/***************************************************************************
 * proxy_http.c -- HTTP Connect proxying.                                  *
 *                                                                         *
 ***********************IMPORTANT NSOCK LICENSE TERMS***********************
 *                                                                         *
 * The nsock parallel socket event library is (C) 1999-2015 Insecure.Com   *
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 *                                                                         *
 ***************************************************************************/

/* $Id $ */

#define _GNU_SOURCE
#include <stdio.h>

#include "http.h"
#include "nsock.h"
#include "nbase.h"
#include "nsock_internal.h"
#include "nsock_log.h"
#include <string.h>

#ifdef HAVE_OPENSSL
#include <openssl/md5.h>
#include <openssl/rand.h>
#endif

#define DEFAULT_PROXY_PORT_HTTP 8080


extern struct timeval nsock_tod;
extern const struct proxy_spec ProxySpecHttp;

static long check_http_status_code(const char *http) {
  char *tail;
  long res;
  char *start_code = strchr(http, ' ');
  if (start_code == NULL)
    return -1;
  start_code++; /* Skip the space after "HTTP/x.y" */
  res = parse_long(start_code, &tail);
  if (tail == start_code)
    return -1;
  return res;
}

static int proxy_http_node_new(struct proxy_node **node, const struct uri *uri) {
  int rc;
  struct proxy_node *proxy;

  proxy = (struct proxy_node *)safe_zalloc(sizeof(struct proxy_node));
  proxy->spec = &ProxySpecHttp;

  rc = proxy_resolve(uri->host, (struct sockaddr *)&proxy->ss, &proxy->sslen);
  if (rc < 0) {
    free(proxy);
    *node = NULL;
    return -1;
  }

  if (uri->port == -1)
    proxy->port = DEFAULT_PROXY_PORT_HTTP;
  else
    proxy->port = (unsigned short)uri->port;

  if (uri->user) {
    proxy->user = strdup(uri->user);
    if (!proxy->user)
      fatal("Out of Memory!");
  }
  if (uri->pass) {
    proxy->pass = strdup(uri->pass);
    if (!proxy->pass)
      fatal("Out of Memory!");
  }
  rc = asprintf(&proxy->nodestr, "http://%s:%d", uri->host, proxy->port);
  if (rc < 0) {
    /* asprintf() failed for some reason but this is not a disaster (yet).
     * Set nodestr to NULL and try to keep on going. */
    proxy->nodestr = NULL;
  }

  *node = proxy;

  return 1;
}

static void proxy_http_node_delete(struct proxy_node *node) {
  if (!node)
    return;

  free(node->user);
  free(node->pass);
  free(node->nodestr);

  free(node);
}

static int handle_state_initial(struct npool *nsp, struct nevent *nse, void *udata) {
  struct proxy_chain_context *px_ctx = nse->iod->px_ctx;
  struct sockaddr_storage *ss;
  size_t sslen;
  unsigned short port;
  struct proxy_node *next;
  int timeout;

  next = proxy_ctx_node_next(px_ctx);
  if (next) {
    ss    = &next->ss;
    sslen = next->sslen;
    port  = next->port;
  } else {
    ss    = &px_ctx->target_ss;
    sslen = px_ctx->target_sslen;
    port  = px_ctx->target_port;
  }

  timeout = TIMEVAL_MSEC_SUBTRACT(nse->timeout, nsock_tod);

  nsock_printf(nsp, (nsock_iod)nse->iod, nsock_proxy_ev_dispatch,
               timeout, udata, "CONNECT %s:%d HTTP/1.1\r\n\r\n",
               inet_ntop_ez(ss, sslen), (int)port);

  px_ctx->px_state = PROXY_STATE_HTTP_TCP_CONNECTED;
  nsock_readlines(nsp, (nsock_iod)nse->iod, nsock_proxy_ev_dispatch,
                  timeout, udata, 1);
  return 0;
}

static int handle_state_unauthenticated_basic(struct npool *nsp, struct nevent *nse, void *udata) {
  struct proxy_chain_context *px_ctx = nse->iod->px_ctx;
  struct sockaddr_storage *ss;
  size_t sslen;
  unsigned short port;
  struct proxy_node *next;
  char *auth_str;
  int rc = 1;
  int timeout;

