prologic-saltyim/lookup.go

package saltyim

import (
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"strings"

	"github.com/keys-pub/keys"
	log "github.com/sirupsen/logrus"
)

var (
	_ json.Marshaler = (*Addr)(nil)
)

func fetchConfig(addr string) (Config, Capabilities, error) {
	// Attempt using hash
	res, err := Request(http.MethodGet, addr, nil, nil)
	if err != nil {
		return Config{}, Capabilities{}, err
	}

	var config Config
	if err := json.NewDecoder(res.Body).Decode(&config); err != nil {
		return Config{}, Capabilities{}, err
	}

	cap := Capabilities{
		AcceptEncoding: res.Header.Get("Accept-Encoding"),
	}

	return config, cap, err
}

// Config represents a Salty Config for a User which at a minimum is required
// to have an Endpoint and Key (Public Key)
type Config struct {
	Endpoint string `json:"endpoint"`
	Key      string `json:"key"`
}

type Capabilities struct {
	AcceptEncoding string
}

// Addr represents a Salty IM User's Address
type Addr struct {
	User   string
	Domain string

	key              *keys.EdX25519PublicKey
	endpoint         *url.URL
	discoveredDomain string
	capabilities     Capabilities
}

// IsZero returns true if the address is empty
func (a *Addr) IsZero() bool {
	return a.User == "" && a.Domain == ""
}

func (a *Addr) MarshalJSON() ([]byte, error) {
	return json.Marshal(struct {
		Addr     string
		User     string
		Domain   string
		Key      string
		Endpoint string
	}{
		User:     a.User,
		Domain:   a.Domain,
		Addr:     a.String(),
		Key:      a.key.ID().String(),
		Endpoint: a.Endpoint().String(),
	})
}

func (a *Addr) String() string {
	return fmt.Sprintf("%s@%s", a.User, a.Domain)
}

// Hash returns the Hex(SHA256Sum()) of the Address
func (a *Addr) Hash() string {
	return fmt.Sprintf("%x", sha256.Sum256([]byte(a.String())))
}

// Formatted returns a formatted user used in the Salty Message Format
// <timestamp\t(<user>) <message>\n
func (a *Addr) Formatted() string {
	return fmt.Sprintf("(%s)", a)
}

// Key returns the Publib Kcy of this User (Salty Addr) as discovered
func (a *Addr) Key() *keys.EdX25519PublicKey {
	return a.key
}

// Endpoint returns the discovered Endpoint
func (a *Addr) Endpoint() *url.URL {
	return a.endpoint
}

// Cap returns the discovered Capabilities
func (a *Addr) Cap() Capabilities {
	return a.capabilities
}

// DiscoveredDomain returns the discovered domain (if any) of fallbacks to the Domain
func (a *Addr) DiscoveredDomain() string {
	if a.discoveredDomain != "" {
		return a.discoveredDomain
	}
	return a.Domain
}

// URI returns the Well-Known URI for this Addr
func (a *Addr) URI() string {
	return fmt.Sprintf("https://%s/.well-known/salty/%s.json", a.DiscoveredDomain(), a.User)
}

// HashURI returns the Well-Known HashURI for this Addr
func (a *Addr) HashURI() string {
	return fmt.Sprintf("https://%s/.well-known/salty/%s.json", a.DiscoveredDomain(), a.Hash())
}

func (a *Addr) Refresh() error {
	log.Debugf("Looking up SRV record for _salty._tcp.%s", a.Domain)
	if target, err := resolver.LookupSRV("salty", "tcp", a.Domain); err == nil {
		a.discoveredDomain = strings.TrimSuffix(target, ".")
		log.Debugf("Discovered salty services %s", a.discoveredDomain)
	} else if err != nil {
		log.Debugf("error looking up SRV record for _salty._tcp.%s : %s", a.Domain, err)
	}

	config, cap, err := fetchConfig(a.HashURI())
	if err != nil {
		// Fallback to plain user nick
		config, cap, err = fetchConfig(a.URI())
	}
	if err != nil {
		return fmt.Errorf("error looking up user %s: %w", a, err)
	}
	key, err := keys.NewEdX25519PublicKeyFromID(keys.ID(config.Key))
	if err != nil {
		return fmt.Errorf("error parsing public key %s: %w", config.Key, err)
	}
	a.key = key

	u, err := url.Parse(config.Endpoint)
	if err != nil {
		return fmt.Errorf("error parsing endpoint %s: %w", config.Endpoint, err)
	}
	a.endpoint = u
	a.capabilities = cap

	return nil
}

// ParseAddr parsers a Salty Address for a user into it's user and domain
// parts and returns an Addr object with the User and Domain and a method
// for returning the expected User's Well-Known URI
func ParseAddr(addr string) (*Addr, error) {
	parts := strings.Split(addr, "@")
	if len(parts) != 2 {
		return nil, fmt.Errorf("expected nick@domain found %q", addr)
	}

	return &Addr{User: parts[0], Domain: parts[1]}, nil
}

// LookupAddr looks up a Salty Address for a User by parsing the user's domain and
// making a request to the user's Well-Known URI expected to be located at
// https://domain/.well-known/salty/<user>.json
func LookupAddr(addr string) (*Addr, error) {
	a, err := ParseAddr(addr)
	if err != nil {
		return nil, err
	}
	if err := a.Refresh(); err != nil {
		return nil, err
	}
	return a, nil
}