update SPECIFICATION.md

Fix https://github.com/misskey-dev/media-proxy/issues/6

.eslintrc.cjs

@@ -1,32 +0,0 @@
-module.exports = {
-	parserOptions: {
-		tsconfigRootDir: __dirname,
-		project: ['./tsconfig.json'],
-	},
-	extends: [
-		'../shared/.eslintrc.js',
-	],
-	rules: {
-		'import/order': ['warn', {
-			'groups': ['builtin', 'external', 'internal', 'parent', 'sibling', 'index', 'object', 'type'],
-			'pathGroups': [
-				{
-					'pattern': '@/**',
-					'group': 'external',
-					'position': 'after'
-				}
-			],
-		}],
-		'no-restricted-globals': [
-			'error',
-			{
-				'name': '__dirname',
-				'message': 'Not in ESModule. Use `import.meta.url` instead.'
-			},
-			{
-				'name': '__filename',
-				'message': 'Not in ESModule. Use `import.meta.url` instead.'
-			}
-	]
-	},
-};

SPECIFICATION.md

@@ -26,6 +26,7 @@ Acceptヘッダーは無視される。
 Cache-Controlは、正常なレスポンスの場合`max-age=31536000, immutable`、エラーレスポンスの場合`max-age=300`である。  
 Content-Typeは、ファイルの内容について適切なものが挿入される。
 Content-Security-Policyは、`default-src 'none'; img-src 'self'; media-src 'self'; style-src 'unsafe-inline'`となっている。
+Content-Dispositionは、filenameは元画像のContent-Disposition.filenameもしくはファイル名に基づいて挿入される。拡張子は適宜変更され、octet-streamの場合は拡張子として.unknownが付加される。inlineが指定される。
 
 ### クエリの一覧
 #### url (必須)
@@ -51,6 +52,9 @@ https://www.google.com/images/errors/robot.png をプロキシする場合:
 変換形式が指定されていなかった場合は、画像ファイルもしくは許可されたファイル（FILE_TYPE_BROWSERSAFE）である場合のみプロキシ（ファイルの再配信）が行われる。  
 ただし、svgは、webpに変換される（最大サイズ2048x2048）。
 
+#### 変換クエリ付加時の挙動
+一方、以下の変換クエリが指定されているが、元ファイルがsharp.jsで変換できない形式の場合、404が返される。
+
 #### emoji
 存在すると、高さ128px以下のwebpが応答される。  
 ただし、sharp.jsの都合により、元画像がapngの場合は無変換で応答される。
@@ -68,7 +72,7 @@ https://www.google.com/images/errors/robot.png をプロキシする場合:
 #### static
 存在すると、アニメーション画像では最初のフレームのみの静止画のwebpが応答される。
 
-emojiまたはavatarとstaticが同時に指定された場合は、それぞれに応じた高さが、指定されていない場合は幅498px・高さ280pxに収まるサイズ以下に縮小される。  
+emojiまたはavatarとstaticが同時に指定された場合は、それぞれに応じた高さが、指定されていない場合は幅498px・高さ422pxに収まるサイズ以下に縮小される。
 
 #### preview
 存在すると、幅200px・高さ200pxに収まるサイズ以下のwebpが応答される。

built/download.d.ts

@@ -19,4 +19,6 @@ export declare const defaultDownloadConfig: {
     maxSize: number;
     proxy: boolean;
 };
-export declare function downloadUrl(url: string, path: string, settings?: DownloadConfig): Promise<void>;
+export declare function downloadUrl(url: string, path: string, settings?: DownloadConfig): Promise<{
+    filename: string;
+}>;

