JavaScriptSolidServer/src/wac/checker.js at gh-pages · JavaScriptSolidServer/JavaScriptSolidServer · GitHub

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/**

* WAC (Web Access Control) Checker

* Checks if an agent has permission to access a resource

import * as storage from '../storage/filesystem.js';

import { parseAcl, AccessMode, AgentClass } from './parser.js';

import { getAclUrl } from '../ldp/headers.js';

import { readLedger, getBalance, debit } from '../webledger.js';

/**

* Check if agent has required access mode for resource

* @param {object} options

* @param {string} options.resourceUrl - Full URL of the resource

* @param {string} options.resourcePath - Path portion of the resource URL

* @param {boolean} options.isContainer - Whether resource is a container

* @param {string|null} options.agentWebId - WebID of the agent (null for unauthenticated)

* @param {string} options.requiredMode - Required access mode (from AccessMode)

* @param {boolean} [options.noDebit=false] - When true, evaluate a

* PaymentCondition without charging the ledger. A positive-cost paid grant

* is treated as not-satisfied (returns paymentRequired) rather than debited.

* Used by secondary/guard checks (e.g. the POST sidecar Control gate in

* handlePost) so a single request cannot debit twice or charge silently;

* the authoritative debit stays in the primary authorize() hook.

* @returns {Promise<{

* allowed: boolean,

* wacAllow: string,

* paymentRequired?: object|null,

* paid?: number,

* balance?: number,

* currency?: string

* }>}

* `paymentRequired` carries the unmet PaymentCondition (present when a paid

* grant is denied, including every `noDebit` denial). `paid`/`balance`/

* `currency` are set only when a debit actually occurred. The no-ACL deny

* path returns just `{allowed, wacAllow}`.

export async function checkAccess({

resourceUrl,

resourcePath,

isContainer,

agentWebId,

requiredMode,

noDebit = false

}) {

// Find applicable ACL

const aclResult = await findApplicableAcl(resourceUrl, resourcePath, isContainer);

if (!aclResult) {

// No ACL found - deny by default (restrictive mode)

// Security: Require explicit ACL for any access

return { allowed: false, wacAllow: 'user="", public=""' };

}

const { authorizations, isDefault, targetUrl: aclContainerUrl } = aclResult;

// Check authorizations

// Note: For default ACLs, we check if the ACL's default rules apply to the actual resource URL

const result = await checkAuthorizations(

authorizations,

resourceUrl, // Use actual resource URL, not the ACL container URL

agentWebId,

requiredMode,

isDefault,

noDebit

);

// Calculate WAC-Allow header

const wacAllow = calculateWacAllow(authorizations, resourceUrl, agentWebId, isDefault);

return { allowed: result.allowed, wacAllow, paymentRequired: result.paymentRequired || null, paid: result.paid, balance: result.balance, currency: result.currency };

}

/**

* Find the applicable ACL for a resource

* Walks up the path hierarchy looking for .acl files

async function findApplicableAcl(resourceUrl, resourcePath, isContainer) {

// First check for resource-specific ACL

const resourceAclPath = isContainer

? (resourcePath.endsWith('/') ? resourcePath : resourcePath + '/') + '.acl'

: resourcePath + '.acl';

if (await storage.exists(resourceAclPath)) {

const content = await storage.read(resourceAclPath);

if (content) {

const aclUrl = getAclUrl(resourceUrl, isContainer);

const authorizations = await parseAcl(content.toString(), aclUrl);

return { authorizations, isDefault: false, targetUrl: resourceUrl };

}

// Walk up the hierarchy looking for default ACLs

// Track both storage path (for file lookup) and URL path (for URL construction)

let currentStoragePath = resourcePath;

let currentUrlPath = new URL(resourceUrl).pathname;

while (currentStoragePath && currentStoragePath !== '/') {

// Get parent container

const parentStoragePath = getParentPath(currentStoragePath);

const parentAclPath = parentStoragePath + '.acl';

if (await storage.exists(parentAclPath)) {

const content = await storage.read(parentAclPath);

if (content) {

// Get parent URL path and construct full URL

const parentUrlPath = getParentPath(currentUrlPath);

const origin = resourceUrl.substring(0, resourceUrl.indexOf('/', 8));

const parentUrl = origin + parentUrlPath;

const parentAclUrl = getAclUrl(parentUrl, true); // Container ACL URL

const authorizations = await parseAcl(content.toString(), parentAclUrl);

return { authorizations, isDefault: true, targetUrl: parentUrl };

