WiFi: STA connection / disconnection event handler incorrectly copies ssid from the SDK struct

[mcspr]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: any
• Core Version: 1b922ed
• Development Env: any
• Operating System: any

Problem Description

Something I noticed while looking at the event handler:

Arduino/libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.cpp

Lines 106 to 108 in 1b922ed

	auto& src = e->event_info.connected;
	WiFiEventStationModeConnected dst;
	dst.ssid = String(reinterpret_cast<char*>(src.ssid));

Arduino/libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.cpp

Lines 120 to 122 in 1b922ed

	auto& src = e->event_info.disconnected;
	WiFiEventStationModeDisconnected dst;
	dst.ssid = String(reinterpret_cast<char*>(src.ssid));

It is assumed that the pointer could be used as-is via a simple char* cast.

Arduino/tools/sdk/include/user_interface.h

Lines 516 to 528 in 1b922ed

	typedef struct {
	uint8 ssid[32];
	uint8 ssid_len;
	uint8 bssid[6];
	uint8 channel;
	} Event_StaMode_Connected_t;
	typedef struct {
	uint8 ssid[32];
	uint8 ssid_len;
	uint8 bssid[6];
	uint8 reason;
	} Event_StaMode_Disconnected_t;

While it is not true from the SDK side, it is a byte string with a separate length field.

Adding this as an issue, since I also wanted to go over other possible user_interface.h structs with ssid + ssid_len appearances before sending the patch

MCVE Sketch

Small example showing ssid.length() 33 instead of expected 32, because we read 0x20 aka ssid_len=32 plus the first 00 of zeroed out bssid[6]

#include <Arduino.h>
#include <ESP8266WiFi.h>

const char ssid[] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"; // strlen(ssid) == 32
const char pass[] = "whatever";

void setup() {
    Serial.begin(115200);
    Serial.println("trying to connect");

    static auto disconnected = WiFi.onStationModeDisconnected([](const auto& result) {
        Serial.println("onDisconnected");
        Serial.println(result.ssid);
        Serial.printf("len=%u\n", result.ssid.length());
        Serial.printf("ssid[-1]=%02X\n", result.ssid[result.ssid.length() - 1]);
        Serial.printf("reason=%d\n", static_cast<int>(result.reason));
    });

    WiFi.persistent(false);
    WiFi.begin(ssid, pass);
    if (WL_CONNECTED != WiFi.waitForConnectResult()) {
        Serial.println("wifi err");
        abort();
    }
}

void loop() {
}

Debug Messages

trying to connect
onDisconnected
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
len=33
ssid[-1]=20
reason=201