built/download.js

@@ -6,6 +6,7 @@ import IPCIDR from 'ip-cidr';
 import PrivateIp from 'private-ip';
 import { StatusError } from './status-error.js';
 import { getAgents } from './http.js';
+import { parse } from 'content-disposition';
 const pipeline = util.promisify(stream.pipeline);
 export const defaultDownloadConfig = {
     userAgent: `MisskeyMediaProxy/0.0.0`,
@@ -19,6 +20,8 @@ export async function downloadUrl(url, path, settings = defaultDownloadConfig) {
         console.log(`Downloading ${url} to ${path} ...`);
     const timeout = 30 * 1000;
     const operationTimeout = 60 * 1000;
+    const urlObj = new URL(url);
+    let filename = urlObj.pathname.split('/').pop() ?? 'unknown';
     const req = got.stream(url, {
         headers: {
             'User-Agent': settings.userAgent,
@@ -56,6 +59,13 @@ export async function downloadUrl(url, path, settings = defaultDownloadConfig) {
                 req.destroy();
             }
         }
+        const contentDisposition = res.headers['content-disposition'];
+        if (contentDisposition != null) {
+            const parsed = parse(contentDisposition);
+            if (parsed.parameters.filename) {
+                filename = parsed.parameters.filename;
+            }
+        }
     }).on('downloadProgress', (progress) => {
         if (progress.transferred > settings.maxSize) {
             console.log(`maxSize exceeded (${progress.transferred} > ${settings.maxSize}) on downloadProgress`);
@@ -75,6 +85,9 @@ export async function downloadUrl(url, path, settings = defaultDownloadConfig) {
     }
     if (process.env.NODE_ENV !== 'production')
         console.log(`Download finished: ${url}`);
+    return {
+        filename,
+    };
 }
 function isPrivateIp(ip, allowedPrivateNetworks) {
     for (const net of allowedPrivateNetworks ?? []) {

built/file-info.js

@@ -55,7 +55,7 @@ async function checkSvg(path) {
 import { FILE_TYPE_BROWSERSAFE } from './const.js';
 const dictionary = {
     'safe-file': FILE_TYPE_BROWSERSAFE,
-    'sharp-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/apng', 'image/vnd.mozilla.apng', 'image/webp', 'image/avif', 'image/svg+xml'],
+    'sharp-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/apng', 'image/vnd.mozilla.apng', 'image/webp', 'image/avif', 'image/svg+xml', 'image/x-icon', 'image/bmp'],
-    'sharp-animation-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'image/avif', 'image/svg+xml'],
+    'sharp-animation-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'image/avif', 'image/svg+xml', 'image/x-icon', 'image/bmp'],
 };
 export const isMimeImage = (mime, type) => dictionary[type].includes(mime);

built/image-processor.js

@@ -1,11 +1,12 @@
 import sharp from 'sharp';
 export const webpDefault = {
-    quality: 85,
+    quality: 77,
     alphaQuality: 95,
     lossless: false,
     nearLossless: false,
     smartSubsample: true,
     mixed: true,
+    effort: 2,
 };
 export function convertToWebpStream(path, width, height, options = webpDefault) {
     return convertSharpToWebpStream(sharp(path), width, height, options);

built/index.js

@@ -4,12 +4,14 @@ import { dirname } from 'node:path';
 import fastifyStatic from '@fastify/static';
 import { createTemp } from './create-temp.js';
 import { FILE_TYPE_BROWSERSAFE } from './const.js';
-import { convertToWebpStream, webpDefault } from './image-processor.js';
+import { convertToWebpStream, webpDefault, convertSharpToWebpStream } from './image-processor.js';
 import { detectType, isMimeImage } from './file-info.js';
 import sharp from 'sharp';
+import { sharpBmp } from 'sharp-read-bmp';
 import { StatusError } from './status-error.js';
 import { defaultDownloadConfig, downloadUrl } from './download.js';
 import { getAgents } from './http.js';
+import _contentDisposition from 'content-disposition';
 const _filename = fileURLToPath(import.meta.url);
 const _dirname = dirname(_filename);
 const assets = `${_dirname}/../assets/`;
@@ -106,7 +108,7 @@ async function proxyHandler(request, reply) {
                 };
             }
             else {
-                const data = sharp(file.path, { animated: !('static' in request.query) })
+                const data = (await sharpBmp(file.path, file.mime, { animated: !('static' in request.query) }))
                     .resize({
                     height: 'emoji' in request.query ? 128 : 320,
                     withoutEnlargement: true,
@@ -120,13 +122,13 @@ async function proxyHandler(request, reply) {
             }
         }
         else if ('static' in request.query) {
-            image = convertToWebpStream(file.path, 498, 280);
+            image = convertSharpToWebpStream(await sharpBmp(file.path, file.mime), 498, 422);
         }
         else if ('preview' in request.query) {
-            image = convertToWebpStream(file.path, 200, 200);
+            image = convertSharpToWebpStream(await sharpBmp(file.path, file.mime), 200, 200);
         }
         else if ('badge' in request.query) {
-            const mask = sharp(file.path)
+            const mask = (await sharpBmp(file.path, file.mime))
                 .resize(96, 96, {
                 fit: 'inside',
                 withoutEnlargement: false,
@@ -182,6 +184,7 @@ async function proxyHandler(request, reply) {
         }
         reply.header('Content-Type', image.type);
         reply.header('Cache-Control', 'max-age=31536000, immutable');
+        reply.header('Content-Disposition', contentDisposition('inline', correctFilename(file.filename, image.ext)));
         return reply.send(image.data);
     }
     catch (e) {
@@ -193,12 +196,13 @@ async function proxyHandler(request, reply) {
 async function downloadAndDetectTypeFromUrl(url) {
     const [path, cleanup] = await createTemp();
     try {
-        await downloadUrl(url, path, config);
+        const { filename } = await downloadUrl(url, path, config);
         const { mime, ext } = await detectType(path);
         return {
             state: 'remote',
             mime, ext,
             path, cleanup,
+            filename: correctFilename(filename, ext),
         };
     }
     catch (e) {
@@ -206,3 +210,20 @@ async function downloadAndDetectTypeFromUrl(url) {
         throw e;
     }
 }
+function correctFilename(filename, ext) {
+    const dotExt = ext ? `.${ext}` : '.unknown';
+    if (filename.endsWith(dotExt)) {
+        return filename;
+    }
+    if (ext === 'jpg' && filename.endsWith('.jpeg')) {
+        return filename;
+    }
+    if (ext === 'tif' && filename.endsWith('.tiff')) {
+        return filename;
+    }
+    return `${filename}${dotExt}`;
+}
+function contentDisposition(type, filename) {
+    const fallback = filename.replace(/[^\w.-]/g, '_');
+    return _contentDisposition(filename, { type, fallback });
+}

