curl/lib/krb5.c

/* GSSAPI/krb5 support for FTP - loosely based on old krb4.c
 *
 * Copyright (c) 1995, 1996, 1997, 1998, 1999 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * Copyright (c) 2004 - 2019 Daniel Stenberg
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.  */

#include "curl_setup.h"

#if defined(HAVE_GSSAPI) && !defined(CURL_DISABLE_FTP)

#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif

#include "urldata.h"
#include "curl_base64.h"
#include "ftp.h"
#include "curl_gssapi.h"
#include "sendf.h"
#include "curl_sec.h"
#include "warnless.h"

/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

static int
krb5_init(void *app_data)
{
  gss_ctx_id_t *context = app_data;
  /* Make sure our context is initialized for krb5_end. */
  *context = GSS_C_NO_CONTEXT;
  return 0;
}

static int
krb5_check_prot(void *app_data, int level)
{
  (void)app_data; /* unused */
  if(level == PROT_CONFIDENTIAL)
    return -1;
  return 0;
}

static int
krb5_decode(void *app_data, void *buf, int len,
            int level UNUSED_PARAM,
            struct connectdata *conn UNUSED_PARAM)
{
  gss_ctx_id_t *context = app_data;
  OM_uint32 maj, min;
  gss_buffer_desc enc, dec;

  (void)level;
  (void)conn;

  enc.value = buf;
  enc.length = len;
  maj = gss_unwrap(&min, *context, &enc, &dec, NULL, NULL);
  if(maj != GSS_S_COMPLETE) {
    if(len >= 4)
      strcpy(buf, "599 ");
    return -1;
  }

  memcpy(buf, dec.value, dec.length);
  len = curlx_uztosi(dec.length);
  gss_release_buffer(&min, &dec);

  return len;
}

static int
krb5_overhead(void *app_data, int level, int len)
{
  /* no arguments are used */
  (void)app_data;
  (void)level;
  (void)len;
  return 0;
}

static int
krb5_encode(void *app_data, const void *from, int length, int level, void **to)
{
  gss_ctx_id_t *context = app_data;
  gss_buffer_desc dec, enc;
  OM_uint32 maj, min;
  int state;
  int len;

  /* NOTE that the cast is safe, neither of the krb5, gnu gss and heimdal
   * libraries modify the input buffer in gss_wrap()
   */
  dec.value = (void *)from;
  dec.length = length;
  maj = gss_wrap(&min, *context,
                 level == PROT_PRIVATE,
                 GSS_C_QOP_DEFAULT,
                 &dec, &state, &enc);

  if(maj != GSS_S_COMPLETE)
    return -1;

  /* malloc a new buffer, in case gss_release_buffer doesn't work as
     expected */
  *to = malloc(enc.length);
  if(!*to)
    return -1;
  memcpy(*to, enc.value, enc.length);
  len = curlx_uztosi(enc.length);
  gss_release_buffer(&min, &enc);
  return len;
}

static int
krb5_auth(void *app_data, struct connectdata *conn)
{
  int ret = AUTH_OK;
  char *p;
  const char *host = conn->host.name;
  ssize_t nread;
  curl_socklen_t l = sizeof(conn->local_addr);
  struct Curl_easy *data = conn->data;
  CURLcode result;
  const char *service = data->set.str[STRING_SERVICE_NAME] ?
                        data->set.str[STRING_SERVICE_NAME] :
                        "ftp";
  const char *srv_host = "host";
  gss_buffer_desc input_buffer, output_buffer, _gssresp, *gssresp;
  OM_uint32 maj, min;
  gss_name_t gssname;
  gss_ctx_id_t *context = app_data;
  struct gss_channel_bindings_struct chan;
  size_t base64_sz = 0;
  struct sockaddr_in **remote_addr =
    (struct sockaddr_in **)&conn->ip_addr->ai_addr;
  char *stringp;

  if(getsockname(conn->sock[FIRSTSOCKET],
                 (struct sockaddr *)&conn->local_addr, &l) < 0)
    perror("getsockname()");

  chan.initiator_addrtype = GSS_C_AF_INET;
  chan.initiator_address.length = l - 4;
  chan.initiator_address.value = &conn->local_addr.sin_addr.s_addr;
  chan.acceptor_addrtype = GSS_C_AF_INET;
  chan.acceptor_address.length = l - 4;
  chan.acceptor_address.value = &(*remote_addr)->sin_addr.s_addr;
  chan.application_data.length = 0;
  chan.application_data.value = NULL;

