Move engine library over to using the new thread API
[openssl.git] / crypto / engine / eng_ctrl.c
index 5ce25d92ec9518508b9e7c3734bf1b59ae8fcc63..c912c1d913f57f85a1b7d2eb9b022d48dc711258 100644 (file)
@@ -1,4 +1,3 @@
-/* crypto/engine/eng_ctrl.c */
 /* ====================================================================
  * Copyright (c) 1999-2001 The OpenSSL Project.  All rights reserved.
  *
@@ -7,7 +6,7 @@
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer. 
+ *    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
 
 #include "eng_int.h"
 
-/* When querying a ENGINE-specific control command's 'description', this string
- * is used if the ENGINE_CMD_DEFN has cmd_desc set to NULL. */
+/*
+ * When querying a ENGINE-specific control command's 'description', this
+ * string is used if the ENGINE_CMD_DEFN has cmd_desc set to NULL.
+ */
 static const char *int_no_description = "";
 
-/* These internal functions handle 'CMD'-related control commands when the
+/*
+ * These internal functions handle 'CMD'-related control commands when the
  * ENGINE in question has asked us to take care of it (ie. the ENGINE did not
- * set the ENGINE_FLAGS_MANUAL_CMD_CTRL flag. */
+ * set the ENGINE_FLAGS_MANUAL_CMD_CTRL flag.
+ */
 
 static int int_ctrl_cmd_is_null(const ENGINE_CMD_DEFN *defn)
-       {
-       if((defn->cmd_num == 0) || (defn->cmd_name == NULL))
-               return 1;
-       return 0;
-       }
+{
+    if ((defn->cmd_num == 0) || (defn->cmd_name == NULL))
+        return 1;
+    return 0;
+}
 
 static int int_ctrl_cmd_by_name(const ENGINE_CMD_DEFN *defn, const char *s)
-       {
-       int idx = 0;
-       while(!int_ctrl_cmd_is_null(defn) && (strcmp(defn->cmd_name, s) != 0))
-               {
-               idx++;
-               defn++;
-               }
-       if(int_ctrl_cmd_is_null(defn))
-               /* The given name wasn't found */
-               return -1;
-       return idx;
-       }
+{
+    int idx = 0;
+    while (!int_ctrl_cmd_is_null(defn) && (strcmp(defn->cmd_name, s) != 0)) {
+        idx++;
+        defn++;
+    }
+    if (int_ctrl_cmd_is_null(defn))
+        /* The given name wasn't found */
+        return -1;
+    return idx;
+}
 
 static int int_ctrl_cmd_by_num(const ENGINE_CMD_DEFN *defn, unsigned int num)
-       {
-       int idx = 0;
-       /* NB: It is stipulated that 'cmd_defn' lists are ordered by cmd_num. So
-        * our searches don't need to take any longer than necessary. */
-       while(!int_ctrl_cmd_is_null(defn) && (defn->cmd_num < num))
-               {
-               idx++;
-               defn++;
-               }
-       if(defn->cmd_num == num)
-               return idx;
-       /* The given cmd_num wasn't found */
-       return -1;
-       }
+{
+    int idx = 0;
+    /*
+     * NB: It is stipulated that 'cmd_defn' lists are ordered by cmd_num. So
+     * our searches don't need to take any longer than necessary.
