Merge pull request #1986 from reaperhulk/cffi10

cffi 1.0

1 files changed, 22 insertions, 0 deletions

diff --git a/src/_cffi_src/hazmat_src/constant_time.c b/src/_cffi_src/hazmat_src/constant_time.c
new file mode 100644
index 00000000..0a48fe83
--- /dev/null
+++ b/src/_cffi_src/hazmat_src/constant_time.c
@@ -0,0 +1,22 @@
+// This file is dual licensed under the terms of the Apache License, Version
+// 2.0, and the BSD License. See the LICENSE file in the root of this
+// repository for complete details.
+
+uint8_t Cryptography_constant_time_bytes_eq(uint8_t *a, size_t len_a,
+                                            uint8_t *b, size_t len_b) {
+    size_t i = 0;
+    uint8_t mismatch = 0;
+    if (len_a != len_b) {
+        return 0;
+    }
+    for (i = 0; i < len_a; i++) {
+        mismatch |= a[i] ^ b[i];
+    }
+
+    /* Make sure any bits set are copied to the lowest bit */
+    mismatch |= mismatch >> 4;
+    mismatch |= mismatch >> 2;
+    mismatch |= mismatch >> 1;
+    /* Now check the low bit to see if it's set */
+    return (mismatch & 1) == 0;
+}