text: // Copyright 2018 The gVisor Authors.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  #include <sys/ioctl.h>
  #include <termios.h>
  
  #include "gtest/gtest.h"
  #include "absl/base/macros.h"
  #include "test/util/capability_util.h"
  #include "test/util/file_descriptor.h"
  #include "test/util/posix_error.h"
  #include "test/util/pty_util.h"
  
  namespace gvisor {
  namespace testing {
  
  // These tests should be run as root.
  namespace {
  
  TEST(JobControlRootTest, StealTTY) {
    SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
  
    // Make this a session leader, which also drops the controlling terminal.
    // In the gVisor test environment, this test will be run as the session
    // leader already (as the sentry init process).
    if (!IsRunningOnGvisor()) {
      ASSERT_THAT(setsid(), SyscallSucceeds());
    }
  
    FileDescriptor master =
        ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/ptmx", O_RDWR | O_NONBLOCK));
    FileDescriptor slave = ASSERT_NO_ERRNO_AND_VALUE(OpenSlave(master));
  
    // Make slave the controlling terminal.
    ASSERT_THAT(ioctl(slave.get(), TIOCSCTTY, 0), SyscallSucceeds());
  
    // Fork, join a new session, and try to steal the parent's controlling
    // terminal, which should succeed when we have CAP_SYS_ADMIN and pass an arg
    // of 1.
    pid_t child = fork();
    if (!child) {
      TEST_PCHECK(setsid() >= 0);
      // We shouldn't be able to steal the terminal with the wrong arg value.
      TEST_PCHECK(ioctl(slave.get(), TIOCSCTTY, 0));
      // We should be able to steal it here.
      TEST_PCHECK(!ioctl(slave.get(), TIOCSCTTY, 1));
      _exit(0);
    }
  
    int wstatus;
    ASSERT_THAT(waitpid(child, &wstatus, 0), SyscallSucceedsWithValue(child));
    ASSERT_EQ(wstatus, 0);
  }
  
  }  // namespace
  }  // namespace testing
  }  // namespace gvisor
  