sandbox/linux/bpf_dsl/bpf_dsl_unittest.cc

// Copyright 2014 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/bpf_dsl/bpf_dsl.h"

#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/utsname.h>
#include <unistd.h>

#include "base/files/scoped_file.h"
#include "base/macros.h"
#include "build/build_config.h"
#include "sandbox/linux/bpf_dsl/bpf_dsl_impl.h"
#include "sandbox/linux/bpf_dsl/policy.h"
#include "sandbox/linux/seccomp-bpf/bpf_tests.h"
#include "sandbox/linux/seccomp-bpf/errorcode.h"
#include "sandbox/linux/seccomp-bpf/syscall.h"
#include "testing/gtest/include/gtest/gtest.h"

#define CASES SANDBOX_BPF_DSL_CASES

// Helper macro to assert that invoking system call |sys| directly via
// Syscall::Call with arguments |...| returns |res|.
// Errors can be asserted by specifying a value like "-EINVAL".
#define ASSERT_SYSCALL_RESULT(res, sys, ...) \
  BPF_ASSERT_EQ(res, Stubs::sys(__VA_ARGS__))

namespace sandbox {
namespace bpf_dsl {
namespace {

// Type safe stubs for tested system calls.
class Stubs {
 public:
  static int getpgid(pid_t pid) { return Syscall::Call(__NR_getpgid, pid); }
  static int setuid(uid_t uid) { return Syscall::Call(__NR_setuid, uid); }
  static int setgid(gid_t gid) { return Syscall::Call(__NR_setgid, gid); }
  static int setpgid(pid_t pid, pid_t pgid) {
    return Syscall::Call(__NR_setpgid, pid, pgid);
  }

  static int fcntl(int fd, int cmd, unsigned long arg = 0) {
    return Syscall::Call(__NR_fcntl, fd, cmd, arg);
  }

  static int uname(struct utsname* buf) {
    return Syscall::Call(__NR_uname, buf);
  }

  static int setresuid(uid_t ruid, uid_t euid, uid_t suid) {
    return Syscall::Call(__NR_setresuid, ruid, euid, suid);
  }

#if !defined(ARCH_CPU_X86)
  static int socketpair(int domain, int type, int protocol, int sv[2]) {
    return Syscall::Call(__NR_socketpair, domain, type, protocol, sv);
  }
#endif
};

class BasicPolicy : public Policy {
 public:
  BasicPolicy() {}
  ~BasicPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_getpgid) {
      const Arg<pid_t> pid(0);
      return If(pid == 0, Error(EPERM)).Else(Error(EINVAL));
    }
    if (sysno == __NR_setuid) {
      const Arg<uid_t> uid(0);
      return If(uid != 42, Error(ESRCH)).Else(Error(ENOMEM));
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(BasicPolicy);
};

BPF_TEST_C(BPFDSL, Basic, BasicPolicy) {
  ASSERT_SYSCALL_RESULT(-EPERM, getpgid, 0);
  ASSERT_SYSCALL_RESULT(-EINVAL, getpgid, 1);

  ASSERT_SYSCALL_RESULT(-ENOMEM, setuid, 42);
  ASSERT_SYSCALL_RESULT(-ESRCH, setuid, 43);
}

/* On IA-32, socketpair() is implemented via socketcall(). :-( */
#if !defined(ARCH_CPU_X86)
class BooleanLogicPolicy : public Policy {
 public:
  BooleanLogicPolicy() {}
  ~BooleanLogicPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_socketpair) {
      const Arg<int> domain(0), type(1), protocol(2);
      return If(domain == AF_UNIX &&
                    (type == SOCK_STREAM || type == SOCK_DGRAM) &&
                    protocol == 0,
                Error(EPERM)).Else(Error(EINVAL));
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(BooleanLogicPolicy);
};

BPF_TEST_C(BPFDSL, BooleanLogic, BooleanLogicPolicy) {
  int sv[2];

  // Acceptable combinations that should return EPERM.
  ASSERT_SYSCALL_RESULT(-EPERM, socketpair, AF_UNIX, SOCK_STREAM, 0, sv);
  ASSERT_SYSCALL_RESULT(-EPERM, socketpair, AF_UNIX, SOCK_DGRAM, 0, sv);

  // Combinations that are invalid for only one reason; should return EINVAL.
  ASSERT_SYSCALL_RESULT(-EINVAL, socketpair, AF_INET, SOCK_STREAM, 0, sv);
  ASSERT_SYSCALL_RESULT(-EINVAL, socketpair, AF_UNIX, SOCK_SEQPACKET, 0, sv);
  ASSERT_SYSCALL_RESULT(
      -EINVAL, socketpair, AF_UNIX, SOCK_STREAM, IPPROTO_TCP, sv);

