Add SGI Image (.rgb) decoder

Author: mstoeckl

Cargo.toml

@@ -8,8 +8,9 @@ publish = false
 include = ["src", "tests/reference.rs"]
 
 [features]
-default = ["pcx"]
+default = ["pcx", "sgi"]
 pcx = ["dep:pcx"]
+sgi = []
 
 [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) |
+| RGB | [Wikipedia](https://en.wikipedia.org/wiki/Silicon_Graphics_Image) |
 
 ## New Formats
 

fuzz/Cargo.toml

@@ -25,3 +25,7 @@ members = ["."]
 [[bin]]
 name = "fuzzer_script_pcx"
 path = "fuzzers/fuzzer_script_pcx.rs"
+
+[[bin]]
+name = "fuzzer_script_sgi"
+path = "fuzzers/fuzzer_script_sgi.rs"

fuzz/fuzzers/fuzzer_script_sgi.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::sgi::SgiDecoder::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 +18,41 @@
 #[cfg(feature = "pcx")]
 pub mod pcx;
 
+#[cfg(feature = "sgi")]
+pub mod sgi;
+
 /// 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"));
     }
+
+    // SGI RGB images generally show up with a .rgb ending (whether or not they
+    // have 3 channels), and sometimes .bw (when grayscale) and .rgba. The
+    // extensions .sgi and .iris, while unambiguous, do not seem to have been
+    // used much. The extension .rgb is also used for a variety of other files,
+    // including bare image data, so to be sure it would be best to check both
+    // extension and leading bytes
+    let hook: for<'a> fn(
+        image::hooks::GenericReader<'a>,
+    ) -> image::ImageResult<Box<dyn image::ImageDecoder + 'a>> =
+        |r| Ok(Box::new(sgi::SgiDecoder::new(r)?));
+    image::hooks::register_decoding_hook("bw".into(), Box::new(hook));
+    image::hooks::register_decoding_hook("rgb".into(), Box::new(hook));
+    image::hooks::register_decoding_hook("rgba".into(), Box::new(hook));
+    image::hooks::register_decoding_hook("iris".into(), Box::new(hook));
+    let just_registered_sgi = image::hooks::register_decoding_hook("sgi".into(), Box::new(hook));
+    if just_registered_sgi {
+        // The main signature bytes are technically just 01 da, but this is short
+        // and the following storage and bpc fields are constrained well enough to
+        // efficiently match them as well
+        image::hooks::register_format_detection_hook("sgi".into(), b"\x01\xda\x00\x01", None);
+        image::hooks::register_format_detection_hook("sgi".into(), b"\x01\xda\x01\x01", None);
+        image::hooks::register_format_detection_hook("sgi".into(), b"\x01\xda\x00\x02", None);
+        image::hooks::register_format_detection_hook("sgi".into(), b"\x01\xda\x01\x02", None);
+    }
 }