使用临时凭据对 R2 进行身份验证

import { SignJWT } from "jose";

type R2Scope =
  | "object-read-only"
  | "object-read-write"
  | "admin-read-only"
  | "admin-read-write";

export interface TempCredentialOptions {
  scope: R2Scope;
  // Optional: narrow the credential to specific S3 operations.
  actions?: string[];
  // Time-to-live in seconds. Defaults to 1 hour.
  ttlSeconds?: number;
  // Optional: restrict access to specific prefixes or objects.
  paths?: { prefixPaths?: string[]; objectPaths?: string[] };
}

export async function createTempCredentials(
  endpoint: string,
  accountId: string,
  parentAccessKeyId: string,
  parentSecretAccessKey: string,
  bucket: string,
  opts: TempCredentialOptions,
): Promise<{
  accessKeyId: string;
  secretAccessKey: string;
  sessionToken: string;
}> {
  const ttl = opts.ttlSeconds ?? 3600;

  const claims: Record<string, unknown> = {
    bucket,
    scope: opts.scope,
  };

  if (opts.actions !== undefined && opts.actions.length > 0) {
    claims.actions = opts.actions;
  }

  if (opts.paths !== undefined) {
    claims.paths = {
      prefixPaths: opts.paths.prefixPaths ?? [],
      objectPaths: opts.paths.objectPaths ?? [],
    };
  }

  // Sign the JWT with the parent secret access key. R2 validates this signature.
  const jwt = await new SignJWT(claims)
    .setProtectedHeader({ alg: "HS256", typ: "JWT" })
    .setSubject(accountId)
    .setIssuer(parentAccessKeyId)
    .setAudience(new URL(endpoint).host)
    .setIssuedAt()
    .setExpirationTime(`${ttl}s`)
    .sign(new TextEncoder().encode(parentSecretAccessKey));

  // The temporary secret access key is the SHA-256 hex digest of the signed JWT.
  const digest = await crypto.subtle.digest(
    "SHA-256",
    new TextEncoder().encode(jwt),
  );
  const secretAccessKey = Array.from(new Uint8Array(digest))
    .map((b) => b.toString(16).padStart(2, "0"))
    .join("");

  return {
    // Reuse the parent access key ID as the temporary access key ID.
    accessKeyId: parentAccessKeyId,
    secretAccessKey,
    // The session token is base64("jwt/" + signed JWT).
    sessionToken: btoa(`jwt/${jwt}`),
  };
}