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token.go
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token.go
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// Copyright The Athenz Authors
// Licensed under the terms of the Apache version 2.0 license. See LICENSE file for terms.
// Package zmssvctoken produces and validates ntokens given appropriate keys.
// It can only produce service tokens but can validate any principal token.
package zmssvctoken
import (
"fmt"
"log"
"strconv"
"strings"
"sync"
"time"
)
const (
defaultTokenVersion = "S1"
)
var expirationDrift = 10 * time.Minute
const (
tagVersion = "v"
tagDomain = "d"
tagName = "n"
tagKeyVersion = "k"
tagHostname = "h"
tagIP = "i"
tagGenerationTime = "t"
tagExpireTime = "e"
tagSalt = "a"
tagSignature = "s"
tagKeyService = "z"
)
// NToken provides access to useful fields in an ntoken.
type NToken struct {
Version string // the token version e.g. S1, U1
Domain string // domain for which token is valid
Name string // local principal name
KeyVersion string // key version as registered in Athenz
KeyService string // optional key service
Hostname string // optional hostname
IPAddress string // optional IP address
GenerationTime time.Time // time token was generated
ExpiryTime time.Time // time token expires
}
// PrincipalName returns the fully qualified principal name for the token.
func (n *NToken) PrincipalName() string {
return n.Domain + "." + n.Name
}
// IsExpired is a convenience function to check token expiry.
func (n *NToken) IsExpired() bool {
return n.ExpiryTime.Before(time.Now())
}
func (n *NToken) almostExpired() bool {
return time.Now().After(n.ExpiryTime.Add(-1 * expirationDrift))
}
func (n *NToken) toSignedToken(s Signer, expiration time.Duration) (string, error) {
n.GenerationTime = time.Now()
n.ExpiryTime = n.GenerationTime.Add(expiration)
var parts []string
add := func(k, v string) {
parts = append(parts, fmt.Sprintf("%s=%s", k, v))
}
add(tagVersion, n.Version)
add(tagDomain, n.Domain)
add(tagName, n.Name)
add(tagKeyVersion, n.KeyVersion)
if n.KeyService != "" {
add(tagKeyService, n.KeyService)
}
if n.Hostname != "" {
add(tagHostname, n.Hostname)
}
if n.IPAddress != "" {
add(tagIP, n.IPAddress)
}
salt, err := getSalt()
if err != nil {
return "", fmt.Errorf("Salt error: %v", err)
}
add(tagSalt, salt)
add(tagGenerationTime, fmt.Sprintf("%d", n.GenerationTime.Unix()))
add(tagExpireTime, fmt.Sprintf("%d", n.ExpiryTime.Unix()))
unsignedToken := strings.Join(parts, ";")
signature, err := s.Sign(unsignedToken)
if err != nil {
return "", fmt.Errorf("Signature error: %v", err)
}
return unsignedToken + fmt.Sprintf(";%s=", tagSignature) + signature, nil
}
var zeroTime = time.Time{}
func asTime(s, name string) (time.Time, error) {
n, err := strconv.ParseInt(s, 10, 64)
if err != nil {
return zeroTime, fmt.Errorf("Invalid field value '%s' for field '%s'", s, name)
}
return time.Unix(n, 0), nil
}
func (n *NToken) assertValid() error {
if n.Version == "" {
return fmt.Errorf("Invalid token: missing version")
}
if n.Domain == "" {
return fmt.Errorf("Invalid token: missing domain")
}
if n.Name == "" {
return fmt.Errorf("Invalid token: missing name")
}
if n.KeyVersion == "" {
return fmt.Errorf("Invalid token: missing key version")
}
if n.GenerationTime.IsZero() {
return fmt.Errorf("Invalid token: missing generation time")
}
if n.ExpiryTime.IsZero() {
return fmt.Errorf("Invalid token: missing expiry time")
}
return nil
}
func (n *NToken) load(tok string, verifier Verifier) error {
delim := fmt.Sprintf(";%s=", tagSignature)
usig := strings.SplitN(tok, delim, 2)
if len(usig) != 2 {
return fmt.Errorf("Token does not have a signature")
}
unsignedToken := usig[0]
signature := usig[1]
err := verifier.Verify(unsignedToken, signature)
if err != nil {
return fmt.Errorf("Invalid token signature")
}
parts := strings.Split(unsignedToken, ";")
for _, part := range parts {
inner := strings.SplitN(part, "=", 2)
if len(inner) != 2 {
return fmt.Errorf("Malformed token field %s", part)
}
v := inner[1]
switch inner[0] {
case tagVersion:
