add agent environment

Author: paulwe

agent/environment.go

@@ -0,0 +1,24 @@
+package agent
+
+import "fmt"
+
+const MaxEnvironmentLength = 64
+
+func ValidateEnvironment(env string) error {
+	if env == "" {
+		return nil
+	}
+	if len(env) > MaxEnvironmentLength {
+		return fmt.Errorf("environment exceeds %d bytes", MaxEnvironmentLength)
+	}
+	for i := 0; i < len(env); i++ {
+		c := env[i]
+		switch {
+		case c == '_':
+			return fmt.Errorf("environment contains reserved character %q", c)
+		case c <= ' ' || c == 0x7f:
+			return fmt.Errorf("environment contains whitespace or control byte at position %d", i)
+		}
+	}
+	return nil
+}