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Fixing property parsing issue on Rust 1.78+ #129

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merged 6 commits into from
Jun 4, 2024
Merged

Fixing property parsing issue on Rust 1.78+ #129

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5eeec51
adding safety checks to support calls to from_raw_parts()
matterpreter May 2, 2024
1877643
adding temp debug prints
matterpreter May 2, 2024
3ba50fe
more triaging
matterpreter May 2, 2024
e168405
temporarily removing alignment check for strings
matterpreter May 2, 2024
61a58cb
trying to use Vec<u16> to fix pointer alignment weirdness
matterpreter May 2, 2024
3859982
cleanup
matterpreter May 2, 2024
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40 changes: 34 additions & 6 deletions src/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -371,17 +371,38 @@ macro_rules! impl_try_parse_primitive_array {
match prop_slice.property.info {
PropertyInfo::Array { .. } => {
// TODO: Check In and Out type and do a better type checking

// This property type has not been tested yet as I don't have a
// provider that uses it. It's possible that the buffer is not
// aligned correctly, which would cause this to fail.
let size = std::mem::size_of::<$T>();
let align = std::mem::align_of::<$T>();

if prop_slice.buffer.len() % size != 0 {
return Err(ParserError::LengthMismatch);
}

let count = prop_slice.buffer.len() / size;

if prop_slice.buffer.as_ptr() as usize % align != 0 {
return Err(ParserError::PropertyError(
"buffer alignment mismatch".into()
));
}

if size.checked_mul(count).is_none() || (size * count) > isize::MAX as usize {
return Err(ParserError::PropertyError(
"size overflow".into()
));
}

let slice = unsafe {
std::slice::from_raw_parts(
prop_slice.buffer.as_ptr() as *const $T,
count,
)
};

Ok(slice)
}
_ => Err(ParserError::InvalidType),
Expand Down Expand Up @@ -447,19 +468,26 @@ impl private::TryParse<String> for Parser<'_, '_> {
));
}

let mut wide = unsafe {
std::slice::from_raw_parts(
prop_slice.buffer.as_ptr() as *const u16,
prop_slice.buffer.len() / 2,
)
};
// std::slice::from_raw_parts requires a pointer to be aligned, but we can't
// guarantee that the buffer is aligned. In testing, I found that the buffer
// is in fact never aligned appropriately, so a cheap workaround is to copy
// the buffer into a new Vec<u16> and use that as the source for the slice
// until we can find a better solution.
let mut aligned_buffer = Vec::with_capacity(prop_slice.buffer.len() / 2);
for chunk in prop_slice.buffer.chunks_exact(2) {
let part = u16::from_ne_bytes([chunk[0], chunk[1]]);
aligned_buffer.push(part);
}

let mut wide = aligned_buffer.as_slice();

match wide.last() {
// remove the null terminator from the slice
Some(c) if c == &0 => wide = &wide[..wide.len() - 1],
_ => (),
}

// Decode UTF-16 to String
Ok(widestring::decode_utf16_lossy(wide.iter().copied()).collect::<String>())
}
TdhInType::InTypeAnsiString => {
Expand Down