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A did method that uses at uri's to resolve a did document in a pds
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did-method-at resolver.ts
11 kB · 338 lines
TypeScript
at main
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const DEFAULT_MAX_RECURSION = 8const PLC_DIRECTORY = 'https://plc.directory'const SEP = '..'
export type AtPath = | { kind: 'record'; collection: string; rkey: string } | { kind: 'space' stype: string skey: string memberDid: string rtype: string rkey: string }
export interface ParsedDidAt { authority: string path: AtPath}
export interface ResolutionResult { didDocument: Record<string, unknown> didDocumentMetadata: { deactivated: boolean } didResolutionMetadata: { recursionRemaining: number }}
export class ResolutionError extends Error { constructor( public code: | 'invalidDid' | 'invalidDidDocument' | 'unsupportedAuthority' | 'notFound' | 'deactivated' | 'recursionLimitExceeded' | 'cycleDetected', message: string, ) { super(`${code}: ${message}`) }}
// ---------------------------------------------------------------- parsing
const NSID_RE = /^[a-zA-Z](?:[a-zA-Z0-9-]*)(?:\.[a-zA-Z0-9-]+)+\.[a-zA-Z](?:[a-zA-Z0-9]*)$/const HANDLE_RE = /^[a-zA-Z0-9](?:[a-zA-Z0-9-]*)(?:\.[a-zA-Z0-9-]+)+$/// Colons are fine (spec §3.5); "~" and ".." are unaddressable.const RKEY_RE = /^[a-zA-Z0-9._:-]{1,512}$/
const isNsid = (s: string) => NSID_RE.test(s) && s.split('.').length >= 3const isDid = (s: string) => /^did:[a-z]+:.+$/.test(s)const isHandle = (s: string) => HANDLE_RE.test(s)
const invalid = (msg: string) => new ResolutionError('invalidDid', msg)
/** Parse `did:at:<authority>..<path components>` (spec §3.3, left-to-right). */export function parseDidAt(did: string): ParsedDidAt { if (!did.startsWith('did:at:')) { throw invalid(`not a did:at DID: ${did}`) } const components = did.slice('did:at:'.length).split(SEP) for (const c of components) { if (!c || c.startsWith('.') || c.endsWith('.')) { throw invalid(`bad component ${JSON.stringify(c)} in ${did}`) } } const authority = parseDid(components, 0, did) const path = parsePath(components, authority.next, did) if (path.next !== components.length) { throw invalid(`trailing components in ${did}`) } return { authority: authority.did, path: path.path }}
/** * Rule: did-or-handle. A did:at consumes its own path from the following * components; other DIDs and handles are a single component. An embedded * did:at's authority chain lives entirely within component `i`; its path * components flatten into the list innermost-first (spec §3.3.2). */function parseDid( components: string[], i: number, full: string,): { did: string; next: number } { const c = components[i] if (c === undefined) throw invalid(`missing DID component in ${full}`) return parseDidFrom(c, components, i + 1, full)}
function parseDidFrom( authorityChain: string, components: string[], i: number, full: string,): { did: string; next: number } { if (authorityChain.startsWith('did:at:')) { const inner = parseDidFrom(authorityChain.slice('did:at:'.length), components, i, full) const { path, next } = parsePath(components, inner.next, full) return { did: `did:at:${inner.did}${SEP}${renderPath(path)}`, next } } if (isDid(authorityChain) || isHandle(authorityChain)) { return { did: authorityChain, next: i } } throw invalid(`invalid DID or handle: ${authorityChain}`)}
/** Rule: path — a repo record (collection, rkey) or a space record (§3.2). */function parsePath( components: string[], i: number, full: string,): { path: AtPath; next: number } { if (components[i] === 'space') { const stype = components[i + 1] const skey = components[i + 2] if (stype === undefined || skey === undefined) { throw invalid(`truncated space path in ${full}`) } if (!isNsid(stype)) throw invalid(`invalid space type NSID: ${stype}`) if (!RKEY_RE.test(skey)) throw invalid(`invalid space key: ${skey}`) const member = parseDid(components, i + 3, full) const rtype = components[member.next] const rkey = components[member.next + 1] if (rtype === undefined || rkey === undefined) { throw invalid(`truncated space path in ${full}`) } if (!isNsid(rtype)) throw invalid(`invalid record type NSID: ${rtype}`) if (!RKEY_RE.test(rkey)) throw invalid(`invalid rkey: ${rkey}`) return { path: { kind: 'space', stype, skey, memberDid: member.did, rtype, rkey }, next: member.next + 2, } }
const collection = components[i] const rkey = components[i + 1] if (collection === undefined || rkey === undefined) { throw invalid(`missing collection or rkey in ${full}`) } if (!isNsid(collection)) throw invalid(`invalid collection NSID: ${collection}`) if (!RKEY_RE.test(rkey)) throw invalid(`invalid rkey: ${rkey}`) return { path: { kind: 'record', collection, rkey }, next: i + 2 }}
function renderPath(path: AtPath): string { return path.kind === 'record' ? [path.collection, path.rkey].join(SEP) : ['space', path.stype, path.skey, path.memberDid, path.rtype, path.rkey].join(SEP)}
// ------------------------------------------------- resolving DIDs (§6)
async function getJson(url: string): Promise<any> { const res = await fetch(url, { headers: { accept: 'application/json' } }) if (res.status === 404 || res.status === 400) { throw new ResolutionError('notFound', url) } if (!res.ok) throw new Error(`${res.status} fetching ${url}`) return res.json()}
