cwtch/model/profile.go

package model

import (
	"crypto/rand"
	"cwtch.im/cwtch/protocol/groups"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"git.openprivacy.ca/cwtch.im/tapir/primitives"
	"golang.org/x/crypto/ed25519"
	"io"
	"path/filepath"
	"sync"
	"time"
)

// Authorization is a type determining client assigned authorization to a peer
type Authorization string

const (
	// AuthUnknown is an initial state for a new unseen peer
	AuthUnknown Authorization = "unknown"
	// AuthApproved means the client has approved the peer, it can send messages to us, perform GetVals, etc
	AuthApproved Authorization = "approved"
	// AuthBlocked means the client has blocked the peer, it's messages and connections should be rejected
	AuthBlocked Authorization = "blocked"
)

// PublicProfile is a local copy of a CwtchIdentity
type PublicProfile struct {
	Name                   string
	Ed25519PublicKey       ed25519.PublicKey
	Authorization          Authorization
	DeprecatedBlocked      bool `json:"Blocked"`
	Onion                  string
	Attributes             map[string]string
	Timeline               Timeline `json:"-"`
	LocalID                string   // used by storage engine
	State                  string   `json:"-"`
	lock                   sync.Mutex
	UnacknowledgedMessages map[string]int
}

// Profile encapsulates all the attributes necessary to be a Cwtch Peer.
type Profile struct {
	PublicProfile
	Contacts          map[string]*PublicProfile
	Ed25519PrivateKey ed25519.PrivateKey
	Groups            map[string]*Group
}

// MaxGroupMessageLength is the maximum length of a message posted to a server group.
// TODO: Should this be per server?
const MaxGroupMessageLength = 1800

func getRandomness(arr *[]byte) {
	if _, err := io.ReadFull(rand.Reader, (*arr)[:]); err != nil {
		if err != nil {
			// If we can't do randomness, just crash something is very very wrong and we are not going
			// to resolve it here....
			panic(err.Error())
		}
	}
}

// GenerateRandomID generates a random 16 byte hex id code
func GenerateRandomID() string {
	randBytes := make([]byte, 16)
	rand.Read(randBytes)
	return filepath.Join(hex.EncodeToString(randBytes))
}

// EncryptMessageToGroup when given a message and a group, encrypts and signs the message under the group and
// profile
func EncryptMessageToGroup(message string, author primitives.Identity, group *Group) ([]byte, []byte, *groups.DecryptedGroupMessage, error) {
	if len(message) > MaxGroupMessageLength {
		return nil, nil, nil, errors.New("group message is too long")
	}
	timestamp := time.Now().Unix()

	// Select the latest message from the timeline as a reference point.
	var prevSig []byte
	if len(group.Timeline.Messages) > 0 {
		prevSig = group.Timeline.Messages[len(group.Timeline.Messages)-1].Signature
	} else {
		prevSig = []byte(group.GroupID)
	}

	lenPadding := MaxGroupMessageLength - len(message)
	padding := make([]byte, lenPadding)
	getRandomness(&padding)
	hexGroupID, err := hex.DecodeString(group.GroupID)
	if err != nil {
		return nil, nil, nil, err
	}

	dm := &groups.DecryptedGroupMessage{
		Onion:              author.Hostname(),
		Text:               message,
		SignedGroupID:      hexGroupID,
		Timestamp:          uint64(timestamp),
		PreviousMessageSig: prevSig,
		Padding:            padding[:],
	}

	ciphertext, err := group.EncryptMessage(dm)
	if err != nil {
		return nil, nil, nil, err
	}
	serialized, _ := json.Marshal(dm)
	signature := author.Sign([]byte(group.GroupID + group.GroupServer + base64.StdEncoding.EncodeToString(serialized)))
	return ciphertext, signature, dm, nil
}

// GetCopy returns a full deep copy of the Profile struct and its members (timeline inclusion control by arg)
func (p *Profile) GetCopy(timeline bool) *Profile {
	p.lock.Lock()
	defer p.lock.Unlock()

	newp := new(Profile)
	bytes, _ := json.Marshal(p)
	json.Unmarshal(bytes, &newp)

	if timeline {
		for groupID := range newp.Groups {
			newp.Groups[groupID].Timeline = *p.Groups[groupID].Timeline.GetCopy()
		}

		for peerID := range newp.Contacts {
			newp.Contacts[peerID].Timeline = *p.Contacts[peerID].Timeline.GetCopy()
		}
	}

	return newp
}