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Decode unaligned registry UTF-16 data safely #9599

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Merged
youknowone merged 3 commits into from
Nov 5, 2026
Merged

Decode unaligned registry UTF-16 data safely #9599

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c3afc23
Decode unaligned registry UTF-16 data safely
youknowdot Nov 3, 2026
405f948
Use array chunks for registry UTF-16 decoding
youknowdot Nov 3, 2026
9e6d797
Merge current main into registry alignment fix
youknowdot Nov 4, 2026
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24 changes: 22 additions & 2 deletions crates/host_env/src/winreg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@

extern crate alloc;

use alloc::string::FromUtf16Error;
use alloc::{borrow::Cow, string::FromUtf16Error};
use rustpython_wtf8::Wtf8Buf;

use windows_sys::Win32::{
Expand Down Expand Up @@ -97,6 +97,26 @@ pub fn bytes_as_wide_slice(bytes: &[u8]) -> &[u16] {
u16_slice
}

pub fn registry_wide_units(bytes: &[u8]) -> Cow<'_, [u16]> {
// Windows strings use complete native-endian UTF-16 code units; CPython
// ignores a trailing incomplete byte.
let bytes = &bytes[..bytes.len() & !1];
// SAFETY: Every u16 bit pattern is valid and align_to checks alignment.
let (prefix, u16_slice, _) = unsafe { bytes.align_to::<u16>() };
if prefix.is_empty() {
Cow::Borrowed(u16_slice)
} else {
Cow::Owned(
bytes
.as_chunks::<2>()
.0
.iter()
.map(|&pair| u16::from_ne_bytes(pair))
.collect(),
)
}
}

pub fn close_key(hkey: Registry::HKEY) -> u32 {
unsafe { Registry::RegCloseKey(hkey) }
}
Expand Down Expand Up @@ -423,7 +443,7 @@ fn query_default_value_with<T>(
break Err(QueryStringError::Code(Foundation::ERROR_INVALID_DATA));
}

let u16_slice = bytes_as_wide_slice(&buffer[..size as usize]);
let u16_slice = registry_wide_units(&buffer[..size as usize]);
let len = u16_slice
.iter()
.position(|&c| c == 0)
Expand Down
4 changes: 2 additions & 2 deletions crates/vm/src/stdlib/winreg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -758,7 +758,7 @@ mod winreg {
Ok(vm.ctx.new_int(val).into())
}
REG_SZ | REG_EXPAND_SZ => {
let u16_slice = host_winreg::bytes_as_wide_slice(ret_data);
let u16_slice = host_winreg::registry_wide_units(ret_data);
// Only use characters up to the first NUL.
let len = u16_slice
.iter()
Expand All @@ -772,7 +772,7 @@ mod winreg {
if ret_data.is_empty() {
Ok(vm.ctx.new_list(vec![]).into())
} else {
let u16_slice = host_winreg::bytes_as_wide_slice(ret_data);
let u16_slice = host_winreg::registry_wide_units(ret_data);
let u16_count = u16_slice.len();

// Remove trailing null if present (like countStrings)
Expand Down
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