diff options
| -rw-r--r-- | unprotbas.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/unprotbas.c b/unprotbas.c index 0b11e0e..16fbea5 100644 --- a/unprotbas.c +++ b/unprotbas.c @@ -16,6 +16,12 @@ #define STM_OFFSET 0xf2 +/* minimum program size, for a program that has no variables and + only one line of code (the immediate line 32768, consisting only of + one token, which would be CSAVE). anything smaller than this, we + can't process. */ +#define MIN_PROG_SIZE 21 + /* entire file gets read into memory (for now) */ unsigned char data[65536]; @@ -60,6 +66,8 @@ int readfile(void) { int got = fread(data, 1, 65535, input_file); if(verbose) fprintf(stderr, "read %d bytes\n", got); fclose(input_file); + if(got < MIN_PROG_SIZE) + die("File too short to be a BASIC program (truncated?)\n"); return got; } @@ -194,7 +202,14 @@ int fixcode(void) { by moving the rest of the program (including the variable value table) up in memory. */ void move_code(int offset) { - memmove(data + vvstart + offset, data + vvstart, filelen); + unsigned char *dest = data + vvstart + offset; + + if(dest < data || (filelen + offset) > 65535) { + die("attempt to move memory out of range; corrupt header bytes?\n"); + } + + memmove(dest, data + vvstart, filelen); + vntd += offset; vvtp += offset; stmtab += offset; |