Parsing HTTP data in C using MCU - c++

Question

I am trying to parse the data obtained from GET / POST request using C in a MCU based project. I must say upfront that I haven't work with c and c++ for some time, so any suggestion is welcome.
So, the data arriving the MCU has the following markup:
HTTP/1.1
Authorization: Basic blablah
Content-Type: application/json
{
redLedBrightness:50,
redLedIsOn:true,
greenLedBrightness:70,
greenLedIsOn:false,
}
where the end beginnning of the lines are given respectively by \r and \n.
My approach entailed processing line by line, and searching the corresponding key (e.g. Authorization or redLedBrightness) and its value (e.g. blahblah or 50). I wrote the following code, which seemed to be working fine in the compiler I was using, but not in the MCU.
One of problems seems to be in the statement *tempInDataP = *index; since the MCU stops hanging if I comment it out. Of course I need this line, but I cannot figure out where the problem(s) is (are). I suspect the compiler I am using is not showing all the errors.
Here is an adaption of the code:
#include <iostream>
#include <string>
#include <cstring>
#define IN_DATA_SIZE 100
#define TEMP_IN_DATA_SIZE 10
using namespace std;
char mock[] = "Authentication:YERL90,\r\nredLedBri:400,\r\nredLedOn:true\r\n";
char * mockP = mock;
char inData[IN_DATA_SIZE];
char * inDataP = inData;
char tempInData[TEMP_IN_DATA_SIZE];
char * tempInDataP = tempInData;
const char * auth = "YERL90";
bool isAuthenticated = false;
void printBuffer(char * buf) {
for (char *p = buf; *p; p++) {
cout << *p;
}
}
void resetBuffer(char * buf, int _size)
{
memset(buf, 0, _size);
}
/**
* Returns true if keyWord exists and update the variable tempInData
* with the response / value
*/
bool parseResponse(char * res, const char * keyWord, int dataShift ) {
cout << "\nParsing:" << res << endl;
char * index;
// Reset temp in data buffer and its pointer
resetBuffer(tempInData, TEMP_IN_DATA_SIZE);
tempInDataP = &tempInData[0];
// Search for a member /keyword inside the response
index = strstr(res, keyWord);
if (index) {
// Keyword exists in the response
// Move the index to the beginning of the value (key:value)
index = index + strlen(keyWord) + dataShift;
while ((*index != '\r') && (*index != ',')) {
*tempInDataP = *index;
tempInDataP++;
index++;
}
// Terminate the string with a null
*tempInDataP = '\0';
return true;
} else {
cout << "-bul" << endl;
//Object was not found
return false;
}
}
bool checkAuth(const char * _auth) {
if (strcmp (auth, _auth) == 0)
return true;
else
return false;
}
int main()
{
while(*mockP) {
// Simulating, reading data from the channel
*inDataP=*mockP;
//Parsing line by line
if (*inDataP == '\n') {
//Check for authentication if not done yet
if(!isAuthenticated) {
cout << "Authenticating ..." << endl;
if(parseResponse(inData, "Authentication", 1)) {
cout << "Key exists ..." << endl;
if(checkAuth(tempInData)) {
cout << "Correct Password" << endl;
isAuthenticated = true;
} else {
cout << "Password Invalid" << endl;
// Prepare headers
// Send response with unauthorized access
// stop connection
break;
}
} else {
cout << "Data not found" << endl;
}
} else {
// User is logged in
cout << "User is logged in" << endl;
if(parseResponse(inData, "redLedBri", 1)) {
cout << "Data exists:" << tempInData << endl;
// update local variables
} else {
cout << "Data not found" << endl;
}
}
resetBuffer(inData, IN_DATA_SIZE);
inDataP = &inData[0];
}
else {
inDataP++;
}
mockP++;
}
//close connection and log the user out
return 0;
}
I am open for other alternatives, as this implementation seems a bit cumbersome depending on the JSON file sent to the MCU.

Answer 1

I see potential buffer overruns. You trust your input too much. You assume it will end with '\r' or ',' characters, and if it doesn't then you will overrun the bounds of your array(s) and access arbitrary memory.
At the very least, pass the maximum length with each array pointer, and check in each loop iteration that you NEVER access an element beyond the last address of the array.