/* Copyright (c) 2011, 2023, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   Without limiting anything contained in the foregoing, this file,
   which is part of C Driver for MySQL (Connector/C), is also subject to the
   Universal FOSS Exception, version 1.0, a copy of which can be found at
   http://oss.oracle.com/licenses/universal-foss-exception.

   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, version 2.0, 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 St, Fifth Floor, Boston, MA  02110-1301  USA */

// First include (the generated) my_config.h, to get correct platform defines.
#include "my_config.h"

#if defined(HAVE_OPENSSL)
#include "crypt_genhash_impl.h"
#include "mysql/client_authentication.h"
#include "m_ctype.h"
#include "sql_common.h"
#include "errmsg.h"
#include "sql_string.h"

#include <string.h>
#include <stdarg.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <openssl/sha.h>
#if defined(_WIN32) && !defined(_OPENSSL_Applink) && defined(HAVE_OPENSSL_APPLINK_C)
#include <openssl/applink.c>
#endif
#include "mysql/plugin.h"

#define MAX_CIPHER_LENGTH 1024

#define SHA2_SCRAMBLE_LENGTH SHA256_DIGEST_LENGTH

mysql_mutex_t g_public_key_mutex;

int sha256_password_init(char *a, size_t b, int c, va_list d)
{
  mysql_mutex_init(0,&g_public_key_mutex, MY_MUTEX_INIT_SLOW);
  return 0;
}

int sha256_password_deinit(void)
{
  mysql_mutex_destroy(&g_public_key_mutex);
  return 0;
}


/**
  Reads and parse RSA public key data from a file.

  @param mysql connection handle with file path data
 
  @return Pointer to the RSA public key storage buffer
*/

RSA *rsa_init(MYSQL *mysql)
{
  static RSA *g_public_key= NULL;
  RSA *key= NULL;

  mysql_mutex_lock(&g_public_key_mutex);
  key= g_public_key;
  mysql_mutex_unlock(&g_public_key_mutex);

  if (key != NULL)
    return key;

  FILE *pub_key_file= NULL;

  if (mysql->options.extension != NULL &&
      mysql->options.extension->server_public_key_path != NULL &&
      mysql->options.extension->server_public_key_path[0] != '\0')
  {
    pub_key_file= fopen(mysql->options.extension->server_public_key_path,
                        "r");
  }
  /* No public key is used; return 0 without errors to indicate this. */
  else
    return 0;

  if (pub_key_file == NULL)
  {
    /*
      If a key path was submitted but no key located then we print an error
      message. Else we just report that there is no public key.
    */
    my_message_local(WARNING_LEVEL, "Can't locate server public key '%s'",
                     mysql->options.extension->server_public_key_path);

    return 0;
  }

  mysql_mutex_lock(&g_public_key_mutex);
  key= g_public_key= PEM_read_RSA_PUBKEY(pub_key_file, 0, 0, 0);
  mysql_mutex_unlock(&g_public_key_mutex);
  fclose(pub_key_file);
  if (g_public_key == NULL)
  {
    ERR_clear_error();
    my_message_local(WARNING_LEVEL, "Public key is not in PEM format: '%s'",
                     mysql->options.extension->server_public_key_path);
    return 0;
  }

  return key;
}

/**
  Authenticate the client using the RSA or TLS and a SHA256 salted password.
 
  @param vio Provides plugin access to communication channel
  @param mysql Client connection handler

  @return Error status
    @retval CR_ERROR An error occurred.
    @retval CR_OK Authentication succeeded.
*/

extern "C"
int sha256_password_auth_client(MYSQL_PLUGIN_VIO *vio, MYSQL *mysql)
{
  bool uses_password= mysql->passwd[0] != 0;
  unsigned char encrypted_password[MAX_CIPHER_LENGTH];
  static char request_public_key= '\1';
  RSA *public_key= NULL;
  bool got_public_key_from_server= false;
  bool connection_is_secure= false;
  unsigned char scramble_pkt[20];
  unsigned char *pkt;


