Add domain-specific language for BPF policies

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 <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/utsname.h>
+
+#include "base/macros.h"
+#include "build/build_config.h"
+#include "sandbox/linux/seccomp-bpf/bpf_tests.h"
+#include "sandbox/linux/seccomp-bpf/errorcode.h"
+#include "sandbox/linux/seccomp-bpf/sandbox_bpf_policy.h"
+#include "sandbox/linux/seccomp-bpf/syscall.h"
+
+using namespace sandbox::bpf_dsl;
+
+// 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 {
+
+// 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 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 SandboxBPFDSLPolicy {
+ public:
+  BasicPolicy() {}
+  virtual ~BasicPolicy() {}
+  virtual 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));
+    }
+    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);
+}
+
+/* On IA-32, socketpair() is implemented via socketcall(). :-( */
+#if !defined(ARCH_CPU_X86)
+class BooleanLogicPolicy : public SandboxBPFDSLPolicy {
+ public:
+  BooleanLogicPolicy() {}
+  virtual ~BooleanLogicPolicy() {}
+  virtual 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 SandboxBPFDSLPolicy {
+ public:
+  MoreBooleanLogicPolicy() {}
+  virtual ~MoreBooleanLogicPolicy() {}
+  virtual 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 SandboxBPFDSLPolicy {
+ public:
+  ArgSizePolicy() {}
+  virtual ~ArgSizePolicy() {}
+  virtual 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 SandboxBPFDSLPolicy {
+ public:
+  TrappingPolicy() {}
+  virtual ~TrappingPolicy() {}
+  virtual 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 SandboxBPFDSLPolicy {
+ public:
+  MaskingPolicy() {}
+  virtual ~MaskingPolicy() {}
+  virtual 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));
+    }
+    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);
+  }
+}
+
+class ElseIfPolicy : public SandboxBPFDSLPolicy {
+ public:
+  ElseIfPolicy() {}
+  virtual ~ElseIfPolicy() {}
+  virtual 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);
+}
+
+}  // namespace
+}  // namespace sandbox