howtos

HTTP connections unlimited

Ever thought about how to craft a HTTP connection? Without tools such as curl or wget. For the purposes of testing some edge case of the HTTP1.1 protocol. Let’s use the tools netcat (nc) and openssl for this purpose.

without TLS

Plain HTTP request, POST to google.com port 80, NOTE that we target an IP address (the google.com bit is specified in the header Host in the request body):

#!/bin/bash

HostDomain="google.com" ; \
HostIP="216.58.215.110" ; \
HostPort="80" ; \
dataToPost='{ data: "" }' ; \
dataLen=$(expr length "${dataToPost}" ) ; \
  ( printf "POST /api HTTP/1.1\r\n" ; \
    printf "Host: %s\r\n" "${HostDomain}" ; \
    printf "User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0\r\n" ; \
    printf "Connection: close\r\n" ; \
    printf "Content-Length: %d\r\n" "$((dataLen+1))" ; \
    printf "Content-Type: application/x-www-form-urlencoded\r\n" ; \
    printf "\r\n" ; \
    printf "%s" "${dataToPost}" ; \
    sleep 1.5 ) | nc ${HostIP} ${HostPort}

with TLS

HTTPs request (using certificates), POST to google.com port 443, NOTE that we target an IP address (the google.com bit is specified in the header Host in the request body):

#!/bin/bash

HostDomain="google.com" ; \
HostIP="216.58.215.110" ; \
HostPort="443" ; \
dataToPost='{ data: "" }' ; \
dataLen=$(expr length "${dataToPost}" ) ; \
  ( printf "POST /test HTTP/1.1\r\n" ; \
    printf "Host: %s\r\n" "${HostDomain}" ; \
    printf "User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0\r\n" ; \
    printf "Connection: close\r\n" ; \
    printf "Content-Length: %d\r\n" "$((dataLen+1))" ; \
    printf "Content-Type: application/x-www-form-urlencoded\r\n" ; \
    printf "\r\n" ; \
    printf "%s" "${dataToPost}" ; \
    sleep 1.5 ) | openssl s_client -connect ${HostIP}:${HostPort}

some notes

In both of the above commands - you can see each line ends with ; \. This makes it possible to just copy the multi-line Bash snippet, and paste into a terminal. It will run just fine (as long as your shell is bash).

Also, note the explicit new line printf "\r\n" being sent to the server. This is part of the HTTP standard, which implies that after a new line, there will be no more headers, and only the request body will follow.

about these howtos

This howto is part of a larger collection of howtos maintained by the author (mostly for his own reference). The source code for the current howto in plain Markdown is available on GitHub. If you have a GitHub account, you can jump straight in, and suggest edits or improvements via the link at the bottom of the page (Improve this page).

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