getrandom: loop around getrandom to get the requested number of bytes

This simplifies and enhanced the previous error handling code.

diff --git a/lib/nettle/rnd-linux.c b/lib/nettle/rnd-linux.c
index 3f59332977a80d2166309b1287d3c300396be32a..3ad9056cb38adc535c081cb6f7028bd085586ef2 100644 (file)
--- a/lib/nettle/rnd-linux.c
+++ b/lib/nettle/rnd-linux.c
@@ -71,13 +71,33 @@ static unsigned have_getrandom(void)
        return 0;
 }
 
-static int _rnd_get_system_entropy_getrandom(void* _rnd, size_t size)
+/* returns exactly the amount of bytes requested */
+static int force_getrandom(void *buf, size_t buflen, unsigned int flags)
 {
+       int left = buflen;
        int ret;
-       do {
-               ret = getrandom(_rnd, size, 0);
-       } while (ret == -1 && errno == EINTR);
+       uint8_t *p = buf;
+
+       while (left > 0) {
+               ret = getrandom(p, left, flags);
+               if (ret == -1) {
+                       if (errno != EINTR)
+                               return ret;
+               }
+
+               if (ret > 0) {
+                       left -= ret;
+                       p += ret;
+               }
+       }
+
+       return buflen;
+}
 
+static int _rnd_get_system_entropy_getrandom(void* _rnd, size_t size)
+{
+       int ret;
+       ret = force_getrandom(_rnd, size, 0);
        if (ret == -1) {
                int e = errno;
                gnutls_assert();
@@ -87,25 +107,6 @@ static int _rnd_get_system_entropy_getrandom(void* _rnd, size_t size)
                return 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;
 }
 #else