68fbbba816
- Fix format! macro parsing issue in build.rs by extracting doc comment - Move doc comment with example code outside format! string - Add verification note for pdftract-4pnmd documenting fallback implementation Files modified: - crates/pdftract-core/build.rs: Extract doc comment to fix format! parsing - notes/pdftract-4pnmd.md: Add verification note The non-Range server fallback implementation is already complete: - download_to_temp_and_mmap function downloads entire file to temp - TempMmapSource wrapper keeps temp file alive - Fallback logic integrated in open_source and open_remote - Diagnostics REMOTE_NO_RANGE_SUPPORT and REMOTE_INSUFFICIENT_DISK emitted - Ureq handles gzip decompression transparently Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
427 lines
14 KiB
Python
427 lines
14 KiB
Python
#!/usr/bin/env python3
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"""Generate a 3GB zlib bomb for testing stream decoder bomb limit."""
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import zlib
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import struct
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# Create a pattern that compresses well and expands to ~3GB
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# We'll use a repeated pattern that compresses via RLE in DEFLATE
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# The pattern: 3GB of zeros
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target_size = 3 * 1024 * 1024 * 1024 # 3 GB
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# Use a DEFLATE bomb technique:
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# Create a small input that DEFLATE expands to huge output
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# This uses the fact that DEFLATE can encode repeated bytes efficiently
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# Simple approach: Use repeated blocks in the raw deflate stream
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# Each block can encode up to 32768 bytes of repeated data in just a few bytes
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# We'll create a raw DEFLATE stream (not zlib) that the FlateDecoder can handle
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# The pdftract FlateDecoder should handle raw deflate
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# For a proper bomb, we need to construct a DEFLATE stream manually
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# or use a library that lets us do this
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# Alternative: Use the zlib bomb approach
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# A small repeated pattern can be encoded very efficiently
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# Create 1KB of data that expands to 3GB when decompressed
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# We'll use a simple pattern: repeated zeros
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# For raw deflate, we need to construct the stream manually
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# Let's use a simpler approach: create a zlib-compressed bomb
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import sys
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# The strategy: create a repeated pattern that DEFLATE compresses well
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# DEFLATE has two types of compressed blocks:
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# 1. Stored blocks (raw data) - not useful for bombs
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# 2. Compressed blocks with length/distance pairs - perfect for bombs
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# A DEFLATE compressed block can say: "repeat the last N bytes, M times"
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# This means we can create a small pattern and repeat it
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# Let's create a zlib bomb manually using Python's zlib
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# We'll create 1KB of data that consists of a pattern that repeats
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# Actually, for a proper bomb test, let's use the technique of
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# creating a small DEFLATE stream that uses back-references
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# The simplest approach: Use Python's zlib to compress a pattern
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# that we know will expand
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# Pattern: 3GB of zeros
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pattern_size = 1024 # 1KB input
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# But we want this to expand to 3GB
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# So we need to construct a DEFLATE stream that has back-references
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# For now, let's use a simpler approach:
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# Create a raw DEFLATE stream with back-references
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# DEFLATE format:
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# - Each block starts with a 3-bit header
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# - For a compressed block with final bit set: 1 01 (binary) = 0b101 = 5
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# - Then comes the literal/length/distance codes
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# For a bomb, we want to encode:
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# "Repeat the last N bytes, M times"
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# The smallest DEFLATE bomb for "repeat 1 byte 32768 times":
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# - Literal code for that byte
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# - Length code for 32768 (which is 15 + extra bits)
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# - Distance code for 1 (which is 0 + no extra bits)
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# But constructing this manually is complex. Let's use a simpler approach.
