New upstream version 2.4~beta1upstream/2.4_beta1

1 files changed, 827 insertions, 0 deletions

diff --git a/include/openvpn-plugin.h.in b/include/openvpn-plugin.h.in
new file mode 100644
index 0000000..34ad18b
--- /dev/null
+++ b/include/openvpn-plugin.h.in
@@ -0,0 +1,827 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  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 (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef OPENVPN_PLUGIN_H_
+#define OPENVPN_PLUGIN_H_
+
+#define OPENVPN_PLUGIN_VERSION 3
+
+#ifdef ENABLE_CRYPTO
+#ifdef ENABLE_CRYPTO_MBEDTLS
+#include <mbedtls/x509_crt.h>
+#ifndef __OPENVPN_X509_CERT_T_DECLARED
+#define __OPENVPN_X509_CERT_T_DECLARED
+typedef mbedtls_x509_crt openvpn_x509_cert_t;
+#endif
+#else
+#include <openssl/x509.h>
+#ifndef __OPENVPN_X509_CERT_T_DECLARED
+#define __OPENVPN_X509_CERT_T_DECLARED
+typedef X509 openvpn_x509_cert_t;
+#endif
+#endif
+#endif
+
+#include <stdarg.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Provide some basic version information to plug-ins at OpenVPN compile time
+ * This is will not be the complete version
+ */
+#define OPENVPN_VERSION_MAJOR @OPENVPN_VERSION_MAJOR@
+#define OPENVPN_VERSION_MINOR @OPENVPN_VERSION_MINOR@
+#define OPENVPN_VERSION_PATCH "@OPENVPN_VERSION_PATCH@"
+
+/*
+ * Plug-in types.  These types correspond to the set of script callbacks
+ * supported by OpenVPN.
+ *
+ * This is the general call sequence to expect when running in server mode:
+ *
+ * Initial Server Startup:
+ *
+ * FUNC: openvpn_plugin_open_v1
+ * FUNC: openvpn_plugin_client_constructor_v1 (this is the top-level "generic"
+ *                                             client template)
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_UP
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_ROUTE_UP
+ *
+ * New Client Connection:
+ *
+ * FUNC: openvpn_plugin_client_constructor_v1
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_ENABLE_PF
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_TLS_VERIFY (called once for every cert
+ *                                                     in the server chain)
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_TLS_FINAL
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_IPCHANGE
+ *
+ * [If OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY returned OPENVPN_PLUGIN_FUNC_DEFERRED,
+ * we don't proceed until authentication is verified via auth_control_file]
+ *
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_CLIENT_CONNECT_V2
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_LEARN_ADDRESS
+ * 
+ * [Client session ensues]
+ *
+ * For each "TLS soft reset", according to reneg-sec option (or similar):
+ *
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_ENABLE_PF
+ *
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_TLS_VERIFY (called once for every cert
+ *                                                     in the server chain)
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_TLS_FINAL
+ * 
+ * [If OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY returned OPENVPN_PLUGIN_FUNC_DEFERRED,
+ * we expect that authentication is verified via auth_control_file within
+ * the number of seconds defined by the "hand-window" option.  Data channel traffic
+ * will continue to flow uninterrupted during this period.]
+ *
+ * [Client session continues]
+ *
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_CLIENT_DISCONNECT
+ * FUNC: openvpn_plugin_client_destructor_v1
+ *
+ * [ some time may pass ]
+ *
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_LEARN_ADDRESS (this coincides with a
+ *                                                            lazy free of initial
+ *                                                            learned addr object)
+ * Server Shutdown:
+ *
+ * FUNC: openvpn_plugin_func_v1 OPENVPN_PLUGIN_DOWN
+ * FUNC: openvpn_plugin_client_destructor_v1 (top-level "generic" client)
+ * FUNC: openvpn_plugin_close_v1
+ */
+#define OPENVPN_PLUGIN_UP                    0
+#define OPENVPN_PLUGIN_DOWN                  1
+#define OPENVPN_PLUGIN_ROUTE_UP              2
+#define OPENVPN_PLUGIN_IPCHANGE              3
+#define OPENVPN_PLUGIN_TLS_VERIFY            4
+#define OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY 5
+#define OPENVPN_PLUGIN_CLIENT_CONNECT        6
+#define OPENVPN_PLUGIN_CLIENT_DISCONNECT     7
+#define OPENVPN_PLUGIN_LEARN_ADDRESS         8
+#define OPENVPN_PLUGIN_CLIENT_CONNECT_V2     9
+#define OPENVPN_PLUGIN_TLS_FINAL             10
+#define OPENVPN_PLUGIN_ENABLE_PF             11
+#define OPENVPN_PLUGIN_ROUTE_PREDOWN         12
+#define OPENVPN_PLUGIN_N                     13
+
+/*
+ * Build a mask out of a set of plug-in types.
