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.

--- a/http/http.h	Tue Mar 31 11:46:01 2020 +0000
+++ b/http/http.h	Thu Apr 02 11:55:28 2020 +0000
@@ -8,7 +8,6 @@
 #define HTTP_HAVE_SOMETHING_TO_SEND  2
 
 extern void   HttpReset   (int connectionId);
-extern bool   HttpResponse(int connectionId, bool clientFinished, int* pWindowSize, char* pWindow, uint32_t windowPositionInStream);
 extern bool   HttpAdd     (int connectionId,                      int* pWindowSize, char* pWindow, uint32_t windowPositionInStream); //returns true if finished; false if not
 extern int    HttpPoll    (int connectionId, bool clientFinished);  //returns true if something to send; false if not
 extern void   HttpRequest (int connectionId,                      int   windowSize, char* pWindow, uint32_t windowPositionInStream);