TFTP Server Configuration Security via DHCP Authentication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing broadband data services face unauthorized use due to the inherent security weakness in the interactions between trivial file transfer protocol (TFTP) servers and cable modems, where configuration files can be easily retrieved and modified by users to access unauthorized services.
Innovation Solution
The solution involves transmitting cable modem configuration file names from the DHCP server in a disguised or encrypted form, using unique authorization keys and a coordination pass phrase, ensuring that only valid cable modems can request files from the TFTP server, thereby preventing unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If TFTP servers transmit configuration files to cable modems using standard protocols, then cable modems can retrieve configuration files easily, but unauthorized users can also access and modify these files to gain unauthorized service access
Solution Approach 1:
The patent introduces an intermediary authentication mechanism between the TFTP server and cable modems. The DHCP server acts as a mediator that generates authenticated configuration file names incorporating authorization keys, which are then used by the TFTP server to verify legitimate requests. This intermediary layer prevents unauthorized access while maintaining ease of operation for authorized devices.
Solution Approach 2:
The patent transforms the configuration file name parameter from a plain text identifier into an authenticated token that includes encryption elements and authorization keys. By changing the parameter structure of the file name to include security credentials, the system enables both easy retrieval for authorized modems and protection against unauthorized access.
2Productivity
If configuration files are stored on TFTP servers with standard access protocols, then cable modems can download files efficiently, but security vulnerabilities allow users to retrieve and modify files for service abuse
Solution Approach 1:
The patent implements preliminary authentication actions during the DHCP phase, before the actual file transfer occurs. The configuration file name is pre-authenticated with authorization keys and encryption elements during the DHCP handshake. This preliminary security action ensures that subsequent fast TFTP transfers are performed only by authorized devices, maintaining both productivity and reliability.
3Device complexity
If TFTP servers allow open access to configuration files, then system complexity remains low and implementation is simple, but security weaknesses enable unauthorized service access
Solution Approach 1:
The patent makes the DHCP server multi-functional by having it perform both its traditional IP address assignment role and the additional function of generating authenticated configuration file names. This universal approach allows the system to gain security capabilities without adding dedicated new hardware or complex systems, thus maintaining low implementation complexity while eliminating security weaknesses.
Data Source
AI summary
The present invention teaches methods and systems for blocking unauthorized access to cable modem configuration files stored on trivial file transfer protocol (TFTP) servers. Filenames are modified by the DHCP to incorporate an authentication key (and optional cloaking) prior to transmission to the cable modem. When the TFTP server receives a modified filename, it also generates an authentication key. The authentication keys must match in order for the cable modem to receive the configuration file requested. At a minimum, authentication keys depend upon the un-modified filename, the cable modem IP address and a “coordination pass phrase” known to the TFTP server and DHCP server, but not known to the cable modem. Variations include optional cloaking, various actions performed for non-matching authentication keys, selection of authentication key generating algorithm and inclusion of cable modem MAC address in the authentication key for all cable modems or for premium service customer cable modems.