openSUSE Security June 2002

security@lists.opensuse.org

180 participants
198 discussions

how to keep nimda and code red from filling apache logs

by Mathias Homann

Hi all, here's a bit of a step-by-step description on how to keep nimda and codered from filling your apache logs. Parts used: - SuSE 7.2 Professional - SuSEfirewall2 - iptables 1.2.3 - linux kernel 2.4.13-pre5 steps: 1. install kernel sources for a kernel >> 2.4.9, running 2.4.13- pre5 here, works fine so far 2. get the sources for iptables 1.2.3 from http://netfilter.samba.org 3. unpack sources somewhere 4. export KERNEL_DIR=$(where you put the kernel tree) 5. cd into unpacked iptables sources, there's a subdirectory named patch-o-matic there 6. apply wanted patches by running ./runme $(name.of.patch)patch for this here You'll want the string patch You can also apply other patches, like the irc-conntrack patch 7. now there's a little bug in this patch... here's a diff: --- linux/net/ipv4/netfilter/ipt_string.c~ Sun Oct 21 00:16:29 2001 +++ linux/net/ipv4/netfilter/ipt_string.c Sun Oct 21 16:54:45 2001 @@ -62,7 +62,7 @@ sk = skip[haystack[right_end - i]]; sh = shift[i]; - right_end = max(int, right_end - i + sk, right_end + sh); + right_end = max(right_end - i + sk, right_end + sh); } return NULL; 8. now, make config/menuconfig/xconfig... as usual. You can import your running kernel's config first. 9. enable the experimental stuff 10. go to networking options->netfilter, there's an option there to enable string matching; set that to M 11. compile and install kernel as usual; remember to uncomment the export INSTALL_PATH=/boot in the main makefile. 12. now build a rpm file for the new iptables stuff by installing the source rpm which comes with suse, then edit the spec file, put the iptables source in /usr/src/packages/SOURCE and rebuild. 13. now there are some small changes to the firewall config files. a) uncomment the last line in /etc/rc.config.d/firewall2.rc.config: FW_CUSTOMRULES="/etc/rc.config.d/firewall2-custom.rc.config" b) edit that file, I got the following stuff in mine: for forbidden_string in root.exe cmd.exe .ida; do iptables -I input_ext -p tcp --dport http -m string \ --string $forbidden_string -m state \ --state ESTABLISHED -j REJECT --reject-with tcp-reset done put that in the last supfunction defined in the custom rc file. c) change the FW_LOG setting in firewall2.rc.config from reading -log-level warning to -log-level kernel.warning 14. last: some small changes to /sbin/SuSEfirewall2 search in the script for the parts where the modules are loaded and unloaded; be sure to add ipt_string (and the other new modules you created by patching the kernel and enabling them in make config) to the modules loading/unloading code there. 15. reboot 16. if you try now to access (from outside, of course) one of the nimda or codered URLS, all you get is a 'connection reset by peer', and the request doesn't show in apache log files. btw, no guarantees, and the usual YMMV :) bye [L]

18 years, 9 months

suse samba server

by jonathan

Hello I have basically a suse samba server setup. Eth0 is for the internet connection (cable). Eth1 is my internal network. I use eth1 for my samba server. When i have the shares/ drive letters mapped, whatever, Ill goto access them and that computer will just lockup or timeout for about 1 minute, then it will resume operation normally. I have approx. 5 comptuers on the suse server, and they all do this from windows xp to windows 98se. I am using set up addresses of 192.168.0.x, where is greater than 2. My question is have or is there something Ive setup wrong to cause this pause to occur. ? Its becomming very annoying..and frustrating. Im using kernel 2.4.18-64GB-SMP with a dual processor setup. If anyone has any ideas please let me know. Every package installed is orginal versions from the suse install cdroms. (no updates done). Anything come to mind. btw, ive replaced the switch, with a new netgear one, and all the networks at startech ST100 Realtek 8139 chipsets on 100Tx. Anyone... !

19 years, 5 months

Urgggggg!!! SuSEFirewall2 is getting on my nerves!!!!!

by Chris Bek

Hi there SuSErs... Well I must be doing something really wrong because everything that I do with SuSEFirewall2 is just not working! I have a small network with 5 PCs (all Win9X) and a Linux box (Currently SuSE 7.3) acting as a server. The server is a DHCP server and a Samba server for the entire network. So far everything is working perfect!!! Users log on the network, logon script executes etc.... Then a new task came up: let's input the internet into the network. Configured a 56Kbps modem on the server with YAST. Manged to get my account setup and running. Made a test connection and netscape works great on the server as well as e-mail (pop3). I tried configuring SuSEfirewall to manage all incoming requests from the PCs of the network. The firewall warned me about masquerading etc. so I downloaded the latest version of SuSEfirewall2 from the internet and installed it. Since I only need direct masquerading to be done (no proxies are currently working on the net) I made all the necessary changes as outlined in the examples supplied with the software. Since I needed to have Samba to keep working on the network, I opened (among others) 139 port for samba to work. Double checked all the changes that I have made and run rcSuSEfirewall2 to see what happens. Strange enough when wvdial executes it tells me that DNS is not functioning properly since www.suse.com cannot be found (or something like that please forgive me I am away from the Linux station now). Further on, when I open mIRC or other like programs (winmx etc) from a station, I look at the activity of IPtraf (I check this to see what happens) and I see no connections being created whatsoever.... mIRC prompts me that there was an error trying to find the host.... I have made no changes to the Win9X PCs. Is there something that I am forgeting to do?? I undestand that it is impossible for all of you to react to this since I have no output of the SuSEfirewall.conf file being published to this message.... I understand. Can someone please send me their configuration file so I can see what you have done, on a system that currently is working fine?? In addition, is there something that I have to do regarding route or routing?? What about the Win9X PCs?? Is there something that I have to do there?? I thank you so very much for all your help is advance!!!! I am killing myself trying to figure this one out for about 2 weeks now and managed nothing more than thin air!!!!! Chris

