jvybihal
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GUID: how is it created?

Hello, today, when I was debugging some IdM issues, I noticed that some guids of of users in connected eDirectory systemc are looking quite interesting to me.

Some examples:

000BEEF84EF7D911B66EFFFFFFFFFFFF
000CB04C026EDF11B66FFFFFFFFFFFFF
000DD07A9AA8E011B66FFFFFFFFFFFFF
003FF47871FBDA11B66EFFFFFFFFFFFF
004053D4200FDF11B66FFFFFFFFFFFFF
0041925D0093DA11B41CFFFFFFFFFFFF


8D46DD53D77C5842FB918D46DD53D77C
8FC40D52AF87644EF6A88FC40D52AF87
9148C33457CFB04536839148C33457CF



I wonder, how exactly are guids created under the hood? Does those FFFFFFFFFFFFFs mean something special? Or is that just a padding to 32 bytes when migrated (probably, I dont know for sure) from older (netware?) system? Why the last 12 bytes repeat sometimes? But some users have guids fairly "ok-guid-looking-like" 809663B72F43D7118D4E00B0D0FE7592.
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Knowledge Partner Knowledge Partner
Knowledge Partner

Re: GUID: how is it created?

There are multiple ways for systems to generate UUID/GUID types of things,
and while we like to think of them as being completely random, in reality
they are often note, and need not be, so long as they are unique. These
are not hashes, but are just meant to be unique, so some implementations
look more like insanely-complex hexadecimal counters (when printed for
human readability) while others appear to change entirely with every one
generated, depending on how many you view and how closely they were
generated. There is a decent Wikipedia page on generation of GUID/UUID
data which you may find interesting.

At the end of the day, the important thing with any GUID/UUID is that it
really is globally/universally unique, and all implementations do a decent
job of ensuring that within their scope of use. If there is a particular
reason for knowing the algorithm behind the implementation, please sure
that business case, but chances are good that we will only be speculating
as the product is not open source, and reverse-engineering it will likely
only be interesting academically, vs. practical in any other way (since
the GUIDs are unique regardless of how well we understand the exact
implementation details).

--
Good luck.

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Knowledge Partner
Knowledge Partner

Re: GUID: how is it created?

I had a situation when GUID for objects created a long time ago on "old" eDirectory hosted on "old" Solaris systems generated GUID "duplications" or objects with "very close" GUID values (differences only in one bit).
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Knowledge Partner Knowledge Partner
Knowledge Partner

Re: GUID: how is it created?

I recall about the time I started at Novell (2004) I heard about "old" (at
the time) bugs where the GUID generators, which were fairly new, had
issues so duplicate could be generated, but it's been a ton of years since
I've seen that. I wrote a script to detect those duplicates even back in
the day: https://www.novell.com/coolsolutions/feature/16494.html


--
Good luck.

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Knowledge Partner
Knowledge Partner

Re: GUID: how is it created?

ab;2474956 wrote:
I recall about the time I started at Novell (2004) I heard about "old" (at
the time) bugs where the GUID generators, which were fairly new, had
issues so duplicate could be generated, but it's been a ton of years since
I've seen that. I wrote a script to detect those duplicates even back in
the day: https://www.novell.com/coolsolutions/feature/16494.html


--
Good luck.

If you find this post helpful and are logged into the web interface,
show your appreciation and click on the star below.

If you want to send me a private message, please let me know in the
forum as I do not use the web interface often.


Most of these duplications in the objects created during our initial mass user creation in 2001.
Thank you for your script, Aaron!
I use IDM null driver for detect and report about duplications. 🙂
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