  // Completely unacceptable combination; should also return EINVAL.
  ASSERT_SYSCALL_RESULT(
      -EINVAL, socketpair, AF_INET, SOCK_SEQPACKET, IPPROTO_UDP, sv);
}
#endif  // !ARCH_CPU_X86

class MoreBooleanLogicPolicy : public Policy {
 public:
  MoreBooleanLogicPolicy() {}
  ~MoreBooleanLogicPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_setresuid) {
      const Arg<uid_t> ruid(0), euid(1), suid(2);
      return If(ruid == 0 || euid == 0 || suid == 0, Error(EPERM))
          .ElseIf(ruid == 1 && euid == 1 && suid == 1, Error(EAGAIN))
          .Else(Error(EINVAL));
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(MoreBooleanLogicPolicy);
};

BPF_TEST_C(BPFDSL, MoreBooleanLogic, MoreBooleanLogicPolicy) {
  // Expect EPERM if any set to 0.
  ASSERT_SYSCALL_RESULT(-EPERM, setresuid, 0, 5, 5);
  ASSERT_SYSCALL_RESULT(-EPERM, setresuid, 5, 0, 5);
  ASSERT_SYSCALL_RESULT(-EPERM, setresuid, 5, 5, 0);

  // Expect EAGAIN if all set to 1.
  ASSERT_SYSCALL_RESULT(-EAGAIN, setresuid, 1, 1, 1);

  // Expect EINVAL for anything else.
  ASSERT_SYSCALL_RESULT(-EINVAL, setresuid, 5, 1, 1);
  ASSERT_SYSCALL_RESULT(-EINVAL, setresuid, 1, 5, 1);
  ASSERT_SYSCALL_RESULT(-EINVAL, setresuid, 1, 1, 5);
  ASSERT_SYSCALL_RESULT(-EINVAL, setresuid, 3, 4, 5);
}

static const uintptr_t kDeadBeefAddr =
    static_cast<uintptr_t>(0xdeadbeefdeadbeefULL);

class ArgSizePolicy : public Policy {
 public:
  ArgSizePolicy() {}
  ~ArgSizePolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_uname) {
      const Arg<uintptr_t> addr(0);
      return If(addr == kDeadBeefAddr, Error(EPERM)).Else(Allow());
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(ArgSizePolicy);
};

BPF_TEST_C(BPFDSL, ArgSizeTest, ArgSizePolicy) {
  struct utsname buf;
  ASSERT_SYSCALL_RESULT(0, uname, &buf);
  ASSERT_SYSCALL_RESULT(
      -EPERM, uname, reinterpret_cast<struct utsname*>(kDeadBeefAddr));
}

class TrappingPolicy : public Policy {
 public:
  TrappingPolicy() {}
  ~TrappingPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_uname) {
      return Trap(UnameTrap, &count_);
    }
    return Allow();
  }

 private:
  static intptr_t count_;

  static intptr_t UnameTrap(const struct arch_seccomp_data& data, void* aux) {
    BPF_ASSERT_EQ(&count_, aux);
    return ++count_;
  }

  DISALLOW_COPY_AND_ASSIGN(TrappingPolicy);
};

intptr_t TrappingPolicy::count_;

BPF_TEST_C(BPFDSL, TrapTest, TrappingPolicy) {
  ASSERT_SYSCALL_RESULT(1, uname, NULL);
  ASSERT_SYSCALL_RESULT(2, uname, NULL);
  ASSERT_SYSCALL_RESULT(3, uname, NULL);
}

class MaskingPolicy : public Policy {
 public:
  MaskingPolicy() {}
  ~MaskingPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_setuid) {
      const Arg<uid_t> uid(0);
      return If((uid & 0xf) == 0, Error(EINVAL)).Else(Error(EACCES));
    }
    if (sysno == __NR_setgid) {
      const Arg<gid_t> gid(0);
      return If((gid & 0xf0) == 0xf0, Error(EINVAL)).Else(Error(EACCES));
    }
    if (sysno == __NR_setpgid) {
      const Arg<pid_t> pid(0);
      return If((pid & 0xa5) == 0xa0, Error(EINVAL)).Else(Error(EACCES));
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(MaskingPolicy);
};

BPF_TEST_C(BPFDSL, MaskTest, MaskingPolicy) {
  for (uid_t uid = 0; uid < 0x100; ++uid) {
    const int expect_errno = (uid & 0xf) == 0 ? EINVAL : EACCES;
    ASSERT_SYSCALL_RESULT(-expect_errno, setuid, uid);
  }

  for (gid_t gid = 0; gid < 0x100; ++gid) {
    const int expect_errno = (gid & 0xf0) == 0xf0 ? EINVAL : EACCES;
    ASSERT_SYSCALL_RESULT(-expect_errno, setgid, gid);
  }

  for (pid_t pid = 0; pid < 0x100; ++pid) {
    const int expect_errno = (pid & 0xa5) == 0xa0 ? EINVAL : EACCES;
    ASSERT_SYSCALL_RESULT(-expect_errno, setpgid, pid, 0);
  }
}

class ElseIfPolicy : public Policy {
 public:
  ElseIfPolicy() {}
  ~ElseIfPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_setuid) {
      const Arg<uid_t> uid(0);
      return If((uid & 0xfff) == 0, Error(0))
          .ElseIf((uid & 0xff0) == 0, Error(EINVAL))
          .ElseIf((uid & 0xf00) == 0, Error(EEXIST))
          .Else(Error(EACCES));
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(ElseIfPolicy);
};

