Package org.apache.tika.sax

Class SecureContentHandler

java.lang.Object

org.xml.sax.helpers.DefaultHandler

org.apache.tika.sax.ContentHandlerDecorator

org.apache.tika.sax.SecureContentHandler

All Implemented Interfaces:

ContentHandler, DTDHandler, EntityResolver, ErrorHandler

public class SecureContentHandler
extends ContentHandlerDecorator

Content handler decorator that attempts to prevent denial of service attacks against Tika parsers.

Currently this class simply compares the number of output characters to to the number of input bytes and keeps track of the XML nesting levels. An exception gets thrown if the output seems excessive compared to the input document. This is a strong indication of a zip bomb.

Since:

Apache Tika 0.4

See Also:

TIKA-216

Constructor Summary

Constructors

Constructor	Description
SecureContentHandler(ContentHandler handler, TikaInputStream stream)	Decorates the given content handler with zip bomb prevention based on the count of bytes read from the given counting input stream.

Method Summary

Modifier and Type	Method	Description
protected void	advance(int length)	Records the given number of output characters (or more accurately UTF-16 code units).
void	characters(char[] ch, int start, int length)
void	endElement(String uri, String localName, String name)
long	getMaximumCompressionRatio()	Returns the maximum compression ratio.
int	getMaximumDepth()	Returns the maximum XML element nesting level.
int	getMaximumPackageEntryDepth()	Returns the maximum package entry nesting level.
long	getOutputThreshold()	Returns the configured output threshold.
void	ignorableWhitespace(char[] ch, int start, int length)
void	setMaximumCompressionRatio(long ratio)	Sets the ratio between output characters and input bytes.
void	setMaximumDepth(int depth)	Sets the maximum XML element nesting level.
void	setMaximumPackageEntryDepth(int depth)	Sets the maximum package entry nesting level.
void	setOutputThreshold(long threshold)	Sets the threshold for output characters before the zip bomb prevention is activated.
void	startElement(String uri, String localName, String name, Attributes atts)
void	throwIfCauseOf(SAXException e)	Converts the given SAXException to a corresponding TikaException if it's caused by this instance detecting a zip bomb.

Methods inherited from class org.apache.tika.sax.ContentHandlerDecorator

endDocument, endPrefixMapping, error, fatalError, handleException, processingInstruction, setContentHandler, setDocumentLocator, skippedEntity, startDocument, startPrefixMapping, toString, warning

Methods inherited from class org.xml.sax.helpers.DefaultHandler

notationDecl, resolveEntity, unparsedEntityDecl

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SecureContentHandler

public SecureContentHandler(ContentHandler handler,
                            TikaInputStream stream)

Decorates the given content handler with zip bomb prevention based on the count of bytes read from the given counting input stream. The resulting decorator can be passed to a Tika parser along with the given counting input stream.

Parameters:

handler - the content handler to be decorated

stream - the input stream to be parsed

Method Detail

getOutputThreshold

public long getOutputThreshold()

Returns the configured output threshold.

Returns:

output threshold

setOutputThreshold

public void setOutputThreshold(long threshold)

Sets the threshold for output characters before the zip bomb prevention is activated. This avoids false positives in cases where an otherwise normal document for some reason starts with a highly compressible sequence of bytes.

Parameters:

threshold - new output threshold

getMaximumCompressionRatio

public long getMaximumCompressionRatio()

Returns the maximum compression ratio.

Returns:

maximum compression ratio

setMaximumCompressionRatio

public void setMaximumCompressionRatio(long ratio)

Sets the ratio between output characters and input bytes. If this ratio is exceeded (after the output threshold has been reached) then an exception gets thrown.

Parameters:

ratio - new maximum compression ratio

getMaximumDepth

public int getMaximumDepth()

Returns the maximum XML element nesting level.

Returns:

maximum XML element nesting level

setMaximumDepth

public void setMaximumDepth(int depth)

Sets the maximum XML element nesting level. If this depth level is exceeded then an exception gets thrown.

Parameters:

depth - maximum XML element nesting level

getMaximumPackageEntryDepth

public int getMaximumPackageEntryDepth()

Returns the maximum package entry nesting level.

Returns:

maximum package entry nesting level

setMaximumPackageEntryDepth

public void setMaximumPackageEntryDepth(int depth)

Sets the maximum package entry nesting level. If this depth level is exceeded then an exception gets thrown.

Parameters:

depth - maximum package entry nesting level

throwIfCauseOf

public void throwIfCauseOf(SAXException e)
                    throws TikaException

Converts the given SAXException to a corresponding TikaException if it's caused by this instance detecting a zip bomb.

Parameters:

e - SAX exception

Throws:

TikaException - zip bomb exception

advance

protected void advance(int length)
                throws SAXException

Records the given number of output characters (or more accurately UTF-16 code units). Throws an exception if the recorded number of characters highly exceeds the number of input bytes read.

Parameters:

length - number of new output characters produced

Throws:

SAXException - if a zip bomb is detected

startElement

public void startElement(String uri,
                         String localName,
                         String name,
                         Attributes atts)
                  throws SAXException

Specified by:

startElement in interface ContentHandler

Overrides:

startElement in class ContentHandlerDecorator

Throws:

SAXException

endElement

public void endElement(String uri,
                       String localName,
                       String name)
                throws SAXException

Specified by:

endElement in interface ContentHandler

Overrides:

endElement in class ContentHandlerDecorator

Throws:

SAXException

characters

public void characters(char[] ch,
                       int start,
                       int length)
                throws SAXException

Specified by:

characters in interface ContentHandler

Overrides:

characters in class ContentHandlerDecorator

Throws:

SAXException

ignorableWhitespace

public void ignorableWhitespace(char[] ch,
                                int start,
                                int length)
                         throws SAXException

Specified by:

ignorableWhitespace in interface ContentHandler

Overrides:

ignorableWhitespace in class ContentHandlerDecorator

Throws:

SAXException