rnd-linux: make getrandom back-end robust against EINTR failures

diff --git a/lib/nettle/rnd-linux.c b/lib/nettle/rnd-linux.c
index e61566b88db3f788992faec30cd57cce4b85ff9f..3f59332977a80d2166309b1287d3c300396be32a 100644 (file)
--- a/lib/nettle/rnd-linux.c
+++ b/lib/nettle/rnd-linux.c
@@ -74,19 +74,37 @@ static unsigned have_getrandom(void)
 static int _rnd_get_system_entropy_getrandom(void* _rnd, size_t size)
 {
        int ret;
-       ret = getrandom(_rnd, size, 0);
+       do {
+               ret = getrandom(_rnd, size, 0);
+       } while (ret == -1 && errno == EINTR);
+
        if (ret == -1) {
+               int e = errno;
                gnutls_assert();
                _gnutls_debug_log
                        ("Failed to use getrandom: %s\n",
-                                        strerror(errno));
+                                        strerror(e));
                return GNUTLS_E_RANDOM_DEVICE_ERROR;
        }
 
-       /* This function is only used internally for small sizes which
-        * should be delivered by getrandom(). */
-       if ((size_t)ret != size)
-               return gnutls_assert_val(GNUTLS_E_RANDOM_DEVICE_ERROR);
+       /* Since this function is only used internally for small sizes,
+        * any limits of getrandom() are not reached. The only way
+        * to receive less data than asked, is due to a signal interrupting
+        * the system call. In that case we retry. */
+       if ((size_t)ret != size) {
+               unsigned i;
+               for (i=0;i<3;i++) {
+                       do {
+                               ret = getrandom(_rnd, size, 0);
+                       } while (ret == -1 && errno == EINTR);
+
+                       if ((size_t)ret == size)
+                               break;
+               }
+
+               if (ret == -1 || (size_t)ret != size)
+                       return gnutls_assert_val(GNUTLS_E_RANDOM_DEVICE_ERROR);
+       }
 
        return 0;
 }
@@ -106,10 +124,11 @@ static int _rnd_get_system_entropy_urandom(void* _rnd, size_t size)
                } while (res < 0 && errno == EINTR);
 
                if (res <= 0) {
+                       int e = errno;
                        if (res < 0) {
                                _gnutls_debug_log
                                        ("Failed to read /dev/urandom: %s\n",
-                                        strerror(errno));
+                                        strerror(e));
                        } else {
                                _gnutls_debug_log
                                        ("Failed to read /dev/urandom: end of file\n");