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349 lines
11 KiB
349 lines
11 KiB
// Package profile implements Provider Profiles (spec §10-§13): their
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// Deterministic CBOR encoding, profile_hash, validation and the locally
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// pinned registry that forms the client's root of trust.
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package profile
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import (
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"bytes"
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"crypto/sha256"
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"encoding/hex"
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"fmt"
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"math"
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"time"
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"github.com/drand/drand/v2/common/chain"
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"github.com/drand/drand/v2/crypto"
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datekeys "g.activething.com/go/DateKeys"
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"g.activething.com/go/DateKeys/codec"
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)
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// Schema constants of the Provider Profile CBOR map (spec §11).
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const (
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TypeTag = "datekeys-provider-profile"
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SchemaVersion = 1
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)
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// ProviderDrand is the only provider implemented by this module (spec §12).
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const ProviderDrand = "drand"
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// MaxUnixTime is 9999-12-31T23:59:59Z. Round times beyond it are rejected so
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// that every effective time stays representable in RFC 3339 and every round
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// computation stays within int64.
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const MaxUnixTime int64 = 253402300799
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// Field limits enforced by Validate. They are implementation limits; spec §74
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// leaves the definitive field limits open.
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const (
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maxIDLen = 128
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maxNameLen = 64
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maxPublicKeyLen = 1024
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maxPeriod = 24 * time.Hour
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)
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// Profile is an immutable Provider Profile (spec §10). Treat values as
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// read-only; registries hand out copies.
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type Profile struct {
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ID string // key 2, profile_id, for example "datekeys:quicknet:v1"
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Provider string // key 3, for example "drand"
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Network string // key 4, provider network identifier, for example "quicknet"
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ChainHash [32]byte // key 5
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PublicKey []byte // key 6, provider group public key
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Period time.Duration // key 7, encoded as whole seconds
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GenesisTime int64 // key 8, Unix seconds
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Scheme string // key 9, for example "bls-unchained-g1-rfc9380"
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GenesisSeed [32]byte // key 10
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}
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// wire is the CBOR map of spec §11, keys 2 to 10; keys 0 and 1 are the
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// constants TypeTag and SchemaVersion. Every key is required.
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type wire struct {
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ID string // key 2
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Provider string // key 3
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Network string // key 4
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ChainHash []byte // key 5
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PublicKey []byte // key 6
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Period uint64 // key 7, 1..2^53-1
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GenesisTime uint64 // key 8, 0..2^53-1
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Scheme string // key 9
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GenesisSeed []byte // key 10
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}
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// wireKeys is the number of keys of the map, all required.
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const wireKeys = 11
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// unbounded bounds a field only by the input: its rule carries its own error
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// code (spec §57) and Validate checks it after decoding.
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const unbounded = math.MaxInt
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func (w *wire) encode(e *codec.Encoder) {
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e.Map(wireKeys)
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e.Uint(0)
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e.Text(TypeTag)
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e.Uint(1)
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e.Uint(SchemaVersion)
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e.Uint(2)
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e.Text(w.ID)
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e.Uint(3)
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e.Text(w.Provider)
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e.Uint(4)
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e.Text(w.Network)
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e.Uint(5)
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e.Bstr(w.ChainHash)
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e.Uint(6)
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e.Bstr(w.PublicKey)
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e.Uint(7)
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e.Uint(w.Period)
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e.Uint(8)
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e.Uint(w.GenesisTime)
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e.Uint(9)
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e.Text(w.Scheme)
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e.Uint(10)
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e.Bstr(w.GenesisSeed)
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}
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// decode reads the map with every CDDL rule whose violation is
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// ErrNonCanonicalCBOR; the names and the public key are left to Validate.
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func (w *wire) decode(d *codec.Decoder) error {
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pairs, err := d.Map(wireKeys)
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if err != nil {
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return err
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}
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if pairs != wireKeys {
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return fmt.Errorf("%d keys, want all %d: %w", pairs, wireKeys, datekeys.ErrNonCanonicalCBOR)
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}
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for want := range uint64(wireKeys) {
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k, err := d.Key()
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if err != nil {
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return err
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}
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if k != want {
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return fmt.Errorf("key %d where key %d was expected: %w", k, want, datekeys.ErrNonCanonicalCBOR)
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}
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switch k {
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case 0:
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_, err = d.Text(len(TypeTag))
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case 1:
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_, err = d.Uint(SchemaVersion)
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case 2:
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w.ID, err = d.Text(unbounded)
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case 3:
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w.Provider, err = d.Text(unbounded)
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case 4:
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w.Network, err = d.Text(unbounded)
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case 5:
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w.ChainHash, err = d.Bstr(32, 32)
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case 6:
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w.PublicKey, err = d.Bstr(0, unbounded)
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case 7:
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// Spec §11: period in 1..2^53-1.
