/*
 * Copyright (C) 1996-2017 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

#include "squid.h"

#if HAVE_GSSAPI

#include "base64.h"
#include "tools/squidclient/gssapi_support.h"

#include <iostream>

#if !defined(gss_mech_spnego)
static gss_OID_desc _gss_mech_spnego = {6, (void *) "\x2b\x06\x01\x05\x05\x02"};
gss_OID gss_mech_spnego = &_gss_mech_spnego;
#endif

#define BUFFER_SIZE 8192

/**
 * Check return valuse major_status, minor_status for error and print error description
 * in case of an error.
 *
 * \retval true in case of gssapi error
 * \retval false in case of no gssapi error
 */
bool
check_gss_err(OM_uint32 major_status, OM_uint32 minor_status, const char *function)
{
    if (GSS_ERROR(major_status)) {
        OM_uint32 maj_stat, min_stat;
        OM_uint32 msg_ctx = 0;
        gss_buffer_desc status_string;
        char buf[BUFFER_SIZE];
        size_t len;

        len = 0;
        msg_ctx = 0;
        while (!msg_ctx) {
            /* convert major status code (GSS-API error) to text */
            maj_stat = gss_display_status(&min_stat, major_status,
                                          GSS_C_GSS_CODE,
                                          GSS_C_NULL_OID,
                                          &msg_ctx, &status_string);
            if (maj_stat == GSS_S_COMPLETE) {
                snprintf(buf + len, BUFFER_SIZE-len, "%s", (char *) status_string.value);
                len += status_string.length;
                gss_release_buffer(&min_stat, &status_string);
                break;
            }
            gss_release_buffer(&min_stat, &status_string);
        }
        snprintf(buf + len, BUFFER_SIZE-len, "%s", ". ");
        len += 2;
        msg_ctx = 0;
        while (!msg_ctx) {
            /* convert minor status code (underlying routine error) to text */
            maj_stat = gss_display_status(&min_stat, minor_status,
                                          GSS_C_MECH_CODE,
                                          GSS_C_NULL_OID,
                                          &msg_ctx, &status_string);
            if (maj_stat == GSS_S_COMPLETE) {
                snprintf(buf + len, BUFFER_SIZE-len,"%s", (char *) status_string.value);
                len += status_string.length;
                gss_release_buffer(&min_stat, &status_string);
                break;
            }
            gss_release_buffer(&min_stat, &status_string);
        }
        std::cerr << "ERROR: " << function << " failed: " << buf << std::endl;
        return true;
    }
    return false;
}

/**
 * Get gssapi token for service HTTP/<server>
 * User has to initiate a kinit user@DOMAIN on commandline first for the
 * function to be successful
 *
 * \return base64 encoded token if successful,
 *         string "ERROR" if unsuccessful
 */
char *
GSSAPI_token(const char *server)
{
    OM_uint32 major_status, minor_status;
    gss_ctx_id_t gss_context = GSS_C_NO_CONTEXT;
    gss_name_t server_name = GSS_C_NO_NAME;
    gss_buffer_desc service = GSS_C_EMPTY_BUFFER;
    gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
    gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
    char *token = NULL;

    setbuf(stdout, NULL);
    setbuf(stdin, NULL);

    if (!server) {
        std::cerr << "ERROR: GSSAPI: No server name" << std::endl;
        token = new char[6];
        memcpy(token, "ERROR", 5);
        token[5] = '\0';
        return token;
    }
    service.value = xmalloc(strlen("HTTP") + strlen(server) + 2);
    snprintf((char *) service.value, strlen("HTTP") + strlen(server) + 2, "%s@%s", "HTTP", server);
    service.length = strlen((char *) service.value);

    major_status = gss_import_name(&minor_status, &service,
                                   gss_nt_service_name, &server_name);

    if (!check_gss_err(major_status, minor_status, "gss_import_name()")) {

        major_status = gss_init_sec_context(&minor_status,
                                            GSS_C_NO_CREDENTIAL,
                                            &gss_context,
                                            server_name,
                                            gss_mech_spnego,
                                            0,
                                            0,
                                            GSS_C_NO_CHANNEL_BINDINGS,
                                            &input_token,
                                            NULL,
                                            &output_token,
                                            NULL,
                                            NULL);

        if (!check_gss_err(major_status, minor_status, "gss_init_sec_context()") && output_token.length) {
            uint8_t *b64buf = new uint8_t[base64_encode_len(output_token.length)];
            struct base64_encode_ctx ctx;
            base64_encode_init(&ctx);
            size_t blen = base64_encode_update(&ctx, b64buf, output_token.length, reinterpret_cast<const uint8_t*>(output_token.value));
            blen += base64_encode_final(&ctx, b64buf+blen);
            b64buf[blen] = '\0';

            token = reinterpret_cast<char*>(b64buf);
        }
    }

    if (!output_token.length) {
        token = new char[6];
        memcpy(token, "ERROR", 5);
        token[5] = '\0';
    }

    gss_delete_sec_context(&minor_status, &gss_context, NULL);
    gss_release_buffer(&minor_status, &service);
    gss_release_buffer(&minor_status, &input_token);
    gss_release_buffer(&minor_status, &output_token);
    gss_release_name(&minor_status, &server_name);

    return token;
}

#endif /* HAVE_GSSAPI */

