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Base64.cpp
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370 lines (303 loc) · 9.25 KB
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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
#include "graphqlservice/internal/Base64.h"
#include <array>
#include <stdexcept>
namespace graphql::internal {
std::uint8_t Base64::verifyFromBase64(char ch)
{
const std::uint8_t result = fromBase64(ch);
if ((result & 0xC0) != 0)
{
throw std::logic_error { "invalid character in base64 encoded string" };
}
return result;
}
std::vector<std::uint8_t> Base64::fromBase64(std::string_view encoded)
{
std::vector<std::uint8_t> result;
if (encoded.empty())
{
return result;
}
result.reserve((encoded.size() + (encoded.size() % 4)) * 3 / 4);
// First decode all of the full unpadded segments 24 bits at a time
while (encoded.size() >= 4 && encoded[3] != padding)
{
const uint32_t segment = (static_cast<uint32_t>(verifyFromBase64(encoded[0])) << 18)
| (static_cast<uint32_t>(verifyFromBase64(encoded[1])) << 12)
| (static_cast<uint32_t>(verifyFromBase64(encoded[2])) << 6)
| static_cast<uint32_t>(verifyFromBase64(encoded[3]));
result.emplace_back(static_cast<std::uint8_t>((segment & 0xFF0000) >> 16));
result.emplace_back(static_cast<std::uint8_t>((segment & 0xFF00) >> 8));
result.emplace_back(static_cast<std::uint8_t>(segment & 0xFF));
encoded = encoded.substr(4);
}
// Get any leftover partial segment with 2 or 3 non-padding characters
if (encoded.size() > 1)
{
const bool triplet = (encoded.size() > 2 && padding != encoded[2]);
const std::uint8_t tail = (triplet ? verifyFromBase64(encoded[2]) : 0);
const uint16_t segment = (static_cast<uint16_t>(verifyFromBase64(encoded[0])) << 10)
| (static_cast<uint16_t>(verifyFromBase64(encoded[1])) << 4)
| (static_cast<uint16_t>(tail) >> 2);
if (triplet)
{
if (tail & 0x3)
{
throw std::logic_error { "invalid padding at the end of a base64 encoded string" };
}
result.emplace_back(static_cast<std::uint8_t>((segment & 0xFF00) >> 8));
result.emplace_back(static_cast<std::uint8_t>(segment & 0xFF));
encoded = encoded.substr(3);
}
else
{
if (segment & 0xFF)
{
throw std::logic_error { "invalid padding at the end of a base64 encoded string" };
}
result.emplace_back(static_cast<std::uint8_t>((segment & 0xFF00) >> 8));
encoded = encoded.substr(2);
}
}
// Make sure anything that's left is 0 - 2 characters of padding
if ((encoded.size() > 0 && padding != encoded[0])
|| (encoded.size() > 1 && padding != encoded[1]) || encoded.size() > 2)
{
throw std::logic_error { "invalid padding at the end of a base64 encoded string" };
}
return result;
}
char Base64::verifyToBase64(std::uint8_t i)
{
unsigned char result = toBase64(i);
if (result == padding)
{
throw std::logic_error { "invalid 6-bit value" };
}
return result;
}
std::string Base64::toBase64(const std::vector<std::uint8_t>& bytes)
{
std::string result;
if (bytes.empty())
{
return result;
}
size_t count = bytes.size();
const std::uint8_t* data = bytes.data();
result.reserve((count + (count % 3)) * 4 / 3);
// First encode all of the full unpadded segments 24 bits at a time
while (count >= 3)
{
const uint32_t segment = (static_cast<uint32_t>(data[0]) << 16)
| (static_cast<uint32_t>(data[1]) << 8) | static_cast<uint32_t>(data[2]);
result.append({ verifyToBase64(static_cast<std::uint8_t>((segment & 0xFC0000) >> 18)),
verifyToBase64(static_cast<std::uint8_t>((segment & 0x3F000) >> 12)),
verifyToBase64(static_cast<std::uint8_t>((segment & 0xFC0) >> 6)),
verifyToBase64(static_cast<std::uint8_t>(segment & 0x3F)) });
data += 3;
count -= 3;
}
// Get any leftover partial segment with 1 or 2 bytes
if (count > 0)
{
const bool pair = (count > 1);
const uint16_t segment =
(static_cast<uint16_t>(data[0]) << 8) | (pair ? static_cast<uint16_t>(data[1]) : 0);
const std::array<char, 4> remainder { verifyToBase64(static_cast<std::uint8_t>(
(segment & 0xFC00) >> 10)),
verifyToBase64(static_cast<std::uint8_t>((segment & 0x3F0) >> 4)),
(pair ? verifyToBase64(static_cast<std::uint8_t>((segment & 0xF) << 2)) : padding),
padding };
result.append(remainder.data(), remainder.size());
}
return result;
}
Base64::Comparison Base64::compareBase64(
const std::vector<std::uint8_t>& bytes, std::string_view maybeEncoded) noexcept
{
if (bytes.empty())
{
if (maybeEncoded.empty())
{
return Comparison::EqualTo;
}
}
else if (maybeEncoded.empty())
{
return Comparison::GreaterThan;
}
auto result = Comparison::EqualTo;
auto itr = bytes.cbegin();
