s4: Patch for fixing LDB integer save operations on 64 bit platforms

Andrew Bartlett abartlet at samba.org
Fri Oct 15 15:18:17 MDT 2010

On Fri, 2010-10-15 at 21:08 +0200, Matthias Dieter Wallnöfer wrote:
> Okay, this is the latest patch proposal: 
> http://gitweb.samba.org/samba.git/?p=mdw/samba.git;a=commitdiff;h=26121b2ea1c7c6fce0589b1db89e385ea1367dd9

The comment here is still quite incorrect.  There is nothing special
about numbers > 2^16.  The issue is also not to do with nibble orders or
big endian platforms.  As I see it, the issue is the behaviour of
casting to 'unsigned' or 'signed' on platforms where a 'long' is 64 bits

As I see it, your patch is correct, but we just need more comments -
such as something like this on samldb_msg_add_uint() (because the
current use is deceptive to the casual observer):


The issue here is that we have not yet first cast to int32_t explicitly,
before we cast to an signed int to printf() into the %d or cast to a
int64_t before we then cast to a long long to printf into a %lld.

There are *no* unsigned integers in Active Directory LDAP, even the RID
allocations and ms-DS-Secondary-KrbTgt-Number are *signed* quantities.
(See the schema, and the syntax definitions in schema_syntax.c). 


I think we should always cast to int32_t (but then again, if we are on a
platform where 'int' isn't 32 bits, we are probably totally broken
anyway, but it may still be safer). 

However, I do wonder if we are dealing with this at the wrong layer -
you should first test if AD allows these large, signed numbers to be set
over LDAP, and then what value is stored in the DB.  If the DB
'magically' wraps these to signed 32 bit numbers, then passing in large
unsigned numbers is harmless, and we may simply need to work on our
schema validation code instead. 

Finally, I do want to thank you for looking into this - issues of
integer length can be tricky to debug, particularly when we have relied
on implicit casts in printf().  

We should also remember that on databases other than sam.ldb, different
rules may apply - they are not under such silly restrictions regarding
unsigned integers.

Andrew Bartlett
Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org
Samba Developer, Cisco Inc.

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