tests/sys_prctl_test.cpp

/*
 * Copyright (C) 2015 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.
 */

#include <inttypes.h>
#include <limits.h>
#include <stdio.h>
#include <sys/capability.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <unistd.h>

#include <string>
#include <vector>

#include <gtest/gtest.h>

#include "android-base/file.h"
#include "android-base/strings.h"

// http://b/20017123.
TEST(sys_prctl, bug_20017123) {
#if defined(PR_SET_VMA) // PR_SET_VMA is only available in Android kernels.
  size_t page_size = static_cast<size_t>(sysconf(_SC_PAGESIZE));
  void* p = mmap(NULL, page_size * 3, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  ASSERT_NE(MAP_FAILED, p);
  ASSERT_EQ(0, mprotect(p, page_size, PROT_NONE));
  ASSERT_NE(-1, prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, p, page_size * 3, "anonymous map space"));
  // Now read the maps and verify that there are no overlapped maps.
  std::string file_data;
  ASSERT_TRUE(android::base::ReadFileToString("/proc/self/maps", &file_data));

  uintptr_t last_end = 0;
  std::vector<std::string> lines = android::base::Split(file_data, "\n");
  for (size_t i = 0; i < lines.size(); i++) {
    if (lines[i].empty()) {
      continue;
    }
    uintptr_t start;
    uintptr_t end;
    ASSERT_EQ(2, sscanf(lines[i].c_str(), "%" SCNxPTR "-%" SCNxPTR " ", &start, &end))
        << "Failed to parse line: " << lines[i];
    // This will never fail on the first line, so no need to do any special checking.
    ASSERT_GE(start, last_end)
        << "Overlapping map detected:\n" << lines[i -1] << '\n' << lines[i] << '\n';
    last_end = end;
  }

  ASSERT_EQ(0, munmap(p, page_size * 3));
#else
  GTEST_LOG_(INFO) << "This test does nothing as it tests an Android specific kernel feature.";
#endif
}

TEST(sys_prctl, pr_cap_ambient) {
// PR_CAP_AMBIENT was introduced in v4.3.  Android devices should always
// have a backport, but we can't guarantee it's available on the host.
#if defined(__ANDROID__) || defined(PR_CAP_AMBIENT)
  const std::string caps_sha =
      "https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/"
      "?id=58319057b7847667f0c9585b9de0e8932b0fdb08";
  const std::string caps_typo_sha =
      "https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/"
      "?id=b7f76ea2ef6739ee484a165ffbac98deb855d3d3";

  auto err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
  EXPECT_EQ(0, err);
  // EINVAL -> unrecognized prctl option
  ASSERT_NE(EINVAL, errno) << "kernel missing required commits:\n"
                           << caps_sha << "\n"
                           << caps_typo_sha << "\n";

  // Unprivileged processes shouldn't be able to raise CAP_SYS_ADMIN,
  // but they can check or lower it
  err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_SYS_ADMIN, 0, 0);
  EXPECT_EQ(-1, err);
  EXPECT_EQ(EPERM, errno);

  err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_SYS_ADMIN, 0, 0);
  EXPECT_EQ(0, err);

  err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_LOWER, CAP_SYS_ADMIN, 0, 0);
  EXPECT_EQ(0, err);

  // ULONG_MAX isn't a legal cap
  err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, ULONG_MAX, 0, 0);
  EXPECT_EQ(-1, err);
  EXPECT_EQ(EINVAL, errno);

  err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, ULONG_MAX, 0, 0);
  EXPECT_EQ(-1, err);
  EXPECT_EQ(EINVAL, errno);

  err = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_LOWER, ULONG_MAX, 0, 0);
  EXPECT_EQ(-1, err);
  EXPECT_EQ(EINVAL, errno);
#else
  GTEST_LOG_(INFO)
      << "Skipping test that requires host support for PR_CAP_AMBIENT.";
#endif
}