n.Version = v
case tagDomain:
n.Domain = v
case tagName:
n.Name = v
case tagKeyVersion:
n.KeyVersion = v
case tagHostname:
n.Hostname = v
case tagIP:
n.IPAddress = v
case tagKeyService:
n.KeyService = v
case tagGenerationTime:
if n.GenerationTime, err = asTime(v, tagGenerationTime); err != nil {
return err
}
case tagExpireTime:
if n.ExpiryTime, err = asTime(v, tagExpireTime); err != nil {
return err
}
case tagSalt, tagSignature:
// ignore
default:
log.Println("Unknown ntoken field: ", v)
}
}
return n.assertValid()
}
func (n *NToken) String() string {
parts := []string{
fmt.Sprintf("Version: %v", n.Version),
fmt.Sprintf("Domain: %v", n.Domain),
fmt.Sprintf("Name: %v", n.Name),
fmt.Sprintf("Key version: %v", n.KeyVersion),
fmt.Sprintf("Key service: %v", n.KeyService),
fmt.Sprintf("Hostname: %v", n.Hostname),
fmt.Sprintf("I/P: %v", n.IPAddress),
fmt.Sprintf("Created on: %v", n.GenerationTime),
fmt.Sprintf("Expires: %v", n.ExpiryTime),
}
return strings.Join(parts, "\n")
}
// Token is a mechanism to get an ntoken as a string.
// It guarantees that the returned token has not expired.
type Token interface {
// Value returns the value of the current token or
// an error if it couldn't be generated for any reason.
Value() (string, error)
}
// TokenBuilder provides a mechanism to set optional ntoken attributes and
// a means to get the token value with efficient auto-refresh.
type TokenBuilder interface {
// SetExpiration sets the duration for which the token is valid (default=1h).
SetExpiration(t time.Duration)
// SetHostname sets the hostname for the token (default=current hostname).
SetHostname(h string)
// SetIPAddress sets the IP address for the token (default=host IP address).
SetIPAddress(ip string)
// SetKeyService sets the key service for the token
SetKeyService(keyService string)
// Token returns a Token instance with the fields correctly set for
// the current token. Multiple calls to Token will return the same implementation.
// If you change optional attributes between calls to Token, these will have no effect.
Token() Token
}
// tokenBuilder implements TokenBuilder
type tokenBuilder struct {
signer Signer
ntok *NToken
expiration time.Duration
l sync.Mutex
tok *token
}
// NewTokenBuilder returns a TokenBuilder implementation for the specified
// domain/name, with a private key (PEM format) and its key-version. The key-version
// should be the same string that was used to register the key with Athenz.
func NewTokenBuilder(domain, name string, privateKeyPEM []byte, keyVersion string) (TokenBuilder, error) {
s, err := NewSigner(privateKeyPEM)
if err != nil {
return nil, fmt.Errorf("Unable to create signer: %v", err)
}
exp := time.Hour
ntok := &NToken{
Domain: domain,
Name: name,
KeyVersion: keyVersion,
Version: defaultTokenVersion,
Hostname: defaultHostname(),
IPAddress: defaultIP(),
GenerationTime: time.Now().Add(-2 * exp),
ExpiryTime: time.Now().Add(-1 * exp), // start out as expired
}
err = ntok.assertValid()
if err != nil {
return nil, err
}
return &tokenBuilder{
signer: s,
ntok: ntok,
expiration: exp,
}, nil
}
func (t *tokenBuilder) SetExpiration(e time.Duration) {
t.expiration = e
}
func (t *tokenBuilder) SetHostname(h string) {
t.ntok.Hostname = h
}
func (t *tokenBuilder) SetIPAddress(v string) {
t.ntok.IPAddress = v
}
func (t *tokenBuilder) SetKeyService(keyService string) {
t.ntok.KeyService = keyService
}
func (t *tokenBuilder) Token() Token {
t.l.Lock()
defer t.l.Unlock()
if t.tok == nil {
t.tok = &token{
signer: t.signer,
ntok: t.ntok,
expiration: t.expiration,
}
}
return t.tok
}
type token struct {
sync.Mutex
signer Signer
ntok *NToken
expiration time.Duration
cachedToken string
}
func (t *token) Value() (string, error) {
t.Lock()
defer t.Unlock()
if t.ntok.almostExpired() {
v, err := t.ntok.toSignedToken(t.signer, t.expiration)
if err != nil {
return "", err
}
t.cachedToken = v
}
return t.cachedToken, nil
}
// TokenValidator provides a mechanism to validate tokens.
type TokenValidator interface {
// Validate returns an unexpired NToken object from its
// string representation.
Validate(token string) (*NToken, error)
}
type tokenValidator struct {
verifier Verifier
}
func (tv *tokenValidator) Validate(token string) (*NToken, error) {
ntok := &NToken{}
err := ntok.load(token, tv.verifier)
if err != nil {
return nil, err
}
if ntok.IsExpired() {
return nil, fmt.Errorf("Token has expired")
}
return ntok, nil
}
// NewPubKeyTokenValidator returns NToken objects from signed token strings
// given a public key to verify signatures.
func NewPubKeyTokenValidator(publicKeyPEM []byte) (TokenValidator, error) {
v, err := NewVerifier(publicKeyPEM)
if err != nil {
return nil, fmt.Errorf("Unable to create verifier: %v", err)
}
return &tokenValidator{
verifier: v,
}, nil
}
// ValidationConfig contains data to change runtime parameters from the default values.
type ValidationConfig struct {
ZTSBaseUrl string // the ZTS base url including the /zts/v1 version path, default
PublicKeyFetchTimeout time.Duration // timeout for fetching the public key from ZTS, default: 5s
CacheTTL time.Duration // TTL for cached public keys, default: 10 minutes
sysAuthDomain string // domain for the ZMS / ZTS service itself
zmsService string // service name for the ZMS service
ztsService string // service name for the ZTS service
}
// NewTokenValidator returns NToken objects from signed token strings.
// It automatically fetches the required public key for validation from ZTS
// based on the token contents. You can optionally pass in a validation config
// object to change runtime parameters from the default values.
func NewTokenValidator(config ...ValidationConfig) TokenValidator {
cfg := &ValidationConfig{
ZTSBaseUrl: "https://localhost:4443/zts/v1",
PublicKeyFetchTimeout: 5 * time.Second,
CacheTTL: 10 * time.Minute,
sysAuthDomain: "sys.auth",
zmsService: "zms",
ztsService: "zts",
}
for _, c := range config {
if c.ZTSBaseUrl != "" {
cfg.ZTSBaseUrl = c.ZTSBaseUrl
}
if c.PublicKeyFetchTimeout != 0 {
cfg.PublicKeyFetchTimeout = c.PublicKeyFetchTimeout
}
if c.CacheTTL != 0 {
cfg.CacheTTL = c.CacheTTL
}
}
return newAutoTokenValidator(cfg)
}
type nopVerifier struct {
}
func (nv *nopVerifier) Verify(input, signature string) error {
return nil
}
type autoTokenValidator struct {
config *ValidationConfig
store *keyStore
initialVerifier Verifier
}
func newAutoTokenValidator(cfg *ValidationConfig) *autoTokenValidator {
return &autoTokenValidator{
config: cfg,
store: newKeyStore(cfg),
initialVerifier: &nopVerifier{},
}
}
func (a *autoTokenValidator) Validate(token string) (*NToken, error) {
t := &NToken{}
err := t.load(token, a.initialVerifier)
if err != nil {
return nil, err
}
src := keySource{keyVersion: t.KeyVersion}
if t.KeyService != "" && t.KeyService == a.config.zmsService {
src.domain = a.config.sysAuthDomain
src.name = a.config.zmsService
} else if t.KeyService != "" && t.KeyService == a.config.ztsService {
src.domain = a.config.sysAuthDomain
src.name = a.config.ztsService
} else if len(t.Version) > 0 && t.Version[0] == 'U' { // user principal, use ZMS's public key
src.domain = a.config.sysAuthDomain
src.name = a.config.zmsService
} else {
src.domain = t.Domain
src.name = t.Name
}
validator, err := a.store.getValidator(src)
if err != nil {
return nil, err
}
return validator.Validate(token)
}