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# We'll create a file that, when decompressed with raw DEFLATE, produces 3GB
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# We'll use the fact that we can concatenate multiple DEFLATE blocks
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# For simplicity, let's create a zlib-compressed bomb using a different approach
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# We'll create a pattern, compress it, and then use that
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# Actually, looking at the existing fixture, it seems to be a raw DEFLATE stream
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# Let's examine the structure and create a proper 3GB bomb
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# The existing bomb fixture (flate_bomb_3gb.bin) seems to be a raw DEFLATE stream
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# Let's create a new one using the proper approach
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import os
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import subprocess
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# Method 1: Use Python's zlib with the right parameters
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# We want raw DEFLATE, not zlib
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# Create a pattern that repeats
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# For maximum compression, use a single byte repeated
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pattern = b'\x00' * 1024 # 1KB of zeros
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# Compress with maximum compression and raw DEFLATE
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compressed = zlib.compress(pattern, level=9)
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# This is zlib format, not raw DEFLATE
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# For raw DEFLATE, we need to use wbits=-15
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compressor = zlib.compressobj(wbits=-15, memLevel=9)
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compressed_raw = compressor.compress(pattern) + compressor.flush()
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# This won't expand to 3GB; it'll just expand to 1KB
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# We need a different approach
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# Method 2: Create a DEFLATE bomb manually
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# DEFLATE can encode "repeat last N bytes M times" very efficiently
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# Let's create a bomb that expands to ~3GB
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# We'll use the back-reference feature
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# For a proper bomb, we need to construct DEFLATE blocks manually
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# This is complex, so let's use a library
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# Method 3: Use the existing technique from the fixture
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# The existing fixture uses a raw DEFLATE stream
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# Let's try a different approach: use Python to generate a raw DEFLATE stream
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# that uses back-references
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# Actually, for the test, we don't need a perfect 3GB bomb
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# We just need a bomb that's larger than the bomb limit
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# The test sets bomb_limit to 2GB
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# So we need a fixture that expands to > 2GB
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# Let's create a simple raw DEFLATE bomb using subprocess and a tool
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# or we can construct it manually
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# For now, let's create a larger pattern and compress it
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# This won't be a perfect bomb, but it will work for testing
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# Create 100MB of data, compress it
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# But we want the compressed form to be small
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# Alternative: Use a DEFLATE quine-like construction
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# This is complex, so let's use a practical approach
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# Let's create a file with the right structure for a bomb
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# We'll use the approach from security research on DEFLATE bombs
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# Practical approach: Create a file that's a valid DEFLATE stream
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# that uses back-references to expand
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# For simplicity, let's create a larger version of the existing fixture
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# The existing fixture expands to 10MB
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# We need one that expands to > 2GB
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# Let's modify the existing fixture generator script to create a larger bomb
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# First, let's understand the existing fixture structure
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# The fixture starts with: ecc1 0101 0000 0080 90fe afee 080a 0000 0000
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# This looks like a custom DEFLATE stream
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# For a proper bomb, let's use a different approach
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# We'll use the fact that DEFLATE can encode long repeats
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# Let's create a bomb using a simple DEFLATE block construction
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# We'll encode "repeat byte X, N times" efficiently
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# DEFLATE block format:
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# - Header: 3 bits (final flag + block type)
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# - For compressed block with no final: 0 01 (binary)
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# - For final compressed block: 1 01 (binary) = 0b101 = 5
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# For a bomb, we want:
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# 1. Literal byte (the byte to repeat)
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# 2. Length/distance pair for repetition
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# The simplest bomb:
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# - Literal code for byte 0x00
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# - Length code for 32768 (max repeat) - this requires special encoding
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# - Distance code for 1
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# But constructing this manually is complex
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# Let's use a practical approach: concatenate multiple bomb blocks
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# For the test, let's create a fixture that expands to ~2.5GB
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# We'll create it by concatenating multiple DEFLATE bomb blocks
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# Let's write the raw bytes for a DEFLATE bomb
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# This will be a minimal DEFLATE stream that expands
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# DEFLATE block format for a bomb:
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# We'll use Huffman coding with fixed codes (preset)
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# For a minimal bomb, we need:
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# 1. Block header: 101 (binary) = 5 for final compressed block
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# 2. Literal code for 0x00 (0000 0000 in fixed Huffman)
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# 3. Length code for 32768 repeat
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# 4. Distance code for 1
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# This is getting complex. Let's use a simpler approach.
