system_unittest.cc

// system_unittest.cpp
// Copyright (C) 2017 The Android Open Source Project
//
// 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.
//
// Test system.[ch] module code using gtest.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <gtest/gtest.h>

#include "system.h"

namespace {

// A random path that really really should not exist on the host.
const char kNoSuchDir[] = "/.x/..x/...x/path/should/not/exist/";

// A random file that should exist.
const char kValidFile[] = "/etc/passwd";

// A random directory that should exist.
const char kValidDir[] = "/";

// A random character device that should exist.
const char kValidCharDev[] = "/dev/null";

// Return a temp filename in the cwd that this test can manipulate.
// It will not exist when it returns, and the user has to free the memory.
char *get_temp_path() {
  char *path = strdup("minijail.tests.XXXXXX");
  if (!path)
    return nullptr;

  // Just create the temp path.
  int fd = mkstemp(path);
  if (fd < 0)
    return nullptr;
  close(fd);
  unlink(path);

  return path;
}

}  // namespace

// Sanity check for the cap range.
TEST(get_last_valid_cap, basic) {
  unsigned int cap = get_last_valid_cap();

  // We pick 35 as it's been that since at least v3.0.
  // If this test is run on older kernels, it might fail.
  EXPECT_GE(cap, 35u);

  // Pick a really large number that we probably won't hit for a long time.
  // It helps that caps are bitfields.
  EXPECT_LT(cap, 128u);
}

// Might be useful to figure out the return value, but for now,
// just make sure it doesn't crash?
TEST(cap_ambient_supported, smoke) {
  cap_ambient_supported();
}

// Invalid indexes should return errors, not crash.
TEST(setup_pipe_end, bad_index) {
  EXPECT_LT(setup_pipe_end(nullptr, 2), 0);
  EXPECT_LT(setup_pipe_end(nullptr, 3), 0);
  EXPECT_LT(setup_pipe_end(nullptr, 4), 0);
}

// Verify getting the first fd works.
TEST(setup_pipe_end, index0) {
  int fds[2];
  EXPECT_EQ(0, pipe(fds));
  // This should close fds[1] and return fds[0].
  EXPECT_EQ(fds[0], setup_pipe_end(fds, 0));
  // Use close() to verify open/close state.
  EXPECT_EQ(-1, close(fds[1]));
  EXPECT_EQ(0, close(fds[0]));
}

// Verify getting the second fd works.
TEST(setup_pipe_end, index1) {
  int fds[2];
  EXPECT_EQ(0, pipe(fds));
  // This should close fds[0] and return fds[1].
  EXPECT_EQ(fds[1], setup_pipe_end(fds, 1));
  // Use close() to verify open/close state.
  EXPECT_EQ(-1, close(fds[0]));
  EXPECT_EQ(0, close(fds[1]));
}

// Invalid indexes should return errors, not crash.
TEST(setup_and_dupe_pipe_end, bad_index) {
  EXPECT_LT(setup_and_dupe_pipe_end(nullptr, 2, -1), 0);
  EXPECT_LT(setup_and_dupe_pipe_end(nullptr, 3, -1), 0);
  EXPECT_LT(setup_and_dupe_pipe_end(nullptr, 4, -1), 0);
}

// An invalid path should return an error.
TEST(write_pid_to_path, bad_path) {
  EXPECT_NE(0, write_pid_to_path(0, kNoSuchDir));
}

// Make sure we can write a pid to the file.
TEST(write_pid_to_path, basic) {
  char *path = get_temp_path();
  ASSERT_NE(nullptr, path);

  EXPECT_EQ(0, write_pid_to_path(1234, path));
  FILE *fp = fopen(path, "re");
  unlink(path);
  EXPECT_NE(nullptr, fp);
  char data[6] = {};
  EXPECT_EQ(5u, fread(data, 1, sizeof(data), fp));
  fclose(fp);
  EXPECT_EQ(0, strcmp(data, "1234\n"));

  free(path);
}

// If the destination exists, there's nothing to do.
TEST(setup_mount_destination, dest_exists) {
  // Pick some paths that should always exist.  We pass in invalid pointers
  // for other args so we crash if the dest check doesn't short circuit.
  EXPECT_EQ(0, setup_mount_destination(nullptr, kValidDir, 0, 0, false));
  EXPECT_EQ(0, setup_mount_destination(nullptr, "/proc", 0, 0, true));
  EXPECT_EQ(0, setup_mount_destination(nullptr, "/dev", 0, 0, false));
}

// When given a bind mount where the source is relative, reject it.
TEST(setup_mount_destination, reject_relative_bind) {
  // Pick a destination we know doesn't exist.
  EXPECT_NE(0, setup_mount_destination("foo", kNoSuchDir, 0, 0, true));
}

// A mount of a pseudo filesystem should make the destination dir.
TEST(setup_mount_destination, create_pseudo_fs) {
  char *path = get_temp_path();
  ASSERT_NE(nullptr, path);

  // Passing -1 for uid/gid tells chown to make no changes.
  EXPECT_EQ(0, setup_mount_destination("none", path, -1, -1, false));
  // We check it's a directory by deleting it as such.
  EXPECT_EQ(0, rmdir(path));

  free(path);
}

// If the source path does not exist, we should error out.
TEST(setup_mount_destination, missing_source) {
  // The missing dest path is so we can exercise the source logic.
  EXPECT_NE(0, setup_mount_destination(kNoSuchDir, kNoSuchDir, 0, 0, false));
  EXPECT_NE(0, setup_mount_destination(kNoSuchDir, kNoSuchDir, 0, 0, true));
}

// A bind mount of a directory should create the destination dir.
TEST(setup_mount_destination, create_bind_dir) {
  char *path = get_temp_path();
  ASSERT_NE(nullptr, path);

  // Passing -1 for uid/gid tells chown to make no changes.
  EXPECT_EQ(0, setup_mount_destination(kValidDir, path, -1, -1, true));
  // We check it's a directory by deleting it as such.
  EXPECT_EQ(0, rmdir(path));

  free(path);
}

// A bind mount of a file should create the destination file.
TEST(setup_mount_destination, create_bind_file) {
  char *path = get_temp_path();
  ASSERT_NE(nullptr, path);

  // Passing -1 for uid/gid tells chown to make no changes.
  EXPECT_EQ(0, setup_mount_destination(kValidFile, path, -1, -1, true));
  // We check it's a file by deleting it as such.
  EXPECT_EQ(0, unlink(path));

  free(path);
}

// A mount of a character device should create the destination char.
TEST(setup_mount_destination, create_char_dev) {
  char *path = get_temp_path();
  ASSERT_NE(nullptr, path);

  // Passing -1 for uid/gid tells chown to make no changes.
  EXPECT_EQ(0, setup_mount_destination(kValidCharDev, path, -1, -1, false));
  // We check it's a directory by deleting it as such.
  EXPECT_EQ(0, rmdir(path));

  free(path);
}