initial draft

.gitignore

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+*.html
+

biblio.json

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+{
+    "Community.Solid.Server": {
+        "authors": [
+            "Joachim Van Herwegen"
+        ],
+        "href": "https://communitysolidserver.github.io/",
+        "title": "Community Solid Server"
+    },
+    "SolidOS": {
+        "authors": [
+            "Timea Turdean"
+        ],
+        "href": "https://solidos.solidcommunity.net/",
+        "title": "SolidOS"
+    }
+}

index.bs

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+<pre class='metadata'>
+Title: Solid Security Best Current Practice
+Boilerplate: issues-index no
+Boilerplate: omit conformance
+Local Boilerplate: logo yes
+Shortname: solid-best-security-practice
+Level: 1
+Status: w3c/CG-DRAFT
+Group: Solid Community Group
+Favicon: https://solidproject.org/TR/solid.svg
+ED: https://solid.github.io/specification/security-best-practice
+TR: https://solidproject.org/TR/security-best-practice
+!Created: Feb 20, 2024
+!Modified: [DATE]
+!Editor's Draft: [https://solid.github.io/specification/security-best-practice](https://solid.github.io/specification/security-best-practice)
+Repository: https://github.com/solid/security-best-practice
+Inline Github Issues: title
+Markup Shorthands: markdown yes
+Max ToC Depth: 2
+Editor: [elf Pavlik](https://elf-pavlik.hackers4peace.net/)
+Metadata Order: This version, Latest published version, Editor's Draft, Test Suite, Created, Modified, *, !*
+Metadata Include: Editor's Draft off
+Abstract:
+  This document describes best current security practice for OAuth 2.0.
+Status Text:
+  This section describes the status of this document at the time of its publication.
+
+  This document was published by the [Solid Community Group](https://www.w3.org/community/solid/) as
+  an Editor’s Draft. The information in this document is
+  still subject to change. You are invited to [contribute](https://github.com/solid/solid-oidc/issues)
+  any feedback, comments, or questions you might have.
+
+  Publication as an Editor’s Draft does not imply endorsement by the W3C Membership. This is a draft
+  document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate
+  to cite this document as other than work in progress.
+
+  This document was produced by a group operating under the [W3C Community Contributor License Agreement
+  (CLA)](https://www.w3.org/community/about/process/cla/). A human-readable
+  [summary](https://www.w3.org/community/about/process/cla-deed/) is available.
+</pre>
+
+# Attacks and Mitigations # {#attacks-and-mitigations}
+
+## Serving user-created files ## {#serving-user-created-files}
+
+An attacker could be an agent with a WebID or an application. They need append/write access to the user's server
+to store a malicious HTML file. They might have this access because the user allowed them to write a blog post,
+or because they have their own storage in a different path on the same domain.
+
+Impact of both scenarios: The attacker, pretending to be the victim, can access anything
+that the victim's account can access.
+
+
+### Use Solid-OIDC DPoP-bound ID tokens to make authenticated requests
+
+#### Prerequisites
+
+* The attacker has append/write access to a publicly readable folder/file on the server
+* The server serves [[SolidOS]] under the same domain (by default, [[Community.Solid.Server]] serves everything under the same domain)
+* The victim is logged in via [[SolidOS]], so any new session is automatically logged in again
+
+#### Attack
+
+The attacker writes a malicious `text/html` file to the server. When this file is opened by the user:
+
+* It opens [[SolidOS]] in a new tab and saves the window reference (if the writer of this document recalls correctly, opening any non-existent resource from the server returns [[SolidOS]])
+* [[SolidOS]] automatically logs in, as the user logged in there previously
+* The `text/html` file can access [[SolidOS]] via the window reference, including the authenticated fetch
+* The `text/html` file can make any requests through this authenticated fetch in the name of the currently logged-in user
+
+
+### Steal login credentials
+
+#### Prerequisites
+
+* The attacker has append/write access to a publicly readable folder/file on the server
+* The victim uses the IDP of the (small) [[Community.Solid.Server]] server
+* The storages are on the same domain as the IDP (default for [[Community.Solid.Server]])
+* The user saved their login credentials (`/idp/login/` for [[Community.Solid.Server]]) via the browser or a password manager extension
+
+
+#### Attack
+
+The attacker writes a malicious `text/html` file to the server. Depending on the application used to store the login credentials, the concrete autofill/suggestion behaviour can vary. For instance, if the user saved it with Chrome and opens the malicious file:
+
+* The victim performs any interaction with the site (e.g., clicking on a cookie banner)
+* Chrome automatically fills in `<input>` fields for the user name and password with the saved credentials
+* The malicious `text/html` file can read and send the credentials to the attacker
+* The attacker can use it to login with the IDP of the victim
+
+
+
+### Countermeasures ### {#serving-user-created-files-countermeasures}
+
+* Servers are encouraged to apply security measures when serving user-created files.
+* Multiple agents can create files on the same server, which could render `same-origin` security boundaries useless.
+* As an example countermeasure, servers could add a `Content-Security-Policy: sandbox` header to artificially enable `same-origin` security policies for files on the same origin.

logo.include

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+<a href="https://solidproject.org/TR/" class="logo">
+    <img alt="Solid" src="https://solid.github.io/solid-oidc/solid.svg" width="72">
+</a>