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| Phrack Seventeen | |
| 07 April 1988 | |
| File 6 of 12 : How to Hack HP2000's | |
| How to Hack an HP 2000 | |
| By: ** Grey Sorcerer | |
| Okay, so you've read the HP-2000 basic guides, and know your way around. I | |
| will not repeat all that. | |
| There's two or three things I've found that allow you through HP 2000 | |
| security. | |
| 1. When you log in, a file called HELLO on the user number Z999 is run. A lot | |
| of time this file is used to deny you access. Want in? Well, it's just a | |
| BASIC program, and an be BREAKed.. but, usually the first thing they do in | |
| that program is turn Breaks (interrupts) off by the BRK(0) function. However, | |
| if you log in like this: | |
| HELLO-D345,PASS (return) (break) | |
| With the break nearly instantly after the return, a lot of time, you'll abort | |
| the HELLO program, and be home free. | |
| 2. If you can create a "bad file", which takes some doing, then anytime you | |
| try to CSAVE this file (compile and save), the system will quickly fade into a | |
| hard crash. | |
| 3. How to make a bad file and other goodies: | |
| The most deadly hole in security in the HP2000 is the "two terminal" method. | |
| You've got to understand buffers to see how it works. When you OPEN a file, | |
| or ASSIGN it (same thing), you get 256 bytes of the file -- the first 256. | |
| When you need anymore, you get 256 more. They are brought in off the disk in | |
| discrete chunks. They are stored in "buffers." | |
| So. Save a bunch of junk to disk -- programs, data, whatever. Then once your | |
| user number is full, delete all of it. The effect is to leave the raw jumbled | |
| data on disk. | |
| Pick a time when the system is REAL busy, then: | |
| 1. Have terminal #1 running a program that looks for a file to exist (with the | |
| ASSIGN) statement as quickly as it can loop. If it finds the file there, it | |
| goes to the very end of the file, and starts reading backwards, record by | |
| record, looking for data. If it finds data, it lets you know, and stops at an | |
| input prompt. It is now running. | |
| 2. Have terminal #2 create a really huge data file (OPEN-FILE, 3000) or | |
| however it goes. | |
| What happens is terminal #2's command starts zeroing all the sectors of the | |
| file, starting at file start. But it only gets so far before someone else | |
| needs the processor, and kicks #2 out. The zeroing stops for a sec. Terminal | |
| #1 gets in, finds the file there, and reads to the end. What's there? Old | |
| trash on disk. (Which can be mighty damned interesting by the way -- did you | |
| know HP uses a discrete mark to indicate end-of-buffer? You've just maybe got | |
| yourself a buffer that is as deep as system memory, and if you're clever, you | |
| can peek or poke anywhere in memory. If so, keep it, it is pure gold). | |
| But. Back to the action. | |
| 3. Terminal #2 completes the OPEN. He now deletes the file. This leaves | |
| Terminal #1 with a buffer full of data waiting to be dumped back to disk at | |
| that file's old disk location. | |
| 4. Terminal #2 now saves a load of program files, as many as are required to | |
| fill up the area that was taken up by the deleted big file. | |
| 5. You let Terminal #1 past the input prompt, and it writes its buffer to | |
| disk. This promptly overlays some program just stored there. Result: "bad | |
| program." HPs are designed with a syntax checker and store programs in token; | |
| a "bad program" is one that the tokens are screwed up in. Since HP assumes | |
| that if a program is THERE, it passed the syntax check, it must be okay... | |
| it's in for big problems. For a quick thrill, just CSAVE it.. system tries | |
| to semi-compile bad code, and drops. | |
| Really, the classier thing to do with this is to use the "bottomless buffer" | |
| to look through your system and change what you don't like.. maybe the | |
| password to A000? Write some HP code, look around memory, have a good time. | |
| It can be done. | |
| ** Grey Sorcerer | |