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Fix checking change address

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There was a signed/unsigned problem: size_t is unsigned, but we use
-1 to indicate mismatch.  The problem was that when checking the input
address path, it still did this unintentionally when a mismatch was
detected, forbidding to sign with mismatched inputs, even when there
is no change address.

We now use 1 for mismatch.  Also we don't allow change address anymore
if the inputs have a path of length 1.  This simplifies the code a bit.
This commit is contained in:
Jochen Hoenicke 2017-10-10 16:05:42 +02:00 committed by Pavol Rusnak
parent 5e98b0ffd6
commit 4805f27e8c
1 changed files with 25 additions and 37 deletions
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62
firmware/signing.c
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@ -68,6 +68,12 @@ static uint8_t multisig_fp[32];
static uint32_t in_address_n[8];
static size_t in_address_n_count;
/* marker for in_address_n_count to indicate a mismatch in bip32 paths in
input */
#define BIP32_NOCHANGEALLOWED 1
/* maximum allowed change index */
#define MAX_BIP32_LAST_ELEMENT 1000000
enum {
SIGHASH_ALL = 1,
SIGHASH_FORKID = 0x40,
@ -328,61 +334,45 @@ void phase2_request_next_input(void)
void extract_input_bip32_path(const TxInputType *tinput)
{
if (in_address_n_count == (size_t) -1) {
if (in_address_n_count == BIP32_NOCHANGEALLOWED) {
return;
}
size_t count = tinput->address_n_count;
if (count < 1) {
if (count < 2) {
// no change address allowed
in_address_n_count = (size_t) -1;
in_address_n_count = BIP32_NOCHANGEALLOWED;
return;
}
if (in_address_n_count == 0) {
// initialize in_address_n on first input seen
in_address_n_count = count;
if (count > 2) { // if longer than 2 elements, store first N - 2
memcpy(in_address_n, tinput->address_n, (count - 2) * sizeof(uint32_t));
}
// store first N - 2
memcpy(in_address_n, tinput->address_n, (count - 2) * sizeof(uint32_t));
return;
}
// check whether they are same length
if (in_address_n_count != count) {
in_address_n_count = (size_t) -1;
in_address_n_count = BIP32_NOCHANGEALLOWED;
return;
}
if (count > 2 && memcmp(in_address_n, tinput->address_n, (count - 2) * sizeof(uint32_t)) != 0) {
if (memcmp(in_address_n, tinput->address_n, (count - 2) * sizeof(uint32_t)) != 0) {
// mismatch -> no change address allowed
in_address_n_count = (size_t) -1;
in_address_n_count = BIP32_NOCHANGEALLOWED;
return;
}
}
#define MAX_BIP32_LAST_ELEMENT 1000000
bool check_change_bip32_path(const TxOutputType *toutput)
{
size_t count = toutput->address_n_count;
if (count < 1 || in_address_n_count < 1) {
return 0;
}
if (count != in_address_n_count) {
return 0;
}
if (toutput->address_n[count - 1] > MAX_BIP32_LAST_ELEMENT) {
return 0;
}
if (count >= 2) {
if (0 != memcmp(in_address_n, toutput->address_n, (count - 2) * sizeof(uint32_t)) ||
toutput->address_n[count - 2] != 1) {
return 0;
}
}
return 1;
// Note: count >= 2 and count == in_address_n_count
// imply that in_address_n_count != BIP32_NOCHANGEALLOWED
return (count >= 2
&& count == in_address_n_count
&& 0 == memcmp(in_address_n, toutput->address_n, (count - 2) * sizeof(uint32_t))
&& toutput->address_n[count - 2] == 1
&& toutput->address_n[count - 1] <= MAX_BIP32_LAST_ELEMENT);
}
bool compile_input_script_sig(TxInputType *tinput)
@ -397,14 +387,12 @@ bool compile_input_script_sig(TxInputType *tinput)
return false;
}
}
if (in_address_n_count >= 1) {
if (in_address_n_count != BIP32_NOCHANGEALLOWED) {
// check that input address didn't change
size_t count = tinput->address_n_count;
if (count != in_address_n_count) {
return false;
}
if (count >= 2
&& 0 != memcmp(in_address_n, tinput->address_n, (count - 2) * sizeof(uint32_t))) {
if (count < 2
|| count != in_address_n_count
|| 0 != memcmp(in_address_n, tinput->address_n, (count - 2) * sizeof(uint32_t))) {
return false;
}
}