const auto itrEnd = bytes.cend();
// First decode and compare all of the full unpadded segments 24 bits at a time
while (maybeEncoded.size() >= 4 && maybeEncoded[3] != padding)
{
const auto a = fromBase64(maybeEncoded[0]);
const auto b = fromBase64(maybeEncoded[1]);
const auto c = fromBase64(maybeEncoded[2]);
const auto d = fromBase64(maybeEncoded[3]);
if (((a | b | c | d) & 0xC0) != 0)
{
// Invalid Base64 characters
return Comparison::InvalidBase64;
}
if (Comparison::EqualTo == result)
{
const uint32_t segment = (static_cast<uint32_t>(a) << 18)
| (static_cast<uint32_t>(b) << 12) | (static_cast<uint32_t>(c) << 6)
| static_cast<uint32_t>(d);
const std::array decoded { static_cast<std::uint8_t>((segment & 0xFF0000) >> 16),
static_cast<std::uint8_t>((segment & 0xFF00) >> 8),
static_cast<std::uint8_t>(segment & 0xFF) };
for (auto value : decoded)
{
if (itr == itrEnd)
{
result = Comparison::LessThan;
break;
}
if (*itr != value)
{
result = *itr < value ? Comparison::LessThan : Comparison::GreaterThan;
break;
}
++itr;
}
}
maybeEncoded = maybeEncoded.substr(4);
}
// Compare any leftover partial segment with 2 or 3 non-padding characters
if (maybeEncoded.size() > 1)
{
const bool triplet = (maybeEncoded.size() > 2 && padding != maybeEncoded[2]);
const auto a = fromBase64(maybeEncoded[0]);
const auto b = fromBase64(maybeEncoded[1]);
const auto c = triplet ? fromBase64(maybeEncoded[2]) : std::uint8_t {};
if (((a | b | c) & 0xC0) != 0 || (c & 0x3) != 0)
{
// Invalid Base64 characters or padding
return Comparison::InvalidBase64;
}
const uint16_t segment = (static_cast<uint16_t>(a) << 10) | (static_cast<uint16_t>(b) << 4)
| (static_cast<uint16_t>(c) >> 2);
const std::array decoded { static_cast<std::uint8_t>((segment & 0xFF00) >> 8),
static_cast<std::uint8_t>(segment & 0xFF) };
if (triplet)
{
if (Comparison::EqualTo == result)
{
for (auto value : decoded)
{
if (itr == itrEnd)
{
result = Comparison::LessThan;
break;
}
if (*itr != value)
{
result = *itr < value ? Comparison::LessThan : Comparison::GreaterThan;
break;
}
++itr;
}
}
maybeEncoded = maybeEncoded.substr(3);
}
else
{
if (decoded[1] != 0)
{
// Invalid padding
return Comparison::InvalidBase64;
}
if (Comparison::EqualTo == result)
{
if (itr == itrEnd)
{
result = Comparison::LessThan;
}
else if (*itr != decoded[0])
{
result = *itr < decoded[0] ? Comparison::LessThan : Comparison::GreaterThan;
}
++itr;
}
maybeEncoded = maybeEncoded.substr(2);
}
}
// Make sure anything that's left is 0 - 2 characters of padding
if ((maybeEncoded.size() > 0 && padding != maybeEncoded[0])
|| (maybeEncoded.size() > 1 && padding != maybeEncoded[1]) || maybeEncoded.size() > 2)
{
return Comparison::InvalidBase64;
}
if (Comparison::EqualTo == result)
{
// We should reach the end of the byte vector
if (itr != itrEnd)
{
result = Comparison::GreaterThan;
}
}
return result;
}
bool Base64::validateBase64(std::string_view maybeEncoded) noexcept
{
if (maybeEncoded.empty())
{
return true;
}
// First decode and compare all of the full unpadded segments 24 bits at a time
while (maybeEncoded.size() >= 4 && maybeEncoded[3] != padding)
{
const auto a = fromBase64(maybeEncoded[0]);
const auto b = fromBase64(maybeEncoded[1]);
const auto c = fromBase64(maybeEncoded[2]);
const auto d = fromBase64(maybeEncoded[3]);
if (((a | b | c | d) & 0xC0) != 0)
{
// Invalid Base64 characters
return false;
}
maybeEncoded = maybeEncoded.substr(4);
}
// Compare any leftover partial segment with 2 or 3 non-padding characters
if (maybeEncoded.size() > 1)
{
const bool triplet = (maybeEncoded.size() > 2 && padding != maybeEncoded[2]);
const auto a = fromBase64(maybeEncoded[0]);
const auto b = fromBase64(maybeEncoded[1]);
const auto c = triplet ? fromBase64(maybeEncoded[2]) : std::uint8_t {};
if (((a | b | c) & 0xC0) != 0 || (c & 0x3) != 0)
{
// Invalid Base64 characters or padding
return false;
}
if (triplet)
{
maybeEncoded = maybeEncoded.substr(3);
}
else
{
const uint16_t segment = (static_cast<uint16_t>(a) << 10)
| (static_cast<uint16_t>(b) << 4) | (static_cast<uint16_t>(c) >> 2);
if ((segment & 0xFF) != 0)
{
// Invalid padding
return false;
}
maybeEncoded = maybeEncoded.substr(2);
}
}
// Make sure anything that's left is 0 - 2 characters of padding
if ((maybeEncoded.size() > 0 && padding != maybeEncoded[0])
|| (maybeEncoded.size() > 1 && padding != maybeEncoded[1]) || maybeEncoded.size() > 2)
{
return false;
}
return true;
}
} // namespace graphql::internal
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