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83 lines
2.3 KiB
TypeScript
83 lines
2.3 KiB
TypeScript
import type { AllowedMimeType } from './constants'
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function matchJpeg(bytes: Uint8Array): boolean {
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return bytes.length >= 3
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&& bytes[0] === 0xFF
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&& bytes[1] === 0xD8
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&& bytes[2] === 0xFF
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}
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function matchPng(bytes: Uint8Array): boolean {
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const signature = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]
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if (bytes.length < signature.length) return false
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return signature.every((byte, index) => bytes[index] === byte)
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}
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function matchGif(bytes: Uint8Array): boolean {
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if (bytes.length < 6) return false
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const header = new TextDecoder().decode(bytes.subarray(0, 6))
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return header === 'GIF87a' || header === 'GIF89a'
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}
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function matchWebp(bytes: Uint8Array): boolean {
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if (bytes.length < 12) return false
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const riff = new TextDecoder().decode(bytes.subarray(0, 4))
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const webp = new TextDecoder().decode(bytes.subarray(8, 12))
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return riff === 'RIFF' && webp === 'WEBP'
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}
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/** ICO 文件头：00 00 01 00 */
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function matchIco(bytes: Uint8Array): boolean {
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return bytes.length >= 6
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&& bytes[0] === 0x00
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&& bytes[1] === 0x00
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&& bytes[2] === 0x01
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&& bytes[3] === 0x00
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}
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/** SVG 是 XML 文本，无二进制签名，按内容开头识别 */
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function matchSvg(bytes: Uint8Array): boolean {
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if (!bytes.length) return false
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const head = new TextDecoder('utf-8', { fatal: false })
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.decode(bytes.subarray(0, 1024))
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const trimmed = head.replace(/^\uFEFF/, '').trimStart()
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if (
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!trimmed.startsWith('<?xml')
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&& !trimmed.startsWith('<svg')
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&& !trimmed.startsWith('<!--')
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) {
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return false
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}
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return /<svg[\s>]/i.test(head)
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}
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const SIGNATURE_CHECKS: Record<AllowedMimeType, (bytes: Uint8Array) => boolean> = {
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'image/jpeg': matchJpeg,
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'image/png': matchPng,
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'image/gif': matchGif,
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'image/webp': matchWebp,
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'image/x-icon': matchIco,
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'image/svg+xml': matchSvg
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}
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export function isAllowedMimeType(mime: string): mime is AllowedMimeType {
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return mime in SIGNATURE_CHECKS
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}
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export function validateFileSignature(
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mime: AllowedMimeType,
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bytes: Uint8Array
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): boolean {
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const checker = SIGNATURE_CHECKS[mime]
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return checker(bytes)
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}
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export function detectMimeFromSignature(bytes: Uint8Array): AllowedMimeType | null {
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for (const mime of Object.keys(SIGNATURE_CHECKS) as AllowedMimeType[]) {
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if (SIGNATURE_CHECKS[mime](bytes)) {
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return mime
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}
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}
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return null
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}
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