User authentication callback function

When using the DATABASE (or CONNECT TO without the USER/USING clause) instruction, the database user name and password can be provided at runtime by a callback function. The callback function must be defined with the dbi.default.userauth.callback FGLPROFILE entry:
dbi.default.userauth.callback = "[module-name.]function-name"
This callback method is provided when a lot of programs use the DATABASE instruction, and database user credentials are mandatory. If possible, use the CONNECT TO instruction with the USER/USING clause instead of DATABASE.

With the IBM® Informix® driver, when using the DATABASE instruction, the callback method is invoked, but the user name and password returned by the function are ignored: Only CONNECT TO will take the login parameters into account for IBM Informix, when no USER/USING clause is specified.

The callback function must have the following signature:

CALL function-name(dbspec STRING)
      RETURNS ( STRING, -- username
                STRING  -- password

If you do not specify the module name, the callback function must be linked to the 42r program. By using the "module-name.function-name" syntax in the FGLPROFILE entry, the runtime system will automatically load the module. In both cases, the module must be located in a directory where the runtime system can find it, defined by the FGLLDPATH environment variable.

In the callback function body, the value of dbspec can be used to identify the database source, read user name and encrypted password from FGLPROFILE entries with the fgl_getResource() function, then decrypt password with the algorithm of your choice and return user name and decrypted password.

User authentication callback function for DATABASE:

  LET un = fgl_getResource("dbi.database."||dbspec||".username") 
  LET ep = fgl_getResource("dbi.database."||dbspec||".password.encrypted")
  RETURN un, decrypt_user_password(dbspec, un, ep)