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petertoddpetertodd
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Add rejection of non-null CHECKMULTISIG dummy values
This is a source of transaction mutability as the dummy value was previously not checked and could be modified to something other than the usual OP_0 value.
1 parent 29c1749 commit 6380180

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5 files changed

+63
-5
lines changed

5 files changed

+63
-5
lines changed

‎src/script.cpp‎

Lines changed: 15 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -934,8 +934,22 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, co
934934
fSuccess = false;
935935
}
936936

937-
while (i-- > 0)
937+
// Clean up stack of actual arguments
938+
while (i-- > 1)
938939
popstack(stack);
940+
941+
// A bug causes CHECKMULTISIG to consume one extra argument
942+
// whose contents were not checked in any way.
943+
//
944+
// Unfortunately this is a potential source of mutability,
945+
// so optionally verify it is exactly equal to zero prior
946+
// to removing it from the stack.
947+
if (stack.size() < 1)
948+
return false;
949+
if ((flags & SCRIPT_VERIFY_NULLDUMMY) && stacktop(-1).size())
950+
return error("CHECKMULTISIG dummy argument not null");
951+
popstack(stack);
952+
939953
stack.push_back(fSuccess ? vchTrue : vchFalse);
940954

941955
if (opcode == OP_CHECKMULTISIGVERIFY)

‎src/script.h‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -42,6 +42,7 @@ enum
4242
SCRIPT_VERIFY_STRICTENC = (1U << 1), // enforce strict conformance to DER and SEC2 for signatures and pubkeys
4343
SCRIPT_VERIFY_EVEN_S = (1U << 2), // enforce even S values in signatures (depends on STRICTENC)
4444
SCRIPT_VERIFY_NOCACHE = (1U << 3), // do not store results in signature cache (but do query it)
45+
SCRIPT_VERIFY_NULLDUMMY = (1U << 4), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
4546
};
4647

4748
// Mandatory script verification flags that all new blocks must comply with for
@@ -54,7 +55,8 @@ static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;
5455
// with. However scripts violating these flags may still be present in valid
5556
// blocks and we must accept those blocks.
5657
static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
57-
SCRIPT_VERIFY_STRICTENC;
58+
SCRIPT_VERIFY_STRICTENC |
59+
SCRIPT_VERIFY_NULLDUMMY;
5860

5961
enum txnouttype
6062
{

‎src/test/data/tx_invalid.json‎

Lines changed: 28 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -67,11 +67,38 @@
6767
["0000000000000000000000000000000000000000000000000000000000000200", 0, "0x21 0x035e7f0d4d0841bcd56c39337ed086b1a633ee770c1ffdd94ac552a95ac2ce0efc CHECKSIG"]],
6868
"01000000020001000000000000000000000000000000000000000000000000000000000000000000004948304502203a0f5f0e1f2bdbcd04db3061d18f3af70e07f4f467cbc1b8116f267025f5360b022100c792b6e215afc5afc721a351ec413e714305cb749aae3d7fee76621313418df10101000000000200000000000000000000000000000000000000000000000000000000000000000000484730440220201dc2d030e380e8f9cfb41b442d930fa5a685bb2c8db5906671f865507d0670022018d9e7a8d4c8d86a73c2a724ee38ef983ec249827e0e464841735955c707ece98101000000010100000000000000015100000000", "P2SH"],
6969

70-
["Incorrect signature order"],
70+
["CHECKMULTISIG with incorrect signature order"],
7171
["Note the input is just required to make the tester happy"],
7272
[[["b3da01dd4aae683c7aee4d5d8b52a540a508e1115f77cd7fa9a291243f501223", 0, "HASH160 0x14 0xb1ce99298d5f07364b57b1e5c9cc00be0b04a954 EQUAL"]],
7373
"01000000012312503f2491a2a97fcd775f11e108a540a5528b5d4dee7a3c68ae4add01dab300000000fdfe000048304502207aacee820e08b0b174e248abd8d7a34ed63b5da3abedb99934df9fddd65c05c4022100dfe87896ab5ee3df476c2655f9fbe5bd089dccbef3e4ea05b5d121169fe7f5f401483045022100f6649b0eddfdfd4ad55426663385090d51ee86c3481bdc6b0c18ea6c0ece2c0b0220561c315b07cffa6f7dd9df96dbae9200c2dee09bf93cc35ca05e6cdf613340aa014c695221031d11db38972b712a9fe1fc023577c7ae3ddb4a3004187d41c45121eecfdbb5b7210207ec36911b6ad2382860d32989c7b8728e9489d7bbc94a6b5509ef0029be128821024ea9fac06f666a4adc3fc1357b7bec1fd0bdece2b9d08579226a8ebde53058e453aeffffffff0180380100000000001976a914c9b99cddf847d10685a4fabaa0baf505f7c3dfab88ac00000000", "P2SH"],
7474

