Relax the EncryptMetadata check.

core/fpdfapi/parser/cpdf_security_handler.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fpdfapi/parser/cpdf_security_handler.h"
 
 #include <time.h>
 
@@ skipping 368 matching lines @@
       std::min(sizeof(perms_buf), static_cast<size_t>(perms.GetLength()));
   FXSYS_memcpy(perms_buf, perms.raw_str(), copy_len);
   uint8_t buf[16];
   CRYPT_AESDecrypt(aes.data(), buf, perms_buf, 16);
   if (buf[9] != 'a' || buf[10] != 'd' || buf[11] != 'b')
     return false;
 
   if (FXDWORD_GET_LSBFIRST(buf) != m_Permissions)
     return false;
 
-  bool encrypted = IsMetadataEncrypted();
-  if ((buf[8] == 'T' && !encrypted) || (buf[8] == 'F' && encrypted))
-    return false;
-  return true;
+  // Relax this check as there appear to be some non-conforming documents
+  // in the wild. The value in the buffer is the truth; if it requires us
+  // to encrypt metadata, but the dictionary says otherwise, then we may
+  // have a tampered doc.  Otherwise, give it a pass.
+  return buf[8] == 'F' || IsMetadataEncrypted();
 }
 
 bool CPDF_SecurityHandler::CheckPassword(const uint8_t* password,
                                          uint32_t size,
                                          bool bOwner,
                                          uint8_t* key,
                                          int32_t key_len) {
   if (m_Revision >= 5)
     return AES256_CheckPassword(password, size, bOwner, key);
 
@@ skipping 302 matching lines @@
   uint8_t* aes = FX_Alloc(uint8_t, 2048);
   CRYPT_AESSetKey(aes, 16, key, 32, true);
   uint8_t iv[16], buf1[16];
   FXSYS_memset(iv, 0, 16);
   CRYPT_AESSetIV(aes, iv);
   CRYPT_AESEncrypt(aes, buf1, buf, 16);
   FX_Free(aes);
   pEncryptDict->SetNewFor<CPDF_String>("Perms", CFX_ByteString(buf1, 16),
                                        false);
 }