TỔNG QUAN VỀ MẠNG WLAN VÀ CÁC BIỆN PHÁP BẢO MẬT TRONG MẠNG WLAN

TỔNG QUAN VỀ MẠNG WLAN VÀ CÁC BIỆN PHÁP BẢO MẬT
TRONG MẠNG WLAN
1.1. Tổng quan về mạng WLAN
 !"
#!$%&'''()*+,,-$./0123"45.#
!"#6!$%+7%$.62898:61"
;"<.+
Những ưu điểm của mạng không dây:
- =>?2@AA5B5!"#CD;!E2%+
- =$DF6"@G!$@@FH!"#+
- IJK52L@3!+
- =$MN58@4"!.OK52LN5+
- IJP+
Nhược điểm của mạng không dây:
- QR65:@."45-S>T@@46+
- U$289G!$M#VW2"N
@;2G@J+
- UM#X#2-82YO2>Z
+++
 [6&!$%8OYDD54:D>\
2345Q]Q^"56_!&
`]&`^@D545N-!"#$6Na6
`Q'`Q'S5+U21-Q21
@%b6-235N@1-2c$
@<;>NN66-5B5X!"#L?L
, ,
NN6@6+[Q135B5<
XNH@V5b1456Va+
1.1.1. Kiến trúc mạng WLAN
()*+,,A!"a"D-21.#289d
C"D-e289fg@gfgg2892G

!3DPQQ+
[LV132896CV@<Q-5M
<2896CG-21NQ289!"#$S0h8:
#IDgIg+
[45F@0P'hg@g-'gg1G:
NfggV6D+U6"22LD.ii-
i5]]5i-N"DF!$%13G$A
"5@<e"DF!N@!$/02345+7;&fgg
fgg245+
jX8<2%k()*+,,23XV@<N5M
289>P\









1.1.2. Chế độ hoạt động
[6!$%1"262\]@&+
1.1.2.1. Kiểu Ad-hoc
l"262-!ab6!$!"C!"a"D
81PeNH6"5A"5@<$S
* *
N"DF`6 !$ %- !$V2" N"DF2F"
m5N!$%Q+










1.1.2.2. Kiểu Infrastructure
Các máy tính trong hệ thống mạng sử dụng một hoặc nhiều các thiết
bị định tuyến (wirelesss router) hay thiết bị thu phát (AP) để thực hiện các
hoạt động trao đổi dữ liệu với nhau và các hoạt động khác.
Trong chế độ này trạm không dây kết nối với mạng (thường là mạng
Ethernet) thông qua AP. Một tập các trạm kết nối với AP tạo lên một BSS
(Basic Service Set). Mỗi BSS được định danh bởi một BSSID (BSS
Identifier) có độ dài 6 byte tương ứng với địa chỉ MAC của AP.









1.1.2.3. Ca
́
c tha
̀
nh phâ
̀

n cơ ba
̉
n cu
̉
a WLAN
=
n

n
:D
o
$
p
8
q

p
5%
p
\
r r
• Q]Q\
p

n
D
s

p
2

o
!
n
$
n

p

n
D
s
!$%
s

@:
n

p
$
s

s
+Q
n

o
!
n
$
n

@:
n
$
s

s

n
%
@
p

n

o

o

n
58
q

s
8
q

n

n
D

s
!$%@
p

n
%+
• m\$
n
8Q88
n
?_-2
s

n

-U@
p

s
@
s
Ij`Q@
p

s
@
s
%
n
52

s
t
o
&Q2$
s

+
• _!&`&`\ 
s

s
-28:
s
8
o

s

s

8:
p

p
2M$
n
+`
s

n


s
S
n
5
s
@%
p
$
n
!
n

$
n
@
p
2
n
8
s

s
!
n
$
n
@:
n
$

s
Q$
s
_!
n
+
• u\
p
$
s
5%
p
S
s
-
s

n

s
5
n

n
t
n

s
2
q

S
2
p

n
2
o

n

p
5%
p
!$%
n

o
28:
s
t
n

s
+
1.1.3. Kiến trúc phân tầng của WLAN


 !"#$




%&&


'
((()*+,

#-

./
v#8D;!XR()*+h- ()*+,,DYM[`
@Qjw+
x x


0!"#$



%&&


'
((()*
1.1.3.1. Tầng PHY
U6M@4T- ()*+,,e9D !N\
]IgSg5g5Iggg\>5c5%26A"5+
]Sj55g5g5jgg\>5c>M+
]&\Y6+
a. DSSS

j62AK>5cH.2M5NPD?y5H
.>5cD?23NJ$8O+U62M-H.
2892GD"623!$50H.#+
b. FHSS
`$.AT>M->2M5N@2M2G1
z423S2FMAN5<+{6O
232M5N@2M5>62VM#+
1.1.3.2. Tầng MAC
UM.@02G!34528OG+g/0!{4
>41Nh2`g[5_`
@`g[|`+
vR`g[|`@.8\[6#G-2M1
}$8O!$%23hN2F.162G
~ ~
!$+"$8O.2DF"-6HN!>JL5
6W+!OJ21$S-66h.1
62G!$+f•N6OJW-G
62#G}!$#KG6VO23N
h2+
`N@.2LD..S>!$8O!$>L-!1
5B56G@<!>OJd;-86h>
8O95G6VG€.Oh>h2-
%A"N6;28OGe@45R
S"2FG+•25>2895N.-DP@4M[`13
G61DPH1!$5>DPNM:-2G21}W
2"J+U'-h22895N.DP6GA>
4h5D!+
1.1.4. Khuôn dạng các gói tin trong mạng WLAN
`N12"CM6289K5M[`PM[`6
[QI‚[QI‚+[QI‚212893h#

