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wscutil: Add wsc_pin_is_checksum_valid

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This commit is contained in:
Denis Kenzior 2017-02-13 20:27:24 -06:00
parent 5a8d573ae4
commit 94c49a4563
2 changed files with 29 additions and 0 deletions
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28
src/wscutil.c
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@ -2531,3 +2531,31 @@ bool wsc_pin_is_valid(const char *pin)
return true; return true;
} }
/* Takes the first 7 characters of a PIN as input and computes a check digit */
static char compute_check_digit(const char *pin)
{
unsigned int accum = 0;
unsigned int digit;
accum += 3 * ((pin[0] - '0') % 10);
accum += 1 * ((pin[1] - '0') % 10);
accum += 3 * ((pin[2] - '0') % 10);
accum += 1 * ((pin[3] - '0') % 10);
accum += 3 * ((pin[4] - '0') % 10);
accum += 1 * ((pin[5] - '0') % 10);
accum += 3 * ((pin[6] - '0') % 10);
digit = (10 - (accum % 10)) % 10;
return '0' + digit;
}
/*
* Validates the checksum digit and returns true if valid. Assumes that the
* input is an 8-byte PIN already validated by wsc_pin_is_valid()
*/
bool wsc_pin_is_checksum_valid(const char *pin)
{
char digit = compute_check_digit(pin);
return pin[7] == digit;
}

1
src/wscutil.h
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@ -639,3 +639,4 @@ struct wsc_session_key {
bool wsc_kdf(const void *kdk, void *output, size_t size); bool wsc_kdf(const void *kdk, void *output, size_t size);
bool wsc_pin_is_valid(const char *pin); bool wsc_pin_is_valid(const char *pin);
bool wsc_pin_is_checksum_valid(const char *pin);