[Files] correct for anomalies in content disposition value for file d…

…ownloads (elastic#176822)

## Summary

closes; elastic#173138

Looking into this, it turns out this issue was happening because the
header value for `content-disposition` contained invalid characters
given we were using the filename as is.

See Screenshot resulting from debugging the request; 

<img width="846" alt="Screenshot 2024-02-13 at 13 38 53"
src="https://github.com/elastic/kibana/assets/7893459/c1fbc09c-53c3-4d5b-8ba9-8752a56a9a6b">


To fix this, I've opted to leverage the ~package
[content-disposition](https://github.com/jshttp/content-disposition), in
place of some custom approach to fix this~ `res.file` handler which
correctly handles computation for content-disposition in place of
`res.ok` ~and providing our own computation of the value for
content-disposition~.

## Verifying the fix:

- Navigate to cases, (found in the the nav menu for stack management)
- create a new case, if there isn't one you can readily use
- click the files tab and grab an image you'd like to upload, before you
do rename said image to `Screenshot 2023-12-11 at 1 29 07 PM` keeping
it's extension
- on image upload complete, you should be able to view the preview for
the just uploaded image.

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### Risk Matrix

Delete this section if it is not applicable to this PR.

Before closing this PR, invite QA, stakeholders, and other developers to
identify risks that should be tested prior to the change/feature
release.

When forming the risk matrix, consider some of the following examples
and how they may potentially impact the change:

| Risk | Probability | Severity | Mitigation/Notes |

|---------------------------|-------------|----------|-------------------------|
| Multiple Spaces&mdash;unexpected behavior in non-default Kibana Space.
| Low | High | Integration tests will verify that all features are still
supported in non-default Kibana Space and when user switches between
spaces. |
| Multiple nodes&mdash;Elasticsearch polling might have race conditions
when multiple Kibana nodes are polling for the same tasks. | High | Low
| Tasks are idempotent, so executing them multiple times will not result
in logical error, but will degrade performance. To test for this case we
add plenty of unit tests around this logic and document manual testing
procedure. |
| Code should gracefully handle cases when feature X or plugin Y are
disabled. | Medium | High | Unit tests will verify that any feature flag
or plugin combination still results in our service operational. |
| [See more potential risk
examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx) |


### For maintainers

- [ ] This was checked for breaking API changes and was [labeled
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src/plugins/files/server/routes/common.test.ts

@@ -10,48 +10,40 @@ import type { File } from '../file';
 import { getDownloadHeadersForFile } from './common';
 
 describe('getDownloadHeadersForFile', () => {
-  function expectHeaders({
-    contentDisposition,
-    contentType,
-  }: {
-    contentDisposition: string;
-    contentType: string;
-  }) {
+  function expectHeaders({ contentType }: { contentType: string }) {
     return {
       'content-type': contentType,
-      'content-disposition': `attachment; filename="${contentDisposition}"`,
       'cache-control': 'max-age=31536000, immutable',
-      'x-content-type-options': 'nosniff',
     };
   }
 
   const file = { data: { name: 'test', mimeType: undefined } } as unknown as File;
   test('no mime type and name from file object', () => {
     expect(getDownloadHeadersForFile({ file, fileName: undefined })).toEqual(
-      expectHeaders({ contentType: 'application/octet-stream', contentDisposition: 'test' })
+      expectHeaders({ contentType: 'application/octet-stream' })
     );
   });
 
   test('no mime type and name (without ext)', () => {
     expect(getDownloadHeadersForFile({ file, fileName: 'myfile' })).toEqual(
-      expectHeaders({ contentType: 'application/octet-stream', contentDisposition: 'myfile' })
+      expectHeaders({ contentType: 'application/octet-stream' })
     );
   });
   test('no mime type and name (with ext)', () => {
     expect(getDownloadHeadersForFile({ file, fileName: 'myfile.png' })).toEqual(
-      expectHeaders({ contentType: 'image/png', contentDisposition: 'myfile.png' })
+      expectHeaders({ contentType: 'image/png' })
     );
   });
   test('mime type and no name', () => {
     const fileWithMime = { data: { ...file.data, mimeType: 'application/pdf' } } as File;
     expect(getDownloadHeadersForFile({ file: fileWithMime, fileName: undefined })).toEqual(
-      expectHeaders({ contentType: 'application/pdf', contentDisposition: 'test' })
+      expectHeaders({ contentType: 'application/pdf' })
     );
   });
   test('mime type and name', () => {
     const fileWithMime = { data: { ...file.data, mimeType: 'application/pdf' } } as File;
     expect(getDownloadHeadersForFile({ file: fileWithMime, fileName: 'a cool file.pdf' })).toEqual(
-      expectHeaders({ contentType: 'application/pdf', contentDisposition: 'a cool file.pdf' })
+      expectHeaders({ contentType: 'application/pdf' })
     );
   });
 });