package.json

@@ -1,9 +1,9 @@
 {
   "name": "misskey-media-proxy",
-  "version": "0.0.13",
+  "version": "0.0.19",
   "description": "The Media Proxy for Misskey",
   "main": "built/index.js",
-  "packageManager": "pnpm@7.26.0",
+  "packageManager": "pnpm@7.28.0",
   "type": "module",
   "files": [
     "built",
@@ -28,6 +28,7 @@
   "devDependencies": {
     "@swc/cli": "^0.1.61",
     "@swc/core": "^1.3.32",
+    "@types/content-disposition": "^0.5.5",
     "@types/node": "^18.11.19",
     "@types/sharp": "^0.31.1",
     "@types/tmp": "^0.2.3",
@@ -36,6 +37,7 @@
   "dependencies": {
     "@fastify/static": "^6.8.0",
     "cacheable-lookup": "^7.0.0",
+    "content-disposition": "^0.5.4",
     "fastify": "^4.12.0",
     "fastify-cli": "^5.7.1",
     "file-type": "^18.2.0",
@@ -45,6 +47,7 @@
     "is-svg": "^4.3.2",
     "private-ip": "^3.0.0",
     "sharp": "^0.31.3",
+    "sharp-read-bmp": "github:misskey-dev/sharp-read-bmp",
     "tmp": "^0.2.1"
   }
 }

pnpm-lock.yaml

@@ -4,10 +4,12 @@ specifiers:
   '@fastify/static': ^6.8.0
   '@swc/cli': ^0.1.61
   '@swc/core': ^1.3.32
+  '@types/content-disposition': ^0.5.5
   '@types/node': ^18.11.19
   '@types/sharp': ^0.31.1
   '@types/tmp': ^0.2.3
   cacheable-lookup: ^7.0.0
+  content-disposition: ^0.5.4
   fastify: ^4.12.0
   fastify-cli: ^5.7.1
   file-type: ^18.2.0
@@ -17,12 +19,14 @@ specifiers:
   is-svg: ^4.3.2
   private-ip: ^3.0.0
   sharp: ^0.31.3
+  sharp-read-bmp: github:misskey-dev/sharp-read-bmp
   tmp: ^0.2.1
   typescript: ^4.9.5
 
 dependencies:
   '@fastify/static': 6.8.0
   cacheable-lookup: 7.0.0
+  content-disposition: 0.5.4
   fastify: 4.12.0
   fastify-cli: 5.7.1
   file-type: 18.2.0
@@ -32,11 +36,13 @@ dependencies:
   is-svg: 4.3.2
   private-ip: 3.0.0
   sharp: 0.31.3
+  sharp-read-bmp: github.com/misskey-dev/sharp-read-bmp/c5fb82e26fa50fca8b3b2d7e22467626d7f61baa
   tmp: 0.2.1
 
 devDependencies:
   '@swc/cli': 0.1.61_@swc+core@1.3.32
   '@swc/core': 1.3.32
+  '@types/content-disposition': 0.5.5
   '@types/node': 18.11.19
   '@types/sharp': 0.31.1
   '@types/tmp': 0.2.3
@@ -44,6 +50,10 @@ devDependencies:
 
 packages:
 
