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links.go
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links.go
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package bertylinks
import (
"bytes"
"crypto/aes"
"fmt"
"net/url"
"strings"
"github.com/eknkc/basex"
"github.com/gogo/protobuf/proto"
"github.com/mr-tron/base58"
"golang.org/x/crypto/sha3"
"berty.tech/berty/v2/go/internal/cryptoutil"
"berty.tech/berty/v2/go/pkg/errcode"
"berty.tech/berty/v2/go/pkg/messengertypes"
"berty.tech/berty/v2/go/pkg/protocoltypes"
)
// MarshalLink returns shareable web and internal URLs.
//
// The web URL is meant to:
// - be short,
// - have some parts that are human-readable,
// - to point to a sub-page of the berty.tech website where some JS code will parse the human-readable part.
//
// The internal URL is meant to generate the most tiny QR codes. These QR codes can only be opened by a Berty app.
//
// Marshal will return an error if the provided link does not contain all the mandatory fields;
// it may also filter-out some sensitive data.
func MarshalLink(link *messengertypes.BertyLink) (internal string, web string, err error) {
if link == nil || link.Kind == messengertypes.BertyLink_UnknownKind {
return "", "", errcode.ErrMissingInput
}
if err := link.IsValid(); err != nil {
return "", "", err
}
var (
// web
kind string
machine = &messengertypes.BertyLink{}
human = url.Values{}
// internal
qrOptimized = &messengertypes.BertyLink{}
)
switch link.Kind {
case messengertypes.BertyLink_ContactInviteV1Kind:
kind = "contact"
machine.BertyID = &messengertypes.BertyID{
PublicRendezvousSeed: link.BertyID.PublicRendezvousSeed,
AccountPK: link.BertyID.AccountPK,
}
if link.BertyID.DisplayName != "" {
human.Add("name", link.BertyID.DisplayName)
}
// for contact sharing, there are no fields to hide, so just copy the input link
*qrOptimized = *link
case messengertypes.BertyLink_GroupV1Kind:
kind = "group"
machine.BertyGroup = &messengertypes.BertyGroup{
Group: &protocoltypes.Group{
PublicKey: link.BertyGroup.Group.PublicKey,
Secret: link.BertyGroup.Group.Secret,
SecretSig: link.BertyGroup.Group.SecretSig,
GroupType: link.BertyGroup.Group.GroupType,
SignPub: link.BertyGroup.Group.SignPub,
LinkKeySig: link.BertyGroup.Group.LinkKeySig,
},
}
if link.BertyGroup.DisplayName != "" {
human.Add("name", link.BertyGroup.DisplayName)
}
*qrOptimized = *link
case messengertypes.BertyLink_EncryptedV1Kind:
kind = "enc"
machine.Encrypted = &messengertypes.BertyLink_Encrypted{
Kind: link.Encrypted.Kind,
Nonce: link.Encrypted.Nonce,
Checksum: link.Encrypted.Checksum,
}
if link.Encrypted.DisplayName != "" {
human.Add("name", link.Encrypted.DisplayName)
}
switch link.Encrypted.Kind {
case messengertypes.BertyLink_ContactInviteV1Kind:
machine.Encrypted.ContactAccountPK = link.Encrypted.ContactAccountPK
machine.Encrypted.ContactPublicRendezvousSeed = link.Encrypted.ContactPublicRendezvousSeed
case messengertypes.BertyLink_GroupV1Kind:
machine.Encrypted.GroupPublicKey = link.Encrypted.GroupPublicKey
machine.Encrypted.GroupSecret = link.Encrypted.GroupSecret
machine.Encrypted.GroupSecretSig = link.Encrypted.GroupSecretSig
machine.Encrypted.GroupSignPub = link.Encrypted.GroupSignPub
machine.Encrypted.GroupType = link.Encrypted.GroupType
machine.Encrypted.GroupLinkKeySig = link.Encrypted.GroupLinkKeySig
}
*qrOptimized = *link
case messengertypes.BertyLink_MessageV1Kind:
kind = "message"
machine.BertyMessageRef = &messengertypes.BertyLink_BertyMessageRef{
AccountID: link.BertyMessageRef.AccountID,
GroupPK: link.BertyMessageRef.GroupPK,
MessageID: link.BertyMessageRef.MessageID,
}
*qrOptimized = *link
default:
return "", "", errcode.ErrInvalidInput
}
// compute the web shareable link.
