Title

Public web servers must use TLS if authentication is required. (Cat II impact)

Discussion

Transport Layer Security (TLS) is optional for a public web server. However, if authentication is being performed, then the use of the TLS protocol is required. Without the use of TLS, the authentication data would be transmitted unencrypted and would become vulnerable to disclosure. Using TLS along with DoD PKI certificates for encryption of the authentication data protects the information from being accessed by all parties on the network. To further protect the authentication data, the web server must use a FIPS 140-2 approved TLS version and all non-FIPS-approved SSL versions must be disabled. FIPS 140-2 approved TLS versions include TLS V1.0 or greater. NIST SP 800-52 specifies the preferred configurations for government systems.

Check Content

1. Open the IIS Manager > Right click on the website to be examined > Select properties > Select the Web Site tab > Note the entry for the SSL port (i.e. 443). 2. Select the Directory Security tab > Select the Edit button in the Secure communications section. 3. Ensure the Require secure channel (SSL) and Require 128-bit encryption check boxes are checked. If the Require secure channel (SSL) and Require 128-bit encryption check boxes are not checked, this is a finding. If the site requires SSL and 128-bit encryption, then the version of SSL also needs to be verified. The following registry keys need to exist and be set to not allow anything lower than TLS. This can be accomplished by ensuring the following value exists in each of the keys: Enabled REG_DWORD 0 HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\PCT 1.0\Client HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\PCT 1.0\Server HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 2.0\Client HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 2.0\Server HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 3.0\Client HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 3.0\Server If these keys are not set to a DWORD value of 0, this is a finding. If the keys do not contain the value Enabled, this would also be a finding. The keys for TLS 1.0 do not require the Enabled value to be present, but if it is, it needs to be set to REG_DWORD 1, to enable TLS. If the Enable value is present and is not set to 1, this is a finding. NOTE: In some cases the web servers are configured in an environment to support load balancing. This configuration most likely utilizes a content switch to control traffic to the various web servers. In this situation, the SSL certificated for the web sites may be installed on the content switch vs. the individual web sites. This solution is acceptable as long as the web servers are isolated from the general population LAN. Users should not have the ability to bypass the content switch to access the web sites.

Fix Text

1. Obtain and install a server certificate from a .mil Certificate Authority or approved DoD ECA. 2. Open the IIS Manager > Right click on the website to be examined > Select properties > select the Directory Security tab > Select the Edit button in the Secure communications section. 3. Select Require secure channel (SSL) and Require 128-bit encryption check boxes. 4. Set the version SSL\TLS by creating and setting the following registry to not allow anything lower than TLS. Ensure the following value exists in each of the keys: Enabled REG_DWORD 0 HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\PCT 1.0\Client HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\PCT 1.0\Server HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 2.0\Client HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 2.0\Server HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 3.0\Client HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\SSL 3.0\Server The keys for TLS 1.0 do not require the Enabled value to be present, but if it is, it needs to be set to REG_DWORD 1, to enable TLS.

Additional Identifiers

Rule ID: SV-28566r2_rule

Vulnerability ID: V-13694

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.