+ */
+#define OPENVPN_PLUGIN_MASK(x) (1<<(x))
+
+/*
+ * A pointer to a plugin-defined object which contains
+ * the object state.
+ */
+typedef void *openvpn_plugin_handle_t;
+
+/*
+ * Return value for openvpn_plugin_func_v1 function
+ */
+#define OPENVPN_PLUGIN_FUNC_SUCCESS  0
+#define OPENVPN_PLUGIN_FUNC_ERROR    1
+#define OPENVPN_PLUGIN_FUNC_DEFERRED 2
+
+/*
+ * For Windows (needs to be modified for MSVC)
+ */
+#if defined(_WIN32) && !defined(OPENVPN_PLUGIN_H)
+# define OPENVPN_EXPORT __declspec(dllexport)
+#else
+# define OPENVPN_EXPORT
+#endif
+
+/*
+ * If OPENVPN_PLUGIN_H is defined, we know that we are being
+ * included in an OpenVPN compile, rather than a plugin compile.
+ */
+#ifdef OPENVPN_PLUGIN_H
+
+/*
+ * We are compiling OpenVPN.
+ */
+#define OPENVPN_PLUGIN_DEF        typedef
+#define OPENVPN_PLUGIN_FUNC(name) (*name)
+
+#else
+
+/*
+ * We are compiling plugin.
+ */
+#define OPENVPN_PLUGIN_DEF        OPENVPN_EXPORT
+#define OPENVPN_PLUGIN_FUNC(name) name
+
+#endif
+
+/*
+ * Used by openvpn_plugin_func to return structured
+ * data.  The plugin should allocate all structure
+ * instances, name strings, and value strings with
+ * malloc, since OpenVPN will assume that it
+ * can free the list by calling free() over the same.
+ */
+struct openvpn_plugin_string_list
+{
+  struct openvpn_plugin_string_list *next;
+  char *name;
+  char *value;
+};
+
+
+/* openvpn_plugin_{open,func}_v3() related structs */
+
+/* Defines version of the v3 plugin argument structs
+ *
+ * Whenever one or more of these structs are modified, this constant
+ * must be updated.  A changelog should be appended in this comment
+ * as well, to make it easier to see what information is available
+ * in the different versions.
+ *
+ * Version   Comment
+ *    1      Initial plugin v3 structures providing the same API as
+ *           the v2 plugin interface, X509 certificate information +
+ *           a logging API for plug-ins.
+ *
+ *    2      Added ssl_api member in struct openvpn_plugin_args_open_in
+ *           which identifies the SSL implementation OpenVPN is compiled
+ *           against.
+ *
+ *    3      Added ovpn_version, ovpn_version_major, ovpn_version_minor
+ *           and ovpn_version_patch to provide the runtime version of
+ *           OpenVPN to plug-ins.
+ */
+#define OPENVPN_PLUGINv3_STRUCTVER 3
+
+/**
+ * Definitions needed for the plug-in callback functions.
