handshake_client.cc

/* Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */

#include "handshake.h"

#include <mysql.h> // for MYSQL structure



class Handshake_client: public Handshake
{
  SEC_WCHAR  *m_service_name;

  SEC_WCHAR   m_service_name_buf[MAX_SERVICE_NAME_LENGTH];

  Connection &m_con;

public:

  Handshake_client(Connection &con, const char *target, size_t len);
  ~Handshake_client();

  Blob  first_packet();
  Blob  process_data(const Blob&);

  Blob read_packet();
  int write_packet(Blob &data);
};


Handshake_client::Handshake_client(Connection &con, 
                                   const char *target, size_t len)
: Handshake(SSP_NAME, CLIENT), m_service_name(NULL), m_con(con)
{
  if (!target || 0 == len)
    return;

  // Convert received UPN to internal WCHAR representation.

  m_service_name= utf8_to_wchar(target, &len);

  if (m_service_name)
    DBUG_PRINT("info", ("Using target service: %S\n", m_service_name));
  else
  {
    /*
      Note: we ignore errors here - m_target will be NULL, the target name
      will not be used and system will fall-back to NTLM authentication. But
      we leave trace in error log.
    */
    ERROR_LOG(WARNING, ("Could not decode UPN sent by the server"
                        "; target service name will not be used"
                        " and Kerberos authentication will not work"));
  }
}


Handshake_client::~Handshake_client()
{
  if (m_service_name)
    free(m_service_name);
}


Blob Handshake_client::read_packet()
{
  /*
    We do a fake read in the first round because first
    packet from the server containing UPN must be read
    before the handshake context is created and the packet
    processing loop starts. We return an empty blob here
    and process_data() function will ignore it.
  */
  if (m_round == 1)
    return Blob();

  // Otherwise we read packet from the connection.

  Blob packet= m_con.read();
  m_error= m_con.error();
  if (!m_error && packet.is_null())
    m_error= true;  // (no specific error code assigned)

  if (m_error)
    return Blob();

  DBUG_PRINT("dump", ("Got the following bytes"));
  DBUG_DUMP("dump", packet.ptr(), packet.len());
  return packet;
}



int Handshake_client::write_packet(Blob &data)
{
  /*
   Length of the first data payload send by client authentication plugin is
   limited to 255 bytes (because it is wrapped inside client authentication
   packet and is length-encoded with 1 byte for the length).

   If the data payload is longer than 254 bytes, then it is sent in two parts:
   first part of length 255 will be embedded in the authentication packet, 
   second part will be sent in the following packet. Byte 255 of the first 
   part contains information about the total length of the payload. It is a
   number of blocks of size 512 bytes which is sufficient to store the
   combined packets.

   Server's logic for reading first client's payload is as follows
   (see Handshake_server::read_packet()):
   1. Read data from the authentication packet, if it is shorter than 255 bytes 
      then that is all data sent by client.
   2. If there is 255 bytes of data in the authentication packet, read another
      packet and append it to the data, skipping byte 255 of the first packet
      which can be used to allocate buffer of appropriate size.
  */

  size_t len2= 0;   // length of the second part of first data payload
  byte saved_byte;  // for saving byte 255 in which data length is stored

  if (m_round == 1 && data.len() > 254)
  {
    len2= data.len() - 254;
    DBUG_PRINT("info", ("Splitting first packet of length %lu"
                        ", %lu bytes will be sent in a second part", 
                        data.len(), len2));
    /* 
      Store in byte 255 the number of 512b blocks that are needed to
      keep all the data.
    */
    unsigned block_count= data.len()/512 + ((data.len() % 512) ? 1 : 0);

#if !defined(DBUG_OFF) && defined(WINAUTH_USE_DBUG_LIB)

    /*
      For testing purposes, use wrong block count to see how server
      handles this.
    */
    DBUG_EXECUTE_IF("winauth_first_packet_test",{
      block_count= data.len() == 601 ? 0 :
                   data.len() == 602 ? 1 : 
                   block_count;
    });

#endif

    DBUG_ASSERT(block_count < (unsigned)0x100);
    saved_byte= data[254];
    data[254] = block_count;

    data.trim(255);
  }

  DBUG_PRINT("dump", ("Sending the following data"));
  DBUG_DUMP("dump", data.ptr(), data.len());
  int ret= m_con.write(data);

  if (ret)
    return ret;

  // Write second part if it is present.
  if (len2)
  {
    data[254]= saved_byte;
    Blob data2(data.ptr() + 254, len2);
    DBUG_PRINT("info", ("Sending second part of data"));
    DBUG_DUMP("info", data2.ptr(), data2.len());
    ret= m_con.write(data2);
  }

  return ret;
}


Blob Handshake_client::process_data(const Blob &data)
{
#if !defined(DBUG_OFF) && defined(WINAUTH_USE_DBUG_LIB)
  /*
    Code for testing the logic for sending the first client payload.

