bugmonotone - Bugs: bug #27929, Don't use excessive amounts of...

 
 

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bug #27929: Don't use excessive amounts of entropy

Submitted by:  Martin von Gagern <gagern>
Submitted on:  Tue 03 Nov 2009 08:28:43 PM UTC  
 
Category: cryptographySeverity: 3 - Normal
Item Group: feature requestStatus: Wont Fix
Privacy: PublicAssigned to: None
Open/Closed: Closed
mtn version --full: 

monotone 0.43

Thu 12 Nov 2009 01:55:58 PM UTC, comment #1:

[log.html Starting from version 1.8.3 (2009-07-11)] botan is using /dev/urandom instead of /dev/random, so the solution to avoid using /dev/random seems simply to be: upgrade your botan package to 1.8.3+.

Lapo Luchini <lapo>
Tue 03 Nov 2009 08:28:43 PM UTC, original submission:

In http://bugs.gentoo.org/274709 I found out that session::mk_nonce uses a random number generator (RNG) from botan to generate some kind of nonce. It seems to use some kind of default random number generator there, which in turn uses a number of entropy sources, /dev/random prominent among them.

This uses up entropy, a valuable resource. Running multiple processes which behave in this way could cause the entropy pool to become depleted, causing processes to block reading from /dev/random. While it makes sense to use this strong entropy source for highly sensitive cryptographic tasks executed not too often, using it for nonce generation seems a bad idea to me, in particular if this is a read-only access to a public repository, so there is nothing there to protect imho.

I would therefore suggest that you use different kinds of entropy soutrces for different tasks. Nonce generation should use /dev/urandom, and maybe other parts of monotone as well.
Quoting from http://www.kernel.org/doc/man-pages/online/pages/man4/random.4.html
"If you are unsure about whether you should use /dev/random or /dev/urandom, then probably you want to use the latter. As a general rule, /dev/urandom should be used for everything except long-lived GPG/SSL/SSH keys."

I've originally investigated a bug in monotone 0.43 when I observed this issue. I don't have that version installed any more, so I can't give you the "mtn version --full" output. I don't see any changes affecting this issue since then, so I assume it's present in current releases as well.

Martin von Gagern <gagern>

 

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  • -unavailable- added by dscherger (Updated the item)
  • -unavailable- added by lapo (Posted a comment)
  • -unavailable- added by gagern (Submitted the item)
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    Follow 2 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sat 08 May 2010 09:31:28 PM UTCdschergerStatusNone=>Wont Fix
      Open/ClosedOpen=>Closed

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