+ */
+typedef enum
+{
+  PLOG_ERR    = (1 << 0),  /* Error condition message */
+  PLOG_WARN   = (1 << 1),  /* General warning message */
+  PLOG_NOTE   = (1 << 2),  /* Informational message */
+  PLOG_DEBUG  = (1 << 3),  /* Debug message, displayed if verb >= 7 */
+
+  PLOG_ERRNO  = (1 << 8),  /* Add error description to message */
+  PLOG_NOMUTE = (1 << 9),  /* Mute setting does not apply for message */
+
+} openvpn_plugin_log_flags_t;
+
+
+#ifdef __GNUC__
+#if __USE_MINGW_ANSI_STDIO
+#  define _ovpn_chk_fmt(a, b) __attribute__ ((format(gnu_printf, (a), (b))))
+#else
+#  define _ovpn_chk_fmt(a, b) __attribute__ ((format(__printf__, (a), (b))))
+#endif
+#else
+#  define _ovpn_chk_fmt(a, b)
+#endif
+
+typedef void (*plugin_log_t) (openvpn_plugin_log_flags_t flags,
+                              const char *plugin_name,
+                              const char *format, ...) _ovpn_chk_fmt(3, 4);
+
+typedef void (*plugin_vlog_t) (openvpn_plugin_log_flags_t flags,
+                               const char *plugin_name,
+                               const char *format,
+                               va_list arglist) _ovpn_chk_fmt(3, 0);
+
+#undef _ovpn_chk_fmt
+
+/**
+ * Used by the openvpn_plugin_open_v3() function to pass callback
+ * function pointers to the plug-in.
+ *
+ * plugin_log
+ * plugin_vlog : Use these functions to add information to the OpenVPN log file.
+ *               Messages will only be displayed if the plugin_name parameter
+ *               is set. PLOG_DEBUG messages will only be displayed with plug-in
+ *               debug log verbosity (at the time of writing that's verb >= 7).
+ */
+struct openvpn_plugin_callbacks
+{
+  plugin_log_t    plugin_log;
+  plugin_vlog_t   plugin_vlog;
+};
+
+/**
+ * Used by the openvpn_plugin_open_v3() function to indicate to the
+ * plug-in what kind of SSL implementation OpenVPN uses.  This is
+ * to avoid SEGV issues when OpenVPN is complied against mbed TLS
+ * and the plug-in against OpenSSL.
+ */
+typedef enum {
+  SSLAPI_NONE,
+  SSLAPI_OPENSSL,
+  SSLAPI_MBEDTLS
+} ovpnSSLAPI;
+
+/**
+ * Arguments used to transport variables to the plug-in.
+ * The struct openvpn_plugin_args_open_in is only used
+ * by the openvpn_plugin_open_v3() function.
+ *
+ * STRUCT MEMBERS
+ *
+ * type_mask : Set by OpenVPN to the logical OR of all script
+ *             types which this version of OpenVPN supports.
+ *
+ * argv : a NULL-terminated array of options provided to the OpenVPN
+ *        "plug-in" directive.  argv[0] is the dynamic library pathname.
+ *
+ * envp : a NULL-terminated array of OpenVPN-set environmental
+ *        variables in "name=value" format.  Note that for security reasons,
+ *        these variables are not actually written to the "official"
+ *        environmental variable store of the process.
+ *
+ * callbacks : a pointer to the plug-in callback function struct.
+ *
+ */
+struct openvpn_plugin_args_open_in
+{
+  const int type_mask;
+  const char ** const argv;
+  const char ** const envp;
+  struct openvpn_plugin_callbacks *callbacks;
+  const ovpnSSLAPI ssl_api;
+  const char *ovpn_version;
+  const unsigned int ovpn_version_major;
+  const unsigned int ovpn_version_minor;
+  const char * const ovpn_version_patch;
+};
+
+
+/**
+ * Arguments used to transport variables from the plug-in back
+ * to the OpenVPN process.  The struct openvpn_plugin_args_open_return
+ * is only used by the openvpn_plugin_open_v3() function.
