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cochran: do a partial header de-scramble

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This descrambles at least parts of the header data.  Some of it has the
same pattern of data 4kB apart, it may be that there is a dive hiding in
there too (ie what I currently call a "header" may in fact be a header
_plus_ a dive).

But the 4kB thing may well be an artifact of the crazy scrambling code
itself.  Who knows what kind of chunking the Cochran Analyst
"encryption" uses.

As with the dive data, there seems to be some offset differences between
different CAN files.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2012-01-27 15:11:34 -08:00
parent 5bc3ba5e95
commit 1a66a74e8a
1 changed files with 46 additions and 10 deletions
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56
cochran.c
View file

@ -79,7 +79,7 @@ static int figure_out_modulus(const unsigned char *decode, const unsigned char *
#define hexchar(n) ("0123456789abcdef"[(n)&15])
static void show_line(unsigned offset, const unsigned char *data, unsigned size)
static int show_line(unsigned offset, const unsigned char *data, unsigned size, int show_empty)
{
unsigned char bits;
int i, off;
@ -105,18 +105,51 @@ static void show_line(unsigned offset, const unsigned char *data, unsigned size)
asc[1] = 0;
}
if (bits)
if (bits) {
puts(buffer);
return 1;
}
if (show_empty)
puts("...");
return 0;
}
static void cochran_debug_write(const char *filename, int dive, const unsigned char *data, unsigned size)
static void cochran_debug_write(const char *filename, const unsigned char *data, unsigned size)
{
int i;
printf("\n%s, dive %d\n\n", filename, dive);
int i, show = 1;
for (i = 0; i < size; i += 16) {
show_line(i, data + i, size - i);
}
for (i = 0; i < size; i += 16)
show = show_line(i, data + i, size - i, show);
}
static void parse_cochran_header(const char *filename,
const unsigned char *decode, unsigned mod,
const unsigned char *in, unsigned size)
{
char *buf = malloc(size);
/* Do the "null decode" using a one-byte decode array of '\0' */
partial_decode(0 , 0x0b14, "", 0, 1, in, size, buf);
/*
* The header scrambling is different form the dive
* scrambling. Oh yay!
*/
#if 0 // Alex
partial_decode(0x058c, 0x0b14, decode, 0, mod, in, size, buf);
#else // Don
partial_decode(0x05a0, 0x0b14, decode, 0, mod, in, size, buf);
#endif
partial_decode(0x0b14, 0x1b14, decode, 0, mod, in, size, buf);
partial_decode(0x1b14, 0x2b14, decode, 0, mod, in, size, buf);
partial_decode(0x2b14, 0x3b14, decode, 0, mod, in, size, buf);
partial_decode(0x3b14, 0x5414, decode, 0, mod, in, size, buf);
partial_decode(0x5414, size, decode, 0, mod, in, size, buf);
printf("\n%s, header\n\n", filename);
cochran_debug_write(filename, buf, size);
free(buf);
}
static void parse_cochran_dive(const char *filename, int dive,
@ -150,7 +183,8 @@ static void parse_cochran_dive(const char *filename, int dive,
partial_decode(0x4a14, 0xc9bd, decode, 0, mod, in, size, buf);
partial_decode(0xc9bd, size, decode, 0, mod, in, size, buf);
cochran_debug_write(filename, dive, buf, size);
printf("\n%s, dive %d\n\n", filename, dive);
cochran_debug_write(filename, buf, size);
free(buf);
}
@ -172,6 +206,8 @@ int try_to_open_cochran(const char *filename, struct memblock *mem, GError **err
mod = figure_out_modulus(decode, mem->buffer + dive1, dive2 - dive1);
parse_cochran_header(filename, decode, mod, mem->buffer + 0x40000, dive1 - 0x40000);
for (i = 0; i < 65534; i++) {
dive1 = offsets[i];
dive2 = offsets[i+1];
@ -179,7 +215,7 @@ int try_to_open_cochran(const char *filename, struct memblock *mem, GError **err
break;
if (dive2 > mem->size)
break;
parse_cochran_dive(filename, i, decode, mod, mem->buffer + dive1, dive2 - dive1);
parse_cochran_dive(filename, i+1, decode, mod, mem->buffer + dive1, dive2 - dive1);
}
exit(0);