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if w.Period, err = d.Uint(codec.MaxSafeUint); err == nil && w.Period == 0 {
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err = fmt.Errorf("period 0: %w", datekeys.ErrNonCanonicalCBOR)
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}
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case 8:
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// Spec §11: genesis_time in 0..2^53-1, unsigned.
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w.GenesisTime, err = d.Uint(codec.MaxSafeUint)
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case 9:
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w.Scheme, err = d.Text(unbounded)
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case 10:
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w.GenesisSeed, err = d.Bstr(32, 32)
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}
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if err != nil {
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return fmt.Errorf("key %d: %w", k, err)
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}
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}
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return d.EndMap()
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}
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// Clone returns a deep copy of p.
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func (p *Profile) Clone() *Profile {
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c := *p
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c.PublicKey = bytes.Clone(p.PublicKey)
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return &c
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}
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// CanonicalCBOR returns the exact Deterministic CBOR bytes of spec §11.
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func (p *Profile) CanonicalCBOR() ([]byte, error) {
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if p.Period <= 0 || p.Period%time.Second != 0 {
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return nil, fmt.Errorf("profile: period %s is not a positive whole number of seconds: %w", p.Period, datekeys.ErrNonCanonicalCBOR)
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}
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// Spec §11: genesis_time in 0..2^53-1. The period needs no such check:
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// a time.Duration holds at most about 9.2e9 seconds.
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if p.GenesisTime < 0 || p.GenesisTime > codec.MaxSafeUint {
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return nil, fmt.Errorf("profile: genesis time %d outside 0..%d: %w", p.GenesisTime, int64(codec.MaxSafeUint), datekeys.ErrNonCanonicalCBOR)
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}
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w := wire{
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ID: p.ID,
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Provider: p.Provider,
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Network: p.Network,
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ChainHash: p.ChainHash[:],
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PublicKey: p.PublicKey,
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Period: uint64(p.Period / time.Second),
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GenesisTime: uint64(p.GenesisTime),
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Scheme: p.Scheme,
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GenesisSeed: p.GenesisSeed[:],
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}
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var e codec.Encoder
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w.encode(&e)
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return e.Out()
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}
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// Hash returns profile_hash = SHA-256(exact_deterministic_cbor_bytes) (spec §11).
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//
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// A profile_hash declared by a remote party has no security value; security
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// comes from the profile pinned locally (spec §11, §13).
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func (p *Profile) Hash() ([32]byte, error) {
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b, err := p.CanonicalCBOR()
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if err != nil {
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return [32]byte{}, err
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}
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return sha256.Sum256(b), nil
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}
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// Decode parses the Deterministic CBOR encoding of a Provider Profile and
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// validates it. It does not make the profile trusted: only a Registry built by
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// the caller does (spec §13).
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func Decode(b []byte) (*Profile, error) {
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if err := codec.CheckSchema(b, TypeTag, SchemaVersion); err != nil {
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return nil, fmt.Errorf("profile: %w", err)
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}
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var w wire
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if err := codec.Unmarshal(b, w.decode, w.encode); err != nil {
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return nil, fmt.Errorf("profile: %w", err)
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}
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if w.Period > uint64(maxPeriod/time.Second) {
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return nil, fmt.Errorf("profile: period %d s out of range: %w", w.Period, datekeys.ErrNonCanonicalCBOR)
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}
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p := &Profile{
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ID: w.ID,
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Provider: w.Provider,
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Network: w.Network,
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PublicKey: w.PublicKey,
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Period: time.Duration(w.Period) * time.Second,
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GenesisTime: int64(w.GenesisTime),
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Scheme: w.Scheme,
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}
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copy(p.ChainHash[:], w.ChainHash)
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copy(p.GenesisSeed[:], w.GenesisSeed)
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if err := p.Validate(); err != nil {
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return nil, err
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}
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return p, nil
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}
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// Validate checks the syntax of every field and, for drand profiles, that the
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// scheme is supported, that the public key is a valid group element and that
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// the chain hash is the drand chain-info hash of the other parameters. The
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// last check is the self-verification kept from the prototype: a profile whose
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// parameters do not produce its own chain hash is rejected.
