVER_[version|extraversion|capabilities|
parameters|get_features|page_size|guest_handle|changeset|
compile_info] behave as before - allowed by default for all
guests if using the XSM default policy or with the dummy one.

The admin can choose to change the sub-ops to be denied
as they see fit.

Also we add a local variable block.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

---
Cc: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>

v2: Do XSM check for all the XENVER_ ops.
v3: Add empty data conditions.
v4: Return <denied> for priv subops.
v5: Move extraversion from priv to normal. Drop the XSM check
    for the non-priv subops.
v6: Add +1 for strlen(xen_deny()) to include NULL. Move changeset,
    compile_info to non-priv subops.
v7: Remove the \0 on xen_deny()
v8: Add new XSM domain for xenver hypercall. Add all subops to it.
v9: Remove the extra line, Add Ack from Daniel
v10: Rename the XSM from xen_version_op to xsm_xen_version.
    Prefix the types with 'xen' to distinguish it from another
    hypercall performing similar operation. Removed Ack from Daniel
    as it was so large. Add local variable block.
---
 tools/flask/policy/policy/modules/xen/xen.te | 15 ++++++++
 xen/common/kernel.c                          | 53 +++++++++++++++++++++-------
 xen/common/version.c                         | 15 ++++++++
 xen/include/xen/version.h                    |  2 +-
 xen/include/xsm/dummy.h                      | 22 ++++++++++++
 xen/include/xsm/xsm.h                        |  5 +++
 xen/xsm/dummy.c                              |  1 +
 xen/xsm/flask/hooks.c                        | 43 ++++++++++++++++++++++
 xen/xsm/flask/policy/access_vectors          | 28 +++++++++++++++
 xen/xsm/flask/policy/security_classes        |  1 +
 10 files changed, 172 insertions(+), 13 deletions(-)

diff --git a/tools/flask/policy/policy/modules/xen/xen.te b/tools/flask/policy/policy/modules/xen/xen.te
index d35ae22..7e7400d 100644
--- a/tools/flask/policy/policy/modules/xen/xen.te
+++ b/tools/flask/policy/policy/modules/xen/xen.te
@@ -73,6 +73,15 @@ allow dom0_t xen_t:xen2 {
     pmu_ctrl
     get_symbol
 };
+
+# Allow dom0 to use all XENVER_ subops
+# Note that dom0 is part of domain_type so this has duplicates.
+allow dom0_t xen_t:version {
+    xen_version xen_extraversion xen_compile_info xen_capabilities
+    xen_changeset xen_platform_parameters xen_get_features xen_pagesize
+    xen_guest_handle xen_commandline
+};
+
 allow dom0_t xen_t:mmu memorymap;
 
 # Allow dom0 to use these domctls on itself. For domctls acting on other
@@ -137,6 +146,12 @@ if (guest_writeconsole) {
 # pmu_ctrl is for)
 allow domain_type xen_t:xen2 pmu_use;
 
+# For normal guests all except XENVER_commandline
+allow domain_type xen_t:version {
+    xen_version xen_extraversion xen_compile_info xen_capabilities
+    xen_changeset xen_platform_parameters xen_get_features xen_pagesize
+    xen_guest_handle
+};
 ###############################################################################
 #
 # Domain creation
diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index 0618da2..2699ac0 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -13,6 +13,7 @@
 #include <xen/nmi.h>
 #include <xen/guest_access.h>
 #include <xen/hypercall.h>
+#include <xsm/xsm.h>
 #include <asm/current.h>
 #include <public/nmi.h>
 #include <public/version.h>
@@ -223,12 +224,15 @@ void __init do_initcalls(void)
 /*
  * Simple hypercalls.
  */
-
 DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
+    bool_t deny = !!xsm_xen_version(XSM_OTHER, cmd);
+
     switch ( cmd )
     {
     case XENVER_version:
+        if ( deny )
+            return 0;
         return (xen_major_version() << 16) | xen_minor_version();
 
     case XENVER_extraversion:
@@ -236,7 +240,7 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         xen_extraversion_t extraversion;
 
         memset(extraversion, 0, sizeof(extraversion));
-        safe_strcpy(extraversion, xen_extra_version());
+        safe_strcpy(extraversion, deny ? xen_deny() : xen_extra_version());
         if ( copy_to_guest(arg, extraversion, ARRAY_SIZE(extraversion)) )
             return -EFAULT;
         return 0;
@@ -247,10 +251,10 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         xen_compile_info_t info;
 
         memset(&info, 0, sizeof(info));
-        safe_strcpy(info.compiler,       xen_compiler());
-        safe_strcpy(info.compile_by,     xen_compile_by());
-        safe_strcpy(info.compile_domain, xen_compile_domain());
-        safe_strcpy(info.compile_date,   xen_compile_date());
+        safe_strcpy(info.compiler,       deny ? xen_deny() : xen_compiler());
+        safe_strcpy(info.compile_by,     deny ? xen_deny() : xen_compile_by());
+        safe_strcpy(info.compile_domain, deny ? xen_deny() : xen_compile_domain());
+        safe_strcpy(info.compile_date,   deny ? xen_deny() : xen_compile_date());
         if ( copy_to_guest(arg, &info, 1) )
             return -EFAULT;
         return 0;
@@ -261,7 +265,8 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         xen_capabilities_info_t info;
 