src/plugins/files/server/routes/common.ts

@@ -19,11 +19,7 @@ export function getDownloadHeadersForFile({ file, fileName }: Args): ResponseHea
   return {
     'content-type':
       (fileName && mime.getType(fileName)) ?? file.data.mimeType ?? 'application/octet-stream',
-    // Note, this name can be overridden by the client if set via a "download" attribute on the HTML tag.
-    'content-disposition': `attachment; filename="${fileName || getDownloadedFileName(file)}"`,
     'cache-control': 'max-age=31536000, immutable',
-    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
-    'x-content-type-options': 'nosniff',
   };
 }
 

src/plugins/files/server/routes/file_kind/download.ts

@@ -12,7 +12,7 @@ import type { FilesClient } from '../../../common/files_client';
 import type { FileKind } from '../../../common/types';
 import { fileNameWithExt } from '../common_schemas';
 import { fileErrors } from '../../file';
-import { getDownloadHeadersForFile } from '../common';
+import { getDownloadHeadersForFile, getDownloadedFileName } from '../common';
 import { getById } from './helpers';
 import type { CreateHandler, FileKindRouter } from './types';
 import { CreateRouteDefinition, FILES_API_ROUTES } from '../api_routes';
@@ -39,8 +39,9 @@ export const handler: CreateHandler<Endpoint> = async ({ files, fileKind }, req,
   if (error) return error;
   try {
     const body: Response = await file.downloadContent();
-    return res.ok({
+    return res.file({
       body,
+      filename: fileName ?? getDownloadedFileName(file),
       headers: getDownloadHeadersForFile({ file, fileName }),
     });
   } catch (e) {

src/plugins/files/server/routes/file_kind/integration_tests/file_kind_http.test.ts

@@ -72,7 +72,7 @@ describe('File kind HTTP API', () => {
       .expect(200);
 
     expect(header['content-type']).toEqual('image/png');
-    expect(header['content-disposition']).toEqual('attachment; filename="test.png"');
+    expect(header['content-disposition']).toEqual('attachment; filename=test.png');
     expect(buffer.toString('utf8')).toEqual('what have you');
   });
 

src/plugins/files/server/routes/integration_tests/routes.test.ts

@@ -331,7 +331,7 @@ describe('File HTTP API', () => {
         .expect(200);
 
       expect(header['content-type']).toEqual('application/pdf');
-      expect(header['content-disposition']).toEqual('attachment; filename="myfilename.pdf"');
+      expect(header['content-disposition']).toEqual('attachment; filename=myfilename.pdf');
       expect(buffer.toString('utf8')).toEqual('test');
     });
   });

src/plugins/files/server/routes/public_facing/download.ts

@@ -17,7 +17,7 @@ import {
 } from '../../file_share_service/errors';
 import type { FilesRouter } from '../types';
 import { CreateRouteDefinition, FILES_API_ROUTES } from '../api_routes';
-import { getDownloadHeadersForFile } from '../common';
+import { getDownloadHeadersForFile, getDownloadedFileName } from '../common';
 import { fileNameWithExt } from '../common_schemas';
 import { CreateHandler } from '../types';
 
@@ -44,8 +44,9 @@ const handler: CreateHandler<Endpoint> = async ({ files }, req, res) => {
   try {
     const file = await fileService.asInternalUser().getByToken(token);
     const body: Readable = await file.downloadContent();
-    return res.ok({
+    return res.file({
       body,
+      filename: fileName ?? getDownloadedFileName(file),
       headers: getDownloadHeadersForFile({ file, fileName }),
     });
   } catch (e) {

x-pack/test/api_integration/apis/cases/files.ts

@@ -310,7 +310,7 @@ export default ({ getService }: FtrProviderContext): void => {
                 });
 
                 expect(header['content-type']).to.eql('image/png');
-                expect(header['content-disposition']).to.eql('attachment; filename="test.png"');
+                expect(header['content-disposition']).to.eql('attachment; filename=test.png');
                 expect(buffer.toString('utf8')).to.eql('abc');
               });