Search for metadata if not found at end of file

The runner will now search for its metadata if it is not found at the end of the executable.
This can arise when the runner is modified after packing and other data is appended after it.

src/main.rs

@@ -282,7 +282,7 @@ fn main() {
     );
 
     let info = StarterInfo {
-        signature: [0x50, 0x45, 0x33, 0x44, 0x41, 0x54, 0x41, 0x00],
+        signature: WRAPPE_SIGNATURE,
         show_console,
         current_dir,
         verification,

src/types.rs

@@ -1,6 +1,7 @@
 pub use zerocopy::AsBytes;
 
 pub const WRAPPE_FORMAT: u8 = 201;
+pub const WRAPPE_SIGNATURE: [u8; 8] = [0x50, 0x45, 0x33, 0x44, 0x41, 0x54, 0x41, 0x00];
 pub const NAME_SIZE: usize = 128;
 pub const ARGS_SIZE: usize = 512;
 

startpe/Cargo.toml

@@ -30,6 +30,7 @@ strip = "symbols"
 dirs = "5.0.1"
 filetime = "0.2.23"
 fslock = "0.2.1"
+memchr = "2.7.1"
 memmap2 = "0.9.4"
 rayon = "1.9.0"
 twox-hash = { version = "1.6.3", default-features = false }

startpe/src/main.rs

@@ -17,6 +17,7 @@ use std::time::SystemTime;
 #[cfg(windows)]
 use winapi::um::wincon::{AttachConsole, ATTACH_PARENT_PROCESS};
 
+use memchr::memmem;
 use memmap2::MmapOptions;
 use zerocopy::Ref;
 
@@ -65,11 +66,35 @@ fn main() {
             .expect("couldn't memory map current executable")
     };
     let end = mmap.len();
+    if end < size_of::<StarterInfo>() {
+        panic!("file is too small ({} < {})", end, size_of::<StarterInfo>())
+    }
+
+    let mut signature = Vec::with_capacity(8);
+    signature.extend_from_slice(&WRAPPE_SIGNATURE_1[..4]);
+    signature.extend_from_slice(&WRAPPE_SIGNATURE_2[..4]);
+
+    let mut info_start = end - size_of::<StarterInfo>();
+    if mmap[info_start..info_start + 8] != signature[..] {
+        if let Some(pos) = memmem::rfind(&mmap[..info_start], &signature) {
+            info_start = pos;
+        } else {
+            panic!("couldn't find starter info")
+        }
+    }
 
-    let info_start = end - size_of::<StarterInfo>();
-    let info = Ref::<_, StarterInfo>::new(&mmap[info_start..end])
+    let info = Ref::<_, StarterInfo>::new(&mmap[info_start..info_start + size_of::<StarterInfo>()])
         .expect("couldn't read starter info")
         .into_ref();
+    if info.signature != signature[..] {
+        panic!("file signature is invalid")
+    }
+    if info.wrappe_format != WRAPPE_FORMAT {
+        panic!(
+            "runner version ({}) differs from wrapper version ({})",
+            WRAPPE_FORMAT, info.wrappe_format
+        );
+    }
 
     let show_information = info.show_information;
     let show_console = info.show_console;
@@ -94,16 +119,6 @@ fn main() {
         );
     }
 
-    if info.signature != [0x50, 0x45, 0x33, 0x44, 0x41, 0x54, 0x41, 0x00] {
-        panic!("file signature is invalid");
-    }
-    if info.wrappe_format != WRAPPE_FORMAT {
-        panic!(
-            "runner version ({}) differs from wrapper version ({})",
-            WRAPPE_FORMAT, info.wrappe_format
-        );
-    }
-
     let unpack_dir_name = std::str::from_utf8(
         &info.unpack_directory[0..(info
             .unpack_directory

startpe/src/types.rs

@@ -1,6 +1,8 @@
 pub use zerocopy::{FromBytes, FromZeroes};
 
 pub const WRAPPE_FORMAT: u8 = 201;
+pub const WRAPPE_SIGNATURE_1: [u8; 6] = [0x50, 0x45, 0x33, 0x44, 0x00, 0x00];
+pub const WRAPPE_SIGNATURE_2: [u8; 4] = [0x41, 0x54, 0x41, 0x00];
 pub const NAME_SIZE: usize = 128;
 pub const ARGS_SIZE: usize = 512;