Finalized rm hack

["Alex Kirk" <alex@schnarff.com>]

Thanks to everyone for their comments on my rm hack. I appreciate the 
feedback, particularly the positive stuff. ;-) 

I'm submitting below two diffs: one that represents the changes from the 
current rm.c, and one that represents changes between the version I 
submitted last night and the finalized version. That way, if you've already 
patched, you can apply the new patch, and if you've not, you can get up to 
speed in one step. 

By way of explanation, what I did was read the article pointed out by Damien 
Miller on secure deletion, and then incorporate in the values they suggested 
into my loop. They're listed out (in decimal instead of hex for simplicity's 
sake) in owv[]; my loop goes through and pulls from them, using an entirely 
random value from 0-256 every 2-10 loops through (2 so that it's not all 
random values, 10 so that some randomness is incorporated into most 
overwrites). I'm hoping I've structured my loop properly to acheive this 
effect; it seemed to work in testing. 

Barring any further bugs discovered by you folks, I'd like to see this added 
to -current. How would I go about having that happen? 

Thanks,
Alex
68a69
> long owrite;
89a91,92
> 	extern char *optarg;
> 	char *endptr;
94c97
< 	while ((ch = getopt(argc, argv, "dfiPRrW")) != -1)
---
> 	while ((ch = getopt(argc, argv, "dfiPRrWo:")) != -1)
116a120,125
> 		case 'o':
> 			Pflag = 1;
> 			owrite = strtol(optarg, &endptr, 10);
> 			if (optarg[0] == 0 || *endptr != '\0')
> 				usage();
> 			break;
299c308
<  *	Overwrite the file 3 times with varying bit patterns.
---
>  *	Overwrite the file with varying bit patterns.
306a316,321
>  *
>  * The values in owv[] were taken from the article at
>  * http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html, as those
>  * which would give the highest probability of a fully secure overwrite.
>  * It should be noted, however, that even when using these values, complete
>  * deletion cannot be absolutely ensured.
317a333,335
>         int z, y;
> 	int owv[] = {146, 73, 36, 0, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204, 221, 238, 255, 109, 182, 219};
> 	srand(time(NULL));
343,348c361,377
< 	PASS(0xff);
< 	if (fsync(fd) || lseek(fd, (off_t)0, SEEK_SET))
< 		goto err;
< 	PASS(0x00);
< 	if (fsync(fd) || lseek(fd, (off_t)0, SEEK_SET))
< 		goto err;
---
> 	if (owrite == NULL)
> 		y = 2;
> 	else
> 		y = (owrite - 1);
> 	for (z = 0; z < y; z++)
> 		{
> 		if (z/((rand()%10) + 1) == 1)
> 			{
> 			PASS((rand())%256);
> 			}
> 		else
> 			{
> 			PASS(owv[(rand()%22)]);
> 			}
> 		if (fsync(fd) || lseek(fd, (off_t)0, SEEK_SET))
> 			goto err;
> 		}
441c470
< 	(void)fprintf(stderr, "usage: rm [-dfiPRrW] file ...\n");
---
> 	(void)fprintf(stderr, "usage: rm [-dfiPRrWo] [n] file ...\n");
308c308
<  *	Overwrite the file 3 times with varying bit patterns.
---
>  *	Overwrite the file with varying bit patterns.
315a316,321
>  *
>  * The values in owv[] were taken from the article at
>  * http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html, as those
>  * which would give the highest probability of a fully secure overwrite.
>  * It should be noted, however, that even when using these values, complete
>  * deletion cannot be absolutely ensured.
327a334,335
> 	int owv[] = {146, 73, 36, 0, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204, 221, 238, 255, 109, 182, 219};
> 	srand(time(NULL));
359c367,374
< 		PASS(0xee);
---
> 		if (z/((rand()%10) + 1) == 1)
> 			{
> 			PASS((rand())%256);
> 			}
> 		else
> 			{
> 			PASS(owv[(rand()%22)]);
> 			}