MQjw-62%289K5Mƒ5D„@ƒ„-6
Q`Q]QI‚+QM5D@5M!NV@Qjw/0
Iggg-jgg-…+7M}hhBNbMQjwQ`Q]QI‚-
21bM[`+
1.1.4.1. Các gói tin thuộc tầng vật lý


1!"-



##&

+&

23

QM5D5B5X5M2Mb-2YD1-
5B5/0!G````
† †
QM1;G$-50@!‡4>5c/0
MQjw+
a. FHSS:
QM5DY5M\
] ()Dh!}ND)@,5B5A
Q$;@2YD1@<Q21+
] gIgI,†D)))),,)),),,,,),\k
23DK2Mb
QMYr5M\
] QQ`Q]QI‚,*D\k2#Db

Q`Q]QI‚-5B5MQjwhN2F23!"ab
1+
] QgQ`QgxD\k889289V
1,L*[D|23G€.[QI‚
] j'`j'`!`m`,†D\5B5Xe
8OQ@Qg+
j5M5D@$GPR,[D|
b.DSSS:
QM5D\#jgg-88O:@gI1NF
)hr),,,,)),,,),)))))
QM\Yx5M
] g(D\k#223G[QI‚
)h)()*+,,P"2fQg=,[D|
)h,x()*+,,P"2ˆQg=*[D|
)hr‰()*+,,DP"2ˆQg=~-~[D|
)h†'()*+,,DP"2ˆQg=,,[D|
] g@(D\8€23V
] ,† D\ k 2 HD•D b  2 !Š
[QI‚-5B5MQjwhN2F23#b+
‰ ‰
] j'`j'`!`m`,†D-5B5e
8Og-g@@+
1.1.4.2 Các gói tin thuộc tầng MAC
UM[`1r6\€.-2G!3V23e9
456mUg-`Ug-`=-…@V23S>T@.!"#@<
Q-2YD1-RA+
I8<2%<.6cSN@N8O}2cV
R?b+=H8<<;bM[`
*rx†‰D+
a. Frame tổng quát



4!"-



##-
'
5


• QMY‰8O\2%5M5R65;@X11;G
R?
`\,,8O-@<*D


)!"-

6,

2
 Q@\$)@<@.*D
 U5@gD5\D3Jr6@R?ba*‹xD
] U5\ˆ>T\))
] 7G!3\),
] I€.\,)
 gD5
] mUg\,),,
] `Ug\,,))
( (

] `=\,,),
UIg@Ig\IgŒIDg@Q
UIg,D\2FkQ289/2"
Ig,D\2FkQh;5N
- [\,"€.2895%26-)"€.!$
2895%26L215%26#V+
- m\,"289G6+
- Q_[\,"6P"2"!.?89-)"
6P"262+7"CQ-$P"262+
- [I\289V23S>T?89+789/0DPQ23k
!N22898€6+U613S"2F/
0$23MN!NL3S"26
2+
- 'Q\k5M€.289•1D•4N'Q+
- Ž\",-6!$2895B5/!3+
I&I*D
U8O1T{-50@61\
] •<!3NP"2"!.?89-X21&Ib
6L&I&I
] •<N!N-21NF289V23H•_!
•
U8O
,\D
*\D5N
r\/0DPD23
x\/0IgIDg
~6\
] fgg&I\2F;efgg+
• •
] II\2Fk[`b2H2"#1

[gI‚
] gg\2Fk[`bD5N[gI‚+
] m@m\.!$%b6'
] UU\k/0Ig+
U8OS


7!"-

6,

582
g/0235%2@4595N
`N15%26V1VSD-
8O?e289G2
"!$2895%26XDŒ)
• D\R€.G2-2G!3@S>T
!$1€.+
• `g`!gS\`m`r*D-23!3NH@yb
+
b. Frame điều khiển
U5M`-8OUIgDKDD•)
`NH\
• mUgmS289V23M2895B5G€
.


*!"-




##9:/
] m2FkbND4b€.LS>T
"5
] U2Fkb6GmUg
• `Ug`Ug232Le8<!G23G€.
,) ,)


!"-



##;:/
m2Fk6Y#8OUbmUg
• `=\DN2•4€.


