learn-platform-deploy/Backend/cmd/api/middleware.go

package main

import (
	"context"
	"net/http"
	"strings"
)

type authContextKey string

const userClaimsKey authContextKey = "userClaims"
const tenantContextKey authContextKey = "tenantContext"

type accessClaims struct {
	Sub               string   `json:"sub"`
	Email             string   `json:"email"`
	PreferredUsername string   `json:"preferred_username"`
	AuthorizedParty   string   `json:"azp"`
	TenantID          string   `json:"tenant_id"`
	TenantIDAlt       string   `json:"tenantId"`
	OrganizationID    string   `json:"organization_id"`
	OrganizationIDAlt string   `json:"organizationId"`
	OrganisationID    string   `json:"organisation_id"`
	OrganisationIDAlt string   `json:"organisationId"`
	OrgID             string   `json:"org_id"`
	OrgIDAlt          string   `json:"orgId"`
	Permissions       []string `json:"permissions"`
	Scope             string   `json:"scope"`
	Scopes            []string `json:"scopes"`
	RealmAccess       struct {
		Roles []string `json:"roles"`
	} `json:"realm_access"`
}

func hasOAuthScope(claims *accessClaims, required string) bool {
	if claims == nil {
		return false
	}
	for _, scope := range append(strings.Fields(claims.Scope), claims.Scopes...) {
		if scope == required {
			return true
		}
	}
	return false
}

type tenantContext struct {
	ID             string
	BypassScoping  bool
	RequestedByOps bool
}

func (a *app) authMiddleware(next http.Handler) http.Handler {
	if a.cfg.AuthDisabled {
		return next
	}

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if a.oidcVerifier == nil {
			writeError(w, http.StatusServiceUnavailable, "oidc verifier not configured")
			return
		}

		authHeader := r.Header.Get("Authorization")
		if authHeader == "" {
			writeError(w, http.StatusUnauthorized, "missing authorization header")
			return
		}

		tokenString := strings.TrimSpace(strings.TrimPrefix(authHeader, "Bearer "))
		if tokenString == "" {
			writeError(w, http.StatusUnauthorized, "invalid bearer token")
			return
		}

		idToken, err := a.oidcVerifier.Verify(r.Context(), tokenString)
		if err != nil {
			writeError(w, http.StatusUnauthorized, "invalid token")
			return
		}

		claims := &accessClaims{}
		if err := idToken.Claims(claims); err != nil {
			writeError(w, http.StatusUnauthorized, "invalid token claims")
			return
		}

		if expected := strings.TrimSpace(a.cfg.KeycloakAudience); expected != "" {
			if !contains(idToken.Audience, expected) && strings.TrimSpace(claims.AuthorizedParty) != expected {
				writeError(w, http.StatusUnauthorized, "token client is not authorized for this application")
				return
			}
		}

		tenantID := resolveClaimsTenantID(claims)
		isPlatformRole := hasAnyRole(claims, "platform_owner", "platform_admin")
		requestedTenantID := strings.TrimSpace(r.Header.Get("X-Tenant-Id"))
		if requestedTenantID != "" {
			if !isPlatformRole && tenantID != requestedTenantID {
				writeError(w, http.StatusForbidden, "tenant override requires platform role")
				return
			}
			tenantID = requestedTenantID
		}

		ctx := context.WithValue(r.Context(), userClaimsKey, claims)
		ctx = context.WithValue(ctx, tenantContextKey, tenantContext{
			ID:             tenantID,
			BypassScoping:  isPlatformRole,
			RequestedByOps: requestedTenantID != "",
		})
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func withCORS(allowedOrigins []string, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		origin := r.Header.Get("Origin")
		if isAllowedOrigin(origin, allowedOrigins) {
			w.Header().Set("Access-Control-Allow-Origin", origin)
		} else if contains(allowedOrigins, "*") {
			w.Header().Set("Access-Control-Allow-Origin", "*")
		}

		w.Header().Set("Access-Control-Allow-Methods", "GET,POST,PUT,PATCH,DELETE,OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")

		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}

		next.ServeHTTP(w, r)
	})
}

func isAllowedOrigin(origin string, allowed []string) bool {
	if origin == "" {
		return false
	}
	for _, entry := range allowed {
		if entry == "*" || entry == origin {
			return true
		}
	}
	return false
}

func contains(values []string, needle string) bool {
	for _, value := range values {
		if value == needle {
			return true
		}
	}
	return false
}

func hasRole(claims *accessClaims, role string) bool {
	for _, candidate := range claims.RealmAccess.Roles {
		if candidate == role {
			return true
		}
	}
	return false
}

func resolveClaimsTenantID(claims *accessClaims) string {
	if claims == nil {
		return ""
	}
	for _, candidate := range []string{
		claims.TenantID,
		claims.TenantIDAlt,
		claims.OrganizationID,
		claims.OrganizationIDAlt,
		claims.OrganisationID,
		claims.OrganisationIDAlt,
		claims.OrgID,
		claims.OrgIDAlt,
	} {
		if trimmed := strings.TrimSpace(candidate); trimmed != "" {
			return trimmed
		}
	}
	return ""
}

func resolveClaimsUserID(claims *accessClaims) string {
	if claims == nil {
		return ""
	}
	for _, candidate := range []string{claims.Sub, claims.PreferredUsername, claims.Email} {
		if trimmed := strings.TrimSpace(candidate); trimmed != "" {
			return trimmed
		}
	}
	return ""
}