+  /@canvas/image-data/1.0.0:
+    resolution: {integrity: sha512-BxOqI5LgsIQP1odU5KMwV9yoijleOPzHL18/YvNqF9KFSGF2K/DLlYAbDQsWqd/1nbaFuSkYD/191dpMtNh4vw==}
+    dev: false
+
   /@chainsafe/is-ip/2.0.1:
     resolution: {integrity: sha512-nqSJ8u2a1Rv9FYbyI8qpDhTYujaKEyLknNrTejLYoSWmdeg+2WB7R6BZqPZYfrJzDxVi3rl6ZQuoaEvpKRZWgQ==}
     dev: false
@@ -300,6 +310,10 @@ packages:
       '@types/responselike': 1.0.0
     dev: true
 
+  /@types/content-disposition/0.5.5:
+    resolution: {integrity: sha512-v6LCdKfK6BwcqMo+wYW05rLS12S0ZO0Fl4w1h4aaZMD7bqT3gVUns6FvLJKGZHQmYn3SX55JWGpziwJRwVgutA==}
+    dev: true
+
   /@types/http-cache-semantics/4.0.1:
     resolution: {integrity: sha512-SZs7ekbP8CN0txVG2xVRH6EgKmEm31BOxA07vkFaETzZz1xh+cbt8BcI0slpymvwhx5dlFnQG2rTlPVQn+iRPQ==}
 
@@ -635,6 +649,23 @@ packages:
       ms: 2.1.2
     dev: false
 
+  /decode-bmp/0.2.1:
+    resolution: {integrity: sha512-NiOaGe+GN0KJqi2STf24hfMkFitDUaIoUU3eKvP/wAbLe8o6FuW5n/x7MHPR0HKvBokp6MQY/j7w8lewEeVCIA==}
+    engines: {node: '>=8.6.0'}
+    dependencies:
+      '@canvas/image-data': 1.0.0
+      to-data-view: 1.1.0
+    dev: false
+
+  /decode-ico/0.4.1:
+    resolution: {integrity: sha512-69NZfbKIzux1vBOd31al3XnMnH+2mqDhEgLdpygErm4d60N+UwA5Sq5WFjmEDQzumgB9fElojGwWG0vybVfFmA==}
+    engines: {node: '>=8.6'}
+    dependencies:
+      '@canvas/image-data': 1.0.0
+      decode-bmp: 0.2.1
+      to-data-view: 1.1.0
+    dev: false
+
   /decompress-response/6.0.0:
     resolution: {integrity: sha512-aW35yZM6Bb/4oJlZncMH2LCoZtJXTRxES17vE3hoRiowU2kWHaJKFkSBDnDR+cm9J+9QhXmREyIfv0pji9ejCQ==}
     engines: {node: '>=10'}
@@ -1970,6 +2001,10 @@ packages:
     resolution: {integrity: sha512-3f0uOEAQwIqGuWW2MVzYg8fV/QNnc/IpuJNG837rLuczAaLVHslWHZQj4IGiEl5Hs3kkbhwL9Ab7Hrsmuj+Smw==}
     dev: false
 
+  /to-data-view/1.1.0:
+    resolution: {integrity: sha512-1eAdufMg6mwgmlojAx3QeMnzB/BTVp7Tbndi3U7ftcT2zCZadjxkkmLmd97zmaxWi+sgGcgWrokmpEoy0Dn0vQ==}
+    dev: false
+
   /to-regex-range/5.0.1:
     resolution: {integrity: sha512-65P7iz6X5yEr1cwcgvQxbbIw7Uk3gOy5dIdtZ4rDveLqhrdJP+Li/Hx6tyK0NEb+2GCyneCMJiGqrADCSNk8sQ==}
     engines: {node: '>=8.0'}
@@ -2056,3 +2091,13 @@ packages:
     resolution: {integrity: sha512-rVksvsnNCdJ/ohGc6xgPwyN8eheCxsiLM8mxuE/t/mOVqJewPuO1miLpTHQiRgTKCLexL4MeAFVagts7HmNZ2Q==}
     engines: {node: '>=10'}
     dev: false
+
+  github.com/misskey-dev/sharp-read-bmp/c5fb82e26fa50fca8b3b2d7e22467626d7f61baa:
+    resolution: {tarball: https://codeload.github.com/misskey-dev/sharp-read-bmp/tar.gz/c5fb82e26fa50fca8b3b2d7e22467626d7f61baa}
+    name: sharp-read-bmp
+    version: 1.0.0
+    dependencies:
+      decode-bmp: 0.2.1
+      decode-ico: 0.4.1
+      sharp: 0.31.3
+    dev: false

