Simplify mbedtls_ct_memcmp_partial
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/constant_time.c b/library/constant_time.c
index fffc02f..8b41aed 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -158,13 +158,15 @@
for (size_t i = 0; i < n; i++) {
unsigned char x = A[i], y = B[i];
- int d = x ^ y;
+ unsigned int d = x ^ y;
mbedtls_ct_condition_t valid = mbedtls_ct_bool_and(mbedtls_ct_uint_ge(i, skip_head),
mbedtls_ct_uint_lt(i, valid_end));
diff |= mbedtls_ct_uint_if_else_0(valid, d);
}
- return (int) ((diff & 0xffff) | (diff >> 16));
+ /* Since we go byte-by-byte, the only bits set will be in the bottom 8 bits, so the
+ * cast from uint to int is safe. */
+ return (int) diff;
}
#endif