  DBUG_ENTER("sha256_password_auth_client");

  /*
    Get the scramble from the server because we need it when sending encrypted
    password.
  */
  if (vio->read_packet(vio, &pkt) != SCRAMBLE_LENGTH + 1)
  {
    DBUG_PRINT("info",("Scramble is not of correct length."));
    DBUG_RETURN(CR_ERROR);
  }
  if (pkt[SCRAMBLE_LENGTH] != '\0')
  {
    DBUG_PRINT("info",("Missing protocol token in scramble data."));
    DBUG_RETURN(CR_ERROR);
  }
  /*
    Copy the scramble to the stack or it will be lost on the next use of the 
    net buffer.
  */
  memcpy(scramble_pkt, pkt, SCRAMBLE_LENGTH);

  if (mysql_get_ssl_cipher(mysql) != NULL)
    connection_is_secure= true;

  /* If connection isn't secure attempt to get the RSA public key file */
  if (!connection_is_secure)
  {
    public_key= rsa_init(mysql);
  }

  if (!uses_password)
  {
    /* We're not using a password */
    static const unsigned char zero_byte= '\0'; 
    if (vio->write_packet(vio, &zero_byte, 1))
      DBUG_RETURN(CR_ERROR);
  }
  else
  {
    /* Password is a 0-terminated byte array ('\0' character included) */
    unsigned int passwd_len= static_cast<unsigned int>(strlen(mysql->passwd) + 1);
    if (!connection_is_secure)
    {
      /*
        If no public key; request one from the server.
      */
      if (public_key == NULL)
      {
        if (vio->write_packet(vio, (const unsigned char *) &request_public_key,
                              1))
          DBUG_RETURN(CR_ERROR);
      
        int pkt_len= 0;
        unsigned char *pkt;
        if ((pkt_len= vio->read_packet(vio, &pkt)) == -1)
          DBUG_RETURN(CR_ERROR);
        BIO* bio= BIO_new_mem_buf(pkt, pkt_len);
        public_key= PEM_read_bio_RSA_PUBKEY(bio, NULL, NULL, NULL);
        BIO_free(bio);
        if (public_key == 0)
        {
          ERR_clear_error();
          DBUG_RETURN(CR_ERROR);
        }
        got_public_key_from_server= true;
      }

      /*
        An arbitrary limitation based on the assumption that passwords
        larger than e.g. 15 symbols don't contribute to security.
        Note also that it's furter restricted to RSA_size() - 41 down
        below, so this leaves 471 bytes of possible RSA key sizes which
        should be reasonably future-proof.
        We avoid heap allocation for speed reasons.
      */
      char passwd_scramble[512];

      if (passwd_len > sizeof(passwd_scramble))
      {
        /* password too long for the buffer */
        if (got_public_key_from_server)
          RSA_free(public_key);
        DBUG_RETURN(CR_ERROR);
      }
      memmove(passwd_scramble, mysql->passwd, passwd_len);
      
      /* Obfuscate the plain text password with the session scramble */
      xor_string(passwd_scramble, passwd_len - 1, (char *) scramble_pkt,
                 SCRAMBLE_LENGTH);
      /* Encrypt the password and send it to the server */
      int cipher_length= RSA_size(public_key);
      /*
        When using RSA_PKCS1_OAEP_PADDING the password length must be less
        than RSA_size(rsa) - 41.
      */
      if (passwd_len + 41 >= (unsigned) cipher_length)
      {
        /* password message is to long */
        if (got_public_key_from_server)
          RSA_free(public_key);
        DBUG_RETURN(CR_ERROR);
      }
      RSA_public_encrypt(passwd_len, (unsigned char *) passwd_scramble,
                         encrypted_password,
                         public_key, RSA_PKCS1_OAEP_PADDING);
      if (got_public_key_from_server)
        RSA_free(public_key);

      if (vio->write_packet(vio, (uchar*) encrypted_password, cipher_length))
        DBUG_RETURN(CR_ERROR);
    }
    else
    {
      /* The vio is encrypted already; just send the plain text passwd */
      if (vio->write_packet(vio, (uchar*) mysql->passwd, passwd_len))
        DBUG_RETURN(CR_ERROR);
    }
  }
    
