Problems with transactions with large amouts

[tmpolaczyk]

When the transaction created by the wallet has some outputs with values larger than MAX_SAFE_INTEGER, sheikah may round them to the nearest valid float and then send an invalid transaction.

For example, creating a transaciton that tries to send 9 million wits:

{"jsonrpc":"2.0","method":"inventory","params":{"transaction":{"ValueTransfer":{"body":{"inputs":[{"output_pointer":"988ed9952b6d6195f5afdaf4a3d934ee81c45c8eed96f218c49a8637b1b55023:0"},{"output_pointer":"988ed9952b6d6195f5afdaf4a3d934ee81c45c8eed96f218c49a8637b1b55023:1"},{"output_pointer":"6977e18fa4988ae7fc17c4a8462d3cb262153ad23954bd8e0abaa62239fe23fe:0"}],"outputs":[{"pkh":"twit1vfuklxq4p5d7t744evcrj04r68q7j2f8yj0vqx","time_lock":0,"value":9000000000000000},{"pkh":"twit1lq6vc30s9w6lad2gsmqd028z8zdvjs2r4hmdj5","time_lock":0,"value":25496909012345690}]},"signatures":[{"public_key":{"bytes":[223,106,84,98,186,170,171,0,160,129,45,64,26,180,3,239,237,240,218,147,49,140,142,233,52,150,246,61,236,173,139,204],"compressed":3},"signature":{"Secp256k1":{"der":[48,69,2,33,0,205,100,244,242,167,81,242,185,38,28,142,72,232,18,253,42,130,71,241,136,176,181,247,54,136,87,108,211,145,88,49,237,2,32,110,218,235,243,104,253,197,76,219,84,153,217,65,121,37,196,41,218,210,227,155,147,30,172,89,41,252,210,150,65,81,254]}}},{"public_key":{"bytes":[126,11,75,235,151,155,199,96,45,91,211,86,51,229,247,88,255,211,147,94,190,159,117,45,180,192,162,138,116,253,236,225],"compressed":3},"signature":{"Secp256k1":{"der":[48,68,2,32,105,215,154,161,6,160,43,110,16,53,250,204,9,27,247,183,223,81,33,114,95,112,187,126,15,236,58,192,90,182,127,148,2,32,66,181,236,190,29,170,243,236,228,185,13,139,165,253,162,224,132,124,193,101,205,52,151,54,17,19,58,208,42,114,126,225]}}},{"public_key":{"bytes":[223,106,84,98,186,170,171,0,160,129,45,64,26,180,3,239,237,240,218,147,49,140,142,233,52,150,246,61,236,173,139,204],"compressed":3},"signature":{"Secp256k1":{"der":[48,69,2,33,0,205,100,244,242,167,81,242,185,38,28,142,72,232,18,253,42,130,71,241,136,176,181,247,54,136,87,108,211,145,88,49,237,2,32,110,218,235,243,104,253,197,76,219,84,153,217,65,121,37,196,41,218,210,227,155,147,30,172,89,41,252,210,150,65,81,254]}}}]}}},"id":71}

Using the node CLI, we can calculate the value of the inputs, to summarize:

inputs: 3000000000000000 + 1498028000000009 + 30000000012345680
outputs: 9000000000000000 + 25496909012345690
fee according to sheikah: 1119000000000 (1 wit / weight unit)

However, if we calculate (inputs - outputs), the actual fee is 1118999999999.

The problem is that the change output should be 25496909012345689 instead of 25496909012345690. This can be seen in the following JSON-RPC logs. The first transaction is the one sent from sheikah and it is invalid with error "Failed to verify the signature of transaction". The second transaction is a copy of the first but with that one output manually changed, and it is sent successfully.

