anastasis-core: maximize diversity in provider selection
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@ -90,6 +90,7 @@ import {
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} from "./crypto.js";
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import { unzlibSync, zlibSync } from "fflate";
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import { EscrowMethod, RecoveryDocument } from "./recovery-document-types.js";
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import { ProviderInfo, suggestPolicies } from "./policy-suggestion.js";
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const { fetch } = fetchPonyfill({});
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@ -290,109 +291,6 @@ async function backupEnterUserAttributes(
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return newState;
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}
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interface PolicySelectionResult {
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policies: Policy[];
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policy_providers: PolicyProvider[];
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}
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type MethodSelection = number[];
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function enumerateSelections(n: number, m: number): MethodSelection[] {
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const selections: MethodSelection[] = [];
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const a = new Array(n);
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const sel = (i: number) => {
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if (i === n) {
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selections.push([...a]);
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return;
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}
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const start = i == 0 ? 0 : a[i - 1] + 1;
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for (let j = start; j < m; j++) {
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a[i] = j;
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sel(i + 1);
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}
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};
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sel(0);
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return selections;
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}
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/**
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* Provider information used during provider/method mapping.
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*/
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interface ProviderInfo {
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url: string;
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methodCost: Record<string, AmountString>;
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}
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/**
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* Assign providers to a method selection.
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*/
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function assignProviders(
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methods: AuthMethod[],
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providers: ProviderInfo[],
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methodSelection: number[],
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): Policy | undefined {
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const selectedProviders: string[] = [];
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for (const mi of methodSelection) {
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const m = methods[mi];
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let found = false;
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for (const prov of providers) {
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if (prov.methodCost[m.type]) {
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selectedProviders.push(prov.url);
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found = true;
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break;
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}
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}
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if (!found) {
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/* No provider found for this method */
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return undefined;
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}
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}
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return {
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methods: methodSelection.map((x, i) => {
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return {
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authentication_method: x,
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provider: selectedProviders[i],
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};
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}),
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};
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}
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function suggestPolicies(
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methods: AuthMethod[],
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providers: ProviderInfo[],
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): PolicySelectionResult {
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const numMethods = methods.length;
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if (numMethods === 0) {
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throw Error("no methods");
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}
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let numSel: number;
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if (numMethods <= 2) {
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numSel = numMethods;
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} else if (numMethods <= 4) {
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numSel = numMethods - 1;
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} else if (numMethods <= 6) {
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numSel = numMethods - 2;
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} else if (numMethods == 7) {
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numSel = numMethods - 3;
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} else {
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numSel = 4;
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}
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const policies: Policy[] = [];
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const selections = enumerateSelections(numSel, numMethods);
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logger.info(`selections: ${j2s(selections)}`);
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for (const sel of selections) {
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const p = assignProviders(methods, providers, sel);
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if (p) {
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policies.push(p);
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}
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}
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return {
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policies,
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policy_providers: providers.map((x) => ({
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provider_url: x.url,
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})),
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};
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}
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/**
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* Truth data as stored in the reducer.
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169
packages/anastasis-core/src/policy-suggestion.ts
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169
packages/anastasis-core/src/policy-suggestion.ts
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@ -0,0 +1,169 @@
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import { AmountString, j2s, Logger } from "@gnu-taler/taler-util";
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import { AuthMethod, Policy, PolicyProvider } from "./reducer-types.js";
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const logger = new Logger("anastasis-core:policy-suggestion.ts");
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/**
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* Provider information used during provider/method mapping.
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*/
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export interface ProviderInfo {
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url: string;
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methodCost: Record<string, AmountString>;
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}
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export function suggestPolicies(
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methods: AuthMethod[],
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providers: ProviderInfo[],
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): PolicySelectionResult {
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const numMethods = methods.length;
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if (numMethods === 0) {
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throw Error("no methods");
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}
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let numSel: number;
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if (numMethods <= 2) {
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numSel = numMethods;
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} else if (numMethods <= 4) {
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numSel = numMethods - 1;
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} else if (numMethods <= 6) {
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numSel = numMethods - 2;
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} else if (numMethods == 7) {
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numSel = numMethods - 3;
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} else {
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numSel = 4;
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}
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const policies: Policy[] = [];
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const selections = enumerateMethodSelections(numSel, numMethods);
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logger.info(`selections: ${j2s(selections)}`);
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for (const sel of selections) {
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const p = assignProviders(policies, methods, providers, sel);
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if (p) {
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policies.push(p);
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}
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}
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return {
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policies,
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policy_providers: providers.map((x) => ({
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provider_url: x.url,
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})),
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};
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}
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/**
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* Assign providers to a method selection.
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*
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* The evaluation of the assignment is made with respect to
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* previously generated policies.
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*/
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function assignProviders(
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existingPolicies: Policy[],
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methods: AuthMethod[],
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providers: ProviderInfo[],
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methodSelection: number[],
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): Policy | undefined {
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const providerSelections = enumerateProviderMappings(
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methodSelection.length,
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providers.length,
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);
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let bestProvSel: ProviderSelection | undefined;
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let bestDiversity = 0;
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for (const provSel of providerSelections) {
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// First, check if selection is even possible with the methods offered
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let possible = true;
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for (const methIndex in provSel) {
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const provIndex = provSel[methIndex];
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const meth = methods[methIndex];
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const prov = providers[provIndex];
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if (!prov.methodCost[meth.type]) {
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possible = false;
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break;
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}
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}
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if (!possible) {
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continue;
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}
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// Evaluate diversity, always prefer policies
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// that increase diversity.
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const providerSet = new Set<string>();
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for (const pol of existingPolicies) {
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for (const m of pol.methods) {
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providerSet.add(m.provider);
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}
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}
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for (const provIndex of provSel) {
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const prov = providers[provIndex];
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providerSet.add(prov.url);
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}
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const diversity = providerSet.size;
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if (!bestProvSel || diversity > bestDiversity) {
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bestProvSel = provSel;
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bestDiversity = diversity;
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}
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// TODO: also evaluate costs and duplicates (same challenge at same provider)
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}
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if (!bestProvSel) {
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return undefined;
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}
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return {
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methods: bestProvSel.map((x, i) => ({
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authentication_method: methodSelection[i],
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provider: providers[x].url,
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})),
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};
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}
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type ProviderSelection = number[];
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/**
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* Compute provider mappings.
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* Enumerates all n-combinations with repetition of m providers.
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*/
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function enumerateProviderMappings(n: number, m: number): ProviderSelection[] {
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const selections: ProviderSelection[] = [];
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const a = new Array(n);
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const sel = (i: number, start: number = 0) => {
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if (i === n) {
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selections.push([...a]);
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return;
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}
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for (let j = start; j < m; j++) {
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a[i] = j;
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sel(i + 1, j);
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}
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};
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sel(0);
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return selections;
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}
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interface PolicySelectionResult {
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policies: Policy[];
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policy_providers: PolicyProvider[];
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}
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type MethodSelection = number[];
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/**
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* Compute method selections.
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* Enumerates all n-combinations without repetition of m methods.
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*/
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function enumerateMethodSelections(n: number, m: number): MethodSelection[] {
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const selections: MethodSelection[] = [];
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const a = new Array(n);
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const sel = (i: number, start: number = 0) => {
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if (i === n) {
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selections.push([...a]);
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return;
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}
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for (let j = start; j < m; j++) {
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a[i] = j;
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sel(i + 1, j + 1);
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}
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};
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sel(0);
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return selections;
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}
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