[golang]查询ssl证书剩余有效天数并邮件提醒

前言

自从云厂商的免费ssl证书改成3个月，而且证书数量还是20个之后，自己网站的ssl证书就换成了其它免费方案。但是免费方案不会提醒证书过期，所以写个工具每天定时查询证书剩余有效天数，如果证书即将过期，就发送邮件提醒。

基本实现

最基本的代码功能就是检测网站ssl证书的有效天数，可以用命令行传参的方式指定网站域名。

package main

import (
	"crypto/tls"
	"flag"
	"fmt"
	"net"
	"os"
	"sync"
	"time"
)

var (
	port int
	wg   sync.WaitGroup
)

func checkssl(domain string, port int) {
	defer wg.Done()
	host := fmt.Sprintf("%s:%d", domain, port)
	conn, err := tls.DialWithDialer(&net.Dialer{
		Timeout:  time.Second * 5,
		Deadline: time.Now().Add(time.Second * 5),
	}, "tcp", host, &tls.Config{InsecureSkipVerify: true})
	if err != nil {
		fmt.Println(err)
		return
	}
	defer conn.Close()

	stats := conn.ConnectionState()
	certs := stats.PeerCertificates[0]
	localtz, _ := time.LoadLocation("Asia/Shanghai")
	issueTime := certs.NotBefore.In(localtz)
	expireTime := certs.NotAfter.In(localtz)

	today := time.Now().In(localtz)
	dayLeft := int(expireTime.Sub(today).Hours() / 24)
	fmt.Printf("%s, issue time: %v, expire time: %v, days left: %v\n", domain, issueTime, expireTime, dayLeft)
}

func main() {
	flag.IntVar(&port, "p", 443, "port, example: ./checkssl -p 1443 <domain name>")
	flag.Parse()
	positionArgs := flag.Args()
	if len(positionArgs) == 0 {
		fmt.Println("Error: Missing domain name")
		fmt.Println("Usage: ./checkssl <domain name>")
		os.Exit(1)
	}

	wg.Add(len(positionArgs))
	for _, arg := range positionArgs {
		go checkssl(arg, port)
	}
	wg.Wait()
}

使用示例

# 1. 编译
go build
# 2. 命令行传参的方式指定域名
./check-ssl baidu.com ithome.com qq.com

# 输出
baidu.com, issue time: 2024-01-30 08:00:00 +0800 CST, expire time: 2025-03-02 07:59:59 +0800 CST, days left: 187
ithome.com, issue time: 2024-01-22 08:00:00 +0800 CST, expire time: 2025-02-22 07:59:59 +0800 CST, days left: 179
qq.com, issue time: 2024-06-04 08:00:00 +0800 CST, expire time: 2025-06-11 07:59:59 +0800 CST, days left: 288

完善功能

需要完善的功能主要是发送邮件，这里使用SMTP协议来发送邮件。如果跟我一样用的是163邮箱，则需要先去获取一个SMTP的授权码。

因为需要配置SMTP的连接信息，所以改成了用文件来传入配置，也方便后期修改。配置文件config.yaml示例：

domains:
  - baidu.com
  - qq.com

email:
  smtp:
    host: "smtp.163.com"  # smtp服务器的地址
    port: 465  # 因为云服务器屏蔽了25端口, 只能使用tls加密的465端口
    from: ""   # 发送方邮箱
    token: ""  # 授权码
  sendto:
    - "qq@qq.com"  # 接收方的邮箱地址
  expire: 7  # 证书剩余有效天数, 小于7天时发送邮件提醒

