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.c

Committer:
andrewboyson
Date:
2019-09-24
Revision:
130:9a5b8fe308f1
Child:
134:3d0abf4cd097

File content as of revision 130:9a5b8fe308f1:

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

bool HttpGetTrace()
{
    return WebTrace;
}

void HttpReset(int connection)
{
    HttpConnectionReset(connection);
}
bool HttpResponse(int connection, bool clientFinished, int* pWindowSize, char* pWindow, uint32_t windowPositionInStream)
{
    int status = HttpPoll(connection, clientFinished);
    bool finished;
    switch (status)
    {
        case HTTP_WAIT:                   finished = false;             *pWindowSize = 0;                               break;
        case HTTP_FINISHED:               finished = true;              *pWindowSize = 0;                               break;
        case HTTP_HAVE_SOMETHING_TO_SEND: finished = HttpAdd(connection, pWindowSize, pWindow, windowPositionInStream); break;
    }
    return finished;
}
bool HttpAdd(int connectionId, int* pWindowSize, char* pWindow, uint32_t windowPositionInStream)
{
    HttpAddStart(windowPositionInStream, *pWindowSize, pWindow); //We have something to send so start the buffer
    *pWindowSize = 0;
    
    struct HttpConnection* pConnection = HttpConnectionOrNull(connectionId);
    if (!pConnection) return false; //Protects the gap between the connection being established and the request being started
    
    int todo = pConnection->toDo; //Make a copy so that we don't modify todo in the state
    
    WebAddResponse(todo);
    
    *pWindowSize = HttpAddLength();
    
    return !HttpAddFilled(); //If we haven't used a full buffer then we have finished
}
int HttpPoll(int connectionId, bool clientFinished)
{
    struct HttpConnection* pConnection = HttpConnectionOrNull(connectionId);
    if (!pConnection) return HTTP_WAIT; //Protects the gap between the connection being established and the request being started
    
    if (!pConnection->toDo)
    {
        if (clientFinished) return HTTP_FINISHED; //The client hasn't requested anything and never will so finish
        else                return HTTP_WAIT;     //The client hasn't requested anything yet but still could
    }
    if (!pConnection->postComplete               ) return HTTP_WAIT;  //Wait for the request (usually a POST) to finish
    if (!MsTimerAbsolute(pConnection->delayUntil)) return HTTP_WAIT;  //Wait a while (usually after a LOGIN attempt)
    
    return HTTP_HAVE_SOMETHING_TO_SEND;
}
void HttpRequest(int connectionId, int windowSize, char* pWindow, uint32_t windowPositionInStream)
{
    struct HttpConnection* pConnection;
    if (!windowPositionInStream)
    {
        pConnection = HttpConnectionNew(connectionId);
    }
    else
    {
        pConnection = HttpConnectionOrNull(connectionId);
        if (!pConnection)
        {
            LogTimeF("WebRequest - no connection corresponds to id %d\r\n", connectionId);
            return;
        }
    }
    
    pConnection->delayUntil = MsTimerCount; //Default to no delay unless modified;
    
    //Handle request for the first packet of data received but leave todo the same after that.
    int contentLength = 0;
    int contentStart  = 0;
    if (windowSize && windowPositionInStream == 0)
    {
        //Read the headers
        char* pMethod;
        char* pPath;
        char* pQuery;
        char* pLastModified;
        char* pCookies;
        contentStart = HttpRequestRead(pWindow, windowSize, &pMethod, &pPath, &pQuery, &pLastModified, &pCookies, &contentLength);
        
        //Ask the web server what to do
        pConnection->toDo = WebDecideWhatToDo(pPath, pLastModified);
        
        //Handle the query
        int stop = WebHandleQuery(pQuery, pCookies, &pConnection->toDo, &pConnection->delayUntil); //return -1 on stop; 0 on continue
        if (stop)
        {
            pConnection->postComplete = true;
            return;
        }
    }
    
    //Do the upload of anything that needs it. Todos it doesn't understand are ignored.
    if (!pConnection->postComplete) WebHandlePost(pConnection->toDo, contentLength, contentStart, windowSize, pWindow, windowPositionInStream, &pConnection->postComplete);
}