mahara-contributors team mailing list archive

[Aaron Wells <1482410@xxxxxxxxxxxxxxxxxx>]

Using a for-loop and the PHP chr() command, I individually tested each
ASCII character in the middle of an otherwise acceptable XML file. I
tested them plain, after passing through htmlspecialchars(), and after
passing through htmlentities(). Here is the list of the decimal integer
codes for the ASCII characters that cause SimpleXML to choke. None of
them are escaped by htmlspecialchars() or htmlentities().

$baddies =
array(0,1,2,3,4,5,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31);

To help with testing (because it's not always easy to generate these
characters), I've attached a file controlcharacters.txt which contains
all 29 of these characters, in between <bad> tags. Depending on your
text editor, opening it you may just see "<bad></bad>". But if you
select the whole thing and paste it into a Mahara page title, you should
be able to replicate the problem

To replicate:

1. Create a Mahara page with one or more of the forbidden characters in its page title
2. Export the page to Leap2a
3. Import the Leap2a file back into Mahara

Expected result: You've imported a copy of the page
Actual result: You get an error stack with the SimpleXML parser error as part of it.

** Attachment added: "A text file containing the range of control characters SimpleXML won't parse"
   https://bugs.launchpad.net/mahara/+bug/1482410/+attachment/4440731/+files/controlcharacters.txt

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https://bugs.launchpad.net/bugs/1482410

Title:
  Leap2A import problem: "simplexml_load_file()... parser error : PCDATA
  invalid Char value..."

Status in Mahara:
  In Progress

Bug description:
  We had a report of a Mahara-generated Leap2a file that caused this
  crash stack upon attempting to import it:

  [WAR] 38 (import/leap/lib.php:126) simplexml_load_file(): /home/aaronw/dataroot/mahara/temp/import/admin-1438900425/extract/leap2a.xml:1808: parser error : PCDATA invalid Char value 11
  Call stack (most recent first):

      log_message("simplexml_load_file(): /home/aaronw/dataroot/mahar...", 8, true, true, "/home/aaronw/www/mahara/htdocs/import/leap/lib.php", 126) at /home/aaronw/www/mahara/htdocs/lib/errors.php:441
      error(2, "simplexml_load_file(): /home/aaronw/dataroot/mahar...", "/home/aaronw/www/mahara/htdocs/import/leap/lib.php", 126, array(size 2)) at Unknown:0
      simplexml_load_file("/home/aaronw/dataroot/mahara/temp/import/admin-143...", "SimpleXMLElement", 67584) at /home/aaronw/www/mahara/htdocs/import/leap/lib.php:126
      PluginImportLeap->read_leap2a_xml_file() at /home/aaronw/www/mahara/htdocs/import/leap/lib.php:147
      PluginImportLeap->build_default_load_mapping() at /home/aaronw/www/mahara/htdocs/import/leap/lib.php:164
      PluginImportLeap->process(1) at /home/aaronw/www/mahara/htdocs/import/index.php:245
      import_submit(object(Pieform), array(size 3)) at Unknown:0
      call_user_func_array("import_submit", array(size 2)) at /home/aaronw/www/mahara/htdocs/lib/pieforms/pieform.php:537
      Pieform->__construct(array(size 6)) at /home/aaronw/www/mahara/htdocs/lib/pieforms/pieform.php:164
      Pieform::process(array(size 6)) at /home/aaronw/www/mahara/htdocs/lib/pieforms/pieform.php:71
      pieform(array(size 6)) at /home/aaronw/www/mahara/htdocs/import/index.php:171
      print_upload_form() at /home/aaronw/www/mahara/htdocs/import/index.php:61

  Upon investigation it turned out that the leap2a XML file had a
  Vertical Tab character (ASCII x0A) in one of the page titles. There is
  a whole range of ASCII control characters that will cause a parser
  error in SimpleXML, and if they're placed in a Mahara page title, they
  will be included in the output of the Leap2a file, which will cause
  Mahara to crash when it attempts to import the file.

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