概述

网上的前端验证码逻辑总感觉不安全，验证码建议还是使用后端配合验证。
如果产品确定可以上网的话，就可以使用腾讯，百度等第三方验证，对接方便。但是产品可能内网部署，就必须自己写了。
本文章就是基于这一点来实现的。
前端验证码显示一个图片，后端生成图片。

部分原理

1.前端调用生端获取图片时，传入一个roomID，后端生成一个4位验征码，放入redis中。然后生成一个图片返回。
2.前端显示图片，登录时将roomID和填写的验证码，一并提交，登录接口根据roomId从redis中取出验证码判断是否正确。

这样就相当于后端验证了。

大家觉得有问题什么，可以进行评论。谢谢。

源码

前端部分代码

<template>
  <div class="login-container">
    <vue-particles
      color="#ffffff"
      :particleOpacity="0.7"
      :particlesNumber="50"
      shapeType="circle"
      :particleSize="4"
      linesColor="#dedede"
      :linesWidth="1"
      :lineLinked="true"
      :lineOpacity="0.4"
      :linesDistance="150"
      :moveSpeed="2"
      :hoverEffect="true"
      hoverMode="grab"
      :clickEffect="true"
      clickMode="push"
    ></vue-particles>
    <el-form ref="loginForm" :model="loginForm" :rules="loginRules" class="login-form" autocomplete="on" label-position="left">
      <div class="title-container">
        <h3 class="title">智能综合管理系统</h3>
      </div>

      <el-form-item prop="username">
        <span class="svg-container">
          <svg-icon icon-class="user" />
        </span>
        <el-input ref="username" v-model="loginForm.username" placeholder="用户名" name="username" type="text" tabindex="1" autocomplete="on" />
      </el-form-item>

      <el-tooltip v-model="capsTooltip" content="Caps lock is On" placement="right" manual>
        <el-form-item prop="password">
          <span class="svg-container">
            <svg-icon icon-class="password" />
          </span>
          <el-input
            :key="passwordType"
            ref="password"
            v-model="loginForm.password"
            :type="passwordType"
            placeholder="密码"
            name="password"
            tabindex="2"
            autocomplete="on"
            @keyup.native="checkCapslock"
            @blur="capsTooltip = false"
            @keyup.enter.native="handleLogin"
          />
          <span class="show-pwd" @click="showPwd">
            <svg-icon :icon-class="passwordType === 'password' ? 'eye' : 'eye-open'" />
          </span>
        </el-form-item>
      </el-tooltip>
      <el-form-item prop="yzm">
        <span class="svg-container">
          <svg-icon icon-class="password" />
        </span>
        <el-input type="text" v-model="loginForm.verifyCode" maxlength="4" placeholder="验证码" />
        <div class="identifyCode" @click="refreshCode">
          <el-image :src="verifyImageUrl"></el-image>
        </div>
      </el-form-item>
      <el-button :loading="loading" type="primary" style="width: 100%; margin-bottom: 30px" @click.native.prevent="handleLogin">登录</el-button>
    </el-form>
  </div>
</template>

<script>
import { validUsername } from '@/utils/validate'
import Identify from './components/Identify'
import { uuid } from 'vue-uuid'; // uuid object is also exported to things
// outside Vue instance.


