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fuzz技术和漏洞挖掘

分类： 网络与安全

2020-07-22 21:36:31

声明：谢绝一切形式的转载。

在计算机的世界中，有输入的地方就有江湖，因为有输入的地方，就有可能有漏洞。比如xss，目前很多大型网站依然存在xss漏洞。

一个简单的程序

下面的程序是求一个数的平方。 

    
	
	
  1. 
		#include
	
    2. 

	
  2. 
		int main(){
	
    3. 

	
  3. 
		 int a =0;
	
    4. 

	
  4. 
		 scanf("%d",&a);
	
    5. 

	
  5. 
		 printf("%d\n",a*a);
	
    6. 

	
  6. 
		 return 0;
	
    7. 

	
  7. 
		}
	
    8.

编译 gcc test.c 运行 ./a.out 在这里插入图片描述通过观察，很容易看出当输入一些"畸形"数据的时候会导致程序运行出现错误。如果只有二进制文件，有什么办法可以检测出这种错误？

Fuzz

A software testing technique, often automated or semi-automated, that involves passing invalid, unexpected or random input to a program and monitor result for crashes, failed assertions, races, leaks, etc.

术语

● Target

  • Consumes an array of bytes
  • Calls the code we want to test

● Fuzzer

  • A tool that feed the target with different random inputs

● Corpus

  • A set of valid & invalid inputs for the target
  • Collected manually, by fuzzing, or by crawling

fuzz的种类

  • Generation Based ：通过对目标协议或文件格式建模的方法，从零开始产生测试用例，没有先前的状态
  • Mutation Based ：基于一些规则，从已有的数据样本或存在的状态变异
  • Evolutionary ：包含了上述两种，同时会根据代码覆盖率的回馈进行变异。

传统fuzz

传统的 fuzz 大多通过对已有的样本 按照预先设置好的规则 进行变异产生测试用例，然后喂给 目标程序同时监控目标程序的运行状态。这类 fuzz 有很多，比如: peach , FileFuzz 等。

实战

相关文件位于:

生成测试用例

radamsa 是一个 测试用例生成引擎，它是通过对已有的样本进行变异来生成新的测试用例。下面的代码主要通过调用 radamsa ,然后随机选取 seed_corpus 目录中的文件名作为参数，传递给 radamsa 进行变异，把生成的测试用例，放到 work/corpus。 

    
	
	
  1. 
		#!/usr/bin/env python2
	
    2. 

	
  2. 
		# generate_testcases.py
	
    3. 

	
  3. 
		import os
	
    4. 

	
  4. 
		import random
	
    5. 

	
  5. 
		 
	
    6. 

	
  6. 
		WORK_DIR = 'work'
	
    7. 

	
  7. 
		 
	
    8. 

	
  8. 
		# Create work `directory` and `corpus` subdirectory.
	
    9. 

	
  9. 
		if not os.path.exists(WORK_DIR):
	
    10. 

	
  10. 
		 os.mkdir(WORK_DIR)
	
    11. 

	
  11. 
		 
	
    12. 

	
  12. 
		corpus_dir = os.path.join(WORK_DIR, 'corpus')
	
    13. 

	
  13. 
		if not os.path.exists(corpus_dir):
	
    14. 

	
  14. 
		 os.mkdir(corpus_dir)
	
    15. 

	
  15. 
		 
	
    16. 

	
  16. 
		seed_corpus_filenames = os.listdir('seed_corpus')
	
    17. 

	
  17. 
		 
	
    18. 

	
  18. 
		for i in xrange(1000):
	
    19. 

	
  19. 
		 random_seed_filename = random.choice(seed_corpus_filenames)
	
    20. 

	
  20. 
		 random_seed_filename = os.path.join('seed_corpus', random_seed_filename)
	
    21. 

	
  21. 
		 output_filename = os.path.join(WORK_DIR, 'corpus', 'testcase-%06d' % i)
	
    22. 

