From 261ab1364aa40384b0315be60e78cd89ea7fe661 Mon Sep 17 00:00:00 2001
From: winter
Date: Sun, 23 Feb 2025 18:32:09 +0000
Subject: implement policies

---
 Digitigrade/HttpResponseStatus/PolicyRejected.php | 22 +++++++++++
 Digitigrade/Model/FetchableModel.php              |  3 +-
 Digitigrade/Model/Note.php                        |  2 +-
 Digitigrade/Model/PushableModel.php               |  3 +-
 Digitigrade/Policy.php                            | 37 ++++++++++++++++++
 Digitigrade/Policy/BasicCensor.php                | 47 +++++++++++++++++++++++
 Digitigrade/Policy/BlockInstance.php              | 37 ++++++++++++++++++
 Digitigrade/PolicyManager.php                     | 46 ++++++++++++++++++++++
 8 files changed, 194 insertions(+), 3 deletions(-)
 create mode 100644 Digitigrade/HttpResponseStatus/PolicyRejected.php
 create mode 100644 Digitigrade/Policy.php
 create mode 100644 Digitigrade/Policy/BasicCensor.php
 create mode 100644 Digitigrade/Policy/BlockInstance.php
 create mode 100644 Digitigrade/PolicyManager.php

(limited to 'Digitigrade')

diff --git a/Digitigrade/HttpResponseStatus/PolicyRejected.php b/Digitigrade/HttpResponseStatus/PolicyRejected.php
new file mode 100644
index 0000000..59a4811
--- /dev/null
+++ b/Digitigrade/HttpResponseStatus/PolicyRejected.php
@@ -0,0 +1,22 @@
+<?php
+namespace Digitigrade\HttpResponseStatus;
+
+use Digitigrade\HttpResponseStatus;
+use Digitigrade\Model\FetchableModel;
+
+class PolicyRejected extends \Exception implements HttpResponseStatus {
+    public function __construct() {
+        $this->message = "Object was rejected by one or more of the instance's policies";
+    }
+
+    public function httpCode(): int {
+        return 403;
+    }
+
+    public function httpReason(): string {
+        return "Forbidden";
+    }
+
+    public function httpHeaders() {
+    }
+}
\ No newline at end of file
diff --git a/Digitigrade/Model/FetchableModel.php b/Digitigrade/Model/FetchableModel.php
index 6d21f40..3efa763 100644
--- a/Digitigrade/Model/FetchableModel.php
+++ b/Digitigrade/Model/FetchableModel.php
@@ -2,6 +2,7 @@
 namespace Digitigrade\Model;
 
 use Digitigrade\Model;
+use Digitigrade\PolicyManager;
 use Digitigrade\RemoteFetchable;
 
 abstract class FetchableModel extends Model implements RemoteFetchable {
@@ -75,7 +76,7 @@ abstract class FetchableModel extends Model implements RemoteFetchable {
         $obj = static::createFromJson($data, $autoSave, $uri);
 
         $obj->finaliseAfterFetch($uri);
-        if (!$obj->validate()) {
+        if (!$obj->validate() || !PolicyManager::getInstance()->check($obj)) {
             return null; // and don't save
         }
         if ($autoSave) {
diff --git a/Digitigrade/Model/Note.php b/Digitigrade/Model/Note.php
index f3c0901..880e3e8 100644
--- a/Digitigrade/Model/Note.php
+++ b/Digitigrade/Model/Note.php
@@ -20,7 +20,7 @@ class Note extends PushableModel implements TimelineIncludeable, Notifyable {
     public Actor $author;
     public ?string $summary;
     public string $plainContent;
-    // associative array mapping strings to strings - mimetypes to content
+    /** @var array associative array mapping strings to strings - mimetypes to content */
     public array $formattedContent = [];
     public string $language;
     /**
diff --git a/Digitigrade/Model/PushableModel.php b/Digitigrade/Model/PushableModel.php
index 271b313..e773779 100644
--- a/Digitigrade/Model/PushableModel.php
+++ b/Digitigrade/Model/PushableModel.php
@@ -2,6 +2,7 @@
 namespace Digitigrade\Model;
 
 use Digitigrade\Job\PushObject;
+use Digitigrade\PolicyManager;
 
 abstract class PushableModel extends FetchableModel implements \JsonSerializable {
     public ?int $id;
@@ -20,7 +21,7 @@ abstract class PushableModel extends FetchableModel implements \JsonSerializable
         }
 
