This makes irq and blkdev interrupts untrusted and allows adding a bit
of entropy for a configurable percentage of untrusted 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.
This also smartens up and simplifies the batch entropy pool to allow
unlimited amounts of untrusted mixing without blocking out trusted
samples.
diff -urN -x '.patch*' -x '*.orig' orig/drivers/char/random.c work/drivers/char/random.c
--- orig/drivers/char/random.c 2002-09-28 00:16:14.000000000 -0500
+++ work/drivers/char/random.c 2002-09-28 00:16:14.000000000 -0500
@@ -544,7 +544,7 @@
}
/*
- * This function adds a byte into the entropy "pool". It does not
+ * This function adds a word into the entropy "pool". It does not
* update the entropy estimate. The caller should call
* credit_entropy_store if this is appropriate.
*
@@ -618,25 +618,19 @@
*
**********************************************************************/
-static __u32 *batch_entropy_pool;
-static int *batch_entropy_credit;
-static int batch_max;
-static int batch_head, batch_tail;
+static __u32 *batch_entropy_pool=0;
+static int batch_max, batch_pos, batch_credit, batch_samples;
static struct tq_struct batch_tqueue;
static void batch_entropy_process(void *private_);
/* note: the size must be a power of 2 */
static int __init batch_entropy_init(int size, struct entropy_store *r)
{
- batch_entropy_pool = kmalloc(2*size*sizeof(__u32), GFP_KERNEL);
+ batch_entropy_pool = kmalloc(size*sizeof(__u32), GFP_KERNEL);
if (!batch_entropy_pool)
return -1;
- batch_entropy_credit =kmalloc(size*sizeof(int), GFP_KERNEL);
- if (!batch_entropy_credit) {
- kfree(batch_entropy_pool);
- return -1;
- }
- batch_head = batch_tail = 0;
+
+ batch_pos = batch_credit = batch_samples = 0;
batch_max = size;
batch_tqueue.routine = batch_entropy_process;
batch_tqueue.data = r;
@@ -644,56 +638,61 @@
}
/*
- * Changes to the entropy data is put into a queue rather than being added to
- * the entropy counts directly. This is presumably to avoid doing heavy
- * hashing calculations during an interrupt in add_timer_randomness().
+ * Changes to the entropy data are put into a queue rather than being
+ * added to the entropy counts directly. This is to avoid doing heavy
+ * hashing calculations during an interrupt in add_timing_entropy().
* Instead, the entropy is only added to the pool once per timer tick.
+ *
+ * The batch pool intentionally allows wrap-around, to protect against
+ * flooding of untrusted data. Non-random data will not correlate with
+ * random data and can be safely XORed over existing data.
*/
-void batch_entropy_store(u32 a, u32 b, int num)
-{
- int new;
+void batch_entropy_store(u32 val, int bits)
+{
if (!batch_max)
return;
- batch_entropy_pool[2*batch_head] = a;
- batch_entropy_pool[(2*batch_head) + 1] = b;
- batch_entropy_credit[batch_head] = num;
-
- new = (batch_head+1) & (batch_max-1);
- if (new != batch_tail) {
- queue_task(&batch_tqueue, &tq_timer);
- batch_head = new;
- } else {
- DEBUG_ENT("batch entropy buffer full\n");
- }
+ batch_entropy_pool[batch_pos] ^= val;
+ batch_credit+=bits;
+ batch_samples++;
+ batch_pos = (batch_pos+1) & (batch_max-1);
+
+ queue_task(&batch_tqueue, &tq_timer);
}
/*
- * Flush out the accumulated entropy operations, adding entropy to the passed
- * store (normally random_state). If that store has enough entropy, alternate
- * between randomizing the data of the primary and secondary stores.
+ * Flush out the accumulated entropy operations, adding entropy to the
+ * passed store (normally random_state). Alternate between randomizing
+ * the data of the primary and secondary stores.
*/
static void batch_entropy_process(void *private_)
{
- struct entropy_store *r = (struct entropy_store *) private_, *p;
- int max_entropy = r->poolinfo.POOLBITS;
-
+ struct entropy_store *r = (struct entropy_store *) private_;
+ int samples, credit;
+
if (!batch_max)
return;
- p = r;
- while (batch_head != batch_tail) {
- if (r->entropy_count >= max_entropy) {
- r = (r == sec_random_state) ? random_state :
- sec_random_state;
- max_entropy = r->poolinfo.POOLBITS;
- }
- add_entropy_words(r, batch_entropy_pool + 2*batch_tail, 2);
- credit_entropy_store(r, batch_entropy_credit[batch_tail]);
- batch_tail = (batch_tail+1) & (batch_max-1);
+ /* switch pools if current full */
+ if (r->entropy_count >= r->poolinfo.POOLBITS) {
+ r = (r == sec_random_state) ?