+     */
+    while (!int_ctrl_cmd_is_null(defn) && (defn->cmd_num < num)) {
+        idx++;
+        defn++;
+    }
+    if (defn->cmd_num == num)
+        return idx;
+    /* The given cmd_num wasn't found */
+    return -1;
+}
 
 static int int_ctrl_helper(ENGINE *e, int cmd, long i, void *p,
-                          void (*f)(void))
-       {
-       int idx;
-       char *s = (char *)p;
-       /* Take care of the easy one first (eg. it requires no searches) */
-       if(cmd == ENGINE_CTRL_GET_FIRST_CMD_TYPE)
-               {
-               if((e->cmd_defns == NULL) || int_ctrl_cmd_is_null(e->cmd_defns))
-                       return 0;
-               return e->cmd_defns->cmd_num;
-               }
-       /* One or two commands require that "p" be a valid string buffer */
-       if((cmd == ENGINE_CTRL_GET_CMD_FROM_NAME) ||
-                       (cmd == ENGINE_CTRL_GET_NAME_FROM_CMD) ||
-                       (cmd == ENGINE_CTRL_GET_DESC_FROM_CMD))
-               {
-               if(s == NULL)
-                       {
-                       ENGINEerr(ENGINE_F_INT_CTRL_HELPER,
-                               ERR_R_PASSED_NULL_PARAMETER);
-                       return -1;
-                       }
-               }
-       /* Now handle cmd_name -> cmd_num conversion */
-       if(cmd == ENGINE_CTRL_GET_CMD_FROM_NAME)
-               {
-               if((e->cmd_defns == NULL) || ((idx = int_ctrl_cmd_by_name(
-                                               e->cmd_defns, s)) < 0))
-                       {
-                       ENGINEerr(ENGINE_F_INT_CTRL_HELPER,
-                               ENGINE_R_INVALID_CMD_NAME);
-                       return -1;
-                       }
-               return e->cmd_defns[idx].cmd_num;
-               }
-       /* For the rest of the commands, the 'long' argument must specify a
-        * valie command number - so we need to conduct a search. */
-       if((e->cmd_defns == NULL) || ((idx = int_ctrl_cmd_by_num(e->cmd_defns,
-                                       (unsigned int)i)) < 0))
-               {
-               ENGINEerr(ENGINE_F_INT_CTRL_HELPER,
-                       ENGINE_R_INVALID_CMD_NUMBER);
-               return -1;
-               }
-       /* Now the logic splits depending on command type */
-       switch(cmd)
-               {
-       case ENGINE_CTRL_GET_NEXT_CMD_TYPE:
-               idx++;
-               if(int_ctrl_cmd_is_null(e->cmd_defns + idx))
-                       /* end-of-list */
-                       return 0;
-               else
-                       return e->cmd_defns[idx].cmd_num;
-       case ENGINE_CTRL_GET_NAME_LEN_FROM_CMD:
-               return strlen(e->cmd_defns[idx].cmd_name);
-       case ENGINE_CTRL_GET_NAME_FROM_CMD:
-               return BIO_snprintf(s,strlen(e->cmd_defns[idx].cmd_name) + 1,
-                                   "%s", e->cmd_defns[idx].cmd_name);
-       case ENGINE_CTRL_GET_DESC_LEN_FROM_CMD:
-               if(e->cmd_defns[idx].cmd_desc)
-                       return strlen(e->cmd_defns[idx].cmd_desc);
-               return strlen(int_no_description);
-       case ENGINE_CTRL_GET_DESC_FROM_CMD:
-               if(e->cmd_defns[idx].cmd_desc)
-                       return BIO_snprintf(s,
-                                           strlen(e->cmd_defns[idx].cmd_desc) + 1,
-                                           "%s", e->cmd_defns[idx].cmd_desc);