// in this mode, we have:
// - a human-readable link kind
// - a base58-encoded binary (proto) representation of the link (without the kind and metadata)
// - human-readable metadata, encoded as query string (including display name)
{
machineBin, err := proto.Marshal(machine)
if err != nil {
return "", "", errcode.ErrInvalidInput.Wrap(err)
}
// here we use base58 which is compressed enough whilst being easy to read by a human.
// another candidate could be base58.RawURLEncoding which is a little bit more compressed and also only containing unescaped URL chars.
machineEncoded := base58.Encode(machineBin)
path := kind + "/" + machineEncoded
if len(human) > 0 {
path += "/" + human.Encode()
}
// we use a '#' to improve privacy by preventing the webservers to get aware of the right part of this URL
web = LinkWebPrefix + path
}
// compute the internal shareable link.
// in this mode, the url is as short as possible, in the format: berty://{base45(proto.marshal(link))}.
{
qrBin, err := proto.Marshal(qrOptimized)
if err != nil {
return "", "", errcode.ErrInvalidInput.Wrap(err)
}
// using uppercase to stay in the QR AlphaNum's 45chars alphabet
internal = LinkInternalPrefix + "PB/" + qrBaseEncoder.Encode(qrBin)
}
return internal, web, nil
}
// UnmarshalLink takes an URL generated by BertyLink.Marshal (or manually crafted), and returns a BertyLink object.
func UnmarshalLink(uri string, key []byte) (*messengertypes.BertyLink, error) {
if uri == "" {
return nil, errcode.ErrMissingInput
}
// internal format
if strings.HasPrefix(strings.ToLower(uri), strings.ToLower(LinkInternalPrefix)) {
right := uri[len(LinkInternalPrefix):]
parts := strings.Split(right, "/")
if len(parts) < 2 {
return nil, errcode.ErrInvalidInput.Wrap(fmt.Errorf("URI should have at least 2 parts"))
}
switch strings.ToLower(parts[0]) {
case "pb":
blob := strings.Join(parts[1:], "/")
qrBin, err := qrBaseEncoder.Decode(blob)
if err != nil {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
var link messengertypes.BertyLink
err = proto.Unmarshal(qrBin, &link)
if err != nil {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
if link.Kind == messengertypes.BertyLink_EncryptedV1Kind {
return decryptLink(&link, key)
}
return &link, nil
default:
return nil, errcode.ErrInvalidInput.Wrap(fmt.Errorf("unsupported link type"))
}
}
// web format
if strings.HasPrefix(strings.ToLower(uri), strings.ToLower(LinkWebPrefix)) {
parsed, err := url.Parse(uri)
if err != nil {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
if parsed.Fragment == "" {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
rawFragment := strings.Join(strings.Split(uri, "#")[1:], "#") // required by go1.14
// when minimal version of berty will be go1.15, we can just use `parsed.EscapedFragment()`
link := messengertypes.BertyLink{}
parts := strings.Split(rawFragment, "/")
if len(parts) < 2 {
return nil, errcode.ErrInvalidInput.Wrap(fmt.Errorf("URI should have at least 2 parts"))
}
// decode blob
machineBin, err := base58.Decode(parts[1])
if err != nil {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
if err := proto.Unmarshal(machineBin, &link); err != nil {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
// decode url.Values
var human url.Values
if len(parts) > 2 {
encodedValues := strings.Join(parts[2:], "/")
human, err = url.ParseQuery(encodedValues)
if err != nil {
return nil, errcode.ErrInvalidInput.Wrap(err)
}
}
// per-kind merging strategies and checks
switch kind := parts[0]; kind {
case "contact":
link.Kind = messengertypes.BertyLink_ContactInviteV1Kind
if link.BertyID == nil {
link.BertyID = &messengertypes.BertyID{}
}
