Add XBM decoder

Author: mstoeckl

Cargo.toml

@@ -8,8 +8,9 @@ publish = false
 include = ["src", "tests/reference.rs"]
 
 [features]
-default = ["pcx"]
+default = ["pcx", "xbm"]
 pcx = ["dep:pcx"]
+xbm = []
 
 [dependencies]
 image = { version = "0.25.8", default-features = false }

README.md

@@ -6,6 +6,7 @@ Decoding support for additional image formats beyond those provided by the [`ima
 | Extension | File Format Description |
 | --------- | -------------------- |
 | PCX | [Wikipedia](https://en.wikipedia.org/wiki/PCX#PCX_file_format) |
+| XBM | [Wikipedia](https://en.wikipedia.org/wiki/X_BitMap) |
 
 ## New Formats
 

fuzz/Cargo.toml

@@ -14,7 +14,7 @@ image = { version = "0.25.8", default-features = false }
 
 [dependencies.image-extras]
 path = ".."
-features = []
+features = ["xbm"]
 [dependencies.libfuzzer-sys]
 version = "0.4"
 
@@ -25,3 +25,7 @@ members = ["."]
 [[bin]]
 name = "fuzzer_script_pcx"
 path = "fuzzers/fuzzer_script_pcx.rs"
+
+[[bin]]
+name = "fuzzer_script_xbm"
+path = "fuzzers/fuzzer_script_xbm.rs"

fuzz/README.md

@@ -5,6 +5,10 @@ For the possibly more up-to-date guide see <https://fuzz.rs/book/cargo-fuzz/setu
 > $ cargo install cargo-fuzz
 > $ cargo +nightly fuzz run fuzzer_script_<format>
 
+Fuzzing may progress faster for certain formats if seeded with a dictionary:
+
+> $ cargo +nightly fuzz run fuzzer_script_xbm -- -dict=fuzz/dictionaries/xbm.dict
+
 # Bug reports
 
 As explained in the project [README](../README.md), fuzzing is not a priority for

fuzz/dictionaries/xbm.dict

@@ -0,0 +1,16 @@
+"#define"
+"_width"
+"_height"
+"_x_hot"
+"_y_hot"
+"static"
+"unsigned"
+"char"
+"_bits[]"
+"="
+"{"
+"0x"
+"0X"
+","
+"}"
+";"

fuzz/fuzzers/fuzzer_script_xbm.rs

@@ -0,0 +1,22 @@
+#![no_main]
+#[macro_use]
+extern crate libfuzzer_sys;
+
+use image::ImageDecoder;
+use std::io::Cursor;
+
+fuzz_target!(|data: &[u8]| {
+    let reader = Cursor::new(data);
+    let Ok(mut decoder) = image_extras::xbm::XbmDecoder::new(reader) else {
+        return;
+    };
+    let mut limits = image::Limits::default();
+    limits.max_alloc = Some(1024 * 1024); // 1 MiB
+    if limits.reserve(decoder.total_bytes()).is_err() {
+        return;
+    }
+    if decoder.set_limits(limits).is_err() {
+        return;
+    }
+    let _ = std::hint::black_box(image::DynamicImage::from_decoder(decoder));
+});

src/lib.rs

@@ -18,13 +18,26 @@
 #[cfg(feature = "pcx")]
 pub mod pcx;
 
+#[cfg(feature = "xbm")]
+pub mod xbm;
+
 /// Register all enabled extra formats with the image crate.
 pub fn register() {
-    let just_registered = image::hooks::register_decoding_hook(
+    let just_registered_pcx = image::hooks::register_decoding_hook(
         "pcx".into(),
         Box::new(|r| Ok(Box::new(pcx::PCXDecoder::new(r)?))),
     );
-    if just_registered {
+    if just_registered_pcx {
         image::hooks::register_format_detection_hook("pcx".into(), &[0x0a, 0x0], Some(b"\xFF\xF8"));
     }
+
+    // XBM images are often valid C code and have no simple and reliably distinguishing file signature
+    image::hooks::register_decoding_hook(
+        "xbm".into(),
+        Box::new(|r| Ok(Box::new(xbm::XbmDecoder::new(r)?))),
+    );
+    image::hooks::register_decoding_hook(
+        "bm".into(),
+        Box::new(|r| Ok(Box::new(xbm::XbmDecoder::new(r)?))),
+    );
 }