logicsrc/packages/opencontext/src/adapters/http.ts
RissRIce edf9a1b063
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Enforce OpenContext HTTP byte limit while streaming (#136)
2026-08-09 21:57:05 -07:00

110 lines
3.6 KiB
TypeScript

/**
* `http://` and `https://` adapter.
*
* Remote content is data, never instruction. Whatever comes back is marked
* untrusted unless the object declares a digest that matches, in which case it
* is `verified` — integrity is a claim about bytes, not about intent, so even a
* digest-matched document never becomes `trusted`.
*/
import type { Adapter, AdapterContext, AdapterResult } from "../types.js";
import { sha256Uri } from "../digest.js";
export class OfflineError extends Error {
constructor(uri: string) {
super(`Cannot fetch ${uri} in --offline mode. Run without --offline, or inline the content.`);
this.name = "OfflineError";
}
}
const DEFAULT_TIMEOUT_MS = 10_000;
const MAX_BYTES = 5 * 1024 * 1024;
async function readBody(response: Response, uri: string): Promise<string> {
if (!response.body) return "";
const reader = response.body.getReader();
const chunks: Uint8Array[] = [];
let totalBytes = 0;
try {
while (true) {
const { done, value } = await reader.read();
if (done) break;
totalBytes += value.byteLength;
if (totalBytes > MAX_BYTES) {
await reader.cancel().catch(() => undefined);
throw new Error(`Refusing to load ${uri}: response exceeds the ${MAX_BYTES} byte limit.`);
}
chunks.push(value);
}
} finally {
reader.releaseLock();
}
const bytes = new Uint8Array(totalBytes);
let offset = 0;
for (const chunk of chunks) {
bytes.set(chunk, offset);
offset += chunk.byteLength;
}
return new TextDecoder().decode(bytes);
}
export const httpAdapter: Adapter = {
name: "http",
schemes: ["http", "https"],
remote: true,
async load(uri: string, ctx: AdapterContext): Promise<AdapterResult> {
if (ctx.offline) throw new OfflineError(uri);
const url = new URL(uri);
if (url.protocol === "http:" && ctx.config.allow_insecure !== true) {
throw new Error(
`Refusing to fetch ${uri} over plaintext http. Use https, or set adapters.http.allow_insecure: true ` +
`if this is a trusted network you control.`
);
}
const timeoutMs = ctx.timeoutMs ?? (ctx.config.timeout_ms as number | undefined) ?? DEFAULT_TIMEOUT_MS;
const controller = new AbortController();
const timer = setTimeout(() => controller.abort(), timeoutMs);
try {
let response: Response;
try {
response = await fetch(url, {
signal: controller.signal,
// Redirects can move a request to a host the author never named, so the
// final URL is reported back rather than followed silently.
redirect: "follow",
headers: { accept: "text/markdown, text/plain, application/json;q=0.9, */*;q=0.8" }
});
} catch (error) {
throw new Error(`Failed to fetch ${uri}: ${(error as Error).message}`);
}
if (!response.ok) {
throw new Error(`Failed to fetch ${uri}: HTTP ${response.status} ${response.statusText}`);
}
const declaredLength = Number(response.headers.get("content-length") ?? "0");
if (declaredLength > MAX_BYTES) {
throw new Error(`Refusing to load ${uri}: ${declaredLength} bytes exceeds the ${MAX_BYTES} byte limit.`);
}
const content = await readBody(response, uri);
return {
content,
contentType: (response.headers.get("content-type") ?? "text/plain").split(";")[0]!.trim(),
digest: sha256Uri(content),
retrievedAt: new Date().toISOString(),
trust: (ctx.config.trust as AdapterResult["trust"]) ?? "untrusted"
};
} finally {
clearTimeout(timer);
}
}
};