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Securing Connection Strings

Today, again I came across the same scenario about which my colleague Sam had asked me once. He asked me about best practices for securing the connection strings. Well, for securing the Database connection string file. The general approach will be-irrespective of technology- its’ best practice to move the credentials out of source-code into a configuration file. It needs to be properly protected, using strong ACLs and strong encryption with properly protected keys. I shall give you an example of .NET which I am aware of and you can suggest developers to use the similar thing for Oracle and jsp pages.

Again there are different approaches for different technologies- for ASP.Net you can either use Windows authentication instead of using username/password, database (connection string) name in the source code. But that’s not possible, if you have got to mention the username/password, database name, put them in a separate configuration file such as app.config or web.config and encrypt them using various ways available in .NET such as, protected configuration:
The following configuration file fragment shows the connectionStrings section after it has been encrypted:

<connectionStrings configProtectionProvider="DataProtectionConfigurationProvider">
<EncryptedData>
<CipherData>
<CipherValue>AHHJHJh9w+++kdjkdkUIosdndns…. </CipherValue>
</CipherData>
</EncryptedData>
</connectionStrings>

When the encrypted connection string is retrieved at run time, the .NET Framework uses the specified provider to decrypt the CipherValue and make it available to your application. You do not need to write any additional code to manage the decryption process.
The bottom line is that don’t store them in source code and you have to encrypt the configuration file containing connection string. Tell them to put the connection string in configuration file and encrypt it. Again, they have to pay attention to key management. This is the best available solution however, it may be tailored as per the their needs.

His other query was about SSL if that can be used to connections between application and database servers.
Here there are two scenarios, first the app server and database server are on the same machine. In case of protecting connection between application server and database server doesn’t make any sense as the connection is not exposed to the public. Also, the application server and DB server both can be on same machine or separate machines. SSL is only used between application server/DB server machine and user browser to prevent Man in the Middle attacks like sniffing.
In worst case, if application server gets compromised (application vulnerabilities may be main culprit) SSL won’t do anything as the connection string if not encrypted can be easily read by the hacker.

Regarding the second scenario,one situation I may think of, if the both app server and DB server are on different sites. But in that case also, only the connection string credentials in transit can be protected with SSL, can’t be protected when app server is compromised.
The best bet is to encrypt the connection string file itself.


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