  next = proxy_ctx_node_next(px_ctx);
  if (next) {
    ss    = &next->ss;
    sslen = next->sslen;
    port  = next->port;
  } else {
    ss    = &px_ctx->target_ss;
    sslen = px_ctx->target_sslen;
    port  = px_ctx->target_port;
  }

  timeout = TIMEVAL_MSEC_SUBTRACT(nse->timeout, nsock_tod);
  if (px_ctx->px_current->user && px_ctx->px_current->pass) {
    rc = asprintf(&auth_str, "%s:%s", px_ctx->px_current->user,
                  px_ctx->px_current->pass);
  } else if (px_ctx->px_current->user) {
    auth_str = strdup(px_ctx->px_current->user);
  } else {
    auth_str = "";
  }

  if (!auth_str || rc <= 0)
    return 1;

  auth_str = b64enc((unsigned char *) auth_str, strlen(auth_str));
  nsock_printf(nsp, (nsock_iod)nse->iod, nsock_proxy_ev_dispatch, timeout,
               udata, "CONNECT %s:%d HTTP/1.1\r\nProxy-Authorization : Basic %s\r\n\r\n",
               inet_ntop_ez(ss, sslen), (int)port, auth_str);

  px_ctx->px_state = PROXY_STATE_AUTHENTICATION_ATTEMPTED;
  nsock_readlines(nsp, (nsock_iod)nse->iod, nsock_proxy_ev_dispatch,
                  timeout, udata, 1);
  return 0;
}

static int handle_state_unauthenticated_digest(struct npool *nsp, struct nevent *nse,
                                               void *udata, const char *res) {
  struct proxy_chain_context *px_ctx = nse->iod->px_ctx;
  struct sockaddr_storage *ss;
  size_t sslen;
  unsigned short port;
  struct proxy_node *next;
  char *request;
  struct http_header *h;
  struct http_challenge challenge;

  int n = 0;

  int timeout;

  /* This function should never be called if HAVE_OPENSSL is not defined */
  #ifndef HAVE_OPENSSL
  nsock_log_debug("Digest authentication attempted without OpenSSL on proxy %s",
                  px_ctx->px_current->nodestr);
  return -1;
  #endif

  next = proxy_ctx_node_next(px_ctx);
  if (next) {
    ss    = &next->ss;
    sslen = next->sslen;
    port  = next->port;
  } else {
    ss    = &px_ctx->target_ss;
    sslen = px_ctx->target_sslen;
    port  = px_ctx->target_port;
  }

  timeout = TIMEVAL_MSEC_SUBTRACT(nse->timeout, nsock_tod);

  if (!res) {
    nsock_log_debug("Digest authentication attempted without challenge for proxy %s",
                    px_ctx->px_current->nodestr);
    return -1;
  }

  if (http_parse_header(&h, res) != 0) {
   nsock_log_debug("Error parsing digest response header for proxy %s",
                   px_ctx->px_current->nodestr);
   return -1;
  }

  if (http_header_get_proxy_challenge(h, &challenge) == NULL) {
    nsock_log_debug("Error getting Proxy-Authenticate Challenge for proxy %s",
                    px_ctx->px_current->nodestr);
    return -1;
  }

  request = http_digest_proxy_authorization(&challenge, px_ctx->px_current->user,
                                            px_ctx->px_current->pass, "CONNECT",
                                            inet_ntop_ez(ss, sslen));

  nsock_printf(nsp, (nsock_iod)nse->iod, nsock_proxy_ev_dispatch, timeout,
               udata, "%s", request);

  return 0;
}

static int handle_state_authentication_attempted(struct npool *nsp, struct nevent *nse,
                                                 void *udata) {
  struct proxy_chain_context *px_ctx = nse->iod->px_ctx;
  char *res;
  int reslen;