+ *
+ * STRUCT MEMBERS
+ *
+ * *type_mask : The plug-in should set this value to the logical OR of all script
+ *              types which the plug-in wants to intercept.  For example, if the
+ *              script wants to intercept the client-connect and client-disconnect
+ *              script types:
+ *
+ *              *type_mask = OPENVPN_PLUGIN_MASK(OPENVPN_PLUGIN_CLIENT_CONNECT)
+ *                         | OPENVPN_PLUGIN_MASK(OPENVPN_PLUGIN_CLIENT_DISCONNECT)
+ *
+ * *handle :    Pointer to a global plug-in context, created by the plug-in.  This pointer
+ *              is passed on to the other plug-in calls.
+ *
+ * return_list : used to return data back to OpenVPN.
+ *
+ */
+struct openvpn_plugin_args_open_return
+{
+  int  type_mask;
+  openvpn_plugin_handle_t *handle;
+  struct openvpn_plugin_string_list **return_list;
+};
+
+/**
+ * Arguments used to transport variables to and from the
+ * plug-in.  The struct openvpn_plugin_args_func is only used
+ * by the openvpn_plugin_func_v3() function.
+ *
+ * STRUCT MEMBERS:
+ *
+ * type : one of the PLUGIN_x types.
+ *
+ * argv : a NULL-terminated array of "command line" options which
+ *        would normally be passed to the script.  argv[0] is the dynamic
+ *        library pathname.
+ *
+ * envp : a NULL-terminated array of OpenVPN-set environmental
+ *        variables in "name=value" format.  Note that for security reasons,
+ *        these variables are not actually written to the "official"
+ *        environmental variable store of the process.
+ *
+ * *handle : Pointer to a global plug-in context, created by the plug-in's openvpn_plugin_open_v3().
+ *
+ * *per_client_context : the per-client context pointer which was returned by
+ *        openvpn_plugin_client_constructor_v1, if defined.
+ *
+ * current_cert_depth : Certificate depth of the certificate being passed over (only if compiled with ENABLE_CRYPTO defined)
+ *
+ * *current_cert : X509 Certificate object received from the client (only if compiled with ENABLE_CRYPTO defined)
+ *
+ */
+struct openvpn_plugin_args_func_in
+{
+  const int type;
+  const char ** const argv;
+  const char ** const envp;
+  openvpn_plugin_handle_t handle;
+  void *per_client_context;
+#ifdef ENABLE_CRYPTO
+  int current_cert_depth;
+  openvpn_x509_cert_t *current_cert;
+#else
+  int __current_cert_depth_disabled; /* Unused, for compatibility purposes only */
+  void *__current_cert_disabled; /* Unused, for compatibility purposes only */
+#endif
+};
+
+
+/**
+ * Arguments used to transport variables to and from the
+ * plug-in.  The struct openvpn_plugin_args_func is only used
+ * by the openvpn_plugin_func_v3() function.
+ *
+ * STRUCT MEMBERS:
+ *
+ * return_list : used to return data back to OpenVPN for further processing/usage by
+ *               the OpenVPN executable.
+ *
+ */
+struct openvpn_plugin_args_func_return
+{
+  struct openvpn_plugin_string_list **return_list;
+};
+
+/*
+ * Multiple plugin modules can be cascaded, and modules can be
+ * used in tandem with scripts.  The order of operation is that
+ * the module func() functions are called in the order that
+ * the modules were specified in the config file.  If a script
+ * was specified as well, it will be called last.  If the
+ * return code of the module/script controls an authentication
+ * function (such as tls-verify or auth-user-pass-verify), then
+ * every module and script must return success (0) in order for
+ * the connection to be authenticated.
+ *
+ * Notes:
+ *
+ * Plugins which use a privilege-separation model (by forking in
+ * their initialization function before the main OpenVPN process
+ * downgrades root privileges and/or executes a chroot) must
+ * daemonize after a fork if the "daemon" environmental variable is
+ * set.  In addition, if the "daemon_log_redirect" variable is set,
+ * the plugin should preserve stdout/stderr across the daemon()
+ * syscall.  See the daemonize() function in plugin/auth-pam/auth-pam.c
+ * for an example.
+ */
+
+/*
+ * Prototypes for functions which OpenVPN plug-ins must define.
