[UNIX] ARC Insecure Temporary File Creation

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  ARC Insecure Temporary File Creation
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SUMMARY

 <http://sourceforge.net/projects/arc/> ARC is "used to create and 
maintain file archives. An archive is a group of files collected together 
into one file in such a way that the individual files may be recovered 
intact".

A vulnerability in ARC is caused due to temporary file being created 
insecurely. The temporary file used for archive creation could be read by 
untrusted users.

DETAILS

Vulnerable Systems:
 * ARC versions 5.21j and prior.

Vulnerable code:
arc.c :
210     /* see where temp files go */
211 #if   !_MTS
212     arctemp = calloc(1, STRLEN);
213     if (!(arctemp2 = envfind("ARCTEMP")))
214         arctemp2 = envfind("TMPDIR");
215     if (arctemp2) {
216         strcpy(arctemp, arctemp2);
217         n = strlen(arctemp);
218         if (arctemp[n - 1] != CUTOFF)
219             arctemp[n] = CUTOFF;
220     }
221 #if   UNIX
222     else  strcpy(arctemp, "/tmp/");
223 #endif
224 #if   !MSDOS
225     {
226         static char tempname[] = "AXXXXXX";
227         strcat(arctemp, mktemp(tempname));
228     }
229 #else
230     strcat(arctemp, "$ARCTEMP");
231 #endif
232 #else
233     guinfo("SHFSEP ", gotinf);
234     sepchr[0] = gotinf[0];
235     guinfo("SCRFCHAR", gotinf);
236     tmpchr[0] = gotinf[0];
237     arctemp = "-$$$";
238     arctemp[0] = tmpchr[0];
239 #endif
240     arctemp2 = NULL;
241
242 #if   !UNIX
243     /* avoid any case problems with arguments */
244
245     for (n = 1; n < num; n++)    /* for each argument */
246         upper(arg[n]); /* convert it to uppercase */
247 #else
248     /* avoid case problems with command options */
249     upper(arg[1]);     /* convert to uppercase */
250 #endif
251
252     /* create archive names, supplying defaults */
253 #if   UNIX
254     if (!stat(arg[2],&sbuf)) {
255         if ((sbuf.st_mode & S_IFMT) == S_IFDIR)
256             makefnam(arg[2],".arc",arcname);
257         else
258             strcpy(arcname,arg[2]);
259     } else
260         makefnam(arg[2],".arc",arcname);
261 #else
262     makefnam(arg[2], ".ARC", arcname);
263 #endif

Take a look on a the right off temporary files in /tmp :
-rw-r--r-- 1 root root 1564 Sep 5 10:28 A3C6Zs4.arc
The file should not be world readable.

The same problem exists in marc.c


ADDITIONAL INFORMATION

The information has been provided by  <mailto:exploits@xxxxxxxxx> ZATAZ 
Audits.
The original article can be found at:  
<http://www.zataz.net/adviso/arc-09052005.txt> 
http://www.zataz.net/adviso/arc-09052005.txt



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