-               return BIO_snprintf(s, strlen(int_no_description) + 1,"%s",
-                                   int_no_description);
-       case ENGINE_CTRL_GET_CMD_FLAGS:
-               return e->cmd_defns[idx].cmd_flags;
-               }
-       /* Shouldn't really be here ... */
-       ENGINEerr(ENGINE_F_INT_CTRL_HELPER,ENGINE_R_INTERNAL_LIST_ERROR);
-       return -1;
-       }
+                           void (*f) (void))
+{
+    int idx;
+    char *s = (char *)p;
+    /* Take care of the easy one first (eg. it requires no searches) */
+    if (cmd == ENGINE_CTRL_GET_FIRST_CMD_TYPE) {
+        if ((e->cmd_defns == NULL) || int_ctrl_cmd_is_null(e->cmd_defns))
+            return 0;
+        return e->cmd_defns->cmd_num;
+    }
+    /* One or two commands require that "p" be a valid string buffer */
+    if ((cmd == ENGINE_CTRL_GET_CMD_FROM_NAME) ||
+        (cmd == ENGINE_CTRL_GET_NAME_FROM_CMD) ||
+        (cmd == ENGINE_CTRL_GET_DESC_FROM_CMD)) {
+        if (s == NULL) {
+            ENGINEerr(ENGINE_F_INT_CTRL_HELPER, ERR_R_PASSED_NULL_PARAMETER);
+            return -1;
+        }
+    }
+    /* Now handle cmd_name -> cmd_num conversion */
+    if (cmd == ENGINE_CTRL_GET_CMD_FROM_NAME) {
+        if ((e->cmd_defns == NULL)
+            || ((idx = int_ctrl_cmd_by_name(e->cmd_defns, s)) < 0)) {
+            ENGINEerr(ENGINE_F_INT_CTRL_HELPER, ENGINE_R_INVALID_CMD_NAME);
+            return -1;
+        }
+        return e->cmd_defns[idx].cmd_num;
+    }
+    /*
+     * For the rest of the commands, the 'long' argument must specify a valid
+     * command number - so we need to conduct a search.
+     */
+    if ((e->cmd_defns == NULL) || ((idx = int_ctrl_cmd_by_num(e->cmd_defns,
+                                                              (unsigned int)
+                                                              i)) < 0)) {
+        ENGINEerr(ENGINE_F_INT_CTRL_HELPER, ENGINE_R_INVALID_CMD_NUMBER);
+        return -1;
+    }
+    /* Now the logic splits depending on command type */
+    switch (cmd) {
+    case ENGINE_CTRL_GET_NEXT_CMD_TYPE:
+        idx++;
+        if (int_ctrl_cmd_is_null(e->cmd_defns + idx))
+            /* end-of-list */
+            return 0;
+        else
+            return e->cmd_defns[idx].cmd_num;
+    case ENGINE_CTRL_GET_NAME_LEN_FROM_CMD:
+        return strlen(e->cmd_defns[idx].cmd_name);
+    case ENGINE_CTRL_GET_NAME_FROM_CMD:
+        return BIO_snprintf(s, strlen(e->cmd_defns[idx].cmd_name) + 1,
+                            "%s", e->cmd_defns[idx].cmd_name);
+    case ENGINE_CTRL_GET_DESC_LEN_FROM_CMD:
+        if (e->cmd_defns[idx].cmd_desc)
+            return strlen(e->cmd_defns[idx].cmd_desc);
+        return strlen(int_no_description);
+    case ENGINE_CTRL_GET_DESC_FROM_CMD:
+        if (e->cmd_defns[idx].cmd_desc)
+            return BIO_snprintf(s,
+                                strlen(e->cmd_defns[idx].cmd_desc) + 1,
+                                "%s", e->cmd_defns[idx].cmd_desc);
+        return BIO_snprintf(s, strlen(int_no_description) + 1, "%s",
+                            int_no_description);
+    case ENGINE_CTRL_GET_CMD_FLAGS:
+        return e->cmd_defns[idx].cmd_flags;
+    }
+    /* Shouldn't really be here ... */
+    ENGINEerr(ENGINE_F_INT_CTRL_HELPER, ENGINE_R_INTERNAL_LIST_ERROR);
+    return -1;
+}
 
-int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void))
-       {
-       int ctrl_exists, ref_exists;
-       if(e == NULL)
