[PATCH] (4/7) trust_pct

• Next message: Oliver Xymoron: "[PATCH] (5/7) untrusted entropy sources"
• Previous message: Oliver Xymoron: "[PATCH] (3/7) xfer cleanup"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

This allows adding a bit of entropy for a configurable percentage of
untrusted timer samples, controlled by a new sysctl. This defaults to
0 for safety, but can be used on headless machines without a hardware
RNG to continue to use /dev/random with some confidence.

RML's patch to turn on SA_SAMPLE_RANDOM for most NICs is safe after
this patch.

diff -ur a/drivers/char/random.c b/drivers/char/random.c
--- a/drivers/char/random.c 2002-08-23 12:43:24.000000000 -0500
+++ b/drivers/char/random.c 2002-08-23 12:43:27.000000000 -0500
@@ -694,6 +694,7 @@
 static struct timer_rand_state extract_timer_state;
 static struct timer_rand_state *irq_timer_state[NR_IRQS];
 static struct timer_rand_state *blkdev_timer_state[MAX_BLKDEV];
+static int trust_break=50, trust_pct=0, trust_min=0, trust_max=100;
 
 /*
  * This function adds entropy to the entropy "pool" by using timing
@@ -761,6 +762,17 @@
 
                 entropy = int_log2_16bits(delta);
         }
+ else if(trust_pct)
+ {
+ /* Count an untrusted bit as entropy trust_pct% of the time */
+ trust_break+=trust_pct;
+ if(trust_break >= 100)
+ {
+ entropy=1;
+ trust_break-=100;
+ }
+ }
+
         batch_entropy_store(num^time, entropy);
 }
 
@@ -1849,6 +1861,10 @@
         {RANDOM_UUID, "uuid",
          NULL, 16, 0444, NULL,
          &proc_do_uuid, &uuid_strategy},
+ {RANDOM_TRUST_PCT, "trust_pct",
+ &trust_pct, sizeof(int), 0644, NULL,
+ &proc_dointvec_minmax, &sysctl_intvec, 0,
+ &trust_min, &trust_max},
         {0}
 };
 
diff -ur a/include/linux/sysctl.h b/include/linux/sysctl.h
--- a/include/linux/sysctl.h 2002-08-17 00:30:00.000000000 -0500
+++ b/include/linux/sysctl.h 2002-08-23 12:43:27.000000000 -0500
@@ -182,7 +182,8 @@
         RANDOM_READ_THRESH=3,
         RANDOM_WRITE_THRESH=4,
         RANDOM_BOOT_ID=5,
- RANDOM_UUID=6
+ RANDOM_UUID=6,
+ RANDOM_TRUST_PCT=7
 };
 
 /* /proc/sys/bus/isa */

-- 
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.." 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

• Next message: Oliver Xymoron: "[PATCH] (5/7) untrusted entropy sources"
• Previous message: Oliver Xymoron: "[PATCH] (3/7) xfer cleanup"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

This archive was generated by hypermail 2b29 : Fri Aug 23 2002 - 22:00:28 EST