[tor-dev] Tor's default behavior for ed25519 identities

[s7r]

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>> Thanks; this is incredibly helpful!
> 
>> I've started a branch to do a test case to demonstrate all these
>>  bugs ; it's called "ed25519_keygen" in my public repository.  It
>>  also adds a couple more features to '--keygen'.  It does cases 
>> 2...4 so far; I want to make it cover 5..10.
> 
>> Once I've got it demonstrating all the cases, I'll try to clean 
>> it up and start hammering down the bugs.
>> 


Finished tests on branch ed25519_keygen, commit: b71dafcb3358fac7

Things are indeed much much better. I am sending you the new
(hopefully last) cases which need adjustments. Note that the case
numbers do not match the ones in my previous email, since I am
completely removing the cases where now Tor does what it should.

We have cases with two possible status codes:
LOG MESSAGE - where we need to change the log message and not die with
[err] do_main_loop(): Bug: - I am also trying to provide suggestions
for log messages, but we certainly need to improve them.

DEFECT - where we also need to adjust the behavior (only one defect
fortunately).

- ----------------------------------------------------------

1. If ed25519_master_id_secret_key is missing or encrypted and we only
have ed25519_master_id_public_key available in $datadirectory/keys (no
ed25519_signing_cert and 25519_signing_secret_key):

What Tor should do:
- - Don't start at all and print log messages requiring user action.

What Tor currently does:
- - Doesn't start at all:
Aug 06 15:15:01.000 [warn] We needed to load a secret key from
/root/torsrc/data/keys/ed25519_master_id_secret_key, but couldn't find it.
Aug 06 15:15:01.000 [warn] Missing identity key
Aug 06 15:15:01.000 [err] do_main_loop(): Bug: Error initializing
keys; exiting (on Tor 0.2.7.2-alpha-dev b71dafcb3358fac7)

The behavior is correct, it detects the file
ed25519_master_id_public_key, it doesn't see ed25519_signing_cert and
ed25519_signing_secret_key so it tries to look for
ed25519_master_id_secret_key (unencrypted) for generating them.

STATUS: LOG MESSAGE
 -> Change the log message, it is not a bug: Failed to start: Missing
a valid signing key and certificate. Please generate manually a valid
signing key and certificate and move them to $datadirectory/keys or
move the plaintext (unencrypted) master key in $datadirectory/keys so
Tor can do this automatically.
- ----------------------------------------------------------

2. If only ed25519_master_id_secret_key_encrypted exists in
$datadirectory/keys (ed25519_master_id_public_key,
ed25519_signing_secret_key and ed25519_signing_cert are missing):

What Tor should do:
- - We assume the relay identity existed previously and
ed25519_master_id_secret_key_encrypted was restored form a backup. Do
not start Tor at all and print explicit warnings that action is
required - Tor cannot decrypt the
ed25519_master_id_secret_key_encrypted file. Generate
ed25519_master_id_public_key, ed25519_signing_secret_key and
ed25519_signing_cert or decrypt the
ed25519_master_id_secret_key_encrypted in $datadirectory/keys so Tor
can do it by itself.

What Tor currently does:
- - Doesn't start:
Aug 06 15:03:25.000 [warn] Found an encrypted secret key, but not
public key file /root/torsrc/data/keys/ed25519_master_id_public_key!
Aug 06 15:03:25.000 [warn] Missing identity key
Aug 06 15:03:25.000 [err] do_main_loop(): Bug: Error initializing
keys; exiting (on Tor 0.2.7.2-alpha-dev b71dafcb3358fac7)

ed25519_master_id_public_key missing is not the issue here, the issue
is actually not finding valid ed25519_signing_cert and
ed25519_signing_secret_key.

STATUS: LOG MESSAGE
 -> Change the log message, it is not a bug: Failed to start: The
master key in $datadirectory/keys is encrypted and we don't have a
valid signing key and certificate. Please generate manually a valid
signing key and certificate and move them to $datadirectory/keys or
move the plaintext (unencrypted) master key in $datadirectory/keys so
Tor can do this automatically.
- ----------------------------------------------------------

3. If ed25519_master_id_secret_key_encrypted and
ed25519_master_id_public_key both exist in $datadirectory/keys
(ed25519_signing_secret_key and ed25519_signing_cert are missing):

What Tor should do:
- - We assume the relay identity existed previously and
ed25519_master_id_secret_key_encrypted was restored form a backup. Do
not start Tor at all and print explicit warnings that action is
required - Tor cannot decrypt the
ed25519_master_id_secret_key_encrypted file. Generate
ed25519_master_id_public_key, ed25519_signing_secret_key and
ed25519_signing_cert or decrypt the
ed25519_master_id_secret_key_encrypted in $datadirectory/keys so Tor
can do it by itself.

