From cbfca49ac69e701566d507e6ee77a7a77929f054 Mon Sep 17 00:00:00 2001
From: ston1th <ston1th@giftfish.de>
Date: Tue, 10 Jan 2017 22:44:06 +0100
Subject: [PATCH] some improvements

---
 ddns.c | 42 +++++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/ddns.c b/ddns.c
index 44e0176..c6107cc 100644
--- a/ddns.c
+++ b/ddns.c
@@ -7,6 +7,8 @@
 #include <err.h>
 
 #define SEP '='
+#define MAX_QUERY_LEN 255
+#define MAX_QUERY_ARGS 2
 #define IP_LEN 16
 #define IP_FILE "ip.txt"
 #define TOKEN "<empty>"
@@ -23,9 +25,11 @@ char **parse(const char *str) {
         const char *s = str;
         char *qs, *token;
         char **arr = NULL;
-        int c = 1;
+        int c = 1, argc = 0;
         qs = strdup(s);
         while((token = strsep(&qs, "&")) != NULL) {
+                if(++argc > MAX_QUERY_ARGS)
+                        break;
                 c++;
                 if(arr == NULL) {
                         arr = malloc(c*sizeof(char *));
@@ -58,9 +62,10 @@ int ctb(unsigned char a, unsigned char b) {
 }
 
 int ctc(const char *a, const char *b) {
-        if(strlen(a) != strlen(b)) {
+        if(!a || !b)
+                return(0);
+        if(strlen(a) != strlen(b))
                 return(0);
-        }
         const char *x = a, *y = b;
         char v = 0;
         while(*x)
@@ -69,7 +74,7 @@ int ctc(const char *a, const char *b) {
 }
 
 int set_ip(char *env, int fd) {
-        char *ip, *token, *tmp;
+        char *ip = NULL, *token = NULL, *tmp = NULL;
         int ret = -1, len = 0;
         char **arg = parse(env);
         char **arr = arg;
@@ -91,35 +96,46 @@ int set_ip(char *env, int fd) {
         tmp = NULL;
         free_arr(arg);
         if(ctc(token, TOKEN) == 1) {
-                len = strlen(ip);
-                if(len >= IP_LEN-1)
-                        len = IP_LEN-1;
-                write(fd, ip, len);
+                if(ip) {
+                        len = strlen(ip);
+                        if(len >= IP_LEN-1)
+                                len = IP_LEN-1;
+                        write(fd, ip, len);
+                }
                 close(fd);
         } else
                 ret = 1;
-        free(token);
-        free(ip);
+        if(ip)
+                free(ip);
+        if(token)
+                free(token);
         return(ret);
 }
 
 char *err_msg[2] = {"wrong input", "wrong token"};
 
 int main(void) {
-        char *env;
+        char *env = NULL;
         char ip[IP_LEN];
         int errn = 0, len = 0;
-        int rfd = open(IP_FILE, O_RDONLY|O_SHLOCK);
+        int rfd, wfd;
+        if((rfd = open(IP_FILE, O_RDONLY|O_SHLOCK)) == -1)
+                err(EXIT_FAILURE, "read open failed");
         if(read(rfd, &ip, IP_LEN) <= 0)
                 ip[0] = '\0';
         close(rfd);
         ip[IP_LEN] = '\0';
-        int wfd = open(IP_FILE, O_WRONLY|O_CREAT|O_TRUNC|O_EXLOCK);
+        if((wfd = open(IP_FILE, O_WRONLY|O_CREAT|O_TRUNC|O_EXLOCK)) == -1)
+                err(EXIT_FAILURE, "rw open failed");
         if(pledge("stdio", NULL) == -1) 
                 err(EXIT_FAILURE, "pledge");
         env = getenv("QUERY_STRING");
         header();
         if(env != NULL) {
+                if(strlen(env) > MAX_QUERY_LEN) {
+                        puts("query longer than 255 bytes");
+                        return(EXIT_SUCCESS);
+                }
                 if((errn = set_ip(env, wfd)) >= 0)
                         puts(err_msg[errn]);
                 else