protbas: split off protection functions from unprotbas.

1 files changed, 195 insertions, 0 deletions

diff --git a/protbas.c b/protbas.c
new file mode 100644
index 0000000..e57ead3
--- /dev/null
+++ b/protbas.c
@@ -0,0 +1,195 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <time.h>
+
+#include "bas.h"
+
+int protect_vars = 1;
+int protect_code = 1;
+int shrinktable  = 0;
+int varname_char = 0x9b;
+
+/* 32767 END */
+unsigned char badcode[] = {
+	0xff, 0x7f,   /* line number 32767      */
+	0x00,         /* *bad* next-line offset */
+	0x06,         /* next-statement offset  */
+	0x15,         /* END token              */
+	0x16,         /* end-of-line token      */
+};
+
+void scramble_vars(void) {
+	int i;
+
+	if(!vntable_ok()) {
+		fprintf(stderr, "%s: Program already was variable-protected.\n", self);
+		exit(2);
+	}
+
+	if(shrinktable) {
+		if(verbose) fprintf(stderr, "Shrinking variable name table.\n");
+		adjust_vntable_size((vvstart - 1) - vnstart, (codestart - vvstart) / 8);
+	}
+
+	if(varname_char == -1) srand(time(NULL));
+
+	for(i = vnstart; i < vvstart - 1; i++)
+		if(varname_char == -1)
+			program[i] = (rand() >> 8) & 0xff;
+		else
+			program[i] = varname_char & 0xff;
+
+	if(verbose) {
+		i -= vnstart;
+		if(i) {
+			fprintf(stderr, "Replaced %d byte variable name table with ", i);
+			if(varname_char == -1)
+				fprintf(stderr, "random characters.\n");
+			else
+				fprintf(stderr, "character $%02x.\n", varname_char);
+		} else {
+			fprintf(stderr, "Can't protect variables because there are no variables.\n");
+		}
+	}
+}
+
+/* iterate over all the lines, insert a poisoned line 32767 just
+	before line 32768 */
+void breakcode(void) {
+	int pos = codestart, oldpos = 0;
+	int offset, lineno = -1, tmpno = -1;
+
+	while(pos < filelen) {
+		lineno = tmpno;
+		tmpno = getword(pos);
+		if(tmpno == 32768) {
+			break;
+		} else {
+			offset = program[pos + 2];
+			if(!offset) {
+				fprintf(stderr, "%s: program already was code-protected.\n", self);
+				exit(2);
+			}
+			oldpos = pos;
+			pos += offset;
+		}
+	}
+
+	if(!oldpos) die("Can't protect code because there are no lines of code.");
+	if(lineno == 32767) die("Can't protect code because there is already a line 32767.");
+
+	/* pos is now the start of line 32768, move it up to make room for
+		the new line */
+	offset = sizeof(badcode);
+	memmove(program + pos + offset, program + pos, filelen);
+
+	/* insert new line */
+	memmove(program + pos, badcode, offset);
+
+	if(verbose)
+		fprintf(stderr, "Inserted line 32767 with invalid offset at file offset $%04x.\n", pos);
+
+	/* update pointers that would be affected by the code move */
+	stmcur += offset;
+	starp += offset;
+	filelen += offset;
+	update_header();
+	parse_header();
+}
+
+void print_help(void) {
+	fprintf(stderr, "Usage: %s [-v] [-nc|-nv] [-s] [-x[r|NN]] <inputfile> <outputfile>\n", self);
+	fprintf(stderr, "  -v: Verbose.\n");
+	fprintf(stderr, " -nc: Don't protect code.\n");
+	fprintf(stderr, " -nv: Don't protect variable names.\n");
+	fprintf(stderr, "  -s: Shrink variable name table to min size.\n");
+	fprintf(stderr, "-xNN: Hex code NN for variable names.\n");
+	fprintf(stderr, " -xr: Random variable names.\n");
+	fprintf(stderr, "Use - as a filename to read from stdin and/or write to stdout.\n");
+}
+
+void parse_args(int argc, char **argv) {
+	int opt, xopt_used = 0;
+
+	while( (opt = getopt(argc, argv, "vn:x:s")) != -1) {
+		switch(opt) {
+			case 'v': verbose = 1; break;
+			case 's': shrinktable = 1; break;
+			case 'n':
+				switch(optarg[0]) {
+					case 'c': protect_code = 0; break;
+					case 'v': protect_vars = 0; break;
+					default:
+						die("Invalid argument for -n (must be 'c' or 'v').");
+				}
+				break;
+			case 'x':
+				xopt_used = 1;
+				switch(optarg[0]) {
+					case 'r':
+						varname_char = -1; break;
+					case 0:
+						die("-x option requires a hex number or 'r'."); break;
+					default:
+						{
+							char *e;
+							varname_char = (int)strtol(&(*argv)[2], &e, 16);
+							if(*e != 0 || varname_char > 0xff)
+								die("Invalid hex value for -x option (range is 0 to ff).");
+						}
+				}
+				break;
+			default:
+				print_help();
+				exit(1);
+		}
+	}
+
+	if(!protect_code && !protect_vars) {
+		die("Nothing to do: -nc and -nv both given.");
+	}
+
+	if(!protect_vars) {
+		if(xopt_used)
+			die("-x option not valid with -nv.");
+		if(shrinktable)
+			die("-s option not valid with -nv.");
+	}
+
+	if(optind >= argc)
+		die("No input file given (use - for stdin).");
+	else
+		open_input(argv[optind]);
+
+	if(++optind >= argc)
+		die("No output file given (use - for stdout).");
+	else
+		output_filename = argv[optind];
+}
+
+int main(int argc, char **argv) {
+	set_self(*argv);
+	parse_general_args(argc, argv, print_help);
+	parse_args(argc, argv);
+	readfile();
+	parse_header();
+
+	if(verbose) {
+		fprintf(stderr, "Protecting program, ");
+		if(protect_vars && !protect_code)
+			fprintf(stderr, "variables only.\n");
+		else if(protect_code && !protect_vars)
+			fprintf(stderr, "code only.\n");
+		else
+			fprintf(stderr, "both code and variables.\n");
+	}
+	if(protect_vars) scramble_vars();
+	if(protect_code) breakcode();
+
+	open_output(output_filename);
+	writefile();
+	return 0; /* TODO: meaningful return status */
+}