Merge branch 'main' into profile-ownership

client/cmd/service_params.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/netbirdio/netbird/client/configs"
 	"github.com/netbirdio/netbird/client/internal/daemonaddr"
+	"github.com/netbirdio/netbird/client/internal/elevate"
 	"github.com/netbirdio/netbird/util"
 )
 
@@ -50,10 +51,33 @@ func serviceParamsPath() string {
 
 // loadServiceParams reads saved service parameters from disk.
 // Returns nil with no error if the file does not exist.
+//
+// The file is read by an elevated install and decides the arguments and the
+// environment of the service it then registers, so it is used only when its
+// ownership and permissions are the ones saveServiceParams leaves behind. That
+// restricted ACL is applied when the file is written, which is not necessarily
+// before it is first read, so this is checked rather than assumed. A file that
+// fails the check is treated as absent, and the install proceeds with its
+// defaults.
 func loadServiceParams() (*serviceParams, error) {
 	path := serviceParamsPath()
 
-	data, err := os.ReadFile(path)
+	// Resolve links first so the checks apply to the file that is actually read.
+	// Since the check covers every directory above it as well, nobody who fails
+	// it can swap the file between here and the read below.
+	resolved, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil //nolint:nilnil
+		}
+		return nil, fmt.Errorf("resolve service params %s: %w", path, err)
+	}
+
+	if err := elevate.CheckOnlyOwnerWritable(resolved); err != nil {
+		return nil, fmt.Errorf("refusing to read service params from %s: %w", resolved, err)
+	}
+
+	data, err := os.ReadFile(resolved)
 	if err != nil {
 		if os.IsNotExist(err) {
 			return nil, nil //nolint:nilnil
@@ -199,10 +223,16 @@ func applyServiceParams(cmd *cobra.Command, params *serviceParams) {
 // If --service-env was explicitly set to empty, all saved env vars are cleared.
 // If --service-env was not set, saved env vars are used entirely.
 func applyServiceEnvParams(cmd *cobra.Command, params *serviceParams) {
+	// A forbidden name explicitly passed on the command line is an error the
+	// operator is told about, but one restored from a file written by an older
+	// version is dropped: an install that refuses to run would leave the host
+	// without a daemon over a variable nobody is asking for any more.
+	saved := dropForbiddenServiceEnvVars(cmd, params.ServiceEnvVars)
+
 	if !cmd.Flags().Changed("service-env") {
-		if len(params.ServiceEnvVars) > 0 {
+		if len(saved) > 0 {
 			// No explicit env vars: rebuild serviceEnvVars from saved params.
-			serviceEnvVars = envMapToSlice(params.ServiceEnvVars)
+			serviceEnvVars = envMapToSlice(saved)
 		}
 		return
 	}
@@ -221,13 +251,13 @@ func applyServiceEnvParams(cmd *cobra.Command, params *serviceParams) {
 		return
 	}
 
-	if len(params.ServiceEnvVars) == 0 {
+	if len(saved) == 0 {
 		return
 	}
 
 	// Merge saved values underneath explicit ones.
-	merged := make(map[string]string, len(params.ServiceEnvVars)+len(explicit))
-	maps.Copy(merged, params.ServiceEnvVars)
+	merged := make(map[string]string, len(saved)+len(explicit))
+	maps.Copy(merged, saved)
 	maps.Copy(merged, explicit) // explicit wins on conflict
 	serviceEnvVars = envMapToSlice(merged)
 }
@@ -250,6 +280,20 @@ var resetParamsCmd = &cobra.Command{
 	},
 }
 
+// dropForbiddenServiceEnvVars returns the saved entries that may still be
+// registered on the service, reporting every one it leaves behind.
+func dropForbiddenServiceEnvVars(cmd *cobra.Command, saved map[string]string) map[string]string {
+	kept := make(map[string]string, len(saved))
+	for key, value := range saved {
+		if isForbiddenServiceEnvVar(key) {
+			cmd.PrintErrf("Warning: ignoring saved service environment variable %s: it decides where the service resolves the executables, libraries or temporary files it uses\n", key)
+			continue
+		}
+		kept[key] = value
+	}
+	return kept
+}
+
 // envMapToSlice converts a map of env vars to a KEY=VALUE slice.
 func envMapToSlice(m map[string]string) []string {
 	s := make([]string, 0, len(m))