text: /* crypto/engine/eng_dyn.c */
  /* Written by Geoff Thorpe (geoff@geoffthorpe.net) for the OpenSSL
   * project 2001.
   */
  /* ====================================================================
   * Copyright (c) 1999-2001 The OpenSSL Project.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer. 
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. All advertising materials mentioning features or use of this
   *    software must display the following acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
   *
   * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For written permission, please contact
   *    licensing@OpenSSL.org.
   *
   * 5. Products derived from this software may not be called "OpenSSL"
   *    nor may "OpenSSL" appear in their names without prior written
   *    permission of the OpenSSL Project.
   *
   * 6. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
   *
   * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
   * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   * ====================================================================
   *
   * This product includes cryptographic software written by Eric Young
   * (eay@cryptsoft.com).  This product includes software written by Tim
   * Hudson (tjh@cryptsoft.com).
   *
   */
  
  
  #include "eng_int.h"
  #include <openssl/dso.h>
  
  /* Shared libraries implementing ENGINEs for use by the "dynamic" ENGINE loader
   * should implement the hook-up functions with the following prototypes. */
  
  /* Our ENGINE handlers */
  static int dynamic_init(ENGINE *e);
  static int dynamic_finish(ENGINE *e);
  static int dynamic_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void));
  /* Predeclare our context type */
  typedef struct st_dynamic_data_ctx dynamic_data_ctx;
  /* The implementation for the important control command */
  static int dynamic_load(ENGINE *e, dynamic_data_ctx *ctx);
  
  #define DYNAMIC_CMD_SO_PATH		ENGINE_CMD_BASE
  #define DYNAMIC_CMD_NO_VCHECK		(ENGINE_CMD_BASE + 1)
  #define DYNAMIC_CMD_ID			(ENGINE_CMD_BASE + 2)
  #define DYNAMIC_CMD_LIST_ADD		(ENGINE_CMD_BASE + 3)
  #define DYNAMIC_CMD_DIR_LOAD		(ENGINE_CMD_BASE + 4)
  #define DYNAMIC_CMD_DIR_ADD		(ENGINE_CMD_BASE + 5)
  #define DYNAMIC_CMD_LOAD		(ENGINE_CMD_BASE + 6)
  
  /* The constants used when creating the ENGINE */
  static const char *engine_dynamic_id = "dynamic";
  static const char *engine_dynamic_name = "Dynamic engine loading support";
  static const ENGINE_CMD_DEFN dynamic_cmd_defns[] = {
  	{DYNAMIC_CMD_SO_PATH,
  		"SO_PATH",
  		"Specifies the path to the new ENGINE shared library",
  		ENGINE_CMD_FLAG_STRING},
  	{DYNAMIC_CMD_NO_VCHECK,
  		"NO_VCHECK",
  		"Specifies to continue even if version checking fails (boolean)",
  		ENGINE_CMD_FLAG_NUMERIC},
  	{DYNAMIC_CMD_ID,
  		"ID",
  		"Specifies an ENGINE id name for loading",
  		ENGINE_CMD_FLAG_STRING},
  	{DYNAMIC_CMD_LIST_ADD,
  		"LIST_ADD",
  		"Whether to add a loaded ENGINE to the internal list (0=no,1=yes,2=mandatory)",
  		ENGINE_CMD_FLAG_NUMERIC},
  	{DYNAMIC_CMD_DIR_LOAD,
  		"DIR_LOAD",
  		"Specifies whether to load from 'DIR_ADD' directories (0=no,1=yes,2=mandatory)",
  		ENGINE_CMD_FLAG_NUMERIC},
  	{DYNAMIC_CMD_DIR_ADD,
  		"DIR_ADD",
  		"Adds a directory from which ENGINEs can be loaded",
  		ENGINE_CMD_FLAG_STRING},
  	{DYNAMIC_CMD_LOAD,
  		"LOAD",
  		"Load up the ENGINE specified by other settings",
  		ENGINE_CMD_FLAG_NO_INPUT},
  	{0, NULL, NULL, 0}
  	};
  
