//verify block signature
func (bc *BlockChain) VerifyBlockSignature(block Block) error {
//set signature
hash := block.Head.Hash() //block hash
pubkey, err := cipher.PubKeyFromSig(block.Sig, hash) //recovered pubkey for sig
if err != nil {
return errors.New("Pubkey recovery failed")
}
if bc.Genesis().Head.PrevHash != PubKeyHash(pubkey) {
return errors.New("NewBlock, signature is not for pubkey for genesis")
}
err = cipher.VerifySignedHash(block.Sig, hash)
if err != nil {
return errors.New("Signature verification failed for hash")
}
return nil
}
func (self *BlockStat) try_add_hash_and_sig(
hash cipher.SHA256,
sig cipher.Sig) int {
if self.frozen {
// To get a more accurate number of rejects, one would need to
// do as below, except insertion/updating. However, we do not
// want to incurr a calculation in order to get a more
// accurate debug numbers. So we simply:
self.debug_reject_count += 1
return 3
}
// 2016090* ROBUSTNESS: We need to put a limit on the number of
// (signer_pubkey,hash) pairs that we process and forward. One
// reason is to prevent an attack in which the attacker launches a
// large number of nodes each of which make valid blocks, thus
// causing large traffic that can potentially degrade the network
// performace. Example: when we receive, say 63
// (signer_pubkey,hash) pairs for a given seqno, we stop listening
// for the updates. Say, the breakdown is: hash H1 from 50
// signers, hash H2 from 10, hash H3 from 2 and hash H4 from 1.
// We make a local decision to choose H1.
if self.accept_count >= Cfg_consensus_max_candidate_messages {
self.debug_neglect_count += 1
return 1 // same as skip
}
// 20160913 Remember that we move those BlockStat that are old
// enought (seqno difference is used as a measure of time
// difference) to BlockChain, so that the storage requerement for
// each node is now smaller. Yet we keep the limits to avoid
// excessive forwarding.
// At the end of the function, one of them must be 'true'.
action_update := false
action_skip := false
action_insert := false
var info HashCandidate
if true {
var have bool
info, have = self.hash2info[hash]
if !have {
info = HashCandidate{}
info.Init()
action_insert = true
} else {
if _, saw := info.sig2none[sig]; saw {
action_skip = true
} else {
action_update = true
}
}
}
if action_insert || action_update {
if sig == all_zero_sig || hash == all_zero_hash { // Hack
return 4 // <<<<<<<<
}
// PERFORMANCE: This is an expensive call:
signer_pubkey, err := cipher.PubKeyFromSig(sig, hash)
if err != nil {
return 4 // <<<<<<<<
}
// Now do the check that we could not do prior to
// obtaining 'signer_pubkey':
if _, have := info.pubkey2sig[signer_pubkey]; have {
// WARNING: ROBUSTNESS: The pubkey 'signer_pubkey' has
// already published data with the same hash and same
// seqno. This is not a duplicate data: the duplicates
// have been intercepted earlier bsaged in (hash,sig)
// pair; instead, the pubkey signed the block again and
// published the result. So this can be a bug/mistake or
// an attempt to artificially increase the traffic on our
// network.
self.debug_reject_count += 1
action_update = false
action_skip = true
action_insert = false
fmt.Printf("WARNING: %p, Detected malicious publish from"+
" pubkey=%s for hash=%s sig=%s\n", &info,
signer_pubkey.Hex()[:8], hash.Hex()[:8], sig.Hex()[:8])
}
// These bools could have change, see above:
if action_insert || action_update {
if false {
fmt.Printf("Calling %p->ObserveSigAndPubkey(sig=%s,"+
" signer_pubkey=%s), hash=%s\n", &info,
sig.Hex()[:8], signer_pubkey.Hex()[:8], hash.Hex()[:8])
}
info.ObserveSigAndPubkey(sig, signer_pubkey)
self.accept_count += 1
}
}
if action_insert {
self.hash2info[hash] = info
}
self.debug_count += 1
self.debug_usage += 1
if !(action_update || action_skip || action_insert) {
panic("Inconsistent BlockStat::try_add_hash_and_sig()")
return -1
}
if action_update || action_insert {
return 0
}
if action_skip {
return 1
}
return -1
}