From fed4899c8db6587eab3a7657a2ba3ecce6bc0102 Mon Sep 17 00:00:00 2001
From: Matthew Chen <matthew@signal.org>
Date: Fri, 15 Mar 2019 10:01:57 -0400
Subject: [PATCH] Handle incoming attachments with missing MIME type.

---
 .../Messages/Attachments/TSAttachmentPointer.m | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/SignalServiceKit/src/Messages/Attachments/TSAttachmentPointer.m b/SignalServiceKit/src/Messages/Attachments/TSAttachmentPointer.m
index e967ed40d..da2684f01 100644
--- a/SignalServiceKit/src/Messages/Attachments/TSAttachmentPointer.m
+++ b/SignalServiceKit/src/Messages/Attachments/TSAttachmentPointer.m
@@ -116,9 +116,17 @@ NS_ASSUME_NONNULL_BEGIN
         OWSFailDebug(@"Invalid attachment key.");
         return nil;
     }
-    if (attachmentProto.contentType.length < 1) {
-        OWSFailDebug(@"Invalid attachment content type.");
-        return nil;
+    NSString *_Nullable fileName = attachmentProto.fileName;
+    NSString *_Nullable contentType = attachmentProto.contentType;
+    if (contentType.length < 1) {
+        OWSLogError(@"Invalid attachment content type.");
+        NSString *_Nullable fileExtension = [fileName pathExtension].lowercaseString;
+        if (fileExtension.length > 0) {
+            contentType = [MIMETypeUtil mimeTypeForFileExtension:fileExtension];
+        }
+        if (contentType.length < 1) {
+            contentType = OWSMimeTypeApplicationOctetStream;
+        }
     }
 
     // digest will be empty for old clients.
@@ -151,8 +159,8 @@ NS_ASSUME_NONNULL_BEGIN
                                                                              key:attachmentProto.key
                                                                           digest:digest
                                                                        byteCount:attachmentProto.size
-                                                                     contentType:attachmentProto.contentType
-                                                                  sourceFilename:attachmentProto.fileName
+                                                                     contentType:contentType
+                                                                  sourceFilename:fileName
                                                                          caption:caption
                                                                   albumMessageId:albumMessageId
                                                                   attachmentType:attachmentType