/*
 * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdarg.h>

#include "lwip/sockets.h"
#include "esp_rom_md5.h"
#include "esp_tls_crypto.h"

#include "esp_system.h"
#include "esp_log.h"
#include "esp_check.h"

#include "http_utils.h"
#include "http_auth.h"

#define MD5_MAX_LEN (33)
#define HTTP_AUTH_BUF_LEN (1024)

static const char *TAG = "HTTP_AUTH";

/**
 * @brief      This function hash a formatted string with MD5 and format the result as ascii characters
 *
 * @param      md         The buffer will hold the ascii result
 * @param[in]  fmt        The format
 *
 * @return     Length of the result
 */
static int md5_printf(char *md, const char *fmt, ...)
{
    unsigned char *buf;
    unsigned char digest[MD5_MAX_LEN];
    int len, i;
    md5_context_t md5_ctx;
    va_list ap;
    va_start(ap, fmt);
    len = vasprintf((char **)&buf, fmt, ap);
    if (buf == NULL) {
        va_end(ap);
        return ESP_FAIL;
    }

    esp_rom_md5_init(&md5_ctx);
    esp_rom_md5_update(&md5_ctx, buf, len);
    esp_rom_md5_final(digest, &md5_ctx);

    for (i = 0; i < 16; ++i) {
        sprintf(&md[i * 2], "%02x", (unsigned int)digest[i]);
    }
    va_end(ap);

    free(buf);
    return MD5_MAX_LEN;
}

char *http_auth_digest(const char *username, const char *password, esp_http_auth_data_t *auth_data)
{
    char *ha1, *ha2 = NULL;
    char *digest = NULL;
    char *auth_str = NULL;
    char *temp_auth_str = NULL;
    esp_err_t ret = ESP_OK;

    if (username == NULL ||
        password == NULL ||
        auth_data->nonce == NULL ||
        auth_data->uri == NULL ||
        auth_data->realm == NULL) {
        return NULL;
    }

    ha1 = calloc(1, MD5_MAX_LEN);
    ESP_GOTO_ON_FALSE(ha1, ESP_FAIL, _digest_exit, TAG, "Memory exhausted");

    ha2 = calloc(1, MD5_MAX_LEN);
    ESP_GOTO_ON_FALSE(ha2, ESP_FAIL, _digest_exit, TAG, "Memory exhausted");

    digest = calloc(1, MD5_MAX_LEN);
    ESP_GOTO_ON_FALSE(digest, ESP_FAIL, _digest_exit, TAG, "Memory exhausted");

    if (md5_printf(ha1, "%s:%s:%s", username, auth_data->realm, password) <= 0) {
        goto _digest_exit;
    }

    ESP_LOGD(TAG, "%s %s %s %s\r\n", "Digest", username, auth_data->realm, password);
    if (strcasecmp(auth_data->algorithm, "md5-sess") == 0) {
        if (md5_printf(ha1, "%s:%s:%016llx", ha1, auth_data->nonce, auth_data->cnonce) <= 0) {
            goto _digest_exit;
        }
    }
    if (md5_printf(ha2, "%s:%s", auth_data->method, auth_data->uri) <= 0) {
        goto _digest_exit;
    }

    //support qop = auth
    if (auth_data->qop && strcasecmp(auth_data->qop, "auth-int") == 0) {
        if (md5_printf(ha2, "%s:%s", ha2, "entity") <= 0) {
            goto _digest_exit;
        }
    }

    if (auth_data->qop) {
        // response=MD5(HA1:nonce:nonceCount:cnonce:qop:HA2)
        if (md5_printf(digest, "%s:%s:%08x:%016llx:%s:%s", ha1, auth_data->nonce, auth_data->nc, auth_data->cnonce, auth_data->qop, ha2) <= 0) {
            goto _digest_exit;
        }
    } else {
        /* Although as per RFC-2617, "qop" directive is optional in order to maintain backward compatibality, it is recommended
           to use it if the server indicated that qop is supported. This enhancement was introduced to protect against attacks
           like chosen-plaintext attack. */
        ESP_LOGW(TAG, "\"qop\" directive not found. This may lead to attacks like chosen-plaintext attack");
        // response=MD5(HA1:nonce:HA2)
        if (md5_printf(digest, "%s:%s:%s", ha1, auth_data->nonce, ha2) <= 0) {
            goto _digest_exit;
        }
    }
    int rc = asprintf(&auth_str, "Digest username=\"%s\", realm=\"%s\", nonce=\"%s\", uri=\"%s\", algorithm=\"MD5\", "
                      "response=\"%s\"", username, auth_data->realm, auth_data->nonce, auth_data->uri, digest);
    if (rc < 0) {
        ESP_LOGE(TAG, "asprintf() returned: %d", rc);
        ret = ESP_FAIL;
        goto _digest_exit;
    }

    if (auth_data->qop) {
        rc = asprintf(&temp_auth_str, ", qop=%s, nc=%08x, cnonce=\"%016"PRIx64"\"", auth_data->qop, auth_data->nc, auth_data->cnonce);
        if (rc < 0) {
            ESP_LOGE(TAG, "asprintf() returned: %d", rc);
            ret = ESP_FAIL;
            goto _digest_exit;
        }
        auth_str = http_utils_append_string(&auth_str, temp_auth_str, strlen(temp_auth_str));
        if (!auth_str) {
            ret = ESP_FAIL;
            goto _digest_exit;
        }
        free(temp_auth_str);
        auth_data->nc ++;
    }
    if (auth_data->opaque) {
        asprintf(&temp_auth_str, "%s, opaque=\"%s\"", auth_str, auth_data->opaque);
        free(auth_str);
        auth_str = temp_auth_str;
    }
_digest_exit:
    free(ha1);
    free(ha2);
    free(digest);
    return (ret == ESP_OK) ? auth_str : NULL;
}

char *http_auth_basic(const char *username, const char *password)
{
    int out;
    char *user_info = NULL;
    char *digest = NULL;
    esp_err_t ret = ESP_OK;
    size_t n = 0;
    asprintf(&user_info, "%s:%s", username, password);
    ESP_RETURN_ON_FALSE(user_info, NULL, TAG, "Memory exhausted");
    esp_crypto_base64_encode(NULL, 0, &n, (const unsigned char *)user_info, strlen(user_info));
    digest = calloc(1, 6 + n + 1);
    ESP_GOTO_ON_FALSE(digest, ESP_FAIL, _basic_exit, TAG, "Memory exhausted");
    strcpy(digest, "Basic ");
    esp_crypto_base64_encode((unsigned char *)digest + 6, n, (size_t *)&out, (const unsigned char *)user_info, strlen(user_info));
_basic_exit:
    free(user_info);
    return (ret == ESP_OK) ? digest : NULL;
}