routing: record validation into record/

This commit moves the record validation/verification
from dht/ into the new record/ packaage. Validator object
-- which is merely a map of ValidatorFuncs -- with a
VerifyRecord

cc @whyrusleeping

routing/record/validation.go

@@ -0,0 +1,75 @@
+package record
+
+import (
+	"bytes"
+	"errors"
+	"strings"
+
+	ci "github.com/jbenet/go-ipfs/p2p/crypto"
+	pb "github.com/jbenet/go-ipfs/routing/dht/pb"
+	u "github.com/jbenet/go-ipfs/util"
+)
+
+// ValidatorFunc is a function that is called to validate a given
+// type of DHTRecord.
+type ValidatorFunc func(u.Key, []byte) error
+
+// ErrBadRecord is returned any time a dht record is found to be
+// incorrectly formatted or signed.
+var ErrBadRecord = errors.New("bad dht record")
+
+// ErrInvalidRecordType is returned if a DHTRecord keys prefix
+// is not found in the Validator map of the DHT.
+var ErrInvalidRecordType = errors.New("invalid record keytype")
+
+// Validator is an object that helps ensure routing records are valid.
+// It is a collection of validator functions, each of which implements
+// its own notion of validity.
+type Validator map[string]ValidatorFunc
+
+// VerifyRecord checks a record and ensures it is still valid.
+// It runs needed validators
+func (v Validator) VerifyRecord(r *pb.Record, pk ci.PubKey) error {
+	// First, validate the signature
+	blob := RecordBlobForSig(r)
+	ok, err := pk.Verify(blob, r.GetSignature())
+	if err != nil {
+		log.Error("Signature verify failed.")
+		return err
+	}
+	if !ok {
+		log.Error("dht found a forged record! (ignored)")
+		return ErrBadRecord
+	}
+
+	// Now, check validity func
+	parts := strings.Split(r.GetKey(), "/")
+	if len(parts) < 3 {
+		log.Infof("Record key does not have validator: %s", u.Key(r.GetKey()))
+		return nil
+	}
+
+	fnc, ok := v[parts[1]]
+	if !ok {
+		log.Errorf("Unrecognized key prefix: %s", parts[1])
+		return ErrInvalidRecordType
+	}
+
+	return fnc(u.Key(r.GetKey()), r.GetValue())
+}
+
+// ValidatePublicKeyRecord implements ValidatorFunc and
+// verifies that the passed in record value is the PublicKey
+// that matches the passed in key.
+func ValidatePublicKeyRecord(k u.Key, val []byte) error {
+	keyparts := bytes.Split([]byte(k), []byte("/"))
+	if len(keyparts) < 3 {
+		return errors.New("invalid key")
+	}
+
+	pkh := u.Hash(val)
+	if !bytes.Equal(keyparts[2], pkh) {
+		return errors.New("public key does not match storage key")
+	}
+	return nil
+}