X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/putty/blobdiff_plain/93b581bd031b2270deb7f45440e61a1044fe94da..e99bb8bfc8d2c1a47b6ae90ef43683d191c30f66:/sshrand.c

diff --git a/sshrand.c b/sshrand.c
index 7c401af4..4c33f4a0 100644
--- a/sshrand.c
+++ b/sshrand.c
@@ -2,7 +2,12 @@
  * cryptographic random number generator for PuTTY's ssh client
  */
 
+#include "putty.h"
 #include "ssh.h"
+#include <assert.h>
+
+/* Collect environmental noise every 5 minutes */
+#define NOISE_REGULAR_INTERVAL (5*60*TICKSPERSEC)
 
 void noise_get_heavy(void (*func) (void *, int));
 void noise_get_light(void (*func) (void *, int));
@@ -36,17 +41,28 @@ struct RandPool {
 
     unsigned char incomingb[HASHINPUT];
     int incomingpos;
+
+    int stir_pending;
 };
 
 static struct RandPool pool;
 int random_active = 0;
+long next_noise_collection;
 
-void random_stir(void)
+static void random_stir(void)
 {
     word32 block[HASHINPUT / sizeof(word32)];
     word32 digest[HASHSIZE / sizeof(word32)];
     int i, j, k;
 
+    /*
+     * noise_get_light will call random_add_noise, which may call
+     * back to here. Prevent recursive stirs.
+     */
+    if (pool.stir_pending)
+	return;
+    pool.stir_pending = TRUE;
+
     noise_get_light(random_add_noise);
 
     SHATransform((word32 *) pool.incoming, (word32 *) pool.incomingb);
@@ -110,6 +126,8 @@ void random_stir(void)
     memcpy(pool.incoming, digest, sizeof(digest));
 
     pool.poolpos = sizeof(pool.incoming);
+
+    pool.stir_pending = FALSE;
 }
 
 void random_add_noise(void *noise, int length)
@@ -181,14 +199,37 @@ static void random_add_heavynoise_bitbybit(void *noise, int length)
     pool.poolpos = i;
 }
 
-void random_init(void)
+static void random_timer(void *ctx, unsigned long now)
+{
+    if (random_active > 0 && now == next_noise_collection) {
+	noise_regular();
+	next_noise_collection =
+	    schedule_timer(NOISE_REGULAR_INTERVAL, random_timer, &pool);
+    }
+}
+
+void random_ref(void)
 {
-    memset(&pool, 0, sizeof(pool));    /* just to start with */
+    if (!random_active) {
+	memset(&pool, 0, sizeof(pool));    /* just to start with */
 
-    random_active = 1;
+	noise_get_heavy(random_add_heavynoise_bitbybit);
+	random_stir();
 
-    noise_get_heavy(random_add_heavynoise_bitbybit);
-    random_stir();
+	next_noise_collection =
+	    schedule_timer(NOISE_REGULAR_INTERVAL, random_timer, &pool);
+    }
+
+    random_active++;
+}
+
+void random_unref(void)
+{
+    random_active--;
+    assert(random_active >= 0);
+    if (random_active) return;
+
+    expire_timer_context(&pool);
 }
 
 int random_byte(void)
@@ -201,7 +242,10 @@ int random_byte(void)
 
 void random_get_savedata(void **data, int *len)
 {
+    void *buf = snewn(POOLSIZE / 2, char);
     random_stir();
-    *data = pool.pool + pool.poolpos;
+    memcpy(buf, pool.pool + pool.poolpos, POOLSIZE / 2);
     *len = POOLSIZE / 2;
+    *data = buf;
+    random_stir();
 }