	
  22. 
		 cmd = 'bin/radamsa "%s" > "%s"' % (random_seed_filename, output_filename)
	
    23. 

	
  23. 
		 os.popen(cmd)
	
    24.
开始fuzz

fuzz程序如下，target是vscode，Corpus是上面程序生成的测试用例。 

    
	
	
  1. 
		#!/usr/bin/env python2
	
    2. 

	
  2. 
		# run_fuzzing.py
	
    3. 

	
  3. 
		import os
	
    4. 

	
  4. 
		import subprocess
	
    5. 

	
  5. 
		 
	
    6. 

	
  6. 
		WORK_DIR = 'work'
	
    7. 

	
  7. 
		 
	
    8. 

	
  8. 
		def checkOutput(s):
	
    9. 

	
  9. 
		 if 'Segmentation fault' in s or 'error' in s.lower():
	
    10. 

	
  10. 
		 return False
	
    11. 

	
  11. 
		 else:
	
    12. 

	
  12. 
		 return True
	
    13. 

	
  13. 
		 
	
    14. 

	
  14. 
		corpus_dir = os.path.join(WORK_DIR, 'corpus')
	
    15. 

	
  15. 
		corpus_filenames = os.listdir(corpus_dir)
	
    16. 

	
  16. 
		 
	
    17. 

	
  17. 
		for f in corpus_filenames:
	
    18. 

	
  18. 
		 testcase_path = os.path.join(corpus_dir, f)
	
    19. 

	
  19. 
		 cmd = ['/usr/bin/code', testcase_path]
	
    20. 

	
  20. 
		 process = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
	
    21. 

	
  21. 
		 output = process.communicate()[0]
	
    22. 

	
  22. 
		 if not checkOutput(output):
	
    23. 

	
  23. 
		 print testcase_path
	
    24. 

	
  24. 
		 print output
	
    25. 

	
  25. 
		 print '-' * 80
	
    26.

由于用于变异样本的选取 和 样本的变异方式是随机的，可能需要重复多次 样本生成 && fuzz 才能找到 crash。写个 bash 脚本，不断重复即可 

    
	
	
  1. 
		#!/bin/bash
	
    2. 

	
  2. 
		while [ "0" -lt "1" ]
	
    3. 

	
  3. 
		do
	
    4. 

	
  4. 
		 rm -rf ./work/
	
    5. 

	
  5. 
		 ./generate_testcases.py
	
    6. 

	
  6. 
		 ./run_fuzzing.py
	
    7. 

	
  7. 
		done
	
    8.

libFuzzer

feature

  • In-process, in-memory
  • Guided fuzz testing
  • Very effective at a function / protocol level
  • 1000x faster
  • It’s easy to write a libFuzzer-based fuzzer
  • Can be checked along with unit-tests

Memory Tools

● AddressSanitizer (aka ASan)

  • Detects use-after-free, buffer overflows (heap, stack, globals), stack-use-after-return, container-overflow
  • Cpu: 2x, memory 1.5x-3x

● MemorySanitizer (aka MSan)

  • Detects uninitialized memory reads
  • Cpu: 3x, memory: 2x
  • Special mode: origins

● UndefinedBehaviorSanitizer (aka UBSan)

  • Detects several classes of bugs (19?), esp on type confusion, signed-integer-overflow, undefined shift, etc.
  • Cpu: 10-50%
  • Memory: ~1x (no allocator, no shadow)

Helloworld-For-libFuzzer

本节资源位于:。

target 
    
	
	
  1. 
		bool VulnerableFunction1(const uint8_t* data, size_t size) {
	
    2. 

	
  2. 
		 bool result = false;
	
    3. 

	
  3. 
		 if (size >= 3) {
	
    4. 

	
  4. 
		 result = data[0] == 'F' &&
	
    5. 

	
  5. 
		 data[1] == 'U' &&
	
    6. 

	
  6. 
		 data[2] == 'Z' &&
	
    7. 

	
  7. 
		 data[3] == 'Z';
	
    8. 

	
  8. 
		 }
	
    9. 