if name := human.Get("name"); name != "" && link.BertyID.DisplayName == "" {
link.BertyID.DisplayName = name
}
case "group":
link.Kind = messengertypes.BertyLink_GroupV1Kind
if link.BertyGroup == nil {
link.BertyGroup = &messengertypes.BertyGroup{}
}
if name := human.Get("name"); name != "" && link.BertyGroup.DisplayName == "" {
link.BertyGroup.DisplayName = name
}
case "enc":
link.Kind = messengertypes.BertyLink_EncryptedV1Kind
if link.Encrypted == nil {
return nil, errcode.ErrInvalidInput
}
if name := human.Get("name"); name != "" && link.Encrypted.DisplayName == "" {
link.Encrypted.DisplayName = name
}
case "message":
link.Kind = messengertypes.BertyLink_MessageV1Kind
if link.Encrypted == nil {
link.BertyMessageRef = &messengertypes.BertyLink_BertyMessageRef{}
}
default:
return nil, errcode.ErrInvalidInput
}
if link.Kind == messengertypes.BertyLink_EncryptedV1Kind {
return decryptLink(&link, key)
}
return &link, nil
}
return nil, errcode.ErrInvalidInput.Wrap(fmt.Errorf("unsupported link format"))
}
func decryptLink(link *messengertypes.BertyLink, passphrase []byte) (*messengertypes.BertyLink, error) {
if link == nil || link.Kind != messengertypes.BertyLink_EncryptedV1Kind {
return nil, errcode.ErrInvalidInput
}
if err := link.IsValid(); err != nil {
return nil, err
}
if passphrase == nil || string(passphrase) == "" {
return link, nil
}
decrypted := messengertypes.BertyLink{
Kind: link.Encrypted.Kind,
}
// derive key for AES
key, _, err := cryptoutil.DeriveKey(passphrase, link.Encrypted.Nonce)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
// create stream cipher
stream, err := cryptoutil.AESCTRStream(key, link.Encrypted.Nonce)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
switch decrypted.Kind {
case messengertypes.BertyLink_ContactInviteV1Kind:
decrypted.BertyID = &messengertypes.BertyID{
AccountPK: make([]byte, len(link.Encrypted.ContactAccountPK)),
PublicRendezvousSeed: make([]byte, len(link.Encrypted.ContactPublicRendezvousSeed)),
}
stream.XORKeyStream(decrypted.BertyID.PublicRendezvousSeed, link.Encrypted.ContactPublicRendezvousSeed)
stream.XORKeyStream(decrypted.BertyID.AccountPK, link.Encrypted.ContactAccountPK)
decrypted.BertyID.DisplayName = link.Encrypted.DisplayName
case messengertypes.BertyLink_GroupV1Kind:
decrypted.BertyGroup = &messengertypes.BertyGroup{
Group: &protocoltypes.Group{
PublicKey: make([]byte, len(link.Encrypted.GroupPublicKey)),
Secret: make([]byte, len(link.Encrypted.GroupSecret)),
SecretSig: make([]byte, len(link.Encrypted.GroupSecretSig)),
SignPub: make([]byte, len(link.Encrypted.GroupSignPub)),
LinkKeySig: make([]byte, len(link.Encrypted.GroupLinkKeySig)),
GroupType: link.Encrypted.GroupType,
},
}
stream.XORKeyStream(decrypted.BertyGroup.Group.PublicKey, link.Encrypted.GroupPublicKey)
stream.XORKeyStream(decrypted.BertyGroup.Group.Secret, link.Encrypted.GroupSecret)
stream.XORKeyStream(decrypted.BertyGroup.Group.SecretSig, link.Encrypted.GroupSecretSig)
stream.XORKeyStream(decrypted.BertyGroup.Group.SignPub, link.Encrypted.GroupSignPub)
stream.XORKeyStream(decrypted.BertyGroup.Group.LinkKeySig, link.Encrypted.GroupLinkKeySig)
decrypted.BertyGroup.DisplayName = link.Encrypted.DisplayName
}
if link.Encrypted.Checksum != nil && len(link.Encrypted.Checksum) > 0 {
checksum := make([]byte, len(link.Encrypted.Checksum))
err := clearLinkChecksum(&decrypted, checksum)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
if !bytes.Equal(link.Encrypted.Checksum, checksum) {
return nil, errcode.ErrMessengerDeepLinkInvalidPassphrase
}
}
return &decrypted, nil
}
// EncryptLink converts a clear BertyLink into an encrypted one.
