96 lines
2.6 KiB
Text
96 lines
2.6 KiB
Text
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## SVR.JS API (_.tar.gz_ mods and server-side JavaScript)
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SVR.JS has its API for both _.tar.gz_ mods and server-side JavaScript that expands its functionality. SVR.JS API extends vanilla Node.JS HTTP API.
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### Error handling
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When a JavaScript error is thrown outside of event callbacks, SVR.JS will return a 500 error to the client. Inside event callbacks, SVR.JS will simply crash.
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#### Incorrect Error Handling:
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```js
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//XXX WARNING!!! IT WILL CRASH THE SVR.JS!!!
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//It also contains path traversal vulnerability!
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disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!
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var headers = getCustomHeaders();
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headers["Content-Type"] = "text/html; charset=utf8";
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if (href == "/page.svr") {
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fs.readFile(".template", function (err, data) {
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if (err) throw err; //EVIL!!!
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var id = uobject.query.id;
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if (!id) id = "index";
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if (fs.existsSync("pages/" + id + ".html")) {
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fs.readFile("pages/" + id + ".html", function (err2, data2) {
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if (err2) throw err2; //EVIL TWO!!!
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res.writeHead(200, "OK", headers);
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res.end(data.toString().replace("{websiteContents}", data2.toString()));
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});
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} else {
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callServerError(404);
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}
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});
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} else if (href == "/") {
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redirect("/page.svr");
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} else {
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elseCallback();
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}
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```
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Instead, you should handle errors gracefully using _callServerError_ function:
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#### Correct Error Handling:
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```js
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//Much better!
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disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!
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var headers = getCustomHeaders();
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headers["Content-Type"] = "text/html; charset=utf8";
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if (href == "/page.svr") {
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if (fs.existsSync(".template")) {
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fs.readFile(".template", function (err, data) {
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if (err) {
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callServerError(500, err);
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return;
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}
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var id = uobject.query.id;
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if (!id) id = "index";
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id = id
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.replace(/\\/g, "/")
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.replace(/(?:\/|^)\.\.(?=(\/|$))/g, "$1")
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.replace(/\/+/g, "/"); //Poor mans path sanitiation
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if (fs.existsSync("pages/" + id + ".html")) {
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fs.readFile("pages/" + id + ".html", function (err2, data2) {
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if (err2) {
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callServerError(500, err2);
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return;
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}
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res.writeHead(200, "OK", headers);
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res.end(
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data.toString().replace("{websiteContents}", data2.toString())
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);
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});
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} else {
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callServerError(404);
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}
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});
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} else {
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callServerError(
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500,
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new Error("Server is misconfigured - .template file missing")
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);
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}
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} else if (href == "/") {
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redirect("/page.svr");
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} else {
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elseCallback();
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}
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```
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By using `callServerError`, you can handle errors effectively and provide appropriate error responses to the client, preventing SVR.JS from crashing due to unhandled exceptions.
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