std::string count_it(std::string a, std::string b, count_fn f)
{
std::string res;// res.reserve(1024);
if (f!=mul)
prepend_zeros(a,b);
DLOGF("ENTER: a=%s b=%s\n",a.c_str(),b.c_str());
res = f(a,b);
remove_prep_zeros(res);
return res;
}
std::string sub(std::string a,std::string b)
{
std::string res;// res.reserve(1024);
prepend_zeros(a,b);
DLOGF("ENTER: a=%s b=%s\n",a.c_str(),b.c_str());
int borrowed=0;
for (int i=a.size()-1;i>=0;--i) {
int c=a[i]&0xf;
int d=b[i]&0xf;
int e=c-d-borrowed;
if (e<0) {
borrowed=1;
e+=10;
} else
borrowed=0;
res+=e+0x30;
}
reverse(res);
return res;
}
std::string add(std::string a,std::string b)
{
std::string res;// res.reserve(1024);
prepend_zeros(a,b);
DLOGF("ENTER: a=%s b=%s\n",a.c_str(),b.c_str());
int rest=0;
int i=0;
DLOG("Counting sum \n");
for (i=a.size()-1;i>=0;--i) {
int c=a[i]&0xf;
int d=b[i]&0xf;
res+=(((c+d+rest)%10) + 0x30);
DLOGF("i=%d c=%d d=%d rest=%d sum=%d res=%s\n",i,c,d,rest,c+d+rest,res.c_str());
if (c+d+rest>9) rest=1;else rest=0;
}
if (rest)
res+='1';
reverse(res);
return res;
}
int
validateOTP(char * secret_hex, uint8_t * data, char * HOTP_string)
{
int i, j;
uint8_t ipad[65]; /* inner padding - key XORd with ipad */
uint8_t opad[65]; /* outer padding - key XORd with opad */
int s_len = strlen(secret_hex);
int k_len = s_len/2;
uint8_t key[k_len];
SHA1_INFO ctx;
// Convert string of 20 hex characters to an array of
// bytes (two hex chars correspond to 1 uint8_t value)
for (i = 0, j = 0; i < s_len; i+=2, j++)
key[j] = hexstr_to_hex(secret_hex[i]) * 16 + hexstr_to_hex(secret_hex[i + 1]);
/* The HMAC_SHA1 transform looks like: */
/* SHA1(K XOR opad, SHA1(K XOR ipad, text)) */
/* where K is an n byte key */
/* ipad is the byte 0x36 repeated 64 times */
/* opad is the byte 0x5c repeated 64 times */
/* and text is the data being protected */
memset(ipad, 0, sizeof(ipad));
memset(opad, 0, sizeof(opad));
memcpy(ipad, key, k_len);
memcpy(opad, key, k_len);
/* XOR key with ipad and opad values */
for (i = 0; i < 64; i++) {
ipad[i] ^= 0x36;
opad[i] ^= 0x5c;
}
// Compute inner hash
uint8_t ihmac[SHA1_DIGEST_LENGTH];
sha1_init(&ctx);
sha1_update(&ctx, ipad, 64);
sha1_update(&ctx, data, sizeof(data));
sha1_final(&ctx, ihmac);
// Compute inner hash
uint8_t hmac[SHA1_DIGEST_LENGTH];
sha1_init(&ctx);
sha1_update(&ctx, opad, 64);
sha1_update(&ctx, ihmac, SHA1_DIGEST_LENGTH);
sha1_final(&ctx, hmac);
// Extract 4B dynamic binary code from HMAC
int offset = hmac[SHA1_DIGEST_LENGTH - 1] & 0x0f;
long binary = ((hmac[offset] & 0x7f) << 24)
| ((hmac[offset + 1] & 0xff) << 16)
| ((hmac[offset + 2] & 0xff) << 8)
| ( hmac[offset + 3] & 0xff);
long otp = binary % 1000000;
char otp_str[7];
sprintf(otp_str, "%ld", otp);
while(strlen(otp_str) < 6)
prepend_zeros(otp_str);
if(strcmp(HOTP_string, otp_str)==0)
return 1;
else return 0;
}
