Initial patch from Will.

src/platform/cryptohome/username_passhash.h

-// Copyright (c) 2009-2010 The Chromium OS Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// UsernamePasshash wraps a username/salted password hash pair that
-// can be used to authenticate a user.
-
-#ifndef CRYPTOHOME_USERNAME_PASSHASH_H_
-#define CRYPTOHOME_USERNAME_PASSHASH_H_
-
-#include "cryptohome/credentials.h"
-
-#include <string.h>
-
-#include "base/basictypes.h"
-
-namespace cryptohome {
-
-class UsernamePasshash : public Credentials {
- public:
-  // |passhash| is a weak hash of the user's password, using the same
-  // algorithm that pam/pam_google/pam_mount use to get the user's
-  // plaintext passhash safely passed on to the login session.  That
-  // means we compute a sha256sum of the ASCII encoded system salt plus
-  // the plaintext passhash, ASCII encode the result, and take the first
-  // 32 bytes.  To say that in bash...
-  //
-  //    $(cat <(echo -n $(xxd -p "$SYSTEM_SALT_FILE"))
-  //      <(echo -n "$PASSHASH") | sha256sum | head -c 32)
-  //
-  UsernamePasshash(const char *username, const int username_length,
-                   const char *passhash, const int passhash_length);
-
-  ~UsernamePasshash() {}
-
-  // Overridden from cryptohome::Credentials
-  void GetFullUsername(char *name_buffer, int length) const;
-  void GetPartialUsername(char *name_buffer, int length) const;
-  std::string GetObfuscatedUsername(const chromeos::Blob &system_salt) const;
-  std::string GetPasswordWeakHash(const chromeos::Blob &system_salt) const;
-
- private:
-  std::string username_;
-  std::string passhash_;
-
-  DISALLOW_COPY_AND_ASSIGN(UsernamePasshash);
-};
-
-}  // namespace cryptohome
-
-#endif  // CRYPTOHOME_USERNAME_PASSHASH_H_