Attachment #30862: localscan dlopen patch for bug #47106

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

#ifdef DLOPEN_LOCAL_SCAN

This file contains a template local_scan() function that just returns ACCEPT.

#include <dlfcn.h>

If you want to implement your own version, you should copy this file to, say

static int (*local_scan_fn)(int fd, uschar **return_text) = NULL;

Local/local_scan.c, and edit the copy. To use your version instead of the

static int load_local_scan_library(void);

default, you must set

#endif

LOCAL_SCAN_SOURCE=Local/local_scan.c

in your Local/Makefile. This makes it easy to copy your version for use with

subsequent Exim releases.

For a full description of the API to this function, see the Exim specification.

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

/* This is the only Exim header that you should include. The effect of

including any other Exim header is not defined, and may change from release to

release. Use only the documented interface! */

#include "local_scan.h"

/* This is a "do-nothing" version of a local_scan() function. The arguments

are:

  fd             The file descriptor of the open -D file, which contains the

                   body of the message. The file is open for reading and

                   writing, but modifying it is dangerous and not recommended.

  return_text    A pointer to an unsigned char* variable which you can set in

                   order to return a text string. It is initialized to NULL.

The return values of this function are:

  LOCAL_SCAN_ACCEPT

                 The message is to be accepted. The return_text argument is

                   saved in $local_scan_data.

  LOCAL_SCAN_REJECT

                 The message is to be rejected. The returned text is used

                   in the rejection message.

  LOCAL_SCAN_TEMPREJECT

                 This specifies a temporary rejection. The returned text

                   is used in the rejection message.

*/

return LOCAL_SCAN_ACCEPT;

#ifdef DLOPEN_LOCAL_SCAN

/* local_scan_path is defined AND not the empty string */

if (local_scan_path && *local_scan_path)

  {

  if (!local_scan_fn)

    {

    if (!load_local_scan_library())

      {

        char *base_msg , *error_msg , *final_msg ;

        int final_length = -1 ;

        base_msg=US"Local configuration error - local_scan() library failure\n";

        error_msg = dlerror() ;

        final_length = strlen(base_msg) + strlen(error_msg) + 1 ;

        final_msg = (char*)malloc( final_length*sizeof(char) ) ;

        *final_msg = '\0' ;

        strcat( final_msg , base_msg ) ;

        strcat( final_msg , error_msg ) ;

        *return_text = final_msg ;

      return LOCAL_SCAN_TEMPREJECT;

      }

    }

    return local_scan_fn(fd, return_text);

  }

else

#endif

  return LOCAL_SCAN_ACCEPT;

}

#ifdef DLOPEN_LOCAL_SCAN

static int load_local_scan_library(void)

{

/* No point in keeping local_scan_lib since we'll never dlclose() anyway */

void *local_scan_lib = NULL;

int (*local_scan_version_fn)(void);

int vers_maj;

int vers_min;

local_scan_lib = dlopen(local_scan_path, RTLD_NOW);

if (!local_scan_lib)

  {

  log_write(0, LOG_MAIN|LOG_REJECT, "local_scan() library open failed - "

    "message temporarily rejected");

  return FALSE;

  }

local_scan_version_fn = dlsym(local_scan_lib, "local_scan_version_major");

if (!local_scan_version_fn)

  {

  dlclose(local_scan_lib);

  log_write(0, LOG_MAIN|LOG_REJECT, "local_scan() library doesn't contain "

    "local_scan_version_major() function - message temporarily rejected");

  return FALSE;

  }

/* The major number is increased when the ABI is changed in a non

   backward compatible way. */

vers_maj = local_scan_version_fn();

local_scan_version_fn = dlsym(local_scan_lib, "local_scan_version_minor");

if (!local_scan_version_fn)

  {

  dlclose(local_scan_lib);

  log_write(0, LOG_MAIN|LOG_REJECT, "local_scan() library doesn't contain "

    "local_scan_version_minor() function - message temporarily rejected");

  return FALSE;

  }

/* The minor number is increased each time a new feature is added (in a

   way that doesn't break backward compatibility) -- Marc */

vers_min = local_scan_version_fn();

if (vers_maj != LOCAL_SCAN_ABI_VERSION_MAJOR)

  {

  dlclose(local_scan_lib);

  local_scan_lib = NULL;

  log_write(0, LOG_MAIN|LOG_REJECT, "local_scan() has an incompatible major"

    "version number, you need to recompile your module for this version"

    "of exim (The module was compiled for version %d.%d and this exim provides"

    "ABI version %d.%d)", vers_maj, vers_min, LOCAL_SCAN_ABI_VERSION_MAJOR,

    LOCAL_SCAN_ABI_VERSION_MINOR);

  return FALSE;

  }

else if (vers_min > LOCAL_SCAN_ABI_VERSION_MINOR)

  {

  dlclose(local_scan_lib);

  local_scan_lib = NULL;

  log_write(0, LOG_MAIN|LOG_REJECT, "local_scan() has an incompatible minor"

    "version number, you need to recompile your module for this version"

    "of exim (The module was compiled for version %d.%d and this exim provides"

    "ABI version %d.%d)", vers_maj, vers_min, LOCAL_SCAN_ABI_VERSION_MAJOR,

    LOCAL_SCAN_ABI_VERSION_MINOR);

  return FALSE;

  }

local_scan_fn = dlsym(local_scan_lib, "local_scan");

if (!local_scan_fn)

  {

  dlclose(local_scan_lib);

  log_write(0, LOG_MAIN|LOG_REJECT, "local_scan() library doesn't contain "

    "local_scan() function - message temporarily rejected");

  return FALSE;

  }

return TRUE;