export default {
  name: 'Login',
  components: { Identify },
  data() {
    const validateUsername = (rule, value, callback) => {
      if (!validUsername(value)) {
        callback(new Error('请输入正确的用户名'))
      } else {
        callback()
      }
    }
    const validatePassword = (rule, value, callback) => {
      if (value.length < 6) {
        callback(new Error('密码最少6位'))
      } else {
        callback()
      }
    }
    return {
      loginForm: {
        username: 'admin',
        password: '111111',
        roomId: '',
        verifyCode: ''
      },
      loginRules: {
        username: [{ required: true, trigger: 'blur', validator: validateUsername }],
        password: [{ required: true, trigger: 'blur', validator: validatePassword }]
      },
      passwordType: 'password',
      capsTooltip: false,
      loading: false,
      showDialog: false,
      redirect: undefined,
      otherQuery: {},
      identifyCodes: '1234567890',
      identifyCode: '',
      // verifyImageRoomId: '',
      verifyImageUrl: '',
    }
  },
  watch: {
    $route: {
      handler: function (route) {
        const query = route.query
        if (query) {
          this.redirect = query.redirect
          this.otherQuery = this.getOtherQuery(query)
        }
      },
      immediate: true
    }
  },
  created() {
    // window.addEventListener('storage', this.afterQRScan)
    // this.identifyCode = ''
    // this.makeCode(this.identifyCodes, 4)
    this.refreshCode()
  },
  mounted() {
    if (this.loginForm.username === '') {
      this.$refs.username.focus()
    } else if (this.loginForm.password === '') {
      this.$refs.password.focus()
    }
  },
  destroyed() {
    // window.removeEventListener('storage', this.afterQRScan)
  },
  methods: {
    checkCapslock(e) {
      const { key } = e
      this.capsTooltip = key && key.length === 1 && (key >= 'A' && key <= 'Z')
    },
    showPwd() {
      if (this.passwordType === 'password') {
        this.passwordType = ''
      } else {
        this.passwordType = 'password'
      }
      this.$nextTick(() => {
        this.$refs.password.focus()
      })
    },
    createUuid() {
      let uuidV4 = uuid.v4().replace('-', '').replace('-', '').replace('-', '').replace('-', '')

      this.verifyImageRoomId = uuidV4
      this.verifyImageUrl = '/api/Operator/getCaptchaImage/120/40/' + this.verifyImageRoomId
      console.log(uuidV4)
    },
    handleLogin() {
      this.$refs.loginForm.validate(valid => {
        if (valid) {
          this.loading = true
          this.$store.dispatch('user/login', this.loginForm)
            .then(() => {
              this.$router.push({ path: this.redirect || '/', query: this.otherQuery })
              this.loading = false
            })
            .catch(() => {
              this.loading = false
            })
        } else {
          console.log('error submit!!')
          return false
        }
      })
    },
    getOtherQuery(query) {
      return Object.keys(query).reduce((acc, cur) => {
        if (cur !== 'redirect') {
          acc[cur] = query[cur]
        }
        return acc
      }, {})
    },
    // 生成随机数
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min)
    },
    // 切换验证码
    refreshCode() {
      let uuidV4 = uuid.v4().replace('-', '').replace('-', '').replace('-', '').replace('-', '')

      this.loginForm.roomId = uuidV4
      this.verifyImageUrl = '/api/Operator/getCaptchaImage/120/40/' + this.loginForm.roomId
      console.log(uuidV4)
    },
    // 生成四位随机验证码
    makeCode(o, l) {
      for (let i = 0; i < l; i++) {
        this.identifyCode += this.identifyCodes[
          this.randomNum(0, this.identifyCodes.length)
        ]
      }
      console.log(this.identifyCode)
    }
  }
}
</script>

<style lang="scss">
/* 修复input 背景不协调 和光标变色 */
/* Detail see https://github.com/PanJiaChen/vue-element-admin/pull/927 */

$bg: #283443;
$light_gray: #fff;
$cursor: #fff;

@supports (-webkit-mask: none) and (not (cater-color: $cursor)) {
  .login-container .el-input input {
    color: $cursor;
  }
}

/* reset element-ui css */
.login-container {
  background: url("~@/assets/background.jpg") no-repeat;
  min-height: 100vh;

  .el-input {
    display: inline-block;
    height: 47px;
    width: 85%;

    input {
      background: transparent;
      border: 0px;
      -webkit-appearance: none;
      border-radius: 0px;
      padding: 12px 5px 12px 15px;
      color: $light_gray;
      height: 47px;
      caret-color: $cursor;

      &:-webkit-autofill {
        box-shadow: 0 0 0px 1000px $bg inset !important;
        -webkit-text-fill-color: $cursor !important;
      }
    }
  }

  .el-form-item {
    border: 1px solid rgba(255, 255, 255, 0.1);
    background: rgba(0, 0, 0, 0.1);
    border-radius: 5px;
    color: #454545;