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL,ERR_R_PASSED_NULL_PARAMETER);
-               return 0;
-               }
-       CRYPTO_w_lock(CRYPTO_LOCK_ENGINE);
-       ref_exists = ((e->struct_ref > 0) ? 1 : 0);
-       CRYPTO_w_unlock(CRYPTO_LOCK_ENGINE);
-       ctrl_exists = ((e->ctrl == NULL) ? 0 : 1);
-       if(!ref_exists)
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL,ENGINE_R_NO_REFERENCE);
-               return 0;
-               }
-       /* Intercept any "root-level" commands before trying to hand them on to
-        * ctrl() handlers. */
-       switch(cmd)
-               {
-       case ENGINE_CTRL_HAS_CTRL_FUNCTION:
-               return ctrl_exists;
-       case ENGINE_CTRL_GET_FIRST_CMD_TYPE:
-       case ENGINE_CTRL_GET_NEXT_CMD_TYPE:
-       case ENGINE_CTRL_GET_CMD_FROM_NAME:
-       case ENGINE_CTRL_GET_NAME_LEN_FROM_CMD:
-       case ENGINE_CTRL_GET_NAME_FROM_CMD:
-       case ENGINE_CTRL_GET_DESC_LEN_FROM_CMD:
-       case ENGINE_CTRL_GET_DESC_FROM_CMD:
-       case ENGINE_CTRL_GET_CMD_FLAGS:
-               if(ctrl_exists && !(e->flags & ENGINE_FLAGS_MANUAL_CMD_CTRL))
-                       return int_ctrl_helper(e,cmd,i,p,f);
-               if(!ctrl_exists)
-                       {
-                       ENGINEerr(ENGINE_F_ENGINE_CTRL,ENGINE_R_NO_CONTROL_FUNCTION);
-                       /* For these cmd-related functions, failure is indicated
-                        * by a -1 return value (because 0 is used as a valid
-                        * return in some places). */
-                       return -1;
-                       }
-       default:
-               break;
-               }
-       /* Anything else requires a ctrl() handler to exist. */
-       if(!ctrl_exists)
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL,ENGINE_R_NO_CONTROL_FUNCTION);
-               return 0;
-               }
-       return e->ctrl(e, cmd, i, p, f);
-       }
+int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f) (void))
+{
+    int ctrl_exists, ref_exists;
+    if (e == NULL) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL, ERR_R_PASSED_NULL_PARAMETER);
+        return 0;
+    }
+    CRYPTO_THREAD_write_lock(global_engine_lock);
+    ref_exists = ((e->struct_ref > 0) ? 1 : 0);
+    CRYPTO_THREAD_unlock(global_engine_lock);
+    ctrl_exists = ((e->ctrl == NULL) ? 0 : 1);
+    if (!ref_exists) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL, ENGINE_R_NO_REFERENCE);
+        return 0;
+    }
+    /*
+     * Intercept any "root-level" commands before trying to hand them on to
+     * ctrl() handlers.
+     */
+    switch (cmd) {
+    case ENGINE_CTRL_HAS_CTRL_FUNCTION:
+        return ctrl_exists;
+    case ENGINE_CTRL_GET_FIRST_CMD_TYPE:
+    case ENGINE_CTRL_GET_NEXT_CMD_TYPE:
+    case ENGINE_CTRL_GET_CMD_FROM_NAME:
+    case ENGINE_CTRL_GET_NAME_LEN_FROM_CMD:
+    case ENGINE_CTRL_GET_NAME_FROM_CMD:
+    case ENGINE_CTRL_GET_DESC_LEN_FROM_CMD:
+    case ENGINE_CTRL_GET_DESC_FROM_CMD:
+    case ENGINE_CTRL_GET_CMD_FLAGS:
+        if (ctrl_exists && !(e->flags & ENGINE_FLAGS_MANUAL_CMD_CTRL))
+            return int_ctrl_helper(e, cmd, i, p, f);
+        if (!ctrl_exists) {
+            ENGINEerr(ENGINE_F_ENGINE_CTRL, ENGINE_R_NO_CONTROL_FUNCTION);
+            /*
+             * For these cmd-related functions, failure is indicated by a -1
+             * return value (because 0 is used as a valid return in some
+             * places).