  DBUG_RETURN(CR_OK);
}

/* caching_sha2_password */

int caching_sha2_password_init(char *, size_t, int, va_list)
{
  return 0;
}

int caching_sha2_password_deinit(void)
{
  return 0;
}

static bool is_secure_transport(MYSQL *mysql)
{
  if (!mysql || !mysql->net.vio)
    return false;
  switch (mysql->net.vio->type)
  {
    case VIO_TYPE_SSL:
    {
      if (mysql_get_ssl_cipher(mysql) == NULL)
        return false;
    }
   // Fall through
   case VIO_TYPE_SHARED_MEMORY:
   // Fall through
   case VIO_TYPE_SOCKET:
     return true;
   default:
     return false;
  }
  return false;
}

/**
  Authenticate the client using the RSA or TLS and a SHA2 salted password.

  @param vio Provides plugin access to communication channel
  @param mysql Client connection handler

  @return Error status
    @retval CR_ERROR An error occurred.
    @retval CR_OK Authentication succeeded.
*/

static char request_public_key= '\2';
static char fast_auth_success= '\3';
static char perform_full_authentication= '\4';

int caching_sha2_password_auth_client(MYSQL_PLUGIN_VIO *vio, MYSQL *mysql)
{
  bool uses_password= mysql->passwd[0] != 0;
  unsigned char encrypted_password[MAX_CIPHER_LENGTH];
  RSA *public_key= NULL;
  bool got_public_key_from_server= false;
  bool connection_is_secure= false;
  unsigned char scramble_pkt[20];
  unsigned char *pkt;

  DBUG_ENTER("caching_sha2_password_auth_client");

  /*
    Get the scramble from the server because we need it when sending encrypted
    password.
  */
  if (vio->read_packet(vio, &pkt) != SCRAMBLE_LENGTH + 1)
  {
    DBUG_PRINT("info", ("Scramble is not of correct length."));
    DBUG_RETURN(CR_ERROR);
  }

  if (pkt[SCRAMBLE_LENGTH] != '\0')
  {
    DBUG_PRINT("info", ("Missing protocol token in scramble data."));
    DBUG_RETURN(CR_ERROR);
  }

  /*
    Copy the scramble to the stack or it will be lost on the next use of the
    net buffer.
  */
  memcpy(scramble_pkt, pkt, SCRAMBLE_LENGTH);

  connection_is_secure= is_secure_transport(mysql);

  if (!uses_password)
  {
    /* We're not using a password */
    static const unsigned char zero_byte= '\0';
    if (vio->write_packet(vio, &zero_byte, 1))
      DBUG_RETURN(CR_ERROR);
    DBUG_RETURN(CR_OK);
  }
  else
  {
    /* Password is a 0-terminated byte array ('\0' character included) */
    unsigned int passwd_len=
      static_cast<unsigned int>(strlen(mysql->passwd) + 1);
    int pkt_len= 0;
    {
      /* First try with SHA2 scramble */
      unsigned char sha2_scramble[SHA2_SCRAMBLE_LENGTH];
      if (generate_sha256_scramble(sha2_scramble, SHA2_SCRAMBLE_LENGTH,
                                   mysql->passwd, passwd_len - 1,
                                   (char *)scramble_pkt, SCRAMBLE_LENGTH))
      {
        set_mysql_extended_error(mysql, CR_AUTH_PLUGIN_ERR, unknown_sqlstate,
                                 ER(CR_AUTH_PLUGIN_ERR),
                                 "caching_sha2_password",
                                 "Failed to generate scramble");
        DBUG_RETURN(CR_ERROR);
      }

      if (vio->write_packet(vio, sha2_scramble, SHA2_SCRAMBLE_LENGTH))
        DBUG_RETURN(CR_ERROR);

      if ((pkt_len= vio->read_packet(vio, &pkt)) == -1)
        DBUG_RETURN(CR_ERROR);

      if (pkt_len == 1 && *pkt == fast_auth_success)
        DBUG_RETURN(CR_OK);