BPF_TEST_C(BPFDSL, ElseIfTest, ElseIfPolicy) {
  ASSERT_SYSCALL_RESULT(0, setuid, 0);

  ASSERT_SYSCALL_RESULT(-EINVAL, setuid, 0x0001);
  ASSERT_SYSCALL_RESULT(-EINVAL, setuid, 0x0002);

  ASSERT_SYSCALL_RESULT(-EEXIST, setuid, 0x0011);
  ASSERT_SYSCALL_RESULT(-EEXIST, setuid, 0x0022);

  ASSERT_SYSCALL_RESULT(-EACCES, setuid, 0x0111);
  ASSERT_SYSCALL_RESULT(-EACCES, setuid, 0x0222);
}

class SwitchPolicy : public Policy {
 public:
  SwitchPolicy() {}
  ~SwitchPolicy() override {}
  ResultExpr EvaluateSyscall(int sysno) const override {
    if (sysno == __NR_fcntl) {
      const Arg<int> cmd(1);
      const Arg<unsigned long> long_arg(2);
      return Switch(cmd)
          .CASES((F_GETFL, F_GETFD), Error(ENOENT))
          .Case(F_SETFD, If(long_arg == O_CLOEXEC, Allow()).Else(Error(EINVAL)))
          .Case(F_SETFL, Error(EPERM))
          .Default(Error(EACCES));
    }
    return Allow();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(SwitchPolicy);
};

BPF_TEST_C(BPFDSL, SwitchTest, SwitchPolicy) {
  base::ScopedFD sock_fd(socket(AF_UNIX, SOCK_STREAM, 0));
  BPF_ASSERT(sock_fd.is_valid());

  ASSERT_SYSCALL_RESULT(-ENOENT, fcntl, sock_fd.get(), F_GETFD);
  ASSERT_SYSCALL_RESULT(-ENOENT, fcntl, sock_fd.get(), F_GETFL);

  ASSERT_SYSCALL_RESULT(0, fcntl, sock_fd.get(), F_SETFD, O_CLOEXEC);
  ASSERT_SYSCALL_RESULT(-EINVAL, fcntl, sock_fd.get(), F_SETFD, 0);

  ASSERT_SYSCALL_RESULT(-EPERM, fcntl, sock_fd.get(), F_SETFL, O_RDONLY);

  ASSERT_SYSCALL_RESULT(-EACCES, fcntl, sock_fd.get(), F_DUPFD, 0);
}

static intptr_t DummyTrap(const struct arch_seccomp_data& data, void* aux) {
  return 0;
}

TEST(BPFDSL, IsAllowDeny) {
  ResultExpr allow = Allow();
  EXPECT_TRUE(allow->IsAllow());
  EXPECT_FALSE(allow->IsDeny());

  ResultExpr error = Error(ENOENT);
  EXPECT_FALSE(error->IsAllow());
  EXPECT_TRUE(error->IsDeny());

  ResultExpr trace = Trace(42);
  EXPECT_FALSE(trace->IsAllow());
  EXPECT_FALSE(trace->IsDeny());

  ResultExpr trap = Trap(DummyTrap, nullptr);
  EXPECT_FALSE(trap->IsAllow());
  EXPECT_TRUE(trap->IsDeny());

  const Arg<int> arg(0);
  ResultExpr maybe = If(arg == 0, Allow()).Else(Error(EPERM));
  EXPECT_FALSE(maybe->IsAllow());
  EXPECT_FALSE(maybe->IsDeny());
}

TEST(BPFDSL, HasUnsafeTraps) {
  ResultExpr allow = Allow();
  EXPECT_FALSE(allow->HasUnsafeTraps());

  ResultExpr safe = Trap(DummyTrap, nullptr);
  EXPECT_FALSE(safe->HasUnsafeTraps());

  ResultExpr unsafe = UnsafeTrap(DummyTrap, nullptr);
  EXPECT_TRUE(unsafe->HasUnsafeTraps());

  const Arg<int> arg(0);
  ResultExpr maybe = If(arg == 0, allow).Else(unsafe);
  EXPECT_TRUE(maybe->HasUnsafeTraps());
}

}  // namespace
}  // namespace bpf_dsl
}  // namespace sandbox