2.3.2. Program stacking

When stacking a program, the data received by a proxy within a protocol is directed to the standard input. Arbitrary commands (including command line scripts, or applications) working from the standard input can be run on this data stream. The original proxy obtains the processed data back from the standard output. When stacking a command, the command to be called has to be included in the proper stack attribute of the proxy between double-quotes. This is illustrated in the following example.

Example 2.7. Program stacking in HTTP

In this example a simple 'sed' (stream editor) command is stacked into the HTTP proxy to replace all occurrences of 'http' to 'https', thus securing the HTTP connections on one side of the firewall. 

class MyHttp(HttpProxy):
	def config(self):
		HttpProxy.config(self)
		self.response_stack["GET"] = /
		(HTTP_STK_DATA, (Z_STACK_PROGRAM, "/bin/sed '/http:/s//https:/g'"))
Previous Up Next
 Home