         memset(info, 0, sizeof(info));
-        arch_get_xen_caps(&info);
+        if ( !deny )
+            arch_get_xen_caps(&info);
 
         if ( copy_to_guest(arg, info, ARRAY_SIZE(info)) )
             return -EFAULT;
@@ -274,6 +279,9 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
             .virt_start = HYPERVISOR_VIRT_START
         };
 
+        if ( deny )
+            params.virt_start = 0;
+
         if ( copy_to_guest(arg, &params, 1) )
             return -EFAULT;
         return 0;
@@ -285,7 +293,7 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         xen_changeset_info_t chgset;
 
         memset(chgset, 0, sizeof(chgset));
-        safe_strcpy(chgset, xen_changeset());
+        safe_strcpy(chgset, deny ? xen_deny() : xen_changeset());
         if ( copy_to_guest(arg, chgset, ARRAY_SIZE(chgset)) )
             return -EFAULT;
         return 0;
@@ -302,6 +310,8 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         switch ( fi.submap_idx )
         {
         case 0:
+            if ( deny )
+                break;
             fi.submap = (1U << XENFEAT_memory_op_vnode_supported);
             if ( VM_ASSIST(d, pae_extended_cr3) )
                 fi.submap |= (1U << XENFEAT_pae_pgdir_above_4gb);
@@ -342,19 +352,38 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
     }
 
     case XENVER_pagesize:
+        if ( deny )
+            return 0;
         return (!guest_handle_is_null(arg) ? -EINVAL : PAGE_SIZE);
 
     case XENVER_guest_handle:
-        if ( copy_to_guest(arg, current->domain->handle,
-                           ARRAY_SIZE(current->domain->handle)) )
+    {
+        xen_domain_handle_t hdl;
+        ssize_t len;
+
+        if ( deny )
+        {
+            len = sizeof(hdl);
+            memset(&hdl, 0, len);
+        } else
+            len = ARRAY_SIZE(current->domain->handle);
+
+        if ( copy_to_guest(arg, deny ? hdl : current->domain->handle, len ) )
             return -EFAULT;
         return 0;
-
+    }
     case XENVER_commandline:
-        if ( copy_to_guest(arg, saved_cmdline, ARRAY_SIZE(saved_cmdline)) )
+    {
+        size_t len = ARRAY_SIZE(saved_cmdline);
+
+        if ( deny )
+            len = strlen(xen_deny()) + 1;
+
+        if ( copy_to_guest(arg, deny ? xen_deny() : saved_cmdline, len) )
             return -EFAULT;
         return 0;
     }
+    }
 
     return -ENOSYS;
 }
diff --git a/xen/common/version.c b/xen/common/version.c
index b152e27..fc9bf42 100644
--- a/xen/common/version.c
+++ b/xen/common/version.c
@@ -55,3 +55,18 @@ const char *xen_banner(void)
 {
     return XEN_BANNER;
 }
+
+const char *xen_deny(void)
+{
+    return "<denied>";
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/xen/version.h b/xen/include/xen/version.h
index 81a3c7d..016a56c 100644
--- a/xen/include/xen/version.h
+++ b/xen/include/xen/version.h
@@ -12,5 +12,5 @@ unsigned int xen_minor_version(void);
 const char *xen_extra_version(void);
 const char *xen_changeset(void);
 const char *xen_banner(void);
-
+const char *xen_deny(void);
 #endif /* __XEN_VERSION_H__ */
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 1d13826..94b8855 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -727,3 +727,25 @@ static XSM_INLINE int xsm_pmu_op (XSM_DEFAULT_ARG struct domain *d, unsigned int
 }
 
 #endif /* CONFIG_X86 */
+
+#include <public/version.h>
+static XSM_INLINE int xsm_xen_version (XSM_DEFAULT_ARG uint32_t op)
+{
+    XSM_ASSERT_ACTION(XSM_OTHER);
+    switch ( op )
+    {
+    case XENVER_version:
+    case XENVER_extraversion:
+    case XENVER_compile_info:
+    case XENVER_capabilities:
+    case XENVER_changeset:
+    case XENVER_platform_parameters:
+    case XENVER_get_features:
+    case XENVER_pagesize:
+    case XENVER_guest_handle:
+        /* These MUST always be accessible to any guest by default. */
+        return xsm_default_action(XSM_HOOK, current->domain, NULL);
+    default:
+        return xsm_default_action(XSM_PRIV, current->domain, NULL);
+    }
+}
diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
index 3afed70..db440f6 100644
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -193,6 +193,7 @@ struct xsm_operations {
     int (*ioport_mapping) (struct domain *d, uint32_t s, uint32_t e, uint8_t allow);
     int (*pmu_op) (struct domain *d, unsigned int op);
 #endif
+    int (*xen_version) (uint32_t cmd);
 };
 
