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// Copyright 2016 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 COMPONENTS_CLIENT_UPDATE_PROTOCOL_ECDSA_H_
#define COMPONENTS_CLIENT_UPDATE_PROTOCOL_ECDSA_H_
#include <stdint.h>
#include <string>
#include <vector>
#include "base/memory/scoped_ptr.h"
#include "base/strings/string_piece.h"
namespace client_update_protocol {
// Client Update Protocol v2, or CUP-ECDSA, is used by Google Update (Omaha)
// servers to ensure freshness and authenticity of server responses over HTTP,
// without the overhead of HTTPS -- namely, no PKI, no guarantee of privacy, and
// no request replay protection.
//
// CUP-ECDSA relies on a single signing operation using ECDSA with SHA-256,
// instead of the original CUP which used HMAC-SHA1 with a random signing key
// encrypted using RSA.
//
// Each |Ecdsa| object represents a single network ping in flight -- a call to
// SignRequest() generates internal state that will be used by
// ValidateResponse().
class Ecdsa {
public:
~Ecdsa();
// Initializes this instance of CUP-ECDSA with a versioned public key.
// |key_version| must be non-negative. |public_key| is expected to be a
// DER-encoded ASN.1 SubjectPublicKeyInfo containing an ECDSA public key.
// Returns a NULL pointer on failure.
static scoped_ptr<Ecdsa> Create(int key_version,
const base::StringPiece& public_key);
// Generates freshness/authentication data for an outgoing ping.
// |request_body| contains the body of the ping in UTF-8. On return,
// |query_params| contains a set of query parameters (in UTF-8) to be appended
// to the URL.
//
// This method will store internal state in this instance used by calls to
// ValidateResponse(); if you need to have multiple pings in flight,
// initialize a separate CUP-ECDSA instance for each one.
void SignRequest(const base::StringPiece& request_body,
std::string* query_params);
// Validates a response given to a ping previously signed with
// SignRequest(). |response_body| contains the body of the response in
// UTF-8. |server_proof| contains the ECDSA signature and observed request
// hash, which is passed in the ETag HTTP header. Returns true if the response
// is valid and the observed request hash matches the sent hash. This method
// uses internal state that is set by a prior SignRequest() call.
bool ValidateResponse(const base::StringPiece& response_body,
const base::StringPiece& server_etag);
private:
friend class CupEcdsaTest;
Ecdsa(int key_version, const base::StringPiece& public_key);
// The server keeps multiple signing keys; a version must be sent so that
// the correct signing key is used to sign the assembled message.
const int pub_key_version_;
// The ECDSA public key to use for verifying response signatures.
const std::vector<uint8_t> public_key_;
// The SHA-256 hash of the XML request. This is modified on each call to
// SignRequest(), and checked by ValidateResponse().
std::vector<uint8_t> request_hash_;
// The query string containing key version and nonce in UTF-8 form. This is
// modified on each call to SignRequest(), and checked by ValidateResponse().
std::string request_query_cup2key_;
DISALLOW_IMPLICIT_CONSTRUCTORS(Ecdsa);
};
} // namespace client_update_protocol
#endif // COMPONENTS_CLIENT_UPDATE_PROTOCOL_ECDSA_H_
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