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// Copyright 2016 The Chromium Authors
// 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 <array>
#include <cstdint>
#include <memory>
#include <string>
#include <string_view>
#include <vector>
#include "crypto/hash.h"
#include "crypto/keypair.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() = delete;
Ecdsa(const Ecdsa&) = delete;
Ecdsa& operator=(const Ecdsa&) = delete;
~Ecdsa();
struct RequestParameters {
std::string query_cup2key;
std::string hash_hex;
};
// 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.
Ecdsa(int key_version, base::span<const uint8_t> 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(std::string_view request_body, std::string* query_params);
// Generates freshness/authentication data for an outgoing ping.
// |request_body| contains the body of the ping in UTF-8. Returns the
// parameters that must be sent to the server for ECDSA authentication.
//
// 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.
RequestParameters SignRequest(std::string_view request_body);
// Validates a response given to a ping previously signed with
// SignRequest(). |response_body| contains the body of the response in
// UTF-8. |signature| contains the ECDSA signature and observed request
// hash. 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(std::string_view response_body,
std::string_view signature);
// Sets the key and nonce that were used to generate a signature that is baked
// into a unit test. Note this function encodes |nonce| in decimal, while
// non-test paths use a base64url-encoded, 256-bit string.
void OverrideNonceForTesting(int key_version, uint32_t nonce);
private:
// 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 crypto::keypair::PublicKey public_key_;
// The SHA-256 hash of the XML request. This is modified on each call to
// SignRequest(), and checked by ValidateResponse().
std::array<uint8_t, crypto::hash::kSha256Size> 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_;
};
} // namespace client_update_protocol
#endif // COMPONENTS_CLIENT_UPDATE_PROTOCOL_ECDSA_H_
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