/* Copyright (c) 2000, 2018, 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, 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.

   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 */

#include "mysys_priv.h"
#include "m_string.h"
#ifdef __WIN__

/* Windows NT/2000 discretionary access control utility functions. */

/*
  Check if the operating system is built on NT technology.

  RETURN
    0   Windows 95/98/Me
    1   otherwise
*/

static my_bool is_nt()
{
  return GetVersion() < 0x80000000;
}

/*
  Auxilary structure to store pointers to the data which we need to keep
  around while SECURITY_ATTRIBUTES is in use.
*/

typedef struct st_my_security_attr
{
  PSID everyone_sid;
  PACL dacl;
} My_security_attr;


/*
  Allocate and initialize SECURITY_ATTRIBUTES setting up access
  rights for the owner and group `Everybody'.

  SYNOPSIS
    my_security_attr_create()
    psa                [OUT] pointer to store the pointer to SA in
    perror             [OUT] pointer to store error message if there was an
                             error
    owner_rights       [IN]  access rights for the owner
    everyone_rights    [IN]  access rights for group Everybody

  DESCRIPTION
    Set up the security attributes to provide clients with sufficient
    access rights to a kernel object. We need this function
    because if we simply grant all access to everybody (by installing
    a NULL DACL) a mailicious user can attempt a denial of service
    attack by taking ownership over the kernel object. Upon successful
    return `psa' contains a pointer to SECUIRITY_ATTRIBUTES that can be used
    to create kernel objects with proper access rights.

  RETURN
    0  success, psa is 0 or points to a valid SA structure,
       perror is left intact
   !0  error, SA is set to 0, error message is stored in perror
*/

int my_security_attr_create(SECURITY_ATTRIBUTES **psa, const char **perror,
                            DWORD owner_rights, DWORD everyone_rights)
{
  /* Top-level SID authority */
  SID_IDENTIFIER_AUTHORITY world_auth= SECURITY_WORLD_SID_AUTHORITY;
  PSID everyone_sid= 0;
  HANDLE htoken= 0;
  SECURITY_ATTRIBUTES *sa= 0;
  PACL dacl= 0;
  DWORD owner_token_length, dacl_length;
  SECURITY_DESCRIPTOR *sd;
  PTOKEN_USER owner_token;
  PSID owner_sid;
  My_security_attr *attr;

  if (! is_nt())
  {
    *psa= 0;
    return 0;
  }

  /*
    Get SID of Everyone group. Easier to retrieve all SIDs each time
    this function is called than worry about thread safety.
  */
  if (! AllocateAndInitializeSid(&world_auth, 1, SECURITY_WORLD_RID,
                                 0, 0, 0, 0, 0, 0, 0, &everyone_sid))
  {
    *perror= "Failed to retrieve the SID of Everyone group";
    goto error;
  }

  /*
    Get SID of the owner. Using GetSecurityInfo this task can be done
    in just one call instead of five, but GetSecurityInfo declared in
    aclapi.h, so I hesitate to use it.
    SIC: OpenThreadToken works only if there is an active impersonation
    token, hence OpenProcessToken is used.
  */
  if (! OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &htoken))
  {
    *perror= "Failed to retrieve thread access token";
    goto error;
  }
  GetTokenInformation(htoken, TokenUser, 0, 0, &owner_token_length);

  if (! my_multi_malloc(MYF(MY_WME),
                        &sa, ALIGN_SIZE(sizeof(SECURITY_ATTRIBUTES)) +
                             sizeof(My_security_attr),
                        &sd, sizeof(SECURITY_DESCRIPTOR),
                        &owner_token, owner_token_length,
                        0))
  {
    *perror= "Failed to allocate memory for SECURITY_ATTRIBUTES";
    goto error;
  }
  memset(owner_token, 0, owner_token_length);
  if (! GetTokenInformation(htoken, TokenUser, owner_token,
                            owner_token_length, &owner_token_length))
  {
    *perror= "GetTokenInformation failed";
    goto error;
  }
  owner_sid= owner_token->User.Sid;

  if (! IsValidSid(owner_sid))
  {
    *perror= "IsValidSid failed";
    goto error;
  }

  /* Calculate the amount of memory that must be allocated for the DACL */
  dacl_length= sizeof(ACL) + (sizeof(ACCESS_ALLOWED_ACE)-sizeof(DWORD)) * 2 +
               GetLengthSid(everyone_sid) + GetLengthSid(owner_sid);

  /* Create an ACL */
  if (! (dacl= (PACL) my_malloc(dacl_length, MYF(MY_ZEROFILL|MY_WME))))
  {
    *perror= "Failed to allocate memory for DACL";
    goto error;
  }
  if (! InitializeAcl(dacl, dacl_length, ACL_REVISION))
  {
    *perror= "Failed to initialize DACL";
    goto error;
  }
  if (! AddAccessAllowedAce(dacl, ACL_REVISION, everyone_rights, everyone_sid))
  {
    *perror= "Failed to set up DACL";
    goto error;
  }
  if (! AddAccessAllowedAce(dacl, ACL_REVISION, owner_rights, owner_sid))
  {
    *perror= "Failed to set up DACL";
    goto error;
  }
  if (! InitializeSecurityDescriptor(sd, SECURITY_DESCRIPTOR_REVISION))
  {
    *perror= "Could not initialize security descriptor";
    goto error;
  }
  if (! SetSecurityDescriptorDacl(sd, TRUE, dacl, FALSE))
  {
    *perror= "Failed to install DACL";
    goto error;
  }

  sa->nLength= sizeof(*sa);
  sa->bInheritHandle= TRUE;
  sa->lpSecurityDescriptor= sd;
  /* Save pointers to everyone_sid and dacl to be able to clean them up */
  attr= (My_security_attr*) (((char*) sa) + ALIGN_SIZE(sizeof(*sa)));
  attr->everyone_sid= everyone_sid;
  attr->dacl= dacl;
  *psa= sa;

  CloseHandle(htoken);
  return 0;
error:
  if (everyone_sid)
    FreeSid(everyone_sid);
  if (htoken)
    CloseHandle(htoken);
  my_free(sa);
  my_free(dacl);
  *psa= 0;
  return 1;
}

/*
  Cleanup security attributes freeing used memory.

  SYNOPSIS
    my_security_attr_free()
    sa   security attributes
*/

void my_security_attr_free(SECURITY_ATTRIBUTES *sa)
{
  if (sa)
  {
    My_security_attr *attr= (My_security_attr*)
                            (((char*)sa) + ALIGN_SIZE(sizeof(*sa)));
    PACL dacl_from_descriptor= NULL;
    BOOL dacl_present_in_descriptor= FALSE;
    BOOL dacl_defaulted= FALSE;
    // If the DACL in the descriptor is not the same as that in the
    // My_security_attr, it will have been created by a call to SetEntriesInAcl
    // and thus must be freed by a call to LocalFree.
    if (GetSecurityDescriptorDacl(sa->lpSecurityDescriptor,
      &dacl_present_in_descriptor,
      &dacl_from_descriptor, &dacl_defaulted) &&
      dacl_present_in_descriptor && !dacl_defaulted &&
      attr->dacl != dacl_from_descriptor) {
      LocalFree(dacl_from_descriptor);
    }

    FreeSid(attr->everyone_sid);
    my_free(attr->dacl);
    my_free(sa);
  }
}

#endif /* __WIN__ */
