Support SHA-256 on pre-Vista Windows clients

net/cert/sha256_legacy_support_win.h

Index: net/cert/sha256_legacy_support_win.h
diff --git a/net/cert/sha256_legacy_support_win.h b/net/cert/sha256_legacy_support_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..c98414ca94b882d5b060a91fe6c6795a9b327c09
--- /dev/null
+++ b/net/cert/sha256_legacy_support_win.h
@@ -0,0 +1,48 @@
+// Copyright 2014 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.
+
+#ifndef NET_CERT_SHA256_LEGACY_SUPPORT_WIN_H_
+#define NET_CERT_SHA256_LEGACY_SUPPORT_WIN_H_
+
+#include <windows.h>
+#include <wincrypt.h>
+
+#include "net/base/net_export.h"
+
+namespace net {
+
+namespace sha256_interception {
+
+typedef BOOL (WINAPI* CryptVerifyCertificateSignatureExFunc)(
+    HCRYPTPROV_LEGACY provider,
+    DWORD encoding_type,
+    DWORD subject_type,
+    void* subject_data,
+    DWORD issuer_type,
+    void* issuer_data,
+    DWORD flags,
+    void* extra);
+
+// Interception function meant to be called whenever
+// CryptVerifyCertificateSignatureEx is called. Note that the calling
+// conventions do not match, as the caller is expected to ensure that their
+// interposed function handles the calling conventions and provides a pointer
+// to the original CryptVerifyCertificateSignatureEx (e.g. to handle parameters
+// and keys that are not supported).
+NET_EXPORT BOOL CryptVerifyCertificateSignatureExHook(
+    CryptVerifyCertificateSignatureExFunc original_func,
+    HCRYPTPROV_LEGACY provider,
+    DWORD encoding_type,
+    DWORD subject_type,
+    void* subject_data,
+    DWORD issuer_type,
+    void* issuer_data,
+    DWORD flags,
+    void* extra);
+
+}  // namespace sha256_interception
+
+}  // namespace net
+
+#endif  // NET_CERT_SHA256_LEGACY_SUPPORT_WIN_H_