Hey all-
A while back I implemented a repetition check in the hardware RNG to
make it FIPS compliant. It was just pointed out to me that there was an item in
the requirement that I missed. Namely, when operating in FIPS mode, the RNG
should save the first n bit block that it produces for use in the repetition
check, but not return it to the caller (opting instead to return the next n bit
block which passes the repetiiton check instead. This patch corrects that.
Neil
Signed-off-by: Neil Horman <[email protected]>
random.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index d8a9255..6700248 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -399,6 +399,12 @@ module_param(debug, bool, 0644);
* storing entropy in an entropy pool.
*
**********************************************************************/
+#define EXTRACT_SIZE 10
+#define REP_CHECK_BLOCK_COPIED 1
+struct repetition_check {
+ __u8 last_data[EXTRACT_SIZE];
+ __u8 flags;
+};
struct entropy_store;
struct entropy_store {
@@ -414,7 +420,7 @@ struct entropy_store {
unsigned add_ptr;
int entropy_count;
int input_rotate;
- __u8 *last_data;
+ struct repetition_check *rep;
};
static __u32 input_pool_data[INPUT_POOL_WORDS];
@@ -714,7 +720,6 @@ void add_disk_randomness(struct gendisk *disk)
}
#endif
-#define EXTRACT_SIZE 10
/*********************************************************************
*
@@ -856,18 +861,24 @@ static ssize_t extract_entropy(struct entropy_store *r,
void *buf,
__u8 tmp[EXTRACT_SIZE];
unsigned long flags;
+repeat_extract:
xfer_secondary_pool(r, nbytes);
nbytes = account(r, nbytes, min, reserved);
while (nbytes) {
extract_buf(r, tmp);
- if (r->last_data) {
+ if (r->rep) {
spin_lock_irqsave(&r->lock, flags);
- if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
+ if ((r->rep->flags & REP_CHECK_BLOCK_COPIED) &&
+ !memcmp(tmp, r->rep->last_data, EXTRACT_SIZE))
panic("Hardware RNG duplicated output!\n");
- memcpy(r->last_data, tmp, EXTRACT_SIZE);
+ memcpy(r->rep->last_data, tmp, EXTRACT_SIZE);
spin_unlock_irqrestore(&r->lock, flags);
+ if (!(r->rep->flags & REP_CHECK_BLOCK_COPIED)) {
+ r->rep->flags |= REP_CHECK_BLOCK_COPIED;
+ goto repeat_extract;
+ }
}
i = min_t(int, nbytes, EXTRACT_SIZE);
memcpy(buf, tmp, i);
@@ -952,8 +963,10 @@ static void init_std_data(struct entropy_store *r)
mix_pool_bytes(r, &now, sizeof(now));
mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
/* Enable continuous test in fips mode */
- if (fips_enabled)
- r->last_data = kmalloc(EXTRACT_SIZE, GFP_KERNEL);
+ if (fips_enabled) {
+ r->rep = kmalloc(sizeof(struct repetition_check), GFP_KERNEL);
+ r->rep->flags = 0;
+ }
}
static int rand_initialize(void)
--
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