//
// The encrypted link can be marshaled by UnmarshalLink if a passphrase is provided in the URL.
func EncryptLink(link *messengertypes.BertyLink, passphrase []byte) (*messengertypes.BertyLink, error) {
if link == nil {
return nil, errcode.ErrInvalidInput
}
encrypted := messengertypes.BertyLink{
Kind: messengertypes.BertyLink_EncryptedV1Kind,
Encrypted: &messengertypes.BertyLink_Encrypted{
Kind: link.Kind, // inherit kind from the clear link.
},
}
if link.Encrypted != nil {
// if display name is set in the encrypted part of the input link,
// then we want the display name to be available in the generated URL.
encrypted.Encrypted.DisplayName = link.Encrypted.DisplayName
// if checksum is set, it will be the size of the hash (SHAKE256).
encrypted.Encrypted.Checksum = link.Encrypted.Checksum
}
if encrypted.Encrypted.Checksum == nil {
encrypted.Encrypted.Checksum = make([]byte, DefaultChecksumSize)
}
// generate nonce with AES' blocksize
nonce, err := cryptoutil.GenerateNonceSize(aes.BlockSize)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
encrypted.Encrypted.Nonce = nonce
// derive key for AES
key, _, err := cryptoutil.DeriveKey(passphrase, nonce)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
// encrypt
stream, err := cryptoutil.AESCTRStream(key, nonce)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
switch link.Kind {
case messengertypes.BertyLink_ContactInviteV1Kind:
if link.BertyID == nil {
return nil, errcode.ErrInvalidInput
}
// encrypt fields (order is important)
encrypted.Encrypted.ContactPublicRendezvousSeed = make([]byte, len(link.BertyID.PublicRendezvousSeed))
encrypted.Encrypted.ContactAccountPK = make([]byte, len(link.BertyID.AccountPK))
stream.XORKeyStream(encrypted.Encrypted.ContactPublicRendezvousSeed, link.BertyID.PublicRendezvousSeed)
stream.XORKeyStream(encrypted.Encrypted.ContactAccountPK, link.BertyID.AccountPK)
encrypted.Encrypted.DisplayName = link.BertyID.DisplayName
case messengertypes.BertyLink_GroupV1Kind:
if link.BertyGroup == nil || link.BertyGroup.Group == nil {
return nil, errcode.ErrInvalidInput
}
// only field that stays clear
encrypted.Encrypted.GroupType = link.BertyGroup.Group.GroupType
// encrypt fields (order is important)
encrypted.Encrypted.GroupPublicKey = make([]byte, len(link.BertyGroup.Group.PublicKey))
encrypted.Encrypted.GroupSecret = make([]byte, len(link.BertyGroup.Group.Secret))
encrypted.Encrypted.GroupSecretSig = make([]byte, len(link.BertyGroup.Group.SecretSig))
encrypted.Encrypted.GroupSignPub = make([]byte, len(link.BertyGroup.Group.SignPub))
encrypted.Encrypted.GroupLinkKeySig = make([]byte, len(link.BertyGroup.Group.LinkKeySig))
stream.XORKeyStream(encrypted.Encrypted.GroupPublicKey, link.BertyGroup.Group.PublicKey)
stream.XORKeyStream(encrypted.Encrypted.GroupSecret, link.BertyGroup.Group.Secret)
stream.XORKeyStream(encrypted.Encrypted.GroupSecretSig, link.BertyGroup.Group.SecretSig)
