From: Richard Yu <yurichard3839@gmail.com>
Date: Mon, 1 Sep 2025 14:27:33 +0000 (+0800)
Subject: main: Add `stderr` option for cgi-exec to redirect stderr to stdout
X-Git-Url: http://git.openwrt.org/%22https:/collectd.org//%22https:/github.com/fatedier/frp%22/%22https:/collectd.org/%22https:/github.com/fatedier/frp%22?a=commitdiff_plain;p=project%2Fcgi-io.git

main: Add `stderr` option for cgi-exec to redirect stderr to stdout

This feature is used by openwrt/luci#7920
It allows cgi processes to follow real-time output sent to stderr.

Closes #2

Signed-off-by: Richard Yu <yurichard3839@gmail.com>
Signed-off-by: Paul Donald <newtwen+github@gmail.com>
Link: https://github.com/openwrt/cgi-io/pull/3
Signed-off-by: Robert Marko <robimarko@gmail.com>
---

diff --git a/main.c b/main.c
index 8ca4c04..806d715 100644
--- a/main.c
+++ b/main.c
@@ -730,15 +730,15 @@ lookup_executable(const char *cmd)
 static int
 main_exec(int argc, char **argv)
 {
-	char *fields[] = { "sessionid", NULL, "command", NULL, "filename", NULL, "mimetype", NULL };
+	char *fields[] = { "sessionid", NULL, "command", NULL, "filename", NULL, "mimetype", NULL, "stderr", NULL };
 	int i, devnull, status, fds[2];
-	bool allowed = false;
+	bool allowed = false, redir_stderr = false;
 	ssize_t len = 0;
 	const char *exe;
 	char *p, **args;
 	pid_t pid;
 
-	autochar *post = postdecode(fields, 4);
+	autochar *post = postdecode(fields, 5);
 	(void) post;
 
 	if (!fields[1] || !session_access(fields[1], "cgi-io", "exec", "read"))
@@ -752,6 +752,10 @@ main_exec(int argc, char **argv)
 		if (!isalnum(*p) && !strchr(" .;=/-", *p))
 			return failure(400, 0, "Invalid characters in mimetype");
 
+	p = fields[9];
+	if (p && p[0] == '1' && p[1] == '\0')
+		redir_stderr = true;
+
 	args = fields[3] ? parse_command(fields[3]) : NULL;
 
 	if (!args)
@@ -796,7 +800,8 @@ main_exec(int argc, char **argv)
 
 		if (devnull > -1) {
 			dup2(devnull, 0);
-			dup2(devnull, 2);
+			if (!redir_stderr)
+				dup2(devnull, 2);
 			close(devnull);
 		}
 		else {
@@ -805,6 +810,8 @@ main_exec(int argc, char **argv)
 		}
 
 		dup2(fds[1], 1);
+		if (redir_stderr)
+			dup2(fds[1], 2);
 		close(fds[0]);
 		close(fds[1]);