curl/lib/security.c

/* This source code was modified by Martin Hedenfalk <mhe@stacken.kth.se> for
 * use in Curl. His latest changes were done 2000-09-18.
 *
 * It has since been patched and modified a lot by Daniel Stenberg
 * <daniel@haxx.se> to make it better applied to curl conditions, and to make
 * it not use globals, pollute name space and more. This source code awaits a
 * rewrite to work around the paragraph 2 in the BSD licenses as explained
 * below.
 *
 * Copyright (c) 1998, 1999 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 *
 * Copyright (C) 2001 - 2010, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * 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 "setup.h"

#ifndef CURL_DISABLE_FTP
#if defined(HAVE_KRB4) || defined(HAVE_GSSAPI)

#define _MPRINTF_REPLACE /* we want curl-functions instead of native ones */
#include <curl/mprintf.h>

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

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

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "urldata.h"
#include "krb4.h"
#include "curl_base64.h"
#include "sendf.h"
#include "ftp.h"
#include "curl_memory.h"
#include "rawstr.h"

/* The last #include file should be: */
#include "memdebug.h"

static const struct {
  enum protection_level level;
  const char *name;
} level_names[] = {
  { prot_clear, "clear" },
  { prot_safe, "safe" },
  { prot_confidential, "confidential" },
  { prot_private, "private" }
};

static enum protection_level
name_to_level(const char *name)
{
  int i;
  for(i = 0; i < (int)sizeof(level_names)/(int)sizeof(level_names[0]); i++)
    if(checkprefix(name, level_names[i].name))
      return level_names[i].level;
  return (enum protection_level)-1;
}

/* Convert a protocol |level| to its char representation.
   We take an int to catch programming mistakes. */
static char level_to_char(int level) {
  switch(level) {
  case prot_clear:
    return 'C';
  case prot_safe:
    return 'S';
  case prot_confidential:
    return 'E';
  case prot_private:
    return 'P';
  case prot_cmd:
    /* Fall through */
  default:
    /* Those 2 cases should not be reached! */
    break;
  }
  DEBUGASSERT(0);
  /* Default to the most secure alternative. */
  return 'P';
}

static const struct Curl_sec_client_mech * const mechs[] = {
#if defined(HAVE_GSSAPI)
  &Curl_krb5_client_mech,
#endif
#if defined(HAVE_KRB4)
  &Curl_krb4_client_mech,
#endif
  NULL
};

/* Send an FTP command defined by |message| and the optional arguments. The
   function returns the ftp_code. If an error occurs, -1 is returned. */
static int ftp_send_command(struct connectdata *conn, const char *message, ...)
{
  int ftp_code;
  ssize_t nread;
  va_list args;

  va_start(args, message);
  if(Curl_ftpsendf(conn, message, args) != CURLE_OK) {
    ftp_code = -1;
  }
  else {
    if(Curl_GetFTPResponse(&nread, conn, &ftp_code) != CURLE_OK)
      ftp_code = -1;
  }

  (void)nread; /* Unused */
  va_end(args);
  return ftp_code;
}

/* Read |len| from the socket |fd| and store it in |to|. Return a
   CURLcode saying whether an error occured or CURLE_OK if |len| was read. */
static CURLcode
socket_read(curl_socket_t fd, void *to, size_t len)
{
  char *to_p = to;
  CURLcode code;
  ssize_t nread;

  while(len > 0) {
    code = Curl_read_plain(fd, to_p, len, &nread);
    if(code == CURLE_OK) {
      len -= nread;
      to_p += nread;
    }
    else {
      /* FIXME: We are doing a busy wait */
      if(code == CURLE_AGAIN)
        continue;
      return code;
    }
  }
  return CURLE_OK;
}


/* Write |len| bytes from the buffer |to| to the socket |fd|. Return a
   CURLcode saying whether an error occured or CURLE_OK if |len| was written. */
static CURLcode
socket_write(struct connectdata *conn, curl_socket_t fd, const void *to, size_t len)
{
  const char *to_p = to;
  CURLcode code;
  ssize_t written;

  while(len > 0) {
    code = Curl_write_plain(conn, fd, to_p, len, &written);
    if(code == CURLE_OK) {
      len -= written;
      to_p += written;
    }
    else {
      /* FIXME: We are doing a busy wait */
      if(code == CURLE_AGAIN)
        continue;
      return code;
    }
  }
  return CURLE_OK;
}

static CURLcode read_data(struct connectdata *conn,
                          curl_socket_t fd,
                          struct krb4buffer *buf)
{
  int len;
  void* tmp;
  CURLcode ret;

  ret = socket_read(fd, &len, sizeof(len));
  if (ret != CURLE_OK)
    return ret;

  len = ntohl(len);
  tmp = realloc(buf->data, len);
  if (tmp == NULL)
    return CURLE_OUT_OF_MEMORY;

  ret = socket_read(fd, buf->data, len);
  if (ret != CURLE_OK)
    return ret;
  buf->size = (conn->mech->decode)(conn->app_data, buf->data, len,
                                   conn->data_prot, conn);
  buf->index = 0;
  return CURLE_OK;
}

static size_t
buffer_read(struct krb4buffer *buf, const char *data, size_t len)
{
  size_t buf_capacity = buf->size - buf->index;
  DEBUGASSERT(buf->size > buf->index);
  if(buf_capacity < len)
    len = buf_capacity;
  memcpy(buf, data, len);
  buf->index += len;
  return len;
}

static ssize_t sec_read(struct connectdata *conn, int num,
                        char *buffer, size_t length, CURLcode *err)
{
  size_t len;
  int rx = 0;
  curl_socket_t fd = conn->sock[num];

