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