DOCUMENT:Q216829 19-FEB-1999 [iis] TITLE :How to Write a Client Authentication Certificate to a File PRODUCT :Internet Information Server PROD/VER:winnt:4.0 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Internet Information Server 4.0 ------------------------------------------------------------------------------- SUMMARY ======= Sometimes it may be useful to store a public key certificate for future use. The following ASP code takes the client authentication certificate provided by the client and writes it to a file called c:\Cert.txt. For this to work, you must first configure a virtual directory to use SSL and require a client authentication certificate. You can analyze the certificate using the CERTUTIL tool that ships with the Windows NT Option Pack. For more information on how to do this, please see the following article in the Microsoft Knowledge Base: Q216830 IIS: How to View the Contents of a Certificate The following is the ASP code needed for this to work: <% @Language = VBScript %> <% Response.Buffer = True %> <% 'Instantiate the ASP FileSystemObject in order 'to create a text file Set fs = Server.CreateObject("Scripting.FileSystemObject") 'Create text file using append mode Set outStream = fs.OpenTextFile( "C:\cert.txt", 8, True ) 'Save certificate issuer information to text file outStream.WriteLine( "# Issuer: " & Request.ClientCertificate("Issuer") ) 'Extract certificate subject (user) and account information 'from certificate su = Request.ClientCertificate( "Subject" ) mx = len(su) for x = 1 to mx if mid(su,x,1)=chr(10) or mid(su,x,1)=chr(13) then su=left(su,x-1)+";"+right(su,mx-x) end if next outStream.WriteLine( "# Subject: " & su ) outStream.WriteLine( "# Account: " & Request.ServerVariables("REMOTE_USER") ) 'Extract encrypted certificate text from certificate; encode text as 64-bit data uue = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" outStream.WriteLine( "-----BEGIN CERTIFICATE-----" ) cer = Request.ClientCertificate( "Certificate" ) lcer = len(cer) l = 0 for x = 1 to lcer step 3 a1 = asc(mid(cer,x,1)) if x+1 <= lcer then a2 = asc(mid(cer,x+1,1)) if x+2 <=lcer then a3 = asc(mid(cer,x+2,1)) else a3 = 0 end if else a2 = 0 a3 = 0 end if outStream.Write mid(uue, (a1 and 252)/4 +1 ,1) outStream.Write mid(uue, (a1 and 3)*16 + (a2 and 240)/16 +1 ,1) if x+1 <= lcer then outStream.Write mid(uue, (a2 and 15)*4 + (a3 and 192)/64 +1 ,1) if x+2 <= lcer then outStream.Write mid(uue, (a3 and 63) +1 ,1) else outStream.Write "=" end if else outStream.Write "==" end if l = l +4 if l = 64 then outStream.WriteLine("") l = 0 end if next if l > 0 then outStream.WriteLine( "" ) end if outStream.WriteLine( "-----END CERTIFICATE-----" ) Response.Write "Client certificate information has been received and logged successfully
" %> Additional query words: ====================================================================== Keywords : Technology : kbiisSearch kbiis400 Version : winnt:4.0 Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 1999.