Howto HTTP

Le procotole HTTP (HyperText Transfer Protocol) est un protocole client/serveur de niveau 7 s'appuyant par convention sur la couche de transport TCP et le port 80. Sa version sécurisée est HTTPS qui s'appuye en plus sur la couche SSL/TLS.

Comprendre les différentes versions de HTTP grâce à telnet

HTTP/1.0

La version la plus simple, ll'entête Host: est facultatif :

$ telnet www.debian.org 80
Trying 5.153.231.4...
Connected to www.debian.org.
Escape character is '^]'.
GET / HTTP/1.0

HTTP/1.1 200 OK
Date: Wed, 05 Oct 2016 02:09:37 GMT
Server: Apache
Last-Modified: Fri, 08 Jan 2016 22:27:31 GMT
ETag: "1d8-528da17d9b160"
Accept-Ranges: bytes
Content-Length: 472
Vary: Accept-Encoding
X-Clacks-Overhead: GNU Terry Pratchett
Connection: close
Content-Type: text/html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
[...]
Connection closed by foreign host.

HTTP/1.1

L'entête Host: est obligatoire :

$ telnet www.debian.org 80
Trying 5.153.231.4...
Connected to www.debian.org.
Escape character is '^]'.
GET / HTTP/1.1
Host: www.debian.org

HTTP/1.1 200 OK
Date: Wed, 05 Oct 2016 02:11:37 GMT
Server: Apache
Content-Location: index.en.html
Vary: negotiate,accept-language,Accept-Encoding
TCN: choice
Last-Modified: Tue, 04 Oct 2016 15:27:56 GMT
ETag: "3baf-53e0bb4711c9f"
Accept-Ranges: bytes
Content-Length: 15279
Cache-Control: max-age=86400
Expires: Thu, 06 Oct 2016 02:11:37 GMT
X-Clacks-Overhead: GNU Terry Pratchett
Connection: close
Content-Type: text/html
Content-Language: en

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
[...]
Connection closed by foreign host.

HTTPS

On gère le tunnel SSL avec openssl puis tout est en clair :

$ openssl s_client -host www.debian.org -port 443
CONNECTED(00000003)
depth=3 C = SE, O = AddTrust AB, OU = AddTrust External TTP Network, CN = AddTrust External CA Root
verify return:1
depth=2 C = US, ST = New Jersey, L = Jersey City, O = The USERTRUST Network, CN = USERTrust RSA Certification Authority
verify return:1
depth=1 C = FR, ST = Paris, L = Paris, O = Gandi, CN = Gandi Standard SSL CA 2
verify return:1
depth=0 OU = Domain Control Validated, OU = Gandi Standard SSL, CN = debian.org
verify return:1
---
Certificate chain
 0 s:/OU=Domain Control Validated/OU=Gandi Standard SSL/CN=debian.org
   i:/C=FR/ST=Paris/L=Paris/O=Gandi/CN=Gandi Standard SSL CA 2
 1 s:/C=FR/ST=Paris/L=Paris/O=Gandi/CN=Gandi Standard SSL CA 2
[...]
    Start Time: 1475633567
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---
GET / HTTP/1.0

HTTP/1.1 200 OK
Date: Wed, 05 Oct 2016 02:12:56 GMT
Server: Apache
[...]

HTTP/2.0

https://fr.wikipedia.org/wiki/Hypertext_Transfer_Protocol/2

Outils

HEAD/GET/POST

# apt install libwww-perl

Voir http://gcolpart.evolix.net/blog21/faire-du-postgethead-en-ligne-de-commande/

cURL

Voir TipsCurl

ab : apache bench

# apt install apache2-utils

Utilisation :

$ ab -n 1000 -c 100 -l http://127.0.0.1/helloworld.txt

-n : nombre de requêtes
-c : nombre de requêtes effectuées en simultané
-l : option importante qui tolère la variation de la réponse du serveur (si non, les requêtes seront notées en Failed requests)
-k : active le HTTP KeepAlive

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