enr

Documentation

Overview

Package enr implements Abassian Node Records as defined in EIP-778. A node record holds arbitrary information about a node on the peer-to-peer network. Node information is stored in key/value pairs. To store and retrieve key/values in a record, use the Entry interface.

Signature Handling

Records must be signed before transmitting them to another node.

Decoding a record doesn't check its signature. Code working with records from an untrusted source must always verify two things: that the record uses an identity scheme deemed secure, and that the signature is valid according to the declared scheme.

When creating a record, set the entries you want and use a signing function provided by the identity scheme to add the signature. Modifying a record invalidates the signature.

Package enr supports the "secp256k1-keccak" identity scheme.

Index

• Constants
• Variables
• func IsNotFound(err error) bool
• type Entry
  • func WithEntry(k string, v interface{}) Entry
• type ID
  • func (v ID) ENRKey() string
• type IP
  • func (v *IP) DecodeRLP(s *rlp.Stream) error
  • func (v IP) ENRKey() string
  • func (v IP) EncodeRLP(w io.Writer) error
• type IdentityScheme
• type KeyError
  • func (err *KeyError) Error() string
• type Record
  • func (r *Record) AppendElements(list []interface{}) []interface{}
  • func (r *Record) DecodeRLP(s *rlp.Stream) error
  • func (r Record) EncodeRLP(w io.Writer) error
  • func (r *Record) IdentityScheme() string
  • func (r *Record) Load(e Entry) error
  • func (r *Record) Seq() uint64
  • func (r *Record) Set(e Entry)
  • func (r *Record) SetSeq(s uint64)
  • func (r *Record) SetSig(s IdentityScheme, sig []byte) error
  • func (r *Record) VerifySignature(s IdentityScheme) error
• type SchemeMap
  • func (m SchemeMap) NodeAddr(r *Record) []byte
  • func (m SchemeMap) Verify(r *Record, sig []byte) error
• type TCP
  • func (v TCP) ENRKey() string
• type UDP
  • func (v UDP) ENRKey() string

Constants

const IDv4 = ID("v4") // the default identity scheme

const SizeLimit = 300 // maximum encoded size of a node record in bytes

Variables

var (
	ErrInvalidSig = errors.New("invalid signature on node record")
)

Functions

func IsNotFound

func IsNotFound(err error) bool

IsNotFound reports whether the given error means that a key/value pair is missing from a record.

Types

type Entry

type Entry interface {
	ENRKey() string
}

Entry is implemented by known node record entry types.

To define a new entry that is to be included in a node record, create a Go type that satisfies this interface. The type should also implement rlp.Decoder if additional checks are needed on the value.

func WithEntry

func WithEntry(k string, v interface{}) Entry

WithEntry wraps any value with a key name. It can be used to set and load arbitrary values in a record. The value v must be supported by rlp. To use WithEntry with Load, the value must be a pointer.

type ID

type ID string

ID is the "id" key, which holds the name of the identity scheme.

func (ID) ENRKey

func (v ID) ENRKey() string

type IP

type IP net.IP

IP is the "ip" key, which holds the IP address of the node.

func (*IP) DecodeRLP

func (v *IP) DecodeRLP(s *rlp.Stream) error

DecodeRLP implements rlp.Decoder.

func (IP) ENRKey

func (v IP) ENRKey() string

func (IP) EncodeRLP

func (v IP) EncodeRLP(w io.Writer) error

EncodeRLP implements rlp.Encoder.

type IdentityScheme

type IdentityScheme interface {
	Verify(r *Record, sig []byte) error
	NodeAddr(r *Record) []byte
}

An IdentityScheme is capable of verifying record signatures and deriving node addresses.

type KeyError

type KeyError struct {
	Key string
	Err error
}

KeyError is an error related to a key.

func (*KeyError) Error

func (err *KeyError) Error() string

Error implements error.

type Record

type Record struct {
	// contains filtered or unexported fields
}

Record represents a node record. The zero value is an empty record.

func (*Record) AppendElements

func (r *Record) AppendElements(list []interface{}) []interface{}

AppendElements appends the sequence number and entries to the given slice.

func (*Record) DecodeRLP

func (r *Record) DecodeRLP(s *rlp.Stream) error

DecodeRLP implements rlp.Decoder. Decoding verifies the signature.

func (Record) EncodeRLP

func (r Record) EncodeRLP(w io.Writer) error

EncodeRLP implements rlp.Encoder. Encoding fails if the record is unsigned.

func (*Record) IdentityScheme

func (r *Record) IdentityScheme() string

IdentityScheme returns the name of the identity scheme in the record.

func (*Record) Load

func (r *Record) Load(e Entry) error

Load retrieves the value of a key/value pair. The given Entry must be a pointer and will be set to the value of the entry in the record.

Errors returned by Load are wrapped in KeyError. You can distinguish decoding errors from missing keys using the IsNotFound function.

func (*Record) Seq

func (r *Record) Seq() uint64

Seq returns the sequence number.

func (*Record) Set

func (r *Record) Set(e Entry)

Set adds or updates the given entry in the record. It panics if the value can't be encoded. If the record is signed, Set increments the sequence number and invalidates the sequence number.

func (*Record) SetSeq

func (r *Record) SetSeq(s uint64)

SetSeq updates the record sequence number. This invalidates any signature on the record. Calling SetSeq is usually not required because setting any key in a signed record increments the sequence number.

func (*Record) SetSig

func (r *Record) SetSig(s IdentityScheme, sig []byte) error

SetSig sets the record signature. It returns an error if the encoded record is larger than the size limit or if the signature is invalid according to the passed scheme.

You can also use SetSig to remove the signature explicitly by passing a nil scheme and signature.

SetSig panics when either the scheme or the signature (but not both) are nil.

func (*Record) VerifySignature

func (r *Record) VerifySignature(s IdentityScheme) error

VerifySignature checks whether the record is signed using the given identity scheme.

type SchemeMap

type SchemeMap map[string]IdentityScheme

SchemeMap is a registry of named identity schemes.

func (SchemeMap) NodeAddr

func (m SchemeMap) NodeAddr(r *Record) []byte

func (SchemeMap) Verify

func (m SchemeMap) Verify(r *Record, sig []byte) error

type TCP

type TCP uint16

TCP is the "tcp" key, which holds the TCP port of the node.

func (TCP) ENRKey

func (v TCP) ENRKey() string

type UDP

type UDP uint16

UDP is the "udp" key, which holds the UDP port of the node.

func (UDP) ENRKey

func (v UDP) ENRKey() string