  /* Loading code stores state inside the ENGINE structure via the "ex_data"
   * element. We load all our state into a single structure and use that as a
   * single context in the "ex_data" stack. */
  struct st_dynamic_data_ctx
  	{
  	/* The DSO object we load that supplies the ENGINE code */
  	DSO *dynamic_dso;
  	/* The function pointer to the version checking shared library function */
  	dynamic_v_check_fn v_check;
  	/* The function pointer to the engine-binding shared library function */
  	dynamic_bind_engine bind_engine;
  	/* The default name/path for loading the shared library */
  	const char *DYNAMIC_LIBNAME;
  	/* Whether to continue loading on a version check failure */
  	int no_vcheck;
  	/* If non-NULL, stipulates the 'id' of the ENGINE to be loaded */
  	const char *engine_id;
  	/* If non-zero, a successfully loaded ENGINE should be added to the internal
  	 * ENGINE list. If 2, the add must succeed or the entire load should fail. */
  	int list_add_value;
  	/* The symbol name for the version checking function */
  	const char *DYNAMIC_F1;
  	/* The symbol name for the "initialise ENGINE structure" function */
  	const char *DYNAMIC_F2;
  	/* Whether to never use 'dirs', use 'dirs' as a fallback, or only use
  	 * 'dirs' for loading. Default is to use 'dirs' as a fallback. */
  	int dir_load;
  	/* A stack of directories from which ENGINEs could be loaded */
  	STACK_OF(OPENSSL_STRING) *dirs;
  	};
  
  /* This is the "ex_data" index we obtain and reserve for use with our context
   * structure. */
  static int dynamic_ex_data_idx = -1;
  
  static void int_free_str(char *s) { OPENSSL_free(s); }
  /* Because our ex_data element may or may not get allocated depending on whether
   * a "first-use" occurs before the ENGINE is freed, we have a memory leak
   * problem to solve. We can't declare a "new" handler for the ex_data as we
   * don't want a dynamic_data_ctx in *all* ENGINE structures of all types (this
   * is a bug in the design of CRYPTO_EX_DATA). As such, we just declare a "free"
   * handler and that will get called if an ENGINE is being destroyed and there
   * was an ex_data element corresponding to our context type. */
  static void dynamic_data_ctx_free_func(void *parent, void *ptr,
  			CRYPTO_EX_DATA *ad, int idx, long argl, void *argp)
  	{
  	if(ptr)
  		{
  		dynamic_data_ctx *ctx = (dynamic_data_ctx *)ptr;
  		if(ctx->dynamic_dso)
  			DSO_free(ctx->dynamic_dso);
  		if(ctx->DYNAMIC_LIBNAME)
  			OPENSSL_free((void*)ctx->DYNAMIC_LIBNAME);
  		if(ctx->engine_id)
  			OPENSSL_free((void*)ctx->engine_id);
  		if(ctx->dirs)
  			sk_OPENSSL_STRING_pop_free(ctx->dirs, int_free_str);
  		OPENSSL_free(ctx);
  		}
  	}
  
  /* Construct the per-ENGINE context. We create it blindly and then use a lock to
   * check for a race - if so, all but one of the threads "racing" will have
   * wasted their time. The alternative involves creating everything inside the
   * lock which is far worse. */
  static int dynamic_set_data_ctx(ENGINE *e, dynamic_data_ctx **ctx)
  	{
  	dynamic_data_ctx *c;
  	c = OPENSSL_malloc(sizeof(dynamic_data_ctx));
  	if(!c)
  		{
  		ENGINEerr(ENGINE_F_DYNAMIC_SET_DATA_CTX,ERR_R_MALLOC_FAILURE);
  		return 0;
  		}
  	memset(c, 0, sizeof(dynamic_data_ctx));
  	c->dynamic_dso = NULL;
  	c->v_check = NULL;
  	c->bind_engine = NULL;
  	c->DYNAMIC_LIBNAME = NULL;
  	c->no_vcheck = 0;
  	c->engine_id = NULL;
  	c->list_add_value = 0;
  	c->DYNAMIC_F1 = "v_check";
  	c->DYNAMIC_F2 = "bind_engine";
  	c->dir_load = 1;
  	c->dirs = sk_OPENSSL_STRING_new_null();
  	if(!c->dirs)
  		{
  		ENGINEerr(ENGINE_F_DYNAMIC_SET_DATA_CTX,ERR_R_MALLOC_FAILURE);
  		OPENSSL_free(c);
  		return 0;
  		}
  	CRYPTO_w_lock(CRYPTO_LOCK_ENGINE);
  	if((*ctx = (dynamic_data_ctx *)ENGINE_get_ex_data(e,
  				dynamic_ex_data_idx)) == NULL)
  		{
  		/* Good, we're the first */
  		ENGINE_set_ex_data(e, dynamic_ex_data_idx, c);
  		*ctx = c;
  		c = NULL;
  		}
  	CRYPTO_w_unlock(CRYPTO_LOCK_ENGINE);
  	/* If we lost the race to set the context, c is non-NULL and *ctx is the
  	 * context of the thread that won. */
  	if(c)
  		OPENSSL_free(c);
  	return 1;
  	}
  
