sandbox/linux/seccomp-bpf/syscall_unittest.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sandbox/linux/seccomp-bpf/syscall.h"
   6
   7 #include <asm/unistd.h>
   8 #include <fcntl.h>
   9 #include <sys/mman.h>
  10 #include <sys/syscall.h>
  11 #include <sys/types.h>
  12 #include <unistd.h>
  13
  14 #include <vector>
  15
  16 #include "base/posix/eintr_wrapper.h"
  17 #include "build/build_config.h"
  18 #include "sandbox/linux/bpf_dsl/bpf_dsl.h"
  19 #include "sandbox/linux/bpf_dsl/policy.h"
  20 #include "sandbox/linux/seccomp-bpf/bpf_tests.h"
  21 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
  22 #include "sandbox/linux/tests/unit_tests.h"
  23 #include "testing/gtest/include/gtest/gtest.h"
  24
  25 using sandbox::bpf_dsl::Allow;
  26 using sandbox::bpf_dsl::ResultExpr;
  27 using sandbox::bpf_dsl::Trap;
  28
  29 namespace sandbox {
  30
  31 namespace {
  32
  33 // Different platforms use different symbols for the six-argument version
  34 // of the mmap() system call. Test for the correct symbol at compile time.
  35 #ifdef __NR_mmap2
  36 const int kMMapNr = __NR_mmap2;
  37 #else
  38 const int kMMapNr = __NR_mmap;
  39 #endif
  40
  41 TEST(Syscall, InvalidCallReturnsENOSYS) {
  42   EXPECT_EQ(-ENOSYS, Syscall::InvalidCall());
  43 }
  44
  45 TEST(Syscall, WellKnownEntryPoint) {
  46 // Test that Syscall::Call(-1) is handled specially. Don't do this on ARM,
  47 // where syscall(-1) crashes with SIGILL. Not running the test is fine, as we
  48 // are still testing ARM code in the next set of tests.
  49 #if !defined(__arm__) && !defined(__aarch64__)
  50   EXPECT_NE(Syscall::Call(-1), syscall(-1));
  51 #endif
  52
  53 // If possible, test that Syscall::Call(-1) returns the address right
  54 // after
  55 // a kernel entry point.
  56 #if defined(__i386__)
  57   EXPECT_EQ(0x80CDu, ((uint16_t*)Syscall::Call(-1))[-1]);  // INT 0x80
  58 #elif defined(__x86_64__)
  59   EXPECT_EQ(0x050Fu, ((uint16_t*)Syscall::Call(-1))[-1]);  // SYSCALL
  60 #elif defined(__arm__)
  61 #if defined(__thumb__)
  62   EXPECT_EQ(0xDF00u, ((uint16_t*)Syscall::Call(-1))[-1]);  // SWI 0
  63 #else
  64   EXPECT_EQ(0xEF000000u, ((uint32_t*)Syscall::Call(-1))[-1]);  // SVC 0
  65 #endif
  66 #elif defined(__mips__)
  67   // Opcode for MIPS sycall is in the lower 16-bits
  68   EXPECT_EQ(0x0cu, (((uint32_t*)Syscall::Call(-1))[-1]) & 0x0000FFFF);
  69 #elif defined(__aarch64__)
  70   EXPECT_EQ(0xD4000001u, ((uint32_t*)Syscall::Call(-1))[-1]);  // SVC 0
  71 #else
  72 #warning Incomplete test case; need port for target platform
  73 #endif
  74 }
  75
  76 TEST(Syscall, TrivialSyscallNoArgs) {
  77   // Test that we can do basic system calls
  78   EXPECT_EQ(Syscall::Call(__NR_getpid), syscall(__NR_getpid));
  79 }
  80
  81 TEST(Syscall, TrivialSyscallOneArg) {
  82   int new_fd;
  83   // Duplicate standard error and close it.
  84   ASSERT_GE(new_fd = Syscall::Call(__NR_dup, 2), 0);
  85   int close_return_value = IGNORE_EINTR(Syscall::Call(__NR_close, new_fd));
  86   ASSERT_EQ(close_return_value, 0);
  87 }
  88
  89 TEST(Syscall, TrivialFailingSyscall) {
  90   errno = -42;
  91   int ret = Syscall::Call(__NR_dup, -1);
  92   ASSERT_EQ(-EBADF, ret);
  93   // Verify that Syscall::Call does not touch errno.
  94   ASSERT_EQ(-42, errno);
  95 }
  96
  97 // SIGSYS trap handler that will be called on __NR_uname.
  98 intptr_t CopySyscallArgsToAux(const struct arch_seccomp_data& args, void* aux) {
  99   // |aux| is our BPF_AUX pointer.
 100   std::vector<uint64_t>* const seen_syscall_args =
 101       static_cast<std::vector<uint64_t>*>(aux);
 102   BPF_ASSERT(arraysize(args.args) == 6);
 103   seen_syscall_args->assign(args.args, args.args + arraysize(args.args));
 104   return -ENOMEM;
 105 }
 106
 107 class CopyAllArgsOnUnamePolicy : public bpf_dsl::Policy {
 108  public:
 109   explicit CopyAllArgsOnUnamePolicy(std::vector<uint64_t>* aux) : aux_(aux) {}
 110   ~CopyAllArgsOnUnamePolicy() override {}
 111
 112   ResultExpr EvaluateSyscall(int sysno) const override {
 113     DCHECK(SandboxBPF::IsValidSyscallNumber(sysno));
 114     if (sysno == __NR_uname) {
 115       return Trap(CopySyscallArgsToAux, aux_);
 116     } else {
 117       return Allow();
 118     }
 119   }
 120
 121  private:
 122   std::vector<uint64_t>* aux_;
 123
 124   DISALLOW_COPY_AND_ASSIGN(CopyAllArgsOnUnamePolicy);
 125 };
 126
 127 // We are testing Syscall::Call() by making use of a BPF filter that
 128 // allows us
 129 // to inspect the system call arguments that the kernel saw.
