Andrew Boyson
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:
- 109:3e82f62c7e1f
- Child:
- 110:8ab752842d25
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/web.c Mon Apr 29 14:45:30 2019 +0000
@@ -0,0 +1,92 @@
+#include "http.h"
+#include "web-server-base.h"
+#include "web-base.h"
+#include "mstimer.h"
+
+#define LOGIN_DELAY_MS 200
+
+static void handleRequest(int size, char* pRequestStream, uint32_t positionInRequestStream, int* pToDo, bool* pPostComplete, uint32_t* pDelayUntil)
+{
+ //Handle request for the first packet of data received but leave todo the same after that.
+ int contentLength = 0;
+ int contentStart = 0;
+ if (size && positionInRequestStream == 0)
+ {
+ //Read the headers
+ char* pMethod;
+ char* pPath;
+ char* pQuery;
+ char* pLastModified;
+ char* pCookies;
+ contentStart = HttpRequestRead(pRequestStream, size, &pMethod, &pPath, &pQuery, &pLastModified, &pCookies, &contentLength);
+
+ //Ask the web server what to do
+ *pToDo = WebServerBaseDecideWhatToDo(pPath, pLastModified);
+
+ //If what to do is NOTHING, NOT_FOUND or NOT_MODIFIED then no query or post will be valid so stop now
+ if (*pToDo < DO_LOGIN) { *pPostComplete = true; return; }
+
+ //If what to do is LOGIN then the user has just returned the login form
+ if (*pToDo == DO_LOGIN)
+ {
+ WebServerBaseHandleQuery(*pToDo, pQuery); //Read the password and the original location
+ if (WebLoginQueryPasswordOk)
+ {
+ if (!WebLoginSessionIdIsSet()) //If there isn't a session id already
+ {
+ WebLoginSessionIdNew(); //Create a new session id
+ }
+ *pToDo = WebLoginOriginalToDo; //Load the original todo and SEND_SESSION_ID
+ *pToDo += DO_SEND_SESSION_ID;
+ }
+ *pDelayUntil = MsTimerCount + LOGIN_DELAY_MS; //To prevent brute forcing the hash delay the reply to the login
+ *pPostComplete = true;
+ return; //Either way no query or post will be valid
+ }
+
+ //Have a normal request so authenticate
+ if (!WebLoginCookiesContainValidSessionId(pCookies))
+ {
+ WebLoginOriginalToDo = *pToDo; //Record the original destination for redirection
+ *pToDo = DO_LOGIN;
+ *pPostComplete = true;
+ return; //Ignore any query or post as the user is not authenticated
+ }
+
+ //Handle the query
+ WebServerBaseHandleQuery(*pToDo, pQuery);
+ }
+
+ //Do the upload of anything that needs it. Todos it doesn't understand are ignored.
+ if (!*pPostComplete) *pPostComplete = WebServerBaseHandlePost(*pToDo, contentLength, contentStart, size, pRequestStream, positionInRequestStream);
+}
+
+static void sendReply(int todo)
+{
+ //Check if todo includes the need to send a cookie
+ if (todo >= DO_SEND_SESSION_ID)
+ {
+ HttpOkCookieName = WebLoginSessionNameGet();
+ HttpOkCookieValue = WebLoginSessionIdGet();
+ HttpOkCookieMaxAge = WebLoginSessionNameLife();
+ todo -= DO_SEND_SESSION_ID;
+ }
+ else
+ {
+ HttpOkCookieName = NULL;
+ HttpOkCookieValue = NULL;
+ HttpOkCookieMaxAge = -1;
+ }
+
+ WebServerBaseReply(todo);
+}
+
+int WebInit()
+{
+ HttpRequestFunction = handleRequest;
+ HttpReplyFunction = sendReply;
+
+ WebLoginInit();
+
+ return 0;
+}
\ No newline at end of file