influxdb: provide influxdb-api, one mesh-made v1 credential per consumer

grafana's data source and Node-RED's influxdb nodes reached ace's
InfluxDB by a LAN IP or a public name nobody routes, with a credential
somebody made by hand. Now a consumer requires influxdb-api and is told
where it is, which org and default bucket it serves, and signs in with
the password the mesh minted for the pair.

The credential is a v1-compatibility authorization, made per grant by
the new provisioner: InfluxDB 2.x generates API tokens itself and
ignores one the caller sends, so a v2 token could only be accepted by
hand per pair; a v1 authorization takes a caller-chosen password (8-72
characters, the mesh mints 40) and reads/writes every bucket as a
database of its name over InfluxQL and line protocol. A consumer
contributes `access` (read, write, read-write) and, for writing, the
buckets; a missing bucket is made and never deleted. Only
authorizations named mesh_* and marked [mesh] are ever changed or
removed; anything else of that name is refused and left alone.

The org and default bucket are served facts the assignment's settings
set, reaching both the consumers and the provisioner's config.json.

modules/influxdb/grants.ts

@@ -0,0 +1,186 @@
+// What the `influxdb-api` provision means in InfluxDB: one v1-compatibility authorization per
+// consumer, in the org this module serves, under the username and password the mesh gave both ends,
+// allowed exactly the access the consumer contributed. The provisioner (provisioner/index.ts) is the
+// sdk harness calling these; they are here, apart from it, so they can be exercised against a fake
+// InfluxDB without a broker or a contributions file.
+//
+// **Why a v1 authorization and not a v2 API token.** The mesh mints the consumer's password and
+// hands it to both ends (novox/hq ADR 0048); the provider sets it, and never hands one back. An
+// InfluxDB 2.x API token is generated by the server — `POST /api/v2/authorizations` ignores a token
+// the caller sends — so a token could only ever be the operator's to accept, one per pair, by hand.
+// A v1 authorization is a username and a password the caller chooses (8–72 characters; the mesh
+// mints 40), stored hashed, and it reads and writes through InfluxQL (`/query`) and line protocol
+// (`/write`), which every bucket answers under its own name as a database (InfluxDB maps each
+// bucket to a database of the same name by itself). That is what grafana's InfluxDB data source
+// speaks, and what Node-RED's influxdb nodes speak in their 1.x mode — so the mesh can make every
+// consumer's credential, rotate it and withdraw it, with no person in the loop.
+//
+// **What a consumer contributes.** `access`: "read" (the default), "write" or "read-write".
+// `buckets`: the buckets it may use, by name. A reader that names none may read every bucket of the
+// org — a dashboard is pointed at data, it does not own it. A writer must name its buckets: writing
+// everywhere, the org's system buckets included, is never what a consumer means. A named bucket
+// that does not exist is created, keeping its data for ever; the mesh never deletes a bucket.
+//
+// **Only what the mesh made is touched.** An authorization this module creates is named with the
+// mesh's identity prefix and its description starts with MARK. One with the same username that
+// lacks the mark is somebody else's: it is refused, never adopted, never updated, never deleted.
+// Every other authorization, token, user and bucket in the instance is left exactly as it was.
+
+import type { InfluxDBClient, InfluxPermission, LegacyAuthorization } from "./client.js";
+
+/** How a description marks an authorization as the mesh's own work. */
+export const MARK = "[mesh]";
+
+/** The prefix the mesh gives every consumer identity (novox/hq ADR 0049). */
+const IDENTITY_PREFIX = "mesh_";
+
+/** One consumer, as the harness hands it over. */
+export interface ApiGrant {
+  readonly as: string;
+  readonly password: string;
+  readonly values: Readonly<Record<string, unknown>>;
+  readonly consumer?: string;
+}
+
+export type Access = "read" | "write" | "read-write";
+
+/** What a contribution asks for, checked. Refused when it cannot be served as asked. */
+export function askedFor(values: Readonly<Record<string, unknown>>): { access: Access; buckets: string[] } {
+  const access = values.access ?? "read";
+  if (access !== "read" && access !== "write" && access !== "read-write") {
+    throw new Error(`contributes an access of ${JSON.stringify(access)} — it is "read", "write" or "read-write"`);
+  }
+  const raw = values.buckets ?? [];
+  if (!Array.isArray(raw) || raw.some((b) => typeof b !== "string" || b.trim() === "")) {
+    throw new Error(`contributes buckets of ${JSON.stringify(raw)} — a list of bucket names`);
+  }
+  const buckets = [...new Set((raw as string[]).map((b) => b.trim()))].sort();
+  if (access !== "read" && buckets.length === 0) {
+    throw new Error(`asks to write and names no bucket (\`buckets\`) — a writer names what it writes to`);
+  }
+  if (buckets.some((b) => b.startsWith("_"))) {
+    throw new Error(`names a system bucket (${buckets.filter((b) => b.startsWith("_")).join(", ")}) — those are InfluxDB's own`);
+  }
+  return { access: access as Access, buckets };
+}
+
+/** The permissions a grant resolves to, given each named bucket's id. */
+export function permissionsFor(orgID: string, access: Access, bucketIDs: string[]): InfluxPermission[] {
