python3.5/00250-getentropy.patch

diff -r ee1390c9b585 Python/random.c
--- a/Python/random.c	Wed Jan 04 12:02:30 2017 +0100
+++ b/Python/random.c	Wed Jan 04 18:32:21 2017 +0100
@@ -77,45 +77,8 @@ win32_urandom(unsigned char *buffer, Py_
     return 0;
 }
 
-/* Issue #25003: Don't use getentropy() on Solaris (available since
- * Solaris 11.3), it is blocking whereas os.urandom() should not block. */
-#elif defined(HAVE_GETENTROPY) && !defined(sun)
-#define PY_GETENTROPY 1
-
-/* Fill buffer with size pseudo-random bytes generated by getentropy().
-   Return 0 on success, or raise an exception and return -1 on error.
-
-   If raise is zero, don't raise an exception on error. */
-static int
-py_getentropy(char *buffer, Py_ssize_t size, int raise)
-{
-    while (size > 0) {
-        Py_ssize_t len = Py_MIN(size, 256);
-        int res;
+#else   /* !MS_WINDOWS */
 
-        if (raise) {
-            Py_BEGIN_ALLOW_THREADS
-            res = getentropy(buffer, len);
-            Py_END_ALLOW_THREADS
-        }
-        else {
-            res = getentropy(buffer, len);
-        }
-
-        if (res < 0) {
-            if (raise) {
-                PyErr_SetFromErrno(PyExc_OSError);
-            }
-            return -1;
-        }
-
-        buffer += len;
-        size -= len;
-    }
-    return 0;
-}
-
-#else
 
 #if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
 #define PY_GETRANDOM 1
@@ -217,6 +180,59 @@ py_getrandom(void *buffer, Py_ssize_t si
     }
     return 1;
 }
+
+/* Issue #25003: Don't use getentropy() on Solaris (available since
+ * Solaris 11.3), it is blocking whereas os.urandom() should not block. */
+#elif defined(HAVE_GETENTROPY) && !defined(sun)
+#define PY_GETENTROPY 1
+
+/* Fill buffer with size pseudo-random bytes generated by getentropy().
+   Return 1 on success, or raise an exception and return -1 on error.
+
+   If raise is zero, don't raise an exception on error. */
+static int
+py_getentropy(char *buffer, Py_ssize_t size, int raise)
+{
+    /* Is getentropy() supported by the running kernel? Set to 0 if
+       getentropy() failed with ENOSYS. */
+    static int getentropy_works = 1;
+
+    if (!getentropy_works) {
+        return 0;
+    }
+
+    while (size > 0) {
+        Py_ssize_t len = Py_MIN(size, 256);
+        int res;
+
+        if (raise) {
+            Py_BEGIN_ALLOW_THREADS
+            res = getentropy(buffer, len);
+            Py_END_ALLOW_THREADS
+        }
+        else {
+            res = getentropy(buffer, len);
+        }
+
+        if (res < 0) {
+            /* ENOSYS: the inner syscall is not supported by the running
+               kernel. */
+            if (errno == ENOSYS) {
+                getentropy_works = 0;
+                return 0;
+            }
+
+            if (raise) {
+                PyErr_SetFromErrno(PyExc_OSError);
+            }
+            return -1;
+        }
+
+        buffer += len;
+        size -= len;
+    }
+    return 1;
+}
 #endif
 
 static struct {
@@ -236,7 +252,7 @@ dev_urandom(char *buffer, Py_ssize_t siz
 {
     int fd;
     Py_ssize_t n;
-#ifdef PY_GETRANDOM
+#if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
     int res;
 #endif
 
@@ -244,17 +260,20 @@ dev_urandom(char *buffer, Py_ssize_t siz
 
 #ifdef PY_GETRANDOM
     res = py_getrandom(buffer, size, blocking, raise);
+#elif defined(PY_GETENTROPY)
+    res = py_getentropy(buffer, size, raise);
+#endif
+#if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
     if (res < 0) {
         return -1;
     }
     if (res == 1) {
         return 0;
     }
-    /* getrandom() failed with ENOSYS or EPERM,
-       fall back on reading /dev/urandom */
+    /* function failed with ENOSYS or EPERM, fall back on reading
+       from /dev/urandom */
 #endif
 
-
     if (raise) {
         struct _Py_stat_struct st;
 
@@ -349,8 +368,8 @@ dev_urandom_close(void)
         urandom_cache.fd = -1;
     }
 }
+#endif   /* !MS_WINDOWS */
 
-#endif
 
 /* Fill buffer with pseudo-random bytes generated by a linear congruent
    generator (LCG):
@@ -395,8 +414,6 @@ pyurandom(void *buffer, Py_ssize_t size,
 
 #ifdef MS_WINDOWS
     return win32_urandom((unsigned char *)buffer, size, raise);
-#elif defined(PY_GETENTROPY)
-    return py_getentropy(buffer, size, raise);
 #else
     return dev_urandom(buffer, size, blocking, raise);
 #endif
@@ -491,8 +508,6 @@ void
         CryptReleaseContext(hCryptProv, 0);
         hCryptProv = 0;
     }
-#elif defined(PY_GETENTROPY)
-    /* nothing to clean */
 #else
     dev_urandom_close();
 #endif