 #ifdef CONFIG_XSM
@@ -731,6 +732,10 @@ static inline int xsm_pmu_op (xsm_default_t def, struct domain *d, unsigned int
 
 #endif /* CONFIG_X86 */
 
+static inline int xsm_xen_version (xsm_default_t def, uint32_t op)
+{
+    return xsm_ops->xen_version(op);
+}
 #endif /* XSM_NO_WRAPPERS */
 
 #ifdef CONFIG_MULTIBOOT
diff --git a/xen/xsm/dummy.c b/xen/xsm/dummy.c
index 0f32636..9791ad4 100644
--- a/xen/xsm/dummy.c
+++ b/xen/xsm/dummy.c
@@ -162,4 +162,5 @@ void xsm_fixup_ops (struct xsm_operations *ops)
     set_to_dummy_if_null(ops, ioport_mapping);
     set_to_dummy_if_null(ops, pmu_op);
 #endif
+    set_to_dummy_if_null(ops, xen_version);
 }
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 4813623..d1bef43 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -26,6 +26,7 @@
 #include <public/xen.h>
 #include <public/physdev.h>
 #include <public/platform.h>
+#include <public/version.h>
 
 #include <public/xsm/flask_op.h>
 
@@ -1620,6 +1621,47 @@ static int flask_pmu_op (struct domain *d, unsigned int op)
 }
 #endif /* CONFIG_X86 */
 
+static int flask_xen_version (uint32_t op)
+{
+    u32 dsid = domain_sid(current->domain);
+
+    switch ( op )
+    {
+    case XENVER_version:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_VERSION, NULL);
+    case XENVER_extraversion:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_EXTRAVERSION, NULL);
+    case XENVER_compile_info:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_COMPILE_INFO, NULL);
+    case XENVER_capabilities:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_CAPABILITIES, NULL);
+    case XENVER_changeset:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_CHANGESET, NULL);
+    case XENVER_platform_parameters:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_PLATFORM_PARAMETERS, NULL);
+    case XENVER_get_features:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_GET_FEATURES, NULL);
+    case XENVER_pagesize:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_PAGESIZE, NULL);
+    case XENVER_guest_handle:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_GUEST_HANDLE, NULL);
+    case XENVER_commandline:
+        return avc_has_perm(dsid, SECINITSID_XEN, SECCLASS_VERSION,
+                            VERSION__XEN_COMMANDLINE, NULL);
+    default:
+        return -EPERM;
+    }
+}
+
 long do_flask_op(XEN_GUEST_HANDLE_PARAM(xsm_op_t) u_flask_op);
 int compat_flask_op(XEN_GUEST_HANDLE_PARAM(xsm_op_t) u_flask_op);
 
@@ -1758,6 +1800,7 @@ static struct xsm_operations flask_ops = {
     .ioport_mapping = flask_ioport_mapping,
     .pmu_op = flask_pmu_op,
 #endif
+    .xen_version = flask_xen_version,
 };
 
 static __init void flask_init(void)
diff --git a/xen/xsm/flask/policy/access_vectors b/xen/xsm/flask/policy/access_vectors
index effb59f..628dd5c 100644
--- a/xen/xsm/flask/policy/access_vectors
+++ b/xen/xsm/flask/policy/access_vectors
@@ -495,3 +495,31 @@ class security
 # remove ocontext label definitions for resources
     del_ocontext
 }
+
+# Class version is used to describe the XENVER_ hypercall.
+# Each sub-ops is described here - in the default case all of them should
+# be allowed except the XENVER_commandline.
+#
+class version
+{
+# Often called by PV kernels to force an callback.
+    xen_version
+# Extra informations (-unstable).
+    xen_extraversion
+# Compile information of the hypervisor.
+    xen_compile_info
+# Such as "xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64".
+    xen_capabilities
+# Such as the virtual address of where the hypervisor resides.
+    xen_platform_parameters
+# Source code changeset.
+    xen_changeset
+# The features the hypervisor supports.
+    xen_get_features
+# Page size the hypervisor uses.
+    xen_pagesize
+# An value that the control stack can choose.
+    xen_guest_handle
+# Xen command line.
+    xen_commandline
+}
diff --git a/xen/xsm/flask/policy/security_classes b/xen/xsm/flask/policy/security_classes
index ca191db..cde4e1a 100644
--- a/xen/xsm/flask/policy/security_classes
+++ b/xen/xsm/flask/policy/security_classes
@@ -18,5 +18,6 @@ class shadow
 class event
 class grant
 class security
+class version
 
 # FLASK
-- 
2.5.0


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