>From: Kevin Fu <[EMAIL PROTECTED]> >Reply-To: Kevin Fu <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: [linux-delhi] new vulnerability in Netscape effectively disables >SSL server auth >Date: Fri, 26 May 2000 09:51:24 EDT > >[For all you dudes who use Netscape to make lakhs of rupees worth of >online purchases... watch out! -- Raju] > >-----BEGIN PGP SIGNED MESSAGE----- > >Introduction >============ > >This vulnerability defeats SSL server authentication in Netscape 4.73 >and earlier versions. This is a new vulnerability unrelated to CERT >advisory 2000-5. However, it has a similar devastating effect: >destroying SSL server authentication. Under certain conditions, users >can no longer trust the authenticity of SSL server certificates in >Netscape. > >This new vulnerability makes Netscape's SSL implementation as insecure >as DNS. If you are victimized by this attack, then you may >unknowingly divulge private information such as credit card numbers, >personal data, passwords to online financial services, or other >sensitive information to an adversary masquerading as what you think >is a trusted SSL server. > >Reported to Netscape: May 15, 2000 >Reported to CERT: May 17, 2000 >Publicly announced: May 26, 2000 > > >Problem >======= > >Within one Netscape session, if a user clicks on "continue" in >response to a "hostname does not match name in certificate," then that >certificate is incorrectly validated for future use in the Netscape >session, REGARDLESS of the hostname or IP address of other servers >that use the certificate. > > >Exploit >======= > >My web server has a certificate signed by a trusted certificate >authority. For the purposes of this exploit, the example web servers >below share the same certificate and private key. > >Official name: snafu.mit.edu >Host address: 18.152.0.102 > >Official name: snafu.fooworld.org >Host address: 18.152.0.102 > >Official name: www.nscl.org >Host address: 18.152.0.131 > > >1. Play the part of the innocent user. Visit https://snafu.mit.edu/ >with any version on Netscape (minus the Personal Security Manager). >When the dialog warning appears, you click continue because you do not >intend to give private information to this web server. You just want >to access the page with confidentiality enabled, whether or not the >server is authentic. Note that you have asked to accept this >certificate for this hostname, snafu.mit.edu, even though the >certificate belongs to snafu.fooworld.org. > >2. Now play the part of the adversary. Simulate DNS poisoning. Add >an entry to /etc/hosts (UNIX), c:\windows\hosts.sam (Windows98), or >c:\winnt\system32\drivers\etc\hosts (Windows NT) that reads: > > www.the-site-you-want-to-spoof.com 18.152.0.131 > >This will redirect your www.the-site-you-want-to-spoof.com requests to >another server, www.nscl.org. The www.nscl.org server happens to use >the same certificate as snafu.mit.edu. > >2. Schach. Time to switch back to playing the innocent user. Visit >https://www.the-site-you-want-to-spoof.com/. If your browser allows >you to visit this site without a warning, you have been duped into >believing you are talking to a trusted SSL web server. > > >Analysis >======== > >If the ILOVEYOU virus has taught us anything, it's taught us that the >general user population can be easily fooled by seemingly innocent >requests. This vulnerability is a prime example. By following a link >to an SSL server that has a certificate with an incorrect hostname, >all future SSL connections in the Netscape session are made no more >secure than DNS. > >It seems that the "Certificate Name Check" warning will mark a >certificate as valid for any hostname or IP address in the future. In >this way, if an adversary tricks a user into accepting an invalid >certificate at a seemingly benign site, the user can then be tricked >if he/she ever visits a malicious site using the same certificate. A >benign "continue" click on https://snafu.mit.edu/ might end up taking >away server authentication from visiting >https://www.a-site-that-you-give-private-info.com/ that has poisoned >DNS. Note, I have only tested this with server certificates signed by >a certificate authority trusted by Netscape. This attack may be less >powerful if the malicious server certificate is merely self-signed. > >Furthermore, the security community has many examples showing that DNS >is not secure at all. For instance, a teenager recently defaced the >RSA.COM site by an attack against a DNS server. It should be trivial >to attack targeted individuals and not difficult to attack general >users at large. > >Here are some imagined but unimplemented ways that might fool a user >into accepting