secret: rework handling of private secrets

A secret can be marked with the "private" attribute. The intent was that
it is not possible for any libvirt client to be able to read the secret
value, it would only be accesible from within libvirtd. eg the QEMU
driver can read the value to launch a guest.

With the modular daemons, the QEMU, storage and secret drivers are all
running in separate daemons. The QEMU and storage drivers thus appear to
be normal libvirt client's from the POV of the secret driver, and thus
they are not able to read a private secret. This is unhelpful.

With the previous patches that introduced a "system token" to the
identity object, we can now distinguish APIs invoked by libvirt daemons
from those invoked by client applications.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/driver-secret.h

@@ -24,12 +24,6 @@
 # error "Don't include this file directly, only use driver.h"
 #endif
 
-enum {
-    /* This getValue call is inside libvirt, override the "private" flag.
-       This flag cannot be set by outside callers. */
-    VIR_SECRET_GET_VALUE_INTERNAL_CALL = 1 << 0,
-};
-
 typedef virSecretPtr
 (*virDrvSecretLookupByUUID)(virConnectPtr conn,
                             const unsigned char *uuid);
@@ -57,8 +51,7 @@ typedef int
 typedef unsigned char *
 (*virDrvSecretGetValue)(virSecretPtr secret,
                         size_t *value_size,
-                        unsigned int flags,
+                        unsigned int flags);
-                        unsigned int internalFlags);
 
 typedef int
 (*virDrvSecretUndefine)(virSecretPtr secret);

src/libvirt-secret.c

@@ -585,7 +585,7 @@ virSecretGetValue(virSecretPtr secret, size_t *value_size, unsigned int flags)
     if (conn->secretDriver != NULL && conn->secretDriver->secretGetValue != NULL) {
         unsigned char *ret;
 
-        ret = conn->secretDriver->secretGetValue(secret, value_size, flags, 0);
+        ret = conn->secretDriver->secretGetValue(secret, value_size, flags);
         if (ret == NULL)
             goto error;
         return ret;

src/remote/remote_driver.c

@@ -5382,7 +5382,7 @@ remoteDomainBuildQemuMonitorEvent(virNetClientProgram *prog G_GNUC_UNUSED,
 
 static unsigned char *
 remoteSecretGetValue(virSecretPtr secret, size_t *value_size,
-                     unsigned int flags, unsigned int internalFlags)
+                     unsigned int flags)
 {
     unsigned char *rv = NULL;
     remote_secret_get_value_args args;
@@ -5391,12 +5391,6 @@ remoteSecretGetValue(virSecretPtr secret, size_t *value_size,
 
     remoteDriverLock(priv);
 
-    /* internalFlags intentionally do not go over the wire */
-    if (internalFlags) {
-        virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("no internalFlags support"));
-        goto done;
-    }
-
     make_nonnull_secret(&args.secret, secret);
     args.flags = flags;
 

src/secret/secret_driver.c

@@ -36,6 +36,7 @@
 #include "viruuid.h"
 #include "virerror.h"
 #include "virfile.h"
+#include "viridentity.h"
 #include "virpidfile.h"
 #include "configmake.h"
 #include "virstring.h"
@@ -352,8 +353,7 @@ secretSetValue(virSecretPtr secret,
 static unsigned char *
 secretGetValue(virSecretPtr secret,
                size_t *value_size,
-               unsigned int flags,
+               unsigned int flags)
-               unsigned int internalFlags)
 {
     unsigned char *ret = NULL;
     virSecretObj *obj;
@@ -368,11 +368,31 @@ secretGetValue(virSecretPtr secret,
     if (virSecretGetValueEnsureACL(secret->conn, def) < 0)
         goto cleanup;
 
-    if ((internalFlags & VIR_SECRET_GET_VALUE_INTERNAL_CALL) == 0 &&
+    /*
-        def->isprivate) {
+     * For historical compat we want to deny access to
-        virReportError(VIR_ERR_INVALID_SECRET, "%s",
+     * private secrets, even if no ACL driver is
-                       _("secret is private"));
+     * present.
-        goto cleanup;
+     *
+     * We need to validate the identity requesting
+     * the secret value is running as the same user
+     * credentials as this driver.
+     *
+     * ie a non-root libvirt client should not be
+     * able to request the value from privileged
+     * libvirt driver.
+     *
+     * To apply restrictions to processes running under
+     * the same user account is out of scope.
+     */
+    if (def->isprivate) {
+        int rv = virIdentityIsCurrentElevated();
+        if (rv < 0)
+            goto cleanup;
+        if (rv == 0) {
+            virReportError(VIR_ERR_INVALID_SECRET, "%s",
+                           _("secret is private"));
+            goto cleanup;
+        }
     }
 
     if (!(ret = virSecretObjGetValue(obj)))

src/util/virsecret.c

@@ -174,8 +174,7 @@ virSecretGetSecretString(virConnectPtr conn,
         goto cleanup;
     }
 
-    *secret = conn->secretDriver->secretGetValue(sec, secret_size, 0,
+    *secret = conn->secretDriver->secretGetValue(sec, secret_size, 0);
-                                                 VIR_SECRET_GET_VALUE_INTERNAL_CALL);
 
     if (!*secret)
         goto cleanup;

tests/qemuxml2argvtest.c

@@ -43,8 +43,7 @@ static virQEMUDriver driver;
 static unsigned char *
 fakeSecretGetValue(virSecretPtr obj G_GNUC_UNUSED,
                    size_t *value_size,
-                   unsigned int fakeflags G_GNUC_UNUSED,
+                   unsigned int fakeflags G_GNUC_UNUSED)
-                   unsigned int internalFlags G_GNUC_UNUSED)
 {
     char *secret;
     secret = g_strdup("AQCVn5hO6HzFAhAAq0NCv8jtJcIcE+HOBlMQ1A");