+             */
+            return -1;
+        }
+    default:
+        break;
+    }
+    /* Anything else requires a ctrl() handler to exist. */
+    if (!ctrl_exists) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL, ENGINE_R_NO_CONTROL_FUNCTION);
+        return 0;
+    }
+    return e->ctrl(e, cmd, i, p, f);
+}
 
 int ENGINE_cmd_is_executable(ENGINE *e, int cmd)
-       {
-       int flags;
-       if((flags = ENGINE_ctrl(e, ENGINE_CTRL_GET_CMD_FLAGS, cmd, NULL, NULL)) < 0)
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CMD_IS_EXECUTABLE,
-                       ENGINE_R_INVALID_CMD_NUMBER);
-               return 0;
-               }
-       if(!(flags & ENGINE_CMD_FLAG_NO_INPUT) &&
-                       !(flags & ENGINE_CMD_FLAG_NUMERIC) &&
-                       !(flags & ENGINE_CMD_FLAG_STRING))
-               return 0;
-       return 1;
-       }
+{
+    int flags;
+    if ((flags =
+         ENGINE_ctrl(e, ENGINE_CTRL_GET_CMD_FLAGS, cmd, NULL, NULL)) < 0) {
+        ENGINEerr(ENGINE_F_ENGINE_CMD_IS_EXECUTABLE,
+                  ENGINE_R_INVALID_CMD_NUMBER);
+        return 0;
+    }
+    if (!(flags & ENGINE_CMD_FLAG_NO_INPUT) &&
+        !(flags & ENGINE_CMD_FLAG_NUMERIC) &&
+        !(flags & ENGINE_CMD_FLAG_STRING))
+        return 0;
+    return 1;
+}
 
 int ENGINE_ctrl_cmd(ENGINE *e, const char *cmd_name,
-        long i, void *p, void (*f)(void), int cmd_optional)
-        {
-       int num;
+                    long i, void *p, void (*f) (void), int cmd_optional)
+{
+    int num;
 
-       if((e == NULL) || (cmd_name == NULL))
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD,
-                       ERR_R_PASSED_NULL_PARAMETER);
-               return 0;
-               }
-       if((e->ctrl == NULL) || ((num = ENGINE_ctrl(e,
-                                       ENGINE_CTRL_GET_CMD_FROM_NAME,
-                                       0, (void *)cmd_name, NULL)) <= 0))
-               {
-               /* If the command didn't *have* to be supported, we fake
-                * success. This allows certain settings to be specified for
-                * multiple ENGINEs and only require a change of ENGINE id
-                * (without having to selectively apply settings). Eg. changing
-                * from a hardware device back to the regular software ENGINE
-                * without editing the config file, etc. */
-               if(cmd_optional)
-                       {
-                       ERR_clear_error();
-                       return 1;
-                       }
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD,
-                       ENGINE_R_INVALID_CMD_NAME);
-               return 0;
-               }
-       /* Force the result of the control command to 0 or 1, for the reasons
-        * mentioned before. */
-        if (ENGINE_ctrl(e, num, i, p, f) > 0)
-                return 1;
+    if ((e == NULL) || (cmd_name == NULL)) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD, ERR_R_PASSED_NULL_PARAMETER);
         return 0;
+    }
+    if ((e->ctrl == NULL) || ((num = ENGINE_ctrl(e,
+                                                 ENGINE_CTRL_GET_CMD_FROM_NAME,
+                                                 0, (void *)cmd_name,
+                                                 NULL)) <= 0)) {
+        /*
+         * If the command didn't *have* to be supported, we fake success.
+         * This allows certain settings to be specified for multiple ENGINEs
+         * and only require a change of ENGINE id (without having to
+         * selectively apply settings). Eg. changing from a hardware device
+         * back to the regular software ENGINE without editing the config
+         * file, etc.
