roro9stack/lib/debug/src/debug_auth.cpp

#include "debug_auth.h"

#include <cstring>

#include "sha256.h"

namespace roro::debug {

namespace {
const char kAlphabet[] = "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
}

std::string makeToken(const uint8_t random[kTokenRandom]) {
    std::string token;
    uint32_t bits = 0;
    int have = 0;
    size_t next = 0;
    while (token.size() < kTokenChars) {
        if (have < 5) {
            bits = (bits << 8) | random[next++];
            have += 8;
        }
        token += kAlphabet[(bits >> (have - 5)) & 31];
        have -= 5;
    }
    return token;
}

std::string tidyToken(const std::string& typed) {
    std::string out;
    for (char c : typed) {
        if (c == '-' || c == ' ' || c == '\t' || c == '\r' || c == '\n') continue;
        if (c >= 'a' && c <= 'z') c = static_cast<char>(c - 'a' + 'A');
        // Crockford's rule for the letters his alphabet leaves out: read as the digit they look like.
        if (c == 'O') c = '0';
        if (c == 'I' || c == 'L') c = '1';
        out += c;
    }
    return out;
}

bool validToken(const std::string& tidied) {
    if (tidied.size() < kMinTokenChars || tidied.size() > kMaxTokenChars) return false;
    for (char c : tidied)
        if (c <= ' ' || c > '~' || c == '-' || (c >= 'a' && c <= 'z') || c == 'O' || c == 'I' || c == 'L') return false;
    return true;
}

std::string groupToken(const std::string& token) {
    std::string out;
    for (size_t i = 0; i < token.size(); i++) {
        if (i && i % 4 == 0) out += '-';
        out += token[i];
    }
    return out;
}

void hmacSha256(const uint8_t* key, size_t keyLen, const uint8_t* message, size_t messageLen, uint8_t out[32]) {
    uint8_t block[64] = {};
    if (keyLen > sizeof block) Sha256::hash(key, keyLen, block);  // a long key is hashed first
    else memcpy(block, key, keyLen);

    uint8_t pad[64];
    for (size_t i = 0; i < sizeof pad; i++) pad[i] = block[i] ^ 0x36;
    uint8_t inner[32];
    Sha256 in;
    in.update(pad, sizeof pad);
    in.update(message, messageLen);
    in.finish(inner);

    for (size_t i = 0; i < sizeof pad; i++) pad[i] = block[i] ^ 0x5c;
    Sha256 outer;
    outer.update(pad, sizeof pad);
    outer.update(inner, sizeof inner);
    outer.finish(out);
}

std::string toHex(const uint8_t* data, size_t len) {
    static const char digits[] = "0123456789abcdef";
    std::string out;
    out.reserve(len * 2);
    for (size_t i = 0; i < len; i++) {
        out += digits[data[i] >> 4];
        out += digits[data[i] & 15];
    }
    return out;
}

std::string answerFor(const std::string& token, const uint8_t nonce[kNonceBytes]) {
    uint8_t mac[32];
    hmacSha256(reinterpret_cast<const uint8_t*>(token.data()), token.size(), nonce, kNonceBytes, mac);
    return toHex(mac, sizeof mac);
}

bool sameText(const std::string& a, const std::string& b) {
    uint8_t diff = a.size() != b.size();
    for (size_t i = 0; i < b.size(); i++) diff |= static_cast<uint8_t>((i < a.size() ? a[i] : 0) ^ b[i]);
    return diff == 0;
}

bool AuthGate::locked(uint32_t nowMs) {
    if (locked_ && nowMs - lockedAtMs_ >= kLockMs) {  // unsigned: right across the 49-day wrap too
        locked_ = false;
        failures_ = 0;
    }
    return locked_;
}

bool AuthGate::failed(uint32_t nowMs) {
    if (locked(nowMs)) return false;
    if (++failures_ < kMaxFailures) return false;
    locked_ = true;
    lockedAtMs_ = nowMs;
    return true;
}

}  // namespace roro::debug