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.

base/net/web-net4-ajax.c@127:bd6dd135009d, 2019-07-31 (annotated)

Committer:
andrewboyson
Date:
Wed Jul 31 15:09:15 2019 +0000
Revision:
127:bd6dd135009d
Parent:
110:8ab752842d25
Child:
142:b472ba95b018
Amalgamated Reply into Poll function

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 86:f3c9beec4ee7 1 #include <stdio.h>
andrewboyson 86:f3c9beec4ee7 2
andrewboyson 86:f3c9beec4ee7 3 #include "http.h"
andrewboyson 86:f3c9beec4ee7 4 #include "ar4.h"
andrewboyson 86:f3c9beec4ee7 5 #include "nr4.h"
andrewboyson 89:615fb951df69 6 #include "dhcp.h"
andrewboyson 86:f3c9beec4ee7 7
andrewboyson 103:91194cc19bbb 8 void WebNet4Ajax()
andrewboyson 86:f3c9beec4ee7 9 {
andrewboyson 86:f3c9beec4ee7 10 HttpOk("text/plain; charset=UTF-8", "no-cache", NULL, NULL);
andrewboyson 89:615fb951df69 11
andrewboyson 96:eb2eb75bad0f 12 HttpAddInt32AsHex(DhcpLocalIp); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 13 HttpAddText (DhcpDomainName); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 14 HttpAddText (DhcpHostName); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 15 HttpAddInt32AsHex(DhcpNtpIp); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 16 HttpAddInt32AsHex(DhcpDnsServerIp); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 17 HttpAddInt32AsHex(DhcpServerIp); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 18 HttpAddInt32AsHex(DhcpRouterIp); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 19 HttpAddInt32AsHex(DhcpSubnetMask); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 20 HttpAddInt32AsHex(DhcpBroadcastIp); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 21 HttpAddInt32AsHex(DhcpLeaseTime); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 22 HttpAddInt32AsHex(DhcpRenewalT1); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 23 HttpAddInt32AsHex(DhcpRenewalT2); HttpAddChar('\n');
andrewboyson 96:eb2eb75bad0f 24 HttpAddInt32AsHex(DhcpGetElapsedLife()); HttpAddChar('\n');
andrewboyson 89:615fb951df69 25 HttpAddChar('\f');
andrewboyson 89:615fb951df69 26
andrewboyson 88:2857259fc2b4 27 Ar4SendAjax();
andrewboyson 86:f3c9beec4ee7 28 HttpAddChar('\f');
andrewboyson 89:615fb951df69 29
andrewboyson 88:2857259fc2b4 30 Nr4SendAjax();
andrewboyson 86:f3c9beec4ee7 31 }