    .el-form-item__error {
      color: rgb(223, 223, 176);
    }
  }
}
</style>

<style lang="scss" scoped>
$bg: #2d3a4b;
$dark_gray: #889aa4;
$light_gray: #eee;

.login-container {
  min-height: 100%;
  width: 100%;
  background-color: $bg;
  overflow: hidden;

  .login-form {
    position: absolute;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
    margin: auto;
    width: 520px;
    max-width: 100%;
    padding: 160px 35px 0;
    margin: 0 auto;
    overflow: hidden;
  }

  .tips {
    font-size: 14px;
    color: #fff;
    margin-bottom: 10px;

    span {
      &:first-of-type {
        margin-right: 16px;
      }
    }
  }

  .svg-container {
    padding: 6px 5px 6px 15px;
    color: $dark_gray;
    vertical-align: middle;
    width: 30px;
    display: inline-block;
  }

  .title-container {
    position: relative;

    .title {
      font-size: 42px;
      color: $light_gray;
      margin: 0px auto 40px auto;
      text-align: center;
      font-weight: bold;
    }
  }

  .show-pwd {
    position: absolute;
    right: 10px;
    top: 7px;
    font-size: 16px;
    color: $dark_gray;
    cursor: pointer;
    user-select: none;
  }
  .identifyCode {
    position: absolute;
    right: 10px;
    top: 5px;
  }

  .thirdparty-button {
    position: absolute;
    right: 0;
    bottom: 6px;
  }

  @media only screen and (max-width: 470px) {
    .thirdparty-button {
      display: none;
    }
  }
}
</style>

后端接口

        /// <summary>
        /// 获取验证码
        /// </summary>
        /// <returns></returns>
        [HttpGet("getCaptchaImage/{width:int}/{height:int}/{roomId}")]
        public IActionResult GetCaptchaImage(int width, int height, string roomId)
        {
            Console.WriteLine(roomId);
            //int width = 100;
            //int height = 36;
            var captchaCode = Captcha.GenerateCaptchaCode();
            var result = Captcha.GenerateCaptchaImage(width, height, captchaCode);
            string redisKey = "VerifyCode_" + roomId;
            Startup.redisDb.StringSet(redisKey, captchaCode, new TimeSpan(0, 5, 0));
            Stream s = new MemoryStream(result.CaptchaByteData);
            return new FileStreamResult(s, "image/png");
        }

        /// <summary>
        /// 登录
        /// </summary>
        /// <returns></returns>
        [HttpPost("login")]
        public ApiResponseData Login(LoginDto loginInfo)
        {
            if (string.IsNullOrWhiteSpace(loginInfo.username))
                return ApiResponse.Error("用户名不能为空");
            if (string.IsNullOrWhiteSpace(loginInfo.password))
                return ApiResponse.Error("密码不能为空");

            Entity.BaseOperator operInfo = Db
                .Select<BaseOperator>()
                .Where(a => a.OperatorCode == loginInfo.username && a.Password == loginInfo.password.ToLower() && a.Status == 1 && a.IsDel == false).ToOne();
            if (operInfo == null)
                return ApiResponse.Error("用户名或者密码不正确");

            bool verifyResult = Captcha.ValidateCaptchaCode(loginInfo.RoomId, loginInfo.VerifyCode);
            if(verifyResult == false)
                return ApiResponse.Error("验证码不正确");

            //登录时重新生成token，一个用户只能在一个地方登录
            string token = System.Guid.NewGuid().ToString().Replace("-", "");
            Db.Update<BaseOperator>(operInfo.OperatorId)
                .Set(a => a.Token, token)
                .ExecuteAffrows();

            dynamic outJson = new ExpandoObject();//初始化一个不包含任何成员的ExpandoObject
            outJson.token = token;

            //存入redis
            string redisKey = "UserInfo_" + token;
            Startup.redisDb.StringSet(redisKey, operInfo.OperatorId, new TimeSpan(24, 0, 0));

            return ApiResponse.Succ(outJson);
        }