Add mutex protection for the fortuna PRNG

The fortuna PRNG has an statically held internal state. Prevent
concurrent access to this internal state by adding mutexes around
all of the access classes.

Signed-off-by: Love Hornquist Astrand <lha@h5l.org>

lib/hcrypto/rand-fortuna.c

@@ -34,6 +34,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <rand.h>
+#include <heim_threads.h>
 
 #ifdef KRB5
 #include <krb5-types.h>
@@ -441,11 +442,21 @@ static int	have_entropy;
 #define FORTUNA_RESEED_BYTE	10000
 static unsigned	resend_bytes;
 
+/*
+ * This mutex protects all of the above static elements from concurrent
+ * access by multiple threads
+ */
+static HEIMDAL_MUTEX fortuna_mutex = HEIMDAL_MUTEX_INITIALIZER;
+
 /*
  * Try our best to do an inital seed
  */
 #define INIT_BYTES	128
 
+/*
+ * fortuna_mutex must be held across calls to this function
+ */
+
 static int
 fortuna_reseed(void)
 {
@@ -537,6 +548,9 @@ fortuna_reseed(void)
     return entropy_p;
 }
 
+/*
+ * fortuna_mutex must be held by callers of this function
+ */
 static int
 fortuna_init(void)
 {
@@ -555,32 +569,50 @@ fortuna_init(void)
 static void
 fortuna_seed(const void *indata, int size)
 {
+    HEIMDAL_MUTEX_lock(&fortuna_mutex);
+
     fortuna_init();
     add_entropy(&main_state, indata, size);
     if (size >= INIT_BYTES)
 	have_entropy = 1;
+
+    HEIMDAL_MUTEX_unlock(&fortuna_mutex);
 }
 
 static int
 fortuna_bytes(unsigned char *outdata, int size)
 {
+    int ret = 0;
+
+    HEIMDAL_MUTEX_lock(&fortuna_mutex);
+
     if (!fortuna_init())
-	return 0;
+	goto out;
+
     resend_bytes += size;
     if (resend_bytes > FORTUNA_RESEED_BYTE || resend_bytes < size) {
 	resend_bytes = 0;
 	fortuna_reseed();
     }
     extract_data(&main_state, size, outdata);
-    return 1;
+    ret = 1;
+
+out:
+    HEIMDAL_MUTEX_unlock(&fortuna_mutex);
+
+    return ret;
 }
 
 static void
 fortuna_cleanup(void)
 {
+    HEIMDAL_MUTEX_lock(&fortuna_mutex);
+
     init_done = 0;
     have_entropy = 0;
     memset(&main_state, 0, sizeof(main_state));
+
+    HEIMDAL_MUTEX_unlock(&fortuna_mutex);
 }
 
 static void
@@ -598,7 +630,13 @@ fortuna_pseudorand(unsigned char *outdata, int size)
 static int
 fortuna_status(void)
 {
-    return fortuna_init() ? 1 : 0;
+    int result;
+
+    HEIMDAL_MUTEX_lock(&fortuna_mutex);
+    result = fortuna_init();
+    HEIMDAL_MUTEX_unlock(&fortuna_mutex);
+
+    return result ? 1 : 0;
 }
 
 const RAND_METHOD hc_rand_fortuna_method = {