X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/bc0e1c6cb91cbf8bed2ba44e44c5e46209524e90..feae2dfc998c2e9433cb88da64cab0fdc7e5896c:/sshrand.c

diff --git a/sshrand.c b/sshrand.c
index a7b3dc4e..4c33f4a0 100644
--- a/sshrand.c
+++ b/sshrand.c
@@ -4,6 +4,10 @@
 
 #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));
@@ -37,10 +41,13 @@ struct RandPool {
 
     unsigned char incomingb[HASHINPUT];
     int incomingpos;
+
+    int stir_pending;
 };
 
 static struct RandPool pool;
 int random_active = 0;
+long next_noise_collection;
 
 static void random_stir(void)
 {
@@ -48,6 +55,14 @@ static void random_stir(void)
     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);
@@ -111,6 +126,8 @@ static 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)
@@ -182,16 +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)
 {
     if (!random_active) {
 	memset(&pool, 0, sizeof(pool));    /* just to start with */
 
-	random_active = 1;
-
 	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)