[PATCH] improve checks on usernames V3.

[Tito]

On Tuesday 02 August 2011 22:16:18 Ralf Friedl wrote:
> Tito wrote:
> > Hi,
> > minor improvements vs. v2 patch:
> > 1) some more comments added.
> > 2) we now print the position of the illegal character.
> >
> > ...
> > 		/* We don't use isalnum  as it will allow locale-specific non-ASCII */
> > 		/* letters in legacy 8-bit locales. *
> What is the problem with locale-specific characters?

Just that they are not portable so that e.g. "If using external authentication sources to verify user credentials, 
you must establish whether these authentication sources also support multi-byte characters. 
If multi-byte characters are not supported, you must specify usernames and passwords using ASCII characters"
(portable filename charset is recommended).

> I have used user and group names with UTF-8 characters and I didn't 
> notice a problem so far.

This is of course possible and this feature is optional and 
could be turned off if not needed, OTOH allowing chars
as . - $ : /  in usernames may be problematic.

> GNU ls even adjusts the width of the user and group names properly for 
> UTF-8 names, which would be useless if such names can't be created. 
> (Side note, Busybox ls does not adjust the width and truncates at 8 bytes).
> 
> Ralf
> 

Ciao,
Tito