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Re: [PATCH] * grub-core/fs/udf.c: Add support for UUID

From: Pali Rohár
Subject: Re: [PATCH] * grub-core/fs/udf.c: Add support for UUID
Date: Thu, 11 May 2017 12:59:20 +0200
User-agent: Mutt/ (2014-03-12)

On Monday 08 May 2017 16:24:24 Pali Rohár wrote:
> On Monday 08 May 2017 15:13:28 Vladimir 'phcoder' Serbinenko wrote:
> > On Mon, Apr 10, 2017, 23:17 Pali Rohár <address@hidden> wrote:
> > > char *outbuf, int normalize_utf8)
> > 
> > Normalize isn't the right word. And it's not utf-8 but latin1 (called
> > compressed utf-16 by udf docs).
> Without this patch part read_string() expects that input string is 
> either utf-8 or utf-16 in that compressed osta form. If input string is 
> marked with leading 0x8 but contains invalid UTF-8 sequence (like chars 
> 80-FF) then it is treated as Latin1 and converted to UTF-8 in output. So 
> input "\x80" is returned as "\xC2\x80".
> What I need is to do not do this Latin1 --> UTF-8 conversion if input is 
> marked with leading 0x8 and stay it in binary/raw/octets form. This is 
> due to older versions of mkudffs which put into volset string not 
> conforming to osta spec. libblkid do not do that "\x80" --> "\xC2\x80" 
> conversion too so it is better to have same algorithm for providing UUID 
> on running system (blkid on Linux) and in bootloader (Grub2).
> > Are you sure you handle utf-16 case correctly? What is the expected
> > behavior in those cases? Ideally you may want to just parse raw
> > string in caller
> If volsetid is stored according to osta spec, then it is handed 
> correctly (both UTF-8 and UTF-16).
> > > +  binpos = 16;
> > > +  for (i = 0; i < len; ++i)
> > > +    {
> > > +      if (!grub_isalnum (buf[i]))
> > 
> > That looks real weird. What if first byte of UUID is 'a'? What if
> > alnum part contains non-English chars.

Hm... check rather should be that buf[i] contains hexadecimal digit, not
arbitrary letter. But in most cases it is hexadecimal digit...

> > I have to admit I don't get what expected behaviour is. Can you
> > elaborate on this and enable UUID test in udf_test to check that
> > UUID matches blkid?
> According to osta spec, first 16 characters of volsetid are unique and 
> remaining anything. First 8 characters are hexadecimal representation of 
> 32bit timestamp and remaining 8 implementation free (but still are 
> unique). Therefore those first 16 characters we use for generating UUID.
> Again some generators of UDF disks do not put there hexadecimal number, 
> but some garbage (sometimes not valid UTF-8...) so this code generates 
> alphanumeric UUID from input with fact that in most cases is input 
> hexadecimal (so used as is).
> If you have other idea how to deal with this, let me know...

Pali Rohár

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