http: GET /auth/oidc/callback — JIT-provision, refresh, deny paths

internal/server/http/oidc_handlers.go

@@ -3,11 +3,18 @@
 package http
 
 import (
+	"encoding/json"
+	"errors"
 	"log/slog"
 	stdhttp "net/http"
+	"strings"
 	"time"
 
+	"github.com/oklog/ulid/v2"
+
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/auth"
 	"gitea.dcglab.co.uk/steve/restic-manager/internal/server/oidc"
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
 )
 
 // handleOIDCLogin generates state + PKCE pair, persists them, and
@@ -33,3 +40,166 @@ func (s *Server) handleOIDCLogin(w stdhttp.ResponseWriter, r *stdhttp.Request) {
 	}
 	stdhttp.Redirect(w, r, s.deps.OIDC.AuthURL(state, challenge), stdhttp.StatusSeeOther)
 }
+
+func (s *Server) handleOIDCCallback(w stdhttp.ResponseWriter, r *stdhttp.Request) {
+	q := r.URL.Query()
+	code := q.Get("code")
+	state := q.Get("state")
+	if code == "" || state == "" {
+		s.oidcRedirectError(w, r, "missing_params")
+		return
+	}
+	verifier, err := s.deps.Store.ConsumeOIDCState(r.Context(), oidc.HashState(state))
+	if err != nil {
+		s.oidcRedirectError(w, r, "bad_state")
+		return
+	}
+	claims, rawIDToken, err := s.deps.OIDC.Exchange(r.Context(), code, verifier)
+	if err != nil {
+		slog.Warn("oidc callback: exchange", "err", err)
+		s.oidcRedirectError(w, r, "exchange_failed")
+		return
+	}
+
+	uname := strings.ToLower(strings.TrimSpace(claims.PreferredUsername))
+	if uname == "" {
+		uname = strings.ToLower(strings.TrimSpace(claims.Email))
+	}
+	if uname == "" || claims.Subject == "" {
+		s.oidcRedirectError(w, r, "missing_claims")
+		return
+	}
+
+	role := s.deps.OIDC.MapRole(claims.Roles)
+	if role == "" {
+		_ = s.auditOIDCBlocked(r, claims, "no_role_match")
+		s.oidcRedirectError(w, r, "no_role_match")
+		return
+	}
+
+	now := time.Now().UTC()
+
+	// Returning OIDC user — refresh role + email + last_login.
+	existing, err := s.deps.Store.GetUserByOIDCSubject(r.Context(), claims.Subject)
+	if err == nil {
+		if existing.DisabledAt != nil {
+			s.oidcRedirectError(w, r, "user_disabled")
+			return
+		}
+		_ = s.deps.Store.SetUserRole(r.Context(), existing.ID, store.Role(role))
+		_ = s.deps.Store.SetUserEmail(r.Context(), existing.ID, claims.Email)
+		_ = s.deps.Store.MarkUserLogin(r.Context(), existing.ID, now)
+		_ = s.deps.Store.AppendAudit(r.Context(), store.AuditEntry{
+			ID: ulid.Make().String(), UserID: &existing.ID, Actor: "user",
+			Action: "user.oidc_login", TargetKind: ptr("user"),
+			TargetID: &existing.ID, TS: now,
+		})
+		s.oidcDropSessionAndRedirect(w, r, existing.ID, rawIDToken, now)
+		return
+	} else if !errors.Is(err, store.ErrNotFound) {
+		slog.Error("oidc callback: lookup by sub", "err", err)
+		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
+		return
+	}
+
+	// New OIDC user — first check the username doesn't collide with
+	// a local user.
+	if _, err := s.deps.Store.GetUserByUsername(r.Context(), uname); err == nil {
+		_ = s.auditOIDCBlocked(r, claims, "username_taken")
+		s.oidcRedirectError(w, r, "username_taken")
+		return
+	} else if !errors.Is(err, store.ErrNotFound) {
+		slog.Error("oidc callback: lookup by username", "err", err)
+		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
