Support providing CGI options for alternate template file names

NEWS.adoc

@@ -338,6 +338,9 @@ several `FSD` notifications into one executed action. [PR #3097]
    * Introduced a `@NUT_UPSSTATS_TEMPLATE@` command which the HTML template
      files now MUST start with (safety check that we are reading a template).
      [issue #3252, PR #3249]
+   * (Experimental) Custom templates other than `upsstats{,-single}.html` can
+     now be specified as CGI parameters, if locally permitted via `hosts.conf`.
+     [issue #2524, PR #3304]
 
  - `upssched` tool updates:
    * Previously in PR #2896 (NUT releases v2.8.3 and v2.8.4) the `UPSNAME` and

clients/cgilib.c

@@ -87,8 +87,15 @@ void extractcgiargs(void)
 	while (ptr) {
 		varname = ptr;
 		eq = strchr(varname, '=');
-		if (!eq) {
-			ptr = strchr(varname, '&');
+		amp = strchr(varname, '&');
+		if (!eq
+		 || (eq && amp && amp < eq)
+		) {
+			/* Last token is a flag (without assignment in sight),
+			 * OR we've got a flag token in the middle of a query
+			 * string, followed by another key=value pair later on.
+			 */
+			ptr = amp;
 			if (ptr)
 				*ptr++ = '\0';
 
@@ -99,6 +106,8 @@ void extractcgiargs(void)
 			continue;
 		}
 
+		/* The nearest point of interest is a key=value pair,
+		 * maybe followed by another amp and flag or assignment... */
 		*eq = '\0';
 		value = eq + 1;
 		amp = strchr(value, '&');
@@ -111,6 +120,8 @@ void extractcgiargs(void)
 
 		cleanvar = unescape(varname);
 		cleanval = unescape(value);
+		upsdebugx(3, "%s: parsearg('%s', '%s')<br/>",
+			__func__, NUT_STRARG(cleanvar), NUT_STRARG(cleanval));
 		parsearg(cleanvar, cleanval);
 		free(cleanvar);
 		free(cleanval);

clients/upsimage.c

@@ -20,6 +20,7 @@
    Copyrights:
      (C) 1998  Russell Kroll <rkroll@exploits.org>
      (C) 2002  Simon Rozman <simon@rozman.net>
+     (C) 2020-2026 Jim Klimov <jimklimov+nut@gmail.com>
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -619,14 +620,14 @@ int main(int argc, char **argv)
 	double	var = 0;
 
 #ifdef WIN32
-        /* Required ritual before calling any socket functions */
-        static WSADATA  WSAdata;
-        static int      WSA_Started = 0;
-        if (!WSA_Started) {
-                WSAStartup(2, &WSAdata);
-                atexit((void(*)(void))WSACleanup);
-                WSA_Started = 1;
-        }
+	/* Required ritual before calling any socket functions */
+	static WSADATA	WSAdata;
+	static int	WSA_Started = 0;
+	if (!WSA_Started) {
+		WSAStartup(2, &WSAdata);
+		atexit((void(*)(void))WSACleanup);
+		WSA_Started = 1;
+	}
 
 	/* Avoid binary output conversions, e.g.
 	 * mangling what looks like CRLF on WIN32 */
@@ -646,6 +647,23 @@ int main(int argc, char **argv)
 		nut_debug_level = i;
 	}
 
+#ifdef NUT_CGI_DEBUG_UPSIMAGE
+# if (NUT_CGI_DEBUG_UPSIMAGE - 0 < 1)
+#  undef NUT_CGI_DEBUG_UPSIMAGE
+#  define NUT_CGI_DEBUG_UPSIMAGE 6
+# endif
+	/* Un-comment via make flags when developer-troubleshooting: */
+	nut_debug_level = NUT_CGI_DEBUG_UPSIMAGE;
+#endif
+
+	if (nut_debug_level > 0) {
+		cgilogbit_set();
+		printf("Content-type: text/html\n");
+		printf("Pragma: no-cache\n");
+		printf("\n");
+		printf("<p>NUT CGI Debugging enabled, level: %d</p>\n\n", nut_debug_level);
+	}
+
 	extractcgiargs();
 
 	upscli_init_default_connect_timeout(NULL, NULL, UPSCLI_DEFAULT_CONNECT_TIMEOUT);

clients/upsset.c

@@ -1,6 +1,7 @@
 /* upsset - CGI program to manage read/write variables
 
    Copyright (C) 1999  Russell Kroll <rkroll@exploits.org>
+   Copyright (C) 2020-2026 Jim Klimov <jimklimov+nut@gmail.com>
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1116,14 +1117,14 @@ int main(int argc, char **argv)
 	int i;
 
 #ifdef WIN32
-        /* Required ritual before calling any socket functions */
-        static WSADATA  WSAdata;
-        static int      WSA_Started = 0;
-        if (!WSA_Started) {
-                WSAStartup(2, &WSAdata);
-                atexit((void(*)(void))WSACleanup);
-                WSA_Started = 1;
-        }
+	/* Required ritual before calling any socket functions */
+	static WSADATA	WSAdata;
+	static int	WSA_Started = 0;
+	if (!WSA_Started) {
+		WSAStartup(2, &WSAdata);
+		atexit((void(*)(void))WSACleanup);
+		WSA_Started = 1;
+	}
 
 	/* Avoid binary output conversions, e.g.
 	 * mangling what looks like CRLF on WIN32 */
@@ -1136,7 +1137,9 @@ int main(int argc, char **argv)
 	NUT_UNUSED_VARIABLE(argv);
 	username = password = function = monups = NULL;
 
-	printf("Content-type: text/html\n\n");
+	printf("Content-type: text/html\n");
+	printf("Pragma: no-cache\n");
+	printf("\n");
 
 	/* NOTE: Caller must `export NUT_DEBUG_LEVEL` to see debugs for upsc
 	 * and NUT methods called from it. This line aims to just initialize
@@ -1148,6 +1151,20 @@ int main(int argc, char **argv)
 		nut_debug_level = i;
 	}
 
+#ifdef NUT_CGI_DEBUG_UPSSET
+# if (NUT_CGI_DEBUG_UPSSET - 0 < 1)
+#  undef NUT_CGI_DEBUG_UPSSET
+#  define NUT_CGI_DEBUG_UPSSET 6
+# endif
+	/* Un-comment via make flags when developer-troubleshooting: */
+	nut_debug_level = NUT_CGI_DEBUG_UPSSET;
+#endif
+
+	if (nut_debug_level > 0) {
+		cgilogbit_set();
+		printf("<p>NUT CGI Debugging enabled, level: %d</p>\n\n", nut_debug_level);
+	}
+
 	/* see if the magic string is present in the config file */
 	check_conf();