75+
76+
["The following is a tweaked form of 23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63"],
77+
["It is an OP_CHECKMULTISIG with the dummy value missing"],
78+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
79+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004847304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH"],
80+
81+
82+
["CHECKMULTISIG SCRIPT_VERIFY_NULLDUMMY tests:"],
83+
84+
["The following is a tweaked form of 23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63"],
85+
["It is an OP_CHECKMULTISIG with the dummy value set to something other than an empty string"],
86+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
87+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004a010047304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH,NULLDUMMY"],
88+
89+
["As above, but using a OP_1"],
90+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
91+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba26000000000495147304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH,NULLDUMMY"],
92+
93+
["As above, but using a OP_1NEGATE"],
94+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
95+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba26000000000494f47304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH,NULLDUMMY"],
96+
97+
["As above, but with the dummy byte missing"],
98+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
99+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004847304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH,NULLDUMMY"],
100+
101+
75102
["Empty stack when we try to run CHECKSIG"],
76103
[[["ad503f72c18df5801ee64d76090afe4c607fb2b822e9b7b63c5826c50e22fc3b", 0, "0x21 0x027c3a97665bf283a102a587a62a30a0c102d4d3b141015e2cae6f64e2543113e5 CHECKSIG NOT"]],
77104
"01000000013bfc220ec526583cb6b7e922b8b27f604cfe0a09764de61e80f58dc1723f50ad0000000000ffffffff0101000000000000002321027c3a97665bf283a102a587a62a30a0c102d4d3b141015e2cae6f64e2543113e5ac00000000", "P2SH"],

‎src/test/data/tx_valid.json‎

Lines changed: 16 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -13,9 +13,23 @@
1313
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba26000000000490047304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH"],
1414

1515
["The following is a tweaked form of 23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63"],
16-
["It has an arbitrary extra byte stuffed into the signature at pos length - 2"],
16+
["It is an OP_CHECKMULTISIG with an arbitrary extra byte stuffed into the signature at pos length - 2"],
17+
["The dummy byte is fine however, so the NULLDUMMY flag should be happy"],
1718
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
18-
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004A0048304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2bab01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH"],
19+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004A0048304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2bab01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH,NULLDUMMY"],
20+
21+
["The following is a tweaked form of 23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63"],
22+
["It is an OP_CHECKMULTISIG with the dummy value set to something other than an empty string"],
23+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
24+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004a01ff47304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH"],
25+
26+
["As above, but using a OP_1"],
27+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
28+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba26000000000495147304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH"],
29+
30+
["As above, but using a OP_1NEGATE"],
31+
[[["60a20bd93aa49ab4b28d514ec10b06e1829ce6818ec06cd3aabd013ebcdc4bb1", 0, "1 0x41 0x04cc71eb30d653c0c3163990c47b976f3fb3f37cccdcbedb169a1dfef58bbfbfaff7d8a473e7e2e6d317b87bafe8bde97e3cf8f065dec022b51d11fcdd0d348ac4 0x41 0x0461cbdcc5409fb4b4d42b51d33381354d80e550078cb532a34bfa2fcfdeb7d76519aecc62770f5b0e4ef8551946d8a540911abe3e7854a26f39f58b25c15342af 2 OP_CHECKMULTISIG"]],
32+
"0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba26000000000494f47304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000", "P2SH"],
1933

2034
["The following is c99c49da4c38af669dea436d3e73780dfdb6c1ecf9958baa52960e8baee30e73"],
2135
["It is of interest because it contains a 0-sequence as well as a signature of SIGHASH type 0 (which is not a real type)"],

‎src/test/transaction_tests.cpp‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -39,6 +39,7 @@ unsigned int ParseFlags(string strFlags){
3939
mapFlagNames["P2SH"] = SCRIPT_VERIFY_P2SH;
4040
mapFlagNames["STRICTENC"] = SCRIPT_VERIFY_STRICTENC;
4141
mapFlagNames["EVEN_S"] = SCRIPT_VERIFY_EVEN_S;
42+
mapFlagNames["NULLDUMMY"] = SCRIPT_VERIFY_NULLDUMMY;
4243
}
4344

4445
BOOST_FOREACH(string word, words)

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