  /* This function retrieves the context structure from an ENGINE's "ex_data", or
   * if it doesn't exist yet, sets it up. */
  static dynamic_data_ctx *dynamic_get_data_ctx(ENGINE *e)
  	{
  	dynamic_data_ctx *ctx;
  	if(dynamic_ex_data_idx < 0)
  		{
  		/* Create and register the ENGINE ex_data, and associate our
  		 * "free" function with it to ensure any allocated contexts get
  		 * freed when an ENGINE goes underground. */
  		int new_idx = ENGINE_get_ex_new_index(0, NULL, NULL, NULL,
  					dynamic_data_ctx_free_func);
  		if(new_idx == -1)
  			{
  			ENGINEerr(ENGINE_F_DYNAMIC_GET_DATA_CTX,ENGINE_R_NO_INDEX);
  			return NULL;
  			}
  		CRYPTO_w_lock(CRYPTO_LOCK_ENGINE);
  		/* Avoid a race by checking again inside this lock */
  		if(dynamic_ex_data_idx < 0)
  			{
  			/* Good, someone didn't beat us to it */
  			dynamic_ex_data_idx = new_idx;
  			new_idx = -1;
  			}
  		CRYPTO_w_unlock(CRYPTO_LOCK_ENGINE);
  		/* In theory we could "give back" the index here if
  		 * (new_idx>-1), but it's not possible and wouldn't gain us much
  		 * if it were. */
  		}
  	ctx = (dynamic_data_ctx *)ENGINE_get_ex_data(e, dynamic_ex_data_idx);
  	/* Check if the context needs to be created */
  	if((ctx == NULL) && !dynamic_set_data_ctx(e, &ctx))
  		/* "set_data" will set errors if necessary */
  		return NULL;
  	return ctx;
  	}
  
  static ENGINE *engine_dynamic(void)
  	{
  	ENGINE *ret = ENGINE_new();
  	if(!ret)
  		return NULL;
  	if(!ENGINE_set_id(ret, engine_dynamic_id) ||
  			!ENGINE_set_name(ret, engine_dynamic_name) ||
  			!ENGINE_set_init_function(ret, dynamic_init) ||
  			!ENGINE_set_finish_function(ret, dynamic_finish) ||
  			!ENGINE_set_ctrl_function(ret, dynamic_ctrl) ||
  			!ENGINE_set_flags(ret, ENGINE_FLAGS_BY_ID_COPY) ||
  			!ENGINE_set_cmd_defns(ret, dynamic_cmd_defns))
  		{
  		ENGINE_free(ret);
  		return NULL;
  		}
  	return ret;
  	}
  
  void ENGINE_load_dynamic(void)
  	{
  	ENGINE *toadd = engine_dynamic();
  	if(!toadd) return;
  	ENGINE_add(toadd);
  	/* If the "add" worked, it gets a structural reference. So either way,
  	 * we release our just-created reference. */
  	ENGINE_free(toadd);
  	/* If the "add" didn't work, it was probably a conflict because it was
  	 * already added (eg. someone calling ENGINE_load_blah then calling
  	 * ENGINE_load_builtin_engines() perhaps). */
  	ERR_clear_error();
  	}
  
  static int dynamic_init(ENGINE *e)
  	{
  	/* We always return failure - the "dyanamic" engine itself can't be used
  	 * for anything. */
  	return 0;
  	}
  
  static int dynamic_finish(ENGINE *e)
  	{
  	/* This should never be called on account of "dynamic_init" always
  	 * failing. */
  	return 0;
  	}
  
  static int dynamic_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void))
  	{
  	dynamic_data_ctx *ctx = dynamic_get_data_ctx(e);
  	int initialised;
  	
