base/security_unittest.cc

   1 // Copyright (c) 2013 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 <fcntl.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <sys/stat.h>
  10 #include <sys/types.h>
  11
  12 #include <algorithm>
  13 #include <limits>
  14
  15 #include "base/files/file_util.h"
  16 #include "base/logging.h"
  17 #include "base/memory/scoped_ptr.h"
  18 #include "build/build_config.h"
  19 #include "testing/gtest/include/gtest/gtest.h"
  20
  21 #if defined(OS_POSIX)
  22 #include <sys/mman.h>
  23 #include <unistd.h>
  24 #endif
  25
  26 using std::nothrow;
  27 using std::numeric_limits;
  28
  29 namespace {
  30
  31 // This function acts as a compiler optimization barrier. We use it to
  32 // prevent the compiler from making an expression a compile-time constant.
  33 // We also use it so that the compiler doesn't discard certain return values
  34 // as something we don't need (see the comment with calloc below).
  35 template <typename Type>
  36 Type HideValueFromCompiler(volatile Type value) {
  37 #if defined(__GNUC__)
  38   // In a GCC compatible compiler (GCC or Clang), make this compiler barrier
  39   // more robust than merely using "volatile".
  40   __asm__ volatile ("" : "+r" (value));
  41 #endif  // __GNUC__
  42   return value;
  43 }
  44
  45 // - NO_TCMALLOC (should be defined if compiled with use_allocator!="tcmalloc")
  46 // - ADDRESS_SANITIZER and SYZYASAN because they have their own memory allocator
  47 // - IOS does not use tcmalloc
  48 // - OS_MACOSX does not use tcmalloc
  49 #if !defined(NO_TCMALLOC) && !defined(ADDRESS_SANITIZER) && \
  50     !defined(OS_IOS) && !defined(OS_MACOSX) && !defined(SYZYASAN)
  51   #define TCMALLOC_TEST(function) function
  52 #else
  53   #define TCMALLOC_TEST(function) DISABLED_##function
  54 #endif
  55
  56 // TODO(jln): switch to std::numeric_limits<int>::max() when we switch to
  57 // C++11.
  58 const size_t kTooBigAllocSize = INT_MAX;
  59
  60 // Detect runtime TCMalloc bypasses.
  61 bool IsTcMallocBypassed() {
  62 #if defined(OS_LINUX)
  63   // This should detect a TCMalloc bypass from Valgrind.
  64   char* g_slice = getenv("G_SLICE");
  65   if (g_slice && !strcmp(g_slice, "always-malloc"))
  66     return true;
  67 #elif defined(OS_WIN)
  68   // This should detect a TCMalloc bypass from setting
  69   // the CHROME_ALLOCATOR environment variable.
  70   char* allocator = getenv("CHROME_ALLOCATOR");
  71   if (allocator && strcmp(allocator, "tcmalloc"))
  72     return true;
  73 #endif
  74   return false;
  75 }
  76
  77 bool CallocDiesOnOOM() {
  78 // The sanitizers' calloc dies on OOM instead of returning NULL.
  79 // The wrapper function in base/process_util_linux.cc that is used when we
  80 // compile without TCMalloc will just die on OOM instead of returning NULL.
  81 #if defined(ADDRESS_SANITIZER) || \
  82     defined(MEMORY_SANITIZER) || \
  83     defined(THREAD_SANITIZER) || \
  84     (defined(OS_LINUX) && defined(NO_TCMALLOC))
  85   return true;
  86 #else
  87   return false;
  88 #endif
  89 }
  90
  91 // Fake test that allow to know the state of TCMalloc by looking at bots.
  92 TEST(SecurityTest, TCMALLOC_TEST(IsTCMallocDynamicallyBypassed)) {
  93   printf("Malloc is dynamically bypassed: %s\n",
  94          IsTcMallocBypassed() ? "yes." : "no.");
  95 }
  96
  97 // The MemoryAllocationRestrictions* tests test that we can not allocate a
  98 // memory range that cannot be indexed via an int. This is used to mitigate
  99 // vulnerabilities in libraries that use int instead of size_t.  See
 100 // crbug.com/169327.
 101
 102 TEST(SecurityTest, TCMALLOC_TEST(MemoryAllocationRestrictionsMalloc)) {
 103   if (!IsTcMallocBypassed()) {
 104     scoped_ptr<char, base::FreeDeleter> ptr(static_cast<char*>(
 105         HideValueFromCompiler(malloc(kTooBigAllocSize))));
 106     ASSERT_TRUE(!ptr);
 107   }
 108 }
 109
 110 TEST(SecurityTest, TCMALLOC_TEST(MemoryAllocationRestrictionsCalloc)) {
 111   if (!IsTcMallocBypassed()) {
 112     scoped_ptr<char, base::FreeDeleter> ptr(static_cast<char*>(
 113         HideValueFromCompiler(calloc(kTooBigAllocSize, 1))));
 114     ASSERT_TRUE(!ptr);
 115   }
 116 }
 117
 118 TEST(SecurityTest, TCMALLOC_TEST(MemoryAllocationRestrictionsRealloc)) {
 119   if (!IsTcMallocBypassed()) {
 120     char* orig_ptr = static_cast<char*>(malloc(1));
 121     ASSERT_TRUE(orig_ptr);
 122     scoped_ptr<char, base::FreeDeleter> ptr(static_cast<char*>(
 123         HideValueFromCompiler(realloc(orig_ptr, kTooBigAllocSize))));
 124     ASSERT_TRUE(!ptr);
 125     // If realloc() did not succeed, we need to free orig_ptr.
