MIME Types in ISA Server 2004
Multipurpose Internet Mail Extensions (MIME) is a standard covered in RFC 822, RFC 1521, and RFC 1522. MIME types (also known as content types or media types) instruct a Web browser or mail application how to handle files received from a server. MIME provides a mechanism for sending a variety of file types as a part of an e-mail message, or attached to an e-mail message. To open and read such an attached file, an application installed on the receiving operating system must be associated with the file type (extension). For example, when a Web browser requests an item on a server, it also requests the MIME type of the object. Some MIME types, like graphics, can be displayed inside the browser. Others, such as word processing documents, require an external application to be displayed.
Content types in Microsoft Internet Security and Acceleration (ISA) Server 2004 specify MIME types and file name extensions. When you create an access rule, you can define it so that it applies to specific content types. This enables you to configure granular security policies by limiting access to specific types of content.
Content Types
Link Translation and Content Types
Appendix A: Default MIME Type Associations for IIS
Additional Resources
When you use content types in ISA Server access rules, content type parameters specified in a rule are only applied to Hypertext Transfer Protocol (HTTP) and tunneled File Transfer Protocol (FTP) traffic that passes through ISA Server. Content types do not apply to any other protocol, such as HTTPS. HTTP and FTP tunneled traffic is processed as follows:
- When a client requests HTTP content, ISA Server sends the request to the Web server. When the Web server returns the object, ISA Server checks the object's MIME type or its file name extension, depending on the header information returned by the Web server. ISA Server determines if a rule applies to a content type that includes the requested file name extension, and processes the rule accordingly.
- When a client requests FTP content, ISA Server checks the file name extension of the requested object. ISA Server determines if a rule applies to a content type that includes the requested file name extension, and processes the rule accordingly.
ISA Server provides predefined content types, including:
- Application
- Application data files
- Audio
- Compressed files
- Documents
- HTML documents
- Images
- Macro documents
- Text
- Video
- VRML
You can create your own content types. Common content types you may want to add include:
- Common Windows media types:
- .wma (Windows media audio)
- .wmv (Windows media video)
- .asf (either audio or video)
- Potentially dangerous files:
- .jse (encoded JScript)
- .vbe (encoded VBScript)
- .wsf (Windows Script file)
- .reg (Windows registry file)
- .pl (PERL script)
- .com (executable)
When you create content types, we recommend that you specify the content's MIME type and file name extension. For example, to include all directory files in a content type, select the following file name extensions and MIME types:
- .dir
- .dxr
- .dcr
- application/x-director
When you configure a content type and specify the MIME type, you can use an asterisk (*) as a wildcard character. For example, to include all application types, enter application/*. The asterisk wildcard character can be used only with MIME types (and not with file extensions). The asterisk can be specified only once, at the end of the MIME type after the slash mark (/).
Depending on the Web server, different MIME types are associated with different file name extensions. A list of the default associations for Internet Information Services (IIS) is provided in Appendix A.
To create a content type, use the following steps.
In the console tree of ISA Server Management, click Firewall Policy.
In the task pane, on the Toolbox tab, click Content Types.
On the toolbar beneath Content Types, click New to open the New Content Type Set dialog box.
In Name, type the name of the content type.
(Optional) In Description, type a description for the content type.
In Available types, do one of the following:
- To select an existing content type, select a file name extension or MIME type from the drop-down list, and then click Add.
- To add a new content type, type a new file name extension or a MIME type, and then click Add.
Note
You can use an asterisk () as a wildcard character. For example, to include all application types, enter application/.To remove a file name extension or MIME type from the content type, in Selected types, click the file name extension or MIME type, and then click Remove.
Some published websites may include references to internal computer names. Because only ISA Server is available to external clients, and not computers on the Internal network, these references will appear as broken links. ISA Server has a link translation Web filter that enables you to create a dictionary of definitions for internal computer names that map to publicly known names. When you enable link translation for a Web publishing rule, a link translation dictionary is automatically created. You can add more entries to this default dictionary if required.
The link translation filter checks the Content-type header of the request response to determine whether it needs to perform translation on the body of the message. By default, link translation only operates on the HTML documents content group, but you can specify other groups. If no Content-type header is present, the filter will look for a Content-location header to perform translation. If neither header is present, the filter will look at the file name extension of the requested URL.
Note
When the Outlook Web Access server or the ISA Server computer listens for requests on nonstandard ports, and the configured bridging mode is Secure connection to mail server, you must enable link translation for a content type that includes the following:
- application/x-javascript
- text/css
- text/x-component
- text/xml
- .eml
- .css
You must create a new content type, or modify an existing content type, to include these file and MIME types.
Depending on the Web server, different MIME types are associated with different file name extensions. The following table lists the Internet Information Services (IIS) default associations.