  	if(!ctx)
  		{
  		ENGINEerr(ENGINE_F_DYNAMIC_CTRL,ENGINE_R_NOT_LOADED);
  		return 0;
  		}
  	initialised = ((ctx->dynamic_dso == NULL) ? 0 : 1);
  	/* All our control commands require the ENGINE to be uninitialised */
  	if(initialised)
  		{
  		ENGINEerr(ENGINE_F_DYNAMIC_CTRL,
  			ENGINE_R_ALREADY_LOADED);
  		return 0;
  		}
  	switch(cmd)
  		{
  	case DYNAMIC_CMD_SO_PATH:
  		/* a NULL 'p' or a string of zero-length is the same thing */
  		if(p && (strlen((const char *)p) < 1))
  			p = NULL;
  		if(ctx->DYNAMIC_LIBNAME)
  			OPENSSL_free((void*)ctx->DYNAMIC_LIBNAME);
  		if(p)
  			ctx->DYNAMIC_LIBNAME = BUF_strdup(p);
  		else
  			ctx->DYNAMIC_LIBNAME = NULL;
  		return (ctx->DYNAMIC_LIBNAME ? 1 : 0);
  	case DYNAMIC_CMD_NO_VCHECK:
  		ctx->no_vcheck = ((i == 0) ? 0 : 1);
  		return 1;
  	case DYNAMIC_CMD_ID:
  		/* a NULL 'p' or a string of zero-length is the same thing */
  		if(p && (strlen((const char *)p) < 1))
  			p = NULL;
  		if(ctx->engine_id)
  			OPENSSL_free((void*)ctx->engine_id);
  		if(p)
  			ctx->engine_id = BUF_strdup(p);
  		else
  			ctx->engine_id = NULL;
  		return (ctx->engine_id ? 1 : 0);
  	case DYNAMIC_CMD_LIST_ADD:
  		if((i < 0) || (i > 2))
  			{
  			ENGINEerr(ENGINE_F_DYNAMIC_CTRL,
  				ENGINE_R_INVALID_ARGUMENT);
  			return 0;
  			}
  		ctx->list_add_value = (int)i;
  		return 1;
  	case DYNAMIC_CMD_LOAD:
  		return dynamic_load(e, ctx);
  	case DYNAMIC_CMD_DIR_LOAD:
  		if((i < 0) || (i > 2))
  			{
  			ENGINEerr(ENGINE_F_DYNAMIC_CTRL,
  				ENGINE_R_INVALID_ARGUMENT);
  			return 0;
  			}
  		ctx->dir_load = (int)i;
  		return 1;
  	case DYNAMIC_CMD_DIR_ADD:
  		/* a NULL 'p' or a string of zero-length is the same thing */
  		if(!p || (strlen((const char *)p) < 1))
  			{
  			ENGINEerr(ENGINE_F_DYNAMIC_CTRL,
  				ENGINE_R_INVALID_ARGUMENT);
  			return 0;
  			}
  		{
  		char *tmp_str = BUF_strdup(p);
  		if(!tmp_str)
  			{
  			ENGINEerr(ENGINE_F_DYNAMIC_CTRL,
  				ERR_R_MALLOC_FAILURE);
  			return 0;
  			}
  		sk_OPENSSL_STRING_insert(ctx->dirs, tmp_str, -1);
  		}
  		return 1;
  	default:
  		break;
  		}
  	ENGINEerr(ENGINE_F_DYNAMIC_CTRL,ENGINE_R_CTRL_COMMAND_NOT_IMPLEMENTED);
  	return 0;
  	}
  
  static int int_load(dynamic_data_ctx *ctx)
  	{
  	int num, loop;
  	/* Unless told not to, try a direct load */
  	if((ctx->dir_load != 2) && (DSO_load(ctx->dynamic_dso,
  				ctx->DYNAMIC_LIBNAME, NULL, 0) != NULL))
  		return 1;
  	/* If we're not allowed to use 'dirs' or we have none, fail */
  	if(!ctx->dir_load || (num = sk_OPENSSL_STRING_num(ctx->dirs)) < 1)
  		return 0;
  	for(loop = 0; loop < num; loop++)
  		{
  		const char *s = sk_OPENSSL_STRING_value(ctx->dirs, loop);
  		char *merge = DSO_merge(ctx->dynamic_dso, ctx->DYNAMIC_LIBNAME, s);
  		if(!merge)
  			return 0;
  		if(DSO_load(ctx->dynamic_dso, merge, NULL, 0))
  			{
  			/* Found what we're looking for */
  			OPENSSL_free(merge);
  			/* Previous failed loop iterations, if any, will have resulted in
  			 * errors. Clear them out before returning success. */
  			ERR_clear_error();
  			return 1;
  			}
  		OPENSSL_free(merge);
  		}
  	return 0;
  	}
  
  static int dynamic_load(ENGINE *e, dynamic_data_ctx *ctx)
  	{
  	ENGINE cpy;
  	dynamic_fns fns;
  
