- (djm) Random number collection doc fixes from Ben

This commit is contained in:
Damien Miller 2002-04-14 23:16:04 +10:00
parent 32e4818015
commit 49411ff8a7
3 changed files with 27 additions and 17 deletions

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@ -3,6 +3,7 @@
- Add commandline debugging options
- Don't write binary data if stdout is a tty (use hex instead)
- Give it a manpage
- (djm) Random number collection doc fixes from Ben
20020413
- (djm) Add KrbV support patch from Simon Wilkinson <simon@sxw.org.uk>
@ -8240,4 +8241,4 @@
- Wrote replacements for strlcpy and mkdtemp
- Released 1.0pre1
$Id: ChangeLog,v 1.2052 2002/04/14 09:27:12 djm Exp $
$Id: ChangeLog,v 1.2053 2002/04/14 13:16:04 djm Exp $

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@ -108,10 +108,6 @@ different name.
need a working installation of GNOME, including the development
headers, for this to work.
--with-random=/some/file allows you to specify an alternate source of
random numbers (the default is /dev/urandom). Unless you are absolutely
sure of what you are doing, it is best to leave this alone.
--with-prngd-socket=/some/file allows you to enable EGD or PRNGD
support and to specify a PRNGd socket. Use this if your Unix lacks
/dev/random and you don't want to use OpenSSH's builtin entropy
@ -222,4 +218,4 @@ Please refer to the "reporting bugs" section of the webpage at
http://www.openssh.com/
$Id: INSTALL,v 1.50 2002/04/05 16:11:46 mouring Exp $
$Id: INSTALL,v 1.51 2002/04/14 13:16:05 djm Exp $

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@ -28,8 +28,12 @@ On to the description...
The portable OpenSSH contains random number collection support for
systems which lack a kernel entropy pool (/dev/random).
This collector operates by executing the programs listed in
($etcdir)/ssh_prng_cmds, reading their output and adding it to the
This collector (as of 3.1 and beyond) comes as an external application
that allows the local admin to decide on how to implement entropy
collection.
The default entropy collector operates by executing the programs listed
in ($etcdir)/ssh_prng_cmds, reading their output and adding it to the
PRNG supplied by OpenSSL (which is hash-based). It also stirs in the
output of several system calls and timings from the execution of the
programs that it runs.
@ -43,7 +47,7 @@ The random number code will also read and save a seed file to
number generator at startup. The goal here is to maintain as much
randomness between sessions as possible.
The entropy collection code has two main problems:
The default entropy collection code has two main problems:
1. It is slow.
@ -51,14 +55,13 @@ Executing each program in the list can take a large amount of time,
especially on slower machines. Additionally some program can take a
disproportionate time to execute.
This can be tuned by the administrator. To debug the entropy
collection is great detail, turn on full debugging ("ssh -v -v -v" or
"sshd -d -d -d"). This will list each program as it is executed, how
long it took to execute, its exit status and whether and how much data
it generated. You can the find the culprit programs which are causing
the real slow-downs.
Tuning the default entropy collection code is difficult at this point.
It requires doing 'times ./ssh-rand-helper' and modifying the
($etcdir)/ssh_prng_cmds until you have found the issue. In the next
release we will be looking at support '-v' for verbose output to allow
easier debugging.
The entropy collector will timeout programs which take too long
The default entropy collector will timeout programs which take too long
to execute, the actual timeout used can be adjusted with the
--with-entropy-timeout configure option. OpenSSH will not try to
re-execute programs which have not been found, have had a non-zero
@ -79,5 +82,15 @@ up and various other factors.
To make matters even more complex, some of the commands are reporting
largely the same data as other commands (eg. the various "ps" calls).
$Id: WARNING.RNG,v 1.4 2001/02/09 01:55:36 djm Exp $
How to avoid the default entropy code?
The best way is to read the OpenSSL documentation and recompile OpenSSL
to use prngd or egd. Some platforms (like earily solaris) have 3rd
party /dev/random devices that can be also used for this task.
If you are forced to use ssh-rand-helper consider still downloading
prngd/egd and configure OpenSSH using --with-prngd-port=xx or
--with-prngd-socket=xx (refer to INSTALL for more information).
$Id: WARNING.RNG,v 1.5 2002/04/14 13:16:05 djm Exp $