+         */
+        if (cmd_optional) {
+            ERR_clear_error();
+            return 1;
         }
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD, ENGINE_R_INVALID_CMD_NAME);
+        return 0;
+    }
+    /*
+     * Force the result of the control command to 0 or 1, for the reasons
+     * mentioned before.
+     */
+    if (ENGINE_ctrl(e, num, i, p, f) > 0)
+        return 1;
+    return 0;
+}
 
 int ENGINE_ctrl_cmd_string(ENGINE *e, const char *cmd_name, const char *arg,
-                               int cmd_optional)
-       {
-       int num, flags;
-       long l;
-       char *ptr;
-       if((e == NULL) || (cmd_name == NULL))
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ERR_R_PASSED_NULL_PARAMETER);
-               return 0;
-               }
-       if((e->ctrl == NULL) || ((num = ENGINE_ctrl(e,
-                                       ENGINE_CTRL_GET_CMD_FROM_NAME,
-                                       0, (void *)cmd_name, NULL)) <= 0))
-               {
-               /* If the command didn't *have* to be supported, we fake
-                * success. This allows certain settings to be specified for
-                * multiple ENGINEs and only require a change of ENGINE id
-                * (without having to selectively apply settings). Eg. changing
-                * from a hardware device back to the regular software ENGINE
-                * without editing the config file, etc. */
-               if(cmd_optional)
-                       {
-                       ERR_clear_error();
-                       return 1;
-                       }
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ENGINE_R_INVALID_CMD_NAME);
-               return 0;
-               }
-       if(!ENGINE_cmd_is_executable(e, num))
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ENGINE_R_CMD_NOT_EXECUTABLE);
-               return 0;
-               }
-       if((flags = ENGINE_ctrl(e, ENGINE_CTRL_GET_CMD_FLAGS, num, NULL, NULL)) < 0)
-               {
-               /* Shouldn't happen, given that ENGINE_cmd_is_executable()
-                * returned success. */
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ENGINE_R_INTERNAL_LIST_ERROR);
-               return 0;
-               }
-       /* If the command takes no input, there must be no input. And vice
-        * versa. */
-       if(flags & ENGINE_CMD_FLAG_NO_INPUT)
-               {
-               if(arg != NULL)
-                       {
-                       ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                               ENGINE_R_COMMAND_TAKES_NO_INPUT);
-                       return 0;
-                       }
-               /* We deliberately force the result of ENGINE_ctrl() to 0 or 1
-                * rather than returning it as "return data". This is to ensure
-                * usage of these commands is consistent across applications and
-                * that certain applications don't understand it one way, and
-                * others another. */
-               if(ENGINE_ctrl(e, num, 0, (void *)arg, NULL) > 0)
-                       return 1;
-               return 0;
-               }
-       /* So, we require input */
-       if(arg == NULL)
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ENGINE_R_COMMAND_TAKES_INPUT);
-               return 0;
-               }
-       /* If it takes string input, that's easy */
-       if(flags & ENGINE_CMD_FLAG_STRING)
-               {
-               /* Same explanation as above */
-               if(ENGINE_ctrl(e, num, 0, (void *)arg, NULL) > 0)
-                       return 1;
-               return 0;
-               }
-       /* If it doesn't take numeric either, then it is unsupported for use in
-        * a config-setting situation, which is what this function is for. This
-        * should never happen though, because ENGINE_cmd_is_executable() was
-        * used. */
-       if(!(flags & ENGINE_CMD_FLAG_NUMERIC))
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ENGINE_R_INTERNAL_LIST_ERROR);
-               return 0;
-               }
-       l = strtol(arg, &ptr, 10);
-       if((arg == ptr) || (*ptr != '\0'))
-               {
-               ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
-                       ENGINE_R_ARGUMENT_IS_NOT_A_NUMBER);
-               return 0;
-               }
-       /* Force the result of the control command to 0 or 1, for the reasons
-        * mentioned before. */
-       if(ENGINE_ctrl(e, num, l, NULL, NULL) > 0)
-               return 1;
-       return 0;
-       }
+                           int cmd_optional)
+{
+    int num, flags;
+    long l;
+    char *ptr;
+    if ((e == NULL) || (cmd_name == NULL)) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                  ERR_R_PASSED_NULL_PARAMETER);
+        return 0;
+    }
+    if ((e->ctrl == NULL) || ((num = ENGINE_ctrl(e,
+                                                 ENGINE_CTRL_GET_CMD_FROM_NAME,
+                                                 0, (void *)cmd_name,
+                                                 NULL)) <= 0)) {
+        /*
+         * If the command didn't *have* to be supported, we fake success.
