I read a great entry from the ModSecurity blog. This is in relation to repairing the HTTPOnly and Secure Cookie flags. According to the Microsoft Developer Network, HttpOnly is an additional flag included in a Set-Cookie HTTP response header. Using the HttpOnly flag when generating a cookie helps mitigate the risk of client side script accessing the protected cookie (if the browser supports it).
According to the OWASP website, if the HttpOnly flag (optional) is included in the HTTP response header, the cookie cannot be accessed through client side script (again if the browser supports this flag). As a result, even if a cross-site scripting (XSS) flaw exists, and a user accidentally accesses a link that exploits this flaw, the browser (primarily Internet Explorer) will not reveal the cookie to a third party.
If a browser does not support HttpOnly and a website attempts to set an HttpOnly cookie, the HttpOnly flag will be ignored by the browser, thus creating a traditional, script accessible cookie. As a result, the cookie (typically your session cookie) becomes vulnerable to theft of modification by malicious script.
If you are only interested in addressing the missing "Secure" cookie flag, then you can simply take the example from the previous post and edit it slightly to swap out "httponly" with "secure". If, however, you want to try and address both of these issues together, then you will need to change the rule set approach a bit so that it works correctly. This is because there are now three different scenarios you have to account for -
• Missing HTTPOnly flag
• Missing Secure flag (if the SessionID is being sent over an SSL connection)
• Missing both HTTPOnly and Secure flags
With this in mind, here is an updated rule set that will handle both missing HTTPOnly and Secure cooking flags.
#
# First we want to capture Set-Cookie SessionID data for later inspection
SecRule RESPONSE_HEADERS:/Set-Cookie2?/ "(?i:(j?sessionid|(php)?sessid|(asp|jserv|jw)?session[-_]?(id)?|cf(id|token)|sid))" "phase:3,t:none,pass,nolog,setvar:tx.sessionid=%{matched_var}"
#
# We now check the saved SessionID data for the HTTPOnly flag and set an Apache
# ENV variable if it is missing.
SecRule TX:SESSIONID "!(?i:\;? ?httponly;?)" "phase:3,t:none,setenv:httponly_cookie=%{matched_var},pass,log,auditlog,msg:'AppDefect: Missing HttpOnly Cookie Flag.'"
#
# Next we check the saved SessionID data for the Secure flag (if this is an SSL session)
# and set an Apache ENV variable if it is missing.
SecRule SERVER_PORT "@streq 443" "chain,phase:3,t:none,pass,log,auditlog,msg:'AppDefect: Missing Secure Cookie Flag.'"
SecRule TX:SESSIONID "!(?i:\;? ?secure;?)" "t:none,setenv:secure_cookie=%{matched_var}"
#
# The final check is to see if BOTH of the HTTPOnly and Secure cookie flags are missing
# and set an Apache ENV variable if they are missing.
SecRule TX:SESSIONID "!(?i:\;? ?httponly;?)" "chain,phase:3,t:none,pass,log,auditlog,msg:'AppDefect: Missing HttpOnly and Secure Cookie Flag.'"
SecRule SERVER_PORT "@streq 443" "chain,t:none"
SecRule TX:SESSIONID "!(?i:\;? ?secure;?)" "t:none,setenv:secure_httponly_cookie=%{matched_var}"
#
# This last section executes the Apache Header command to
# add the appropriate Cookie flags
Header set Set-Cookie "%{httponly_cookie}e; HTTPOnly" env=httponly_cookie
Header set Set-Cookie "%{secure_cookie}e; Secure" env=secure_cookie
Header set Set-Cookie "%{secure_httponly_cookie}e; Secure; HTTPOnly" env=secure_httponly_cookie
These rules will both alert and fix these cookie issues. You may want to switch the actions to "nolog" so that you are not flooded with alerts.