function pdsEndpoint(didDocument: any): string | undefined { const services: any[] = didDocument?.service ?? [] const pds = services.find( (s) => s.id === '#atproto_pds' || String(s.id).endsWith('#atproto_pds'), ) return pds?.serviceEndpoint}
/** Standard atproto handle resolution (HTTPS well-known; DNS omitted for brevity). */async function resolveHandle(handle: string): Promise<string> { const res = await fetch(`https://${handle}/.well-known/atproto-did`) if (!res.ok) throw new ResolutionError('notFound', `handle ${handle}`) const did = (await res.text()).trim() if (!isDid(did)) { throw new ResolutionError('invalidDidDocument', `handle ${handle} returned ${did}`) } return did}
/** Fetch the DID document for a did:plc or did:web (bare domain or path form). */async function resolveAtprotoDid(did: string): Promise<any> { if (did.startsWith('did:plc:')) { return getJson(`${PLC_DIRECTORY}/${did}`) } if (did.startsWith('did:web:')) { const parts = did.slice('did:web:'.length).split(':').map(decodeURIComponent) const url = parts.length === 1 ? `https://${parts[0]}/.well-known/did.json` : `https://${parts[0]}/${parts.slice(1).join('/')}/did.json` return getJson(url) } throw new ResolutionError('unsupportedAuthority', did)}
interface Repo { repoDid: string pdsUrl?: string}
/** Shared across a whole resolution chain: every did:at resolution, including * siblings (space authority and member), draws from the same count. */interface Budget { remaining: number}
/** * Resolve any DID or handle on the path to a concrete atproto identity. * A did:at recurses (consuming budget) and yields the repo named by its * document's at:// alsoKnownAs alias (spec §6). */async function resolveDid( identifier: string, budget: Budget, seen: Set<string>,): Promise<Repo> { if (!identifier.startsWith('did:') && isHandle(identifier)) { identifier = await resolveHandle(identifier) }
if (identifier.startsWith('did:at:')) { const { didDocument } = await resolveDidAt(identifier, { budget, seen }) const alias = (didDocument.alsoKnownAs as string[] | undefined)?.find((a) => a.startsWith('at://did:'), ) if (!alias) { throw new ResolutionError( 'invalidDidDocument', `${identifier}: no at://<did> alsoKnownAs entry to locate its repo`, ) } const repoDid = alias.slice('at://'.length).split('/')[0] const pdsUrl = pdsEndpoint(didDocument) ?? pdsEndpoint(await resolveAtprotoDid(repoDid)) return { repoDid, pdsUrl } }
const doc = await resolveAtprotoDid(identifier) return { repoDid: identifier, pdsUrl: pdsEndpoint(doc) }}
// --------------------------------------------------------- resolution (§7)
export async function resolveDidAt( did: string, opts: { maxRecursion?: number; seen?: Set<string>; budget?: Budget } = {},): Promise<ResolutionResult> { const budget = opts.budget ?? { remaining: opts.maxRecursion ?? DEFAULT_MAX_RECURSION, } const seen = opts.seen ?? new Set<string>()
if (budget.remaining <= 0) { throw new ResolutionError('recursionLimitExceeded', did) } budget.remaining -= 1 if (seen.has(did)) { throw new ResolutionError('cycleDetected', did) } seen.add(did)
const { authority, path } = parseDidAt(did) const { repoDid, pdsUrl } = await resolveDid(authority, budget, seen) if (!pdsUrl) { throw new ResolutionError('invalidDidDocument', `${authority}: no #atproto_pds service`) } const xrpc = pdsUrl.replace(/\/$/, '') + '/xrpc'
let record: any if (path.kind === 'record') { record = await getJson( `${xrpc}/com.atproto.repo.getRecord` + `?repo=${encodeURIComponent(repoDid)}` + `&collection=${encodeURIComponent(path.collection)}` + `&rkey=${encodeURIComponent(path.rkey)}`, ) } else { // Space record (spec §7.5b). Endpoint name provisional per the Spaces // proposal. A did:at member resolves to its repo DID first. const member = await resolveDid(path.memberDid, budget, seen) const spaceUri = `at://${repoDid}/space/${path.stype}/${path.skey}` record = await getJson( `${xrpc}/com.atproto.space.getRecord` + `?space=${encodeURIComponent(spaceUri)}` + `&repo=${encodeURIComponent(member.repoDid)}` + `&collection=${encodeURIComponent(path.rtype)}` + `&rkey=${encodeURIComponent(path.rkey)}`, ) }
const value = record.value ?? {} if (value.deactivated === true) { throw new ResolutionError('deactivated', did) } const didDocument = value.didDocument if (typeof didDocument !== 'object' || didDocument === null) { throw new ResolutionError('invalidDidDocument', `${did}: record has no didDocument`) } if (didDocument.id !== did) { throw new ResolutionError( 'invalidDidDocument', `${did}: document id is ${didDocument.id} (spec §4.1 requires exact match)`, ) }
return { didDocument, didDocumentMetadata: { deactivated: false }, didResolutionMetadata: { recursionRemaining: budget.remaining }, }}
// ------------------------------------------------------------------- CLI
const invokedDirectly = typeof process !== 'undefined' && process.argv[1]?.endsWith('/resolver.ts')
if (invokedDirectly) { const [did, max] = process.argv.slice(2) if (!did) { console.error('usage: npx tsx resolver.ts <did:at:...> [maxRecursion]') process.exit(2) } resolveDidAt(did, { maxRecursion: max ? Number(max) : undefined }) .then((result) => console.log(JSON.stringify(result, null, 2))) .catch((err) => { console.error(err.message) process.exit(1) })}