Function decryptAndCheckPubkeyPayload

src/shared.py:228–332

Version 4 pubkeys are encrypted. This function is run when we already have the address to which we want to try to send a message. The 'data' may come either off of the wire or we might have had it already in our inventory when we tried to send a msg to this particular address.

(data, address)

def decryptAndCheckPubkeyPayload(data, address):
    """
    Version 4 pubkeys are encrypted. This function is run when we already have the 
    address to which we want to try to send a message. The 'data' may come either
    off of the wire or we might have had it already in our inventory when we tried
    to send a msg to this particular address. 
    """
    try:
        status, addressVersion, streamNumber, ripe = decodeAddress(address)
        
        readPosition = 20  # bypass the nonce, time, and object type
        embeddedAddressVersion, varintLength = decodeVarint(data[readPosition:readPosition + 10])
        readPosition += varintLength
        embeddedStreamNumber, varintLength = decodeVarint(data[readPosition:readPosition + 10])
        readPosition += varintLength
        storedData = data[20:readPosition] # We'll store the address version and stream number (and some more) in the pubkeys table.
        
        if addressVersion != embeddedAddressVersion:
            logger.info('Pubkey decryption was UNsuccessful due to address version mismatch.')
            return 'failed'
        if streamNumber != embeddedStreamNumber:
            logger.info('Pubkey decryption was UNsuccessful due to stream number mismatch.')
            return 'failed'
        
        tag = data[readPosition:readPosition + 32]
        readPosition += 32
        signedData = data[8:readPosition] # the time through the tag. More data is appended onto signedData below after the decryption. 
        encryptedData = data[readPosition:]
    
        # Let us try to decrypt the pubkey
        toAddress, cryptorObject = state.neededPubkeys[tag]
        if toAddress != address:
            logger.critical('decryptAndCheckPubkeyPayload failed due to toAddress mismatch. This is very peculiar. toAddress: %s, address %s' % (toAddress, address))
            # the only way I can think that this could happen is if someone encodes their address data two different ways.
            # That sort of address-malleability should have been caught by the UI or API and an error given to the user. 
            return 'failed'
        try:
            decryptedData = cryptorObject.decrypt(encryptedData)
        except:
            # Someone must have encrypted some data with a different key
            # but tagged it with a tag for which we are watching.
            logger.info('Pubkey decryption was unsuccessful.')
            return 'failed'
        
        readPosition = 0
        bitfieldBehaviors = decryptedData[readPosition:readPosition + 4]
        readPosition += 4
        publicSigningKey = '\x04' + decryptedData[readPosition:readPosition + 64]
        readPosition += 64
        publicEncryptionKey = '\x04' + decryptedData[readPosition:readPosition + 64]
        readPosition += 64
        specifiedNonceTrialsPerByte, specifiedNonceTrialsPerByteLength = decodeVarint(
            decryptedData[readPosition:readPosition + 10])
        readPosition += specifiedNonceTrialsPerByteLength
        specifiedPayloadLengthExtraBytes, specifiedPayloadLengthExtraBytesLength = decodeVarint(
            decryptedData[readPosition:readPosition + 10])
        readPosition += specifiedPayloadLengthExtraBytesLength
        storedData += decryptedData[:readPosition]