baseline: P1 契约、agent 核心与中继投递（既有工作首次入库）

internal/config/config.go

@@ -0,0 +1,109 @@
+// Package config loads the agent's startup file.
+//
+// The shape is deliberately small and has no host field. The local SimAdmin is reached by port
+// number alone: a config entry naming a host would be the one thing standing between a mistyped
+// value and an agent that proxies commands to somebody else's machine.
+package config
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"regexp"
+)
+
+var nodePattern = regexp.MustCompile(`^nd_[A-Za-z0-9_-]{8,64}$`)
+var appPattern = regexp.MustCompile(`^ap_[A-Za-z0-9_-]{8,64}$`)
+
+// Device is a paired phone.
+type Device struct {
+	ID string `json:"id"`
+	// SignKey is the phone's Ed25519 public key, base64. The agent verifies every request against
+	// it and holds no corresponding secret, so a phone cannot be impersonated from the relay side.
+	SignKey string `json:"signKey"`
+	Name    string `json:"name,omitempty"`
+}
+
+// File is the on-disk shape.
+type File struct {
+	NodeID string `json:"nodeId"`
+	// RelayURL is https and is the only outbound destination.
+	RelayURL string `json:"relayUrl"`
+	// AgentToken is the relay bearer credential. It authorises nothing on its own; the challenge
+	// signature does the identifying.
+	AgentToken string `json:"agentToken"`
+	// LocalPort is the SimAdmin port on 127.0.0.1. There is deliberately no host field.
+	LocalPort int `json:"localPort"`
+	// SignKey is the agent's Ed25519 private key, base64.
+	SignKey string `json:"signKey"`
+	// KxKey is the agent's X25519 private key, base64.
+	KxKey string `json:"kxKey"`
+	// AuditPath is where the audit log is appended.
+	AuditPath string   `json:"auditPath"`
+	Devices   []Device `json:"devices"`
+}
+
+// Load reads and validates a config file.
+//
+// Validation is exhaustive rather than partial on purpose: an agent that starts with a missing
+// device or a bad port would sit there healthy and uncommandable, which is harder to notice than a
+// crash at boot.
+func Load(path string) (File, error) {
+	var cfg File
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return cfg, fmt.Errorf("config: %w", err)
+	}
+	decoder := json.NewDecoder(bytes.NewReader(raw))
+	if err := decoder.Decode(&cfg); err != nil {
+		return cfg, fmt.Errorf("config: decode %s: %w", path, err)
+	}
+	if err := cfg.Validate(); err != nil {
+		return cfg, fmt.Errorf("config: %s: %w", path, err)
+	}
+	return cfg, nil
+}
+
+// Validate checks every field the agent depends on.
+func (c File) Validate() error {
+	if !nodePattern.MatchString(c.NodeID) {
+		return errors.New("nodeId must look like nd_xxxxxxxx")
+	}
+	if c.RelayURL == "" {
+		return errors.New("relayUrl is required")
+	}
+	if c.AgentToken == "" {
+		return errors.New("agentToken is required")
+	}
+	if c.LocalPort <= 0 || c.LocalPort > 65535 {
+		return fmt.Errorf("localPort %d is out of range", c.LocalPort)
+	}
+	if c.SignKey == "" {
+		return errors.New("signKey is required")
+	}
+	if c.KxKey == "" {
+		return errors.New("kxKey is required")
+	}
+	if c.AuditPath == "" {
+		return errors.New("auditPath is required")
+	}
+	if len(c.Devices) == 0 {
+		return errors.New("devices is empty, so no phone could ever be authorised")
+	}
+	seen := map[string]bool{}
+	for _, device := range c.Devices {
+		if !appPattern.MatchString(device.ID) {
+			return fmt.Errorf("device id %q must look like ap_xxxxxxxx", device.ID)
+		}
+		if device.SignKey == "" {
+			return fmt.Errorf("device %q has no signKey", device.ID)
+		}
+		if seen[device.ID] {
+			return fmt.Errorf("device %q is listed twice", device.ID)
+		}
+		seen[device.ID] = true
+	}
+	return nil
+}