// ReadKeyfile reads a randomly generated and encrypted AES-256 key from the
// file with the given filename and returns it in unencrypted form.
// The key is protected by a passphrase, which is processed by PBKDF2 to
// derive the AES-256 key to decrypt the generated key.
func ReadKeyfile(filename string, passphrase []byte) (key []byte, err error) {
// open keyfile
keyfile, err := os.Open(filename)
if err != nil {
return nil, log.Error(err)
}
defer keyfile.Close()
// read iter and convert to int
var biter = make([]byte, 8)
if _, err := keyfile.Read(biter); err != nil {
return nil, log.Error(err)
}
uiter := encode.ToUint64(biter)
if uiter > 2147483647 {
return nil, log.Errorf("encdb: ReadKeyfile: invalid iter value")
}
iter := int(uiter)
// read salt
var salt = make([]byte, 32)
if _, err := keyfile.Read(salt); err != nil {
return nil, log.Error(err)
}
// read encrypted key
var encKey = make([]byte, 16+32)
if _, err := keyfile.Read(encKey); err != nil {
return nil, log.Error(err)
}
// compute derived key from passphrase
dk := pbkdf2.Key([]byte(passphrase), salt, iter, 32, sha256.New)
// decrypt key
return cipher.AES256CBCDecrypt([]byte(dk), encKey), nil
}
func (ce *CryptEngine) lookupHashChain(id string) error {
// map identity
mappedID, domain, err := identity.MapPlus(id)
if err != nil {
return err
}
// get JSON-RPC client
client, _, err := ce.cache.Get(domain, ce.keydPort, ce.keydHost, ce.homedir,
"KeyHashchain.LookupUID")
if err != nil {
return err
}
// Call KeyHashchain.LookupUID
content := make(map[string]interface{})
content["Identity"] = mappedID
reply, err := client.JSONRPCRequest("KeyHashchain.LookupUID", content)
if err != nil {
return err
}
hcPositions, ok := reply["HCPositions"].([]interface{})
if !ok {
if _, ok := reply["HCPositions"].(interface{}); !ok {
return log.Errorf("lookup found no entry of id '%s'", id)
}
return log.Error("cryptengine: lookup ID reply has the wrong type")
}
var TYPE, NONCE, HashID, CrUID, UIDIndex []byte
var matchFound bool
for k, v := range hcPositions {
hcPosFloat, ok := v.(float64)
if !ok {
return log.Errorf("cryptengine: lookup ID reply position entry %d has the wrong type", k)
}
hcPos := uint64(hcPosFloat)
hcEntry, err := ce.keyDB.GetHashChainEntry(domain, hcPos)
if err != nil {
return err
}
_, TYPE, NONCE, HashID, CrUID, UIDIndex, err = hashchain.SplitEntry(hcEntry)
if err != nil {
return err
}
if !bytes.Equal(TYPE, hashchain.Type) {
return log.Error("cryptengine: invalid entry type")
}
// Compute k1, k2 = CKDF(NONCE)
k1, k2 := cipher.CKDF(NONCE)
// Compute: HashIDTest = HASH(k1 | Identity)
tmp := make([]byte, len(k1)+len(mappedID))
copy(tmp, k1)
copy(tmp[len(k1):], mappedID)
HashIDTest := cipher.SHA256(tmp)
// If NOT: HashID == HashIDTest: Continue
if !bytes.Equal(HashID, HashIDTest) {
return log.Error("cryptengine: lookup ID returned bogus position")
}
log.Debugf("cryptengine: UIDIndex=%s", base64.Encode(UIDIndex))
// Check UID already exists in keyDB
_, pos, found, err := ce.keyDB.GetPublicUID(mappedID, hcPos)
if err != nil {
return err
}
if found && pos == hcPos {
// UID exists already -> skip entry
matchFound = true
continue
}
// Compute: IDKEY = HASH(k2 | Identity)
tmp = make([]byte, len(k2)+len(mappedID))
copy(tmp, k2)
copy(tmp[len(k2):], mappedID)
IDKEY := cipher.SHA256(tmp)
// Fetch from Key Repository: UIDMessageReply = GET(UIDIndex)
msgReply, err := ce.fetchUID(domain, UIDIndex)
if err != nil {
return err
}
// Decrypt UIDHash = AES_256_CBC_Decrypt( IDKEY, CrUID)
UIDHash := cipher.AES256CBCDecrypt(IDKEY, CrUID)
log.Debugf("cryptengine: UIDHash=%s", base64.Encode(UIDHash))
// Decrypt UIDMessageReply.UIDMessage with UIDHash
index, uid, err := msgReply.Decrypt(UIDHash)
if err != nil {
return err
}
log.Debugf("cryptengine: UIDMessage=%s", uid.JSON())
// Check index
if !bytes.Equal(index, UIDIndex) {
return log.Errorf("cryptengine: index != UIDIndex")
}
// Verify self signature
if err := uid.VerifySelfSig(); err != nil {
return log.Error(err)
}
// Verify server signature
if err := ce.verifyServerSig(uid, msgReply, hcPos); err != nil {
return err
}
// TODO: make sure the whole chain of UIDMessages is valid
// Store UIDMessage
if err := ce.keyDB.AddPublicUID(uid, hcPos); err != nil {
return err
}
matchFound = true
// If no further entry can be found, the latest UIDMessage entry has been found
}
if matchFound {
return nil
}
return log.Errorf("lookup found no entry of id '%s'", id)
}
// searchHashChain searches the local hash chain corresponding to the given id
// for the id. It talks to the corresponding key server to retrieve necessary
// UIDMessageReplys and stores found UIDMessages in the local keyDB.
