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authorWladimir J. van der Laan <laanwj@gmail.com>2015-01-08 12:00:19 +0100
committerWladimir J. van der Laan <laanwj@gmail.com>2015-01-08 12:01:22 +0100
commit48e1765e2781541c0f8b0893b26d02f27eb5c444 (patch)
tree112a2d69a7b1bd0f60d088e90696e294a9a84861 /src/script
parente3f5727590f5a2bb65f1fc7688305fe440ef404d (diff)
parentda918ac06e0d064e9584959ab3d241d03500e972 (diff)
Merge pull request #5143
da918ac Make SCRIPT_VERIFY_CLEANSTACK a standardness requirement (Pieter Wuille) b6e03cc Add SCRIPT_VERIFY_CLEANSTACK (BIP62 rule 6) (Pieter Wuille) ae4151b No semantic change: reuse stack variable in P2SH evaluation (Pieter Wuille)
Diffstat (limited to 'src/script')
-rw-r--r--src/script/interpreter.cpp32
-rw-r--r--src/script/interpreter.h10
-rw-r--r--src/script/script_error.h1
-rw-r--r--src/script/standard.h3
4 files changed, 33 insertions, 13 deletions
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index e979f61f6e..d0f75ab672 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1098,7 +1098,6 @@ bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigne
return false;
if (stack.empty())
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
-
if (CastToBool(stack.back()) == false)
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
@@ -1109,24 +1108,37 @@ bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigne
if (!scriptSig.IsPushOnly())
return set_error(serror, SCRIPT_ERR_SIG_PUSHONLY);
- // stackCopy cannot be empty here, because if it was the
+ // Restore stack.
+ swap(stack, stackCopy);
+
+ // stack cannot be empty here, because if it was the
// P2SH HASH <> EQUAL scriptPubKey would be evaluated with
// an empty stack and the EvalScript above would return false.
- assert(!stackCopy.empty());
+ assert(!stack.empty());
- const valtype& pubKeySerialized = stackCopy.back();
+ const valtype& pubKeySerialized = stack.back();
CScript pubKey2(pubKeySerialized.begin(), pubKeySerialized.end());
- popstack(stackCopy);
+ popstack(stack);
- if (!EvalScript(stackCopy, pubKey2, flags, checker, serror))
+ if (!EvalScript(stack, pubKey2, flags, checker, serror))
// serror is set
return false;
- if (stackCopy.empty())
+ if (stack.empty())
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
- if (!CastToBool(stackCopy.back()))
+ if (!CastToBool(stack.back()))
return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
- else
- return set_success(serror);
+ }
+
+ // The CLEANSTACK check is only performed after potential P2SH evaluation,
+ // as the non-P2SH evaluation of a P2SH script will obviously not result in
+ // a clean stack (the P2SH inputs remain).
+ if ((flags & SCRIPT_VERIFY_CLEANSTACK) != 0) {
+ // Disallow CLEANSTACK without P2SH, as otherwise a switch CLEANSTACK->P2SH+CLEANSTACK
+ // would be possible, which is not a softfork (and P2SH should be one).
+ assert((flags & SCRIPT_VERIFY_P2SH) != 0);
+ if (stack.size() != 1) {
+ return set_error(serror, SCRIPT_ERR_CLEANSTACK);
+ }
}
return set_success(serror);
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
index 3c4e7d466a..8bf379ed89 100644
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -67,8 +67,14 @@ enum
// discouraged NOPs fails the script. This verification flag will never be
// a mandatory flag applied to scripts in a block. NOPs that are not
// executed, e.g. within an unexecuted IF ENDIF block, are *not* rejected.
- SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS = (1U << 7)
-
+ SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS = (1U << 7),
+
+ // Require that only a single stack element remains after evaluation. This changes the success criterion from
+ // "At least one stack element must remain, and when interpreted as a boolean, it must be true" to
+ // "Exactly one stack element must remain, and when interpreted as a boolean, it must be true".
+ // (softfork safe, BIP62 rule 6)
+ // Note: CLEANSTACK should never be used without P2SH.
+ SCRIPT_VERIFY_CLEANSTACK = (1U << 8),
};
uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);
diff --git a/src/script/script_error.h b/src/script/script_error.h
index 5c260327b6..6365680b29 100644
--- a/src/script/script_error.h
+++ b/src/script/script_error.h
@@ -43,6 +43,7 @@ typedef enum ScriptError_t
SCRIPT_ERR_SIG_HIGH_S,
SCRIPT_ERR_SIG_NULLDUMMY,
SCRIPT_ERR_PUBKEYTYPE,
+ SCRIPT_ERR_CLEANSTACK,
/* softfork safeness */
SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS,
diff --git a/src/script/standard.h b/src/script/standard.h
index dbeeace4d9..ac80193773 100644
--- a/src/script/standard.h
+++ b/src/script/standard.h
@@ -48,7 +48,8 @@ static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY
SCRIPT_VERIFY_STRICTENC |
SCRIPT_VERIFY_MINIMALDATA |
SCRIPT_VERIFY_NULLDUMMY |
- SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS;
+ SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS |
+ SCRIPT_VERIFY_CLEANSTACK;
/** For convenience, standard but not mandatory verify flags. */
static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;