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diff --git a/pipermail/pycrypto/2008q3/000000.html b/pipermail/pycrypto/2008q3/000000.html new file mode 100644 index 0000000..89ef64f --- /dev/null +++ b/pipermail/pycrypto/2008q3/000000.html @@ -0,0 +1,103 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<HTML> + <HEAD> + <TITLE> [pycrypto] What to do about RandomPool + </TITLE> + <LINK REL="Index" HREF="index.html" > + <LINK REL="made" HREF="mailto:pycrypto%40lists.dlitz.net?Subject=%5Bpycrypto%5D%20What%20to%20do%20about%20RandomPool&In-Reply-To="> + <META NAME="robots" CONTENT="index,nofollow"> + <META http-equiv="Content-Type" content="text/html; charset=us-ascii"> + + <LINK REL="Next" HREF="000001.html"> + </HEAD> + <BODY BGCOLOR="#ffffff"> + <H1>[pycrypto] What to do about RandomPool</H1> + <B>Dwayne C. Litzenberger</B> + <A HREF="mailto:pycrypto%40lists.dlitz.net?Subject=%5Bpycrypto%5D%20What%20to%20do%20about%20RandomPool&In-Reply-To=" + TITLE="[pycrypto] What to do about RandomPool">dlitz at dlitz.net + </A><BR> + <I>Mon Jul 21 18:25:26 CST 2008</I> + <P><UL> + + <LI>Next message: <A HREF="000001.html">[pycrypto] What to do about RandomPool +</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#0">[ date ]</a> + <a href="thread.html#0">[ thread ]</a> + <a href="subject.html#0">[ subject ]</a> + <a href="author.html#0">[ author ]</a> + </LI> + </UL> + <HR> +<!--beginarticle--> +<PRE>[Reposted from <A HREF="https://bugs.launchpad.net/pycrypto/+bug/249765]">https://bugs.launchpad.net/pycrypto/+bug/249765]</A> + +RandomPool really really needs to die, at least in its current form. It's +not thread-safe, it's not fork-safe, and if it can't get entropy from the +OS, it silently produces predictable output. What's worse is that everyone +assumes that it's a portable substitute for reading from /dev/urandom on +Linux, but it's actually way too fragile to be safely used that way. + +When I fixed Paramiko's usage of RandomPool back in January, Robey Pointer +broke it again, so I ended up fixing it *twice* in one program.[1] Judging +from the rest of the Paramiko code base, I certainly do NOT think Robey is +a careless or stupid programmer; Random number generators are just hard to +get right and RandomPool encourages people to get it wrong. I have yet to +see any code that *explicitly* uses RandomPool correctly. Most of the code +I've seen that avoids RandomPool-related security holes seems to do so +accidentally---as long as it's not running on Windows and /dev/urandom +exists. + +I'm not sure that PyCrypto is the right place to implement a good RNG, +anyway. Even if we make RandomPool thread-safe and make sure it initializes +with enough entropy, it all becomes pointless as soon as somebody calls +os.fork(), which duplicates the entire state pool. As far as I know, +there's no easy way (and certainly no portable way) to prevent that. Also, +absent an OS random number generator, arbitrary programs usually have +little to no access to entropy. What makes matters worse is that, unless +the RNG gets to run in its own process/thread (RandomPool does not) it +relies totally on the user to supply the pool with new entropy at frequent +intervals. That almost never happens. + +Would there be any objection to replacing RandomPool with a simple wrapper +around os.urandom? A quick benchmark shows that reading from /dev/urandom +on Linux is about 10-50x faster than using RandomPool. + +[1] See + <A HREF="http://www.lag.net/pipermail/paramiko/2008-January/000599.html">http://www.lag.net/pipermail/paramiko/2008-January/000599.html</A> + and + <A HREF="http://www.lag.net/pipermail/paramiko/2008-April/000678.html">http://www.lag.net/pipermail/paramiko/2008-April/000678.html</A> + +-- +Dwayne C. Litzenberger <<A HREF="http://lists.dlitz.net/cgi-bin/mailman/listinfo/pycrypto">dlitz at dlitz.net</A>> + Key-signing key - 19E1 1FE8 B3CF F273 ED17 4A24 928C EC13 39C2 5CF7 + Annual key (2008) - 4B2A FD82 FC7D 9E38 38D9 179F 1C11 B877 E780 4B45 +-------------- next part -------------- +A non-text attachment was scrubbed... +Name: not available +Type: application/pgp-signature +Size: 197 bytes +Desc: Digital signature +Url : <A HREF="http://lists.dlitz.net/pipermail/pycrypto/attachments/20080721/deb9ebb1/attachment.pgp">http://lists.dlitz.net/pipermail/pycrypto/attachments/20080721/deb9ebb1/attachment.pgp</A> +</PRE> + + +<!--endarticle--> + <HR> + <P><UL> + <!--threads--> + + <LI>Next message: <A HREF="000001.html">[pycrypto] What to do about RandomPool +</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#0">[ date ]</a> + <a href="thread.html#0">[ thread ]</a> + <a href="subject.html#0">[ subject ]</a> + <a href="author.html#0">[ author ]</a> + </LI> + </UL> + +<hr> +<a href="http://lists.dlitz.net/cgi-bin/mailman/listinfo/pycrypto">More information about the pycrypto +mailing list</a><br> +</body></html> |