+ */
+
+/*
+ * FUNCTION: openvpn_plugin_open_v2
+ *
+ * REQUIRED: YES
+ * 
+ * Called on initial plug-in load.  OpenVPN will preserve plug-in state
+ * across SIGUSR1 restarts but not across SIGHUP restarts.  A SIGHUP reset
+ * will cause the plugin to be closed and reopened.
+ *
+ * ARGUMENTS
+ *
+ * *type_mask : Set by OpenVPN to the logical OR of all script
+ *              types which this version of OpenVPN supports.  The plug-in
+ *              should set this value to the logical OR of all script types
+ *              which the plug-in wants to intercept.  For example, if the
+ *              script wants to intercept the client-connect and
+ *              client-disconnect script types:
+ *
+ *              *type_mask = OPENVPN_PLUGIN_MASK(OPENVPN_PLUGIN_CLIENT_CONNECT)
+ *                         | OPENVPN_PLUGIN_MASK(OPENVPN_PLUGIN_CLIENT_DISCONNECT)
+ *
+ * argv : a NULL-terminated array of options provided to the OpenVPN
+ *        "plug-in" directive.  argv[0] is the dynamic library pathname.
+ *
+ * envp : a NULL-terminated array of OpenVPN-set environmental
+ *        variables in "name=value" format.  Note that for security reasons,
+ *        these variables are not actually written to the "official"
+ *        environmental variable store of the process.
+ *
+ * return_list : used to return data back to OpenVPN.
+ *
+ * RETURN VALUE
+ *
+ * An openvpn_plugin_handle_t value on success, NULL on failure
+ */
+OPENVPN_PLUGIN_DEF openvpn_plugin_handle_t OPENVPN_PLUGIN_FUNC(openvpn_plugin_open_v2)
+     (unsigned int *type_mask,
+      const char *argv[],
+      const char *envp[],
+      struct openvpn_plugin_string_list **return_list);
+
+/*
+ * FUNCTION: openvpn_plugin_func_v2
+ *
+ * Called to perform the work of a given script type.
+ *
+ * REQUIRED: YES
+ * 
+ * ARGUMENTS
+ *
+ * handle : the openvpn_plugin_handle_t value which was returned by
+ *          openvpn_plugin_open.
+ *
+ * type : one of the PLUGIN_x types
+ *
+ * argv : a NULL-terminated array of "command line" options which
+ *        would normally be passed to the script.  argv[0] is the dynamic
+ *        library pathname.
+ *
+ * envp : a NULL-terminated array of OpenVPN-set environmental
+ *        variables in "name=value" format.  Note that for security reasons,
+ *        these variables are not actually written to the "official"
+ *        environmental variable store of the process.
+ *
+ * per_client_context : the per-client context pointer which was returned by
+ *        openvpn_plugin_client_constructor_v1, if defined.
+ *
+ * return_list : used to return data back to OpenVPN.
+ *
+ * RETURN VALUE
+ *
+ * OPENVPN_PLUGIN_FUNC_SUCCESS on success, OPENVPN_PLUGIN_FUNC_ERROR on failure
+ *
+ * In addition, OPENVPN_PLUGIN_FUNC_DEFERRED may be returned by
+ * OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY.  This enables asynchronous
+ * authentication where the plugin (or one of its agents) may indicate
+ * authentication success/failure some number of seconds after the return
+ * of the OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY handler by writing a single
+ * char to the file named by auth_control_file in the environmental variable
+ * list (envp).
+ *
+ * first char of auth_control_file:
+ * '0' -- indicates auth failure
+ * '1' -- indicates auth success
+ *
+ * OpenVPN will delete the auth_control_file after it goes out of scope.
+ *
+ * If an OPENVPN_PLUGIN_ENABLE_PF handler is defined and returns success
+ * for a particular client instance, packet filtering will be enabled for that
+ * instance.  OpenVPN will then attempt to read the packet filter configuration
+ * from the temporary file named by the environmental variable pf_file.  This
+ * file may be generated asynchronously and may be dynamically updated during the
+ * client session, however the client will be blocked from sending or receiving
+ * VPN tunnel packets until the packet filter file has been generated.  OpenVPN
+ * will periodically test the packet filter file over the life of the client
+ * instance and reload when modified.  OpenVPN will delete the packet filter file
+ * when the client instance goes out of scope.