	
  9. 
		 
	
    10. 

	
  10. 
		 return result;
	
    11. 

	
  11. 
		}
	
    12.

在上面的程序中，当size=3的时候，访问data[3]会产生越界。

fuzzer

first_fuzzer.cc 

    
	
	
  1. 
		extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
	
    2. 

	
  2. 
		 VulnerableFunction1(data, size);
	
    3. 

	
  3. 
		 return 0;
	
    4. 

	
  4. 
		}
	
    5.

编译： clang++-g-fsanitize=address,fuzzer first_fuzzer.cc 运行fuzzer: ./a.out2>&1|grep ERROR 在这里插入图片描述完整的输出 

    
	
	
  1. 
		INFO: Seed: 100908111
	
    2. 

	
  2. 
		INFO: Loaded 1 modules (35 inline 8-bit counters): 35 [0x7f8120, 0x7f8143), 
	
    3. 

	
  3. 
		INFO: Loaded 1 PC tables (35 PCs): 35 [0x5b7f68,0x5b8198), 
	
    4. 

	
  4. 
		INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes
	
    5. 

	
  5. 
		INFO: A corpus is not provided, starting from an empty corpus
	
    6. 

	
  6. 
		#2    INITED cov: 3 ft: 3 corp: 1/1b exec/s: 0 rss: 27Mb
	
    7. 

	
  7. 
		#15    NEW    cov: 4 ft: 4 corp: 2/4b lim: 4 exec/s: 0 rss: 27Mb L: 3/3 MS: 3 CopyPart-CrossOver-InsertByte-
	
    8. 

	
  8. 
		#1156    NEW    cov: 5 ft: 5 corp: 3/7b lim: 14 exec/s: 0 rss: 27Mb L: 3/3 MS: 1 CMP- DE: "F\x00"-
	
    9. 

	
  9. 
		#2688    NEW    cov: 6 ft: 6 corp: 4/15b lim: 29 exec/s: 0 rss: 27Mb L: 8/8 MS: 2 ChangeByte-InsertRepeatedBytes-
	
    10. 

	
  10. 
		#2704    REDUCE cov: 6 ft: 6 corp: 4/13b lim: 29 exec/s: 0 rss: 28Mb L: 6/6 MS: 1 EraseBytes-
	
    11. 

	
  11. 
		#2844    REDUCE cov: 6 ft: 6 corp: 4/12b lim: 29 exec/s: 0 rss: 28Mb L: 5/5 MS: 5 CrossOver-PersAutoDict-CrossOver-EraseBytes-EraseBytes- DE: "F\x00"-
	
    12. 

	
  12. 
		#3080    REDUCE cov: 6 ft: 6 corp: 4/11b lim: 29 exec/s: 0 rss: 28Mb L: 4/4 MS: 1 EraseBytes-
	
    13. 

	
  13. 
		#3172    REDUCE cov: 6 ft: 6 corp: 4/10b lim: 29 exec/s: 0 rss: 28Mb L: 3/3 MS: 2 CopyPart-EraseBytes-
	
    14. 

	
  14. 
		#10828    REDUCE cov: 7 ft: 7 corp: 5/70b lim: 104 exec/s: 0 rss: 28Mb L: 60/60 MS: 1 InsertRepeatedBytes-
	
    15. 

	
  15. 
		#10840    REDUCE cov: 7 ft: 7 corp: 5/29b lim: 104 exec/s: 0 rss: 28Mb L: 19/19 MS: 2 PersAutoDict-CrossOver- DE: "F\x00"-
	
    16. 

	
  16. 
		#10933    REDUCE cov: 7 ft: 7 corp: 5/24b lim: 104 exec/s: 0 rss: 28Mb L: 14/14 MS: 3 ChangeByte-InsertByte-EraseBytes-
	
    17. 

	
  17. 
		#11125    REDUCE cov: 7 ft: 7 corp: 5/21b lim: 104 exec/s: 0 rss: 28Mb L: 11/11 MS: 2 InsertByte-EraseBytes-
	
    18. 

