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// 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>
#include <sys/types.h>
#include <unistd.h>
#include "base/file_util.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "sandbox/linux/tests/unit_tests.h"
#include "testing/gtest/include/gtest/gtest.h"
using file_util::ScopedFD;
namespace sandbox {
namespace {
bool DirectoryExists(const char* path) {
struct stat dir;
errno = 0;
int ret = stat(path, &dir);
return -1 != ret || ENOENT != errno;
}
bool WorkingDirectoryIsRoot() {
char current_dir[PATH_MAX];
char* cwd = getcwd(current_dir, sizeof(current_dir));
PCHECK(cwd);
if (strcmp("/", cwd)) return false;
// The current directory is the root. Add a few paranoid checks.
struct stat current;
CHECK_EQ(0, stat(".", ¤t));
struct stat parrent;
CHECK_EQ(0, stat("..", &parrent));
CHECK_EQ(current.st_dev, parrent.st_dev);
CHECK_EQ(current.st_ino, parrent.st_ino);
CHECK_EQ(current.st_mode, parrent.st_mode);
CHECK_EQ(current.st_uid, parrent.st_uid);
CHECK_EQ(current.st_gid, parrent.st_gid);
return true;
}
// Give dynamic tools a simple thing to test.
TEST(Credentials, CreateAndDestroy) {
{
Credentials cred1;
(void) cred1;
}
scoped_ptr<Credentials> cred2(new Credentials);
}
TEST(Credentials, HasOpenDirectory) {
Credentials creds;
// No open directory should exist at startup.
EXPECT_FALSE(creds.HasOpenDirectory(-1));
{
// Have a "/dev" file descriptor around.
int dev_fd = open("/dev", O_RDONLY | O_DIRECTORY);
ScopedFD dev_fd_closer(&dev_fd);
EXPECT_TRUE(creds.HasOpenDirectory(-1));
}
EXPECT_FALSE(creds.HasOpenDirectory(-1));
}
TEST(Credentials, HasOpenDirectoryWithFD) {
Credentials creds;
int proc_fd = open("/proc", O_RDONLY | O_DIRECTORY);
ScopedFD proc_fd_closer(&proc_fd);
ASSERT_LE(0, proc_fd);
// Don't pass |proc_fd|, an open directory (proc_fd) should
// be detected.
EXPECT_TRUE(creds.HasOpenDirectory(-1));
// Pass |proc_fd| and no open directory should be detected.
EXPECT_FALSE(creds.HasOpenDirectory(proc_fd));
{
// Have a "/dev" file descriptor around.
int dev_fd = open("/dev", O_RDONLY | O_DIRECTORY);
ScopedFD dev_fd_closer(&dev_fd);
EXPECT_TRUE(creds.HasOpenDirectory(proc_fd));
}
// The "/dev" file descriptor should now be closed, |proc_fd| is the only
// directory file descriptor open.
EXPECT_FALSE(creds.HasOpenDirectory(proc_fd));
}
SANDBOX_TEST(Credentials, DropAllCaps) {
Credentials creds;
CHECK(creds.DropAllCapabilities());
CHECK(!creds.HasAnyCapability());
}
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 moved_to_new_ns = creds.MoveToNewUserNS();
fprintf(stdout,
"Unprivileged CLONE_NEWUSER supported: %s\n",
moved_to_new_ns ? "true." : "false.");
fflush(stdout);
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;
PCHECK(0 == getresuid(&new_ruid, &new_euid, &new_suid));
CHECK(old_ruid == new_ruid);
CHECK(old_euid == new_euid);
CHECK(old_suid == new_suid);
gid_t new_rgid, new_egid, new_sgid;
PCHECK(0 == getresgid(&new_rgid, &new_egid, &new_sgid));
CHECK(old_rgid == new_rgid);
CHECK(old_egid == new_egid);
CHECK(old_sgid == new_sgid);
}
bool NewUserNSCycle(Credentials* creds) {
DCHECK(creds);
if (!creds->MoveToNewUserNS() ||
!creds->HasAnyCapability() ||
!creds->DropAllCapabilities() ||
creds->HasAnyCapability()) {
return false;
}
return true;
}
SANDBOX_TEST(Credentials, NestedUserNS) {
Credentials creds;
CHECK(creds.DropAllCapabilities());
// Probably missing kernel support.
if (!creds.MoveToNewUserNS()) return;
creds.DropAllCapabilities();
// As of 3.12, the kernel has a limit of 32. See create_user_ns().
const int kNestLevel = 10;
for (int i = 0; i < kNestLevel; ++i) {
CHECK(NewUserNSCycle(&creds)) << "Creating new user NS failed at iteration "
<< i << ".";
}
}
// Test the WorkingDirectoryIsRoot() helper.
TEST(Credentials, CanDetectRoot) {
ASSERT_EQ(0, chdir("/proc/"));
ASSERT_FALSE(WorkingDirectoryIsRoot());
ASSERT_EQ(0, chdir("/"));
ASSERT_TRUE(WorkingDirectoryIsRoot());
}
SANDBOX_TEST(Credentials, DropFileSystemAccessIsSafe) {
Credentials creds;
CHECK(creds.DropAllCapabilities());
// Probably missing kernel support.
if (!creds.MoveToNewUserNS()) return;
CHECK(creds.DropFileSystemAccess());
CHECK(!DirectoryExists("/proc"));
CHECK(WorkingDirectoryIsRoot());
// We want the chroot to never have a subdirectory. A subdirectory
// could allow a chroot escape.
CHECK_NE(0, mkdir("/test", 0700));
}
// Check that after dropping filesystem access and dropping privileges
// it is not possible to regain capabilities.
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.
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