I am sniffing packets on the network and recovering the XML data from the raw payload using Scapy and Python. The XML data I get has a few tags missing when I assemble the frames.Thus, I cannot parse the XML file using etree.parse() function. Is there any method by which I can parse the broken XML file and use XPATH expressions to traverse and get the data I want.
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1 Answer
I'm sure my solution is far too simple to cover all cases, but it should be able to cover simple cases when closing tags are missing:
>>> def fix_xml(string):
"""
Tries to insert missing closing XML tags
"""
error = True
while error:
try:
# Put one tag per line
string = string.replace('>', '>\n').replace('\n\n', '\n')
root = etree.fromstring(string)
error = False
except etree.XMLSyntaxError as exc:
text = str(exc)
pattern = "Opening and ending tag mismatch: (\w+) line (\d+) and (\w+), line (\d+), column (\d+)"
m = re.match(pattern, text)
if m:
# Retrieve where error took place
missing, l1, closing, l2, c2 = m.groups()
l1, l2, c2 = int(l1), int(l2), int(c2)
lines = string.split('\n')
print 'Adding closing tag <{0}> at line {1}'.format(missing, l2)
missing_line = lines[l2 - 1]
# Modified line goes back to where it was
lines[l2 - 1] = missing_line.replace('</{0}>'.format(closing), '</{0}></{1}>'.format(missing, closing))
string = '\n'.join(lines)
else:
raise
print string
This seems to add correctly missing tags B and C:
>>> s = """<A>
<B>
<C>
</B>
<B></A>"""
>>> fix_xml(s)
Adding closing tag <C> at line 4
Adding closing tag <B> at line 7
<A>
<B>
<C>
</C>
</B>
<B>
</B>
</A>