	
  18. 
		#11361    REDUCE cov: 7 ft: 7 corp: 5/18b lim: 104 exec/s: 0 rss: 28Mb L: 8/8 MS: 1 EraseBytes-
	
    19. 

	
  19. 
		#11482    REDUCE cov: 7 ft: 7 corp: 5/14b lim: 104 exec/s: 0 rss: 28Mb L: 4/4 MS: 1 EraseBytes-
	
    20. 

	
  20. 
		=================================================================
	
    21. 

	
  21. 
		==3357==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000040f73 at pc 0x00000059b461 bp 0x7fff657ee560 sp 0x7fff657ee558
	
    22. 

	
  22. 
		READ of size 1 at 0x602000040f73 thread T0
	
    23. 

	
  23. 
		 #0 0x59b460 in VulnerableFunction1(unsigned char const*, unsigned long) /home/burning/linux/libfuzzer-workshop-master/lessons/04/./vulnerable_functions.h:22:14
	
    24. 

	
  24. 
		 #1 0x59bde4 in LLVMFuzzerTestOneInput /home/burning/linux/libfuzzer-workshop-master/lessons/04/first_fuzzer.cc:10:3
	
    25. 

	
  25. 
		 #2 0x466186 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:556
	
    26. 

	
  26. 
		 #3 0x46b7e9 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:470
	
    27. 

	
  27. 
		 #4 0x46b7e9 in fuzzer::Fuzzer::MutateAndTestOne() /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:699
	
    28. 

	
  28. 
		 #5 0x46e80f in fuzzer::Fuzzer::Loop(std::Fuzzer::vector >&) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:830
	
    29. 

	
  29. 
		 #6 0x456b99 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:824
	
    30. 

	
  30. 
		 #7 0x41f522 in main /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerMain.cpp:19
	
    31. 

	
  31. 
		 #8 0x7fa043c3eb96 in __libc_start_main /build/glibc-2ORdQG/glibc-2.27/csu/../csu/libc-start.c:310
	
    32. 

	
  32. 
		 #9 0x41f599 in _start (/home/burning/linux/libfuzzer-workshop-master/lessons/04/a.out+0x41f599)
	
    33. 

	
  33. 
		 
	
    34. 

	
  34. 
		0x602000040f73 is located 0 bytes to the right of 3-byte region [0x602000040f70,0x602000040f73)
	
    35. 

	
  35. 
		allocated by thread T0 here:
	
    36. 

	
  36. 
		 #0 0x597b58 in operator new[](unsigned long) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/asan/asan_new_delete.cpp:102
	
    37. 

	
  37. 
		 #1 0x466092 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:541
	
    38. 

	
  38. 
		 #2 0x46b7e9 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:470
	
    39. 

	
  39. 
		 #3 0x46b7e9 in fuzzer::Fuzzer::MutateAndTestOne() /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:699
	
    40. 

	
  40. 
		 #4 0x46e80f in fuzzer::Fuzzer::Loop(std::Fuzzer::vector >&) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:830
	
    41. 

	
  41. 
		 #5 0x456b99 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:824
	
    42. 

	
  42. 
		 #6 0x41f522 in main /home/burning/linux/libfuzzer-workshop-master/src/llvm/projects/compiler-rt/lib/fuzzer/FuzzerMain.cpp:19
	
    43. 

	
  43. 
		 #7 0x7fa043c3eb96 in __libc_start_main /build/glibc-2ORdQG/glibc-2.27/csu/../csu/libc-start.c:310
	
    44. 

	
  44. 
		 
	
    45. 

	
  45. 
		SUMMARY: AddressSanitizer: heap-buffer-overflow /home/burning/linux/libfuzzer-workshop-master/lessons/04/./vulnerable_functions.h:22:14 in VulnerableFunction1(unsigned char const*, unsigned long)
	
    46. 

	
  46. 
		Shadow bytes around the buggy address:
	
    47. 

