From daadae0bf58789fb3edf04cdefd3df4447873c7e Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Wed, 19 Mar 2014 19:32:45 -0400
Subject: [PATCH] Switch to using snprintf in dhcp.c and ifch.c so that
 truncations can be easily detected.

---
 ndhc/dhcp.c  | 34 ++++++++++++++++++++--------------
 ndhc/ifchd.c | 25 ++++++++++++++++++++-----
 2 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/ndhc/dhcp.c b/ndhc/dhcp.c
index be1da05..6fee061 100644
--- a/ndhc/dhcp.c
+++ b/ndhc/dhcp.c
@@ -28,6 +28,7 @@
 
 #include <stdlib.h>
 #include <stddef.h>
+#include <stdio.h>
 #include <unistd.h>
 #include <string.h>
 #include <netinet/in.h>
@@ -52,7 +53,6 @@
 #include "log.h"
 #include "io.h"
 #include "options.h"
-#include "strl.h"
 #include "random.h"
 
 typedef enum {
@@ -66,31 +66,37 @@ static int create_udp_socket(uint32_t ip, uint16_t port, char *iface)
 {
     int fd;
     if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
-        log_error("create_udp_socket: socket failed: %s", strerror(errno));
+        log_error("%s: (%s) socket failed: %s",
+                  client_config.interface, __func__, strerror(errno));
         goto out;
     }
     int opt = 1;
     if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof opt) == -1) {
-        log_error("create_udp_socket: Set reuse addr failed: %s",
-                  strerror(errno));
+        log_error("%s: (%s) Set reuse addr failed: %s",
+                  client_config.interface, __func__, strerror(errno));
         goto out_fd;
     }
     if (setsockopt(fd, SOL_SOCKET, SO_DONTROUTE, &opt, sizeof opt) == -1) {
-        log_error("create_udp_socket: Set don't route failed: %s",
-                  strerror(errno));
+        log_error("%s: (%s) Set don't route failed: %s",
+                  client_config.interface, __func__, strerror(errno));
         goto out_fd;
     }
     struct ifreq ifr;
-    memset(&ifr, 0, sizeof (struct ifreq));
-    strnkcpy(ifr.ifr_name, iface, IFNAMSIZ);
+    memset(&ifr, 0, sizeof ifr);
+    ssize_t sl = snprintf(ifr.ifr_name, sizeof ifr.ifr_name, "%s", iface);
+    if (sl < 0 || (size_t)sl >= sizeof ifr.ifr_name) {
+        log_error("%s: (%s) Set interface name failed.",
+                  client_config.interface, __func__);
+        goto out_fd;
+    }
     if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof ifr) < 0) {
-        log_error("create_udp_socket: Set bind to device failed: %s",
-                  strerror(errno));
+        log_error("%s: (%s) Set bind to device failed: %s",
+                  client_config.interface, __func__, strerror(errno));
         goto out_fd;
     }
     if (fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK) == -1) {
-        log_error("create_udp_socket: Set non-blocking failed: %s",
-                  strerror(errno));
+        log_error("%s: (%s) Set non-blocking failed: %s",
+                  client_config.interface, __func__, strerror(errno));
         goto out_fd;
     }
 
@@ -118,8 +124,8 @@ static int create_udp_listen_socket(char *inf)
         return -1;
     int opt = 1;
     if (setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &opt, sizeof opt) == -1) {
-        log_error("create_udp_listen_socket: Set broadcast failed: %s",
-                  strerror(errno));
+        log_error("%s: (%s) Set broadcast failed: %s",
+                  client_config.interface, __func__, strerror(errno));
         close(fd);
         return -1;
     }
diff --git a/ndhc/ifchd.c b/ndhc/ifchd.c
index b49f986..ac1b7f6 100644
--- a/ndhc/ifchd.c
+++ b/ndhc/ifchd.c
@@ -52,7 +52,6 @@
 #include "pidfile.h"
 #include "signals.h"
 #include "ifchd-parse.h"
-#include "strl.h"
 #include "cap.h"
 #include "io.h"
 #include "sys.h"
@@ -106,7 +105,11 @@ static void write_resolve_conf(void)
             q = strchr(p, '\0');
         else
             *q++ = '\0';
-        strnkcpy(buf, p, sizeof buf);
+        ssize_t sl = snprintf(buf, sizeof buf, "%s", p);
+        if (sl < 0 || (size_t)sl >= sizeof buf) {
+            log_warning("%s: (%s) snprintf failed appending nameservers",
+                        client_config.interface, __func__);
+        }
 
         writeordie(resolv_conf_fd, ns_str, strlen(ns_str));
         writeordie(resolv_conf_fd, buf, strlen(buf));
@@ -123,7 +126,11 @@ static void write_resolve_conf(void)
             q = strchr(p, '\0');
         else
             *q++ = '\0';
-        strnkcpy(buf, p, sizeof buf);
+        ssize_t sl = snprintf(buf, sizeof buf, "%s", p);
+        if (sl < 0 || (size_t)sl >= sizeof buf) {
+            log_warning("%s: (%s) snprintf failed appending domains",
+                        client_config.interface, __func__);
+        }
 
         if (numdoms == 0) {
             writeordie(resolv_conf_fd, dom_str, strlen(dom_str));
@@ -185,7 +192,11 @@ void perform_dns(const char *str, size_t len)
         log_line("DNS server list is too long: %zu > %zu", len, cl.namesvrs);
         return;
     }
-    strnkcpy(cl.namesvrs, str, sizeof cl.namesvrs);
+    ssize_t sl = snprintf(cl.namesvrs, sizeof cl.namesvrs, "%s", str);
+    if (sl < 0 || (size_t)sl >= sizeof cl.namesvrs) {
+        log_warning("%s: (%s) snprintf failed",
+                    client_config.interface, __func__);
+    }
     write_resolve_conf();
     log_line("Added DNS server: '%s'", str);
 }
@@ -217,7 +228,11 @@ void perform_domain(const char *str, size_t len)
         log_line("DNS domain list is too long: %zu > %zu", len, cl.namesvrs);
         return;
     }
-    strnkcpy(cl.domains, str, sizeof cl.domains);
+    ssize_t sl = snprintf(cl.domains, sizeof cl.domains, "%s", str);
+    if (sl < 0 || (size_t)sl >= sizeof cl.domains) {
+        log_warning("%s: (%s) snprintf failed",
+                    client_config.interface, __func__);
+    }
     write_resolve_conf();
     log_line("Added DNS domain: '%s'", str);
 }