+		return
+	}
+
+	// JIT-provision.
+	id := ulid.Make().String()
+	var emailPtr *string
+	if claims.Email != "" {
+		em := strings.ToLower(claims.Email)
+		emailPtr = &em
+	}
+	sub := claims.Subject
+	if err := s.deps.Store.CreateUser(r.Context(), store.User{
+		ID: id, Username: uname, PasswordHash: "",
+		Role: store.Role(role), Email: emailPtr,
+		AuthSource: "oidc", OIDCSubject: &sub,
+		CreatedAt: now,
+	}); err != nil {
+		slog.Error("oidc callback: provision", "err", err)
+		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
+		return
+	}
+	_ = s.deps.Store.MarkUserLogin(r.Context(), id, now)
+	_ = s.deps.Store.AppendAudit(r.Context(), store.AuditEntry{
+		ID: ulid.Make().String(), UserID: &id, Actor: "user",
+		Action: "user.created", TargetKind: ptr("user"), TargetID: &id,
+		TS:      now,
+		Payload: jsonMust(map[string]any{"auth_source": "oidc"}),
+	})
+	_ = s.deps.Store.AppendAudit(r.Context(), store.AuditEntry{
+		ID: ulid.Make().String(), UserID: &id, Actor: "user",
+		Action: "user.oidc_login", TargetKind: ptr("user"), TargetID: &id,
+		TS: now,
+	})
+	s.oidcDropSessionAndRedirect(w, r, id, rawIDToken, now)
+}
+
+func (s *Server) oidcDropSessionAndRedirect(w stdhttp.ResponseWriter, r *stdhttp.Request, userID, idToken string, now time.Time) {
+	rawSession, err := auth.NewToken()
+	if err != nil {
+		slog.Error("oidc: session token", "err", err)
+		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
+		return
+	}
+	hashed := auth.HashToken(rawSession)
+	if err := s.deps.Store.CreateSession(r.Context(), store.Session{
+		ID: hashed, UserID: userID, CreatedAt: now,
+		ExpiresAt: now.Add(8 * time.Hour),
+		IDToken:   idToken,
+	}, hashed); err != nil {
+		slog.Error("oidc: create session", "err", err)
+		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
+		return
+	}
+	stdhttp.SetCookie(w, &stdhttp.Cookie{
+		Name: sessionCookieName, Value: rawSession,
+		Path: "/", HttpOnly: true,
+		SameSite: stdhttp.SameSiteLaxMode,
+		Secure:   s.deps.Cfg.CookieSecure,
+		Expires:  now.Add(8 * time.Hour),
+	})
+	stdhttp.Redirect(w, r, "/", stdhttp.StatusSeeOther)
+}
+
+func (s *Server) oidcRedirectError(w stdhttp.ResponseWriter, r *stdhttp.Request, code string) {
+	stdhttp.Redirect(w, r, "/login?oidc_error="+code, stdhttp.StatusSeeOther)
+}
+
+// auditOIDCBlocked records a failed sign-in. user_id is nil because
+// no row was created; the IdP subject + reason go in the payload so
+// admin can correlate.
+func (s *Server) auditOIDCBlocked(r *stdhttp.Request, claims *oidc.Claims, reason string) error {
+	return s.deps.Store.AppendAudit(r.Context(), store.AuditEntry{
+		ID: ulid.Make().String(), UserID: nil, Actor: "system",
+		Action: "user.oidc_login_blocked", TargetKind: ptr("user"),
+		TargetID: nil, TS: time.Now().UTC(),
+		Payload: jsonMust(map[string]any{
+			"sub":      claims.Subject,
+			"username": claims.PreferredUsername,
+			"reason":   reason,
+		}),
+	})
+}
+
+// jsonMust marshals to json.RawMessage; on error returns nil so the
+// audit row still lands without the payload (best-effort).
+func jsonMust(v any) json.RawMessage {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return nil
+	}
+	return json.RawMessage(b)
+}