{"jsonrpc":"2.0","method":"inventory","params":{"transaction":{"ValueTransfer":{"body":{"inputs":[{"output_pointer":"988ed9952b6d6195f5afdaf4a3d934ee81c45c8eed96f218c49a8637b1b55023:0"},{"output_pointer":"988ed9952b6d6195f5afdaf4a3d934ee81c45c8eed96f218c49a8637b1b55023:1"},{"output_pointer":"6977e18fa4988ae7fc17c4a8462d3cb262153ad23954bd8e0abaa62239fe23fe:0"}],"outputs":[{"pkh":"twit1vfuklxq4p5d7t744evcrj04r68q7j2f8yj0vqx","time_lock":0,"value":9000000000000000},{"pkh":"twit1lq6vc30s9w6lad2gsmqd028z8zdvjs2r4hmdj5","time_lock":0,"value":25496909012345690}]},"signatures":[{"public_key":{"bytes":[223,106,84,98,186,170,171,0,160,129,45,64,26,180,3,239,237,240,218,147,49,140,142,233,52,150,246,61,236,173,139,204],"compressed":3},"signature":{"Secp256k1":{"der":[48,69,2,33,0,205,100,244,242,167,81,242,185,38,28,142,72,232,18,253,42,130,71,241,136,176,181,247,54,136,87,108,211,145,88,49,237,2,32,110,218,235,243,104,253,197,76,219,84,153,217,65,121,37,196,41,218,210,227,155,147,30,172,89,41,252,210,150,65,81,254]}}},{"public_key":{"bytes":[126,11,75,235,151,155,199,96,45,91,211,86,51,229,247,88,255,211,147,94,190,159,117,45,180,192,162,138,116,253,236,225],"compressed":3},"signature":{"Secp256k1":{"der":[48,68,2,32,105,215,154,161,6,160,43,110,16,53,250,204,9,27,247,183,223,81,33,114,95,112,187,126,15,236,58,192,90,182,127,148,2,32,66,181,236,190,29,170,243,236,228,185,13,139,165,253,162,224,132,124,193,101,205,52,151,54,17,19,58,208,42,114,126,225]}}},{"public_key":{"bytes":[223,106,84,98,186,170,171,0,160,129,45,64,26,180,3,239,237,240,218,147,49,140,142,233,52,150,246,61,236,173,139,204],"compressed":3},"signature":{"Secp256k1":{"der":[48,69,2,33,0,205,100,244,242,167,81,242,185,38,28,142,72,232,18,253,42,130,71,241,136,176,181,247,54,136,87,108,211,145,88,49,237,2,32,110,218,235,243,104,253,197,76,219,84,153,217,65,121,37,196,41,218,210,227,155,147,30,172,89,41,252,210,150,65,81,254]}}}]}}},"id":71}
{"jsonrpc":"2.0","error":{"code":-32603,"message":"Failed to verify the signature of transaction 9bb1aecde93a605912d260394e96bf2c4b0918f9ad9c31c22d9afb3ccacda4b7: Fail in verify process"},"id":71}
{"jsonrpc":"2.0","method":"inventory","params":{"transaction":{"ValueTransfer":{"body":{"inputs":[{"output_pointer":"988ed9952b6d6195f5afdaf4a3d934ee81c45c8eed96f218c49a8637b1b55023:0"},{"output_pointer":"988ed9952b6d6195f5afdaf4a3d934ee81c45c8eed96f218c49a8637b1b55023:1"},{"output_pointer":"6977e18fa4988ae7fc17c4a8462d3cb262153ad23954bd8e0abaa62239fe23fe:0"}],"outputs":[{"pkh":"twit1vfuklxq4p5d7t744evcrj04r68q7j2f8yj0vqx","time_lock":0,"value":9000000000000000},{"pkh":"twit1lq6vc30s9w6lad2gsmqd028z8zdvjs2r4hmdj5","time_lock":0,"value":25496909012345689}]},"signatures":[{"public_key":{"bytes":[223,106,84,98,186,170,171,0,160,129,45,64,26,180,3,239,237,240,218,147,49,140,142,233,52,150,246,61,236,173,139,204],"compressed":3},"signature":{"Secp256k1":{"der":[48,69,2,33,0,205,100,244,242,167,81,242,185,38,28,142,72,232,18,253,42,130,71,241,136,176,181,247,54,136,87,108,211,145,88,49,237,2,32,110,218,235,243,104,253,197,76,219,84,153,217,65,121,37,196,41,218,210,227,155,147,30,172,89,41,252,210,150,65,81,254]}}},{"public_key":{"bytes":[126,11,75,235,151,155,199,96,45,91,211,86,51,229,247,88,255,211,147,94,190,159,117,45,180,192,162,138,116,253,236,225],"compressed":3},"signature":{"Secp256k1":{"der":[48,68,2,32,105,215,154,161,6,160,43,110,16,53,250,204,9,27,247,183,223,81,33,114,95,112,187,126,15,236,58,192,90,182,127,148,2,32,66,181,236,190,29,170,243,236,228,185,13,139,165,253,162,224,132,124,193,101,205,52,151,54,17,19,58,208,42,114,126,225]}}},{"public_key":{"bytes":[223,106,84,98,186,170,171,0,160,129,45,64,26,180,3,239,237,240,218,147,49,140,142,233,52,150,246,61,236,173,139,204],"compressed":3},"signature":{"Secp256k1":{"der":[48,69,2,33,0,205,100,244,242,167,81,242,185,38,28,142,72,232,18,253,42,130,71,241,136,176,181,247,54,136,87,108,211,145,88,49,237,2,32,110,218,235,243,104,253,197,76,219,84,153,217,65,121,37,196,41,218,210,227,155,147,30,172,89,41,252,210,150,65,81,254]}}}]}}},"id":71}
{"jsonrpc":"2.0","result":true,"id":71}

After manually fixing the transaction, sheikah indexes it and shows it, but we can see how the value of the second output and the fee are wrong:

[Tommytrg]

Until witnet/witnet-rust#1760 is done, we have implemented #1541 to solve this problem preventively

[tmpolaczyk]

Still happens as of sheikah commit b3142ff, and wallet commit witnet/witnet-rust@ed1b152

Steps to reproduce:

1. create local testnet with custom genesis block, allocate 15000000000000009 nanowits for the first wallet address
2. try to create transaction with value 1 nanowit and fee 1 nanowit/weight unit
3. check wallet logs for "Failed to verify the signature of transaction"