An IIS 8.5 websites cookies, sent to the client using SSL/TLS, must not be compressed.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-76857	IISW-SI-000245	SV-91553r1_rule		Medium

Description
A cookie is used when a web server needs to share data with the client's browser. The data is often used to remember the client when the client returns to the hosted application at a later date. A session cookie is a special type of cookie used to remember the client during the session. The cookie will contain the session identifier (ID) and may contain authentication data to the hosted application. To protect this data from easily being compromised, the cookie can be encrypted. When a cookie is sent encrypted via SSL/TLS, an attacker must spend a great deal of time and resources to decrypt the cookie. If, along with encryption, the cookie is compressed, the attacker can now use a combination of plaintext injection and inadvertent information leakage through data compression to reduce the time needed to decrypt the cookie. This attack is called Compression Ratio Info-leak Made Easy (CRIME). Cookies shared between the web server and the client when encrypted should not also be compressed.

Description

A cookie is used when a web server needs to share data with the client's browser. The data is often used to remember the client when the client returns to the hosted application at a later date. A session cookie is a special type of cookie used to remember the client during the session. The cookie will contain the session identifier (ID) and may contain authentication data to the hosted application. To protect this data from easily being compromised, the cookie can be encrypted. When a cookie is sent encrypted via SSL/TLS, an attacker must spend a great deal of time and resources to decrypt the cookie. If, along with encryption, the cookie is compressed, the attacker can now use a combination of plaintext injection and inadvertent information leakage through data compression to reduce the time needed to decrypt the cookie. This attack is called Compression Ratio Info-leak Made Easy (CRIME). Cookies shared between the web server and the client when encrypted should not also be compressed.

STIG	Date
IIS 8.5 Site Security Technical Implementation Guide	2018-01-03

Details

Check Text ( C-76513r1_chk )
Follow the procedures below for each site hosted on the IIS 8.5 web server: Access the IIS 8.5 Manager. Select the webserver and each website being reviewed. Under "Management" section, double-click the "Configuration Editor" icon. From the "Section:" drop-down list, select "system.web/httpCookies". Verify the "require SSL" is set to "True". From the "Section:" drop-down list, select "system.web/sessionState". Verify the "compressionEnabled" is set to "False". If both the "system.web/httpCookies:require SSL" is set to "True" and the "system.web/sessionState:compressionEnabled" is set to "False", this is not a finding.

Check Text ( C-76513r1_chk )

Follow the procedures below for each site hosted on the IIS 8.5 web server:

Access the IIS 8.5 Manager.

Select the webserver and each website being reviewed.

Under "Management" section, double-click the "Configuration Editor" icon.

From the "Section:" drop-down list, select "system.web/httpCookies".

Verify the "require SSL" is set to "True".

From the "Section:" drop-down list, select "system.web/sessionState".

Verify the "compressionEnabled" is set to "False".

If both the "system.web/httpCookies:require SSL" is set to "True" and the "system.web/sessionState:compressionEnabled" is set to "False", this is not a finding.

Fix Text (F-83553r1_fix)
Follow the procedures below for each site hosted on the IIS 8.5 web server: Access the IIS 8.5 Manager. Select the webserver and each website being reviewed. Under "Management" section, double-click the "Configuration Editor" icon. From the "Section:" drop-down list, select "system.web/httpCookies". Set the "require SSL" to "True". From the "Section:" drop-down list, select "system.web/sessionState". Set the "compressionEnabled" to "False". Select "Apply" from the "Actions" pane.

Fix Text (F-83553r1_fix)

Follow the procedures below for each site hosted on the IIS 8.5 web server:

Access the IIS 8.5 Manager.

Select the webserver and each website being reviewed.

Under "Management" section, double-click the "Configuration Editor" icon.

From the "Section:" drop-down list, select "system.web/httpCookies".

Set the "require SSL" to "True".

From the "Section:" drop-down list, select "system.web/sessionState".

Set the "compressionEnabled" to "False".

Select "Apply" from the "Actions" pane.