RFE: Introduce privsep to secure OS and hidden service keys
I'm not sure if anything has been implemented to prevent running tor process to read hidden service private key after (not during) startup or to browse OS filesystems.
For example after heartbleed issue OpenBSD has implemented couple of another protection layers to restrict a running daemon using private keys to be read them after startup.
This is commit message from OpenBSD's relayd (load-balancer) so you can get an idea what is the reason:
''Introduce privsep for private keys:
Move RSA private keys to a new separate process instead of copying them to the relays. A custom RSA engine is used by the SSL/TLS code of the relay processes to send RSA private key encryption/decryption (also used for sign/verify) requests to the new "ca" processes instead of operating on the private key directly.
Each relay process gets its own related ca process. Setting "prefork 5" in the config file will spawn 10 processes (5 relay, 5 ca). This diff also reduces the default number of relay processes from 5 to 3 which should be suitable in most installations without a very heavy load.
Don't keep text versions of the keys in memory, parse them once and keep the binary representation. This might still be the case in OpenSSL's internals but will be fixed in the library.
This diff doesn't prevent something like "heartbleed" but adds an additional mitigation to prevent leakage of the private keys from the processes doing SSL/TLS.''
Thus it would be nice if tor would privsep so a new tor process could not access the key directly.
Privsep would also help people in the future to "sandbox" logical functionality of tor (eg. OpenBSD's pledge, seccomp etc...), so it would not be possible for example to browse whole OS filesystem etc. in the future.