| 1 | import { deflateSync } from "node:zlib"; |
| 2 | import { describe, expect, it } from "vitest"; |
| 3 | import { applyDelta, parsePack, sha1 } from "../src/index.js"; |
| 4 | |
| 5 | /** A pack from raw entries: [type code, declared size, body (already deflated, with any delta base prefix)]. */ |
| 6 | async function pack(entries: Array<[number, number, Uint8Array]>): Promise<Uint8Array> { |
| 7 | const parts: number[] = [..."PACK"].map((c) => c.charCodeAt(0)); |
| 8 | const u32 = (n: number) => parts.push((n >>> 24) & 255, (n >>> 16) & 255, (n >>> 8) & 255, n & 255); |
| 9 | u32(2); |
| 10 | u32(entries.length); |
| 11 | for (const [type, size, body] of entries) { |
| 12 | let s = size; |
| 13 | let c = (type << 4) | (s & 15); |
| 14 | s = Math.floor(s / 16); |
| 15 | while (s > 0) { |
| 16 | parts.push(c | 0x80); |
| 17 | c = s & 0x7f; |
| 18 | s = Math.floor(s / 128); |
| 19 | } |
| 20 | parts.push(c); |
| 21 | parts.push(...body); |
| 22 | } |
| 23 | const body = new Uint8Array(parts); |
| 24 | const out = new Uint8Array(body.length + 20); |
| 25 | out.set(body); |
| 26 | out.set(await sha1(body), body.length); |
| 27 | return out; |
| 28 | } |
| 29 | const varint = (n: number) => { |
| 30 | const out: number[] = []; |
| 31 | do { |
| 32 | let b = n % 128; |
| 33 | n = Math.floor(n / 128); |
| 34 | if (n > 0) b |= 0x80; |
| 35 | out.push(b); |
| 36 | } while (n > 0); |
| 37 | return out; |
| 38 | }; |
| 39 | |
| 40 | describe("untrusted packs can't make the server inflate or allocate without bound", () => { |
| 41 | it("stops inflating an object at its declared size", async () => { |
| 42 | // Declares 10 bytes, inflates to 64 MiB. |
| 43 | const bomb = deflateSync(Buffer.alloc(64 * 1024 * 1024)); |
| 44 | await expect(parsePack(await pack([[3, 10, bomb]]))).rejects.toThrow(/larger than its declared size/); |
| 45 | }); |
| 46 | |
| 47 | it("refuses a pack whose objects unpack past the budget", async () => { |
| 48 | const blob = Buffer.alloc(600 * 1024, 120); |
| 49 | const p = await pack([ |
| 50 | [3, blob.length, deflateSync(blob)], |
| 51 | [3, blob.length, deflateSync(Buffer.concat([blob.subarray(1), Buffer.from("y")]))], |
| 52 | ]); |
| 53 | await expect(parsePack(p, undefined, { maxBytes: 1024 * 1024 })).rejects.toThrow(/unpacks to more than/); |
| 54 | expect((await parsePack(p, undefined, { maxBytes: 2 * 1024 * 1024 })).length).toBe(2); |
| 55 | }); |
| 56 | |
| 57 | it("counts every inflation of a large blob that tiny deltas use as their base", async () => { |
| 58 | // One 2 MiB blob, kept compressed, then 20 one-byte deltas against it by offset. |
| 59 | const blob = Buffer.alloc(2 * 1024 * 1024); |
| 60 | const header = (type: number, size: number) => { |
| 61 | const out: number[] = []; |
| 62 | let c = (type << 4) | (size & 15); |
| 63 | size = Math.floor(size / 16); |
| 64 | while (size > 0) { |
| 65 | out.push(c | 0x80); |
| 66 | c = size & 0x7f; |
| 67 | size = Math.floor(size / 128); |
| 68 | } |
| 69 | out.push(c); |
| 70 | return out; |
| 71 | }; |
| 72 | const ofs = (n: number) => { |
| 73 | const out = [n & 127]; |
| 74 | while ((n = Math.floor(n / 128))) out.unshift(0x80 | (--n & 127)); |
| 75 | return out; |
| 76 | }; |
| 77 | const parts: number[] = [..."PACK"].map((c) => c.charCodeAt(0)), u32 = (n: number) => parts.push((n >>> 24) & 255, (n >>> 16) & 255, (n >>> 8) & 255, n & 255); |
| 78 | u32(2); |
| 79 | u32(21); |
| 80 | const base = parts.length; |
| 81 | parts.push(...header(3, blob.length), ...deflateSync(blob)); |
| 82 | const delta = Uint8Array.from([...varint(blob.length), ...varint(1), 0x91, 0, 1]); |
| 83 | for (let i = 0; i < 20; i++) parts.push(...header(6, delta.length), ...ofs(parts.length - base), ...deflateSync(delta)); |
| 84 | const body = new Uint8Array(parts); |
| 85 | const p = new Uint8Array(body.length + 20); |
| 86 | p.set(body); |
| 87 | p.set(await sha1(body), body.length); |
| 88 | const opts = { maxBytes: 16 * 1024 * 1024, largeObjectBytes: 1024 * 1024 }; |
| 89 | await expect(parsePack(p, undefined, opts)).rejects.toThrow(/unpacks to more than/); |
| 90 | // Kept whole, the blob is inflated once and the same pack fits. |
| 91 | expect((await parsePack(p, undefined, { maxBytes: opts.maxBytes })).length).toBe(21); |
| 92 | }); |
| 93 | |
| 94 | it("checks a delta's result size before allocating it", () => { |
| 95 | const delta = Uint8Array.from([...varint(3), ...varint(2 ** 40), 0x91, 0, 3]); |
| 96 | expect(() => applyDelta(Uint8Array.from([1, 2, 3]), delta, 1024 * 1024)).toThrow(/larger than/); |
| 97 | }); |
| 98 | }); |