cash_addr.c

/* Copyright (c) 2017 Jochen Hoenicke
 * based on code Copyright (c) 2017 Peter Wuille
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include <stdlib.h>
#include <stdint.h>
#include <string.h>

#include "cash_addr.h"

#define MAX_CASHADDR_SIZE 129
#define MAX_BASE32_SIZE 104
#define MAX_DATA_SIZE 65
#define MAX_HRP_SIZE 20
#define CHECKSUM_SIZE 8

uint64_t cashaddr_polymod_step(uint64_t pre) {
    uint8_t b = pre >> 35;
    return ((pre & 0x7FFFFFFFFULL) << 5) ^
        (-((b >> 0) & 1) & 0x98f2bc8e61ULL) ^
        (-((b >> 1) & 1) & 0x79b76d99e2ULL) ^
        (-((b >> 2) & 1) & 0xf33e5fb3c4ULL) ^
        (-((b >> 3) & 1) & 0xae2eabe2a8ULL) ^
        (-((b >> 4) & 1) & 0x1e4f43e470ULL);
}

static const char* charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";

static const int8_t charset_rev[128] = {
    -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,
    15, -1, 10, 17, 21, 20, 26, 30,  7,  5, -1, -1, -1, -1, -1, -1,
    -1, 29, -1, 24, 13, 25,  9,  8, 23, -1, 18, 22, 31, 27, 19, -1,
     1,  0,  3, 16, 11, 28, 12, 14,  6,  4,  2, -1, -1, -1, -1, -1,
    -1, 29, -1, 24, 13, 25,  9,  8, 23, -1, 18, 22, 31, 27, 19, -1,
     1,  0,  3, 16, 11, 28, 12, 14,  6,  4,  2, -1, -1, -1, -1, -1
};

int cash_encode(char *output, const char *hrp, const uint8_t *data, size_t data_len) {
    uint64_t chk = 1;
    size_t i = 0;
    while (hrp[i] != 0) {
        int ch = hrp[i];
        if (ch < 33 || ch > 126) {
            return 0;
        }
        *(output++) = ch;
        chk = cashaddr_polymod_step(chk) ^ (ch & 0x1f);
        ++i;
    }
    if (i + 1 + data_len + CHECKSUM_SIZE > MAX_CASHADDR_SIZE) {
        return 0;
    }
    chk = cashaddr_polymod_step(chk);
    *(output++) = ':';
    for (i = 0; i < data_len; ++i) {
        if (*data >> 5) return 0;
        chk = cashaddr_polymod_step(chk) ^ (*data);
        *(output++) = charset[*(data++)];
    }
    for (i = 0; i < CHECKSUM_SIZE; ++i) {
        chk = cashaddr_polymod_step(chk);
    }
    chk ^= 1;
    for (i = 0; i < CHECKSUM_SIZE; ++i) {
        *(output++) = charset[(chk >> ((CHECKSUM_SIZE - 1 - i) * 5)) & 0x1f];
    }
    *output = 0;
    return 1;
}

int cash_decode(char* hrp, uint8_t *data, size_t *data_len, const char *input) {
    uint64_t chk = 1;
    size_t i;
    size_t input_len = strlen(input);
    size_t hrp_len;
    int have_lower = 0, have_upper = 0;
    if (input_len < CHECKSUM_SIZE || input_len > MAX_CASHADDR_SIZE) {
        return 0;
    }
    *data_len = 0;
    while (*data_len < input_len && input[(input_len - 1) - *data_len] != ':') {
        ++(*data_len);
    }
    hrp_len = input_len - (1 + *data_len);
    if (hrp_len < 1 || hrp_len > MAX_HRP_SIZE ||
        *data_len < CHECKSUM_SIZE || *data_len > CHECKSUM_SIZE + MAX_BASE32_SIZE) {
        return 0;
    }
    // subtract checksum
    *(data_len) -= CHECKSUM_SIZE;
    for (i = 0; i < hrp_len; ++i) {
        int ch = input[i];
        if (ch < 33 || ch > 126) {
            return 0;
        }
        if (ch >= 'a' && ch <= 'z') {
            have_lower = 1;
        } else if (ch >= 'A' && ch <= 'Z') {
            have_upper = 1;
            ch = (ch - 'A') + 'a';
        }
        hrp[i] = ch;
        chk = cashaddr_polymod_step(chk) ^ (ch & 0x1f);
    }
    hrp[i] = 0;
    chk = cashaddr_polymod_step(chk);
    ++i;
    while (i < input_len) {
        int v = (input[i] & 0x80) ? -1 : charset_rev[(int)input[i]];
        if (input[i] >= 'a' && input[i] <= 'z') have_lower = 1;
        if (input[i] >= 'A' && input[i] <= 'Z') have_upper = 1;
        if (v == -1) {
            return 0;
        }
        chk = cashaddr_polymod_step(chk) ^ v;
        if (i + 6 < input_len) {
            data[i - (1 + hrp_len)] = v;
        }
        ++i;
    }
    if (have_lower && have_upper) {
        return 0;
    }
    return chk == 1;
}

static int convert_bits(uint8_t* out, size_t* outlen, int outbits, const uint8_t* in, size_t inlen, int inbits, int pad) {
    uint32_t val = 0;
    int bits = 0;
    uint32_t maxv = (((uint32_t)1) << outbits) - 1;
    while (inlen--) {
        val = (val << inbits) | *(in++);
        bits += inbits;
        while (bits >= outbits) {
            bits -= outbits;
            out[(*outlen)++] = (val >> bits) & maxv;
        }
    }
    if (pad) {
        if (bits) {
            out[(*outlen)++] = (val << (outbits - bits)) & maxv;
        }
    } else if (((val << (outbits - bits)) & maxv) || bits >= inbits) {
        return 0;
    }
    return 1;
}

int cash_addr_encode(char *output, const char *hrp, const uint8_t *data, size_t data_len) {
    uint8_t base32[MAX_BASE32_SIZE];
    size_t base32len = 0;
    if (data_len < 2 || data_len > MAX_DATA_SIZE) return 0;
    convert_bits(base32, &base32len, 5, data, data_len, 8, 1);
    return cash_encode(output, hrp, base32, base32len);
}

int cash_addr_decode(uint8_t* witdata, size_t* witdata_len, const char* hrp, const char* addr) {
    uint8_t data[MAX_BASE32_SIZE];
    char hrp_actual[MAX_HRP_SIZE+1];
    size_t data_len;
    if (!cash_decode(hrp_actual, data, &data_len, addr)) return 0;
    if (data_len == 0 || data_len > MAX_BASE32_SIZE) return 0;
    if (strncmp(hrp, hrp_actual, MAX_HRP_SIZE + 1) != 0) return 0;
    *witdata_len = 0;
    if (!convert_bits(witdata, witdata_len, 8, data, data_len, 5, 0)) return 0;
    if (*witdata_len < 2 || *witdata_len > MAX_DATA_SIZE) return 0;
    return 1;
}