Make all script validation flags backward compatible #10699

1. 
   sipa commented at 11:37 pm on June 28, 2017: member

   This change makes SCRIPT_VERIFY_UPGRADABLE_NOPS not apply to OP_CHECKLOCKTIMEVERIFY and OP_CHECKSEQUENCEVERIFY. This is a no-op as UPGRADABLE_NOPS is only set for mempool transactions, and those always have SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY and SCRIPT_VERIFY_CHECKSEQUENCEVERIFY set as well. The advantage is that setting more flags now always results in a reduction in acceptable scripts (=softfork).

   This results in a nice and testable property for validation, for which a new test is added.

   This also means that the introduction of a new definition for a NOP or witness version will likely need the following procedure (example OP_NOP8 here)

   • Remove OP_NOP8 from being affected by SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS.
   • Add a SCRIPT_VERIFY_DISCOURAGE_NOP8, which only applies to OP_NOP8.
   • Add a SCRIPT_VERIFY_NOP8 which implements the new consensus logic.
   • Before activation, add SCRIPT_VERIFY_DISCOURAGE_NOP8 to the mempool flags.
   • After activation, add SCRIPT_VERIFY_NOP8 to both the mempool and consensus flags.
2. fanquake added the label Validation on Jun 29, 2017
3. 
   TheBlueMatt commented at 11:12 pm on June 30, 2017: member

   Can you rebase this on top of the now-merged #10192 to remove the extra checks in its test? Concept ACK.
4. Make all script verification flags softforks 2851b77312
5. Add a test that all flags are softforks 2dd6f80680
6. Simplify tx validation tests 01013f5d2f
7. sipa force-pushed on Jun 30, 2017
8. 
   sipa commented at 11:19 pm on June 30, 2017: member

   Done.
9. 
   TheBlueMatt commented at 7:25 pm on July 3, 2017: member

   utACK 01013f5d2fbe3fa86565c927bf7bb8ec0f525073 I did check some of the test changes failed appropriately, but wouldnt really call it a tested ACK per se.
10. jl2012 approved
11. 
    jl2012 commented at 7:31 am on October 5, 2017: contributor

    utACK 01013f5
12. 
    laanwj commented at 2:01 pm on December 1, 2017: member

    utACK 2851b77312b55c8868acd4cd2c118e5a034606b7, reviewed both test and interpreter changes, they seem clear and contained and could discover no issues with the changed logic.
13. laanwj merged this on Dec 12, 2017
14. laanwj closed this on Dec 12, 2017

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Contributors
sipa TheBlueMatt jl2012 laanwj

Labels
Validation