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The following was sent to BUGTRAQ today... would be a good idea to |
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convert to ssh if you havn't already ;) |
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|
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Could whoever is familiar with the netkit stuff please take a look at the |
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patch they mentioned? Thanks. |
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|
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Begin forwarded message: |
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|
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Date: Fri, 10 Aug 2001 00:14:03 +1200 (NZST) |
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From: <zen-parse@×××.net> |
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To: <bugtraq@×××××××××××××.com> |
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Subject: ADV/EXP: netkit <=0.17 in.telnetd remote buffer overflow |
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|
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|
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************************************************************************ |
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Product: netkit telnet protocol daemon, in.telnetd |
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|
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Version: netkit-telnet-0.17 (and previous) /usr/sbin/in.telnetd |
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|
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Severity: High |
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|
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Remote: Yes |
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|
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Allows: Remote ROOT level access. |
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|
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Workaround: Disable telnet access. |
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|
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Fix: Check with your vendor for an updated package. |
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|
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************************************************************************ |
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<from http://www.securityfocus.com/archive/1/197804, posted by |
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<scut@××××××××××××.de>. |
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|
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To: BugTraq |
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Subject: multiple vendor telnet daemon vulnerability |
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Date: Wed Jul 18 2001 22:15:10 |
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... |
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System | vulnerable | exploitable * |
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----------------------------------------+--------------+------------ |
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... | | |
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Linux netkit-telnetd >= 0.14 | no | |
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... | | |
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The bug has been discovered by scut. (It is easy to spot, so I do not |
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want to rule out discoveries by other persons) |
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... |
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The tests and further analysis were done by smiler, lorian, zip and |
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scut. |
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... |
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|
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<end of message> |
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|
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TESO were wrong about netkit >=0.14 not being vulnerable. |
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|
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************************************************************************ |
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Requires: Currently running telnet daemon (often on by default) |
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|
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/usr/in.telnetd <= netkit-telnet-0.17 |
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(telnet-0.17-7 is the default in.telnetd for Redhat 7.0) |
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|
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GLIBC > 2.0.6 |
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|
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************************************************************************ |
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Description of problem: |
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|
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The version of /usr/sbin/in.telnetd that comes as default on Redhat 7.0, |
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and many other distributions contains an exploitable overflow in the |
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handling of its output, allowing execution of arbitrary commands. |
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|
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The problem is in the handling of the AYT commands, as described in the |
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advisory already linked. |
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|
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************************************************************************ |
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Exploit details: (the attached file zp-exp-telnetd.c) |
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|
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If the user has local access to the system, it is possilble to get the |
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program to set arbitrary environment variables in the environment of |
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/bin/login. |
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e.g. LD_PRELOAD=/tmp/make-rootshell.so |
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|
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By filling the heap, in a similar way to the teso exploit, it its possible |
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to set 2 or more environment variables. |
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|
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If the user doesn't have local access, it is possible to overwrite the |
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chunk header information for a pointer used by setenv(3), and store a new |
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chunk in a user controllable location, so when the envrionement gets |
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reallocated it will change the value of arbitrary memory locations. |
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|
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e.g. You could cause the pointer to set the length of the previous chunk |
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to the distance back from the chunk to a point in netibuf, which itself |
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contains a chunk to set the address of a function in the GOT to point to |
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shellcode, which could also be stored in the network input buffer. |
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|
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Sometimes bad things happen that you have to kludge to fix. e.g. |
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push_clean() in the proof of concept exploit. Sometimes I got some |
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characters from the previous input being sent again, and when that was a |
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command to set an environment variable or something else that changed the |
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environment, it kinda messed with malloc calculations a little. |
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|
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As it is, this exploit will probably not work on your machine, but |
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carefully modifying appropriate values should fix that. |
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|
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|
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-- zen-parse |
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____ http://mp3.com/cosv _______ |
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/ ___\ __ _______ / _____/ __ |
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/ /_____/ \ / ____ \ / / ______/ \__________ |
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\______ /\ \__\ \ \ \ / / /_gone_\__/_platinum_\ |
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\ \/ ______/ \ \/ / \______/ \__________/ |
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\__/ \__/ \__/ |
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-- ObPlug: Buy our CD! |
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|
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-- Available: For work in the security industry. (email for details) |
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|
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------------------------------------------------------------------------- |
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The preceding information, unless directly posted by zen-parse@×××.net to |
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an open forum is confidential information and not to be distributed |
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(without explicit permission being given by zen-parse@×××.net). Legal |
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action may be taken to enforce this. If you are mum or dad, this probably |
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doesn't apply to you. |
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|
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--------------------------------------------------------------------- |
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Bruce A. Locke |
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blocke@××××××.org |
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