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.

Diff: web.c

Revision:
127:bd6dd135009d
Parent:
125:772948168e4f
Child:
128:fc9708e1d17c
--- a/web.c	Mon May 27 10:13:45 2019 +0000
+++ b/web.c	Wed Jul 31 15:09:15 2019 +0000
@@ -116,24 +116,17 @@
     if (!pState->postComplete) handlePost(pState->toDo, contentLength, contentStart, size, pRequestStream, positionInRequestStream, &pState->postComplete);
 }
 
-static int pollSomethingToSend(char* pStateData, bool clientFinished) //returns 0 no; +1 yes; -1 finished; 
+static bool pollSomethingToSend(char* pStateData, bool clientFinished) //returns true if finished; false if not; 
 {
     struct state* pState = (struct state*)pStateData;
     
     if (!pState->toDo)
     {
-        if (clientFinished) return -1; //The client hasn't requested anything and never will so finish
-        else                return  0; //The client hasn't requested anything yet but still could
+        if (clientFinished) return true;  //The client hasn't requested anything and never will so finish
+        else                return false; //The client hasn't requested anything yet but still could
     }
-    if (!pState->postComplete               ) return 0; //Wait for the request (usually a POST) to finish
-    if (!MsTimerAbsolute(pState->delayUntil)) return 0; //Wait a while (usually after a LOGIN attempt)
-    
-    return 1; //Yep, set up anything (just TSL at the moment) then call sendReply
-}
-
-static bool sendReply(char* pStateData)
-{
-    struct state* pState = (struct state*)pStateData;
+    if (!pState->postComplete               ) return false; //Wait for the request (usually a POST) to finish
+    if (!MsTimerAbsolute(pState->delayUntil)) return false; //Wait a while (usually after a LOGIN attempt)
     
     int todo = pState->toDo; //Make a copy so that we don't modify todo in the state
 
@@ -161,7 +154,6 @@
 {
     HttpRequestFunction = handleRequest;
     HttpPollFunction    = pollSomethingToSend;
-    HttpReplyFunction   = sendReply;
     
     WebLoginInit();