alexandre-bartel/cve-2018-20343PoC for CVE-2018-20343
This is a PoC for CVE-2018-20343, a vulnerability in Ken Silverman's Build Engine. The generated .map file triggers a buffer overflow and overwrites the stack as shown below:
Open Watcom under DosBox 0.74-2: the analyst controls the stack
Under FreeDos 1.2: the analyst controls EIP
The vulnerable code is in ENGINE.C:
1935 kread(fil,&numsectors,2);
1936 kread(fil,§or[0],sizeof(sectortype)*numsectors);
Variable sector has a declared size of MAXSECTORS * sizeof(struct sectortype) = 1024 * 40 = 40960 bytes. The analyst controls numsectors (because it is read from the map file) and can thus create a map file to initialize numsectors with a value greater than 40960 to trigger the overflow.
Ken Silverman pointed out that code relying on the kread function, such as the following code snippets, might also be vulnerable:
In ENGINE.C:
1938 kread(fil,&numwalls,2);
1939 kread(fil,&wall[0],sizeof(walltype)*numwalls);
1940
1941 kread(fil,&numsprites,2);
1942 kread(fil,&sprite[0],sizeof(spritetype)*numsprites);
2033 kread(fil,palette,768);
2034 kread(fil,&numpalookups,2);
[...]
2046 kread(fil,palookup[globalpal],numpalookups<<8);
2047 kread(fil,transluc,65536);
2453 kread(fil,&artversion,4);
2454 if (artversion != 1) return(-1);
2455 kread(fil,&numtiles,4);
2456 kread(fil,&localtilestart,4);
2457 kread(fil,&localtileend,4);
2458 kread(fil,&tilesizx[localtilestart],(localtileend-localtilestart+1)<<1);
2459 kread(fil,&tilesizy[localtilestart],(localtileend-localtilestart+1)<<1);
2460 kread(fil,&picanm[localtilestart],(localtileend-localtilestart+1)<<2);
2520 kread(fil,&dasiz,4);
2521 //Must store filenames to use cacheing system :(
2522 voxlock[voxindex][i] = 200;
2523 allocache(&voxoff[voxindex][i],dasiz,&voxlock[voxindex][i]);
2524 ptr = (char *)voxoff[voxindex][i];
2525 kread(fil,ptr,dasiz);
In KDMENG.C:
1155 kread(fil,&dawaversionum,4);
1156 if (dawaversionum != 0) { kclose(fil); return; }
1157
1158 kread(fil,&numwaves,4);
1159 for(i=0;i<numwaves;i++)
1160 {
1161 kread(fil,&instname[i][0],16);
1162 kread(fil,&wavleng[i],4);
1163 kread(fil,&repstart[i],4);
1164 kread(fil,&repleng[i],4);
1165 kread(fil,&finetune[i],4);
1194 kread(fil,snd,totsndbytes);
1214 kread(fil,&kdmversionum,4);
1215 if (kdmversionum != 0) return(-2);
1216 kread(fil,&numnotes,4);
1217 kread(fil,&numtracks,4);
1218 kread(fil,trinst,numtracks);
1219 kread(fil,trquant,numtracks);
1220 kread(fil,trvol1,numtracks);
1221 kread(fil,trvol2,numtracks);
1222 kread(fil,nttime,numnotes<<2);
1223 kread(fil,nttrack,numnotes);
1224 kread(fil,ntfreq,numnotes);
1225 kread(fil,ntvol1,numnotes);
1226 kread(fil,ntvol2,numnotes);
1227 kread(fil,ntfrqeff,numnotes);
1228 kread(fil,ntvoleff,numnotes);
1229 kread(fil,ntpaneff,numnotes);
The PoC for this vulnerability has been tested using the following environments:
The Build engine has been used in many games. Below is a list of games based on the Build engine which have been tested against the PoC (which overflows the sector variable):
| Game | Release Date | Version | Status |
|---|---|---|---|
| Duke Nukem 3D | 1996 | 1.5 | vulnerable |
| Shadow Warrior | 1997 | 1.2 | vulnerable |
| Redneck Rampage | 1997 | 1.01 | vulnerable |
| Blood | 1997 | 1.0 | not vulnerable |