}

currentStoragePath = parentStoragePath;

currentUrlPath = getParentPath(currentUrlPath);

}

// Check root ACL

if (await storage.exists('/.acl')) {

const content = await storage.read('/.acl');

if (content) {

const rootUrl = resourceUrl.substring(0, resourceUrl.indexOf('/', 8) + 1);

const rootAclUrl = getAclUrl(rootUrl, true); // Root container ACL URL

const authorizations = await parseAcl(content.toString(), rootAclUrl);

return { authorizations, isDefault: true, targetUrl: rootUrl };

}

return null;

}

/**

* Get parent container path

function getParentPath(path) {

// Remove trailing slash

const normalized = path.endsWith('/') ? path.slice(0, -1) : path;

const lastSlash = normalized.lastIndexOf('/');

if (lastSlash <= 0) return '/';

return normalized.substring(0, lastSlash + 1);

}

/**

* Check if any authorization grants the required mode

// Supported condition types

const SUPPORTED_CONDITIONS = ['PaymentCondition', 'https://webacl.org/ns#PaymentCondition'];

async function checkAuthorizations(authorizations, targetUrl, agentWebId, requiredMode, isDefault, noDebit = false) {

for (const auth of authorizations) {

// For default ACLs, check if auth has default rules and matches target

// For direct ACLs, check if accessTo matches target

if (isDefault) {

// Skip if no default rules defined

if (auth.default.length === 0) continue;

// Skip if target URL doesn't match any default URL prefix

if (!auth.default.some(d => urlMatches(d, targetUrl, true))) continue;

} else {

// Skip if accessTo doesn't match target

if (!auth.accessTo.some(a => urlMatches(a, targetUrl))) continue;

}

// Check if agent is authorized

const agentAuthorized = isAgentAuthorized(auth, agentWebId);

if (!agentAuthorized) continue;

// Check if mode is granted

const modeGranted = auth.modes.includes(requiredMode) ||

(requiredMode === AccessMode.APPEND && auth.modes.includes(AccessMode.WRITE));

if (!modeGranted) continue;

// Check conditions (fail-closed)

if (auth.conditions && auth.conditions.length > 0) {

// Fail-closed: skip this auth if any condition type is unsupported

const unsupported = auth.conditions.find(c => !SUPPORTED_CONDITIONS.includes(c.type));

if (unsupported) continue;

// Check payment condition

const paymentCondition = auth.conditions.find(c =>

c.type === 'PaymentCondition' || c.type === 'https://webacl.org/ns#PaymentCondition'

);

if (paymentCondition) {

const parsed = parseInt(paymentCondition.amount, 10);

const cost = Number.isNaN(parsed) ? -1 : parsed;

const currency = paymentCondition.currency || 'sat';

// Skip invalid amounts

if (cost < 0) continue;

if (agentWebId) {

try {

const ledger = await readLedger();

// Zero-cost gate: verify they have a ledger entry (have deposited at some point)

if (cost === 0) {

const hasEntry = ledger.entries?.some(e => e.url === agentWebId);

if (hasEntry) return { allowed: true };

}

// Paid access: check balance and deduct

const balance = getBalance(ledger, agentWebId, currency);

if (cost > 0 && balance >= cost) {

// Guard checks must not charge: a paid grant is left unsatisfied

// here so billing happens once, in the primary authorize() path.

if (noDebit) {

return { allowed: false, paymentRequired: paymentCondition };

}

const result = debit(ledger, agentWebId, cost, currency);

const { writeLedger } = await import('../webledger.js');

await writeLedger(ledger);

return { allowed: true, paid: cost, balance: result.balance, currency };