+ *
+ * Packet filter file grammar:
+ *
+ * [CLIENTS DROP|ACCEPT]
+ * {+|-}common_name1
+ * {+|-}common_name2
+ * . . .
+ * [SUBNETS DROP|ACCEPT]
+ * {+|-}subnet1
+ * {+|-}subnet2
+ * . . .
+ * [END]
+ *
+ * Subnet: IP-ADDRESS | IP-ADDRESS/NUM_NETWORK_BITS
+ *
+ * CLIENTS refers to the set of clients (by their common-name) which
+ * this instance is allowed ('+') to connect to, or is excluded ('-')
+ * from connecting to.  Note that in the case of client-to-client
+ * connections, such communication must be allowed by the packet filter
+ * configuration files of both clients.
+ *
+ * SUBNETS refers to IP addresses or IP address subnets which this
+ * instance may connect to ('+') or is excluded ('-') from connecting
+ * to.
+ *
+ * DROP or ACCEPT defines default policy when there is no explicit match
+ * for a common-name or subnet.  The [END] tag must exist.  A special
+ * purpose tag called [KILL] will immediately kill the client instance.
+ * A given client or subnet rule applies to both incoming and outgoing
+ * packets.
+ *
+ * See plugin/defer/simple.c for an example on using asynchronous
+ * authentication and client-specific packet filtering.
+ */
+OPENVPN_PLUGIN_DEF int OPENVPN_PLUGIN_FUNC(openvpn_plugin_func_v2)
+     (openvpn_plugin_handle_t handle,
+      const int type,
+      const char *argv[],
+      const char *envp[],
+      void *per_client_context,
+      struct openvpn_plugin_string_list **return_list);
+
+
+/*
+ * FUNCTION: openvpn_plugin_open_v3
+ *
+ * REQUIRED: YES
+ *
+ * Called on initial plug-in load.  OpenVPN will preserve plug-in state
+ * across SIGUSR1 restarts but not across SIGHUP restarts.  A SIGHUP reset
+ * will cause the plugin to be closed and reopened.
+ *
+ * ARGUMENTS
+ *
+ * version : fixed value, defines the API version of the OpenVPN plug-in API.  The plug-in
+ *	     should validate that this value is matching the OPENVPN_PLUGINv3_STRUCTVER
+ *	     value.
+ *
+ * arguments : Structure with all arguments available to the plug-in.
+ *
+ * retptr :    used to return data back to OpenVPN.
+ *
+ * RETURN VALUE
+ *
+ * OPENVPN_PLUGIN_FUNC_SUCCESS on success, OPENVPN_PLUGIN_FUNC_ERROR on failure
+ */
+OPENVPN_PLUGIN_DEF int OPENVPN_PLUGIN_FUNC(openvpn_plugin_open_v3)
+     (const int version,
+      struct openvpn_plugin_args_open_in const *arguments,
+      struct openvpn_plugin_args_open_return *retptr);
+
+/*
+ * FUNCTION: openvpn_plugin_func_v3
+ *
+ * Called to perform the work of a given script type.
+ *
+ * REQUIRED: YES
+ *
+ * ARGUMENTS
+ *
+ * version : fixed value, defines the API version of the OpenVPN plug-in API.  The plug-in
+ *           should validate that this value is matching the OPENVPN_PLUGIN_VERSION value.
+ *
+ * handle : the openvpn_plugin_handle_t value which was returned by
+ *          openvpn_plugin_open.
+ *
+ * return_list : used to return data back to OpenVPN.
+ *
+ * RETURN VALUE
+ *
+ * OPENVPN_PLUGIN_FUNC_SUCCESS on success, OPENVPN_PLUGIN_FUNC_ERROR on failure
+ *
+ * In addition, OPENVPN_PLUGIN_FUNC_DEFERRED may be returned by
+ * OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY.  This enables asynchronous
+ * authentication where the plugin (or one of its agents) may indicate
+ * authentication success/failure some number of seconds after the return
+ * of the OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY handler by writing a single
+ * char to the file named by auth_control_file in the environmental variable
+ * list (envp).