an invalid certificate: > >* Javascript/Java which references an HTTPS URL. >* Users just clicks. >* Hide the warning window with a pop-up window. >* Email with embedded HTTPS. >* Embed HTTPS images in a web page. >* VBS ILOVEYOU variant virus attachment that appends to hosts.sam and > adds certificate to browser's certificate database. > > >Here are some ways one might affect DNS: > >* Add a fake DNS entry for the target server in a compromised DNS server. >* Respond to DNS requests since UDP responses are easily forged. >* Modify /etc/hosts via a known root vulnerability on a UNIX machine. > Or on Windows, append to c:\windows\hosts.sam or on NT > c:\winnt\system32\drivers\etc\hosts > > >Tested Systems >============== > >Verified as vulnerable: >Linux Netscape 4.73 >Windows 98 Netscape 4.73 >Macintosh Netscape 4.73 > >Verified as not vulnerable: >Linux Netscape 4.73 + PSM >Windows 98 Netscape 4.73 + PSM >Windows 98 Microsoft Internet Explorer 5.00.2614.3500 > > >Solutions >========= > >There is a limited software solution if you run Linux, Solaris, or >Windows95/98/NT. Otherwise, you will have to manually inspect server >certificates in Netscape. The CERT CA-2000-8 advisory better explains >the non-software solution. > >If you run one of the above operating systems, then you must install >BOTH Netscape Communicator (v4.73) and the iPlanet Personal Security >Manager (PSM) for the full fix. PSM appears to manage certificates >more securely. Note, several people have reported problems installing >PSM. I was able to install PSM successfully in Linux and Windows98, >but sometimes the installation script would fail from a yet >undetermined cause. > >Netscape 4.73 download: >http://home.netscape.com/download/ > >iPlanet Personal Security Manger download: >http://www.iplanet.com/downloads/download/detail_128_316.html > >Again, installing the newest Netscape 4.73 alone does NOT fix this >problem. You must also install PSM. iPlanet's PSM does not yet exist >for the Macintosh. > > >Acknowledgements >================ > >Thank you to Shawn Hernan from CERT, Mitja Kolsek (from Advisory >CA-2000-5), Kevin Murray from Netscape, and Jon Guyer (who >independently found the same bug) for their cooperation and >assistance. > > >References >========== > >Inconsistent Warning Messages in Netscape Navigator >CERT Advisory CA-2000-08, May 26, 2000 >http://www.cert.org/advisories/CA-2000-08.html > >Netscape Navigator Improperly Validates SSL Sessions >CERT Advisory CA-2000-05, May 12, 2000 >http://www.cert.org/advisories/CA-2000-05.html > >RSA Security Site Defaced, Feb 14, 2000 >http://www.zdnet.com/zdnn/stories/news/0,4586,2437384,00.html > > >Author Contact Info >=================== > >Kevin Fu <[EMAIL PROTECTED]> >MIT Laboratory for Computer Science >545 Tech Square >Cambridge, MA 02139 > >If possible, please send correspondence encrypted with PGP. My key >available from the key servers or >https://snafu.fooworld.org/~fubob/pgp.html > >PGP Key ID: 0xE0FD2589 >PGP fingerprint: E183 68C5 1D46 1717 9CD5 E9AB D33B 1EB5 > > >Disclaimer >========== > >The information in this report is purely informational and meant only >for the purpose of education and protection. Kevin Fu shall in no >event be liable for any damage whatsoever, direct or implied, arising >from use or spread of this information. The use of information in >this report is entirely at the user's risk. > > >Copyright 2000 Kevin Fu >======================= > >You may distribute copies of this report provided that the >PGP-signature remains intact and the report remains unchanged within >the PGP-signed message. Check >http://snafu.fooworld.org/~fubob/netscape-ssl.html for updates to this >advisory. > >-----BEGIN PGP SIGNATURE----- >Version: PGP for Personal Privacy 5.0 >Charset: noconv > >iQEVAwUBOS5+uUWdEt/g/SWJAQFi/Af8Dx+dATp0tr3dWp1iVw0Evf2GvG9VDWMh >318vMTAqiDcECfxDitiH7oPGX+DrT584WbDcMOb3kfec8NbkfDUrvOs2ft7xgCh3 >lcQkaleoWforZIAPZEbeurqaOC2cySUWewgsf6pEyhv6PuzzIlkfKU+YCKKfhdmg >QA5C+qqWUzGWVrJuB+95sp2/0sKkH8toiWxJgwsPMybL58mpz3dS6UwPQUiTYVPB >qrW+7+vGRKwm4FVKlNcaNSegu34ciIL8f8uemcSOzIdJbNhj8KZU6HJWjakafQEi >2uHtTjqAQQAHDLrH1KMBtOdKOpgIAUywhvmhDS4/CfxDDqlDZenkoA== >=uB/F >-----END PGP SIGNATURE----- > > >-------- >Kevin E. Fu ([EMAIL PROTECTED]) >PGP key: https://snafu.fooworld.org/~fubob/pgp.html > >The mailing list archives are available at >http://lists.linux-india.org/cgi-bin/wilma/linux-delhi/ ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ______________________________________________________________________ Apache Interface to OpenSSL (mod_ssl) www.modssl.org User Support Mailing List [EMAIL PROTECTED] Automated List Manager [EMAIL PROTECTED]
