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109 lines
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4.9 KiB
Markdown
109 lines
No EOL
4.9 KiB
Markdown
# Threat analysis for the federated star activity
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## Technical Background
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### Control Flow
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```mermaid
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sequenceDiagram
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participant fs as foreign_repository_server
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participant os as our_repository_server
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fs ->> os: post /api/activitypub/repository-id/1/inbox {Start-Activity}
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activate os
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os ->> os: validate request inputs
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activate repository
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os ->> repository: search for reop with object-id
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deactivate repository
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activate user
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os ->> user: search for user with actor-id
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user ->> user: create if not found
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activate user
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user ->> fs: get /api/activitypub/user-id/{id from actor}
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user ->> user: create user from response
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deactivate user
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deactivate user
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os ->> repository: execute star action
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os -->> fs: 200 ok
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deactivate os
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```
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### Data transfered
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```
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# edn notation
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{@context [
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"as": "https://www.w3.org/ns/activitystreams#",
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"forge": "https://forgefed.org/ns#",],
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::as/id "https://repo.prod.meissa.de/api/v1/activitypub/user-id/1/outbox/12345",
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::as/type "Star",
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::forge/source "forgejo",
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::as/actor "https://repo.prod.meissa.de/api/v1/activitypub/user-id/1",
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::as/object "https://codeberg.org/api/v1/activitypub/repository-id/12"
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}
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# json notation
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{"id": "https://repo.prod.meissa.de/api/v1/activitypub/user-id/1/outbox/12345",
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"type": "Star",
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"source": "forgejo",
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"actor": "https://repo.prod.meissa.de/api/v1/activitypub/user-id/1",
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"object": "https://codeberg.org/api/v1/activitypub/repository-id/12"
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}
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```
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### Data Flow
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```mermaid
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flowchart TD
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A(User) --> |stars a federated repository| B(foreign repository server)
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B --> |Star Activity| C(our repository server)
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C --> |get Person Actor| B
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C --> |create federated user localy| D(our database)
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C --> |add star to repo localy| D
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```
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## Analysis
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### Assets
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1. **Service Availability**: The availability of our or foreign servers.
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2. **Reputation**: Our standing against freinds and others.
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### Actors
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1. **Script Kiddies**: Boored teens, willing to do some illigal without deep knowlege of tech details but broad knowlege across internet discussions. Able to do some bash / python scripting.
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2. **Experienced Hacker**: Hacker with deep knowlege.
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3. **OpenSource Promoter**:
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### Threat
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1. Script Kiddi sends a Star Activity containing an attack actor url `http://attacked.target/very/special/path` in place of actor. Our repository server sends an `get Person Actor` request to this url. The attacked target gets DenialdOffServices. We loose CPU & reputation.
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2. Experienced hacker sends a Star Activity containing an actor url pointing to an evil forgejo instance. Our repository server sends an `get Person Actor` request to this instance and get a person having sth. like `; drop database;` in its name. If our server tries to create a new user out of this persion, the db might be droped.
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3. OpenSource Promoter sends Star Activities having not authorized Person Actors. The Actors listed as stargazer migth get angry about this, we loose reputation.
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4. Experienced Hacker records activities sent and replays some of them. Without order of activities (i.e. timestamp) we can not decide wether we should execute the activity again. If the replayed activities are Unstar Activity we might loose stars.
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5. Experienced Hacker records activities sends a massive amount of activities which leads to new user creation & storage. Our instance might get off service.
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### Mitigations
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1. Validate object uri in order to send only requests to well defined endpoints.
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2. giteas global SQL injection protection. TODO: verify if there is one.
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3. We accept only signed Activities
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4. We accept only activities having an timestamp & remember the last executed activity timestamp.
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5. ...
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### DREAD-Score
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| Threat | Damage | Reproducibility | Exploitability | Affected Users | Discoverability | Mitigations |
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| :----- | :------ | :-------------- | :------------- | :------------- | :-------------- | :---------- |
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| 1. | ... tbd | | | | | |
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| 2. | ... tbd | | | | | |
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Bewertet wird mit Schulnoten von 1 - 6
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* Damage – wie groß wäre der Schaden, wenn der Angriff erfolgreich ist? 6 ist ein sehr schlimmer Schaden.
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* Reproducibility – wie einfach wäre der Angriff reproduzierbar? 6 ist sehr einfach zu reproduzieren.
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* Exploitability – wieviel Zeit, Aufwand und Erfahrung sind notwendig, um die Bedrohung auszunutzen? 6 ist sehr einfach zu machen.
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* Affected Users – wenn eine Bedrohung ausgenutzt werden würde, wieviel Prozent der Benutzer wären betroffen?
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* Discoverability – Wie einfach lässt sich ein Angriff entdecken? Muss der Angreifer Strafverfolgung erwarten? 6 ist sehr schwer zu entdecken / ist gar nicht illegal
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## Reference
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* https://geballte-sicherheit.de/threat-modelling-bedrohungsanalyse-7-teil-einstufung-von-bedrohungen-ranking-of-threats/ |