Can the qof guid library be replaced by libuuid on linux? Phil --------- I used to be a hypochondriac AND a kleptomaniac. So I took something for it.
________________________________ From: Phil Longstaff <plongst...@rogers.com> To: Geert Janssens <janssens-ge...@telenet.be> Cc: Gnucash Devel <gnucash-de...@lists.gnucash.org> Sent: Mon, March 7, 2011 2:34:15 PM Subject: Re: WARN <qof.engine> [guid_init()] only got xxxx bytes. The identifiers might not be very random. It seems to me that a guid is a guid. Can you just use the win32 function UuidCreate()? Phil --------- I used to be a hypochondriac AND a kleptomaniac. So I took something for it. ________________________________ From: Geert Janssens <janssens-ge...@telenet.be> To: gnucash-devel@gnucash.org Sent: Mon, March 7, 2011 2:23:27 PM Subject: WARN <qof.engine> [guid_init()] only got xxxx bytes. The identifiers might not be very random. ... A warning that will appear in every trace file on Windows. We have all learned to ignore it. Unfortunately, it was a sign of a deeper underlying problem I'd like to discuss here a bit more. We all know GnuCash uses GUID's to uniquely identify its internal objects. These GUID's are generated based on some random number generator [1]. To generate good random GUID's this generator is seeded with some randomness from many different sources [2]. So far so good. These sources are amongst others * /dev/urandom (the system's non-blocking random number generator on unix like architectures), * a number of files that are generally known to have data that differs from machine to machine and evolves randomly in time (/etc/password, several files under /proc/ and so on * a number of directories from which the contents are hardly predictable (again /proc and several of its descendants, /tmp)... * several others, not really relevant for this mail. The problem with the mentioned sources so far is that they all exist on most unix-like systems (linux, OS X, *BSD), but not on Windows. The result is that on Windows the init function doesn't generate a sufficient amount of random numbers to seed the generator. Hence the warning. I would never have come up with the idea to look into this if I wasn't lead to this very intialization function while tracking a bug on Windows [3]. And for those interested: the guid_init function causes *internet* traffic on a Windows box. Probably no successful connections though, but it does in some way trigger the system to hit the network. All because the guid_init function assumes to be in a unix-like environment. The bug is worked around now (I hope), but the core issue still remains: the guid_init function is not well adapted for Windows. The solution: add some code that does similar things but with Windows friendly alternatives. /dev/urandom can be replaced on Windows with RtlGenRandom for example, and I'm sure we can come up with a number of files and directories that can be considered unpredictable on Windows. And right about then, I paused. Looking at all these randomness attempts I'm wondering if this is really all necessary. The routine is built to generate cryptographically safe random numbers. But we're not into cryptography here are we ? As far as I know we don't really care if the generation process is predictable, as long as it continue to generate unique numbers. As far as I know, we only care to get numbers that are unique. Can't we achieve this with less complicated methods ? I imagine that a combination of /dev/urandom (or RtlGenRandom), some date-time information and some other universally available things like process ID, last generated GUID should together be sufficiently random ? Perhaps I'm opening a can of worms here, I don't know. I'm not really a random generator expert. If that's not sufficient, can someone suggest me some files and directories that can be used on Windows to seed the random generator ? Geert [1] http://svn.gnucash.org/trac/browser/gnucash/trunk/src/libqof/qof/guid.c [2] http://svn.gnucash.org/trac/browser/gnucash/trunk/src/libqof/qof/guid.c#L361 [3] https://bugzilla.gnome.org/show_bug.cgi?id=521817 _______________________________________________ gnucash-devel mailing list gnucash-devel@gnucash.org https://lists.gnucash.org/mailman/listinfo/gnucash-devel _______________________________________________ gnucash-devel mailing list gnucash-devel@gnucash.org https://lists.gnucash.org/mailman/listinfo/gnucash-devel _______________________________________________ gnucash-devel mailing list gnucash-devel@gnucash.org https://lists.gnucash.org/mailman/listinfo/gnucash-devel
