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uru4k: decrypt image if necessary

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Add naive detection of image encryption: if stddev between two
adjacent rows is higher than threshold assume that image is encrypted
and decrypt it.

Fixes fd.o bug 88945
This commit is contained in:
Vasily Khoruzhick 2016-07-18 20:46:20 -07:00
parent a1f36c71c9
commit 2162aa9f48
1 changed files with 38 additions and 3 deletions
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41
libfprint/drivers/uru4000.c
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@ -45,6 +45,8 @@
#define IMAGE_HEIGHT 290 #define IMAGE_HEIGHT 290
#define IMAGE_WIDTH 384 #define IMAGE_WIDTH 384
#define ENC_THRESHOLD 1000
enum { enum {
IRQDATA_SCANPWR_ON = 0x56aa, IRQDATA_SCANPWR_ON = 0x56aa,
IRQDATA_FINGER_ON = 0x0101, IRQDATA_FINGER_ON = 0x0101,
@ -664,6 +666,34 @@ static uint32_t do_decode(uint8_t *data, int num_bytes, uint32_t key)
return update_key(key); return update_key(key);
} }
static int calc_dev2(struct uru4k_image *img)
{
uint8_t *b[2] = { NULL, NULL };
int res = 0, mean = 0, i, r, j, idx;
for (i = r = idx = 0; i < array_n_elements(img->block_info) && idx < 2; i++) {
if (img->block_info[i].flags & BLOCKF_NOT_PRESENT)
continue;
for (j = 0; j < img->block_info[i].num_lines && idx < 2; j++)
b[idx++] = img->data[r++];
}
if (!b[0] || !b[1]) {
fp_dbg("NULL! %p %p", b[0], b[1]);
return 0;
}
for (i = 0; i < IMAGE_WIDTH; i++)
mean += (int)b[0][i] + (int)b[1][i];
mean /= IMAGE_WIDTH;
for (i = 0; i < IMAGE_WIDTH; i++) {
int dev = (int)b[0][i] + (int)b[1][i] - mean;
res += dev * dev;
}
return res / IMAGE_WIDTH;
}
static void imaging_run_state(struct fpi_ssm *ssm) static void imaging_run_state(struct fpi_ssm *ssm)
{ {
struct fp_img_dev *dev = ssm->priv; struct fp_img_dev *dev = ssm->priv;
@ -672,7 +702,7 @@ static void imaging_run_state(struct fpi_ssm *ssm)
struct fp_img *fpimg; struct fp_img *fpimg;
uint32_t key; uint32_t key;
uint8_t flags, num_lines; uint8_t flags, num_lines;
int i, r, to; int i, r, to, dev2;
char buf[5]; char buf[5];
switch (ssm->cur_state) { switch (ssm->cur_state) {
@ -698,8 +728,13 @@ static void imaging_run_state(struct fpi_ssm *ssm)
return; return;
} }
if (!urudev->profile->encryption) { if (!urudev->profile->encryption) {
fpi_ssm_jump_to_state(ssm, IMAGING_REPORT_IMAGE); dev2 = calc_dev2(img);
return; fp_dbg("dev2: %d", dev2);
if (dev2 < ENC_THRESHOLD) {
fpi_ssm_jump_to_state(ssm, IMAGING_REPORT_IMAGE);
return;
}
fp_info("image seems to be encrypted");
} }
buf[0] = img->key_number; buf[0] = img->key_number;
buf[1] = urudev->img_enc_seed; buf[1] = urudev->img_enc_seed;