 130 BPF_TEST(Syscall,
 131          SyntheticSixArgs,
 132          CopyAllArgsOnUnamePolicy,
 133          std::vector<uint64_t> /* (*BPF_AUX) */) {
 134   const int kExpectedValue = 42;
 135   // In this test we only pass integers to the kernel. We might want to make
 136   // additional tests to try other types. What we will see depends on
 137   // implementation details of kernel BPF filters and we will need to document
 138   // the expected behavior very clearly.
 139   int syscall_args[6];
 140   for (size_t i = 0; i < arraysize(syscall_args); ++i) {
 141     syscall_args[i] = kExpectedValue + i;
 142   }
 143
 144   // We could use pretty much any system call we don't need here. uname() is
 145   // nice because it doesn't have any dangerous side effects.
 146   BPF_ASSERT(Syscall::Call(__NR_uname,
 147                            syscall_args[0],
 148                            syscall_args[1],
 149                            syscall_args[2],
 150                            syscall_args[3],
 151                            syscall_args[4],
 152                            syscall_args[5]) == -ENOMEM);
 153
 154   // We expect the trap handler to have copied the 6 arguments.
 155   BPF_ASSERT(BPF_AUX->size() == 6);
 156
 157   // Don't loop here so that we can see which argument does cause the failure
 158   // easily from the failing line.
 159   // uint64_t is the type passed to our SIGSYS handler.
 160   BPF_ASSERT((*BPF_AUX)[0] == static_cast<uint64_t>(syscall_args[0]));
 161   BPF_ASSERT((*BPF_AUX)[1] == static_cast<uint64_t>(syscall_args[1]));
 162   BPF_ASSERT((*BPF_AUX)[2] == static_cast<uint64_t>(syscall_args[2]));
 163   BPF_ASSERT((*BPF_AUX)[3] == static_cast<uint64_t>(syscall_args[3]));
 164   BPF_ASSERT((*BPF_AUX)[4] == static_cast<uint64_t>(syscall_args[4]));
 165   BPF_ASSERT((*BPF_AUX)[5] == static_cast<uint64_t>(syscall_args[5]));
 166 }
 167
 168 TEST(Syscall, ComplexSyscallSixArgs) {
 169   int fd;
 170   ASSERT_LE(0,
 171             fd = Syscall::Call(__NR_openat, AT_FDCWD, "/dev/null", O_RDWR, 0L));
 172
 173   // Use mmap() to allocate some read-only memory
 174   char* addr0;
 175   ASSERT_NE(
 176       (char*)NULL,
 177       addr0 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
 178                                                     (void*)NULL,
 179                                                     4096,
 180                                                     PROT_READ,
 181                                                     MAP_PRIVATE | MAP_ANONYMOUS,
 182                                                     fd,
 183                                                     0L)));
 184
 185   // Try to replace the existing mapping with a read-write mapping
 186   char* addr1;
 187   ASSERT_EQ(addr0,
 188             addr1 = reinterpret_cast<char*>(
 189                 Syscall::Call(kMMapNr,
 190                               addr0,
 191                               4096L,
 192                               PROT_READ | PROT_WRITE,
 193                               MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
 194                               fd,
 195                               0L)));
 196   ++*addr1;  // This should not seg fault
 197
 198   // Clean up
 199   EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr1, 4096L));
 200   EXPECT_EQ(0, IGNORE_EINTR(Syscall::Call(__NR_close, fd)));
 201
 202   // Check that the offset argument (i.e. the sixth argument) is processed
 203   // correctly.
 204   ASSERT_GE(
 205       fd = Syscall::Call(__NR_openat, AT_FDCWD, "/proc/self/exe", O_RDONLY, 0L),
 206       0);
 207   char* addr2, *addr3;
 208   ASSERT_NE((char*)NULL,
 209             addr2 = reinterpret_cast<char*>(Syscall::Call(
 210                 kMMapNr, (void*)NULL, 8192L, PROT_READ, MAP_PRIVATE, fd, 0L)));
 211   ASSERT_NE((char*)NULL,
 212             addr3 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
 213                                                           (void*)NULL,
 214                                                           4096L,
 215                                                           PROT_READ,
 216                                                           MAP_PRIVATE,
 217                                                           fd,
 218 #if defined(__NR_mmap2)
 219                                                           1L
 220 #else
 221                                                           4096L
 222 #endif
 223                                                           )));
 224   EXPECT_EQ(0, memcmp(addr2 + 4096, addr3, 4096));
 225
 226   // Just to be absolutely on the safe side, also verify that the file
 227   // contents matches what we are getting from a read() operation.
 228   char buf[8192];
 229   EXPECT_EQ(8192, Syscall::Call(__NR_read, fd, buf, 8192L));
 230   EXPECT_EQ(0, memcmp(addr2, buf, 8192));
 231
 232   // Clean up
 233   EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr2, 8192L));
 234   EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr3, 4096L));
 235   EXPECT_EQ(0, IGNORE_EINTR(Syscall::Call(__NR_close, fd)));
 236 }
 237
 238 }  // namespace
 239
 240 }  // namespace sandbox