This factors pool reseeding out of normal entropy transfer. This allows
different pools to have different policy on how to reseed.
This patch also makes random_read actually use the entropy count in
the secondary pool rather than tracking off the primary.
diff -urN -x '.patch*' -x '*.orig' orig/drivers/char/random.c work/drivers/char/random.c
--- orig/drivers/char/random.c 2002-09-28 00:16:15.000000000 -0500
+++ work/drivers/char/random.c 2002-09-28 00:16:15.000000000 -0500
@@ -263,14 +263,14 @@
* The minimum number of bits of entropy before we wake up a read on
* /dev/random. Should be enough to do a significant reseed.
*/
-static int random_read_wakeup_thresh = 64;
+static int read_thresh = 64;
/*
* If the entropy count falls under this number of bits, then we
* should wake up processes which are selecting or polling on write
* access to /dev/random.
*/
-static int random_write_wakeup_thresh = 128;
+static int write_thresh = 128;
/*
* A pool of size .poolwords is stirred with a primitive polynomial
@@ -381,7 +381,7 @@
/*
* Static global variables
*/
-static struct entropy_store *input_pool, *blocking_pool;
+static struct entropy_store *input_pool, *blocking_pool, *nonblocking_pool;
static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
@@ -617,6 +617,7 @@
/* switch pools if current full */
if (r->entropy_count >= r->poolinfo->POOLBITS) r = blocking_pool;
+ if (r->entropy_count >= r->poolinfo->POOLBITS) r = nonblocking_pool;
/* Don't allow more credit BITS than pool WORDS */
if(credit > batch_max) credit=batch_max;
@@ -626,7 +627,7 @@
add_entropy_words(r, batch_entropy_pool, samples);
credit_entropy_store(r, credit);
- if (input_pool->entropy_count >= random_read_wakeup_thresh)
+ if (input_pool->entropy_count >= read_thresh)
wake_up_interruptible(&random_read_wait);
}
@@ -1159,37 +1160,9 @@
*********************************************************************/
#define EXTRACT_ENTROPY_USER 1
-#define EXTRACT_ENTROPY_SECONDARY 2
#define TMP_BUF_SIZE (HASH_BUFFER_SIZE + HASH_EXTRA_SIZE)
#define SEC_XFER_SIZE (TMP_BUF_SIZE*4)
-static ssize_t extract_entropy(struct entropy_store *r, void * buf,
- size_t nbytes, int flags);
-
-/*
- * This utility inline function is responsible for transfering entropy
- * from the primary pool to the secondary extraction pool. We pull
- * randomness under two conditions; one is if there isn't enough entropy
- * in the secondary pool. The other is after we have extracted 1024 bytes,
- * at which point we do a "catastrophic reseeding".
- */
-static void xfer_entropy(struct entropy_store *r, size_t nbytes)
-{
- __u32 tmp[TMP_BUF_SIZE];
-
- if (r->entropy_count < nbytes * 8 &&
- r->entropy_count < r->poolinfo->POOLBITS) {
- int bytes = min_t(int, nbytes, sizeof(tmp));
-
- DEBUG_ENT("xfer %d to %s (have %d, need %d)\n",
- bytes * 8, r->name, r->entropy_count, nbytes * 8);
-
- extract_entropy(input_pool, tmp, bytes, 0);
- add_entropy_words(r, tmp, bytes);
- credit_entropy_store(r, bytes*8);
- }
-}
-
/*
* This function extracts randomness from the "entropy pool", and
* returns it in a buffer. This function computes how many remaining
@@ -1197,10 +1170,6 @@
* number of bytes that are actually obtained. If the EXTRACT_ENTROPY_USER
* flag is given, then the buf pointer is assumed to be in user space.
*
- * If the EXTRACT_ENTROPY_SECONDARY flag is given, then we are actually
- * extracting entropy from the secondary pool, and can refill from the
- * primary pool if needed.
