crypto: special case ∞+a, a+∞ and a+a in p224.

crypto/p224_unittest.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string.h>
 #include <stdio.h>
 
 #include "crypto/p224.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 788 matching lines @@
       reinterpret_cast<const char *>(kNISTTestVectors[10].affine), 56)));
   ASSERT_TRUE(b.SetFromString(base::StringPiece(
       reinterpret_cast<const char *>(kNISTTestVectors[11].affine), 56)));
 
   p224::Negate(b, &minus_b);
   p224::Add(a, b, &sum);
   EXPECT_TRUE(memcmp(&sum, &a, sizeof(sum) != 0));
   p224::Add(minus_b, sum, &a_again);
   EXPECT_TRUE(a_again.ToString() == a.ToString());
 }
+
+TEST(P224, Infinity) {
+  char zeros[56];
+  memset(zeros, 0, sizeof(zeros));
+
+  // Test that x^0 = ∞.
+  Point a;
+  p224::ScalarBaseMult(reinterpret_cast<const uint8_t*>(zeros), &a);
+  EXPECT_TRUE(memcmp(zeros, a.ToString().data(), sizeof(zeros)) == 0);
+
+  // We shouldn't allow ∞ to be imported.
+  EXPECT_FALSE(a.SetFromString(std::string(zeros, sizeof(zeros))));
+}