  *err = CURLE_OK;

  if(conn->in_buffer.eof_flag) {
    conn->in_buffer.eof_flag = 0;
    return 0;
  }

  len = buffer_read(&conn->in_buffer, buffer, length);
  length -= len;
  rx += len;
  buffer = (char*)buffer + len;

  while(length) {
    if(read_data(conn, fd, &conn->in_buffer) != CURLE_OK)
      return -1;
    if(conn->in_buffer.size == 0) {
      if(rx)
        conn->in_buffer.eof_flag = 1;
      return rx;
    }
    len = buffer_read(&conn->in_buffer, buffer, length);
    length -= len;
    rx += len;
    buffer = (char*)buffer + len;
  }
  return rx;
}

static int
sec_send(struct connectdata *conn, int fd, const char *from, int length)
{
  int bytes;
  void *buf;
  enum protection_level protlevel = conn->data_prot;
  int iscmd = protlevel == prot_cmd;

  if(iscmd) {
    if(!strncmp(from, "PASS ", 5) || !strncmp(from, "ACCT ", 5))
      protlevel = prot_private;
    else
      protlevel = conn->command_prot;
  }
  bytes = (conn->mech->encode)(conn->app_data, from, length, protlevel,
                               &buf, conn);
  if(iscmd) {
    char *cmdbuf;

    bytes = Curl_base64_encode(conn->data, (char *)buf, bytes, &cmdbuf);
    if(bytes > 0) {
      if(protlevel == prot_private)
        socket_write(conn, fd, "ENC ", 4);
      else
        socket_write(conn, fd, "MIC ", 4);
      socket_write(conn, fd, cmdbuf, bytes);
      socket_write(conn, fd, "\r\n", 2);
      Curl_infof(conn->data, "%s %s\n",
                 protlevel == prot_private ? "ENC" : "MIC", cmdbuf);
      free(cmdbuf);
    }
  }
  else {
    bytes = htonl(bytes);
    socket_write(conn, fd, &bytes, sizeof(bytes));
    socket_write(conn, fd, buf, ntohl(bytes));
  }
  free(buf);
  return length;
}

static ssize_t sec_write(struct connectdata *conn, int fd,
                         const char *buffer, int length)
{
  int len = conn->buffer_size;
  int tx = 0;

  len -= (conn->mech->overhead)(conn->app_data, conn->data_prot, len);
  if(len <= 0)
    len = length;
  while(length){
    if(length < len)
      len = length;
    sec_send(conn, fd, buffer, len);
    length -= len;
    buffer += len;
    tx += len;
  }
  return tx;
}

int
Curl_sec_fflush_fd(struct connectdata *conn, int fd)
{
  if(conn->data_prot != prot_clear) {
    sec_send(conn, fd, NULL, 0);
  }
  return 0;
}

static ssize_t _sec_send(struct connectdata *conn, int num,
                         const void *buffer, size_t length, CURLcode *err)
{
  curl_socket_t fd = conn->sock[num];
  *err = CURLE_OK;
  return sec_write(conn, fd, buffer, length);
}

int
Curl_sec_read_msg(struct connectdata *conn, char *s, int level)
{
  int len;
  unsigned char *buf;
  int code;

  len = Curl_base64_decode(s + 4, &buf); /* XXX */
  if(len > 0)
    len = (conn->mech->decode)(conn->app_data, buf, len, level, conn);
  else
    return -1;

  if(len < 0) {
    free(buf);
    return -1;
  }

  if(conn->data->set.verbose) {
    buf[len] = '\n';
    Curl_debug(conn->data, CURLINFO_HEADER_IN, (char *)buf, len + 1, conn);
  }

  buf[len] = '\0';

  if(buf[3] == '-')
    code = 0;
  else
    sscanf((char *)buf, "%d", &code);
  if(buf[len-1] == '\n')
    buf[len-1] = '\0';
  strcpy(s, (char *)buf);
  free(buf);
  return code;
}

enum protection_level
Curl_set_command_prot(struct connectdata *conn, enum protection_level level)
{
  enum protection_level old = conn->command_prot;
  conn->command_prot = level;
  return old;
}

/* FIXME: The error code returned here is never checked. */
int Curl_sec_set_protection_level(struct connectdata *conn)
{
  int code;
  char* pbsz;
  static unsigned int buffer_size = 1 << 20; /* 1048576 */
  enum protection_level level = conn->request_data_prot;

  if(!conn->sec_complete) {
    infof(conn->data, "Trying to change the protection level after the"
                      "completion of the data exchange.");
    return -1;
  }