func (ce *CryptEngine) searchHashChain(id string, searchOnly bool) error {
// map identity
mappedID, domain, err := identity.MapPlus(id)
if err != nil {
return err
}
// make sure we have a hashchain for the given domain
max, found, err := ce.keyDB.GetLastHashChainPos(domain)
if err != nil {
return err
}
if !found {
return log.Errorf("no hash chain entries found for domain '%s'", domain)
}
var TYPE, NONCE, HashID, CrUID, UIDIndex []byte
var matchFound bool
for i := uint64(0); i <= max; i++ {
hcEntry, err := ce.keyDB.GetHashChainEntry(domain, i)
if err != nil {
return err
}
log.Debugf("cryptengine: search hash chain entry %d: %s", i, hcEntry)
_, TYPE, NONCE, HashID, CrUID, UIDIndex, err = hashchain.SplitEntry(hcEntry)
if err != nil {
return err
}
if !bytes.Equal(TYPE, hashchain.Type) {
return log.Error("cryptengine: invalid hash chain entry type")
}
// Compute k1, k2 = CKDF(NONCE)
k1, k2 := cipher.CKDF(NONCE)
// Compute: HashIDTest = HASH(k1 | Identity)
tmp := make([]byte, len(k1)+len(mappedID))
copy(tmp, k1)
copy(tmp[len(k1):], mappedID)
HashIDTest := cipher.SHA256(tmp)
// If NOT: HashID == HashIDTest: Continue
if !bytes.Equal(HashID, HashIDTest) {
continue
}
if searchOnly {
return nil
}
log.Debugf("cryptengine: UIDIndex=%s", base64.Encode(UIDIndex))
// Check UID already exists in keyDB
_, pos, found, err := ce.keyDB.GetPublicUID(mappedID, i)
if err != nil {
return err
}
if found && pos == i {
// UID exists already -> skip entry
matchFound = true
continue
}
// Compute: IDKEY = HASH(k2 | Identity)
tmp = make([]byte, len(k2)+len(mappedID))
copy(tmp, k2)
copy(tmp[len(k2):], mappedID)
IDKEY := cipher.SHA256(tmp)
// Fetch from Key Repository: UIDMessageReply = GET(UIDIndex)
msgReply, err := ce.fetchUID(domain, UIDIndex)
if err != nil {
return err
}
// Decrypt UIDHash = AES_256_CBC_Decrypt( IDKEY, CrUID)
UIDHash := cipher.AES256CBCDecrypt(IDKEY, CrUID)
log.Debugf("cryptengine: UIDHash=%s", base64.Encode(UIDHash))
// Decrypt UIDMessageReply.UIDMessage with UIDHash
index, uid, err := msgReply.Decrypt(UIDHash)
if err != nil {
return err
}
log.Debugf("cryptengine: UIDMessage=%s", uid.JSON())
// Check index
if !bytes.Equal(index, UIDIndex) {
return log.Errorf("cryptengine: index != UIDIndex")
}
// Verify self signature
if err := uid.VerifySelfSig(); err != nil {
return log.Error(err)
}
// Verify server signature
if err := ce.verifyServerSig(uid, msgReply, i); err != nil {
return err
}
// TODO: make sure the whole chain of UIDMessages is valid
// Store UIDMessage
if err := ce.keyDB.AddPublicUID(uid, i); err != nil {
return err
}
matchFound = true
// If no further entry can be found, the latest UIDMessage entry has been found
}
if matchFound {
return nil
}
return log.Errorf("no hash chain entry found of id '%s'", id)
}