- *
* Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
*/
static ssize_t extract_entropy(struct entropy_store *r, void * buf,
@@ -1214,9 +1183,6 @@
if (r->entropy_count > r->poolinfo->POOLBITS)
r->entropy_count = r->poolinfo->POOLBITS;
- if (flags & EXTRACT_ENTROPY_SECONDARY)
- xfer_secondary_pool(r, nbytes);
-
DEBUG_ENT("%s has %d bits, want %d bits\n",
r->name, r->entropy_count, nbytes * 8);
@@ -1225,7 +1191,7 @@
else
r->entropy_count = 0;
- if (r->entropy_count < random_write_wakeup_thresh)
+ if (r->entropy_count < write_thresh)
wake_up_interruptible(&random_write_wait);
ret = 0;
@@ -1296,6 +1262,31 @@
return ret;
}
+/* Reseed pool with pull bits from input pool, provided input pool has
+ * more than thresh bits available. Pullbits should be sufficient for a
+ * "catastrophic reseed" - enough to make the destination pool
+ * unguessable should it be compromised
+ */
+void reseed_pool(struct entropy_store *r, int thresh, int pullbits)
+{
+ __u32 tmp[TMP_BUF_SIZE];
+ int bytes;
+
+ if (r->entropy_count > 8 ||
+ input_pool->entropy_count < thresh ||
+ pullbits < 0)
+ return;
+
+ bytes = min_t(int, pullbits/8, sizeof(tmp));
+
+ DEBUG_ENT("xfer %d to %s (have %d, want %d)\n",
+ bytes * 8, r->name, r->entropy_count, pullbits);
+
+ extract_entropy(input_pool, tmp, bytes, 0);
+ add_entropy_words(r, tmp, bytes);
+ credit_entropy_store(r, bytes*8);
+}
+
/*
* This function is the exported kernel interface. It returns some
* number of good random numbers, suitable for seeding TCP sequence
@@ -1303,14 +1294,16 @@
*/
void get_random_bytes(void *buf, int nbytes)
{
- if (blocking_pool)
- extract_entropy(blocking_pool, (char *) buf, nbytes,
- EXTRACT_ENTROPY_SECONDARY);
- else if (input_pool)
- extract_entropy(input_pool, (char *) buf, nbytes, 0);
- else
- printk(KERN_NOTICE "get_random_bytes called before "
- "random driver initialization\n");
+ if (!nonblocking_pool)
+ {
+ printk(KERN_NOTICE "get_random_bytes called before "
+ "random driver initialization\n");
+ return;
+ }
+
+ /* Leave enough for blocking pool to reseed itself */
+ reseed_pool(nonblocking_pool, read_thresh*2, read_thresh);
+ extract_entropy(nonblocking_pool, (char *) buf, nbytes, 0);
}
/*********************************************************************
@@ -1352,8 +1345,9 @@
{
input_pool = create_entropy_store(512, "input");
blocking_pool = create_entropy_store(128, "blocking");
+ nonblocking_pool = create_entropy_store(128, "nonblocking");
- if(!(input_pool && blocking_pool)) return;
+ if(!(input_pool && blocking_pool && nonblocking_pool)) return;
if(batch_entropy_init(256)) return;
init_std_data(input_pool);
@@ -1382,8 +1376,11 @@
return 0;
add_wait_queue(&random_read_wait, &wait);
+
while (nbytes > 0) {
set_current_state(TASK_INTERRUPTIBLE);
+
+ reseed_pool(input_pool, read_thresh, read_thresh);
n = nbytes;
if (n > SEC_XFER_SIZE)
@@ -1408,8 +1405,7 @@
blocking_pool->entropy_count);
n = extract_entropy(blocking_pool, buf, n,
- EXTRACT_ENTROPY_USER |
- EXTRACT_ENTROPY_SECONDARY);
+ EXTRACT_ENTROPY_USER);
if (n < 0) {
retval = n;
@@ -1438,9 +1434,10 @@
urandom_read(struct file * file, char * buf,
size_t nbytes, loff_t *ppos)
{
- return extract_entropy(blocking_pool, buf, nbytes,
- EXTRACT_ENTROPY_USER |
- EXTRACT_ENTROPY_SECONDARY);
+ reseed_pool(nonblocking_pool, read_thresh*2, read_thresh);
+
+ return extract_entropy(blocking_pool, buf, nbytes,
+ EXTRACT_ENTROPY_USER);
}
static unsigned int
@@ -1451,9 +1448,9 @@
poll_wait(file, &random_read_wait, wait);
poll_wait(file, &random_write_wait, wait);
mask = 0;
- if (input_pool->entropy_count >= random_read_wakeup_thresh)
+ if (input_pool->entropy_count >= read_thresh)
mask |= POLLIN | POLLRDNORM;
- if (input_pool->entropy_count < random_write_wakeup_thresh)
+ if (input_pool->entropy_count < write_thresh)
mask |= POLLOUT | POLLWRNORM;
return mask;
}
@@ -1513,7 +1510,7 @@
* Wake up waiting processes if we have enough
* entropy.
*/
- if (input_pool->entropy_count >= random_read_wakeup_thresh)
+ if (input_pool->entropy_count >= read_thresh)
wake_up_interruptible(&random_read_wait);
return 0;
case RNDGETPOOL:
@@ -1551,7 +1548,7 @@
* Wake up waiting processes if we have enough
* entropy.
*/
- if (input_pool->entropy_count >= random_read_wakeup_thresh)
+ if (input_pool->entropy_count >= read_thresh)
wake_up_interruptible(&random_read_wait);
return 0;
case RNDZAPENTCNT:
@@ -1756,11 +1753,11 @@
NULL, sizeof(int), 0444, NULL,
&proc_dointvec},
{RANDOM_READ_THRESH, "read_wakeup_threshold",
- &random_read_wakeup_thresh, sizeof(int), 0644, NULL,
+ &read_thresh, sizeof(int), 0644, NULL,
&proc_dointvec_minmax, &sysctl_intvec, 0,
&min_read_thresh, &max_read_thresh},
{RANDOM_WRITE_THRESH, "write_wakeup_threshold",
- &random_write_wakeup_thresh, sizeof(int), 0644, NULL,
+ &write_thresh, sizeof(int), 0644, NULL,
&proc_dointvec_minmax, &sysctl_intvec, 0,
&min_write_thresh, &max_write_thresh},
{RANDOM_BOOT_ID, "boot_id",
-
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/