  /* Bail out if we try to set up the same level */
  if(conn->data_prot == level)
    return 0;

  if(level) {
    code = ftp_send_command(conn, "PSBZ %u", buffer_size);
    if(code < 0)
      return -1;

    if(code/100 != 2) {
      failf(conn->data, "Failed to set the protection's buffer size.");
      return -1;
    }
    conn->buffer_size = buffer_size;

    pbsz = strstr(conn->data->state.buffer, "PBSZ=");
    if(pbsz) {
      /* FIXME: Checks for errors in sscanf? */
      sscanf(pbsz, "PBSZ=%u", &buffer_size);
      if(buffer_size < conn->buffer_size)
        conn->buffer_size = buffer_size;
    }
  }

  /* Now try to negiociate the protection level. */
  code = ftp_send_command(conn, "PROT %c", level_to_char(level));

  if(code < 0)
    return -1;

  if(code/100 != 2) {
    failf(conn->data, "Failed to set the protection level.");
    return -1;
  }

  conn->data_prot = level;
  if(level == prot_private)
    conn->command_prot = level;

  return 0;
}

int
Curl_sec_request_prot(struct connectdata *conn, const char *level)
{
  int l = name_to_level(level);
  if(l == -1)
    return -1;
  conn->request_data_prot = (enum protection_level)l;
  return 0;
}

static CURLcode choose_mech(struct connectdata *conn)
{
  int ret;
  struct SessionHandle *data = conn->data;
  const struct Curl_sec_client_mech * const *mech;
  void *tmp_allocation;
  const char *mech_name;

  for(mech = mechs; (*mech); ++mech) {
    mech_name = (*mech)->name;
    /* We have no mechanism with a NULL name but keep this check */
    DEBUGASSERT(mech_name != NULL);
    if(mech_name == NULL) {
      infof(data, "Skipping mechanism with empty name (%p)", mech);
      continue;
    }
    tmp_allocation = realloc(conn->app_data, (*mech)->size);
    if(tmp_allocation == NULL) {
      failf(data, "Failed realloc of size %u", (*mech)->size);
      mech = NULL;
      return CURLE_OUT_OF_MEMORY;
    }
    conn->app_data = tmp_allocation;

    if((*mech)->init) {
      ret = (*mech)->init(conn);
      if(ret != 0) {
        infof(data, "Failed initialization for %s. Skipping it.", mech_name);
        continue;
      }
    }

    infof(data, "Trying mechanism %s...", mech_name);
    ret = ftp_send_command(conn, "AUTH %s", mech_name);
    if(ret < 0)
      /* FIXME: This error is too generic but it is OK for now. */
      return CURLE_COULDNT_CONNECT;

    if(ret/100 != 3) {
      switch(ret) {
      case 504:
        infof(data, "Mechanism %s is not supported by the server (server "
                    "returned ftp code: 504).", mech_name);
        break;
      case 534:
        infof(data, "Mechanism %s was rejected by the server (server returned "
                    "ftp code: 534).", mech_name);
        break;
      default:
        if(ret/100 == 5) {
          infof(data, "The server does not support the security extensions.");
          return CURLE_USE_SSL_FAILED;
        }
        break;
      }
      continue;
    }

    /* Authenticate */
    ret = ((*mech)->auth)(conn->app_data, conn);

    if(ret == AUTH_CONTINUE)
      continue;
    else if(ret != AUTH_OK) {
      /* Mechanism has dumped the error to stderr, don't error here. */
      return -1;
    }
    DEBUGASSERT(ret == AUTH_OK);

    conn->mech = *mech;
    conn->sec_complete = 1;
    if (conn->data_prot != prot_clear) {
      conn->recv[FIRSTSOCKET] = sec_read;
      conn->send[FIRSTSOCKET] = _sec_send;
      conn->recv[SECONDARYSOCKET] = sec_read;
      conn->send[SECONDARYSOCKET] = _sec_send;
    }
    conn->command_prot = prot_safe;
    /* Set the requested protection level */
    /* BLOCKING */
    Curl_sec_set_protection_level(conn);
    break;
  }

  return mech != NULL ? CURLE_OK : CURLE_FAILED_INIT;
}

int
Curl_sec_login(struct connectdata *conn)
{
  CURLcode code = choose_mech(conn);
  return code == CURLE_OK;
}


void
Curl_sec_end(struct connectdata *conn)
{
  if(conn->mech != NULL) {
    if(conn->mech->end)
      (conn->mech->end)(conn->app_data);
    memset(conn->app_data, 0, conn->mech->size);
    free(conn->app_data);
    conn->app_data = NULL;
  }
  conn->sec_complete = 0;
  conn->data_prot = (enum protection_level)0;
  conn->mech=NULL;
}

#endif /* HAVE_KRB4 || HAVE_GSSAPI */

#endif /* CURL_DISABLE_FTP */