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ColdFusion 10: CFFILE Restricting file types to upload

In ColdFusion 10, one can restrict the type of file being uploaded to the server when using CFFILE to upload the files. The new attribute accept allows the user to specify various MIME types or extensions of the file that can be accepted by the server. If the user tries to upload a file with a .txt extension but it contains xml data (application/xml MIME type) then the server would accept or throw an exception based on the value specified for the strict attribute. 'strict' is a boolean attribute added to the CFFILE tag. By default it is true and therefore wouldn't allow the user to upload a file whose contents are of different MIME type. When the strict attribute is set to false it would allow the user to upload a file irrespective of its content. However, an error would be thrown if the extension of the file doesn't match the ones specified in the accept attribute.


Rules:
  1. When strict is true, only MIME types or a combination of MIME types and extensions are allowed in the accept attribute. Since strict is true by default, one should specify MIME types for the accept attribute.
  2. When strict is false, either MIME types or extensions or a combination of both can be specified as a value to the accept attribute.

Example:

<!--- Create a directory where files would be uploaded ---> <cfif not directoryExists(expandPath("./uploadDirectory"))> <cfset directoryCreate(expandPath("./uploadDirectory"))> </cfif> <cfif isDefined("form.myFile")> <cftry> <!--- A valid MIME type must be specified as a value for accept attribute when strict=true. By default strict is true. ---> <cffile action="upload" destination="#expandPath("./uploadDirectory")#" accept="text/plain" filefield="form.myFile" nameconflict="overwrite" strict="true"> File uploaded successfully. <cfcatch type="Any"> <!--- If the text file contains data of a different mime type; ex: application/xml, then an error is thrown. ---> Problem uploading file: <br/> Error message - <cfoutput>#cfcatch.message#</cfoutput> <br/> Error detail - <cfoutput>#cfcatch.detail#</cfoutput> <br/> </cfcatch> </cftry> <cfelse> <cfform method="post" enctype="multipart/form-data"> <cfinput name="myFile" type="file"> <cfinput name="submitBtn" type="submit"> </cfform> </cfif>

When specifying extensions, the . prefix is required i.e. .TXT,.XML etc,. To accept all file types one can specify the wild card '*'.

fileGetMimeType

A new function fileGetMimeType has been added to determine the MIME type of the file:

<cfscript> //if test.txt contains xml data then the MIME type would be application/xml writeOutput(fileGetMimeType(expandPath("test.txt")) & "<br />"); //when strict=false, this would output text/plain writeOutput(fileGetMimeType(expandPath("test.txt"),false) & "<br />"); //try with the file object myFile = fileOpen(expandPath("test.txt")); writeOutput(fileGetMimeType(myFile,false) & "<br />"); </cfscript>

The first argument to fileGetMimeType function can be a path to a file or a file object. The second argument - 'strict' is an optional argument. By default it's value is true. When strict is true this function would return the mimetype after examining the content of the file. When it is set to false, it would just examine the file extension and return the mimetype.
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