Bad request with base64 encoded parameter in WCF rest url on IIS 7 - wcf

Question

I have a rest wcf 4.0 service that takes in a base64 encoded string as a parameter. It works properly when I run the service in Visual Studio using casini, but gives an Error 400 message when I run the same service under IIS 7.5. The break point doesn't get hit. I guess its not a problem with the code because it works under casini with the same code and web.config.
What changes do I need to make to enable the service to function under IIS 7.5?
This is the URL
http://localhost/MyServices/MyServ.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
Thanks.

Answer 1

The equal sign has a special meaning in the URL. It separates a parameter key from its value. The way you use the trailing equal signs, IIS will reject it.
Note that the Base 64 encoding uses additional characters that have a special meaning in a URL and cause problems (namely + and /). Therefore I recommend to use a modified Base 64 encoding that uses only URL safe characters.
Typically, the following characters are replaced:
+ with -,
/ with _, and
= with *.
Update:
The Javascript code you use for Base 64 encoding is easy to modify. Just replace this line:
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
with
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_*";
And
return (r ? enc.slice(0, r - 3) : enc) + '==='.slice(r || 3);
with:
return (r ? enc.slice(0, r - 3) : enc) + '***'.slice(r || 3);
Update 2:
I'm afraid the Base 64 URLs are never going to work with IIS. IIS still treats every part of an URL as a file or directory name. There are many problems with this implementation (just try COM2 or PRN as a URL segment).
You'll need to come up with a different URL scheme or request type. Either use a POST request to transmit the Base64 encoded part or use a URL like:
http://server/MyServices/MyServ.svc/Accept?data=eyJXb3JkY291bnQiOjMwLCJ...VsbH1dfQ**
But the second case will only work if the URL isn't too long. It wouldn't expect URLs of more than 1000 characters to work.