  res = nse_readbuf(nse, &reslen);
  if (reslen >= 15 && check_http_status_code(res) == 407) {
    nsock_log_debug("Authentication failed for proxy %s", px_ctx->px_current->nodestr);
    return -EINVAL;
  } else if (!((reslen >= 15) && strstr(res, "200 OK"))) {
    nsock_log_debug("Connection refused from proxy %s", px_ctx->px_current->nodestr);
    return -EINVAL;
  } else {
    if (proxy_ctx_node_next(px_ctx) == NULL) {
      px_ctx->px_state = PROXY_STATE_HTTP_TUNNEL_ESTABLISHED;
      forward_event(nsp, nse, udata);
    } else {
      px_ctx->px_current = proxy_ctx_node_next(px_ctx);
      px_ctx->px_state = PROXY_STATE_INITIAL;
      nsock_proxy_ev_dispatch(nsp, nse, udata);
    }
  }
  return 0;
}

static int handle_state_tcp_connected(struct npool *nsp, struct nevent *nse, void *udata) {
  struct proxy_chain_context *px_ctx = nse->iod->px_ctx;
  char *res;
  int reslen;

  res = nse_readbuf(nse, &reslen);

  if (reslen >= 15 && check_http_status_code(res) == 407) {
    #ifdef HAVE_OPENSSL
    if (strstr(res, "\r\nProxy-Authenticate: Digest ")) {
      px_ctx->px_state = PROXY_STATE_UNAUTHENTICATED_DIGEST;
      handle_state_unauthenticated_digest(nsp, nse, udata, res);
      return 0;
    }
    #endif
    px_ctx->px_state = PROXY_STATE_UNAUTHENTICATED_BASIC;
    handle_state_unauthenticated_basic(nsp, nse, udata);
    return 0;
  } else if (!((reslen >= 15) && strstr(res, "200 OK"))) {
    nsock_log_debug("Connection refused from proxy %s", px_ctx->px_current->nodestr);
    return -EINVAL;
  } else {
    if (proxy_ctx_node_next(px_ctx) == NULL) {
      px_ctx->px_state = PROXY_STATE_HTTP_TUNNEL_ESTABLISHED;
      forward_event(nsp, nse, udata);
    } else {
      px_ctx->px_current = proxy_ctx_node_next(px_ctx);
      px_ctx->px_state = PROXY_STATE_INITIAL;
      nsock_proxy_ev_dispatch(nsp, nse, udata);
    }
  }
  return 0;
}

static void proxy_http_handler(nsock_pool nspool, nsock_event nsevent, void *udata) {
  int rc = 0;
  struct npool *nsp = (struct npool *)nspool;
  struct nevent *nse = (struct nevent *)nsevent;

  switch (nse->iod->px_ctx->px_state) {
    case PROXY_STATE_INITIAL:
      rc = handle_state_initial(nsp, nse, udata);
      break;

    case PROXY_STATE_UNAUTHENTICATED_BASIC:
      rc = handle_state_unauthenticated_basic(nsp, nse, udata);
      break;

    case PROXY_STATE_UNAUTHENTICATED_DIGEST:
      rc = handle_state_unauthenticated_digest(nsp, nse, udata, NULL);
      break;

    case PROXY_STATE_HTTP_TCP_CONNECTED:
      if (nse->type == NSE_TYPE_READ)
        rc = handle_state_tcp_connected(nsp, nse, udata);
      break;

    case PROXY_STATE_AUTHENTICATION_ATTEMPTED:
      if (nse->type == NSE_TYPE_READ)
        rc = handle_state_authentication_attempted(nsp, nse, udata);
      break;

    case PROXY_STATE_HTTP_TUNNEL_ESTABLISHED:
      forward_event(nsp, nse, udata);
      break;

    default:
      fatal("Invalid proxy state!");
  }

  if (rc) {
    nse->status = NSE_STATUS_PROXYERROR;
    forward_event(nsp, nse, udata);
  }
}


/* ---- PROXY DEFINITION ---- */
static const struct proxy_op ProxyOpsHttp = {
  proxy_http_node_new,
  proxy_http_node_delete,
  proxy_http_handler,
};

const struct proxy_spec ProxySpecHttp = {
  "http://",
  PROXY_TYPE_HTTP,
  &ProxyOpsHttp,
};