[libvirt] [PATCH v5 18/20] tpm: Check TPM XML device configuration changes after edit

[Stefan Berger]

Since swtpm does not support getting started without password
once it was created with encryption enabled, we don't allow
encryption to be removed. Similarly, we do not allow encryption
to be added once swtpm has run. We also prevent chaning the type
of the TPM backend since the encrypted state is still around and
the next time one was to switch back to the emulator backend
and forgot the encryption the TPM would not work.

Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
---
 src/conf/domain_conf.c    | 56 +++++++++++++++++++++++++++++++++++++++
 src/conf/domain_conf.h    |  4 +++
 src/libvirt_private.syms  |  1 +
 src/qemu/qemu_driver.c    | 28 ++++++++++++++++++++
 src/qemu/qemu_extdevice.c |  2 +-
 src/qemu/qemu_extdevice.h |  3 +++
 6 files changed, 93 insertions(+), 1 deletion(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 7b0de160a6..88445dcde4 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -31426,3 +31426,59 @@ virDomainGraphicsNeedsAutoRenderNode(const virDomainGraphicsDef *graphics)
 
     return true;
 }
+
+
+static int
+virDomainCheckTPMChanges(virDomainDefPtr def,
+                         virDomainDefPtr newDef)
+{
+    bool oldEnc, newEnc;
+
+    if (!def->tpm)
+        return 0;
+
+    switch (def->tpm->type) {
+    case VIR_DOMAIN_TPM_TYPE_EMULATOR:
+        if (virFileExists(def->tpm->data.emulator.storagepath)) {
+            /* VM has been started */
+            /* Once a VM was started with an encrypted state we allow
+             * less configuration changes.
+             */
+            oldEnc = def->tpm->data.emulator.hassecretuuid;
+            if (oldEnc && def->tpm->type != newDef->tpm->type) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("Changing the type of TPM is not allowed"));
+                return -1;
+            }
+            if (oldEnc && !newDef->tpm) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("Removing an encrypted TPM is not allowed"));
+                return -1;
+            }
+            newEnc = newDef->tpm->data.emulator.hassecretuuid;
+            if (oldEnc != newEnc) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                   _("TPM state encryption cannot be changed "
+                     "once VM was started"));
+                return -1;
+            }
+        }
+        break;
+    case VIR_DOMAIN_TPM_TYPE_PASSTHROUGH:
+    case VIR_DOMAIN_TPM_TYPE_LAST:
+        break;
+    }
+
+    return 0;
+}
+
+
+int
+virDomainCheckDeviceChanges(virDomainDefPtr def,
+                            virDomainDefPtr newDef)
+{
+    if (!def || !newDef)
+        return 0;
+
+    return virDomainCheckTPMChanges(def, newDef);
+}
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 3facf506ce..7482401983 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -3624,3 +3624,7 @@ virDomainGraphicsGetRenderNode(const virDomainGraphicsDef *graphics);
 
 bool
 virDomainGraphicsNeedsAutoRenderNode(const virDomainGraphicsDef *graphics);
+
+int
+virDomainCheckDeviceChanges(virDomainDefPtr def, virDomainDefPtr newDef)
+    ATTRIBUTE_NONNULL(2);
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index b531ab1efa..ec3b893a2e 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -205,6 +205,7 @@ virDomainBootTypeFromString;
 virDomainBootTypeToString;
 virDomainCapabilitiesPolicyTypeToString;
 virDomainCapsFeatureTypeToString;
+virDomainCheckDeviceChanges;
 virDomainChrConsoleTargetTypeFromString;
 virDomainChrConsoleTargetTypeToString;
 virDomainChrDefForeach;
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index ef2e980216..8f224582b6 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -52,6 +52,7 @@
 #include "qemu_migration_params.h"
 #include "qemu_blockjob.h"
 #include "qemu_security.h"
+#include "qemu_extdevice.h"
 
 #include "virerror.h"
 #include "virlog.h"
@@ -7568,6 +7569,30 @@ qemuDomainCreate(virDomainPtr dom)
     return qemuDomainCreateWithFlags(dom, 0);
 }
 
+static int
+qemuDomainCheckDeviceChanges(virQEMUDriverPtr driver,
+                             virDomainDefPtr def)
+{
+    virDomainObjPtr vm;
+    int ret;
+
+    vm = virDomainObjListFindByUUID(driver->domains, def->uuid);
+    if (!vm)
+        return 0;
+
+    if (qemuExtDevicesInitPaths(driver, vm->def) < 0) {
+        ret = -1;
+        goto cleanup;
+    }
+
+    ret = virDomainCheckDeviceChanges(vm->def, def);
+
+ cleanup:
+    virDomainObjEndAPI(&vm);
+
+    return ret;
+}
+
 static virDomainPtr
 qemuDomainDefineXMLFlags(virConnectPtr conn,
                          const char *xml,
@@ -7604,6 +7629,9 @@ qemuDomainDefineXMLFlags(virConnectPtr conn,
     if (virDomainDefineXMLFlagsEnsureACL(conn, def) < 0)
         goto cleanup;
 
+    if (qemuDomainCheckDeviceChanges(driver, def) < 0)
+        goto cleanup;
+
     if (!(vm = virDomainObjListAdd(driver->domains, def,
                                    driver->xmlopt,
                                    0, &oldDef)))
diff --git a/src/qemu/qemu_extdevice.c b/src/qemu/qemu_extdevice.c
index a21caefaba..e576bca165 100644
--- a/src/qemu/qemu_extdevice.c
+++ b/src/qemu/qemu_extdevice.c
@@ -79,7 +79,7 @@ qemuExtDeviceLogCommand(qemuDomainLogContextPtr logCtxt,
  * stored and we can remove directories and files in case of domain XML
  * changes.
  */
-static int
+int
 qemuExtDevicesInitPaths(virQEMUDriverPtr driver,
                         virDomainDefPtr def)
 {
diff --git a/src/qemu/qemu_extdevice.h b/src/qemu/qemu_extdevice.h
index a72e05ce63..bbdb9a1cc2 100644
--- a/src/qemu/qemu_extdevice.h
+++ b/src/qemu/qemu_extdevice.h
@@ -53,3 +53,6 @@ bool qemuExtDevicesHasDevice(virDomainDefPtr def);
 int qemuExtDevicesSetupCgroup(virQEMUDriverPtr driver,
                               virDomainDefPtr def,
                               virCgroupPtr cgroup);
+
+int qemuExtDevicesInitPaths(virQEMUDriverPtr driver,
+                            virDomainDefPtr def);
-- 
2.20.1