[UNIX] ARC Insecure Temporary File Creation

From: SecuriTeam (support_at_securiteam.com)
Date: 09/19/05

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Date: 19 Sep 2005 10:26:08 +0200

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      ARC Insecure Temporary File Creation
    ------------------------------------------------------------------------

    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@zataz.net> 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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