Remote config files

Config parser can now read config files stored remotely via
https/http/ftp. Requires libcurl.

config_parser.c

@@ -52,6 +52,10 @@
   #include <sys/wait.h>
 #endif
 
+#ifdef HAVE_LIBCURL
+#include <curl/curl.h>
+#endif
+
 char *cnfbuf = NULL;  //config file loaded
 int fileconf_load;   //config file load status
 const char def_conf[] = "sgminer.conf";
@@ -490,6 +494,82 @@ static struct opt_table *opt_find(struct opt_table *tbl, char *optname)
   return NULL;
 }
 
+/**************************************
+ * Remote Config Functions (Curl Only)
+ **************************************/
+#ifdef HAVE_LIBCURL
+  struct remote_config {
+    const char *filename;
+    FILE *stream;
+  };
+
+  //curl file data write callback
+  static size_t fetch_remote_config_cb(void *buffer, size_t size, size_t nmemb, void *stream)
+  {
+    struct remote_config *out = (struct remote_config *)stream;
+    
+    //create file if not created
+    if(out && !out->stream)
+    {
+      if(!(out->stream = fopen(out->filename, "w+")))
+        return -1;
+    }
+    
+    return fwrite(buffer, size, nmemb, out->stream);
+  }
+
+  //download remote config file - return filename on success or NULL on failure
+  static char *fetch_remote_config(const char *url)
+  {
+    CURL *curl;
+    CURLcode res;
+    char *p;
+    struct remote_config file = { "", NULL };
+    
+    //get filename out of url
+    if((p = strrchr(url, '/')) == NULL)
+    {
+      applog(LOG_ERR, "Fetch remote file failed: Invalid URL");
+      return NULL;
+    }
+
+    file.filename = p+1;
+
+    //check for empty filename
+    if(file.filename[0] == '\0')
+    {
+      applog(LOG_ERR, "Fetch remote file failed: Invalid Filename");
+      return NULL;
+    }
+    
+    //init curl
+    if((curl = curl_easy_init()) == NULL)
+    {
+      applog(LOG_ERR, "Fetch remote file failed: curl init failed.");
+      return NULL;
+    }
+    
+    //https stuff - skip verification we just want the data
+    if(strstr(url, "https") != NULL)
+      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
+    
+    //set url
+    curl_easy_setopt(curl, CURLOPT_URL, url);
+    //set write callback and fileinfo
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fetch_remote_config_cb);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &file);
+    
+    if((res = curl_easy_perform(curl)) != CURLE_OK)
+      applog(LOG_ERR, "Fetch remote file failed: %s", curl_easy_strerror(res));
+    
+    if(file.stream)
+      fclose(file.stream);
+    
+    curl_easy_cleanup(curl);
+    
+    return (char *)((res == CURLE_OK)?file.filename:NULL);
+  }
+#endif
 
 /***************************************
 * Config Parsing Functions
@@ -633,6 +713,16 @@ char *load_config(const char *arg, const char *parentkey, void __maybe_unused *u
   json_error_t err;
   json_t *config;
 
+  #ifdef HAVE_LIBCURL
+    //if detected as url
+    if((strstr(arg, "http://") != NULL) || (strstr(arg, "https://") != NULL) || (strstr(arg, "ftp://") != NULL))
+    {
+      //download config file locally and reset arg to it so we can parse it
+      if((arg = fetch_remote_config(arg)) == NULL)
+        return NULL;
+    }
+  #endif
+  
   //most likely useless but leaving it here for now...
   if(!cnfbuf)
     cnfbuf = strdup(arg);