Linux Sandbox: add Credentials::SupportsNewUserNS()

sandbox/linux/services/credentials_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/services/credentials.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <sys/stat.h>
@@ skipping 94 matching lines @@
 SANDBOX_TEST(Credentials, GetCurrentCapString) {
   Credentials creds;
   CHECK(creds.DropAllCapabilities());
   const char kNoCapabilityText[] = "=";
   CHECK(*creds.GetCurrentCapString() == kNoCapabilityText);
 }
 
 SANDBOX_TEST(Credentials, MoveToNewUserNS) {
   Credentials creds;
   creds.DropAllCapabilities();
-  bool userns_supported = creds.MoveToNewUserNS();
-  fprintf(stdout, "Unprivileged CLONE_NEWUSER supported: %s\n",
-          userns_supported ? "true." : "false.");
+  bool moved_to_new_ns = creds.MoveToNewUserNS();
+  fprintf(stdout,
+          "Unprivileged CLONE_NEWUSER supported: %s\n",
+          moved_to_new_ns ? "true." : "false.");
   fflush(stdout);
-  if (!userns_supported) {
+  if (!moved_to_new_ns) {
     fprintf(stdout, "This kernel does not support unprivileged namespaces. "
             "USERNS tests will succeed without running.\n");
     fflush(stdout);
     return;
   }
   CHECK(creds.HasAnyCapability());
   creds.DropAllCapabilities();
   CHECK(!creds.HasAnyCapability());
 }
 
+SANDBOX_TEST(Credentials, SupportsUserNS) {
+  Credentials creds;
+  creds.DropAllCapabilities();
+  bool user_ns_supported = Credentials::SupportsNewUserNS();
+  bool moved_to_new_ns = creds.MoveToNewUserNS();
+  CHECK_EQ(user_ns_supported, moved_to_new_ns);
+}
+
 SANDBOX_TEST(Credentials, UidIsPreserved) {
   Credentials creds;
   creds.DropAllCapabilities();
   uid_t old_ruid, old_euid, old_suid;
   gid_t old_rgid, old_egid, old_sgid;
   PCHECK(0 == getresuid(&old_ruid, &old_euid, &old_suid));
   PCHECK(0 == getresgid(&old_rgid, &old_egid, &old_sgid));
   // Probably missing kernel support.
   if (!creds.MoveToNewUserNS()) return;
   uid_t new_ruid, new_euid, new_suid;
@@ skipping 60 matching lines @@
 SANDBOX_TEST(Credentials, CannotRegainPrivileges) {
   Credentials creds;
   CHECK(creds.DropAllCapabilities());
   // Probably missing kernel support.
   if (!creds.MoveToNewUserNS()) return;
   CHECK(creds.DropFileSystemAccess());
   CHECK(creds.DropAllCapabilities());
 
   // The kernel should now prevent us from regaining capabilities because we
   // are in a chroot.
+  CHECK(!Credentials::SupportsNewUserNS());
   CHECK(!creds.MoveToNewUserNS());
 }
 
 }  // namespace.
 
 }  // namespace sandbox.