Make FFmpeg MP4 diagnostics format-safe

src/rust/src/demuxer/mod.rs

@@ -41,5 +41,7 @@ pub mod demuxer_data;
 pub mod dvdraw;
 #[cfg(feature = "enable_mp4_ffmpeg")]
 pub mod mp4;
+#[cfg(any(feature = "enable_mp4_ffmpeg", test))]
+mod mprint;
 pub mod scc;
 pub mod stream_functions;

src/rust/src/demuxer/mp4.rs

@@ -13,6 +13,8 @@
 //!
 //! - `dvdsub` (DVD bitmap subtitles) via OCR through vobsub_decoder
 
+use super::mprint::mprint_arguments;
+
 #[cfg(feature = "enable_mp4_ffmpeg")]
 use rsmpeg::avformat::AVFormatContextInput;
 #[cfg(feature = "enable_mp4_ffmpeg")]
@@ -82,6 +84,12 @@ extern "C" {
     fn encode_sub(enc_ctx: *mut encoder_ctx, sub: *mut cc_subtitle) -> c_int;
 }
 
+#[cfg(feature = "enable_mp4_ffmpeg")]
+unsafe fn mprint_text(message: *const c_char) {
+    let (format, message) = mprint_arguments(message);
+    mprint(format, message);
+}
+
 /// Track types we can extract captions from
 #[derive(Debug, Clone, Copy, PartialEq)]
 enum TrackType {
@@ -143,20 +151,20 @@ pub unsafe fn processmp4_rust(ctx: *mut lib_ccx_ctx, path: &CStr, sub: *mut cc_s
     let path_display = String::from_utf8_lossy(path_str);
 
     let open_msg = format!("Opening '{}' with FFmpeg: \0", path_display);
-    mprint(open_msg.as_ptr() as *const c_char);
+    mprint_text(open_msg.as_ptr() as *const c_char);
 
     // Open the file with FFmpeg
     let fmt_ctx = match AVFormatContextInput::open(path, None, &mut None) {
         Ok(ctx) => ctx,
         Err(e) => {
             let err_msg = format!("Failed to open input file with FFmpeg: {}\n\0", e);
-            mprint(err_msg.as_ptr() as *const c_char);
+            mprint_text(err_msg.as_ptr() as *const c_char);
             return -2;
         }
     };
 
     let ok_msg = b"ok\n\0";
-    mprint(ok_msg.as_ptr() as *const c_char);
+    mprint_text(ok_msg.as_ptr() as *const c_char);
 
     // Set up encoder/decoder
     let dec_ctx = update_decoder_list(ctx);
@@ -225,7 +233,7 @@ pub unsafe fn processmp4_rust(ctx: *mut lib_ccx_ctx, path: &CStr, sub: *mut cc_s
                 "Track {}, type={} timescale={}\n\0",
                 i, type_name, timescale
             );
-            mprint(msg.as_ptr() as *const c_char);
+            mprint_text(msg.as_ptr() as *const c_char);
 
             tracks.push(TrackInfo {
                 stream_index: i,
@@ -261,11 +269,11 @@ pub unsafe fn processmp4_rust(ctx: *mut lib_ccx_ctx, path: &CStr, sub: *mut cc_s
         hevc_count,
         cc_count
     );
-    mprint(summary.as_ptr() as *const c_char);
+    mprint_text(summary.as_ptr() as *const c_char);
 
     if tracks.is_empty() {
         let msg = b"No processable tracks found\n\0";
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
         return 0;
     }
 
@@ -490,25 +498,25 @@ pub unsafe fn processmp4_rust(ctx: *mut lib_ccx_ctx, path: &CStr, sub: *mut cc_s
     ccx_mp4_report_progress(ctx, 100, 100);
 
     let close_msg = b"\nClosing media: ok\n\0";
-    mprint(close_msg.as_ptr() as *const c_char);
+    mprint_text(close_msg.as_ptr() as *const c_char);
 
     if avc_count > 0 {
         let msg = format!("Found {} AVC track(s). \0", avc_count);
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
     } else {
         let msg = b"Found no AVC track(s). \0";
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
     }
     if hevc_count > 0 {
         let msg = format!("Found {} HEVC track(s). \0", hevc_count);
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
     }
     if cc_count > 0 {
         let msg = format!("Found {} CC track(s).\n\0", cc_count);
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
     } else {
         let msg = b"Found no dedicated CC track(s).\n\0";
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
     }
 
     (*ctx).freport.mp4_cc_track_cnt = cc_count as u32;
@@ -639,24 +647,24 @@ pub unsafe fn dumpchapters_rust(_ctx: *mut lib_ccx_ctx, path: &CStr) -> c_int {
     let path_display = String::from_utf8_lossy(path_str);
 
     let open_msg = format!("Opening '{}': \0", path_display);
-    mprint(open_msg.as_ptr() as *const c_char);
+    mprint_text(open_msg.as_ptr() as *const c_char);
 
     let fmt_ctx = match AVFormatContextInput::open(path, None, &mut None) {
         Ok(ctx) => ctx,
         Err(_) => {
             let msg = b"failed to open\n\0";
-            mprint(msg.as_ptr() as *const c_char);
+            mprint_text(msg.as_ptr() as *const c_char);
             return 5;
         }
     };
 
     let ok_msg = b"ok\n\0";
-    mprint(ok_msg.as_ptr() as *const c_char);
+    mprint_text(ok_msg.as_ptr() as *const c_char);
 
     let nb_chapters = (*fmt_ctx.as_ptr()).nb_chapters as usize;
     if nb_chapters == 0 {
         let msg = b"No chapters information found!\n\0";
-        mprint(msg.as_ptr() as *const c_char);
+        mprint_text(msg.as_ptr() as *const c_char);
         return 0;
     }
 
@@ -667,7 +675,7 @@ pub unsafe fn dumpchapters_rust(_ctx: *mut lib_ccx_ctx, path: &CStr) -> c_int {
     };
 
     let writing_msg = format!("Writing chapters into {}\n\0", out_name);
-    mprint(writing_msg.as_ptr() as *const c_char);
+    mprint_text(writing_msg.as_ptr() as *const c_char);
 
     use std::io::Write;
     for i in 0..nb_chapters {

src/rust/src/demuxer/mprint.rs

@@ -0,0 +1,25 @@
+use std::os::raw::c_char;
+
+const TEXT_FORMAT: &[u8] = b"%s\0";
+
+pub(super) fn mprint_arguments(message: *const c_char) -> (*const c_char, *const c_char) {
+    (TEXT_FORMAT.as_ptr() as *const c_char, message)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::ffi::{CStr, CString};
+
+    #[test]
+    fn text_uses_a_literal_format() {
+        let message = CString::new("Opening '%s%n.mp4' with FFmpeg").unwrap();
+        let (format, argument) = mprint_arguments(message.as_ptr());
+
+        assert_eq!(unsafe { CStr::from_ptr(format) }.to_bytes(), b"%s");
+        assert_eq!(
+            unsafe { CStr::from_ptr(argument) }.to_bytes(),
+            message.as_bytes()
+        );
+    }
+}