         $obj = static::createFromJson($data, $autoSave);
-        if (!$obj->validate()) {
+        if (!$obj->validate() || !PolicyManager::getInstance()->check($obj)) {
             return null; // and don't save
         }
         if ($autoSave) {
diff --git a/Digitigrade/Policy.php b/Digitigrade/Policy.php
new file mode 100644
index 0000000..56fbdb0
--- /dev/null
+++ b/Digitigrade/Policy.php
@@ -0,0 +1,37 @@
+<?php
+namespace Digitigrade;
+
+use Digitigrade\Model\Actor;
+use Digitigrade\Model\Interaction;
+use Digitigrade\Model\Note;
+
+abstract class Policy {
+    /**
+     * Checks if an Actor is allowed and possibly alters it.
+     * @param Actor $actor the actor to check (may be modified in-place)
+     * @return bool true if allowed, false if the actor should be dropped
+     */
+    public function checkActor(Actor $actor): bool {
+        return true;
+    }
+
+    /**
+     * Checks if an Interaction is allowed and possibly alters it.
+     * @param Interaction $interaction the interaction to check (may be modified in-place)
+     * @return bool true if allowed, false if the interaction should be dropped
+     */
+    public function checkInteraction(Interaction $interaction): bool {
+        return true;
+    }
+
+    /**
+     * Checks if a Note is allowed and possibly alters it.
+     * @param Note $note the note to check (may be modified in-place)
+     * @return bool true if allowed, false if the note should be dropped
+     */
+    public function checkNote(Note $note): bool {
+        return true;
+    }
+
+    // TODO: public function checkExtension()
+}
\ No newline at end of file
diff --git a/Digitigrade/Policy/BasicCensor.php b/Digitigrade/Policy/BasicCensor.php
new file mode 100644
index 0000000..5866488
--- /dev/null
+++ b/Digitigrade/Policy/BasicCensor.php
@@ -0,0 +1,47 @@
+<?php
+namespace Digitigrade\Policy;
+
+use Digitigrade\Model\Actor;
+use Digitigrade\Model\Note;
+use Digitigrade\Policy;
+
+/**
+ * Simple word censorship policy that replaces all instances of some text with another string.
+ * 
+ * Suffers from the Scunthorpe problem.
+ * 
+ * Can also be (ab)used to replace some word with another word for humorous effect :3
+ */
+class BasicCensor extends Policy {
+    /** @var string[] */
+    private array $words;
+    private string $replacement;
+
+    public function __construct(array $words, string $replacement) {
+        $this->words = $words;
+        $this->replacement = $replacement;
+    }
+
+    public function checkNote(Note $note): bool {
+        foreach ($this->words as $w) {
+            if (isset($note->summary))
+                $note->summary = str_replace($w, $this->replacement, $note->summary);
+            $note->plainContent = str_replace($w, $this->replacement, $note->plainContent);
+            foreach ($note->formattedContent as $type => $content) {
+                $note->formattedContent[$type] = str_replace($w, $this->replacement, $content);
+            }
+        }
+        return true;
+    }
+
+    public function checkActor(Actor $actor): bool {
+        foreach ($this->words as $w) {
+            $actor->displayName = str_replace($w, $this->replacement, $actor->displayName);
+            if (isset($actor->pronouns))
+                $actor->pronouns = str_replace($w, $this->replacement, $actor->pronouns);
+            if (isset($actor->bio))
+                $actor->bio = str_replace($w, $this->replacement, $actor->bio);
+        }
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/Digitigrade/Policy/BlockInstance.php b/Digitigrade/Policy/BlockInstance.php
new file mode 100644
index 0000000..5f902f2
--- /dev/null
+++ b/Digitigrade/Policy/BlockInstance.php
@@ -0,0 +1,37 @@
+<?php
+namespace Digitigrade\Policy;
+
+use Digitigrade\Model\Actor;
+use Digitigrade\Model\Interaction;
+use Digitigrade\Model\Note;
+use Digitigrade\Model\PushableModel;
+use Digitigrade\Policy;
+
+class BlockInstance extends Policy {
+    /** @var string[] */
+    private array $blockedHosts;
+
+    public function __construct(string ...$hosts) {
+        $this->blockedHosts = $hosts;
+    }
+
+    private function isBlocked(PushableModel $obj): bool {
+        $objHost = hostname_from_uri($obj->uri);
+        foreach ($this->blockedHosts as $host) {
+            if (str_ends_with($objHost, $host)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public function checkActor(Actor $actor): bool {
+        return !$this->isBlocked($actor);
+    }
+    public function checkInteraction(Interaction $interaction): bool {
+        return !$this->isBlocked($interaction);
+    }
+    public function checkNote(Note $note): bool {
+        return !$this->isBlocked($note);
+    }
+}
\ No newline at end of file
diff --git a/Digitigrade/PolicyManager.php b/Digitigrade/PolicyManager.php
new file mode 100644
index 0000000..24c2c7f
--- /dev/null
+++ b/Digitigrade/PolicyManager.php
@@ -0,0 +1,46 @@
+<?php
+namespace Digitigrade;
+
+use Digitigrade\Model\Actor;
+use Digitigrade\Model\FetchableModel;
+use Digitigrade\Model\Interaction;
+use Digitigrade\Model\Note;
+
+class PolicyManager extends Singleton {
+    /** @var Policy[] */
+    private array $policies = [];
+
+    public function register(Policy $policy) {
+        $this->policies[] = $policy;
+    }
+
+    public function registerAll(Policy ...$policies) {
+        foreach ($policies as $p) {
+            $this->register($p);
+        }
+    }
+
+    /**
+     * Checks if an object is allowed by all policies and possibly alters it.
+     * @param FetchableModel $object the object to check (may be modified in-place)
+     * @return bool true if allowed, false if it should be dropped
+     */
+    public function check(FetchableModel $object): bool {
+        return match ($object::class) {
+            Actor::class => self::arrayAll($this->policies, fn(Policy $p) => $p->checkActor($object)),
+            Interaction::class => self::arrayAll($this->policies, fn(Policy $p) => $p->checkInteraction($object)),
+            Note::class => self::arrayAll($this->policies, fn(Policy $p) => $p->checkNote($object)),
+            default => true
+        };
+    }
+
+    private static function arrayAll(array $arr, callable $test): bool {
+        // i would use array_all but that's php 8.4+ only which i don't have lol
+        foreach ($arr as $item) {
+            if (!$test($item)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
\ No newline at end of file
-- 
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