From 32884fd8675eaeb8797b3d459f0bc5382cf09136 Mon Sep 17 00:00:00 2001
From: dartcafe <github@dartcafe.de>
Date: Mon, 27 Mar 2023 20:57:10 +0200
Subject: [PATCH] shorten public links to 8 characters

Signed-off-by: dartcafe <github@dartcafe.de>
---
 CHANGELOG.md                 |  1 +
 lib/Service/ShareService.php | 30 ++++++++++++++++++++++++------
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 31d31e8d1..215d35a53 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ All notable changes to this project will be documented in this file.
  - Added qr code for public shares
 ### Changes
  - PHP 8.0 as minimum requirement
+ - Shorten public tokens to 8 characters (lower and upper characters and digits)
  
 ## [4.1.5] - 2023-02-25
 ### Fix
diff --git a/lib/Service/ShareService.php b/lib/Service/ShareService.php
index c540c4be6..bb4fba6f9 100644
--- a/lib/Service/ShareService.php
+++ b/lib/Service/ShareService.php
@@ -422,12 +422,30 @@ class ShareService {
 		string $timeZone = ''
 	): Share {
 		$preventInvitation = $userGroup->getType() === UserBase::TYPE_PUBLIC ?: $preventInvitation;
-		$token = $this->secureRandom->generate(
-			16,
-			ISecureRandom::CHAR_DIGITS .
-				ISecureRandom::CHAR_LOWER .
-				ISecureRandom::CHAR_UPPER
-		);
+
+		$token = null;
+		$loopCounter = 0;
+		// Generate a unique id
+		while (!$token) {
+			$loopCounter++;
+			$token = $this->secureRandom->generate(
+				8,
+				ISecureRandom::CHAR_DIGITS .
+					ISecureRandom::CHAR_LOWER .
+					ISecureRandom::CHAR_UPPER
+			);
+			try {
+				$this->shareMapper->findByToken($token);
+				// reset token, if it already exists
+				$token = null;
+			} catch (ShareNotFoundException) {
+				$loopCounter = 0;
+			}
+			if ($loopCounter > 10) {
+				// In case of uninspected situations, avoid an endless loop
+				throw new \Exception('Unexpected loop count while trying to create a token for a new share');
+			}
+		}
 
 		$this->share = new Share();
 		$this->share->setToken($token);