WebAuthentication.cpp

// SPDX-License-Identifier: LGPL-3.0-or-later
// Copyright 2016-2025 Hristo Gochkov, Mathieu Carbou, Emil Muratov

#include "WebAuthentication.h"
#include <libb64/cencode.h>
#if defined(ESP32) || defined(TARGET_RP2040)
#include <MD5Builder.h>
#else
#include "md5.h"
#endif
#include "literals.h"

using namespace asyncsrv;

// Basic Auth hash = base64("username:password")

bool checkBasicAuthentication(const char *hash, const char *username, const char *password) {
  if (username == NULL || password == NULL || hash == NULL) {
    return false;
  }
  return generateBasicHash(username, password).equalsIgnoreCase(hash);
}

String generateBasicHash(const char *username, const char *password) {
  if (username == NULL || password == NULL) {
    return emptyString;
  }

  size_t toencodeLen = strlen(username) + strlen(password) + 1;

  char *toencode = new char[toencodeLen + 1];
  if (toencode == NULL) {
    return emptyString;
  }
  char *encoded = new char[base64_encode_expected_len(toencodeLen) + 1];
  if (encoded == NULL) {
    delete[] toencode;
    return emptyString;
  }
  sprintf_P(toencode, PSTR("%s:%s"), username, password);
  if (base64_encode_chars(toencode, toencodeLen, encoded) > 0) {
    String res = String(encoded);
    delete[] toencode;
    delete[] encoded;
    return res;
  }
  delete[] toencode;
  delete[] encoded;
  return emptyString;
}

static bool getMD5(uint8_t *data, uint16_t len, char *output) {  // 33 bytes or more
#if defined(ESP32) || defined(TARGET_RP2040)
  MD5Builder md5;
  md5.begin();
  md5.add(data, len);
  md5.calculate();
  md5.getChars(output);
#else
  md5_context_t _ctx;

  uint8_t *_buf = (uint8_t *)malloc(16);
  if (_buf == NULL) {
    return false;
  }
  memset(_buf, 0x00, 16);

  MD5Init(&_ctx);
  MD5Update(&_ctx, data, len);
  MD5Final(_buf, &_ctx);

  for (uint8_t i = 0; i < 16; i++) {
    sprintf_P(output + (i * 2), PSTR("%02x"), _buf[i]);
  }

  free(_buf);
#endif
  return true;
}

String genRandomMD5() {
#ifdef ESP8266
  uint32_t r = RANDOM_REG32;
#else
  uint32_t r = rand();
#endif
  char *out = (char *)malloc(33);
  if (out == NULL || !getMD5((uint8_t *)(&r), 4, out)) {
    return emptyString;
  }
  String res = String(out);
  free(out);
  return res;
}

static String stringMD5(const String &in) {
  char *out = (char *)malloc(33);
  if (out == NULL || !getMD5((uint8_t *)(in.c_str()), in.length(), out)) {
    return emptyString;
  }
  String res = String(out);
  free(out);
  return res;
}

String generateDigestHash(const char *username, const char *password, const char *realm) {
  if (username == NULL || password == NULL || realm == NULL) {
    return emptyString;
  }
  char *out = (char *)malloc(33);

  String in;
  in.reserve(strlen(username) + strlen(realm) + strlen(password) + 2);
  in.concat(username);
  in.concat(':');
  in.concat(realm);
  in.concat(':');
  in.concat(password);

  if (out == NULL || !getMD5((uint8_t *)(in.c_str()), in.length(), out)) {
    return emptyString;
  }

  in = String(out);
  free(out);
  return in;
}

bool checkDigestAuthentication(
  const char *header, const char *method, const char *username, const char *password, const char *realm, bool passwordIsHash, const char *nonce,
  const char *opaque, const char *uri
) {
  if (username == NULL || password == NULL || header == NULL || method == NULL) {
    // os_printf("AUTH FAIL: missing required fields\n");
    return false;
  }

  String myHeader(header);
  int nextBreak = myHeader.indexOf(',');
  if (nextBreak < 0) {
    // os_printf("AUTH FAIL: no variables\n");
    return false;
  }

  String myUsername;
  String myRealm;
  String myNonce;
  String myUri;
  String myResponse;
  String myQop;
  String myNc;
  String myCnonce;

  myHeader += (char)0x2c;  // ','
  myHeader += (char)0x20;  // ' '
  do {
    String avLine(myHeader.substring(0, nextBreak));
    avLine.trim();
    myHeader = myHeader.substring(nextBreak + 1);
    nextBreak = myHeader.indexOf(',');

    int eqSign = avLine.indexOf('=');
    if (eqSign < 0) {
      // os_printf("AUTH FAIL: no = sign\n");
      return false;
    }
    String varName(avLine.substring(0, eqSign));
    avLine = avLine.substring(eqSign + 1);
    if (avLine.startsWith(String('"'))) {
      avLine = avLine.substring(1, avLine.length() - 1);
    }

    if (varName.equals(T_username)) {
      if (!avLine.equals(username)) {
        // os_printf("AUTH FAIL: username\n");
        return false;
      }
      myUsername = avLine;
    } else if (varName.equals(T_realm)) {
      if (realm != NULL && !avLine.equals(realm)) {
        // os_printf("AUTH FAIL: realm\n");
        return false;
      }
      myRealm = avLine;
    } else if (varName.equals(T_nonce)) {
      if (nonce != NULL && !avLine.equals(nonce)) {
        // os_printf("AUTH FAIL: nonce\n");
        return false;
      }
      myNonce = avLine;
    } else if (varName.equals(T_opaque)) {
      if (opaque != NULL && !avLine.equals(opaque)) {
        // os_printf("AUTH FAIL: opaque\n");
        return false;
      }
    } else if (varName.equals(T_uri)) {
      if (uri != NULL && !avLine.equals(uri)) {
        // os_printf("AUTH FAIL: uri\n");
        return false;
      }
      myUri = avLine;
    } else if (varName.equals(T_response)) {
      myResponse = avLine;
    } else if (varName.equals(T_qop)) {
      myQop = avLine;
    } else if (varName.equals(T_nc)) {
      myNc = avLine;
    } else if (varName.equals(T_cnonce)) {
      myCnonce = avLine;
    }
  } while (nextBreak > 0);

  String ha1 = passwordIsHash ? password : stringMD5(myUsername + ':' + myRealm + ':' + password).c_str();
  String ha2 = stringMD5(String(method) + ':' + myUri);
  String response = ha1 + ':' + myNonce + ':' + myNc + ':' + myCnonce + ':' + myQop + ':' + ha2;

  if (myResponse.equals(stringMD5(response))) {
    // os_printf("AUTH SUCCESS\n");
    return true;
  }

  // os_printf("AUTH FAIL: password\n");
  return false;
}