  	if(!ctx->dynamic_dso)
  		ctx->dynamic_dso = DSO_new();
  	if(!ctx->DYNAMIC_LIBNAME)
  		{
  		if(!ctx->engine_id)
  			return 0;
  		ctx->DYNAMIC_LIBNAME =
  			DSO_convert_filename(ctx->dynamic_dso, ctx->engine_id);
  		}
  	if(!int_load(ctx))
  		{
  		ENGINEerr(ENGINE_F_DYNAMIC_LOAD,
  			ENGINE_R_DSO_NOT_FOUND);
  		DSO_free(ctx->dynamic_dso);
  		ctx->dynamic_dso = NULL;
  		return 0;
  		}
  	/* We have to find a bind function otherwise it'll always end badly */
  	if(!(ctx->bind_engine = (dynamic_bind_engine)DSO_bind_func(
  					ctx->dynamic_dso, ctx->DYNAMIC_F2)))
  		{
  		ctx->bind_engine = NULL;
  		DSO_free(ctx->dynamic_dso);
  		ctx->dynamic_dso = NULL;
  		ENGINEerr(ENGINE_F_DYNAMIC_LOAD,
  			ENGINE_R_DSO_FAILURE);
  		return 0;
  		}
  	/* Do we perform version checking? */
  	if(!ctx->no_vcheck)
  		{
  		unsigned long vcheck_res = 0;
  		/* Now we try to find a version checking function and decide how
  		 * to cope with failure if/when it fails. */
  		ctx->v_check = (dynamic_v_check_fn)DSO_bind_func(
  				ctx->dynamic_dso, ctx->DYNAMIC_F1);
  		if(ctx->v_check)
  			vcheck_res = ctx->v_check(OSSL_DYNAMIC_VERSION);
  		/* We fail if the version checker veto'd the load *or* if it is
  		 * deferring to us (by returning its version) and we think it is
  		 * too old. */
  		if(vcheck_res < OSSL_DYNAMIC_OLDEST)
  			{
  			/* Fail */
  			ctx->bind_engine = NULL;
  			ctx->v_check = NULL;
  			DSO_free(ctx->dynamic_dso);
  			ctx->dynamic_dso = NULL;
  			ENGINEerr(ENGINE_F_DYNAMIC_LOAD,
  				ENGINE_R_VERSION_INCOMPATIBILITY);
  			return 0;
  			}
  		}
  	/* First binary copy the ENGINE structure so that we can roll back if
  	 * the hand-over fails */
  	memcpy(&cpy, e, sizeof(ENGINE));
  	/* Provide the ERR, "ex_data", memory, and locking callbacks so the
  	 * loaded library uses our state rather than its own. FIXME: As noted in
  	 * engine.h, much of this would be simplified if each area of code
  	 * provided its own "summary" structure of all related callbacks. It
  	 * would also increase opaqueness. */
  	fns.static_state = ENGINE_get_static_state();
  	fns.err_fns = ERR_get_implementation();
  	fns.ex_data_fns = CRYPTO_get_ex_data_implementation();
  	CRYPTO_get_mem_functions(&fns.mem_fns.malloc_cb,
  				&fns.mem_fns.realloc_cb,
  				&fns.mem_fns.free_cb);
  	fns.lock_fns.lock_locking_cb = CRYPTO_get_locking_callback();
  	fns.lock_fns.lock_add_lock_cb = CRYPTO_get_add_lock_callback();
  	fns.lock_fns.dynlock_create_cb = CRYPTO_get_dynlock_create_callback();
  	fns.lock_fns.dynlock_lock_cb = CRYPTO_get_dynlock_lock_callback();
  	fns.lock_fns.dynlock_destroy_cb = CRYPTO_get_dynlock_destroy_callback();
  	/* Now that we've loaded the dynamic engine, make sure no "dynamic"
  	 * ENGINE elements will show through. */
  	engine_set_all_null(e);
  
  	/* Try to bind the ENGINE onto our own ENGINE structure */
  	if(!ctx->bind_engine(e, ctx->engine_id, &fns))
  		{
  		ctx->bind_engine = NULL;
  		ctx->v_check = NULL;
  		DSO_free(ctx->dynamic_dso);
  		ctx->dynamic_dso = NULL;
  		ENGINEerr(ENGINE_F_DYNAMIC_LOAD,ENGINE_R_INIT_FAILED);
  		/* Copy the original ENGINE structure back */
  		memcpy(e, &cpy, sizeof(ENGINE));
  		return 0;
  		}
  	/* Do we try to add this ENGINE to the internal list too? */
  	if(ctx->list_add_value > 0)
  		{
  		if(!ENGINE_add(e))
  			{
  			/* Do we tolerate this or fail? */
  			if(ctx->list_add_value > 1)
  				{
  				/* Fail - NB: By this time, it's too late to
  				 * rollback, and trying to do so allows the
  				 * bind_engine() code to have created leaks. We
  				 * just have to fail where we are, after the
  				 * ENGINE has changed. */
  				ENGINEerr(ENGINE_F_DYNAMIC_LOAD,
  					ENGINE_R_CONFLICTING_ENGINE_ID);
  				return 0;
  				}
  			/* Tolerate */
  			ERR_clear_error();
  			}
  		}
  	return 1;
  	}
  