Multi-Signature Transaction - Verify First Signature is Valid?

Question

Using Gavin Anderson's TwoOfThree.sh Gist located here: https://gist.github.com/gavinandresen/3966071

Is it possible to verify the first "partial" signrawtransaction is valid from the known public key prior to performing the second signrawtransaction? My goal is to be as close to sure as possible that the transaction will be accepted by the network prior to sending. In this scenario I would already know that the bitcoins are spendable by the multisig address in question and that the appropriate transaction fee was included in the transaction.

The two steps are below. Help appreciated!

# ... Now I can partially sign it using one private key:
./bitcoind signrawtransaction '0100000001aca7f3b45654c230e0886a57fb988c3044ef5e8f7f39726d305c61d5e818903c0000000000ffffffff0140420f00000000001976a914ae56b4db13554d321c402db3961187aed1bbed5b88ac00000000' '[{"txid":"3c9018e8d5615c306d72397f8f5eef44308c98fb576a88e030c25456b4f3a7ac","vout":0,"scriptPubKey":"a914f815b036d9bbbce5e9f2a00abd1bf3dc91e9551087","redeemScript":"52410491bba2510912a5bd37da1fb5b1673010e43d2c6d812c514e91bfa9f2eb129e1c183329db55bd868e209aac2fbc02cb33d98fe74bf23f0c235d6126b1d8334f864104865c40293a680cb9c020e7b1e106d8c1916d3cef99aa431a56d253e69256dac09ef122b1a986818a7cb624532f062c1d1f8722084861c5c3291ccffef4ec687441048d2455d2403e08708fc1f556002f1b6cd83f992d085097f9974ab08a28838f07896fbab08f39495e15fa6fad6edbfb1e754e35fa1c7844c41f322a1863d4621353ae"}]' '["5JaTXbAUmfPYZFRwrYaALK48fN6sFJp4rHqq2QSXs8ucfpE4yQU"]'

{
        "hex" : "0100000001aca7f3b45654c230e0886a57fb988c3044ef5e8f7f39726d305c61d5e818903c00000000fd15010048304502200187af928e9d155c4b1ac9c1c9118153239aba76774f775d7c1f9c3e106ff33c0221008822b0f658edec22274d0b6ae9de10ebf2da06b1bbdaaba4e50eb078f39e3d78014cc952410491bba2510912a5bd37da1fb5b1673010e43d2c6d812c514e91bfa9f2eb129e1c183329db55bd868e209aac2fbc02cb33d98fe74bf23f0c235d6126b1d8334f864104865c40293a680cb9c020e7b1e106d8c1916d3cef99aa431a56d253e69256dac09ef122b1a986818a7cb624532f062c1d1f8722084861c5c3291ccffef4ec687441048d2455d2403e08708fc1f556002f1b6cd83f992d085097f9974ab08a28838f07896fbab08f39495e15fa6fad6edbfb1e754e35fa1c7844c41f322a1863d4621353aeffffffff0140420f00000000001976a914ae56b4db13554d321c402db3961187aed1bbed5b88ac00000000",
        "complete" : false
}

# ... and then take the "hex" from that and complete the 2-of-3 signatures using one of
# the other public keys (note the "hex" result getting longer):
./bitcoind signrawtransaction '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' '[{"txid":"3c9018e8d5615c306d72397f8f5eef44308c98fb576a88e030c25456b4f3a7ac","vout":0,"scriptPubKey":"a914f815b036d9bbbce5e9f2a00abd1bf3dc91e9551087","redeemScript":"52410491bba2510912a5bd37da1fb5b1673010e43d2c6d812c514e91bfa9f2eb129e1c183329db55bd868e209aac2fbc02cb33d98fe74bf23f0c235d6126b1d8334f864104865c40293a680cb9c020e7b1e106d8c1916d3cef99aa431a56d253e69256dac09ef122b1a986818a7cb624532f062c1d1f8722084861c5c3291ccffef4ec687441048d2455d2403e08708fc1f556002f1b6cd83f992d085097f9974ab08a28838f07896fbab08f39495e15fa6fad6edbfb1e754e35fa1c7844c41f322a1863d4621353ae"}]' '["5JFjmGo5Fww9p8gvx48qBYDJNAzR9pmH5S389axMtDyPT8ddqmw"]'

{
        "hex" : "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",
        "complete" : true
}

Answer 1

As far as I know there's no built-in functionality in Bitcoin to check signatures in each input independently. Either all signatures are correct (so it shows {complete: true}) or there's at least one unsigned/invalid/input values don't add up to output values (so it shows {complete: false}).

The procedure will go as follows:

1. Retrieve the referenced output {txid, vout} from the UTXO set or retrieving txid and only getting the appropriate output.
2. Check the value is what you expect (if you care about the value at all) and get the scriptPubKey.
3. Run the current-input scriptSig and then, with the resulting stack, the previous-output scriptPubKey.

If the resulting stack top is not zero (i.e, is TRUE) then the input is correctly signed.