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/*
* (C) 2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/base58.h>
#include <botan/exceptn.h>
#include <botan/bigint.h>
#include <botan/divide.h>
#include <botan/loadstor.h>
#include <botan/hash.h>
namespace Botan {
namespace {
uint32_t sha256_d_checksum(const uint8_t input[], size_t input_length)
{
std::unique_ptr<HashFunction> sha256 = HashFunction::create_or_throw("SHA-256");
std::vector<uint8_t> checksum(32);
sha256->update(input, input_length);
sha256->final(checksum);
sha256->update(checksum);
sha256->final(checksum);
checksum.resize(4);
uint32_t c = load_be<uint32_t>(checksum.data(), 0);
return c;
}
class Character_Table
{
public:
// This must be a literal constant
Character_Table(const char* alphabet) :
m_alphabet(alphabet)
{
const size_t alpha_len = std::strlen(alphabet);
// 128 or up would flow into 0x80 invalid bit
if(alpha_len == 0 || alpha_len >= 128)
throw Invalid_Argument("Bad Character_Table string");
m_alphabet_len = static_cast<uint8_t>(alpha_len);
set_mem(m_tab, 256, 0x80);
for(size_t i = 0; m_alphabet[i]; ++i)
{
const uint8_t b = static_cast<uint8_t>(m_alphabet[i]);
BOTAN_ASSERT(m_tab[b] == 0x80, "No duplicate chars");
m_tab[b] = static_cast<uint8_t>(i);
}
}
uint8_t radix() const { return m_alphabet_len; }
char operator[](size_t i) const
{
BOTAN_ASSERT(i < m_alphabet_len, "Character in range");
return m_alphabet[i];
}
uint8_t code_for(char c) const
{
return m_tab[static_cast<uint8_t>(c)];
}
private:
const char* m_alphabet;
uint8_t m_alphabet_len;
uint8_t m_tab[256];
};
static const Character_Table& BASE58_ALPHA()
{
static const Character_Table base58_alpha("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz");
return base58_alpha;
}
std::string base58_encode(BigInt v, size_t leading_zeros)
{
const auto base58 = BASE58_ALPHA();
std::string result;
BigInt q;
uint8_t r;
while(v.is_nonzero())
{
ct_divide_u8(v, base58.radix(), q, r);
result.push_back(base58[r]);
v.swap(q);
}
for(size_t i = 0; i != leading_zeros; ++i)
result.push_back(base58[0]);
return std::string(result.rbegin(), result.rend());
}
template<typename T, typename Z>
size_t count_leading_zeros(const T input[], size_t input_length, Z zero)
{
size_t leading_zeros = 0;
while(leading_zeros < input_length && input[leading_zeros] == zero)
leading_zeros += 1;
return leading_zeros;
}
}
std::string base58_encode(const uint8_t input[], size_t input_length)
{
BigInt v(input, input_length);
return base58_encode(v, count_leading_zeros(input, input_length, 0));
}
std::string base58_check_encode(const uint8_t input[], size_t input_length)
{
BigInt v(input, input_length);
v <<= 32;
v += sha256_d_checksum(input, input_length);
return base58_encode(v, count_leading_zeros(input, input_length, 0));
}
std::vector<uint8_t> base58_decode(const char input[], size_t input_length)
{
const auto base58 = BASE58_ALPHA();
const size_t leading_zeros = count_leading_zeros(input, input_length, base58[0]);
BigInt v;
for(size_t i = leading_zeros; i != input_length; ++i)
{
size_t idx = base58.code_for(input[i]);
if(idx == 0x80)
throw Decoding_Error("Invalid base58");
v *= base58.radix();
v += idx;
}
std::vector<uint8_t> output(v.bytes() + leading_zeros);
v.binary_encode(output.data() + leading_zeros);
return output;
}
std::vector<uint8_t> base58_check_decode(const char input[], size_t input_length)
{
std::vector<uint8_t> dec = base58_decode(input, input_length);
if(dec.size() < 4)
throw Decoding_Error("Invalid base58 too short for checksum");
const uint32_t computed_checksum = sha256_d_checksum(dec.data(), dec.size() - 4);
const uint32_t checksum = load_be<uint32_t>(&dec[dec.size()-4], 0);
if(checksum != computed_checksum)
throw Decoding_Error("Invalid base58 checksum");
dec.resize(dec.size() - 4);
return dec;
}
}
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