- 1 Draft - Work In Progress
- 1.1 Basic configuration
- 1.2 Request filtering
- 1.2.1 Configure maxAllowedContentLength
- 1.2.2 Configure maxURL request filter
- 1.2.3 Configure maxQueryString request filter
- 1.2.4 Reject non-ASCII characters in URLs
- 1.2.5 Reject double-encoded requests
- 1.2.6 Disable HTTP trace requests
- 1.2.7 Disallow unlisted file extensions
- 1.2.8 Enable Dynamic IP Address Restrictions
- 1.3 Transport Encryption
- 1.3.1 SSL/TLS settings are controlled at the SChannel level. They are set machine wide and IIS respects these values.
- 1.3.2 A list of recommendations for IIS
- 1.4 HSTS support
- 1.5 CORS support
- 1.6 Authors
Draft - Work In Progress
Common changes that should be part of all IIS installations.
Directory browsing gives the user the ability to just navigate to http://server/directory/ and get a list of all files in the directory. This was useful when web servers were primarily file servers, but is clearly a security problem now.
To disable directory browsing in IIS 10.0 (and several earlier versions, either:
1) Alter the web.config to set the directoryBrowse feature to false
<configuration> <system.webServer> <directoryBrowse enabled="false" /> </system.webServer> </configuration>
2) or Navigate to IIS in the Server Manager, and uncheck Directory Browsing under Common HTTP Features.
Avoid wildcard host headers
IIS 10.0 has added wildcard host headers. This means that if there is a website hosted for a domain, the server will handle requests for any subdomain, allowing the developer to make decisions based on the request as how to respond.
In general, this is a bad idea and shouldn't be used. There are very specific reasons to use them, but it is almost guaranteed that your situation isn't one of them.
Certainly, do not use wildcard domains, like http://* for example. But in general avoid using them at all. Instead use site bindings to solve the same problem.
Ensure applicationPoolIdentity is configured for all application pools
applicationPoolIdentity configured the Active Directory user that the applications in the pool impersonate.
To assure that this value is set, navigate to an Application Pool in IIS Manager, right click and select Application Pool defaults. Then select the appropriate user.
Use an unique applicationPool per site
Application bools are designed to create a collection of sites that can be restarted together, and have a common max memory limit, and some other features. With today's applications, it is best if there is a unique application pool for each site. Perhaps if there is a separate project for services and the front end of an application, then they could go together in one pool but for the majority of applications, one pool per app.=
There are two ways to configure application pools for IIS.
1)In IIS Manager, expand Sites in the Connections pane. Then click Advanced Settings, then the ellipsis button next to Application Pool. Select a unique pool there.
2) Using the command prompt, run appcmd to set up new command pools.
appcmd.exe set config -section:system.applicationHost/applicationPools /+"[name='NewCommandPool',autoStart='True',managedPipelineMode='Integrated']" /commit:apphost
Disable IIS detailed error page from displaying remotely
When debugging a production application that is misbehaving, we would like to see detailed errors when using the server at the console, but show remote users custom pages.
To handle this, use the IIS Console and select Exceptions. In the Actions column, select Edit Feature Settings and then select Detailed Errors For Local Requests and Custom Errors For Remote Requests.
The maxAllowedContentLength is a part of the requestLimits collection, and it is too long by default for most requests (around 26 MB). On an application bases it can be altered using the requestFiltering node in the Security collection. Here is an example in the web.config:
In C#, it is possible to change the content length for a particular request with the ServerManager:
Configure maxURL request filter
Configure maxQueryString request filter
Reject non-ASCII characters in URLs
Reject double-encoded requests
Disable HTTP trace requests
Disallow unlisted file extensions
Enable Dynamic IP Address Restrictions
SSL/TLS settings are controlled at the SChannel level. They are set machine wide and IIS respects these values.
A list of recommendations for IIS
Disable SSL v2/v3
Disable TLS 1.0
Disable TLS 1.1
Ensure TLS 1.2 is enabled
Disable weak cipher suites (NULL cipher suites, DES cipher suites, RC4 cipher suites, Triple DES, etc)
Ensure TLS cipher suites are correctly ordered
IIS recently (Windows Server 1709) added turnkey support for HSTS
If you choose not to handle CORS in your application, we ship an IIS an IIS module to help configure CORS
Sourabh Shirhatti (Microsoft)
Bill Sempf (email@example.com)