Reproduce attack and implement fix for liveness issue with ABA/commoncoin

[sbellem]

Addresses amiller/HoneyBadgerBFT#59:

• The constructive attack proposed by MacBrough should be reflected in the test cases
• the ABA implementation must be modified to reflect the new fix

NOTES

The adversarial network scheduler is currently limited to the minimal case of 4 nodes with one node being the attacker.

Modifying the network scheduler to support multiple nodes should not be too difficult, and is currently work in progress.

Logging was added for troubleshooting purposes. It is currently only meant to be used when testing, and future work will extend this work so that logging is available when the application is run in real scenarios.

Reproducing the Attack

Run:

$ pytest -v -m demo test/demo_attack_issue59.py -s

[codecov-io]

Codecov Report

Merging #12 into dev will decrease coverage by 0.01778%.
The diff coverage is 98.24561%.

@@                 Coverage Diff                 @@
##                 dev         #12         +/-   ##
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- Coverage   98.50917%   98.49138%   -0.01779%     
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  Files             18          18                 
  Lines            872         928         +56     
  Branches         122         130          +8     
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+ Hits             859         914         +55     
  Misses            11          11                 
- Partials           2           3          +1

[amiller]

Are environment variables documented anywhere?

[amiller]

Is there any reason to disable the conf phase except for testing?

[sbellem]

I'll remove the switch. It was put there temporarily to ease the demonstration of the attack.

By putting the CONF phase logic in a function we could also simply mock that function in order to demonstrate the attack.

[sbellem]

@amiller The CONF_PHASE env var was removed and instead a separate "demo" test was written (commits 6842b7b & 09fec40).

This test should demonstrate the liveness issue, and consequently should only be invoked for demonstration purposes. Consequently invoking the test requires passing the option -m demo to pytest and also explicitly selecting the file. That is:

pytest -v -m demo test/demo_attack_issue59.py -s

So, the following two alternatives won't work:

# file not picked up by default because it does not start with "test_"
pytest -v -m demo -s

# option "-m demo" missing
pytest -v test/demo_attack_issue59.py -s

[amiller]

This looks ready to go to me.