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func (p *Profile) Validate() error {
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if !ValidID(p.ID) {
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return fmt.Errorf("profile: invalid profile_id %q: %w", p.ID, datekeys.ErrUnknownProfile)
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}
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if !validName(p.Provider) || !validName(p.Network) || !validName(p.Scheme) {
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return fmt.Errorf("profile %s: invalid provider, network or scheme name: %w", p.ID, datekeys.ErrUnknownProfile)
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}
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if len(p.PublicKey) == 0 || len(p.PublicKey) > maxPublicKeyLen {
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return fmt.Errorf("profile %s: invalid public key length %d: %w", p.ID, len(p.PublicKey), datekeys.ErrUnknownProfile)
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}
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if p.Period <= 0 || p.Period > maxPeriod || p.Period%time.Second != 0 {
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return fmt.Errorf("profile %s: invalid period %s: %w", p.ID, p.Period, datekeys.ErrUnknownProfile)
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}
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if p.GenesisTime <= 0 || p.GenesisTime >= MaxUnixTime {
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return fmt.Errorf("profile %s: invalid genesis time %d: %w", p.ID, p.GenesisTime, datekeys.ErrUnknownProfile)
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}
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if p.Provider != ProviderDrand {
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return fmt.Errorf("profile %s: unsupported provider %q: %w", p.ID, p.Provider, datekeys.ErrUnknownProfile)
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}
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return p.validateDrand()
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}
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func (p *Profile) validateDrand() error {
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scheme, err := p.DrandScheme()
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if err != nil {
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return err
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}
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switch scheme.Name {
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case crypto.SigsOnG1ID, crypto.UnchainedSchemeID, crypto.ShortSigSchemeID:
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default:
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return fmt.Errorf("profile %s: scheme %q is not supported by tlock: %w", p.ID, scheme.Name, datekeys.ErrUnknownProfile)
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}
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key := scheme.KeyGroup.Point()
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if err := key.UnmarshalBinary(p.PublicKey); err != nil {
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return fmt.Errorf("profile %s: public key is not a %s group element: %w", p.ID, scheme.Name, datekeys.ErrUnknownProfile)
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}
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if key.Equal(key.Null()) {
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return fmt.Errorf("profile %s: public key is the identity element: %w", p.ID, datekeys.ErrUnknownProfile)
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}
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info := chain.Info{
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PublicKey: key,
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ID: p.Network,
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Period: p.Period,
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Scheme: p.Scheme,
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GenesisTime: p.GenesisTime,
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GenesisSeed: p.GenesisSeed[:],
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}
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if !bytes.Equal(info.Hash(), p.ChainHash[:]) {
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return fmt.Errorf("profile %s: parameters hash to chain %s, not the pinned %s: %w",
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p.ID, info.HashString(), hex.EncodeToString(p.ChainHash[:]), datekeys.ErrProfileMismatch)
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}
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return nil
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}
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// DrandScheme returns a fresh drand scheme object for p. Fresh objects avoid
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// sharing mutable kyber state between callers.
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func (p *Profile) DrandScheme() (*crypto.Scheme, error) {
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if p.Provider != ProviderDrand {
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return nil, fmt.Errorf("profile %s: provider %q is not drand: %w", p.ID, p.Provider, datekeys.ErrUnknownProfile)
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}
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scheme, err := crypto.SchemeFromName(p.Scheme)
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if err != nil {
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return nil, fmt.Errorf("profile %s: %v: %w", p.ID, err, datekeys.ErrUnknownProfile)
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}
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return scheme, nil
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}
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// ChainHashHex returns the lowercase hexadecimal chain hash, the form used in
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// tlock stanzas and drand relay URLs.
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func (p *Profile) ChainHashHex() string { return hex.EncodeToString(p.ChainHash[:]) }
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// MaxRound is the last round whose round time is not after MaxUnixTime.
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func (p *Profile) MaxRound() uint64 {
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period := int64(p.Period / time.Second)
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if period <= 0 || p.GenesisTime >= MaxUnixTime {
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return 0
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}
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return uint64((MaxUnixTime-p.GenesisTime)/period) + 1
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}
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// ValidID reports whether s is a syntactically valid profile_id: 1 to 128
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// characters from [a-z0-9:._-], starting with a letter or digit. The restricted
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// alphabet keeps the dk1_ JSON form free of escapes (spec §18, §19).
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func ValidID(s string) bool {
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if len(s) == 0 || len(s) > maxIDLen || !alnum(s[0]) {
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return false
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}
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for i := 0; i < len(s); i++ {
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c := s[i]
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if !alnum(c) && c != ':' && c != '.' && c != '_' && c != '-' {
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return false
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}
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}
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return true
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}
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func validName(s string) bool {
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if len(s) == 0 || len(s) > maxNameLen || !alnum(s[0]) {
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return false
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}
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for i := 0; i < len(s); i++ {
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c := s[i]
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if !alnum(c) && c != '.' && c != '_' && c != '-' {
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return false
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}
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}
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return true
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}
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func alnum(c byte) bool { return (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') }
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