From 8a1964d5d52c3acf1127d4e8051e8282634749e4 Mon Sep 17 00:00:00 2001
From: David Phillips <dbphillipsnz@gmail.com>
Date: Tue, 19 Jul 2016 12:02:42 +1200
Subject: Major restructuring and tidying

---
 brightnessd.c | 117 +++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 79 insertions(+), 38 deletions(-)

diff --git a/brightnessd.c b/brightnessd.c
index ebd71a2..4afc3ac 100644
--- a/brightnessd.c
+++ b/brightnessd.c
@@ -14,10 +14,74 @@
 #define STEP		1
 #define BIG_STEP	10
 #define USER        "nobody"
+#define BRIGHT_BUFFER_SIZE 4
+#define DELAY_INFINITE (-1)
+
+/**
+ * create and open fifo, using chmod since mkfifo is affected by umask
+ */
+int setup_fifo()
+{
+	struct stat st;
+	if (stat(FIFO_PATH, &st) == 0)
+	{
+		if (remove(FIFO_PATH))
+		{
+			perror("remove("FIFO_PATH")");
+			return 1;
+		}
+	}
+	if (mkfifo(FIFO_PATH, 0666))
+	{
+		perror("mkfifo");
+		return 1;
+	}
+	if (chmod(FIFO_PATH, 0666))
+	{
+		perror("chmod");
+		return 1;
+	}
+	return 0;
+}
+
+int drop_priv()
+{
+	struct passwd *p = NULL;
+
+	/* get group (and more) of USER */
+	p = getpwnam(USER);
+
+	if (p == NULL)
+	{
+		fprintf(stderr, "Failed to get uid and gid of user \""USER"\", bailing\n");
+		return 1;
+	}
+
+	if (setgid(p->pw_gid))
+	{
+		fprintf(stderr, "Failed to set gid to %d\n", p->pw_gid);
+		perror("setuid");
+		return 1;
+	}
+
+	if (setuid(p->pw_uid))
+	{
+		fprintf(stderr, "Failed to set uid to %d\n", p->pw_uid);
+		perror("setuid");
+		return 1;
+	}
+
+	if (!setuid(0) || !setgid(0))
+	{
+		fprintf(stderr, "Got uid 0 or gid 0 back after dropping, bailing\n");
+		return 1;
+	}
+	return 0;
+}
 
 int get_now(FILE *f)
 {
-	char buffer[4096]; /* FIXME: magic constant is icky */
+	char buffer[BRIGHT_BUFFER_SIZE]; /* FIXME: magic constant is icky */
 	/* FIXME: check return value for error */
 	fgets(buffer, sizeof(buffer), f);
 
@@ -43,10 +107,9 @@ int main(int argc, char **argv)
 	FILE *f = NULL;
 	int fifo = 0;
 	struct pollfd fds;
-	struct passwd *p;
 	int delay = 0;
 	int nread = 0;
-	char buffer[4]; /* size 4 because max bright is 255, plus null terminator */
+	char buffer[BRIGHT_BUFFER_SIZE];
 
 	/* Open brightness file */
 	if ((f = fopen(BRIGHT_FILE, "w+")) == NULL)
@@ -55,50 +118,28 @@ int main(int argc, char **argv)
 		exit(EXIT_FAILURE);
 	}
 
-	now = get_now(f);
-	target = now;
-
-	/* create and open fifo, using chmod since mkfifo is affected by umask */
-	remove(FIFO_PATH);
-	mkfifo(FIFO_PATH, 0666);
-	chmod(FIFO_PATH, 0666);
-
-	/* FIXME : check return val */
-	fifo = open(FIFO_PATH, O_RDWR);
-
-
-	fds.fd = fifo;
-	fds.events = POLLIN;
-
-	p = getpwnam(USER);
-
-	if (p == NULL)
+	if (setup_fifo())
 	{
-		fprintf(stderr, "Failed to get uid and gid of user \""USER"\", bailing\n");
+		fclose(f);
 		return 1;
 	}
 
-	if (setgid(p->pw_gid))
+	if (drop_priv() != 0)
 	{
-		fprintf(stderr, "Failed to set gid to %d\n", p->pw_gid);
-		perror("setuid");
+		fclose(f);
 		return 1;
 	}
 
-	if (setuid(p->pw_uid))
-	{
-		fprintf(stderr, "Failed to set uid to %d\n", p->pw_uid);
-		perror("setuid");
-		return 1;
-	}
+	now = get_now(f);
+	target = now;
 
-	if (!setuid(0) || !setgid(0))
-	{
-		fprintf(stderr, "Got uid 0 or gid 0 back after dropping, bailing\n");
-		return 1;
-	}
+	/* FIXME : check return val */
+	fifo = open(FIFO_PATH, O_RDWR);
+
+	fds.fd = fifo;
+	fds.events = POLLIN;
 
-	delay = -1;
+	delay = DELAY_INFINITE;
 	while(1)
 	{
 		poll(&fds, 1, delay);
@@ -131,7 +172,7 @@ int main(int argc, char **argv)
 			if (now < target)
 				now = target;
 		} else if (now == target) {
-			delay = -1;
+			delay = DELAY_INFINITE;
 		}
 		fprintf(f, "%d\n", now);
 		rewind(f);
-- 
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