Skip to content

fix(unicode): prevent USHORT overflow and null-terminator buffer over… #8

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
TorinKS merged 1 commit into from
Mar 22, 2026
Merged

fix(unicode): prevent USHORT overflow and null-terminator buffer over… #8

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 12 additions & 8 deletions include/UnicodeString.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -267,7 +267,12 @@ inline NTSTATUS RtlInitUnicodeString(
return STATUS_NAME_TOO_LONG;
}
DestinationString->Length = (USHORT)Length;
DestinationString->MaximumLength = (USHORT)(Length + sizeof(UNICODE_NULL));
/* Cap MaximumLength to avoid USHORT overflow when Length == UNICODE_STRING_MAX_BYTES */
if (Length + sizeof(UNICODE_NULL) > UNICODE_STRING_MAX_BYTES) {
DestinationString->MaximumLength = (USHORT)Length;
} else {
DestinationString->MaximumLength = (USHORT)(Length + sizeof(UNICODE_NULL));
}
} else {
DestinationString->Length = 0;
DestinationString->MaximumLength = 0;
Expand Down Expand Up @@ -454,11 +459,11 @@ RtlAppendUnicodeToString(
// Update destination length
Destination->Length += sourceLength;

// Null terminate if there's room
if (Destination->Length < Destination->MaximumLength) {
// Null terminate if there's room for a full WCHAR
if (Destination->Length + sizeof(WCHAR) <= Destination->MaximumLength) {
Destination->Buffer[Destination->Length / sizeof(WCHAR)] = UNICODE_NULL;
}
return STATUS_SUCCESS;
return STATUS_SUCCESS;
}

// Implementation of RtlAppendUnicodeStringToString
Expand Down Expand Up @@ -516,12 +521,11 @@ RtlAppendUnicodeStringToString(
// Update destination length
Destination->Length += Source->Length;

// Add null terminator if there's space (note: this is not required by the API contract
// but is a courtesy for debugging and compatibility with C-style strings)
if (Destination->Length < Destination->MaximumLength) {
// Add null terminator if there's space for a full WCHAR
if (Destination->Length + sizeof(WCHAR) <= Destination->MaximumLength) {
Destination->Buffer[Destination->Length / sizeof(WCHAR)] = UNICODE_NULL;
}
return STATUS_SUCCESS;
return STATUS_SUCCESS;
}

/**
Expand Down
Loading