Re: [PATCH v5] man/man7/pathname.7: Add file documenting format of pathnames

[Florian Weimer <fweimer@redhat.com>]

* Alejandro Colomar:

> Hi Jason, Florian,
>
> On Sun, Jan 19, 2025 at 08:17:46AM -0500, Jason Yundt wrote:
>> > It seems you're passing a non-terminated string, and thus it's producing
>> > a non-terminated string.  Why don't you pass a null-terminated string?
>> > 
>> > That is, inbytesleft should include be the length + 1.
>> 
>> Here’re my concern: iconv(3) is going to see the final element of
>> utf32_pathname and interpret it as a U+0000 null character.  In some
>> character encodings, U+0000 null is encoded as a single null byte.  In
>> other character encodings, U+0000 null is encoded as something other
>> than a single null byte.  For example, in Modified UTF-8, U+0000 null is
>> encoded as the bytes C0 80.  Is there any guarantee that
>> nl_langinfo(CODESET) will return a character encoding where U+0000 is
>> represented as a single null byte?

> Florian, do you know this?

Character sets used by glibc locales must be mostly ASCII-transparent.
This includes the mapping of the null byte.  It is possible to create
locales that do not follow these rules, but they tend to introduce
security vulnerabilities, particularly if shell metacharacters are
mapped differently.

Thanks,
Florian