// 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 #include #include #include #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() = 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. // Returns a NULL pointer on failure. static std::unique_ptr 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); // 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(const base::StringPiece& 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(const base::StringPiece& response_body, const base::StringPiece& 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: 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 public_key_; // The SHA-256 hash of the XML request. This is modified on each call to // SignRequest(), and checked by ValidateResponse(). std::vector 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_