STATUS: LOG MESSAGE
 -> Change the log message, it is not a bug: Failed to start: The
master key in $datadirectory/keys is encrypted and we don't have a
valid signing key and certificate. Please generate manually a valid
signing key and certificate and move them to $datadirectory/keys or
move the plaintext (unencrypted) master key in $datadirectory/keys so
Tor can do this automatically.
- ----------------------------------------------------------

4. If only valid ed25519_signing_secret_key and valid
ed25519_signing_cert exist in $datadirectory/keys
(ed25519_master_id_secret_key and ed25519_master_id_public_key missing):

What Tor should do:
- - Compute ed25519_master_id_public_key from
ed25519_signing_secret_key, validate and start. Proceed as normal
after (regenerate automatically after expiration if master key
unencrypted is still available).

What Tor currently does:
- - It starts (this is good), but does not compute and save to disk
ed25519_master_id_public_key from ed25519_signing_cert:

Aug 06 15:33:21.000 [warn] No key found in
/root/torsrc/data/keys/ed25519_master_id_secret_key or
/root/torsrc/data/keys/ed25519_master_id_public_key.
Aug 06 15:33:21.000 [warn] Master public key was absent; inferring
from public key in signing certificate

STATUS: DEFECT
 -> Tor should also save to disk in $datadirectory/keys
ed25519_master_id_public_key (computed from ed25519_signing_cert) not
just start, in order to avoid future warnings for the same reason.

We have to compute and save to disk *ed25519_master_id_public_key of
ed25519_master_id_secret_key*, not the public key of
ed25519_signing_secret_key.
- ----------------------------------------------------------

5. If we have in $datadirectory/keys an ed25519_master_id_secret_key
and ed25519_master_id_public_key which doesn't belong to the secret key:

What Tor should do:
- - Don't start at all - something is obviously wrong and user has to
clean it up.

What Tor currently does:
- -  Doesn't start:
Aug 06 15:45:36.000 [warn]
/root/torsrc/data/keys/ed25519_master_id_public_key does not match
/root/torsrc/data/keys/ed25519_master_id_secret_key!
Aug 06 15:45:36.000 [warn] Missing identity key
Aug 06 15:45:36.000 [err] do_main_loop(): Bug: Error initializing
keys; exiting (on Tor 0.2.7.2-alpha-dev b71dafcb3358fac7)

STATUS: LOG MESSAGE
 -> Change the log message, it is not a bug: Failed to start: The
ed25519_master_id_public_key and ed25519_master_id_secret_key do not
match. If you are trying to restore this relay from a backup, make
sure you didn't accidentally mix the key files. If you are sure the
ed25519_master_id_secret_key is the right identity file for this
relay, delete ed25519_master_id_public_key.
- ----------------------------------------------------------

6. ed25519_signing_cert and ed25519_signing_secret_key are valid but
do not validate against ed25519_master_id_public_key:

What Tor should do:
- - Don't start at all - something is wrong.

What Tor currently does:
- - Doesn't start:
Aug 06 15:54:20.000 [warn] The signing cert we have was not signed
with the master key we loaded!
Aug 06 15:54:20.000 [err] do_main_loop(): Bug: Error initializing
keys; exiting (on Tor 0.2.7.2-alpha-dev b71dafcb3358fac7)

STATUS: LOG MESSAGE
 -> Change the log message, it is not a bug: Change the log message,
not a bug: Failed to start: The certificate was not signed with the
master key we loaded! Maybe we have in $datadirectory/keys the signing
key and certificate generated with another relay's master key, please
double check!
- ----------------------------------------------------------

7. Only expired ed25519_signing_cert and ed25519_signing_secret_key:

What Tor should do:
- - Don't start.

What Tor currently does:
- - Doesn't start:
Aug 06 15:48:56.000 [warn] No key found in
/root/torsrc/data/keys/ed25519_master_id_secret_key or
/root/torsrc/data/keys/ed25519_master_id_public_key.
Aug 06 15:48:56.000 [warn] Missing identity key
Aug 06 15:48:56.000 [err] do_main_loop(): Bug: Error initializing
keys; exiting (on Tor 0.2.7.2-alpha-dev b71dafcb3358fac7)

The behavior is correct, Tor first checks the certificate's expiration
date, sees that it is expired and proceeds looking for
ed25519_master_id_secret_key unencrypted to generate fresh new cert
and key (very good).

STATUS: LOG MESSAGE
 -> Change the log message, it is not a bug: Failed to start: the
signing key and certificate are expired. Generate a fresh valid
signing key and certificate and move them to $datadirectory/keys or
move the ed25519_master_id_secret_key unencrypted to
$datadirectory/keys so Tor can do this automatically.
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