Fix folder hashing: Murmur hash didn't work reliably

API.md

@@ -346,12 +346,13 @@ The algorithm works as follows:
       - add to `childrenHashes`: `hashFolder(folderId, fields)`
     - if it's a bookmark
       - add to `childrenHashes`: `hashBookmark(bookmarkId, fields)`
-  - Return `murmur2(to_json({title: folderTitle, children: childrenHashes}))`
+  - Return `sha256(to_json({title: folderTitle, children: childrenHashes}))` with the title being unset in case of the root folder
 - `hashBookmark(id, fields)`
   - for all entries in `fields`
     - set `object[field]` to the value of the associated field of the bookmark
-  - Return `murmur2(to_json(object))`
-- `murmur2`: [The murmur2 hashing algorithm](https://en.wikipedia.org/wiki/MurmurHash)
+  - Return `sha256(to_json(object))`
+- `to_json`: A JSON stringification algorithm that adds no unnecessary white-space and doesn't use JSON's backslash escaping unless necessary (character set is UTF-8)
+- `sha256`: The SHA-256 hashing algorithm
 
 ### Delete folders
 

lib/Bookmarks.php

@@ -333,8 +333,12 @@ class Bookmarks {
 				  throw new UnexpectedValueException('Expected bookmark or folder, but not '.$item['type']);
 			}
 		}, $children);
-		$folder = ['title' => $folderRecord['title'], 'children' => $childHashes];
-		return Murmur2Hash::hash(json_encode($folder));
+		$folder = [];
+		if (isset($folderRecord['title'])) {
+			$folder['title'] = $folderRecord['title'];
+		}
+		$folder['children'] = $childHashes;
+		return hash('sha256', json_encode($folder, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES));
 	}
 
 	public function deleteFolder($userId, $folderId) {
@@ -419,7 +423,7 @@ class Bookmarks {
 				$bookmark[$field] = $bookmarkRecord[$field];
 			}
 		}
-		return Murmur2Hash::hash(json_encode($bookmark));
+		return hash('sha256', json_encode($bookmark, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES));
 	}
 
 

lib/Murmur2Hash.php

@@ -1,66 +0,0 @@
-<?php
-namespace OCA\Bookmarks;
-
-class Murmur2Hash {
-	public static function hash($str) {
-		$l = strlen($str);
-		$h = $l;
-		$i = 0;
-
-		while ($l >= 4) {
-			$k = ((ord(substr($str, $i)) & 0xff)) |
-	  ((ord(substr($str, ++$i)) & 0xff) << 8) |
-	  ((ord(substr($str, ++$i)) & 0xff) << 16) |
-	  ((ord(substr($str, ++$i)) & 0xff) << 24);
-
-			$k = ((($k & 0xffff) * 0x5bd1e995) + (((self::unsignedRightShift($k, 16) * 0x5bd1e995) & 0xffff) << 16));
-			$k ^= self::unsignedRightShift($k, 24);
-			$k = ((($k & 0xffff) * 0x5bd1e995) + (((self::unsignedRightShift($k, 16) * 0x5bd1e995) & 0xffff) << 16));
-
-			$h = ((($h & 0xffff) * 0x5bd1e995) + (((self::unsignedRightShift($h, 16) * 0x5bd1e995) & 0xffff) << 16)) ^ $k;
-
-			$l -= 4;
-			++$i;
-		}
-
-		switch ($l) {
-		case 3: $h ^= (ord(substr($str, $i + 2)) & 0xff) << 16;
-		// no break
-		case 2: $h ^= (ord(substr($str, $i + 1)) & 0xff) << 8;
-		// no break
-		case 1: $h ^= (ord(substr($str, $i)) & 0xff);
-		  $h = ((($h & 0xffff) * 0x5bd1e995) + (((self::unsignedRightShift($h, 16) * 0x5bd1e995) & 0xffff) << 16));
-  }
-
-		$h ^= self::unsignedRightShift($h, 13);
-		$h = ((($h & 0xffff) * 0x5bd1e995) + (((self::unsignedRightShift($h, 16) * 0x5bd1e995) & 0xffff) << 16));
-		$h ^= self::unsignedRightShift($h, 15);
-
-		return self::unsignedRightShift($h, 0);
-	}
-
-	private static function unsignedRightShift($a, $b) {
-		if ($b >= 32 || $b < -32) {
-			$m = (int)($b/32);
-			$b = $b-($m*32);
-		}
-
-		if ($b < 0) {
-			$b = 32 + $b;
-		}
-
-		if ($b == 0) {
-			return (($a>>1) & 0x7fffffff) * 2 + (($a>>$b) & 1);
-		}
-
-		if ($a < 0) {
-			$a = ($a >> 1);
-			$a &= 0x7fffffff;
-			$a |= 0x40000000;
-			$a = ($a >> ($b - 1));
-		} else {
-			$a = ($a >> $b);
-		}
-		return $a;
-	}
-}