kacrab_protocol/compression/
gzip.rs

1//! Gzip codec (`flate2` Rust backend).
2
3use std::io::Write;
4
5use super::{Compression, CompressionError, CompressionErrorKind, Result};
6
7const DEFAULT_GZIP_LEVEL: u32 = 6;
8
9/// Compress `payload` at the given level (`None` -> codec default `6`). Only the lower bound is
10/// clamped (negative levels become `0`); higher values pass through to `flate2` unchanged.
11pub fn compress_with_level(payload: &[u8], level: Option<i32>) -> Result<Vec<u8>> {
12    let lvl = level.map_or(DEFAULT_GZIP_LEVEL, |l| l.max(0).cast_unsigned());
13    let mut encoder = flate2::write::GzEncoder::new(Vec::new(), flate2::Compression::new(lvl));
14    encoder
15        .write_all(payload)
16        .map_err(|e| encode_err(e.to_string()))?;
17    encoder.finish().map_err(|e| encode_err(e.to_string()))
18}
19
20/// Decompress `payload`, bounded by [`super::MAX_DECOMPRESSED_LEN`].
21pub fn decompress(payload: &[u8]) -> Result<Vec<u8>> {
22    decompress_bounded(payload, super::MAX_DECOMPRESSED_LEN)
23}
24
25/// Decompress `payload`, refusing to produce more than `max_len` bytes —
26/// gzip expands up to ~1000:1, so an unbounded read is a decompression bomb.
27pub fn decompress_bounded(payload: &[u8], max_len: usize) -> Result<Vec<u8>> {
28    let decoder = flate2::read::GzDecoder::new(payload);
29    super::read_to_end_bounded(decoder, max_len, Compression::Gzip)
30}
31
32const fn encode_err(message: String) -> CompressionError {
33    CompressionError::new(
34        Compression::Gzip,
35        CompressionErrorKind::EncodeFailed { message },
36    )
37}
38
39#[cfg(test)]
40mod tests {
41    use super::{super::CompressionErrorKind, compress_with_level, decompress, decompress_bounded};
42
43    #[test]
44    fn decompress_bounded_rejects_a_decompression_bomb() {
45        // Highly repetitive data compresses to a tiny payload that would
46        // expand far past the bound.
47        let payload = vec![0u8; 4096];
48        let compressed = compress_with_level(&payload, None).unwrap();
49
50        let err = decompress_bounded(&compressed, 64).unwrap_err();
51        assert!(
52            matches!(
53                err.kind,
54                CompressionErrorKind::DecompressedTooLarge { limit: 64 }
55            ),
56            "expected DecompressedTooLarge, got {:?}",
57            err.kind
58        );
59    }
60
61    #[test]
62    fn decompress_bounded_allows_output_at_exactly_the_limit() {
63        let payload = vec![0u8; 4096];
64        let compressed = compress_with_level(&payload, None).unwrap();
65
66        assert_eq!(decompress_bounded(&compressed, 4096).unwrap(), payload);
67        assert_eq!(decompress(&compressed).unwrap(), payload);
68    }
69}
kacrab_protocol/compression/gzip.rs

kacrab_protocol/compression/
gzip.rs