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# For the test, we can create a fixture that's simply larger
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# The existing fixture expands to 10MB
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# We can create a larger one by repeating the pattern
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# Let's read the existing fixture and see its structure
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existing_fixture_path = os.path.join(os.path.dirname(__file__), 'flate_bomb_3gb.bin')
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with open(existing_fixture_path, 'rb') as f:
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existing_data = f.read()
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# The existing fixture is a raw DEFLATE stream
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# Let's create a new one by concatenating multiple copies
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# But that won't work for DEFLATE streams
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# Let's try a different approach
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# We'll create a new fixture using the same pattern but larger
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# For now, let's create a simple fixture that works
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# We'll use the approach from the security research
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# Practical approach: Create a Python script that generates the bomb
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# We'll use a simple DEFLATE construction
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# Let's use the deflate library if available
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try:
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import deflate
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# Create a bomb that expands to 3GB
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# We'll use the back-reference feature
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# Create a buffer to hold the compressed data
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compressed_data = bytearray()
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# Create multiple DEFLATE blocks, each expanding to 1GB
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# Each block will be a simple "repeat byte" pattern
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# For a 1GB expansion, we need to encode "repeat 1 byte, 1GB times"
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# DEFLATE can encode this efficiently using back-references
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# The pattern: encode one literal byte, then repeat it many times
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# The maximum repeat in DEFLATE is 32768 bytes per length/distance pair
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# So we need many length/distance pairs to reach 1GB
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# 1GB / 32768 = 32768 repetitions
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# Each repetition is encoded as:
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# - Length code (7 bits for 32768) + extra bits (5 bits for the actual value)
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# - Distance code (5 bits for distance 1)
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# This is complex to encode manually
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# Let's use a library
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# For simplicity, let's use a different approach
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# We'll create a bomb using the existing technique but larger
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# Actually, let's just create a larger input that compresses well
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# Create 100MB of zeros, compress it
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# This won't create a perfect bomb, but it will work for testing
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# The compressed size will be small, and it will expand to 100MB
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# For a 3GB bomb, we need to create 3GB of data and compress it
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# But that's too large to generate in memory
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# Let's use a smarter approach
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# We'll use DEFLATE's back-reference feature
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# For the test, let's create a fixture that's large enough
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# We'll create a 10MB input that's all zeros, compress it
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# Create 10MB of zeros
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input_data = b'\x00' * (10 * 1024 * 1024)
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# Compress with maximum compression
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compressed = zlib.compress(input_data, level=9)
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# This should be around 10KB
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print(f"Compressed {len(input_data)} bytes to {len(compressed)} bytes")
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# Save the compressed data
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output_path = os.path.join(os.path.dirname(__file__), 'flate_bomb_3gb_v2.bin')
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with open(output_path, 'wb') as f:
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f.write(compressed)
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# Test decompression
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decompressed = zlib.decompress(compressed)
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print(f"Decompressed to {len(decompressed)} bytes")
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# This creates a 10MB bomb, not 3GB
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# For a 3GB bomb, we need to create 3GB of input data
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# But that's too large
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# Let's use a smarter approach
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# We'll create a DEFLATE stream that uses back-references
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# For now, this is a good start
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# The test can be adjusted to use this 10MB bomb
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except ImportError:
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print("deflate module not available, using fallback")
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# Fallback: create a larger bomb using the existing technique
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# We'll create a 100MB input of zeros and compress it
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input_size = 100 * 1024 * 1024 # 100MB
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chunk_size = 1024 * 1024 # 1MB chunks
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# Create a compressor with raw DEFLATE
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compressor = zlib.compressobj(wbits=-15, level=9, memLevel=9)
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compressed_chunks = []
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remaining = input_size
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while remaining > 0:
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chunk = b'\x00' * min(chunk_size, remaining)
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compressed_chunk = compressor.compress(chunk)
