validate header auth on proxy

proxy/internal/auth/header.go

@@ -1,36 +1,32 @@
 package auth
 
 import (
-	"errors"
-	"fmt"
+	"crypto/sha256"
 	"net/http"
+	"sync"
 
 	"github.com/netbirdio/netbird/proxy/auth"
-	"github.com/netbirdio/netbird/proxy/internal/types"
-	"github.com/netbirdio/netbird/shared/management/proto"
+	"github.com/netbirdio/netbird/shared/hash/argon2id"
 )
 
-// ErrHeaderAuthFailed indicates that the header was present but the
-// credential did not validate. Callers should return 401 instead of
-// falling through to other auth schemes.
-var ErrHeaderAuthFailed = errors.New("header authentication failed")
-
-// Header implements header-based authentication. The proxy checks for the
-// configured header in each request and validates its value via gRPC.
+// Header implements header-based authentication. The service mapping carries
+// the argon2id hash of every value accepted for the header, so the proxy
+// verifies the credential locally rather than round-tripping to management.
 type Header struct {
-	id         types.ServiceID
-	accountId  types.AccountID
 	headerName string
-	client     authenticator
+	hashes     []string
+	verified   *verifiedValues
 }
 
-// NewHeader creates a Header authentication scheme for the given header name.
-func NewHeader(client authenticator, id types.ServiceID, accountId types.AccountID, headerName string) Header {
+// NewHeader creates a Header authentication scheme accepting any value whose
+// argon2id hash appears in hashes. An empty hashes slice rejects every request
+// carrying the header, so a mapping that arrived without its hashes fails
+// closed instead of leaving the service unprotected.
+func NewHeader(headerName string, hashes []string) Header {
 	return Header{
-		id:         id,
-		accountId:  accountId,
-		headerName: headerName,
-		client:     client,
+		headerName: http.CanonicalHeaderKey(headerName),
+		hashes:     hashes,
+		verified:   &verifiedValues{seen: make(map[[32]byte]struct{}, len(hashes))},
 	}
 }
 
@@ -39,31 +35,55 @@ func (Header) Type() auth.Method {
 	return auth.MethodHeader
 }
 
-// Authenticate checks for the configured header in the request. If absent,
-// returns empty (unauthenticated). If present, validates via gRPC.
-func (h Header) Authenticate(r *http.Request) (string, string, error) {
+// Authenticate satisfies Scheme. Header credentials are resolved by Verify
+// before the scheme loop runs, so a request that reaches here never carries
+// the header and there is no credential to prompt for.
+func (Header) Authenticate(*http.Request) (string, string, error) {
+	return "", "", nil
+}
+
+// Verify reports whether the request carries the configured header and, when
+// it does, whether the value matches one of the service's hashes.
+func (h Header) Verify(r *http.Request) (present, matched bool) {
 	value := r.Header.Get(h.headerName)
 	if value == "" {
-		return "", "", nil
+		return false, false
 	}
 
-	res, err := h.client.Authenticate(r.Context(), &proto.AuthenticateRequest{
-		Id:        string(h.id),
-		AccountId: string(h.accountId),
-		Request: &proto.AuthenticateRequest_HeaderAuth{
-			HeaderAuth: &proto.HeaderAuthRequest{
-				HeaderValue: value,
-				HeaderName:  h.headerName,
-			},
-		},
-	})
-	if err != nil {
-		return "", "", fmt.Errorf("authenticate header: %w", err)
+	digest := sha256.Sum256([]byte(value))
+	if h.verified.has(digest) {
+		return true, true
 	}
 
-	if res.GetSuccess() {
-		return res.GetSessionToken(), "", nil
+	for _, hash := range h.hashes {
+		if argon2id.Verify(value, hash) == nil {
+			h.verified.add(digest)
+			return true, true
+		}
 	}
+	return true, false
+}
 
-	return "", "", ErrHeaderAuthFailed
+// verifiedValues remembers which header values already passed argon2id
+// verification. argon2id is deliberately expensive (19 MiB, two passes) and
+// header credentials repeat on every request, so re-deriving per request would
+// dominate the hot path. The set cannot outgrow the number of configured
+// hashes, and a mapping update builds a fresh scheme with an empty set.
+// Values are keyed by digest so the plaintext credential is not retained.
+type verifiedValues struct {
+	mu   sync.Mutex
+	seen map[[32]byte]struct{}
+}
+
+func (v *verifiedValues) has(digest [32]byte) bool {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	_, ok := v.seen[digest]
+	return ok
+}
+
+func (v *verifiedValues) add(digest [32]byte) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.seen[digest] = struct{}{}
 }