## another case of deja-vu
## this time, we want the slashdot style (what Yahoo said to do) only allow
## certain tags... we'll make it an option
## we'll have to tie this in some way to our HTML body displayer...
##
## Ok, there are basically four types of tags:
## 1) safe - ie, <b>, <i>, etc.
## 2) render problems - <table><form><body><frame> - these we either strip,
## or we have to ensure they match
## 3) definitely evil independent tags that we always strip
## 4) definitely evil tags which denote a region, we strip the entire region
from PassSGMLParser import PassSGMLParser
from urllib import basejoin
import string, sys
import neo_cgi
try:
from cStringIO import StringIO
except:
from StringIO import StringIO
class SafeHtml (PassSGMLParser):
_safeTags = {"P":1, "LI":1, "DD":1, "DT":1, "EM":1, "BR":1, "CITE":1,
"DFN":1, "Q":1, "STRONG":1, "IMG":1, "HR":1,
"TR":1, "TD":1, "TH":1, "CAPTION":1, "THEAD":1, "TFOOT":1,
"TBODY":1}
_matchTags = {"TABLE":1, "OL":1, "UL":1, "DL":1, "CENTER":1, "DIV":1, "PRE":1,
"SUB":1, "SUP":1, "BIG":1, "SMALL":1, "CODE":1,
"B":1, "I":1, "A":1, "TT":1, "BLOCKQUOTE":1, "U":1,
"H1":1, "H2":1, "H3":1, "H4":1, "H5":1, "H6":1, "FONT":1}
_skipTags = {"FORM":1, "HTML":1, "BODY":1, "EMBED":1, "AREA":1, "MAP":1,
"FRAME":1, "FRAMESET":1, "IFRAME":1, "META":1}
_stripTags = {"HEAD":1, "JAVA":1, "APPLET":1, "OBJECT":1,
"JAVASCRIPT":1, "LAYER":1, "STYLE":1, "SCRIPT":1}
def __init__ (self, fp, extra_safe=1, base=None, map_urls=None, new_window=1):
self._extra_safe = extra_safe
PassSGMLParser.__init__ (self, fp, extra_safe)
self._matchDict = {}
self._stripping = 0
self._base = base
self._map_urls = map_urls
self._new_window = new_window
def safe_start_strip (self):
if self._stripping == 0:
self.flush()
self._stripping = self._stripping + 1
def safe_end_strip (self):
self.flush()
self._stripping = self._stripping - 1
if self._stripping < 0: self._stripping = 0
def write (self, data):
# sys.stderr.write("write[%d] %s\n" % (self._stripping, data))
if self._stripping == 0:
# sys.stderr.write("write %s\n" % data)
PassSGMLParser.write(self, data)
def cleanup_attrs (self, tag, attrs):
new_attrs = []
tag = string.lower(tag)
if self._new_window and tag == "a":
new_attrs.append(('target', '_blank'))
for name, value in attrs:
name = string.lower(name)
if name[:2] == "on": continue ## skip any javascript events
if string.lower(value)[:11] == "javascript:": continue
if self._map_urls and name in ["action", "href", "src", "lowsrc", "background"] and value[:4] == 'cid:':
try:
value = self._map_urls[value[4:]]
except KeyError:
pass
else:
if self._base and name in ["action", "href", "src", "lowsrc", "background"]:
value = basejoin (self._base, value)
if name in ["action", "href", "src", "lowsrc", "background"]:
value = 'http://www.google.com/url?sa=D&q=%s' % (neo_cgi.urlEscape(value))
if self._new_window and tag == "a" and name == "target": continue
new_attrs.append ((name, value))
return new_attrs
def unknown_starttag(self, tag, attrs):
tag = string.upper(tag)
if SafeHtml._stripTags.has_key(tag):
self.safe_start_strip()
# sys.stderr.write("Stripping tag %s: %d\n" % (tag, self._stripping))
elif SafeHtml._skipTags.has_key(tag):
# sys.stderr.write("Skipping tag %s\n" % tag)
pass
elif SafeHtml._matchTags.has_key(tag):
# sys.stderr.write("Matching tag %s\n" % tag)
if self._matchDict.has_key(tag):
self._matchDict[tag] = self._matchDict[tag] + 1
else:
self._matchDict[tag] = 1
self.write_starttag (tag, self.cleanup_attrs(tag, attrs))
elif SafeHtml._safeTags.has_key(tag):
# sys.stderr.write("Safe tag %s\n" % tag)
self.write_starttag (tag, self.cleanup_attrs(tag, attrs))
elif not self._extra_safe:
# sys.stderr.write("Other tag %s\n" % tag)
self.write_starttag (tag, self.cleanup_attrs(tag, attrs))
def unknown_endtag(self, tag):
tag = string.upper(tag)
if SafeHtml._stripTags.has_key(tag):
self.safe_end_strip()
# sys.stderr.write("End Stripping tag %s: %d\n" % (tag, self._stripping))
elif self._stripping == 0:
if SafeHtml._skipTags.has_key(tag):
pass
elif SafeHtml._matchTags.has_key(tag):
if self._matchDict.has_key(tag):
self._matchDict[tag] = self._matchDict[tag] - 1
self.write_endtag (tag)
elif SafeHtml._safeTags.has_key(tag):
self.write_endtag (tag)
elif not self._extra_safe:
self.write_endtag (tag)
def close (self):
self._stripping = 0
for tag in self._matchDict.keys():
if self._matchDict[tag] > 0:
for x in range (self._matchDict[tag]):
self.write_endtag(tag)
PassSGMLParser.close(self)
def SafeHtmlString (s, really_safe=1, map_urls=None):
# fp = open("/tmp/safe_html.in", "w")
# fp.write(s)
# fp.close()
fp = StringIO()
parser = SafeHtml(fp, really_safe, map_urls=map_urls)
parser.feed (s)
parser.close ()
s = fp.getvalue()
# fp = open("/tmp/safe_html.out", "w")
# fp.write(s)
# fp.close()
return s