[PATCH 2/3] security: Introduce virSecurityManagerDomainSetIncomingPathLabel

[Michal Privoznik]

This API allows drivers to separate out handling of @stdin_path
of virSecurityManagerSetAllLabel(). The thing is, the QEMU driver
uses transactions for virSecurityManagerSetAllLabel() which
relabels devices from inside of domain's namespace. This is what
we usually want. Except when resuming domain from a file. The
file is opened before any namespace is set up and the FD is
passed to QEMU to read the migration stream from. Because of
this, the file lives outside of the namespace and if it so
happens that the file is a block device (i.e. it lives under
/dev) its copy will be created in the namespace. But the FD that
is passed to QEMU points to the original living in the host and
not in the namespace. So relabeling the file inside the namespace
helps nothing.

But if we have a separate API for relabeling the restore file
then the QEMU driver can continue calling
virSecurityManagerSetAllLabel() with transactions enabled and
call this new API without transactions.

We already have an API for relabeling a single file
(virSecurityManagerDomainSetPathLabel()) but in case of SELinux
it uses @imagelabel (which allows RW access) and we want to use
@content_context (which allows RO access).

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/libvirt_private.syms        |  1 +
 src/security/security_driver.h  |  4 ++++
 src/security/security_manager.c | 29 +++++++++++++++++++++++++++++
 src/security/security_manager.h |  4 ++++
 src/security/security_stack.c   | 21 +++++++++++++++++++++
 5 files changed, 59 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index e276f55bb1..2c63f37fc2 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1523,6 +1523,7 @@ virSecurityDriverLookup;
 # security/security_manager.h
 virSecurityManagerCheckAllLabel;
 virSecurityManagerClearSocketLabel;
+virSecurityManagerDomainSetIncomingPathLabel;
 virSecurityManagerDomainSetPathLabel;
 virSecurityManagerGenLabel;
 virSecurityManagerGetBaseLabel;
diff --git a/src/security/security_driver.h b/src/security/security_driver.h
index 3353955813..6cbe8613c9 100644
--- a/src/security/security_driver.h
+++ b/src/security/security_driver.h
@@ -140,6 +140,9 @@ typedef int (*virSecurityDomainSetPathLabel) (virSecurityManagerPtr mgr,
                                               virDomainDefPtr def,
                                               const char *path,
                                               bool allowSubtree);
+typedef int (*virSecurityDomainSetIncomingPathLabel) (virSecurityManagerPtr mgr,
+                                                      virDomainDefPtr def,
+                                                      const char *path);
 typedef int (*virSecurityDomainSetChardevLabel) (virSecurityManagerPtr mgr,
                                                  virDomainDefPtr def,
                                                  virDomainChrSourceDefPtr dev_source,
@@ -211,6 +214,7 @@ struct _virSecurityDriver {
     virSecurityDriverGetBaseLabel getBaseLabel;
 
     virSecurityDomainSetPathLabel domainSetPathLabel;
+    virSecurityDomainSetIncomingPathLabel domainSetIncomingPathLabel;
 
     virSecurityDomainSetChardevLabel domainSetSecurityChardevLabel;
     virSecurityDomainRestoreChardevLabel domainRestoreSecurityChardevLabel;
diff --git a/src/security/security_manager.c b/src/security/security_manager.c
index fe032746ff..a76b953ee4 100644
--- a/src/security/security_manager.c
+++ b/src/security/security_manager.c
@@ -1077,6 +1077,35 @@ virSecurityManagerDomainSetPathLabel(virSecurityManagerPtr mgr,
 }
 
 
+/**
+ * virSecurityManagerDomainSetIncomingPathLabel:
+ * @mgr: security manager object
+ * @vm: domain definition object
+ * @path: path to label
+ *
+ * This function relabels given @path so that @vm can restore for
+ * it.  This allows the driver backend to use different label than
+ * virSecurityManagerDomainSetPathLabel().
+ *
+ * Returns: 0 on success, -1 on error.
+ */
+int
+virSecurityManagerDomainSetIncomingPathLabel(virSecurityManagerPtr mgr,
+                                             virDomainDefPtr vm,
+                                             const char *path)
+{
+    if (mgr->drv->domainSetIncomingPathLabel) {
+        int ret;
+        virObjectLock(mgr);
+        ret = mgr->drv->domainSetIncomingPathLabel(mgr, vm, path);
+        virObjectUnlock(mgr);
+        return ret;
+    }
+
+    return 0;
+}
+
+
 /**
  * virSecurityManagerSetMemoryLabel:
  * @mgr: security manager object
diff --git a/src/security/security_manager.h b/src/security/security_manager.h
index 7699bcbc6f..465d71558f 100644
--- a/src/security/security_manager.h
+++ b/src/security/security_manager.h
@@ -189,6 +189,10 @@ int virSecurityManagerDomainSetPathLabel(virSecurityManagerPtr mgr,
                                          const char *path,
                                          bool allowSubtree);
 
+int virSecurityManagerDomainSetIncomingPathLabel(virSecurityManagerPtr mgr,
+                                                 virDomainDefPtr vm,
+                                                 const char *path);
+
 int virSecurityManagerSetChardevLabel(virSecurityManagerPtr mgr,
                                       virDomainDefPtr def,
                                       virDomainChrSourceDefPtr dev_source,
diff --git a/src/security/security_stack.c b/src/security/security_stack.c
index 073876daff..7782abaf9d 100644
--- a/src/security/security_stack.c
+++ b/src/security/security_stack.c
@@ -825,6 +825,26 @@ virSecurityStackDomainSetPathLabel(virSecurityManagerPtr mgr,
     return rc;
 }
 
+
+static int
+virSecurityStackDomainSetIncomingPathLabel(virSecurityManagerPtr mgr,
+                                           virDomainDefPtr vm,
+                                           const char *path)
+{
+    virSecurityStackDataPtr priv = virSecurityManagerGetPrivateData(mgr);
+    virSecurityStackItemPtr item = priv->itemsHead;
+    int rc = 0;
+
+    for (; item; item = item->next) {
+        if (virSecurityManagerDomainSetIncomingPathLabel(item->securityManager,
+                                                         vm, path) < 0)
+            rc = -1;
+    }
+
+    return rc;
+}
+
+
 static int
 virSecurityStackDomainSetChardevLabel(virSecurityManagerPtr mgr,
                                       virDomainDefPtr def,
@@ -985,6 +1005,7 @@ virSecurityDriver virSecurityDriverStack = {
     .getBaseLabel                       = virSecurityStackGetBaseLabel,
 
     .domainSetPathLabel                 = virSecurityStackDomainSetPathLabel,
+    .domainSetIncomingPathLabel         = virSecurityStackDomainSetIncomingPathLabel,
 
     .domainSetSecurityChardevLabel      = virSecurityStackDomainSetChardevLabel,
     .domainRestoreSecurityChardevLabel  = virSecurityStackDomainRestoreChardevLabel,
-- 
2.24.1