Node.js image to safely embed user content

Closes GH-9.

text/0005-camo-image-proxy.md

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+*   2023-07-04
+*   Scope: new repository
+*   RFC PR: <!-- leave this empty -->
+*   Implementation issue(s): <!-- leave this empty -->
+
+# Summary
+
+A new Node.js HTTP proxy to route images through SSL, compatible with unified
+plugins, to safely embed user content on the web.
+
+Implementation would be done by me and would require funds from Open Collective.
+
+## Motivation
+
+Unified has put a lot of effort in providing similar markdown support as GitHub.
+The latest project, [`rehype-github`][], takes this even further in order to
+support processing user content for safe use on the web, just as GitHub does.
+
+There is a missing piece in safely authoring user content: images.
+
+> An HTTPS page that includes content fetched using cleartext HTTP is called a
+> mixed content page.  Pages like this are only partially encrypted, leaving the
+> unencrypted content accessible to sniffers and man-in-the-middle attackers.
+> — [MDN](https://developer.mozilla.org/en-US/docs/Web/Security/Mixed_content)
+
+Developers aware of this problem, who are using Go or are willing to run a Go
+server, can use the well maintained [go-camo][] to solve this.  However, there
+is no Node.js equivalent, nor is there a plug-and-play solution for processing
+markdown which takes this problem into account.
+
+Case in point: a new Node.js HTTP proxy to route images through SSL, to be
+used together with the existing [`rehype-github-image`][] plugin.
+
+It’s in the ecosystem’s and the web’s best interest to create awareness and
+solutions for security problems when authoring user content.
+
+## Detailed design
+
+*   A bare bones Node.js server (no framework).
+    The reason for this is that we can create a `handle` function which can be
+    integrated in any Node.js framework or even a front-end framework
+    like Next.js.  This is what I’ve worked on for `@tus/server`,
+    as you can see in the [examples](https://github.com/tus/tus-node-server/tree/main/packages/server#examples).
+*   A client-server flow similar to this:
+
+```text
+  +----------+           request            +-------------+
+  |          |----------------------------->|             |
+  |          |                              |             |
+  |          |                              |   web-app   |
+  |          | img src=https://camo/url     |             |
+  |          |<-----------------------------|             |
+  |          |                              +-------------+
+  |  client  |
+  |          |     https://camo/url         +-------------+ http://some/img
+  |          |----------------------------->|             |--------------->
+  |          |                              |             |
+  |          |                              |   camo      |
+  |          |           img data           |             |    img data
+  |          |<-----------------------------|             |<---------------
+  |          |                              +-------------+
+  +----------+
+```
+
+*   Out of scope (for now): metrics endpoint for usage data, filtering rules.
+
+## Funding
+
+In short: between $500 and $1,000 from Open Collective (exact amount up for
+debate).
+
+*   **Why take money at all?**
+    *   I’m not really in a position to do this for free.  I make my living from
+        maintaining open source software on freelance basis and life is also
+        busy.  To really push this through I would put other paid work on hold.
+    *   Since there is no
+        [expenses/invoices/fund policy](https://github.com/unifiedjs/collective/issues/34),
+        taking money from Open Collective is not clearly defined.
+        But here is how I ideally imagine it:
+        funds are used to kick start substantial work which
+        otherwise may not have happened.  Many people maintain OSS for free
+        (and thanklessly) but we also shouldn’t be afraid to ask for funds.
+        There is at the time of writing $23,648 in Open Collective.
+        It’s not a lot if you want to live from it,
+        but it is a lot if you would divide it by the amount of
+        projects it could kick start.
+*   **Why me?**  I have experience in creating Node.js servers at scale and
+    globally distributed.  I also maintain [tus](https://tus.io/), a protocol
+    for resumable file uploads in multiple languages.
+*   **Why this amount of $**?  With implementation, tests, and docs, this could
+    take around three full days (optimistically).  Naturally, I didn’t base this
+    on a freelance rate I work for normally.  It’s more an attempt at a fair
+    flat fee.
+
+## Drawbacks
+
+*   Money out of the Open Collective.
+*   [go-camo][] already exists so there is some solution to this problem.
+    But for people with front-end frameworks or Node.js servers this would mean
+    hosting another server.  Furthermore unified could contribute to awareness
+    of the problem and a streamlined plug-and-play experience.
+
+## Alternatives
+
+*   Only keeping the [`rehype-github-image`][] plugin and document the existing
+    servers, not creating a Node.js server.
+
+## Adoption strategy
+
+Not relevant since it is a new project.
+
+[`rehype-github`]: https://github.com/rehypejs/rehype-github
+
+[`rehype-github-image`]: https://github.com/rehypejs/rehype-github/tree/main/packages/image
+
+[go-camo]: https://github.com/cactus/go-camo