Messages in this thread Patch in this message |  | | Date | Fri, 23 Aug 2002 13:31:28 -0500 | From | Oliver Xymoron <> | Subject | [PATCH] (4/7) trust_pct |
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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 */
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