+         * This allows certain settings to be specified for multiple ENGINEs
+         * and only require a change of ENGINE id (without having to
+         * selectively apply settings). Eg. changing from a hardware device
+         * back to the regular software ENGINE without editing the config
+         * file, etc.
+         */
+        if (cmd_optional) {
+            ERR_clear_error();
+            return 1;
+        }
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING, ENGINE_R_INVALID_CMD_NAME);
+        return 0;
+    }
+    if (!ENGINE_cmd_is_executable(e, num)) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                  ENGINE_R_CMD_NOT_EXECUTABLE);
+        return 0;
+    }
+    if ((flags =
+         ENGINE_ctrl(e, ENGINE_CTRL_GET_CMD_FLAGS, num, NULL, NULL)) < 0) {
+        /*
+         * Shouldn't happen, given that ENGINE_cmd_is_executable() returned
+         * success.
+         */
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                  ENGINE_R_INTERNAL_LIST_ERROR);
+        return 0;
+    }
+    /*
+     * If the command takes no input, there must be no input. And vice versa.
+     */
+    if (flags & ENGINE_CMD_FLAG_NO_INPUT) {
+        if (arg != NULL) {
+            ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                      ENGINE_R_COMMAND_TAKES_NO_INPUT);
+            return 0;
+        }
+        /*
+         * We deliberately force the result of ENGINE_ctrl() to 0 or 1 rather
+         * than returning it as "return data". This is to ensure usage of
+         * these commands is consistent across applications and that certain
+         * applications don't understand it one way, and others another.
+         */
+        if (ENGINE_ctrl(e, num, 0, (void *)arg, NULL) > 0)
+            return 1;
+        return 0;
+    }
+    /* So, we require input */
+    if (arg == NULL) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                  ENGINE_R_COMMAND_TAKES_INPUT);
+        return 0;
+    }
+    /* If it takes string input, that's easy */
+    if (flags & ENGINE_CMD_FLAG_STRING) {
+        /* Same explanation as above */
+        if (ENGINE_ctrl(e, num, 0, (void *)arg, NULL) > 0)
+            return 1;
+        return 0;
+    }
+    /*
+     * If it doesn't take numeric either, then it is unsupported for use in a
+     * config-setting situation, which is what this function is for. This
+     * should never happen though, because ENGINE_cmd_is_executable() was
+     * used.
+     */
+    if (!(flags & ENGINE_CMD_FLAG_NUMERIC)) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                  ENGINE_R_INTERNAL_LIST_ERROR);
+        return 0;
+    }
+    l = strtol(arg, &ptr, 10);
+    if ((arg == ptr) || (*ptr != '\0')) {
+        ENGINEerr(ENGINE_F_ENGINE_CTRL_CMD_STRING,
+                  ENGINE_R_ARGUMENT_IS_NOT_A_NUMBER);
+        return 0;
+    }
+    /*
+     * Force the result of the control command to 0 or 1, for the reasons
+     * mentioned before.
+     */
+    if (ENGINE_ctrl(e, num, l, NULL, NULL) > 0)
+        return 1;
+    return 0;
+}