Topic: C or C++ code for validating Bitcoin addresses (Read 2273 times)

/* Based on libbase58, see https://github.com/luke-jr/libbase58 for reference.*/
/* Attempts to convert the binary input to a Base58 format and returns true   */
/* on success.                                                                */
static bool generate_bitcoin_address(const unsigned char *payload, char type, char *b58, size_t *b58sz) {
    unsigned char address[25];

    address[0] = ( type == '1' ? 0 :
                   type == '3' ? 5 : 111);
    memcpy(address+1, payload, 20);

    unsigned char d1[SHA256_DIGEST_LENGTH], d2[SHA256_DIGEST_LENGTH];
    SHA256(SHA256(address, 21, d1), SHA256_DIGEST_LENGTH, d2);
    memcpy(address+21, d2, 4);

    {
        static const char b58digits_ordered[] = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
        const uint8_t *bin = (const uint8_t *) address;
        int carry;
        ssize_t i, j, high, zcount = 0;
        size_t size;
        size_t uzcount = 0;

        while (uzcount < 25 && !bin[uzcount]) ++uzcount;
        zcount = uzcount;
        size =        (25 - zcount) * 138 / 100 + 1;
        uint8_t buf[ ((25 -      0) * 138 / 100 + 1) ];
        memset(buf, 0, size);
        for (i = zcount, high = size - 1; i < 25; ++i, high = j) {
            for (carry = bin[i], j = size - 1; (j > high) || carry; --j) {
                carry += 256 * buf[j];
                buf[j] = carry % 58;
                carry /= 58;
            }
        }

        for (j = 0; j < (ssize_t) size && !buf[j]; ++j);

        if (*b58sz <= zcount + size - j) {
            *b58sz = zcount + size - j + 1;
            return false;
        }

        if (zcount) memset(b58, '1', zcount);
        for (i = zcount; j < (ssize_t) size; ++i, ++j) b58[i] = b58digits_ordered[buf[j]];
        b58[i] = '\0';
        *b58sz = i + 1;
    }
    return true;
}

#include
#include
#include
#include
#include
#include

/* Based on libbase58, see https://github.com/luke-jr/libbase58 for reference.*/
/* Returns the version of a valid Bitcoin address or a negative value if the  */
/* address is invalid.                                                        */
int validate_bitcoin_address(const char *address) {
    static const int8_t b58digits_map[] = {
        -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
        -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
        -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
        -1, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,
        -1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
        22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
        -1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
        47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,
    };

    unsigned char addrbin[25];
    size_t addrbinsz = sizeof(addrbin);

    void *bin = (void *) addrbin;
    size_t *binszp = &addrbinsz;
    const char *b58 = address;
    size_t b58sz = strlen(address);

    {
        const unsigned char *b58u = (void *) b58;
        unsigned char *binu = bin;
        uint32_t outi[(25 + 3) / 4];
        size_t outisz=(25 + 3) / 4;
        uint64_t t;
        uint32_t c;
        size_t i, j;
        uint8_t bytesleft = 25 % 4;
        uint32_t zeromask = bytesleft ? (0xffffffff << (bytesleft * 8)) : 0;
        unsigned zerocount = 0;

        if (!b58sz) b58sz = strlen(b58);
        memset(outi, 0, sizeof(outi));

        /* Leading zeros, just count */
        for (i = 0; i < b58sz && b58u[i] == '1'; ++i) ++zerocount;
        for ( ; i < b58sz; ++i) {
            if (b58u[i] & 0x80) return -1; /* High-bit set on invalid digit */
    if (b58digits_map[b58u[i]] == -1) return -2; /* Invalid base58 digit */
           
            c = (unsigned)b58digits_map[b58u[i]];
            for (j = outisz; j--; ) {
                t = ((uint64_t)outi[j]) * 58 + c;
                c = (t & 0x3f00000000) >> 32;
                outi[j] = t & 0xffffffff;
            }

            if (c) return -3; /* Output number too big (carry to the next int32) */
            if (outi[0] & zeromask) return -4; /* Output number too big (last int32 filled too far) */
        }

        j = 0;
        switch (bytesleft) {
            case 3: *(binu++) = (outi[0] &   0xff0000) >> 16;
    case 2: *(binu++) = (outi[0] &     0xff00) >>  8;
    case 1: *(binu++) = (outi[0] &       0xff);  ++j;
    default: break;
        }

        for (; j < outisz; ++j) {
            *(binu++) = (outi[j] >> 0x18) & 0xff;
            *(binu++) = (outi[j] >> 0x10) & 0xff;
            *(binu++) = (outi[j] >>    8) & 0xff;
            *(binu++) = (outi[j] >>    0) & 0xff;
        }

        binu = bin; /* Count canonical base58 byte count */
        for (i = 0; i < 25; ++i) {
            if (binu[i]) break;
            --*binszp;
        }
        *binszp += zerocount;
    }

    if (addrbinsz != 25) return -5;
    if (addrbin[0] != 0 && addrbin[0] != 5) return -6;

    {
        unsigned char d1[SHA256_DIGEST_LENGTH], d2[SHA256_DIGEST_LENGTH];
        SHA256(SHA256(addrbin, 21, d1), SHA256_DIGEST_LENGTH, d2);
        if (memcmp(addrbin + 21, d2, 4)) return -7;
    }

    return addrbin[0];
}

int main( int argc, char * argv [] ) {
    int i;

    for (i = 1; i < argc; ++i ) {
        bool valid = (validate_bitcoin_address(argv[i]) >= 0);
        printf( "%s is %s\n", argv[i], valid ? "VALID." : "INVALID!");
    }

    return 0;
}

SHA256(SHA256(000000000000000000000000000000000000000000)) =
94a00911c4da27f9271727ffa7a14d8d5588fc0fff9964340ec4065f387e622b

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1

SHA256(SHA256(000000000000000000000000000000000000000001)) =
9d35b5b9d5befcf2d6b89994f7f64279b0645d5d4a5f1a6fa2dcc615bbed04ef

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1