!"-



##;"
m2Fk6Y-2"C8O*b€.L
S>T8<21+
c. Frame quản lý
`1
n
1S>T\
] f\Q8:

p
h8
o
D2
o
$D
n
8
s

n
?
s

o

t
p
 @:
n
8
q
$85-gg&I @
p
 
n
$
n
!
n

+

q
!
o

n
!
p

n
@
p
D
8$
s
::
o
2
o

s
Q
p

p
5
p
:
s

5%
n
@
s
!
n
$
n
+
] QDmS|QDm5\g8
o
5DS!%
p
D
n

$@
p
$
s
!
n
+QD5
p
8
o

o
@
p

$
p
8
q

$
n

o

n
8$
n
2$
s

p
8
q

s
-+++
] mS|m5\S
$
p
8
q
$@
p
&`-gg&I

o

s

p
$
n
!
n
$
n
:
n
-
28:
s
8
o
8
p
2
n
Q2
o
%
p
28:
s
!
n

$
n
+g!%
s
28:
s


p
Q8
o
2
n
52
o
%
n
5%
s
!
n
$
n
-
%
n
5D$
s
:
n

@
p
h%8
s
$
s
&I!
n
$
n
+
] mmS|mm5\mS
28:
s

p
!:
p
!
o
!
n
$
n
@:
n
Q
s

s

@
p
t
p
%
n
$
s
Q
!
n

n
t
n

s
D
s
:-
q
8
o

p
2
n
Q:
n
+Q

,, ,,
:
n
8
o

s
5%
n
5%
s
!
n
$
n
-2
n

q
5$
n
:
s
5@
p
8
o
8
q


n

o
@%q
p
D$
s
2
s

o
Q8:
n
2
n
+
] I\g
q
8
o
:
n
$
s
!
n
!

n
$

n
8
p
!
n
$
n
@:
n
2
n
+•t
n

s
-$
s
_8:
n
!
8
p

s
2$
s

n

o

8
o
2
o
D
n
8:
n
QD
n
+
g2
n
Q
n

o
8
p
@
s
%
n
55
n
D$
s
:
n
@

p
:
q
D
o
&`!
o
D
o
!
n

$
n
+
] I\g8
o

p
2
n
!
n
!
n
$
n
!
n



n
!
n
$
n

p
+
1.1.5. Một số chuẩn WLAN hiện hành
1.1.5.1. Chuẩn 802.11b (Chuẩn B)
`N"DF 62PM#*+xvj‘@13G€
.@<#2#2,,[D556@C,))2",~)Cr~B
2"x~B
1.1.5.2. Chuẩn 802.11a (Chuẩn A)
`N"DF 62PM#~vj‘@13G€
.@<#2#2~x[D58k56@!>‰~!>*~
B
1.1.5.3. Chuẩn 802.11g (Chuẩn G)
`N"DF62PVM#8N"DF f-
ae9#2G€.;5~M@< f@<V
56@5b1+`N"DF f@ v8:H@<
-M8T!D6WN"DF f@ v@<
XN"DF}62 1#2;5:+
1.1.5.4. Chuẩn 802.11c
` !$289/0G-1289V23h%AM#
@<Nb()*+,,PM`+
1.5.5. Chuẩn 802.11d
,* ,*
` 289Dc@<02HS#"1N6()*+,,2F

58:+15B5N"DF!NbN•!N13
2c$8OM#+
1.15.6. Chuẩn 802.11i
` 23>.HD>4GS>T@5%5#
!1-•1@RA+` /0 •1"'g
@'5g+
1.1.5.7. Chuẩn 802.11Ir
` /0H.Y6PMQjw+
1.1.5.8. Home RF
7895N3DPjmS!v5jmv+
g/0RgQgQ5B5G
1@€.O@!{4!$%/02X-889
26C,-†[D|2"*)[D|+
:<=;!/0RUI[UI@[523
G1@VR`g[|``g[5|
`@23G€.+
:<>?!jm62>M*-xvj‘-/0!{4>
5c>Mjgg@<~)5|+
1.1.5.9. HiperLan (High Performance local area network)
'Ug&5N3j5,,••†@j5*,•••236@<
 ()*+,,b[‡+`> 2G;5€2LH@!>?
8:28:N +j5,62P>M~-,~~-r)vj‘-
$89*r+~[D|-DN!H62!>~)+j5*62
  >  ~vj‘-  /  0  !{  4  ŽI[  Ž  S  I@
[5h-$89~x[D|+
1.2. Các giải pháp bảo mật trong mạng WLAN
,r ,r
1.2.1. Các dạng tấn công
U1G6;$-211@!313A
.289GN!N-8@G:D>X16;$

H;$DF25@!@;$b2@!


!



+$

&

-
1.2.1.1. Tấn công bị động (passive attack)
U6;$-8289hNA45@6
bD6+!!$2cN$2.5-ak"
8$6@C211N$@G6bD6+
I6;$289L2LD.Ha-a13JQ
6O@DYNH289DF@
5MG2LD.23X!"Q+€289DF?
8<H5B58$6C!>Nh!@A5b
1  b  Q+  `1    6  \  6  DF  2  =-  -
QD…!$236;@"-M8!$DF5N.@6b
2D-D13DF5N.!-a/N
ƒ5D  S„+  U  21  k  1  D  6  2    $  8O
,x ,x