Added constant time string comparison to avoid possible time-based attacks. #3836
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igrr
reviewed
Nov 15, 2017
libraries/ArduinoOTA/ArduinoOTA.h
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| @@ -93,6 +93,7 @@ class ArduinoOTAClass | |||
| void _onRx(void); | |||
| int parseInt(void); | |||
| String readStringUntil(char end); | |||
| bool constantTimeEquals(const String &string1, const String &string2); | |||
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Suggestion: can this method be moved into String class, so reuse in other places is possible?
libraries/ArduinoOTA/ArduinoOTA.cpp
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| // Preliminary check | ||
| if(string1.length() != string2.length()) { | ||
| return false; |
libraries/ArduinoOTA/ArduinoOTA.cpp
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| bool equals = true; | ||
| unsigned int len = string1.length(); | ||
| for(unsigned int i = 0; i < len; i++){ | ||
| equals &= (string1.charAt(i) == string2.charAt(i)); |
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It would be interesting to see the generated code for this loop at -O2 optimization level... I wonder whether the compiler is smart enough to convert this 'and' into 'branch-if-zero'.
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I agree. Maybe better to write not so easily optimizable code. Ill think about that
…unction body to assure constant time comparison despite compiler optimizations
# Conflicts: # libraries/ArduinoOTA/ArduinoOTA.cpp
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@igrr tried to met all your requests |
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Except for my two nitpick cleanups, this looks good to me. |
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This should still be tested more thoroughly, but after careful inspection, the code looks good, so merging. |
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This should resolve #1127.