Left sig != right sig. Signature check failure. message occurs very frequently - follow up to 6288

Description

While testing #6288 I noticed that I very frequently got the Left sig != right sig. Signature check failure. message in the terminal. This results in not all ballots being sent out, so not all BAT is properly distributed.

Steps to Reproduce

1. enable rewards with short contribution interval on staging. I also launched with --enable-logging=stderr --vmodule=*rewards*=6 to see log messages.
2. claim grant (30 BAT)
3. set AC amount to Up to 20 BAT
4. add verified and non verified publishers to AC table
5. add verified recurring tips in this order (5, 10, 10, 10, 1)
6. wait for monthly contribution to trigger
7. you should see 26 BAT goes through for monthly and 4 BAT from AC
8. Watch terminal.

• for simplicity, all verified publishers used belonged to the same publisher email

Actual result:

See several Left sig != right sig. Signature check failure. messages. Watch publisher account. Not all BAT is distributed as expected.

Expected result:

No Left sig != right sig. Signature check failure. messages

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.73.8 Chromium: 78.0.3904.50 (Official Build) nightly (64-bit)
Revision	2accdc52c79976e264cd2694df6db31d1fccd8e8-refs/branch-heads/3904@{#658}
OS	macOS Version 10.13.6 (Build 17G5019)

Version/Channel Information:

• Can you reproduce this issue with the current release? unsure
• Can you reproduce this issue with the beta channel? unsure
• Can you reproduce this issue with the dev channel? unsure
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

cc @NejcZdovc @rebron @brave/legacy_qa

[jhoneycutt]

This appears to be caused by braveledger_contribution::PhaseTwo::PrepareBatchCallback overwriting an existing prepareBallot object with an object for a different viewingId. I believe that the check there for ballots[i].proofBallot_.empty() is a typo and should be ballots[i].prepareBallot_.empty()

[LaurenWags]

Verified passed with

Brave	0.71.113 Chromium: 78.0.3904.87 (Official Build) (64-bit)
Revision	20c21f4010010f32462ea8e1d6af30cef66d48c8-refs/branch-heads/3904@{#840}
OS	macOS Version 10.13.6 (Build 17G5019)

• Verified test plan from https://github.com/brave/brave-core/pull/3819 (restored a wallet with 30 BAT).
  • Confirmed expected BAT was sent to my publisher accts (unable to confirm all test accts, as not all pub accts belong to me).
  • Confirmed that the batch section of ledger_state was empty as per https://github.com/brave/brave-browser/issues/6545#issuecomment-545431916 .
  • Confirmed no Left sig != right sig message was observed.
• Verified test plan from https://github.com/brave/brave-core/pull/3819 except modified by using a staging grant for 17.5 BAT instead. In step 5, my tips were set up as 5, 10, 10, 1 due to lower wallet balance. In step 7, 16 BAT was contributed from monthly tips and 1.5 BAT from AC.
  • Confirmed expected BAT was sent to my publisher accts (unable to confirm all test accts, as not all pub accts belong to me).
  • Confirmed that the batch section of ledger_state was empty as per https://github.com/brave/brave-browser/issues/6545#issuecomment-545431916 .
  • Confirmed no Left sig != right sig message was observed.

Verification passed on

Brave	0.71.114 Chromium: 78.0.3904.97 (Official Build) (64-bit)
Revision	021b9028c246d820be17a10e5b393ee90f41375e-refs/branch-heads/3904@{#859}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified test plan from https://github.com/brave/brave-core/pull/3819 except modified by using a staging grant for 17.5 BAT instead. In step 5, my tips were set up as 5, 10, 10, 1 due to lower wallet balance. In step 7, 16 BAT was contributed from monthly tips and 1.5 BAT from AC.
  • Confirmed expected BAT was sent to my publisher accts (unable to confirm all test accts, as not all pub accts belong to me).
  • Confirmed that the batch section of ledger_state was empty as per https://github.com/brave/brave-browser/issues/6545#issuecomment-545431916 .
  • Confirmed no Left sig != right sig message was observed.

Verification passed on

Brave	0.71.114 Chromium: 78.0.3904.97 (Official Build) (64-bit)
Revision	021b9028c246d820be17a10e5b393ee90f41375e-refs/branch-heads/3904@{#859}
OS	Ubuntu 18.04 LTS

• Verified test plan from https://github.com/brave/brave-core/pull/3819 except modified by using a staging grant for 17.5 BAT instead. In step 5, my tips were set up as 5, 10, 10, 1 due to lower wallet balance. In step 7, 16 BAT was contributed from monthly tips and 1.5 BAT from AC.
  • Confirmed expected BAT was sent to my publisher accts (unable to confirm all test accts, as not all pub accts belong to me).
  • Confirmed that the batch section of ledger_state was empty as per https://github.com/brave/brave-browser/issues/6545#issuecomment-545431916 .
  • Confirmed no Left sig != right sig message was observed.