读取配置的代码文件config.go，使用viper来读取配置文件。

package main

import "github.com/spf13/viper"

var (
	v *viper.Viper
)

type SMTPServer struct {
	Host  string
	Port  int
	Token string
	From  string
}

func initViper() {
	v = viper.New()
	v.AddConfigPath(".")
	v.SetConfigType("yaml")
	v.SetConfigFile(configfile)
	err := v.ReadInConfig()
	if err != nil {
		panic(err)
	}
}

type configer struct{}

func NewConfiger() configer {
	if v == nil {
		initViper()
	}
	return configer{}
}

func (c configer) GetSMTPServer() SMTPServer {
	return SMTPServer{
		Host:  v.GetString("email.smtp.host"),
		Port:  v.GetInt("email.smtp.port"),
		Token: v.GetString("email.smtp.token"),
		From:  v.GetString("email.smtp.from"),
	}
}

func (c configer) GetDomains() []string {
	return v.GetStringSlice("domains")
}

func (c configer) GetSendTos() []string {
	return v.GetStringSlice("email.sendto")
}

func (c configer) GetExpiry() int {
	return v.GetInt("email.expire")
}

发送邮件的相关代码文件：notify.go

package main

import (
	"crypto/tls"
	"fmt"
	"net/smtp"

	"github.com/jordan-wright/email"
)

type Postman struct {
	SmtpServer SMTPServer
	SendTos    []string
}

func (p Postman) SendEmail(domain string, dayleft int) {
	auth := smtp.PlainAuth("", p.SmtpServer.From, p.SmtpServer.Token, p.SmtpServer.Host)
	e := &email.Email{
		To:      p.SendTos,
		From:    fmt.Sprintf("YXHYW <%s>", p.SmtpServer.From),
		Subject: fmt.Sprintf("域名 %s SSL证书过期提醒", domain),
		Text:    []byte(fmt.Sprintf("域名 %s 的SSL证书即将过期, 剩余有效期 %d 天", domain, dayleft)),
	}
	// err := e.Send(fmt.Sprintf("%s:%d", p.SmtpServer.Host, p.SmtpServer.Port), auth)
	addr := fmt.Sprintf("%s:%d", p.SmtpServer.Host, p.SmtpServer.Port)
	fmt.Println("SMTP Server addr: ", addr)
	err := e.SendWithTLS(addr, auth, &tls.Config{
		InsecureSkipVerify: false,
		ServerName:         p.SmtpServer.Host,
	})
	if err != nil {
		fmt.Printf("Send email failed, %v\n", err)
	}
}

主体代码文件main.go，主要修改地方：检测到证书即将过期后，调用发送邮件的相关方法。

package main

import (
	"crypto/tls"
	"flag"
	"fmt"
	"net"
	"sync"
	"time"
)

var (
	port       int
	configfile string
	wg         sync.WaitGroup
	c          configer = NewConfiger()
)

func checkssl(domain string, port int) {
	defer wg.Done()
	host := fmt.Sprintf("%s:%d", domain, port)
	conn, err := tls.DialWithDialer(&net.Dialer{
		Timeout:  time.Second * 5,
		Deadline: time.Now().Add(time.Second * 5),
	}, "tcp", host, &tls.Config{InsecureSkipVerify: true})
	if err != nil {
		fmt.Println(err)
		return
	}
	defer conn.Close()

	stats := conn.ConnectionState()
	certs := stats.PeerCertificates[0]
	localtz, _ := time.LoadLocation("Asia/Shanghai")
	issueTime := certs.NotBefore.In(localtz)
	expireTime := certs.NotAfter.In(localtz)

	today := time.Now().In(localtz)
	dayLeft := int(expireTime.Sub(today).Hours() / 24)
	fmt.Printf("%s, issue time: %v, expire time: %v, days left: %v\n", domain, issueTime, expireTime, dayLeft)

	// c := NewConfiger()
	if dayLeft < c.GetExpiry() {
		p := Postman{SmtpServer: c.GetSMTPServer(), SendTos: c.GetSendTos()}
		p.SendEmail(domain, dayLeft)
	}
}

func main() {
	flag.IntVar(&port, "p", 443, "port, example: ./check-ssl -p 1443 <domain name>")
	flag.StringVar(&configfile, "c", "config.yaml", "config file")
	flag.Parse()

	conf := NewConfiger()
	domains := conf.GetDomains()

	wg.Add(len(domains))
	for _, arg := range domains {
		go checkssl(arg, port)
	}
	wg.Wait()
}

本地测试通过后，可以配到服务器的crontab中每天执行。