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/*
This file is part of GNU Taler
(C) 2021 Taler Systems S.A.
GNU Taler is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.
GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
GNU Taler; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
*/
import { canonicalJson, Logger } from "@gnu-taler/taler-util";
import { kdf } from "@gnu-taler/taler-util";
import {
decodeCrock,
encodeCrock,
getRandomBytes,
hash,
stringToBytes,
} from "@gnu-taler/taler-util";
const logger = new Logger("contractTerms.ts");
export namespace ContractTermsUtil {
export type PathPredicate = (path: string[]) => boolean;
/**
* Scrub all forgettable members from an object.
*/
export function scrub(anyJson: any): any {
return forgetAllImpl(anyJson, [], () => true);
}
/**
* Recursively forget all forgettable members of an object,
* where the path matches a predicate.
*/
export function forgetAll(anyJson: any, pred: PathPredicate): any {
return forgetAllImpl(anyJson, [], pred);
}
function forgetAllImpl(
anyJson: any,
path: string[],
pred: PathPredicate,
): any {
const dup = JSON.parse(JSON.stringify(anyJson));
if (Array.isArray(dup)) {
for (let i = 0; i < dup.length; i++) {
dup[i] = forgetAllImpl(dup[i], [...path, `${i}`], pred);
}
} else if (typeof dup === "object" && dup != null) {
if (typeof dup.$forgettable === "object") {
for (const x of Object.keys(dup.$forgettable)) {
if (!pred([...path, x])) {
continue;
}
if (!dup.$forgotten) {
dup.$forgotten = {};
}
if (!dup.$forgotten[x]) {
const membValCanon = stringToBytes(
canonicalJson(scrub(dup[x])) + "\0",
);
const membSalt = stringToBytes(dup.$forgettable[x] + "\0");
const h = kdf(64, membValCanon, membSalt, new Uint8Array([]));
dup.$forgotten[x] = encodeCrock(h);
}
delete dup[x];
delete dup.$forgettable[x];
}
if (Object.keys(dup.$forgettable).length === 0) {
delete dup.$forgettable;
}
}
for (const x of Object.keys(dup)) {
if (x.startsWith("$")) {
continue;
}
dup[x] = forgetAllImpl(dup[x], [...path, x], pred);
}
}
return dup;
}
/**
* Generate a salt for all members marked as forgettable,
* but which don't have an actual salt yet.
*/
export function saltForgettable(anyJson: any): any {
const dup = JSON.parse(JSON.stringify(anyJson));
if (Array.isArray(dup)) {
for (let i = 0; i < dup.length; i++) {
dup[i] = saltForgettable(dup[i]);
}
} else if (typeof dup === "object" && dup !== null) {
if (typeof dup.$forgettable === "object") {
for (const k of Object.keys(dup.$forgettable)) {
if (dup.$forgettable[k] === true) {
dup.$forgettable[k] = encodeCrock(getRandomBytes(32));
}
}
}
for (const x of Object.keys(dup)) {
if (x.startsWith("$")) {
continue;
}
dup[x] = saltForgettable(dup[x]);
}
}
return dup;
}
const nameRegex = /^[0-9A-Za-z_]+$/;
/**
* Check that the given JSON object is well-formed with regards
* to forgettable fields and other restrictions for forgettable JSON.
*/
export function validateForgettable(anyJson: any): boolean {
if (typeof anyJson === "string") {
return true;
}
if (typeof anyJson === "number") {
return (
Number.isInteger(anyJson) &&
anyJson >= Number.MIN_SAFE_INTEGER &&
anyJson <= Number.MAX_SAFE_INTEGER
);
}
if (typeof anyJson === "boolean") {
return true;
}
if (anyJson === null) {
return true;
}
if (Array.isArray(anyJson)) {
return anyJson.every((x) => validateForgettable(x));
}
if (typeof anyJson === "object") {
for (const k of Object.keys(anyJson)) {
if (k.match(nameRegex)) {
if (validateForgettable(anyJson[k])) {
continue;
} else {
return false;
}
}
if (k === "$forgettable") {
const fga = anyJson.$forgettable;
if (!fga || typeof fga !== "object") {
return false;
}
for (const fk of Object.keys(fga)) {
if (!fk.match(nameRegex)) {
return false;
}
if (!(fk in anyJson)) {
return false;
}
const fv = anyJson.$forgettable[fk];
if (typeof fv !== "string") {
return false;
}
}
} else if (k === "$forgotten") {
const fgo = anyJson.$forgotten;
if (!fgo || typeof fgo !== "object") {
return false;
}
for (const fk of Object.keys(fgo)) {
if (!fk.match(nameRegex)) {
return false;
}
// Check that the value has actually been forgotten.
if (fk in anyJson) {
return false;
}
const fv = anyJson.$forgotten[fk];
if (typeof fv !== "string") {
return false;
}
try {
const decFv = decodeCrock(fv);
if (decFv.length != 64) {
return false;
}
} catch (e) {
return false;
}
// Check that salt has been deleted after forgetting.
if (anyJson.$forgettable?.[k] !== undefined) {
return false;
}
}
} else {
return false;
}
}
return true;
}
return false;
}
/**
* Check that no forgettable information has been forgotten.
*
* Must only be called on an object already validated with validateForgettable.
*/
export function validateNothingForgotten(contractTerms: any): boolean {
throw Error("not implemented yet");
}
/**
* Hash a contract terms object. Forgettable fields
* are scrubbed and JSON canonicalization is applied
* before hashing.
*/
export function hashContractTerms(contractTerms: unknown): string {
const cleaned = scrub(contractTerms);
const canon = canonicalJson(cleaned) + "\0";
const bytes = stringToBytes(canon);
logger.info(`contract terms before hashing: ${encodeCrock(bytes)}`);
return encodeCrock(hash(bytes));
}
}
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