    A fake data of length given by environment variable TEST_PACKET_LENGTH
    (or default 255 bytes) is sent to the server. First 2 bytes of the
    payload contain its total length (LSB first). The length of test data
    is limited to 2048 bytes.

    Upon receiving test data, server will check that data is correct and
    refuse connection. If server detects data errors it will crash on 
    assertion.

    This code is executed if debug flag "winauth_first_packet_test" is
    set, e.g. using client option:

     --debug="d,winauth_first_packet_test"

     The same debug flag must be enabled in the server, e.g. using 
     statement:

     SET GLOBAL debug= '+d,winauth_first_packet_test'; 
  */

  static byte test_buf[2048];

  if (m_round == 1 
      && DBUG_EVALUATE_IF("winauth_first_packet_test", true, false))
  {
    const char *env= getenv("TEST_PACKET_LENGTH");
    size_t len= env ? atoi(env) : 0;
    if (!len)
      len= 255;
    if (len > sizeof(test_buf))
      len= sizeof(test_buf);

    // Store data length in first 2 bytes.
    byte *ptr= test_buf;
    *ptr++= len & 0xFF;
    *ptr++= len >> 8;

    // Fill remaining bytes with known values.
    for (byte b= 0; ptr < test_buf + len; ++ptr, ++b)
      *ptr= b;

    return Blob(test_buf, len);
  };

#endif

  Security_buffer  input(data);
  SECURITY_STATUS  ret;

  m_output.free();

  ret= InitializeSecurityContextW(
         &m_cred,
         m_round == 1 ? NULL : &m_sctx,        // partial context
         m_service_name,                       // service name
         ASC_REQ_ALLOCATE_MEMORY,              // requested attributes
         0,                                    // reserved
         SECURITY_NETWORK_DREP,                // data representation
         m_round == 1 ? NULL : &input,         // input data
         0,                                    // reserved
         &m_sctx,                              // context
         &m_output,                            // output data
         &m_atts,                              // attributes
         &m_expire);                           // expire date

  if (process_result(ret))
  {
    DBUG_PRINT("error",
               ("InitializeSecurityContext() failed with error %X", ret));
    return Blob();
  }

  return m_output.as_blob();
}


/**********************************************************************/


int win_auth_handshake_client(MYSQL_PLUGIN_VIO *vio, MYSQL *mysql)
{
  DBUG_ENTER("win_auth_handshake_client");

  /*
    Check if we should enable logging.
  */
  {
    const char *opt= getenv("AUTHENTICATION_WIN_LOG");
    int opt_val= opt ? atoi(opt) : 0;
    if (opt && !opt_val)
    {
      if (!strncasecmp("on", opt, 2))    opt_val= 2;
      if (!strncasecmp("yes", opt, 3))   opt_val= 2;
      if (!strncasecmp("true", opt, 4))  opt_val= 2;
      if (!strncasecmp("debug", opt, 5)) opt_val= 4;
      if (!strncasecmp("dbug", opt, 4))  opt_val= 4;
    }
    set_log_level(opt_val);
  }

  ERROR_LOG(INFO, ("Authentication handshake for account %s", mysql->user));

  // Create connection object.

  Connection con(vio);
  DBUG_ASSERT(!con.error());

  // Read initial packet from server containing service name.

  Blob service_name= con.read();

  if (con.error() || service_name.is_null())
  {
    ERROR_LOG(ERROR, ("Error reading initial packet"));
    DBUG_RETURN(CR_ERROR);
  }
  DBUG_PRINT("info", ("Got initial packet of length %d", service_name.len()));

  // Create authentication handshake context using the given service name.

  Handshake_client hndshk(con,
                          service_name[0] ? (char *)service_name.ptr() : NULL,
                          service_name.len());
  if (hndshk.error())
  {
    ERROR_LOG(ERROR, ("Could not create authentication handshake context"));
    DBUG_RETURN(CR_ERROR);
  }

  DBUG_ASSERT(!hndshk.error());

  /*
    Read and process packets from server until handshake is complete.
    Note that the first read from server is dummy 
    (see Handshake_client::read_packet()) as we already have read the 
    first packet to establish service name.
  */
  if (hndshk.packet_processing_loop())
    DBUG_RETURN(CR_ERROR);

  DBUG_ASSERT(!hndshk.error() && hndshk.is_complete());

  DBUG_RETURN(CR_OK);
}