From 54877253c807dac7a3720b2c3d1d989c410259a7 Mon Sep 17 00:00:00 2001 From: Sebastian Falbesoner Date: Thu, 11 May 2023 19:54:03 +0200 Subject: [PATCH] test: avoid sporadic MINIMALDATA failure in feature_taproot.py (fixes #27595) The functional test feature_taproot.py fails in some rare cases on the execution of the `"branched_codesep"` spending script. The problem occurs if the first data-push (having random content with a random length in the range [0, 510]) has a length of 1 and the single byte has value of [1...16] or [-1]; in this case, the data-push is not minimally encoded by test framework's CScript class (i.e. doesn't use the special op-codes OP_1...OP_16 or OP_1NEGATE) and the script interpreter throws an SCRIPT_ERR_MINIMALDATA error: ``` test_framework.authproxy.JSONRPCException: non-mandatory-script-verify-flag (Data push larger than necessary) (-26) ``` Background: The functional test framework's CScript class translates passed bytes/bytearrays always to data pushes using OP_PUSHx/OP_PUSHDATA{1,2,4} op-codes. E.g. the expression `CScript(bytes([1]))` yields `bytes([OP_PUSH1, 1])` instead of the minimal-encoded `bytes([OP_1])`. Fix this by adapting the random-size range to [2,...], i.e. never pass byte-arrays below length two to be pushed. Closes #27595. --- test/functional/feature_taproot.py | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/test/functional/feature_taproot.py b/test/functional/feature_taproot.py index 8be2040d916..34197a5c483 100755 --- a/test/functional/feature_taproot.py +++ b/test/functional/feature_taproot.py @@ -738,7 +738,11 @@ def spenders_taproot_active(): scripts = [ ("pk_codesep", CScript(random_checksig_style(pubs[1]) + bytes([OP_CODESEPARATOR]))), # codesep after checksig ("codesep_pk", CScript(bytes([OP_CODESEPARATOR]) + random_checksig_style(pubs[1]))), # codesep before checksig - ("branched_codesep", CScript([random_bytes(random.randrange(511)), OP_DROP, OP_IF, OP_CODESEPARATOR, pubs[0], OP_ELSE, OP_CODESEPARATOR, pubs[1], OP_ENDIF, OP_CHECKSIG])), # branch dependent codesep + ("branched_codesep", CScript([random_bytes(random.randrange(2, 511)), OP_DROP, OP_IF, OP_CODESEPARATOR, pubs[0], OP_ELSE, OP_CODESEPARATOR, pubs[1], OP_ENDIF, OP_CHECKSIG])), # branch dependent codesep + # Note that the first data push in the "branched_codesep" script has the purpose of + # randomizing the sighash, both by varying script size and content. In order to + # avoid MINIMALDATA script verification errors caused by not-minimal-encoded data + # pushes (e.g. `OP_PUSH1 1` instead of `OP_1`), we set a minimum data size of 2 bytes. ] random.shuffle(scripts) tap = taproot_construct(pubs[0], scripts)