src/download.ts

@@ -8,6 +8,7 @@ import IPCIDR from 'ip-cidr';
 import PrivateIp from 'private-ip';
 import { StatusError } from './status-error.js';
 import { getAgents } from './http.js';
+import { parse } from 'content-disposition';
 
 const pipeline = util.promisify(stream.pipeline);
 
@@ -29,12 +30,17 @@ export const defaultDownloadConfig = {
     ...getAgents()
 }
 
-export async function downloadUrl(url: string, path: string, settings:DownloadConfig = defaultDownloadConfig): Promise<void> {
+export async function downloadUrl(url: string, path: string, settings:DownloadConfig = defaultDownloadConfig): Promise<{
+    filename: string;
+}> {
     if (process.env.NODE_ENV !== 'production') console.log(`Downloading ${url} to ${path} ...`);
 
     const timeout = 30 * 1000;
     const operationTimeout = 60 * 1000;
 
+    const urlObj = new URL(url);
+    let filename = urlObj.pathname.split('/').pop() ?? 'unknown';
+
     const req = got.stream(url, {
         headers: {
             'User-Agent': settings.userAgent,
@@ -73,6 +79,14 @@ export async function downloadUrl(url: string, path: string, settings:DownloadCo
                 req.destroy();
             }
         }
+
+        const contentDisposition = res.headers['content-disposition'];
+        if (contentDisposition != null) {
+            const parsed = parse(contentDisposition);
+            if (parsed.parameters.filename) {
+                filename = parsed.parameters.filename;
+            }
+        }
     }).on('downloadProgress', (progress: Got.Progress) => {
         if (progress.transferred > settings.maxSize) {
             console.log(`maxSize exceeded (${progress.transferred} > ${settings.maxSize}) on downloadProgress`);
@@ -91,6 +105,10 @@ export async function downloadUrl(url: string, path: string, settings:DownloadCo
     }
 
     if (process.env.NODE_ENV !== 'production') console.log(`Download finished: ${url}`);
+
+    return {
+        filename,
+    }
 }
 
 function isPrivateIp(ip: string, allowedPrivateNetworks: string[]): boolean {

src/file-info.ts

@@ -66,8 +66,8 @@ import { FILE_TYPE_BROWSERSAFE } from './const.js';
 
 const dictionary = {
     'safe-file': FILE_TYPE_BROWSERSAFE,
-    'sharp-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/apng', 'image/vnd.mozilla.apng', 'image/webp', 'image/avif', 'image/svg+xml'],
+    'sharp-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/apng', 'image/vnd.mozilla.apng', 'image/webp', 'image/avif', 'image/svg+xml', 'image/x-icon', 'image/bmp'],
-    'sharp-animation-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'image/avif', 'image/svg+xml'],
+    'sharp-animation-convertible-image': ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'image/avif', 'image/svg+xml', 'image/x-icon', 'image/bmp'],
 };
 
 export const isMimeImage = (mime: string, type: keyof typeof dictionary): boolean => dictionary[type].includes(mime);

src/image-processor.ts

@@ -16,12 +16,13 @@ export type IImageStream = {
 export type IImageStreamable = IImage | IImageStream;
 
 export const webpDefault: sharp.WebpOptions = {
-    quality: 85,
+    quality: 77,
     alphaQuality: 95,
     lossless: false,
     nearLossless: false,
     smartSubsample: true,
     mixed: true,
+    effort: 2,
 };
 
 export function convertToWebpStream(path: string, width: number, height: number, options: sharp.WebpOptions = webpDefault): IImageStream {

