Hi!
----
Attached is a small (unfinished) prototype toy patch
("ksh93_random_use_dev_urandom001.diff.txt") which switches the
discipline functions of ${RANDOM} from |rand()| to /dev/urandom,
resulting in a much better random number generation (/dev/random wasn't
used because it may block when the system's entropy is used-up and wait
until enougth entropy becomes available).
Questions:
- Can I register a C function which gets called at shell shutdown which
can be used to close any file descriptors ?
- Would it be usefull/Ok to add ${RANDOM.min} and ${RANDOM.max} to
define the upper and lower bounds for a random value ?
- How should I handle writing to ${RANDOM} (which normally defines the
seed of |rand()|) when /dev/urandom is used ? The device is read-only on
Solaris for normal users. Should a write failure (to /dev/urandom) be
ignored or handled as error ?
----
Bye,
Roland
--
__ . . __
(o.\ \/ /.o) roland.mainz at nrubsig.org
\__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer
/O /==\ O\ TEL +49 641 7950090
(;O/ \/ \O;)
-------------- next part --------------
Index: src/lib/libshell/common/sh/init.c
===================================================================
--- src/lib/libshell/common/sh/init.c (revision 534)
+++ src/lib/libshell/common/sh/init.c (working copy)
@@ -552,6 +552,27 @@
np->nvalue.lp = &rp->rand_last;
}
+
+static
+int fetch_dev_random(void)
+{
+ static int randdevfildes = -1; /* bug:we should close this file... */
+ int randval = 0;
+
+ if (randdevfildes == -1)
+ {
+ randdevfildes = open("/dev/urandom", O_RDONLY);
+ }
+
+ if (randdevfildes != -1)
+ {
+ if (read(randdevfildes, &randval, sizeof(randval)) == sizeof(randval))
+ return randval;
+ }
+
+ return rand();
+}
+
/*
* get random number in range of 0 - 2**15
* never pick same number twice in a row
@@ -561,7 +582,7 @@
register long cur, last= *np->nvalue.lp;
NOT_USED(fp);
do
- cur = (rand()>>rand_shift)&RANDMASK;
+ cur = (fetch_dev_random()>>rand_shift)&RANDMASK;
while(cur==last);
*np->nvalue.lp = cur;
return((Sfdouble_t)cur);
