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/httpadd.c

Committer:
andrewboyson
Date:
2019-09-24
Revision:
130:9a5b8fe308f1
Child:
159:bda5b89e8c19

File content as of revision 130:9a5b8fe308f1:

#include <time.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdarg.h>

static uint32_t currentPositionInMessage;
static uint32_t bufferPositionInMessage;
static int bufferLength;
static char* pBuffer;
static char* p;

void HttpAddStart(uint32_t position, int mss, char *pData)
{
    currentPositionInMessage = 0;
    bufferPositionInMessage = position;
    bufferLength = mss;
    pBuffer = pData;
    p       = pData;
}
int HttpAddLength()
{
    return p - pBuffer;
}
bool HttpAddFilled()
{
    return p - pBuffer >= bufferLength;
}

void HttpAddChar(char c)
{
    //Add character if the current position is within the buffer
    if (currentPositionInMessage >= bufferPositionInMessage &&
        currentPositionInMessage <  bufferPositionInMessage + bufferLength) *p++ = c;
    
    currentPositionInMessage++;
}

void HttpAddFillChar (char c, int length)
{
    while (length > 0)
    {
        HttpAddChar(c);
        length--;
    }
}
int  HttpAddText  (const char* text)
{
    const char* start = text;
    while (*text)
    {
        HttpAddChar(*text);
        text++;
    }
    return text - start;
}
int  HttpAddV     (char *fmt, va_list argptr)
{
    int size  = vsnprintf(NULL, 0, fmt, argptr); //Find the size required
    char text[size + 1];                         //Allocate enough memory for the size required with an extra byte for the terminating null
    vsprintf(text, fmt, argptr);                 //Fill the new buffer
    return HttpAddText(text);                    //Add the text
}
int  HttpAddF     (char *fmt, ...)
{
    va_list argptr;
    va_start(argptr, fmt);
    int size = HttpAddV(fmt, argptr);
    va_end(argptr);
    return size;
}
void HttpAddData  (const char* data, int length)
{
    while (length > 0)
    {
        HttpAddChar(*data);
        data++;
        length--;
    }
}
void HttpAddStream(void (*startFunction)(void), int (*enumerateFunction)(void))
{
    startFunction();
    while (true)
    {
        int c = enumerateFunction();
        if (c == EOF) break;
        HttpAddChar(c);
    }
}
void HttpAddNibbleAsHex(int nibble)
{
    nibble &= 0x0F;
    char c;
    if      (nibble < 0x0A) c = nibble + '0';
    else if (nibble < 0x10) c = nibble - 0xA + 'A';
    else                    c = '0';
    HttpAddChar(c);
}
void HttpAddByteAsHex(int value)
{
    HttpAddNibbleAsHex(value >> 4);
    HttpAddNibbleAsHex(value >> 0);
}
void HttpAddInt12AsHex(int value)
{   
    HttpAddNibbleAsHex(value >> 8);
    HttpAddNibbleAsHex(value >> 4);
    HttpAddNibbleAsHex(value >> 0);
}
void HttpAddInt16AsHex(int value)
{   
    HttpAddNibbleAsHex(value >> 12);
    HttpAddNibbleAsHex(value >>  8);
    HttpAddNibbleAsHex(value >>  4);
    HttpAddNibbleAsHex(value >>  0);
}
void HttpAddInt32AsHex(int value)
{   
    HttpAddNibbleAsHex(value >> 28);
    HttpAddNibbleAsHex(value >> 24);
    HttpAddNibbleAsHex(value >> 20);
    HttpAddNibbleAsHex(value >> 16);
    HttpAddNibbleAsHex(value >> 12);
    HttpAddNibbleAsHex(value >>  8);
    HttpAddNibbleAsHex(value >>  4);
    HttpAddNibbleAsHex(value >>  0);
}
void HttpAddInt64AsHex(int64_t value)
{   
    HttpAddNibbleAsHex(value >> 60);
    HttpAddNibbleAsHex(value >> 56);
    HttpAddNibbleAsHex(value >> 52);
    HttpAddNibbleAsHex(value >> 48);
    HttpAddNibbleAsHex(value >> 44);
    HttpAddNibbleAsHex(value >> 40);
    HttpAddNibbleAsHex(value >> 36);
    HttpAddNibbleAsHex(value >> 32);
    HttpAddNibbleAsHex(value >> 28);
    HttpAddNibbleAsHex(value >> 24);
    HttpAddNibbleAsHex(value >> 20);
    HttpAddNibbleAsHex(value >> 16);
    HttpAddNibbleAsHex(value >> 12);
    HttpAddNibbleAsHex(value >>  8);
    HttpAddNibbleAsHex(value >>  4);
    HttpAddNibbleAsHex(value >>  0);
}
void HttpAddBytesAsHex(const uint8_t* value, int size)
{
    int i = 0;
    while(true)
    {
        HttpAddByteAsHex(value[i]);
        i++;
        if (i >= size) break;
        if (i % 16 == 0) HttpAddText("\r\n");
        else             HttpAddChar(' ');
    }
}
void HttpAddBytesAsHexRev(const uint8_t* value, int size)
{
    int i = 0;
    while(true)
    {
        HttpAddByteAsHex(value[size - i - 1]);
        i++;
        if (i >= size) break;
        if (i % 16 == 0) HttpAddText("\r\n");
        else             HttpAddChar(' ');
    }
}
void HttpAddTm(struct tm* ptm)
{
    HttpAddF("%d-%02d-%02d ", ptm->tm_year + 1900, ptm->tm_mon + 1, ptm->tm_mday);
    switch(ptm->tm_wday)
    {
        case  0: HttpAddText("Sun"); break;
        case  1: HttpAddText("Mon"); break;
        case  2: HttpAddText("Tue"); break;
        case  3: HttpAddText("Wed"); break;
        case  4: HttpAddText("Thu"); break;
        case  5: HttpAddText("Fri"); break;
        case  6: HttpAddText("Sat"); break;
        default: HttpAddText("???"); break;
    }
    HttpAddF(" %02d:%02d:%02d", ptm->tm_hour, ptm->tm_min, ptm->tm_sec);
    if      (ptm->tm_isdst  > 0) HttpAddText(" BST");
    else if (ptm->tm_isdst == 0) HttpAddText(" GMT");
    else                         HttpAddText(" UTC");
}