Wednesday, November 23, 2011

ngrep2curl - How to replay a browser web request


Many times, I found myself downloading a file twice because Cookies or some other required browser headers prevent curl from doing a direct download from the command line.

To simplify this process, I wrote a script that:
1) Listens on port 80 to grab the http headers for a download on a browser
2) Generates a curl command using the captured headers.

Old workflow (file transfered twice):
Web Browser -> browse to file -> download to local machine
sftp to remote server

New workflow (file transfered just once):
run ngrep2curl on local machine
Web Browser -> browse to file -> download just the beginning of the file -> cancel download
run the generated curl command on remote server

#!/bin/sh
ngrep port 80 -Wbyline |grep -vE '^#|^T '|head -20|sed 's/\.$//'|awk '/GET/{url=$2} /Host:/{host=$2} /User-Agent:/{gsub("User-Agent: ","");ua=$0} /Cookie:/{gsub("Cookie: ","");cookie=$0} /Referer:/{gsub("Referer: ","");ref=$0} /Accept:/{accept=$0} END{print "curl -L","\x27"host url"\x27","-A","\""ua"\"","-b\""cookie"\"","-e \x27"ref"\x27","-H","\x27"accept"\x27"}'
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