コロナウイルス対応のため、学習コンテンツの無料開放にひと肌脱いだ話。

const https = require('https');

const AWS_ACCESSKEY_ID =  process.env.AWS_ACCESSKEY_ID;
const AWS_SECRET_ACCESSKEY =  process.env.AWS_SECRET_ACCESSKEY;
const PDF_BASE_URL = process.env.PDF_BASE_URL;
const PDF_BUCKET = process.env.PDF_BUCKET;
const PDF_EXPIRES = parseInt(process.env.PDF_EXPIRES,10);

let AWS = require('aws-sdk');
AWS.config.update({accessKeyId: AWS_ACCESSKEY_ID, secretAccessKey: AWS_SECRET_ACCESSKEY,region:"ap-northeast-1"});
let s3 = new AWS.S3({signatureVersion:'v4'});


exports.handler = async function (event, context, callback) {

    const done = (err, res) => callback(null, {
        statusCode: err ? '400' : '302',
        body: res,
        headers: {
            "Access-Control-Allow-Origin": "*",　//Lambdaプロキシ統合の場合は自前でCORS設定。
            "Location": res //302リダイレクトのために独自設定
        }
    });

    switch (event.httpMethod) {
        case 'GET':

            const book = event['queryStringParameters']['book'];
            const page = event['queryStringParameters']['page'];

            let presignedURL = await createPresignedURL(PDF_BUCKET,book+"/"+page+".pdf");
            let return_url = PDF_BASE_URL+"?file="+encodeURIComponent(presignedURL);
            console.log('createPresignedURL :' + return_url);  

            done(null,return_url);

            break;
        default:
            done(new Error(`Unsupported method "${event.httpMethod}"`));
    }

};


/**
 * 対象のURLに対して署名を行い、公開用のURLを発行します。
 */
async function createPresignedURL(inBucket,pdffilename){

    const s3params = {
        Bucket: inBucket,
        Key: pdffilename,
        Expires: PDF_EXPIRES
    };
    console.log('createPresignedURL:', JSON.stringify(s3params));

    try {
        let signed_url = await s3.getSignedUrl('getObject', s3params);
        return signed_url;
    } catch (err) {
        console.log("Err:"+err);
        return err;
    }

}

{
    "Version": "2012-10-17",
    "Id": "policy example",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": "*",
            "Action": "execute-api:Invoke",
            "Resource": "arn:aws:execute-api:Hogehoge/*",
            "Condition": {
                "StringLike": {
                    "aws:Referer": [
                        "https://foobar/*"
                    ]
                }
            }
        }
    ]
}

 /* ツールバーのボタン類を削除 */
#sidebarToggle,
#openFile, 
#viewBookmark,
#print,
#download,
#secondaryOpenFile, 
#secondaryViewBookmark,
#secondaryDownload,
#secondaryPrint,
#secondaryToolbarToggle { 
    display: none !important;
}

 /* ブラウザ印刷時のデータ削除 */
@media print{
  body{
    display: none;
  }
}

function getDefaultPreferences() {
  if (!defaultPreferences) {
    defaultPreferences = Promise.resolve({
      "cursorToolOnLoad": 0,
      "defaultZoomValue": "",
      "disablePageLabels": false,
      "enablePrintAutoRotate": false,
      "enableWebGL": false,
      "eventBusDispatchToDOM": false,
      "externalLinkTarget": 0,
      "historyUpdateUrl": false,
      "pdfBugEnabled": false,
      "renderer": "canvas",
      "renderInteractiveForms": false,
      "sidebarViewOnLoad": -1,
      "scrollModeOnLoad": 1, //ここのデフォルトを-1⇒１に変更
      "spreadModeOnLoad": -1,
      "textLayerMode": 1,
      "useOnlyCssZoom": false,
      "viewOnLoad": 0,
      "disableAutoFetch": false,
      "disableFontFace": false,
      "disableRange": false,
      "disableStream": false
    });
  }

{
    "Version": "2012-10-17",
    "Id": "policyexample",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": "*",
            "Action": "s3:GetObject",
            "Resource": "arn:aws:s3:::hogehoge/*",
            "Condition": {
                "StringLike": {
                    "aws:Referer": [
                        "https://foo.bar/*"
                    ]
                }
            }
        }
    ]
}

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
<CORSRule>
    <AllowedOrigin>https://hogehohogehoge</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <AllowedMethod>POST</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <ExposeHeader>ETag</ExposeHeader>
    <ExposeHeader>Accept-Ranges</ExposeHeader>
    <ExposeHeader>Content-Encoding</ExposeHeader>
    <ExposeHeader>Content-Length</ExposeHeader>
    <ExposeHeader>Content-Range</ExposeHeader>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>
</CORSConfiguration>