	
  47. 
		 0x0c0480000190: fa fa fd fa fa fa fd fa fa fa fd fa fa fa fd fa
	
    48. 

	
  48. 
		 0x0c04800001a0: fa fa fd fa fa fa fd fa fa fa fd fa fa fa fd fa
	
    49. 

	
  49. 
		 0x0c04800001b0: fa fa fd fa fa fa fd fa fa fa fd fa fa fa fd fa
	
    50. 

	
  50. 
		 0x0c04800001c0: fa fa fd fd fa fa fd fd fa fa fd fa fa fa fd fa
	
    51. 

	
  51. 
		 0x0c04800001d0: fa fa fd fa fa fa fd fa fa fa fd fa fa fa fd fa
	
    52. 

	
  52. 
		=>0x0c04800001e0: fa fa fd fa fa fa fd fa fa fa fd fa fa fa[03]fa
	
    53. 

	
  53. 
		 0x0c04800001f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
	
    54. 

	
  54. 
		 0x0c0480000200: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
	
    55. 

	
  55. 
		 0x0c0480000210: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
	
    56. 

	
  56. 
		 0x0c0480000220: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
	
    57. 

	
  57. 
		 0x0c0480000230: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
	
    58. 

	
  58. 
		Shadow byte legend (one shadow byte represents 8 application bytes):
	
    59. 

	
  59. 
		 Addressable: 00
	
    60. 

	
  60. 
		 Partially addressable: 01 02 03 04 05 06 07 
	
    61. 

	
  61. 
		 Heap left redzone: fa
	
    62. 

	
  62. 
		 Freed heap region: fd
	
    63. 

	
  63. 
		 Stack left redzone: f1
	
    64. 

	
  64. 
		 Stack mid redzone: f2
	
    65. 

	
  65. 
		 Stack right redzone: f3
	
    66. 

	
  66. 
		 Stack after return: f5
	
    67. 

	
  67. 
		 Stack use after scope: f8
	
    68. 

	
  68. 
		 Global redzone: f9
	
    69. 

	
  69. 
		 Global init order: f6
	
    70. 

	
  70. 
		 Poisoned by user: f7
	
    71. 

	
  71. 
		 Container overflow: fc
	
    72. 

	
  72. 
		 Array cookie: ac
	
    73. 

	
  73. 
		 Intra object redzone: bb
	
    74. 

	
  74. 
		 ASan internal: fe
	
    75. 

	
  75. 
		 Left alloca redzone: ca
	
    76. 

	
  76. 
		 Right alloca redzone: cb
	
    77. 

	
  77. 
		 Shadow gap: cc
	
    78. 

	
  78. 
		==3357==ABORTING
	
    79. 

	
  79. 
		MS: 5 CopyPart-EraseBytes-PersAutoDict-EraseBytes-ChangeBinInt- DE: "F\x00"-; base unit: 9dbab5c181e3d878fa7e1229929a99dc1f04abf4
	
    80. 

	
  80. 
		0x46,0x55,0x5a,
	
    81. 

	
  81. 
		FUZ
	
    82. 

	
  82. 
		artifact_prefix='./'; Test unit written to ./crash-0eb8e4ed029b774d80f2b66408203801cb982a60
	
    83.

正常的话应该可以看到类似上面的输出，这里对其中的一些信息解析一下

  • Seed: 1608565063 说明这次的种子数据
  • max_len 用于设置最大的数据长度
  • 接下来 # 开头的行是 fuzz 过程中找到的路径信息
  • 最后一行是触发漏洞的测试用例

重现crash: 

    
	
	
  1. 
		ASAN_OPTIONS=symbolize=1 ./a.out ./crash-0eb8e4ed029b774d80f2b66408203801cb982a60
	
    2. 

	
  2. 
		# ASAN_OPTIONS=symbolize=1 用于显示 栈的符号信息
	
    3.

写在最后

文章中涉及到很多英文内容，个人不能翻译到信、达、雅的地步，所以就保留原文了。

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