+ random_state : sec_random_state;
}
- if (p->entropy_count >= random_read_wakeup_thresh)
+
+ credit=batch_credit;
+ samples=batch_samples;
+ batch_pos = batch_credit = batch_samples = 0;
+
+ /* Don't allow more credit BITS than pool WORDS */
+ if(credit > batch_max) credit=batch_max;
+ /* Check for pool wrap-around */
+ if(samples > batch_max) samples=batch_max;
+
+ add_entropy_words(r, batch_entropy_pool, samples);
+ credit_entropy_store(r, credit);
+
+ if (r->entropy_count >= random_read_wakeup_thresh)
wake_up_interruptible(&random_read_wait);
}
@@ -707,14 +706,12 @@
struct timer_rand_state {
__u32 last_time;
__s32 last_delta,last_delta2;
- int dont_count_entropy:1;
};
static struct timer_rand_state keyboard_timer_state;
static struct timer_rand_state mouse_timer_state;
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
@@ -751,7 +748,7 @@
* We take into account the first, second and third-order deltas
* in order to make our estimate.
*/
- if (!state->dont_count_entropy) {
+ if (state) {
delta = time - state->last_time;
state->last_time = time;
@@ -782,7 +779,18 @@
entropy = int_ln_12bits(delta);
}
- batch_entropy_store(num, time, entropy);
+ 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);
}
void add_keyboard_randomness(unsigned char scancode)
@@ -802,24 +810,12 @@
void add_interrupt_randomness(int irq)
{
- if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
- return;
-
- add_timer_randomness(irq_timer_state[irq], 0x100+irq);
+ add_timer_randomness(0, irq);
}
void add_blkdev_randomness(int major)
{
- if (major >= MAX_BLKDEV)
- return;
-
- if (blkdev_timer_state[major] == 0) {
- rand_initialize_blkdev(major, GFP_ATOMIC);
- if (blkdev_timer_state[major] == 0)
- return;
- }
-
- add_timer_randomness(blkdev_timer_state[major], 0x200+major);
+ add_timer_randomness(0, 0x200+major);
}
/******************************************************************
@@ -1270,8 +1266,6 @@
__u32 tmp[TMP_BUF_SIZE];
__u32 x;
- add_timer_randomness(&extract_timer_state, nbytes);
-
/* Redundant, but just in case... */
if (r->entropy_count > r->poolinfo.POOLBITS)
r->entropy_count = r->poolinfo.POOLBITS;
@@ -1352,7 +1346,6 @@
nbytes -= i;
buf += i;
ret += i;
- add_timer_randomness(&extract_timer_state, nbytes);
}
/* Wipe data just returned from memory */
@@ -1429,53 +1422,18 @@
#ifdef CONFIG_SYSCTL
sysctl_init_random(random_state);
#endif
- for (i = 0; i < NR_IRQS; i++)
- irq_timer_state[i] = NULL;
- for (i = 0; i < MAX_BLKDEV; i++)
- blkdev_timer_state[i] = NULL;
memset(&keyboard_timer_state, 0, sizeof(struct timer_rand_state));
memset(&mouse_timer_state, 0, sizeof(struct timer_rand_state));
- memset(&extract_timer_state, 0, sizeof(struct timer_rand_state));
- extract_timer_state.dont_count_entropy = 1;
}
void rand_initialize_irq(int irq)
{
- struct timer_rand_state *state;
-
- if (irq >= NR_IRQS || irq_timer_state[irq])
- return;
-
- /*
- * If kmalloc returns null, we just won't use that entropy
- * source.
- */
- state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
- if (state) {
- memset(state, 0, sizeof(struct timer_rand_state));
- irq_timer_state[irq] = state;
- }
}
void rand_initialize_blkdev(int major, int mode)
{
- struct timer_rand_state *state;
-
- if (major >= MAX_BLKDEV || blkdev_timer_state[major])
- return;
-
- /*
- * If kmalloc returns null, we just won't use that entropy
- * source.
- */
- state = kmalloc(sizeof(struct timer_rand_state), mode);
- if (state) {
- memset(state, 0, sizeof(struct timer_rand_state));
- blkdev_timer_state[major] = state;
- }
}
-
static ssize_t
random_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
{
@@ -1872,6 +1830,10 @@
{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 -urN -x '.patch*' -x '*.orig' orig/include/linux/random.h work/include/linux/random.h
--- orig/include/linux/random.h 2002-07-20 14:11:18.000000000 -0500
+++ work/include/linux/random.h 2002-09-28 00:16:14.000000000 -0500
@@ -46,7 +46,7 @@
extern void rand_initialize_irq(int irq);
extern void rand_initialize_blkdev(int irq, int mode);
-extern void batch_entropy_store(u32 a, u32 b, int num);
+extern void batch_entropy_store(u32 val, int bits);
extern void add_keyboard_randomness(unsigned char scancode);
extern void add_mouse_randomness(__u32 mouse_data);
diff -urN -x '.patch*' -x '*.orig' orig/include/linux/sysctl.h work/include/linux/sysctl.h
--- orig/include/linux/sysctl.h 2002-09-20 11:03:37.000000000 -0500
+++ work/include/linux/sysctl.h 2002-09-28 00:16:14.000000000 -0500
@@ -185,7 +185,8 @@
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 */