Andrew Boyson / web

Common stuff for all my devices' web server pages: css, login, log, ipv4, ipv6, firmware update, clock, reset info etc.

Dependents:   oldheating gps motorhome heating

Security

A password has to be set whenever there has been a software reset. Resets following faults or power on do not require a new password as the hash is restored from the RTC GPREG register.

The password is not saved on the device; instead a 32 bit hash of the password is saved. It would take 2^31 attempts to brute force the password: this could be done in under a month if an attempt were possible every millisecond. To prevent this a 200 ms delay is introduced in the reply to the login form, that gives a more reasonable 13 years to brute force the password.

Once the password is accepted a random session id is created. This is 36 bit to give six base 64 characters but without an extra delay. If an attempt could be made every ms then this would still take over a year to brute force.

The most likely attack would to use a dictionary with, say, 10 million entries against the password which would still take 20 days to do.

http/http-connection.c

Committer:
andrewboyson
Date:
2021-05-11
Revision:
160:daa94b75b94c
Parent:
130:9a5b8fe308f1

File content as of revision 160:daa94b75b94c:

#include <stdlib.h>

#include "http-connection.h"
#include "mstimer.h"

#define MAX_CONNECTIONS 10

static struct HttpConnection connections[MAX_CONNECTIONS];

static void zeroConnection(struct HttpConnection* p)
{
    p->id           = 0;
    p->lastUsed     = 0;
    p->toDo         = 0;
    p->postComplete = false;
    p->delayUntil   = 0;
}

struct HttpConnection* HttpConnectionNew(int connectionId) //Never fails so never returns NULL
{
    struct HttpConnection* p;
    
    //Look for an existing connection
    for (p = connections; p < connections + MAX_CONNECTIONS; p++)
    {
        if (p->id == connectionId) goto end;
    }
    
    //look for an empty connection
    {
        struct HttpConnection* pOldest = 0;
        uint32_t ageOldest = 0;
        for (p = connections; p < connections + MAX_CONNECTIONS; p++)
        {
            if (!p->id) goto end;
            
            //Otherwise record the oldest and keep going
            uint32_t age = MsTimerCount - p->lastUsed;
            if (age >= ageOldest)
            {
                ageOldest = age;
                  pOldest = p;
            }
        }
    
        //No empty ones found so use the oldest
        p = pOldest;
    }
    
end:
    zeroConnection(p);
    p->id           = connectionId;
    p->lastUsed     = MsTimerCount;
    return p;
}
struct HttpConnection* HttpConnectionOrNull(int connectionId)
{
    for (struct HttpConnection* p = connections; p < connections + MAX_CONNECTIONS; p++)
    {
        if (p->id == connectionId)
        {
            p->lastUsed = MsTimerCount;
            return p;
        }
    }
    return NULL;
}
void HttpConnectionReset(int connectionId)
{
    for (struct HttpConnection* p = connections; p < connections + MAX_CONNECTIONS; p++)
    {
        if (p->id == connectionId) zeroConnection(p);
    }
}