src/index.ts

@@ -6,13 +6,15 @@ import { dirname } from 'node:path';
 import fastifyStatic from '@fastify/static';
 import { createTemp } from './create-temp.js';
 import { FILE_TYPE_BROWSERSAFE } from './const.js';
-import { IImageStreamable, convertToWebpStream, webpDefault } from './image-processor.js';
+import { IImageStreamable, convertToWebpStream, webpDefault, convertSharpToWebpStream } from './image-processor.js';
 import type { FastifyInstance, FastifyRequest, FastifyReply, FastifyPluginOptions } from 'fastify';
 import { detectType, isMimeImage } from './file-info.js';
 import sharp from 'sharp';
+import { sharpBmp } from 'sharp-read-bmp';
 import { StatusError } from './status-error.js';
 import { DownloadConfig, defaultDownloadConfig, downloadUrl } from './download.js';
 import { getAgents } from './http.js';
+import _contentDisposition from 'content-disposition';
 
 const _filename = fileURLToPath(import.meta.url);
 const _dirname = dirname(_filename);
@@ -152,12 +154,12 @@ async function proxyHandler(request: FastifyRequest<{ Params: { url: string; };
                     type: file.mime,
                 };
             } else {
-                const data = sharp(file.path, { animated: !('static' in request.query) })
+                const data = (await sharpBmp(file.path, file.mime, { animated: !('static' in request.query) }))
-                        .resize({
+                    .resize({
-                            height: 'emoji' in request.query ? 128 : 320,
+                        height: 'emoji' in request.query ? 128 : 320,
-                            withoutEnlargement: true,
+                        withoutEnlargement: true,
-                        })
+                    })
-                        .webp(webpDefault);
+                    .webp(webpDefault);
 
                 image = {
                     data,
@@ -166,11 +168,11 @@ async function proxyHandler(request: FastifyRequest<{ Params: { url: string; };
                 };
             }
         } else if ('static' in request.query) {
-            image = convertToWebpStream(file.path, 498, 280);
+            image = convertSharpToWebpStream(await sharpBmp(file.path, file.mime), 498, 422);
         } else if ('preview' in request.query) {
-            image = convertToWebpStream(file.path, 200, 200);
+            image = convertSharpToWebpStream(await sharpBmp(file.path, file.mime), 200, 200);
         } else if ('badge' in request.query) {
-            const mask = sharp(file.path)
+            const mask = (await sharpBmp(file.path, file.mime))
                 .resize(96, 96, {
                     fit: 'inside',
                     withoutEnlargement: false,
@@ -230,6 +232,12 @@ async function proxyHandler(request: FastifyRequest<{ Params: { url: string; };
 
         reply.header('Content-Type', image.type);
         reply.header('Cache-Control', 'max-age=31536000, immutable');
+        reply.header('Content-Disposition',
+            contentDisposition(
+                'inline',
+                correctFilename(file.filename, image.ext)
+            )
+        );
         return reply.send(image.data);
     } catch (e) {
         if ('cleanup' in file) file.cleanup();
@@ -238,11 +246,11 @@ async function proxyHandler(request: FastifyRequest<{ Params: { url: string; };
 }
 
 async function downloadAndDetectTypeFromUrl(url: string): Promise<
-    { state: 'remote'; mime: string; ext: string | null; path: string; cleanup: () => void; }
+    { state: 'remote'; mime: string; ext: string | null; path: string; cleanup: () => void; filename: string; }
 > {
     const [path, cleanup] = await createTemp();
     try {
-        await downloadUrl(url, path, config);
+        const { filename } = await downloadUrl(url, path, config);
 
         const { mime, ext } = await detectType(path);
 
@@ -250,9 +258,29 @@ async function downloadAndDetectTypeFromUrl(url: string): Promise<
             state: 'remote',
             mime, ext,
             path, cleanup,
+            filename: correctFilename(filename, ext),
         }
     } catch (e) {
         cleanup();
         throw e;
     }
 }
+
+function correctFilename(filename: string, ext: string | null) {
+    const dotExt = ext ? `.${ext}` : '.unknown';
+    if (filename.endsWith(dotExt)) {
+        return filename;
+    }
+    if (ext === 'jpg' && filename.endsWith('.jpeg')) {
+        return filename;
+    }
+    if (ext === 'tif' && filename.endsWith('.tiff')) {
+        return filename;
+    }
+    return `${filename}${dotExt}`;
+}
+
+function contentDisposition(type: 'inline' | 'attachment', filename: string): string {
+	const fallback = filename.replace(/[^\w.-]/g, '_');
+	return _contentDisposition(filename, { type, fallback });
+}