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137 lines
4.2 KiB
Markdown
137 lines
4.2 KiB
Markdown
Identifying Application Protocols
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=================================
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The three easiest protocols to identify are FTP, SMTP, and HTTP. These
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also happen to be some of the most common protocols in use.
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In these examples, lines either begin with `C:` (client) or `S:`
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(server).
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FTP (control channel only)
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--------------------------
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S: 220 ScumFTPD
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C: USER anonymous
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S: 331 Anonymous login ok, use email address as password
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C: PASS joe@example.org
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S: 230-Welcome to the FTP server.
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S: 230 Anonymous access granted, restrictions apply.
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C: PASV
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S: 227 Entering Passive Mode (152,46,7,80,196,9).
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C: LIST
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S: 150 Opening ASCII mode data connection for file list
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S: 226 Transfer complete
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C: QUIT
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S: 221 Goodbye
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SMTP
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----
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S: 220 mail.example.com ESMTP MushMail 1.3
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C: EHLO bub
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S: 250-Hi there
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S: 250-VRFY
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S: 250 8BITMIME
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C: MAIL FROM: bob@example.com
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S: 250 Recipient address accepted
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C: RCPT TO: alice@example.com
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S: 250 Sender accepted
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C: DATA
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S: 354 End data with \n.\n
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C: From: Santa Claus <santa@workshop.np>
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C: To: Alice <alice@example.com>
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C: Subject: ho ho ho
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C:
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C: You've been a good girl this year, Alice.
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C: .
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S: 250 Message accepted for delivery
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C: QUIT
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S: 221 Goodbye
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Note here that the `MAIL FROM` is different from the `From:` header
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field. `MAIL FROM` and `RCPT TO` are called the “envelope” and are what
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the mail server looks at. The `From:` header field is merely advisory,
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and can be trivially spoofed!
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HTTP
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----
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C: GET /path/to/resource.html HTTP/1.1
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C: Host: www.example.com
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C: User-Agent: Mozilla/2.0 (Galeon 1.0; Unicos; 2.3)
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C: Connection: Close
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C:
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S: HTTP/1.1 200 OK
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S: Server: CERN httpd 1.2
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S: Date: Fri, 22 May 2009 14:34:12 GMT
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S: Last-Modified: Wed, 20 May 2009 10:33:42 GMT
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S: Content-length: 20
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S:
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S: <title>hi</title>hi.
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The first line of an HTTP connection consists of:
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METHOD PATH VERSION
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`PATH` is the path to the resource being requested. It usually begins
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with `/`, but if the client is trying to use the server as an HTTP
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proxy, it will be a full URL.
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`VERSION` is the version of HTTP in use. It always begins with `HTTP/`
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and ends with major and minor version numbers, separated by a period.
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Many protocols are "HTTP-like", and provide a version beginning with
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something other than `HTTP/'. Although they may look like HTTP, they
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are not truly HTTP connections.
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`METHOD` is typically either `GET`, `HEAD`, or `POST`, but may also be
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`OPTIONS`, `PUT`, `DELETE`, `TRACE`, `CONNECT`, or any number of
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extensions.
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The `CONNECT` method is used to proxy traffic through the HTTP server.
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Typically this is done by web browsers set up to use HTTP proxies for
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HTTPS (HTTP over SSL), but is worth noting since it can also be used by
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malware or to skirt firewall policies. For instance:
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CONNECT us.undernet.org:6667 HTTP/1.0
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Would open an IRC connection to the Undernet IRC network. If your
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policies disallow connecting to IRC, this demonstrates a possibly
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successful attempt to skirt firewall rules.
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Question
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========
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Sometimes as an analyst, you only get the first few dozen bytes of a
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conversation, and you may not even get an indication of whether the
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client or server spoke first.
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You have been given the first line sent in 16 different connections and
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asked to determine which warrant further investigation. You need to
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rule out things that are clearly not the first line of HTTP, SMTP, or
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FTP.
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The answer for this page is the list of protocols *not described on this
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page*, ordered from lowest (1) to highest (F). The answer should be of
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the form "1,2,3,7,8,A,B,C".
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1: GET / HTTP/1.1
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2: +OK example.com server ready
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3: 220 mailrelay.example.com ESMTP Postfix 2.3.3/Bantu
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4: QUERY: //SYSTEMS/5B669A24
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5: POST /depts/research/beekeeping/survey.php?token=83927400 HTTP/1.1
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6: NICK rutabaga
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7: HEAD /content/images/ap-5823.jpg HTTP/1.0
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8: -l jsmith
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9: CONNECT example.com:996 HTTP/1.1
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A: USER robot robot robot :robot
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B: EHLO example.com
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C: Subject: all-employee notice
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D: * OK [CAPABILITY STARTTLS] example.com server Innova ready
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E: TRACE / HTTP/1.1
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F: GET / ICAP/1.1
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