Class HTMLSanitizer
object --+
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HTMLSanitizer
A filter that removes potentially dangerous HTML tags and attributes
from the stream.
>>> from genshi import HTML
>>> html = HTML('<div><script>alert(document.cookie)</script></div>')
>>> print html | HTMLSanitizer()
<div/>
The default set of safe tags and attributes can be modified when the filter
is instantiated. For example, to allow inline style attributes, the
following instantation would work:
>>> html = HTML('<div style="background: #000"></div>')
>>> sanitizer = HTMLSanitizer(safe_attrs=HTMLSanitizer.SAFE_ATTRS | set(['style']))
>>> print html | sanitizer
<div style="background: #000"/>
Note that even in this case, the filter does attempt to remove dangerous
constructs from style attributes:
>>> html = HTML('<div style="background: url(javascript:void); color: #000"></div>')
>>> print html | sanitizer
<div style="color: #000"/>
This handles HTML entities, unicode escapes in CSS and Javascript text, as
well as a lot of other things. However, the style tag is still excluded by
default because it is very hard for such sanitizing to be completely safe,
especially considering how much error recovery current web browsers perform.
Warning:
Note that this special processing of CSS is currently only applied to
style attributes, not style elements.
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__init__(self,
safe_tags=frozenset([ ' a ' , ' abbr ' , ' acronym ' , ' address ' , ' area ' , ' b ' , ' bi ... ,
safe_attrs=frozenset([ ' abbr ' , ' accept ' , ' accept-charset ' , ' accesskey ' , ' a ... ,
safe_schemes=frozenset([ None, ' file ' , ' ftp ' , ' http ' , ' https ' , ' mailto ' ]) ,
uri_attrs=frozenset([ ' action ' , ' background ' , ' dynsrc ' , ' href ' , ' lowsrc ' , ... )
Create the sanitizer. |
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__call__(self,
stream)
Apply the filter to the given stream. |
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bool
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is_safe_uri(self,
uri)
Determine whether the given URI is to be considered safe for
inclusion in the output. |
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list
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sanitize_css(self,
text)
Remove potentially dangerous property declarations from CSS code. |
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Inherited from object :
__delattr__ ,
__getattribute__ ,
__hash__ ,
__new__ ,
__reduce__ ,
__reduce_ex__ ,
__repr__ ,
__setattr__ ,
__str__
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SAFE_TAGS = frozenset([ ' a ' , ' abbr ' , ' acronym ' , ' address ' , ' are ...
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SAFE_ATTRS = frozenset([ ' abbr ' , ' accept ' , ' accept-charset ' , ' a ...
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SAFE_SCHEMES = frozenset([ None, ' file ' , ' ftp ' , ' http ' , ' https ' ...
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URI_ATTRS = frozenset([ ' action ' , ' background ' , ' dynsrc ' , ' href ...
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safe_tags
The set of tag names that are considered safe.
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safe_attrs
The set of attribute names that are considered safe.
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uri_attrs
The set of names of attributes that may contain URIs.
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safe_schemes
The set of URI schemes that are considered safe.
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Inherited from object :
__class__
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__init__(self,
safe_tags=frozenset([ ' a ' , ' abbr ' , ' acronym ' , ' address ' , ' area ' , ' b ' , ' bi ... ,
safe_attrs=frozenset([ ' abbr ' , ' accept ' , ' accept-charset ' , ' accesskey ' , ' a ... ,
safe_schemes=frozenset([ None, ' file ' , ' ftp ' , ' http ' , ' https ' , ' mailto ' ]) ,
uri_attrs=frozenset([ ' action ' , ' background ' , ' dynsrc ' , ' href ' , ' lowsrc ' , ... )
(Constructor)
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Create the sanitizer.
The exact set of allowed elements and attributes can be configured.
- Parameters:
safe_tags - a set of tag names that are considered safe
safe_attrs - a set of attribute names that are considered safe
safe_schemes - a set of URI schemes that are considered safe
uri_attrs - a set of names of attributes that contain URIs
- Overrides:
object.__init__
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__call__(self,
stream)
(Call operator)
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Apply the filter to the given stream.
- Parameters:
stream - the markup event stream to filter
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Determine whether the given URI is to be considered safe for
inclusion in the output.
The default implementation checks whether the scheme of the URI is in
the set of allowed URIs (safe_schemes).
>>> sanitizer = HTMLSanitizer()
>>> sanitizer.is_safe_uri('http://example.org/')
True
>>> sanitizer.is_safe_uri('javascript:alert(document.cookie)')
False
- Parameters:
- Returns:
bool
True if the URI can be considered safe, False otherwise
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Remove potentially dangerous property declarations from CSS code.
In particular, properties using the CSS url() function with a scheme
that is not considered safe are removed:
>>> sanitizer = HTMLSanitizer()
>>> sanitizer.sanitize_css(u'''
... background: url(javascript:alert("foo"));
... color: #000;
... ''')
[u'color: #000']
Also, the proprietary Internet Explorer function expression() is
always stripped:
>>> sanitizer.sanitize_css(u'''
... background: #fff;
... color: #000;
... width: e/**/xpression(alert("foo"));
... ''')
[u'background: #fff', u'color: #000']
- Parameters:
text - the CSS text; this is expected to be unicode and to not
contain any character or numeric references
- Returns:
list
- a list of declarations that are considered safe
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SAFE_TAGS
- Value:
frozenset([ ' a ' ,
' abbr ' ,
' acronym ' ,
' address ' ,
' area ' ,
' b ' ,
' big ' ,
' blockquote ' ,
...
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SAFE_ATTRS
- Value:
frozenset([ ' abbr ' ,
' accept ' ,
' accept-charset ' ,
' accesskey ' ,
' action ' ,
' align ' ,
' alt ' ,
' axis ' ,
...
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SAFE_SCHEMES
- Value:
frozenset([ None, ' file ' , ' ftp ' , ' http ' , ' https ' , ' mailto ' ])
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URI_ATTRS
- Value:
frozenset([ ' action ' , ' background ' , ' dynsrc ' , ' href ' , ' lowsrc ' , ' src ' ])
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