      /* An OK packet would follow */
    }

    if (pkt_len != 1 || *pkt != perform_full_authentication)
    {
      DBUG_PRINT("info", ("Unexpected reply from server."));
      DBUG_RETURN(CR_ERROR);
    }

    if (!connection_is_secure)
    {
      /* If connection isn't secure attempt to get the RSA public key file */
      public_key= rsa_init(mysql);

      if (public_key == NULL && mysql->options.extension &&
          mysql->options.extension->get_server_public_key)
      {
        // If no public key; request one from the server.
        if (vio->write_packet(vio, (const unsigned char *)&request_public_key,
                              1))
          DBUG_RETURN(CR_ERROR);

        if ((pkt_len= vio->read_packet(vio, &pkt)) <= 0)
          DBUG_RETURN(CR_ERROR);
        BIO *bio= BIO_new_mem_buf(pkt, pkt_len);
        public_key= PEM_read_bio_RSA_PUBKEY(bio, NULL, NULL, NULL);
        BIO_free(bio);
        if (public_key == 0)
        {
          ERR_clear_error();
          DBUG_PRINT("info", ("Failed to parse public key"));
          DBUG_RETURN(CR_ERROR);
        }
        got_public_key_from_server= true;
      }

      if (public_key)
      {
        /*
          An arbitrary limitation based on the assumption that passwords
          larger than e.g. 15 symbols don't contribute to security.
          Note also that it's further restricted to RSA_size() - 11 down
          below, so this leaves 471 bytes of possible RSA key sizes which
          should be reasonably future-proof.
          We avoid heap allocation for speed reasons.
        */
        char passwd_scramble[512];

        if (passwd_len > sizeof(passwd_scramble))
        {
          /* password too long for the buffer */
          if (got_public_key_from_server) RSA_free(public_key);
          DBUG_PRINT("info", ("Password is too long."));
          DBUG_RETURN(CR_ERROR);
        }
        memmove(passwd_scramble, mysql->passwd, passwd_len);

        /* Obfuscate the plain text password with the session scramble */
        xor_string(passwd_scramble, passwd_len - 1, (char *)scramble_pkt,
                   SCRAMBLE_LENGTH);
        /* Encrypt the password and send it to the server */
        int cipher_length= RSA_size(public_key);
        /*
          When using RSA_PKCS1_OAEP_PADDING the password length must be less
          than RSA_size(rsa) - 41.
        */
        if (passwd_len + 41 >= (unsigned)cipher_length)
        {
          /* password message is to long */
          if (got_public_key_from_server)
            RSA_free(public_key);
          DBUG_PRINT("info", ("Password is too long to be encrypted using "
                              "given public key."));
          DBUG_RETURN(CR_ERROR);
        }
        RSA_public_encrypt(passwd_len, (unsigned char *)passwd_scramble,
                           encrypted_password, public_key,
                           RSA_PKCS1_OAEP_PADDING);
        if (got_public_key_from_server)
          RSA_free(public_key);

        if (vio->write_packet(vio, (uchar *)encrypted_password, cipher_length))
          DBUG_RETURN(CR_ERROR);
      }
      else
      {
        set_mysql_extended_error(mysql, CR_AUTH_PLUGIN_ERR, unknown_sqlstate,
                                 ER(CR_AUTH_PLUGIN_ERR),
                                 "caching_sha2_password",
                                 "Authentication requires secure connection.");
        DBUG_RETURN(CR_ERROR);
      }
    }
    else
    {
      /* The vio is encrypted already; just send the plain text passwd */
      if (vio->write_packet(vio, (uchar *)mysql->passwd, passwd_len))
        DBUG_RETURN(CR_ERROR);
    }
  }
  DBUG_RETURN(CR_OK);
}

#endif /* HAVE_OPENSSL */