stream.XORKeyStream(encrypted.Encrypted.GroupSignPub, link.BertyGroup.Group.SignPub)
stream.XORKeyStream(encrypted.Encrypted.GroupLinkKeySig, link.BertyGroup.Group.LinkKeySig)
encrypted.Encrypted.DisplayName = link.BertyGroup.DisplayName
default:
return nil, errcode.ErrInvalidInput
}
if encrypted.Encrypted.Checksum != nil && len(encrypted.Encrypted.Checksum) > 0 {
err := clearLinkChecksum(link, encrypted.Encrypted.Checksum)
if err != nil {
return nil, errcode.ErrInternal.Wrap(err)
}
}
return &encrypted, nil
}
func clearLinkChecksum(link *messengertypes.BertyLink, dest []byte) error {
// compute the hash based on every field that can be encrypted, even if they're empty.
// the order is important.
hasher := sha3.NewShake256()
// contact v1
if link.BertyID != nil {
for _, b := range [][]byte{
link.BertyID.PublicRendezvousSeed,
link.BertyID.AccountPK,
} {
_, err := hasher.Write(b)
if err != nil {
return errcode.ErrInternal.Wrap(err)
}
}
}
// group v1
if link.BertyGroup != nil && link.BertyGroup.Group != nil {
for _, b := range [][]byte{
link.BertyGroup.Group.PublicKey,
link.BertyGroup.Group.Secret,
link.BertyGroup.Group.SecretSig,
link.BertyGroup.Group.SignPub,
} {
_, err := hasher.Write(b)
if err != nil {
return errcode.ErrInternal.Wrap(err)
}
}
}
_, err := hasher.Read(dest)
if err != nil {
return errcode.ErrInternal.Wrap(err)
}
return nil
}
func InternalLinkToMessage(accountID, groupPK, cid string) (string, error) {
if accountID == "" {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("account id should not be empty"))
}
if groupPK == "" {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("group pk should not be empty"))
}
if cid == "" {
return "", errcode.ErrInvalidInput.Wrap(fmt.Errorf("message cid should not be empty"))
}
internal, _, err := MarshalLink(&messengertypes.BertyLink{
BertyMessageRef: &messengertypes.BertyLink_BertyMessageRef{
AccountID: accountID,
GroupPK: groupPK,
MessageID: cid,
},
Kind: messengertypes.BertyLink_MessageV1Kind,
})
if err != nil {
return "", errcode.ErrSerialization.Wrap(err)
}
return internal, nil
}
const (
LinkWebPrefix = "https://berty.tech/id#"
LinkInternalPrefix = "BERTY://"
DefaultChecksumSize = 1 // 1-byte length by default (should have ~1/256 false-positive in case of invalid password)
)
// from https://www.swisseduc.ch/informatik/theoretische_informatik/qr_codes/docs/qr_standard.pdf
//
// Alphanumeric Mode encodes data from a set of 45 characters, i.e.
// - 10 numeric digits (0 - 9) (ASCII values 30 to 39),
// - 26 alphabetic characters (A - Z) (ASCII values 41 to 5A),
// - and 9 symbols (SP, $, %, *, +, -, ., /, :) (ASCII values 20, 24, 25, 2A, 2B, 2D to 2F, 3A).
//
// we remove SP, %, +, which changes when passed through url.Encode.
//
// the generated string is longer than a base58 one, but the generated QR code is smaller which is best for scanning.
var qrBaseEncoder, _ = basex.NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789$*-.:/")