pppd: Check challenge length from peer in CHAPMS and CHAPMS-v2 challe… - #630
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…nges Instead of assuming the challenge is the right length, check that it is at least the expected length, and return a 0-length response if it isn't. Previously we would read past the end of the challenge, which was in the received packet in inpacket_buf[]. Thus the extra bytes read would have been either zeroes or bytes from previous received packets, so there was no information disclosure to the peer of anything that it didn't already know. Nevertheless we should be careful. Thanks to leegihyoung45@gmail.com for finding and reporting this. Also add a comment and checks in ascii2unicode() on the value of ascii_len. Because it always comes from get_secret(), the checks will never trigger, but it is better to be defensive. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
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…nges
Instead of assuming the challenge is the right length, check that it is at least the expected length, and return a 0-length response if it isn't. Previously we would read past the end of the challenge, which was in the received packet in inpacket_buf[]. Thus the extra bytes read would have been either zeroes or bytes from previous received packets, so there was no information disclosure to the peer of anything that it didn't already know. Nevertheless we should be careful.
Thanks to leegihyoung45@gmail.com for finding and reporting this.
Also add a comment and checks in ascii2unicode() on the value of ascii_len. Because it always comes from get_secret(), the checks will never trigger, but it is better to be defensive.