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Correct buffer overflow and remove magic constants from esp8266 example

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The msg[] array is defined as 50 bytes long, but then the snprintf is
protected at 75 bytes long, which is incorrectly 25 bytes longer than
the underlying array.

To correct this, define a new macro MSG_BUFFER_SIZE and use it in both
places:
 * defining msg[]
 * writing to msg[] with snprintf()
This commit is contained in:
Kenneth Finnegan 2017-04-25 20:43:54 -07:00
parent b85f4dc35c
commit 98ad16eff8
1 changed files with 3 additions and 2 deletions
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5
examples/mqtt_esp8266/mqtt_esp8266.ino
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@ -35,7 +35,8 @@ const char* mqtt_server = "broker.mqtt-dashboard.com";
WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
char msg[50];
#define MSG_BUFFER_SIZE (50)
char msg[MSG_BUFFER_SIZE];
int value = 0;
void setup_wifi() {
@ -124,7 +125,7 @@ void loop() {
if (now - lastMsg > 2000) {
lastMsg = now;
++value;
snprintf (msg, 75, "hello world #%ld", value);
snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
Serial.print("Publish message: ");
Serial.println(msg);
client.publish("outTopic", msg);