Mail System 介紹--SMTP

實例介紹 1

我們由 venus 這部機器 telnet eesol00 port 25, 直接以 SMTP 將信件 header 和內容告訴 eesol00 上的 TA, 請它代為轉送

步驟 (藍色部份為 user keyin)

Tung@venus:~> telnet eesol01 25
Trying 140.116.49.11...
Connected to eesol01.
Escape character is '^]'.
220 eesol01.ee.ncku.edu.tw ESMTP Sendmail 8.8.8/8.8.8; Thu, 21 May 1998 20:45:51
 +0800 (CST)
helo venus
250 eesol01.ee.ncku.edu.tw Hello Tung@venus.ee.ncku.edu.tw [140.116.72.74], pleased to meet you
mail from: <Tung@eesol01.ee.ncku.edu.tw>
250 <Tung@eesol01.ee.ncku.edu.tw>... Sender ok
rcpt to: <Tung@turtle.ee.ncku.edu.tw>
250 <Tung@turtle.ee.ncku.edu.tw>... Recipient ok
data
354 Enter mail, end with "." on a line by itself
mail from telnet eesol01 port 25
.
250 UAA02587 Message accepted for delivery
quit

在 turtle 收到的信件如下

From Tung@eesol01.ee.ncku.edu.tw  Thu May 21 20:36:29 1998
Received: from eesol01.ee.ncku.edu.tw (eesol01 [140.116.49.11])
        by turtle.ee.ncku.edu.tw (8.8.5/8.8.5) with ESMTP id UAA05162
        for <Tung@turtle.ee.ncku.edu.tw>; Thu, 21 May 1998 20:36:29 +0800 (CST)
Received: from venus (Tung@venus.ee.ncku.edu.tw [140.116.72.74])
        by eesol01.ee.ncku.edu.tw (8.8.8/8.8.8) with SMTP id UAA02587
        for <Tung@turtle.ee.ncku.edu.tw>; Thu, 21 May 1998 20:46:32 +0800 (CST)
Date: Thu, 21 May 1998 20:46:32 +0800 (CST)
From: staff <Tung@eesol01.ee.ncku.edu.tw>
Message-Id: <199805211246.UAA02587@eesol01.ee.ncku.edu.tw>

mail from telnet eesol01 port 25
 
 

實例介紹 2
 
在上面的例子我們發現以 telnet port 25 的方式寄信,

fromhost (helo 後面跟的 domainname)
mail from (寄信人)
rcpt to (收信人)

都可以隨便打, 與自己真正的身份無關....這是不是會造成假信件的產生呢?
考慮跟例一同樣的組態, 不過這次我們給一些假資料試看看
 
Tung@venus:~> telnet eesol01 25
Trying 140.116.49.11...
Connected to eesol01.
Escape character is '^]'.
220 eesol01.ee.ncku.edu.tw ESMTP Sendmail 8.8.8/8.8.8; Thu, 21 May 1998 20:50:07
 +0800 (CST)
helo fake.domain.in.helo
250 eesol01.ee.ncku.edu.tw Hello Tung@venus.ee.ncku.edu.tw [140.116.72.74], pleased to meet you
mail from: <root@eesol01.ee.ncku.edu.tw>
250 <root@eesol01.ee.ncku.edu.tw>... Sender ok
rcpt to: <Tung@turtle.ee.ncku.edu.tw>
250 <Tung@turtle.ee.ncku.edu.tw>... Recipient ok
data
354 Enter mail, end with "." on a line by itself
fake root mail from telnet eesol01 port 25
.
250 UAA02592 Message accepted for delivery
quit

在 turtle 收到的信件如下

From root@eesol01.ee.ncku.edu.tw  Thu May 21 20:41:35 1998
Received: from eesol01.ee.ncku.edu.tw (eesol01 [140.116.49.11])
        by turtle.ee.ncku.edu.tw (8.8.5/8.8.5) with ESMTP id UAA05191
        for <Tung@turtle.ee.ncku.edu.tw>; Thu, 21 May 1998 20:41:35 +0800 (CST)
Received: from fake.domain.in.helo (Tung@venus.ee.ncku.edu.tw [140.116.72.74])
        by eesol01.ee.ncku.edu.tw (8.8.8/8.8.8) with SMTP id UAA02592
        for <Tung@turtle.ee.ncku.edu.tw>; Thu, 21 May 1998 20:51:23 +0800 (CST)
Date: Thu, 21 May 1998 20:51:23 +0800 (CST)
From: Super-User <root@eesol01.ee.ncku.edu.tw>
Message-Id: <199805211251.UAA02592@eesol01.ee.ncku.edu.tw>

fake root mail from telnet eesol01 port 25

藍色部份就是當初我們 key in 的部份, 注意標紅色的地方,清楚地顯示這封信是由 Tung@venus.ee.ncku.edu.tw 所送出, 雖然我們 mail from 偽裝成 root@eesol00.ee.ncku.edu.tw, fromhost 也假裝一個不存在的機器名稱, 但是還是漏出馬腳囉....