Fix cache index calculation error.

Author: serhiy-storchaka

Lib/test/test_binascii.py

@@ -202,6 +202,17 @@ def assertNonBase64Data(data, expected, ignorechars):
         assertNonBase64Data(b'a\nb==', b'i', ignorechars=bytearray(b'\n'))
         assertNonBase64Data(b'a\nb==', b'i', ignorechars=memoryview(b'\n'))
 
+        # Same byte in the bit cache: '\r' >> 3 == '\n' >> 3.
+        data = self.type2test(b'\r\n')
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(data, ignorechars=b'\r')
+        self.assertEqual(binascii.a2b_base64(data, ignorechars=b'\r\n'), b'')
+        # Same mask in the bit cache: ':' & 7 == '\n' & 7.
+        data = self.type2test(b':\n')
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(data, ignorechars=b':')
+        self.assertEqual(binascii.a2b_base64(data, ignorechars=b':\n'), b'')
+
         data = self.type2test(b'a\nb==')
         with self.assertRaises(TypeError):
             binascii.a2b_base64(data, ignorechars='')

Modules/binascii.c

@@ -476,11 +476,11 @@ ignorechar(unsigned char c, Py_buffer *ignorechars, char ignorecache[32])
     if (ignorechars->buf == NULL) {
         return 0;
     }
-    if (ignorecache[c >> 8] & (1 << (c & 7))) {
+    if (ignorecache[c >> 3] & (1 << (c & 7))) {
         return 1;
     }
     if (memchr(ignorechars->buf, c, ignorechars->len)) {
-        ignorecache[c >> 8] |= 1 << (c & 7);
+        ignorecache[c >> 3] |= 1 << (c & 7);
         return 1;
     }
     return 0;