+ *
+ * first char of auth_control_file:
+ * '0' -- indicates auth failure
+ * '1' -- indicates auth success
+ *
+ * OpenVPN will delete the auth_control_file after it goes out of scope.
+ *
+ * If an OPENVPN_PLUGIN_ENABLE_PF handler is defined and returns success
+ * for a particular client instance, packet filtering will be enabled for that
+ * instance.  OpenVPN will then attempt to read the packet filter configuration
+ * from the temporary file named by the environmental variable pf_file.  This
+ * file may be generated asynchronously and may be dynamically updated during the
+ * client session, however the client will be blocked from sending or receiving
+ * VPN tunnel packets until the packet filter file has been generated.  OpenVPN
+ * will periodically test the packet filter file over the life of the client
+ * instance and reload when modified.  OpenVPN will delete the packet filter file
+ * when the client instance goes out of scope.
+ *
+ * Packet filter file grammar:
+ *
+ * [CLIENTS DROP|ACCEPT]
+ * {+|-}common_name1
+ * {+|-}common_name2
+ * . . .
+ * [SUBNETS DROP|ACCEPT]
+ * {+|-}subnet1
+ * {+|-}subnet2
+ * . . .
+ * [END]
+ *
+ * Subnet: IP-ADDRESS | IP-ADDRESS/NUM_NETWORK_BITS
+ *
+ * CLIENTS refers to the set of clients (by their common-name) which
+ * this instance is allowed ('+') to connect to, or is excluded ('-')
+ * from connecting to.  Note that in the case of client-to-client
+ * connections, such communication must be allowed by the packet filter
+ * configuration files of both clients.
+ *
+ * SUBNETS refers to IP addresses or IP address subnets which this
+ * instance may connect to ('+') or is excluded ('-') from connecting
+ * to.
+ *
+ * DROP or ACCEPT defines default policy when there is no explicit match
+ * for a common-name or subnet.  The [END] tag must exist.  A special
+ * purpose tag called [KILL] will immediately kill the client instance.
+ * A given client or subnet rule applies to both incoming and outgoing
+ * packets.
+ *
+ * See plugin/defer/simple.c for an example on using asynchronous
+ * authentication and client-specific packet filtering.
+ */
+OPENVPN_PLUGIN_DEF int OPENVPN_PLUGIN_FUNC(openvpn_plugin_func_v3)
+     (const int version,
+      struct openvpn_plugin_args_func_in const *arguments,
+      struct openvpn_plugin_args_func_return *retptr);
+
+/*
+ * FUNCTION: openvpn_plugin_close_v1
+ *
+ * REQUIRED: YES
+ * 
+ * ARGUMENTS
+ *
+ * handle : the openvpn_plugin_handle_t value which was returned by
+ *          openvpn_plugin_open.
+ *
+ * Called immediately prior to plug-in unload.
+ */
+OPENVPN_PLUGIN_DEF void OPENVPN_PLUGIN_FUNC(openvpn_plugin_close_v1)
+     (openvpn_plugin_handle_t handle);
+
+/*
+ * FUNCTION: openvpn_plugin_abort_v1
+ *
+ * REQUIRED: NO
+ * 
+ * ARGUMENTS
+ *
+ * handle : the openvpn_plugin_handle_t value which was returned by
+ *          openvpn_plugin_open.
+ *
+ * Called when OpenVPN is in the process of aborting due to a fatal error.
+ * Will only be called on an open context returned by a prior successful
+ * openvpn_plugin_open callback.
+ */
+OPENVPN_PLUGIN_DEF void OPENVPN_PLUGIN_FUNC(openvpn_plugin_abort_v1)
+     (openvpn_plugin_handle_t handle);
+
+/*
+ * FUNCTION: openvpn_plugin_client_constructor_v1
+ *
+ * Called to allocate a per-client memory region, which
+ * is then passed to the openvpn_plugin_func_v2 function.
