random: add new ioctl RNDRESEEDCRNG

Add a new ioctl which forces the the crng to be reseeded.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

2 files changed, 15 insertions, 1 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 898233f594b4..3cd3aae24d6d 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -429,6 +429,7 @@ struct crng_state primary_crng = {
 static int crng_init = 0;
 #define crng_ready() (likely(crng_init > 1))
 static int crng_init_cnt = 0;
+static unsigned long crng_global_init_time = 0;
 #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
 static void _extract_crng(struct crng_state *crng,
                           __u32 out[CHACHA20_BLOCK_WORDS]);
@@ -933,7 +934,8 @@ static void _extract_crng(struct crng_state *crng,
         unsigned long v, flags;
 
         if (crng_ready() &&
-            time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))
+            (time_after(crng_global_init_time, crng->init_time) ||
+             time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
                 crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
         spin_lock_irqsave(&crng->lock, flags);
         if (arch_get_random_long(&v))
@@ -1757,6 +1759,7 @@ static int rand_initialize(void)
         init_std_data(&input_pool);
         init_std_data(&blocking_pool);
         crng_initialize(&primary_crng);
+        crng_global_init_time = jiffies;
         return 0;
 }
 early_initcall(rand_initialize);
@@ -1930,6 +1933,14 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
                 input_pool.entropy_count = 0;
                 blocking_pool.entropy_count = 0;
                 return 0;
+        case RNDRESEEDCRNG:
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+                if (crng_init < 2)
+                        return -ENODATA;
+                crng_reseed(&primary_crng, NULL);
+                crng_global_init_time = jiffies - 1;
+                return 0;
         default:
                 return -EINVAL;
         }
diff --git a/include/uapi/linux/random.h b/include/uapi/linux/random.h
index c34f4490d025..26ee91300e3e 100644
--- a/include/uapi/linux/random.h
+++ b/include/uapi/linux/random.h
@@ -35,6 +35,9 @@
 /* Clear the entropy pool and associated counters.  (Superuser only.) */
 #define RNDCLEARPOOL    _IO( 'R', 0x06 )
 
+/* Reseed CRNG.  (Superuser only.) */
+#define RNDRESEEDCRNG   _IO( 'R', 0x07 )
+
 struct rand_pool_info {
         int     entropy_count;
         int     buf_size;