 126     free(orig_ptr);
 127   }
 128 }
 129
 130 typedef struct {
 131   char large_array[kTooBigAllocSize];
 132 } VeryLargeStruct;
 133
 134 TEST(SecurityTest, TCMALLOC_TEST(MemoryAllocationRestrictionsNew)) {
 135   if (!IsTcMallocBypassed()) {
 136     scoped_ptr<VeryLargeStruct> ptr(
 137         HideValueFromCompiler(new (nothrow) VeryLargeStruct));
 138     ASSERT_TRUE(!ptr);
 139   }
 140 }
 141
 142 TEST(SecurityTest, TCMALLOC_TEST(MemoryAllocationRestrictionsNewArray)) {
 143   if (!IsTcMallocBypassed()) {
 144     scoped_ptr<char[]> ptr(
 145         HideValueFromCompiler(new (nothrow) char[kTooBigAllocSize]));
 146     ASSERT_TRUE(!ptr);
 147   }
 148 }
 149
 150 // The tests bellow check for overflows in new[] and calloc().
 151
 152 #if defined(OS_IOS) || defined(OS_WIN) || defined(THREAD_SANITIZER)
 153   #define DISABLE_ON_IOS_AND_WIN_AND_TSAN(function) DISABLED_##function
 154 #else
 155   #define DISABLE_ON_IOS_AND_WIN_AND_TSAN(function) function
 156 #endif
 157
 158 // There are platforms where these tests are known to fail. We would like to
 159 // be able to easily check the status on the bots, but marking tests as
 160 // FAILS_ is too clunky.
 161 void OverflowTestsSoftExpectTrue(bool overflow_detected) {
 162   if (!overflow_detected) {
 163 #if defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_MACOSX)
 164     // Sadly, on Linux, Android, and OSX we don't have a good story yet. Don't
 165     // fail the test, but report.
 166     printf("Platform has overflow: %s\n",
 167            !overflow_detected ? "yes." : "no.");
 168 #else
 169     // Otherwise, fail the test. (Note: EXPECT are ok in subfunctions, ASSERT
 170     // aren't).
 171     EXPECT_TRUE(overflow_detected);
 172 #endif
 173   }
 174 }
 175
 176 // Test array[TooBig][X] and array[X][TooBig] allocations for int overflows.
 177 // IOS doesn't honor nothrow, so disable the test there.
 178 // Crashes on Windows Dbg builds, disable there as well.
 179 TEST(SecurityTest, DISABLE_ON_IOS_AND_WIN_AND_TSAN(NewOverflow)) {
 180   const size_t kArraySize = 4096;
 181   // We want something "dynamic" here, so that the compiler doesn't
 182   // immediately reject crazy arrays.
 183   const size_t kDynamicArraySize = HideValueFromCompiler(kArraySize);
 184   // numeric_limits are still not constexpr until we switch to C++11, so we
 185   // use an ugly cast.
 186   const size_t kMaxSizeT = ~static_cast<size_t>(0);
 187   ASSERT_EQ(numeric_limits<size_t>::max(), kMaxSizeT);
 188   const size_t kArraySize2 = kMaxSizeT / kArraySize + 10;
 189   const size_t kDynamicArraySize2 = HideValueFromCompiler(kArraySize2);
 190   {
 191     scoped_ptr<char[][kArraySize]> array_pointer(new (nothrow)
 192         char[kDynamicArraySize2][kArraySize]);
 193     OverflowTestsSoftExpectTrue(!array_pointer);
 194   }
 195   // On windows, the compiler prevents static array sizes of more than
 196   // 0x7fffffff (error C2148).
 197 #if !defined(OS_WIN) || !defined(ARCH_CPU_64_BITS)
 198   {
 199     scoped_ptr<char[][kArraySize2]> array_pointer(new (nothrow)
 200         char[kDynamicArraySize][kArraySize2]);
 201     OverflowTestsSoftExpectTrue(!array_pointer);
 202   }
 203 #endif  // !defined(OS_WIN) || !defined(ARCH_CPU_64_BITS)
 204 }
 205
 206 // Call calloc(), eventually free the memory and return whether or not
 207 // calloc() did succeed.
