summaryrefslogtreecommitdiff
path: root/WARNING.RNG
diff options
context:
space:
mode:
authordjm <djm>2002-04-14 13:16:04 +0000
committerdjm <djm>2002-04-14 13:16:04 +0000
commitd8dcf0e07de6588c137e40c2034e847161c55bda (patch)
tree7c13f02be07d9cbd6e59c006f7cd2e693f454240 /WARNING.RNG
parent5a7dea43690f694e9c767e97d185ae1090fe5aa8 (diff)
downloadopenssh-d8dcf0e07de6588c137e40c2034e847161c55bda.tar.gz
- (djm) Random number collection doc fixes from Ben
Diffstat (limited to 'WARNING.RNG')
-rw-r--r--WARNING.RNG35
1 files changed, 24 insertions, 11 deletions
diff --git a/WARNING.RNG b/WARNING.RNG
index 487346ef..ae43930a 100644
--- a/WARNING.RNG
+++ b/WARNING.RNG
@@ -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 $