From d30e950bf9688f6ecf2e98aadf9cad033ef84920 Mon Sep 17 00:00:00 2001
From: Mikunj <mikunj@live.com.au>
Date: Mon, 11 Feb 2019 15:00:30 +1100
Subject: [PATCH] Changed hashing algorithm.

---
 js/link_previews_helper.js | 20 ++++++++------------
 js/models/messages.js      |  3 ++-
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/js/link_previews_helper.js b/js/link_previews_helper.js
index adaf8378b..87b1899c5 100644
--- a/js/link_previews_helper.js
+++ b/js/link_previews_helper.js
@@ -1,6 +1,7 @@
 /* global
   Signal,
   textsecure,
+  StringView
 */
 
 /* eslint-disable no-bitwise */
@@ -61,17 +62,10 @@
     };
   }
 
-  function hashCode(string) {
-    let hash = 0;
-    if (string.length === 0) {
-      return hash;
-    }
-    for (let i = 0; i < string.length; i += 1) {
-      const char = string.charCodeAt(i);
-      hash = (hash << 5) - hash + char;
-      hash &= hash; // Convert to 32bit integer
-    }
-    return hash;
+  async function sha256(string) {
+    const arraybuffer = new TextEncoder('utf-8').encode(string);
+    const digest = await window.crypto.subtle.digest('SHA-256', arraybuffer);
+    return StringView.arrayBufferToHex(digest);
   }
 
   async function getPreview(url) {
@@ -132,11 +126,13 @@
       }
     }
 
+    const hash = await sha256(url);
+
     return {
       title,
       url,
       image,
-      hash: hashCode(url),
+      hash,
     };
   }
 
diff --git a/js/models/messages.js b/js/models/messages.js
index bc0e4b9b1..2847af3bd 100644
--- a/js/models/messages.js
+++ b/js/models/messages.js
@@ -159,10 +159,11 @@
         const { data } = image;
         const extension = Attachment.getFileExtension(image);
         if (data && extension) {
+          const hash32 = hash.substring(0, 32);
           try {
             const filePath = await writeAttachment({
               data,
-              path: `previews/${hash}.${extension}`,
+              path: `previews/${hash32}.${extension}`,
             });
 
             // return the image without the data