File name extension | MIME type |
---|---|
.hta |
application/hta |
.isp |
application/x-internet-signup |
.crd |
application/x-mscardfile |
.pmc |
application/x-perfmon |
.spc |
application/x-pkcs7-certificates |
.sv4crc |
application/x-sv4crc |
.bin |
application/octet-stream |
.clp |
application/x-msclip |
.mny |
application/x-msmoney |
.p7r |
application/x-pkcs7-certreqresp |
.evy |
application/envoy |
.p7s |
application/pkcs7-signature |
.eps |
application/postscript |
.setreg |
application/set-registration-initiation |
.xlm |
application/vnd.ms-excel |
.cpio |
application/x-cpio |
.dvi |
application/x-dvi |
.p7b |
application/x-pkcs7-certificates |
.doc |
application/msword |
.dot |
application/msword |
.p7c |
application/pkcs7-mime |
.ps |
application/postscript |
.wps |
application/vnd.ms-works |
.csh |
application/x-csh |
.iii |
application/x-iphone |
.pmw |
application/x-perfmon |
.man |
application/x-troff-man |
.hdf |
application/x-hdf |
.mvb |
application/x-msmediaview |
.texi |
application/x-texinfo |
.setpay |
application/set-payment-initiation |
.stl |
application/vndms-pkistl |
.mdb |
application/x-msaccess |
.oda |
application/oda |
.hlp |
application/winhlp |
.nc |
application/x-netcdf |
.sh |
application/x-sh |
.shar |
application/x-shar |
.tcl |
application/x-tcl |
.ms |
application/x-troff-ms |
.ods |
application/oleobject |
.axs |
application/olescript |
.xla |
application/vnd.ms-excel |
.mpp |
application/vnd.ms-project |
.dir |
application/x-director |
.sit |
application/x-stuffit |
.* |
application/octet-stream |
.crl |
application/pkix-crl |
.ai |
application/postscript |
.xls |
application/vnd.ms-excel |
.wks |
application/vnd.ms-works |
.ins |
application/x-internet-signup |
.pub |
application/x-mspublisher |
.wri |
application/x-mswrite |
.spl |
application/futuresplash |
.hqx |
application/mac-binhex40 |
.p10 |
application/pkcs10 |
.xlc |
application/vnd.ms-excel |
.xlt |
application/vnd.ms-excel |
.dxr |
application/x-director |
.js |
application/x-javascript |
.m13 |
application/x-msmediaview |
.trm |
application/x-msterminal |
.pml |
application/x-perfmon |
.me |
application/x-troff-me |
.wcm |
application/vnd.ms-works |
.latex |
application/x-latex |
.m14 |
application/x-msmediaview |
.wmf |
application/x-msmetafile |
.cer |
application/x-x509-ca-cert |
.zip |
application/x-zip-compressed |
.p12 |
application/x-pkcs12 |
.pfx |
application/x-pkcs12 |
.der |
application/x-x509-ca-cert |
application/pdf |
|
.xlw |
application/vnd.ms-excel |
.texinfo |
application/x-texinfo |
.p7m |
application/pkcs7-mime |
.pps |
application/vnd.ms-powerpoint |
.dcr |
application/x-director |
.gtar |
application/x-gtar |
.sct |
text/scriptlet |
.fif |
application/fractals |
.exe |
application/octet-stream |
.ppt |
application/vnd.ms-powerpoint |
.sst |
application/vndms-pkicertstore |
.pko |
application/vndms-pkipko |
.scd |
application/x-msschedule |
.tar |
application/x-tar |
.roff |
application/x-troff |
.t |
application/x-troff |
.prf |
application/pics-rules |
.rtf |
application/rtf |
.pot |
application/vnd.ms-powerpoint |
.wdb |
application/vnd.ms-works |
.bcpio |
application/x-bcpio |
.dll |
application/x-msdownload |
.pma |
application/x-perfmon |
.pmr |
application/x-perfmon |
.tr |
application/x-troff |
.src |
application/x-wais-source |
.acx |
application/internet-property-stream |
.cat |
application/vndms-pkiseccat |
.cdf |
application/x-cdf |
.tgz |
application/x-compressed |
.sv4cpio |
application/x-sv4cpio |
.tex |
application/x-tex |
.ustar |
application/x-ustar |
.crt |
application/x-x509-ca-cert |
.ra |
audio/x-pn-realaudio |
.mid |
audio/mid |
.au |
audio/basic |
.snd |
audio/basic |
.wav |
audio/wav |
.aifc |
audio/aiff |
.m3u |
audio/x-mpegurl |
.ram |
audio/x-pn-realaudio |
.aiff |
audio/aiff |
.rmi |
audio/mid |
.aif |
audio/x-aiff |
.mp3 |
audio/mpeg |
.gz |
application/x-gzip |
.z |
application/x-compress |
.tsv |
text/tab-separated-values |
.xml |
text/xml |
.323 |
text/h323 |
.htt |
text/webviewhtml |
.stm |
text/html |
.html |
text/html |
.xsl |
text/xml |
.htm |
text/html |
.cod |
image/cis-cod |
.ief |
image/ief |
.pbm |
image/x-portable-bitmap |
.tiff |
image/tiff |
.ppm |
image/x-portable-pixmap |
.rgb |
image/x-rgb |
.dib |
image/bmp |
.jpeg |
image/jpeg |
.cmx |
image/x-cmx |
.pnm |
image/x-portable-anymap |
.jpe |
image/jpeg |
.jfif |
image/pjpeg |
.tif |
image/tiff |
.jpg |
image/jpeg |
.xbm |
image/x-xbitmap |
.ras |
image/x-cmu-raster |
.gif |
image/gif |
To learn more about MIME types on Microsoft.com, see the following resources: