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key_manager.go
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key_manager.go
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package vfy
import (
"context"
"errors"
"log"
"sync"
"github.com/adem-wg/adem-proto/pkg/roots"
"github.com/adem-wg/adem-proto/pkg/tokens"
"github.com/adem-wg/adem-proto/pkg/util"
"github.com/lestrrat-go/jwx/v2/jwa"
"github.com/lestrrat-go/jwx/v2/jwk"
"github.com/lestrrat-go/jwx/v2/jws"
"github.com/lestrrat-go/jwx/v2/jwt"
)
var ErrNoKeyFound = errors.New("no key found")
var ErrRootKeyUnbound = errors.New("root key not properly committed")
var ErrAlgsDiffer = errors.New("jws alg and verification key alg are different")
var ErrLogsEmpty = errors.New("logs field cannot be empty")
// A struct that implements the [jwt.KeyProvider] interface.
type keyManager struct {
// Lock for map access
lock sync.Mutex
// Wait group that will be done once all verification threads obtained a
// promise for their verification key.
init sync.WaitGroup
// Maps KIDs to keys. Only contains verified keys.
keys map[string]jwk.Key
// Promises waiting for keys.
listeners map[string][]util.Promise[jwk.Key]
}
// Creates a new key manager to verify [numThreads]-many tokens asynchronously.
func NewKeyManager(numThreads int) *keyManager {
var km keyManager
km.init.Add(numThreads)
km.keys = make(map[string]jwk.Key)
km.listeners = make(map[string][]util.Promise[jwk.Key])
return &km
}
// Wait until all verification threads obtained a promise for their verification
// key.
func (km *keyManager) waitForInit() {
km.init.Wait()
}
// Cancel any further verification.
func (km *keyManager) killListeners() {
km.lock.Lock()
defer km.lock.Unlock()
for k, listeners := range km.listeners {
for _, promise := range listeners {
promise.Reject()
}
delete(km.listeners, k)
}
}
// How many blocked threads are there that wait for a key promise to be resolved?
func (km *keyManager) waiting() int {
km.lock.Lock()
defer km.lock.Unlock()
sum := 0
for _, listeners := range km.listeners {
sum += len(listeners)
}
return sum
}
// Store a verified key and notify listeners waiting for that key.
func (km *keyManager) put(k jwk.Key) bool {
km.lock.Lock()
defer km.lock.Unlock()
kid, err := tokens.GetKID(k)
if err != nil {
return false
} else if fp, err := tokens.CalcKID(k); err != nil {
// We set and calculate the KID ID to be consistent with key hashing later
// down the line.
return false
} else if err := k.Set("kid", fp); err != nil {
return false
}
_, ok := km.keys[kid]
if ok {
return false
}
km.keys[kid] = k
promises := km.listeners[kid]
if len(promises) == 0 {
return false
}
for _, promise := range promises {
if promise != nil {
promise.Fulfill(k)
}
}
delete(km.listeners, kid)
return true
}
// Get a key based on its [kid]. Returns a promise that may already be resolved.
func (km *keyManager) get(kid string) util.Promise[jwk.Key] {
km.lock.Lock()
defer km.lock.Unlock()
c := util.NewPromise[jwk.Key]()
k, ok := km.keys[kid]
if ok {
c.Fulfill(k)
} else {
km.listeners[kid] = append(km.listeners[kid], c)
}
return c
}
func (km *keyManager) getVerificationKey(sig *jws.Signature) util.Promise[jwk.Key] {
if headerKID := sig.ProtectedHeaders().KeyID(); headerKID != "" {
return km.get(headerKID)
} else if sig.ProtectedHeaders().JWK().KeyID() != "" {
return km.get(sig.ProtectedHeaders().JWK().KeyID())
} else {
return util.Rejected[jwk.Key]()
}
}
// Implements the [jwt.KeyManager] interface. If the token includes a root key,
// the root key commitment will be verified, and when this succeeds, the root
// key will be used for verification. All other keys will register a listener
// and wait for their verification key to be verified externally.
func (km *keyManager) FetchKeys(ctx context.Context, sink jws.KeySink, sig *jws.Signature, m *jws.Message) error {
var promise util.Promise[jwk.Key]
var err error
if t, e := jwt.Parse(m.Payload(), jwt.WithVerify(false)); e != nil {
log.Printf("could not decode payload: %s", e)
err = e
} else if logs, ok := t.Get("log"); ok {
headerKey := sig.ProtectedHeaders().JWK()
for _, r := range roots.VerifyBindingCerts(t.Issuer(), headerKey, logs.([]*tokens.LogConfig)) {
if !r.Ok {
log.Printf("could not verify root key commitment for log ID %s", r.LogID)
err = ErrRootKeyUnbound
break
}
}
if len(logs.([]*tokens.LogConfig)) == 0 {
err = ErrLogsEmpty
}
if err == nil {
km.put(headerKey)
}
}
promise = km.getVerificationKey(sig)
km.init.Done()
if err != nil {
log.Printf("err: %s", err)
return err
}
verificationKey := promise.Get()
if verificationKey == nil {
return ErrNoKeyFound
}
if verificationKey.Algorithm() != sig.ProtectedHeaders().Algorithm() {
return ErrAlgsDiffer
}
sink.Key(jwa.SignatureAlgorithm(verificationKey.Algorithm().String()), verificationKey)
return nil
}