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fix for empty string table parsing in COFF files. fixes issue #502. #503

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Merged
m4b merged 1 commit into from
Jan 20, 2026
Merged

fix for empty string table parsing in COFF files. fixes issue #502. #503

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49 changes: 49 additions & 0 deletions src/pe/header.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1823,4 +1823,53 @@ mod tests {
assert_eq!(header.dos_header.pe_pointer, 0x40);
assert_eq!(header.coff_header.number_of_sections, 3);
}

// MASM COFF file that has an empty string table
static EMPTY_STRING_TABLE_OBJ: [u8; 424] = [
0x64, 0x86, 0x03, 0x00, 0xf3, 0xcb, 0x20, 0x69, 0x02, 0x01, 0x00, 0x00, 0x09, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x2e, 0x74, 0x65, 0x78, 0x74, 0x24, 0x6d, 0x6e, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x8c, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x00, 0x50, 0x60,
0x2e, 0x64, 0x61, 0x74, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x50, 0xc0, 0x2e, 0x64, 0x65, 0x62, 0x75,
0x67, 0x24, 0x53, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x74, 0x00, 0x00, 0x00,
0x8d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x40, 0x00, 0x10, 0x42, 0xc3, 0x04, 0x00, 0x00, 0x00, 0xf1, 0x00, 0x00, 0x00, 0x68,
0x00, 0x00, 0x00, 0x2d, 0x00, 0x01, 0x11, 0x00, 0x00, 0x00, 0x00, 0x43, 0x3a, 0x5c, 0x55,
0x73, 0x65, 0x72, 0x73, 0x5c, 0x43, 0x6f, 0x6e, 0x74, 0x6f, 0x73, 0x6f, 0x5c, 0x77, 0x69,
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0x2e, 0x6f, 0x62, 0x6a, 0x00, 0x37, 0x00, 0x3c, 0x11, 0x03, 0x02, 0x00, 0x00, 0xd0, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x00, 0x2a, 0x00, 0x84, 0x86, 0x00,
0x00, 0x4d, 0x69, 0x63, 0x72, 0x6f, 0x73, 0x6f, 0x66, 0x74, 0x20, 0x28, 0x52, 0x29, 0x20,
0x4d, 0x61, 0x63, 0x72, 0x6f, 0x20, 0x41, 0x73, 0x73, 0x65, 0x6d, 0x62, 0x6c, 0x65, 0x72,
0x00, 0x00, 0x00, 0x40, 0x63, 0x6f, 0x6d, 0x70, 0x2e, 0x69, 0x64, 0x84, 0x86, 0x03, 0x01,
0xff, 0xff, 0x00, 0x00, 0x03, 0x00, 0x40, 0x66, 0x65, 0x61, 0x74, 0x2e, 0x30, 0x30, 0x10,
0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0x03, 0x00, 0x2e, 0x74, 0x65, 0x78, 0x74, 0x24,
0x6d, 0x6e, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x03, 0x01, 0x01, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x2e, 0x64, 0x61, 0x74, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00,
0x00, 0x03, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2e, 0x64, 0x65, 0x62, 0x75, 0x67, 0x24, 0x53, 0x00,
0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x03, 0x01, 0x74, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x65, 0x6d, 0x70,
0x74, 0x79, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x20, 0x00, 0x02, 0x00,
0x04, 0x00, 0x00, 0x00,
];

#[test]
fn parse_coff_with_empty_string_table() {
// This test verifies that a COFF file with an empty string table can be parsed
// The file has a string table with only the length field (4 bytes)
let coff = Coff::parse(&EMPTY_STRING_TABLE_OBJ).unwrap();

// Should have sections, symbols, and a minimal string table
assert_eq!(coff.header.number_of_sections, 3);
assert_eq!(coff.header.number_of_symbol_table, 9);
assert!(coff.strings.is_some());

// String table should be empty (only contains the length field)
let strings = coff.strings.unwrap();
assert_eq!(strings.len(), 0); // Empty string table content
}
}
6 changes: 5 additions & 1 deletion src/strtab.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -105,8 +105,12 @@ impl<'a> Strtab<'a> {
) -> error::Result<Self> {
let (end, overflow) = offset.overflowing_add(len);

// For COFF with an empty string table, len is zero and offset is equal to bytes.len().
// In this case an empty slice is returned.
// ELF has explicit checks for string tables with sh_size of zero.

// Handle completely invalid offset
if offset >= bytes.len() {
if offset > bytes.len() {
#[cfg(feature = "alloc")]
return Err(error::Error::Malformed(format!(
"String table offset ({}) is beyond file boundary ({})",
Expand Down