19 years, 5 months

SSH Authentication

by Joao Reis

Hi! I implemented a ssh conection from the outside to my intranet. This ssh requires a username and a password. In terms of security what is more secure: require authentication (username and password) or having the public key of each user that connects to our intranet in the authorized public key lists (in this case there is no need for username and password)? In the second case there is no need of authentication and only the users wich have the public keys in the list are allowed to enter in my intranet. This second solution is a good solution or that brings other security problems ? Thanks. -- Farewell. "Keep your friends close, but your enemies closer." "Do or do not. There is no try" - Yoda João Reis -------------------------------------------------------

19 years, 7 months

File access permissions on home users directory

by Corneliu MUSAT

Hi, When I create a new user (useradd os yast2) the users home directory have 755 access permissions. Is this normal ? What am I doing wrong ?! -- Cornel. tel.:4092743604

19 years, 12 months

MD5 password confirmation fails after update to OpenSSH 3.3 on SuSE 7.3

by Thomas Föcking

Hello, this morning I updated all linux servers running SuSE 7.3 to OpenSSH 3.3. Now I am not able to login via ssh anymore - password confirmation fails. First I tought, that sshd is not allowed to read /etc/shadow, but this was not the case. "harden_suse" made my /etc/shadow passwords be encrypted with MD5. After adding a new user with yast the new user's password was only DES encrypted. With this user I am able to login, with users who has got MD5 encrypted passwords I'm not able to login via ssh. Am I right, that the new sshd has got problems with MD5 password? What can I do now? Regards, Thomas

20 years

firewall problem

by Thomas Nyman

Hi, I have a problem with my SuSEfirewall2..despite reading the examples and faq I cant get it to allow incoming and otugoing traffic on port 25 the firewall is run on a machine configured as follows eth0 = external network (internet) eth1 = internal network (192.168.1.1) the machine runs postfix and postfix can't open port 25. I've enclosed my firewall script..I'm hoping someone can see what I've done wrong. Thomas -------------------------------------------------------

20 years

OpenSSH 3.3p1 on Suse 7.1 - lockup?

by Hemsley, Trevor

I've read most of the recent discussion about Openssh 3.3p1 but haven't seen this particular issue so... I installed the 3.3p1 patch on several Suse 7.1 boxes, 7 in the UK that I can reach locally yesterday and they all seem fine and 5 more in another country that I can't get to without a plane ticket :-( Sequence of installation was to use YOU to apply the patch while logged on via SSH on all machines then to shutdown -r now them, wait a bit then log back on. So far so good on all boxes. However, within 30 minutes of the reboot on the 5 machines that I cannot reach locally, 2 of them have become inaccessible. They don't ping and nmap with the -P0 option doesn't get any response from them. That looks pretty dead to me. Neither of these two machines has done this before and up until now, they've up and running for 113 days without any issue. I can't categorically state that it is the Openssh patch that's done this since I can't find anyone around to go and look at them to find out if they're sitting with an Ooops message or what's wrong with them. But it's suspicious enough that I've backed out 3.3p1 on the machines I can still get to and gone back to 2.9.9p2-98 for now. And, yes, if I'd read the mailing list before I put the patches on then I probably wouldn't have bothered :-) With issues like this, maybe Suse should pull these particular patches off the web page/ftp site? Especially since it appears that the 2.9.9p2 rpm's aren't vulnerable to the exploit that the advisory is meant to fix. Trevor Hemsley, Security Specialist, Atos Origin Ltd, Whyteleafe, +44-(0)1883-628139 [This electronic transmission and any files attached to it are strictly confidential and intended solely for the addressee. If you are not the intended addressee, you must not disclose, copy or take any action in reliance of this transmission. If you have received this transmission in error, please notify us by return and delete the same. The views expressed in this electronic transmission do not necessarily reflect those of Atos Origin or any of its subsidiary companies. Although the sender endeavours to maintain a computer virus free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. Thank You.]

20 years

Re: [suse-security] Buffer Overflows in DNS Resolver libs...

by ts

> for those who doesn't know already: > > http://online.securityfocus.com/archive/1/279637/2002-06-2 > 6/2002-07-02/0 > > so, hava nice weekend ;) > > Sven Yeah, I looked at this, the resolver libraries. 8.3.3 and 9.0(?) were reported safe. Any ideas on a quick fix?

20 years

Buffer Overflows in DNS Resolver libs...

by Sven 'Darkman' Michels

for those who doesn't know already: http://online.securityfocus.com/archive/1/279637/2002-06-26/2002-07-02/0 so, hava nice weekend ;) Sven

20 years

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openSUSE Security June 2002