83 lines
2.2 KiB
TypeScript
83 lines
2.2 KiB
TypeScript
export const MAX_FORM_ANSWER_IMAGE_BYTES = 50 * 1024 * 1024;
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const ALLOWED_IMAGE_MIME_TYPES = new Set([
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"image/png",
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"image/jpeg",
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"image/webp",
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"image/gif",
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]);
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const ALLOWED_IMAGE_EXTENSIONS = new Set(["png", "jpg", "jpeg", "webp", "gif"]);
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export function validateImageUploadFile(
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file: Pick<File, "name" | "type" | "size">,
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bytes?: Uint8Array
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) {
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if (!ALLOWED_IMAGE_MIME_TYPES.has(file.type)) {
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throw new Error("Only PNG, JPG, WebP, and GIF images are allowed");
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}
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if (file.size > MAX_FORM_ANSWER_IMAGE_BYTES) {
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throw new Error("Image must be 50MB or smaller");
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}
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if (file.size === 0) {
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throw new Error("Image cannot be empty");
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}
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const extension = (file.name.split(".").pop() || "").toLowerCase();
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if (!ALLOWED_IMAGE_EXTENSIONS.has(extension)) {
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throw new Error("Invalid image extension");
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}
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if (bytes && !hasMatchingImageSignature(file.type, bytes)) {
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throw new Error("Image contents do not match the declared image type");
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}
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}
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function hasMatchingImageSignature(type: string, bytes: Uint8Array) {
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if (type === "image/png") {
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return bytes.length >= 8 &&
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bytes.slice(0, 8).every((value, index) => value === [137, 80, 78, 71, 13, 10, 26, 10][index]);
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}
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if (type === "image/jpeg") {
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return bytes.length >= 3 && bytes[0] === 0xff && bytes[1] === 0xd8 && bytes[2] === 0xff;
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}
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if (type === "image/gif") {
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return bytes.length >= 6 &&
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(String.fromCharCode(...bytes.slice(0, 6)) === "GIF87a" ||
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String.fromCharCode(...bytes.slice(0, 6)) === "GIF89a");
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}
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if (type === "image/webp") {
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return bytes.length >= 12 &&
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String.fromCharCode(...bytes.slice(0, 4)) === "RIFF" &&
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String.fromCharCode(...bytes.slice(8, 12)) === "WEBP";
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}
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return false;
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}
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export function cdnUrl(id: string | null | undefined) {
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return id ? `/cdn/${id}` : "";
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}
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export type CdnResponseRecord = {
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data: Buffer;
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type: string;
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size: number;
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};
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export function cdnImageResponse(record: CdnResponseRecord) {
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return new Response(new Uint8Array(record.data), {
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headers: {
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"Content-Type": record.type,
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"Content-Length": String(record.size),
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"Cache-Control": "public, max-age=31536000, immutable",
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"X-Content-Type-Options": "nosniff",
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},
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});
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}
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