Description of problem:

  smbspool is unable to authenticate to Windows print server using
  username/password passed through DEVICE_URI environment variable.

How reproducible:

  100%

Steps to Reproduce:

 1. Configure CUPS print queue with a username password combination:

    lpadmin -p smbtest -v 'smb://user:password@host/printer' -E
      
 2. Try to print to the printer

    lp -d smbtest /etc/fstab

Actual results:

  The print job fails with the following messages in the CUPS error_log:

    Started backend /usr/lib/cups/backend/smb (PID 14556)
    get_exit_code(nt_status=NT_STATUS_INVALID_ACCOUNT_NAME [c0000062])
    ATTR: auth-info-required=username,password
    PID 14556 (/usr/lib/cups/backend/smb) stopped with status 2.
    Unable to connect to CIFS host: NT_STATUS_INVALID_ACCOUNT_NAME
 
Expected results:

  File should print

Additional info:

  When smbspool is run directly from the command line, i.e.:

    smbspool 'smb://user:password@host/printer' 1 user test 1 "" /etc/fstab

  then the file is printed correctly.  The problem is:

  * CUPS provides the Device URI (which should contain the
    username/password) through argv[0] (yes, I know that's weird) and
    through the DEVICE_URI environment variable.

  * The Device URI passed through argv[0] is "sanitized" so that the
    username and password is removed.  This is most likely done so that
    the username/password isn't visible in the process information,
    which could be easily accessed by ps or similar commands.

  * smbspool searches argv[0], argv[1], and DEVICE_URI for the Device
    URI, but if it finds something in argv[0], it won't use the
    information in DEVICE_URI.

  As a result, smbspool uses the sanitized Device URI in argv[0] instead
  of the Device URI in DEVICE_URI that has the login credentials.  Since
  the sanitized URI doesn't have the credentials, print job transfer to
  Windows fails.

  The proposed patch changes smbspool to primarily use DEVICE_URI and
  only use argv[0] or argv[1] if DEVICE_URI is nonexistent or empty.
  I've done some quick tests to verify that the patch does re-enable
  CUPS printing to a Windows server using username/password authentication.

  As an aside, CUPS never passes the Device URI through argv[1], but
  this mechanism is _very_ useful for testing purposes (like in the
  smbspool command above).

  This worked prior to Commit 69d7a496, which swizzled the URI logic
  around a bit.  Commit 69d7a496 made the URI handling much cleaner,
  but introduced this regression.

  Proposed patch to be attached later today.