+ * This function is called every time the OpenVPN server
+ * constructs a client instance object, which normally
+ * occurs when a session-initiating packet is received
+ * by a new client, even before the client has authenticated.
+ *
+ * This function should allocate the private memory needed
+ * by the plugin to track individual OpenVPN clients, and
+ * return a void * to this memory region.
+ *
+ * REQUIRED: NO
+ * 
+ * ARGUMENTS
+ *
+ * handle : the openvpn_plugin_handle_t value which was returned by
+ *          openvpn_plugin_open.
+ *
+ * RETURN VALUE
+ *
+ * void * pointer to plugin's private per-client memory region, or NULL
+ * if no memory region is required.
+ */
+OPENVPN_PLUGIN_DEF void * OPENVPN_PLUGIN_FUNC(openvpn_plugin_client_constructor_v1)
+     (openvpn_plugin_handle_t handle);
+
+/*
+ * FUNCTION: openvpn_plugin_client_destructor_v1
+ *
+ * This function is called on client instance object destruction.
+ *
+ * REQUIRED: NO
+ * 
+ * ARGUMENTS
+ *
+ * handle : the openvpn_plugin_handle_t value which was returned by
+ *          openvpn_plugin_open.
+ *
+ * per_client_context : the per-client context pointer which was returned by
+ *        openvpn_plugin_client_constructor_v1, if defined.
+ */
+OPENVPN_PLUGIN_DEF void OPENVPN_PLUGIN_FUNC(openvpn_plugin_client_destructor_v1)
+     (openvpn_plugin_handle_t handle, void *per_client_context);
+
+/*
+ * FUNCTION: openvpn_plugin_select_initialization_point_v1
+ *
+ * Several different points exist in OpenVPN's initialization sequence where
+ * the openvpn_plugin_open function can be called.  While the default is
+ * OPENVPN_PLUGIN_INIT_PRE_DAEMON, this function can be used to select a
+ * different initialization point.  For example, if your plugin needs to
+ * return configuration parameters to OpenVPN, use
+ * OPENVPN_PLUGIN_INIT_PRE_CONFIG_PARSE.
+ *
+ * REQUIRED: NO
+ * 
+ * RETURN VALUE:
+ *
+ * An OPENVPN_PLUGIN_INIT_x value.
+ */
+#define OPENVPN_PLUGIN_INIT_PRE_CONFIG_PARSE 1
+#define OPENVPN_PLUGIN_INIT_PRE_DAEMON       2 /* default */
+#define OPENVPN_PLUGIN_INIT_POST_DAEMON      3
+#define OPENVPN_PLUGIN_INIT_POST_UID_CHANGE  4
+
+OPENVPN_PLUGIN_DEF int OPENVPN_PLUGIN_FUNC(openvpn_plugin_select_initialization_point_v1)
+     (void);
+
+/*
+ * FUNCTION: openvpn_plugin_min_version_required_v1
+ *
+ * This function is called by OpenVPN to query the minimum
+   plugin interface version number required by the plugin.
+ *
+ * REQUIRED: NO
+ * 
+ * RETURN VALUE
+ *
+ * The minimum OpenVPN plugin interface version number necessary to support
+ * this plugin.
+ */
+OPENVPN_PLUGIN_DEF int OPENVPN_PLUGIN_FUNC(openvpn_plugin_min_version_required_v1)
+     (void);
+
+/*
+ * Deprecated functions which are still supported for backward compatibility.
+ */
+
+OPENVPN_PLUGIN_DEF openvpn_plugin_handle_t OPENVPN_PLUGIN_FUNC(openvpn_plugin_open_v1)
+     (unsigned int *type_mask,
+      const char *argv[],
+      const char *envp[]);
+
+OPENVPN_PLUGIN_DEF int OPENVPN_PLUGIN_FUNC(openvpn_plugin_func_v1)
+     (openvpn_plugin_handle_t handle, const int type, const char *argv[], const char *envp[]);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* OPENVPN_PLUGIN_H_ */