WebCrypto: Add WebKit API structure for keys.

Source/modules/crypto/Key.cpp

+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "modules/crypto/Key.h"
+
+#include "modules/crypto/Algorithm.h"
+
+namespace WebCore {
+
+namespace {
+
+const char* keyTypeToString(WebKit::WebCryptoKeyType type)
+{
+    switch (type) {
+    case WebKit::WebCryptoKeyTypeSecret:
+        return "secret";
+    case WebKit::WebCryptoKeyTypePublic:
+        return "public";
+    case WebKit::WebCryptoKeyTypePrivate:
+        return "private";
+    }
+    ASSERT_NOT_REACHED();
+    return 0;
+}
+
+const char* keyUsageToString(WebKit::WebCryptoKeyUsage usage)
+{
+    switch (usage) {
+    case WebKit::WebCryptoKeyUsageEncrypt:
+        return "encrypt";
+    case WebKit::WebCryptoKeyUsageDecrypt:
+        return "decrypt";
+    case WebKit::WebCryptoKeyUsageSign:
+        return "sign";
+    case WebKit::WebCryptoKeyUsageVerify:
+        return "verify";
+    case WebKit::WebCryptoKeyUsageDerive:
+        return "derive";
+    case WebKit::WebCryptoKeyUsageWrap:
+        return "wrap";
+    case WebKit::WebCryptoKeyUsageUnwrap:
+        return "unwrap";
+    }
+    return 0;

[abarth-chromium, 2013/07/03 18:01:41]

ASSERT_NOT_REACHED();

[eroman, 2013/07/03 19:18:06]

I am in fact relying on the 0 case here:

<long_winded_optional_explanation>

In order to enumerate the WebCrytoKeyUsage in a generic fashion, in
"Key::keyUsage()" I construct WebCryptoKeyUsage values directly out of integers
by using the expression (1 << i), for i starting at 0, up until N.

I didn't want to hard-code the maximum value of "i", for fear that the code
would silently break if new values are added to WebCryptoKeyUsage in the future.
What I did instead is to keep iterating and increasing "i" until
keyUsageToString() returns 0. This indicates that the "usage" value passed in
was not a valid enum, and hence iteration is done.

With this approach, if a new enumerated value gets added to WebCryptoKeyUsage
then compilation of the switch statement will fail with a warning, as it has no
"default" case. Once the developer updates the switch statement to fix the
compile break, then everything else "just works".

The alternative would be to add some "last usage" value to the end of the enum
definition (so the hardcoded bit is closer to the definition, and more likely to
get updated). In this case though, since the enumerated values define a bitfield
(and are not just increasing numbers), then defining and using the sentinel is a
bit uglier (and it ends up polluting the enum with a non-value)

</long_winded_optional_explanation>

In summary: I can add an ASSERT_NOT_REACHED() here, however it will mean
changing the design of the keyUsage() function below.

+}
+
+} // namespace
+
+Key::Key(const WebKit::WebCryptoKey& key)
+    : m_key(key)
+{
+    ScriptWrappable::init(this);
+}
+
+String Key::type() const
+{
+    return ASCIILiteral(keyTypeToString(m_key.type()));
+}
+
+bool Key::extractable() const
+{
+    return m_key.extractable();
+}
+
+Algorithm* Key::algorithm()
+{
+    if (!m_algorithm)
+        m_algorithm = Algorithm::create(m_key.algorithm());
+    return m_algorithm.get();
+}
+
+Vector<String> Key::keyUsage() const
+{
+    Vector<String> v;

[abarth-chromium, 2013/07/03 18:01:41]

v -> result

Please use complete words in variable names.  (We do use i as a look index
though.)

[eroman, 2013/07/03 19:18:06]

Done.

+
+    // The WebCryptoKeyUsage values are consecutive powers of 2. Test each one in order.
+    for (int i = 0; ; ++i) {
+        // Note that this won't be a valid WebCryptoKeyUsage during the last iteration.
+        WebKit::WebCryptoKeyUsage usage = static_cast<WebKit::WebCryptoKeyUsage>(1 << i);
+        const char* usageString = keyUsageToString(usage);
+        if (!usageString)
+            break;
+
+        if (m_key.keyUsage() & usage)
+            v.append(ASCIILiteral(usageString));
+    }
+    return v;
+}
+
+} // namespace WebCore