+  const actions: ("read" | "write")[] = access === "read-write" ? ["read", "write"] : [access];
+  const out: InfluxPermission[] = [];
+  for (const action of actions) {
+    if (bucketIDs.length === 0) {
+      out.push({ action, resource: { type: "buckets", orgID } });
+      continue;
+    }
+    for (const id of bucketIDs) out.push({ action, resource: { type: "buckets", orgID, id } });
+  }
+  return out;
+}
+
+/** A permission as a comparable string: what InfluxDB answers carries names and links besides. */
+function key(p: InfluxPermission): string {
+  return `${p.action}:${p.resource.type}:${p.resource.orgID ?? ""}:${p.resource.id ?? "*"}`;
+}
+
+function samePermissions(a: readonly InfluxPermission[], b: readonly InfluxPermission[]): boolean {
+  const x = a.map(key).sort();
+  const y = b.map(key).sort();
+  return x.length === y.length && x.every((v, i) => v === y[i]);
+}
+
+export function marked(a: Pick<LegacyAuthorization, "token" | "description">): boolean {
+  return a.token.startsWith(IDENTITY_PREFIX) && (a.description ?? "").startsWith(MARK);
+}
+
+function describe(g: ApiGrant): string {
+  return `${MARK} made by the mesh for ${g.consumer ? `a module on ${g.consumer}` : "a consumer"} — do not edit; it is reset`;
+}
+
+export class ApiGrants {
+  constructor(private readonly influx: InfluxDBClient, readonly org: string) {}
+
+  private async orgID(): Promise<string> {
+    const id = await this.influx.orgID(this.org);
+    if (!id) throw new Error(`InfluxDB has no org ${JSON.stringify(this.org)} — the org this module serves must exist`);
+    return id;
+  }
+
+  /** The ids of the named buckets, creating any that are missing when `create` says so. Undefined
+   *  when one is missing and may not be created (a read-only question). */
+  private async bucketIDs(orgID: string, names: string[], create: ApiGrant | undefined): Promise<string[] | undefined> {
+    const ids: string[] = [];
+    for (const name of names) {
+      let b = await this.influx.findBucket(orgID, name);
+      if (!b) {
+        if (!create) return undefined;
+        b = await this.influx.createBucket(orgID, name, `${MARK} made by the mesh for ${create.as}; the mesh never deletes it`);
+      }
+      ids.push(b.id);
+    }
+    return ids.sort();
+  }
+
+  /** Create the consumer's authorization, or bring the mesh's existing one back to what the grant
+   *  says. Idempotent: a second apply of the same grant changes nothing beyond re-asserting the
+   *  password, which InfluxDB can be told but never asked. */
+  async ensure(g: ApiGrant): Promise<"created" | "updated" | "unchanged"> {
+    if (!g.as.startsWith(IDENTITY_PREFIX)) {
+      throw new Error(`${g.as} is not a mesh identity — the mesh names every consumer ${IDENTITY_PREFIX}<node>_<module>`);
+    }
+    const { access, buckets } = askedFor(g.values);
+    const orgID = await this.orgID();
+    const found = await this.influx.findLegacy(g.as);
+    if (found && !marked(found)) {
+      throw new Error(
+        `InfluxDB already has a v1 authorization ${g.as} the mesh did not make — left alone; ` +
+          `delete it if the mesh should own that name`);
+    }
+    const want = permissionsFor(orgID, access, (await this.bucketIDs(orgID, buckets, g))!);
+
+    if (found && found.orgID === orgID && samePermissions(found.permissions, want)) {
+      // Only what differs is written. The password cannot be read back, so it is tried instead.
+      let changed = false;
+      if (found.status === "inactive") {
+        await this.influx.updateLegacy(found.id, { status: "active" });
+        changed = true;
+      }
+      if (!(await this.influx.legacySignsIn(g.as, g.password))) {
+        await this.influx.setLegacyPassword(found.id, g.password);
+        changed = true;
+      }
+      return changed ? "updated" : "unchanged";
+    }
+    // InfluxDB cannot change an authorization's permissions in place, so the mesh's own is made
+    // again. Only ever one the mesh made: a foreign one was refused above.
+    if (found) await this.influx.deleteLegacy(found.id);
+    const made = await this.influx.createLegacy({
+      token: g.as, orgID, status: "active", description: describe(g), permissions: want,
+    });
+    await this.influx.setLegacyPassword(made.id, g.password);
+    return found ? "updated" : "created";
+  }
+
+  /** Whether InfluxDB still holds this consumer's authorization exactly as the grant says: present,
+   *  the mesh's, active, allowed what was asked and nothing more, and signing in with the mesh's
+   *  password. Reads only — a missing bucket is "not held", never created here. */
+  async holds(g: ApiGrant): Promise<boolean> {
+    const { access, buckets } = askedFor(g.values);
+    const orgID = await this.influx.orgID(this.org);
+    if (!orgID) return false;
+    const found = await this.influx.findLegacy(g.as);
+    if (!found || !marked(found) || found.status === "inactive" || found.orgID !== orgID) return false;
+    const ids = await this.bucketIDs(orgID, buckets, undefined);
+    if (!ids || !samePermissions(found.permissions, permissionsFor(orgID, access, ids))) return false;
+    return this.influx.legacySignsIn(g.as, g.password);
+  }
+
+  /** Withdraw a consumer's authorization — only one the mesh made. Its buckets and their data stay. */
+  async remove(as: string): Promise<"removed" | "absent" | "not ours"> {
+    const found = await this.influx.findLegacy(as);
+    if (!found) return "absent";
+    if (!marked(found)) return "not ours";
+    await this.influx.deleteLegacy(found.id);
+    return "removed";
+  }
+}