  /* this loop will execute twice (once for service, once for host) */
  for(;;) {
    /* this really shouldn't be repeated here, but can't help it */
    if(service == srv_host) {
      result = Curl_ftpsend(conn, "AUTH GSSAPI");
      if(result)
        return -2;

      if(Curl_GetFTPResponse(&nread, conn, NULL))
        return -1;

      if(data->state.buffer[0] != '3')
        return -1;
    }

    stringp = aprintf("%s@%s", service, host);
    if(!stringp)
      return -2;

    input_buffer.value = stringp;
    input_buffer.length = strlen(stringp);
    maj = gss_import_name(&min, &input_buffer, GSS_C_NT_HOSTBASED_SERVICE,
                          &gssname);
    free(stringp);
    if(maj != GSS_S_COMPLETE) {
      gss_release_name(&min, &gssname);
      if(service == srv_host) {
        failf(data, "Error importing service name %s@%s", service, host);
        return AUTH_ERROR;
      }
      service = srv_host;
      continue;
    }
    /* We pass NULL as |output_name_type| to avoid a leak. */
    gss_display_name(&min, gssname, &output_buffer, NULL);
    Curl_infof(data, "Trying against %s\n", output_buffer.value);
    gssresp = GSS_C_NO_BUFFER;
    *context = GSS_C_NO_CONTEXT;

    do {
      /* Release the buffer at each iteration to avoid leaking: the first time
         we are releasing the memory from gss_display_name. The last item is
         taken care by a final gss_release_buffer. */
      gss_release_buffer(&min, &output_buffer);
      ret = AUTH_OK;
      maj = Curl_gss_init_sec_context(data,
                                      &min,
                                      context,
                                      gssname,
                                      &Curl_krb5_mech_oid,
                                      &chan,
                                      gssresp,
                                      &output_buffer,
                                      TRUE,
                                      NULL);

      if(gssresp) {
        free(_gssresp.value);
        gssresp = NULL;
      }

      if(GSS_ERROR(maj)) {
        Curl_infof(data, "Error creating security context\n");
        ret = AUTH_ERROR;
        break;
      }

      if(output_buffer.length != 0) {
        char *cmd;

        result = Curl_base64_encode(data, (char *)output_buffer.value,
                                    output_buffer.length, &p, &base64_sz);
        if(result) {
          Curl_infof(data, "base64-encoding: %s\n",
                     curl_easy_strerror(result));
          ret = AUTH_ERROR;
          break;
        }

        cmd = aprintf("ADAT %s", p);
        if(cmd)
          result = Curl_ftpsend(conn, cmd);
        else
          result = CURLE_OUT_OF_MEMORY;

        free(p);
        free(cmd);

        if(result) {
          ret = -2;
          break;
        }

        if(Curl_GetFTPResponse(&nread, conn, NULL)) {
          ret = -1;
          break;
        }

        if(data->state.buffer[0] != '2' && data->state.buffer[0] != '3') {
          Curl_infof(data, "Server didn't accept auth data\n");
          ret = AUTH_ERROR;
          break;
        }

        _gssresp.value = NULL; /* make sure it is initialized */
        p = data->state.buffer + 4;
        p = strstr(p, "ADAT=");
        if(p) {
          result = Curl_base64_decode(p + 5,
                                      (unsigned char **)&_gssresp.value,
                                      &_gssresp.length);
          if(result) {
            failf(data, "base64-decoding: %s", curl_easy_strerror(result));
            ret = AUTH_CONTINUE;
            break;
          }
        }

        gssresp = &_gssresp;
      }
    } while(maj == GSS_S_CONTINUE_NEEDED);

    gss_release_name(&min, &gssname);
    gss_release_buffer(&min, &output_buffer);

    if(gssresp)
      free(_gssresp.value);

    if(ret == AUTH_OK || service == srv_host)
      return ret;

    service = srv_host;
  }
  return ret;
}

static void krb5_end(void *app_data)
{
    OM_uint32 min;
    gss_ctx_id_t *context = app_data;
    if(*context != GSS_C_NO_CONTEXT) {
      OM_uint32 maj = gss_delete_sec_context(&min, context, GSS_C_NO_BUFFER);
      (void)maj;
      DEBUGASSERT(maj == GSS_S_COMPLETE);
    }
}

struct Curl_sec_client_mech Curl_krb5_client_mech = {
    "GSSAPI",
    sizeof(gss_ctx_id_t),
    krb5_init,
    krb5_auth,
    krb5_end,
    krb5_check_prot,
    krb5_overhead,
    krb5_encode,
    krb5_decode
};

#endif /* HAVE_GSSAPI && !CURL_DISABLE_FTP */