Operating Systems 2019W Lecture 19

Video

Video for the lecture given on March 25, 2019 is now available.

Notes

Lecture 19
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TOCTTOU
Time of check to time of use

If a privileged program tries to modify a file owned by an unprivileged user, it is possible for it to be changed between the time it is checked to the time it is used (unless special care is taken).

lpr 8lgm vulnerability (look up)

Spectre and meltdown
 - information leak due to concurrency


Covert channels are when two processes (or other computational elements) communicate when they are supposed to be isolated.

kernel random number generator: combine hardware events with cryptographically secure pseudo random number generator (based on a cryptographic hash function)

clocks & security
 - replay attacks

 - high resolution clocks are dangerous