| Basic Info | |
|---|---|
| Media Type | application |
| subtype | vnd.dpgraph |
| Registered? | Yes |
| See also | Parker |
| Extensions | |
Tags: (none)
File Formats: (none)
From: David Parker [[email protected]] Sent: Monday, August 23, 1999 9:29 AM To: [email protected] Subject: Request for MIME media type Application/Vendor Tree - vnd.dpgraph Name : David Parker E-mail : [email protected] MIME media type name : Application MIME subtype name : Vendor Tree - vnd.dpgraph Required parameters : none Optional parameters : charset. A DPGraph file is essentially a US-ASCII file containing programming language commands that generate and display mathematical graphs. However, user comments can be embedded in the file, and those comments can be in any character set that is a superset of US-ASCII. Hence, the optional charset parameter is for the convenience of anyone reading the comments, and is not used by the program that interprets the mathematical graphing commands. Encoding considerations : DPGraph files should be base64-encoded for transmission where transport is not 8-bit clean. Other encodings run the danger of introducing or removing CR's and LF's from files as they are transferred between users on different operating systems, which may cause programs which interpret DPGraph files to miscount the number of lines in the files. Security considerations : Security considerations specific to DPGraph files: 1) "File system" threats: none. The programming language commands in DPGraph files contain no constructs that allow the program to read/write/create/erase or otherwise modify the user's file system. The programming constructs in a DPGraph file are only used to generate and display graphs on the user's screen. 2) "Peripheral device" threats: the programming language commands in DPGraph files contain no constructs for sending data to any peripheral devices (printers and modems, for examples), except for the screen. With regard to possible screen threats, see the "Denial of screen" and "Spoofing" threats below. 3) "System command" threats: none. The programming language commands in DPGraph files contain no constructs for passing commands to the operating system, or for calling any external program. 4) "Persistent state" threats: none. The programming language commands in DPGraph files contain no constructs for changing the persistent state of the user's machine. 5) "Viral" threats: none. DPGraph files contain no binary data except in user comments; all of the programming language commands are in US-ASCII and are processed by an interpreter. Any binary characters embedded in a DPGraph file should simply be flagged as syntax errors if they occur in programming language commands, or should be discarded if they occur in user comments. 6) "Denial of memory" threats: like any other program, an interpreter for DPGraph files requires system memory in order to execute. Using the program language commands in a DPGraph file, it is possible to request graphs that would require a large, approaching infinite, amount of memory. There is no specific defense against this type of threat. Programs that interpret DPGraph files should ensure that there is a way for the user to "kill" the interpreter if it seems to be taking too much memory. 7) "Denial of cycles" threats: using the programming language commands in a DPGraph file, it is possible to request graphs that would require a large, approaching infinite, amount of time to generate. There is no specific defense against this type of threat. Programs that interpret DPGraph files should ensure that there is a way for the user to "kill" the interpreter if a graph seems to be taking too long to display. They should also ensure that their execution priority is such that the cycles consumed don't hamper more critical operating system tasks such as page swapping. 8) "Denial of screen" threats: since DPGraph files are meant to generate graphs to display on the user's screen, it is conceivable that someone might think of a malicious reason to fill someone else's screen with graphs. To help guard against this possibility, an interpreter for displaying DPGraph files should be easy for the user to exit. The programming language commands in a DPGraph file have no constructs for displaying arbitrary data at any position on the screen; DPGraph files can only request the display of graphs inside the boundaries of the interpreter's window. 9) "Spoofing" threats: since DPGraph files are meant to generate graphs to display on the user's screen, it is conceivable that someone might create a graph with the malicious intent of confusing the user about what they are seeing on the screen. To help guard against this possibility, interpreters for DPGraph files should make sure to display the graph inside a window that clearly identifies the interpreter. Here are just two of the many general security threats involved in transmitting files, and running programs to view them, which are not specific to DPGraph files: 1) "Bug" threats: A bug in a program that interprets DPGraph files could conceivably be exploited as a security threat. No such bugs are known. The best way to guard against this type of security problem would be to fix the bug as quickly as possible, and make the fixed copies available to all current users. 2) "File system" threats: someone could transmit a huge DPGraph file with the intention of occupying large amounts of somebody else's storage. Interoperability considerations : None. The format of DPGraph files is independent of the user's computer or operating system. Published specification : The format of DPGraph files is described in the help information supplied with DPGraph 2000, available from www.davidparker.com. Applications which use this media : Two known applications which use DPGraph files are DPGraph 2000, available from www.davidparker.com, and MathWare Cyclone, available from www.mathware.com. Both were programmed by David Parker. Additional information : 1. Magic number(s) : 2. File extension(s) : .dpg .mwc .dpgraph 3. Macintosh file type code : 4. Object identifiers(s) or OID(s) : Person to contact for further information : 1. Name : David Parker 2. E-mail : [email protected] Intended usage : Common Author/Change controller : David Parker, www.davidparker.com, [email protected]