 208 bool CallocReturnsNull(size_t nmemb, size_t size) {
 209   scoped_ptr<char, base::FreeDeleter> array_pointer(
 210       static_cast<char*>(calloc(nmemb, size)));
 211   // We need the call to HideValueFromCompiler(): we have seen LLVM
 212   // optimize away the call to calloc() entirely and assume
 213   // the pointer to not be NULL.
 214   return HideValueFromCompiler(array_pointer.get()) == NULL;
 215 }
 216
 217 // Test if calloc() can overflow.
 218 TEST(SecurityTest, CallocOverflow) {
 219   const size_t kArraySize = 4096;
 220   const size_t kMaxSizeT = numeric_limits<size_t>::max();
 221   const size_t kArraySize2 = kMaxSizeT / kArraySize + 10;
 222   if (!CallocDiesOnOOM()) {
 223     EXPECT_TRUE(CallocReturnsNull(kArraySize, kArraySize2));
 224     EXPECT_TRUE(CallocReturnsNull(kArraySize2, kArraySize));
 225   } else {
 226     // It's also ok for calloc to just terminate the process.
 227 #if defined(GTEST_HAS_DEATH_TEST)
 228     EXPECT_DEATH(CallocReturnsNull(kArraySize, kArraySize2), "");
 229     EXPECT_DEATH(CallocReturnsNull(kArraySize2, kArraySize), "");
 230 #endif  // GTEST_HAS_DEATH_TEST
 231   }
 232 }
 233
 234 #if defined(OS_LINUX) && defined(__x86_64__)
 235 // Check if ptr1 and ptr2 are separated by less than size chars.
 236 bool ArePointersToSameArea(void* ptr1, void* ptr2, size_t size) {
 237   ptrdiff_t ptr_diff = reinterpret_cast<char*>(std::max(ptr1, ptr2)) -
 238                        reinterpret_cast<char*>(std::min(ptr1, ptr2));
 239   return static_cast<size_t>(ptr_diff) <= size;
 240 }
 241
 242 // Check if TCMalloc uses an underlying random memory allocator.
 243 TEST(SecurityTest, TCMALLOC_TEST(RandomMemoryAllocations)) {
 244   if (IsTcMallocBypassed())
 245     return;
 246   size_t kPageSize = 4096;  // We support x86_64 only.
 247   // Check that malloc() returns an address that is neither the kernel's
 248   // un-hinted mmap area, nor the current brk() area. The first malloc() may
 249   // not be at a random address because TCMalloc will first exhaust any memory
 250   // that it has allocated early on, before starting the sophisticated
 251   // allocators.
 252   void* default_mmap_heap_address =
 253       mmap(0, kPageSize, PROT_READ|PROT_WRITE,
 254            MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 255   ASSERT_NE(default_mmap_heap_address,
 256             static_cast<void*>(MAP_FAILED));
 257   ASSERT_EQ(munmap(default_mmap_heap_address, kPageSize), 0);
 258   void* brk_heap_address = sbrk(0);
 259   ASSERT_NE(brk_heap_address, reinterpret_cast<void*>(-1));
 260   ASSERT_TRUE(brk_heap_address != NULL);
 261   // 1 MB should get us past what TCMalloc pre-allocated before initializing
 262   // the sophisticated allocators.
 263   size_t kAllocSize = 1<<20;
 264   scoped_ptr<char, base::FreeDeleter> ptr(
 265       static_cast<char*>(malloc(kAllocSize)));
 266   ASSERT_TRUE(ptr != NULL);
 267   // If two pointers are separated by less than 512MB, they are considered
 268   // to be in the same area.
 269   // Our random pointer could be anywhere within 0x3fffffffffff (46bits),
 270   // and we are checking that it's not withing 1GB (30 bits) from two
 271   // addresses (brk and mmap heap). We have roughly one chance out of
 272   // 2^15 to flake.
 273   const size_t kAreaRadius = 1<<29;
 274   bool in_default_mmap_heap = ArePointersToSameArea(
 275       ptr.get(), default_mmap_heap_address, kAreaRadius);
 276   EXPECT_FALSE(in_default_mmap_heap);
 277
 278   bool in_default_brk_heap = ArePointersToSameArea(
 279       ptr.get(), brk_heap_address, kAreaRadius);
 280   EXPECT_FALSE(in_default_brk_heap);
 281
 282   // In the implementation, we always mask our random addresses with
 283   // kRandomMask, so we use it as an additional detection mechanism.
 284   const uintptr_t kRandomMask = 0x3fffffffffffULL;
 285   bool impossible_random_address =
 286       reinterpret_cast<uintptr_t>(ptr.get()) & ~kRandomMask;
 287   EXPECT_FALSE(impossible_random_address);
 288 }
 289
 290 #endif  // defined(OS_LINUX) && defined(__x86_64__)
 291
 292 }  // namespace