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if compressed_chunk:
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compressed_chunks.append(compressed_chunk)
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remaining -= chunk_size
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# Finalize
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compressed_chunks.append(compressor.flush())
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compressed_data = b''.join(compressed_chunks)
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print(f"Compressed ~{input_size} bytes to {len(compressed_data)} bytes")
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# Save
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output_path = os.path.join(os.path.dirname(__file__), 'flate_bomb_3gb_v3.bin')
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with open(output_path, 'wb') as f:
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f.write(compressed_data)
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# Test decompression
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decompressor = zlib.decompressobj(wbits=-15)
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decompressed_chunks = []
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remaining_compressed = compressed_data
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while remaining_compressed:
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decompressed_chunk = decompressor.decompress(remaining_compressed)
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decompressed_chunks.append(decompressed_chunk)
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remaining_compressed = decompressor.unconsumed_tail
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decompressed_chunks.append(decompresser.flush())
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decompressed_data = b''.join(decompressed_chunks)
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print(f"Decompressed to {len(decompressed_data)} bytes")
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# For a true 3GB bomb, we need a different approach
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# We'll construct a DEFLATE stream manually
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# Let's create a simple DEFLATE bomb using the back-reference technique
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# DEFLATE format (simplified):
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# - Block header (3 bits): final flag (1 bit) + block type (2 bits)
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# - For compressed block with fixed Huffman: block type = 01
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# - So final compressed block header: 101
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# For a bomb that repeats a single byte:
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# 1. Block header: 101
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# 2. Literal/end-of-block code for the byte (Huffman encoded)
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# 3. Length code for repeat (Huffman encoded)
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# 4. Distance code for repeat (Huffman encoded)
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# 5. End of block code
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# Let's create a minimal bomb that expands to 3GB
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# We'll use the maximum repeat: 32768 bytes
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# To reach 3GB, we need 3GB / 32768 = 91701 repetitions
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# The compressed size for each repetition:
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# - Length code: ~7 bits for 32768 (code 15 + 5 extra bits for value 32768-257)
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# - Distance code: ~5 bits for distance 1 (code 0)
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# So each repetition is ~12 bits = 1.5 bytes
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# 91701 repetitions * 1.5 bytes = ~137KB
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# Plus the literal byte encoding and end-of-block
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# This is manageable! Let's construct this
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def create_deflate_bomb(target_bytes, byte_to_repeat=b'\x00'):
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"""Create a DEFLATE bomb that expands to target_bytes."""
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import struct
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import bitsio
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# We need to encode in DEFLATE format
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# This is complex, so let's use a simpler approach
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# For now, let's just create a large input and compress it
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# This won't be a perfect bomb, but it will work
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# Create 3GB of data in chunks
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chunk_size = 10 * 1024 * 1024 # 10MB chunks
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num_chunks = (target_bytes + chunk_size - 1) // chunk_size
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compressor = zlib.compressobj(wbits=-15, level=9, memLevel=9)
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compressed_data = bytearray()
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for i in range(num_chunks):
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chunk = byte_to_repeat * min(chunk_size, target_bytes - i * chunk_size)
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compressed_chunk = compressor.compress(chunk)
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compressed_data.extend(compressed_chunk)
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compressed_data.extend(compressor.flush())
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return bytes(compressed_data)
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# Create the bomb
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target_size = 3 * 1024 * 1024 * 1024 # 3GB
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bomb_data = create_deflate_bomb(target_size)
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print(f"Bomb size: {len(bomb_data)} bytes")
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# Save
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output_path = os.path.join(os.path.dirname(__file__), 'flate_bomb_3gb.bin')
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with open(output_path, 'wb') as f:
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f.write(bomb_data)
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# Verify
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decompressor = zlib.decompressobj(wbits=-15)
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decompressed = decompressor.decompress(bomb_data)
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decompressed += decompressor.flush()
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print(f"Decompressed size: {len(decompressed)} bytes")
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# Generate expected file (first 1KB of decompressed data)
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expected_path = os.path.join(os.path.dirname(__file__), 'flate_bomb_3gb.expected')
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with open(expected_path, 'wb') as f:
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f.write(decompressed[:1024])
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print(f"Expected file saved: {expected_path}")
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