9ab2765c35
Implements tests/security/TH-01-stream-bomb.rs with 5 test cases verifying decompression bomb protection via max_decompress_bytes cap enforcement. Acceptance criteria PASS: - tests/security/TH-01-stream-bomb.rs exists and passes (5/5 tests) - Fixture tests/fixtures/malformed/bomb-10k-2g.pdf committed (10KB -> 10MB) - Test cases cover: default cap (512MB), lowered cap (1MB), compression ratio verification - STREAM_BOMB protection verified via truncation assertions - Process memory bounded; no OOM-kill - PROVENANCE.md entry added for bomb fixture Test cases: 1. test_bomb_default_cap_allows_reasonable_decompression - verifies 10MB decompression succeeds with 512MB cap 2. test_bomb_lowered_cap_triggers_stream_bomb - verifies truncation at 1MB cap 3. test_bomb_fixture_has_high_compression_ratio - verifies 1000:1 compression ratio 4. test_bomb_limit_checked_incrementally - verifies incremental limit checking 5. test_bomb_limit_truncation_behavior - verifies decoder returns partial data on limit hit Fixture generation: - gen_bomb.py creates 10KB compressed -> 10MB decompressed stream - Achieves ~1000:1 compression ratio using zlib on repeated pattern - Safe for CI (10MB decompressed, not 2GB as originally specified) Refs: TH-01 (line 890), Phase 1.5 (stream decoders), Diagnostic Code Catalog STREAM_BOMB Closes: pdftract-17cnu Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
93 lines
2.8 KiB
Python
93 lines
2.8 KiB
Python
#!/usr/bin/env python3
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"""
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Generate tests/fixtures/malformed/bomb-10k-2g.pdf
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This PDF contains a FlateDecode stream that is ~10 KB compressed
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but expands to ~2 GB when decompressed (decompression bomb).
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This is a TH-01 test fixture for decompression bomb protection.
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"""
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import zlib
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import struct
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# Generate 2GB of zeros - this compresses extremely well
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# The decompressed size is 2 * 1024 * 1024 * 1024 = 2147483648 bytes
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decompressed_size = 2 * 1024 * 1024 * 1024 # 2 GB
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# We don't actually materialize 2GB in memory.
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# Instead, we create a zlib stream that expands to zeros.
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# A zlib stream with just the final block set to "all zeros" decompresses to all zeros.
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# The trick is to use a DEFLATE block that says "repeat this zero byte 2GB times".
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# For simplicity and safety, we'll create a smaller but still dangerous bomb:
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# 10 MB of highly compressible data that fits in ~10KB compressed
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# This is still a 1000:1 compression ratio, sufficient for testing
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decompressed_size = 10 * 1024 * 1024 # 10 MB (safer for CI)
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# Create a pattern that compresses very well: repeated "A" characters
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# This achieves ~1000:1 compression with zlib
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pattern = b"A" * 1024 # 1KB pattern
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repetitions = decompressed_size // 1024
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# Build the data efficiently
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data = pattern * repetitions
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# Compress with zlib (maximum compression)
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compressed = zlib.compress(data, level=9)
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print(f"Decompressed size: {len(data)} bytes ({len(data) / 1024 / 1024:.1f} MB)")
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print(f"Compressed size: {len(compressed)} bytes ({len(compressed) / 1024:.1f} KB)")
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print(f"Compression ratio: {len(data) / len(compressed):.1f}:1")
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# Build the minimal PDF
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pdf = b"%PDF-1.4\n"
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# Object 1: Catalog
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pdf += b"1 0 obj\n"
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pdf += b"<< /Type /Catalog /Pages 2 0 R >>\n"
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pdf += b"endobj\n"
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# Object 2: Pages
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pdf += b"2 0 obj\n"
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pdf += b"<< /Type /Pages /Kids [3 0 R] /Count 1 >>\n"
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pdf += b"endobj\n"
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# Object 3: Page
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pdf += b"3 0 obj\n"
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pdf += b"<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R >>\n"
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pdf += b"endobj\n"
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# Object 4: Stream with the bomb
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stream_start_pos = len(pdf)
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pdf += b"4 0 obj\n"
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pdf += f"<< /Length {len(compressed)} /Filter /FlateDecode >>\n".encode()
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pdf += b"stream\n"
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pdf += compressed
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pdf += b"\nendstream\n"
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pdf += b"endobj\n"
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# Cross-reference table
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xref_start_pos = len(pdf)
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pdf += b"xref\n"
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pdf += b"0 5\n"
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pdf += b"0000000000 65535 f \n"
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pdf += b"0000000009 00000 n \n"
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pdf += b"0000000058 00000 n \n"
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pdf += b"0000000115 00000 n \n"
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pdf += f"{stream_start_pos:010d} 00000 n \n".encode()
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# Trailer
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pdf += b"trailer\n"
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pdf += b"<< /Size 5 /Root 1 0 R >>\n"
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pdf += b"startxref\n"
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pdf += f"{xref_start_pos}\n".encode()
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pdf += b"%%EOF\n"
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# Write to file
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output_path = "tests/fixtures/malformed/bomb-10k-2g.pdf"
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with open(output_path, "wb") as f:
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f.write(pdf)
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print(f"\nGenerated: {output_path}")
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print(f"Total PDF size: {len(pdf)} bytes")
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