On 3 April 2017 at 13:04, George Kadianakis desnacked@riseup.net wrote:
I'm calling it weird because I'm not sure how an attacker can profit from being able to provide two addresses that correspond to the same key, but I can probably come up with a few scenarios if I think about it.
Hi George!
I'll agree it's a weird edge case :-)
I think the reason my spider-sense is tingling is because years of cleaning up after intrusions has taught me that sysadmins and human beings are very bad at non-canonical address formats, especially where they combine them with either blacklisting, or else case-statements-with-default-conditions.
If one creates scope for saying "the address is <foo>.onion but you can actually use <foo'>.onion or <foo''>.onion which are equivalent" - then someone will somehow leverage that either a) for hackery, or b) for social engineering.
Compare:
* http://017700000001 * http://2130706433 * http://0177.0.0.1 <- this one tends to surprise people * http://127.0.0.1
…and the sort of fun shenanigans that can be done with those "equivalent forms"
People who've been trained not to type [X] into their browser, might be convinced to type [X']
It's a lot easier for people to cope with there being one-and-only-one viable form for any given hostname or address-representation.
-a