}

} catch (e) {

// Ledger read failed — fall through to payment required

}

return { allowed: false, paymentRequired: paymentCondition };

}

return { allowed: true };

}

return { allowed: false };

}

/**

* Check if the agent is authorized by an authorization rule

function isAgentAuthorized(auth, agentWebId) {

// Check specific agent

if (agentWebId && auth.agents.includes(agentWebId)) {

return true;

}

// Check agent classes

for (const agentClass of auth.agentClasses) {

// foaf:Agent - everyone (including unauthenticated)

if (agentClass === AgentClass.AGENT || agentClass === 'foaf:Agent') {

return true;

}

// acl:AuthenticatedAgent - any authenticated user

if (agentWebId && (agentClass === AgentClass.AUTHENTICATED || agentClass === 'acl:AuthenticatedAgent')) {

return true;

}

// TODO: Check agent groups (requires fetching and parsing group documents)

return false;

}

/**

* Check if URLs match (handles trailing slashes)

* @param {string} pattern - The ACL URL pattern

* @param {string} url - The target URL to check

* @param {boolean} prefixMatch - If true, check if url starts with pattern (for acl:default)

function urlMatches(pattern, url, prefixMatch = false) {

const normalizedPattern = pattern.replace(/\/$/, '');

const normalizedUrl = url.replace(/\/$/, '');

if (prefixMatch) {

// For default ACLs: target must be same as or under the pattern

return normalizedUrl === normalizedPattern ||

normalizedUrl.startsWith(normalizedPattern + '/');

}

return normalizedPattern === normalizedUrl;

}

/**

* Calculate WAC-Allow header value

function calculateWacAllow(authorizations, targetUrl, agentWebId, isDefault) {

const userModes = new Set();

const publicModes = new Set();

for (const auth of authorizations) {

// Check if applies to resource - use same logic as checkAuthorizations

if (isDefault) {

if (auth.default.length === 0) continue;

if (!auth.default.some(d => urlMatches(d, targetUrl, true))) continue;

} else {

if (!auth.accessTo.some(a => urlMatches(a, targetUrl))) continue;

}

// Check what modes this grants

const modes = auth.modes.map(m => {

if (m === AccessMode.READ || m === 'acl:Read') return 'read';

if (m === AccessMode.WRITE || m === 'acl:Write') return 'write';

if (m === AccessMode.APPEND || m === 'acl:Append') return 'append';

if (m === AccessMode.CONTROL || m === 'acl:Control') return 'control';

return null;

}).filter(Boolean);

// Check if public

const isPublic = auth.agentClasses.some(c =>

c === AgentClass.AGENT || c === 'foaf:Agent'

);

if (isPublic) {

modes.forEach(m => publicModes.add(m));

}

// Check if user-specific

if (agentWebId && auth.agents.includes(agentWebId)) {

modes.forEach(m => userModes.add(m));

}

// Check authenticated class

if (agentWebId && auth.agentClasses.some(c =>

c === AgentClass.AUTHENTICATED || c === 'acl:AuthenticatedAgent'

)) {

modes.forEach(m => userModes.add(m));

}

// User also gets public modes

publicModes.forEach(m => userModes.add(m));

const userStr = Array.from(userModes).join(' ');

const publicStr = Array.from(publicModes).join(' ');

return `user="${userStr}", public="${publicStr}"`;

}

/**

* Get the required access mode for an HTTP method

* @param {string} method - HTTP method

* @returns {string} Access mode

export function getRequiredMode(method) {

switch (method.toUpperCase()) {

case 'GET':

case 'HEAD':

case 'OPTIONS':

return AccessMode.READ;

case 'POST':

return AccessMode.APPEND;

case 'PUT':

case 'PATCH':

case 'DELETE':

return AccessMode.WRITE;

default:

return AccessMode.READ;

}

JavaScriptSolidServer/src/wac/checker.js at gh-pages · JavaScriptSolidServer/JavaScriptSolidServer · GitHub

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