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Fix incorrect handling of multi-byte codepoints split by chunk boundaries #15

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Fix incorrect handling of multi-byte codepoints split by chunk boundaries #15

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da41d7f
Test case for mangled multi-byte unicode codepoint
MrVoltz Oct 4, 2023
6eb6ebb
Fix incorrect handling of multi-byte codepoints split by chunk bounda…
MrVoltz Oct 4, 2023
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39 changes: 24 additions & 15 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -95,8 +95,17 @@ function RespModifier (opts) {
res.end = end;
}

var chunks = [];

res.push = function (chunk) {
res.data = (res.data || "") + chunk;
// Back-compat is somebody was calling push from outside with a string
if(!(chunk instanceof Buffer)) {
chunk = Buffer.from(chunk, "utf8");
}

// res.data can contain incorrectly decoded split multi-byte codepoints
res.data = (res.data || "") + chunk.toString("utf8");
chunks.push(chunk);
};

res.write = function (string, encoding) {
Expand All @@ -106,10 +115,11 @@ function RespModifier (opts) {
}

if (string !== undefined) {
var body = string instanceof Buffer ? string.toString(encoding) : string;
// Convert arguments into a Buffer
var chunk = !(string instanceof Buffer) ? Buffer.from(string, encoding) : string;
// If this chunk appears to be valid, push onto the res.data stack
if (force || (utils.isHtml(body) || utils.isHtml(res.data))) {
res.push(body);
if (force || (utils.isHtml(chunk.toString("utf8")) || utils.isHtml(res.data))) {
res.push(chunk);
} else {
restore();
return write.call(res, string, encoding);
Expand Down Expand Up @@ -142,19 +152,18 @@ function RespModifier (opts) {

res.end = function (string, encoding) {

res.data = res.data || "";

if (typeof string === "string") {
res.data += string;
if (!runPatches) {
return end.call(res, string, encoding);
}

if (string instanceof Buffer) {
res.data += string.toString();
if (typeof string === "string") {
res.push(Buffer.from(string, encoding));
} else if (string instanceof Buffer) {
res.push(string);
}

if (!runPatches) {
return end.call(res, string, encoding);
}
// Reconstruct res.data from buffers stored in chunks, so it is decoded as a valid Unicode string
res.data = Buffer.concat(chunks).toString("utf8");

// Check if our body is HTML, and if it does not already have the snippet.
if (force || utils.isHtml(res.data) && !utils.snip(res.data)) {
Expand All @@ -163,9 +172,9 @@ function RespModifier (opts) {
runPatches = false;
}
if (res.data !== undefined && !res._header) {
res.setHeader("content-length", Buffer.byteLength(res.data, encoding));
res.setHeader("content-length", Buffer.byteLength(res.data, "utf8"));
}
end.call(res, res.data, encoding);
end.call(res, res.data, "utf8");
};
}
}
Expand Down
45 changes: 45 additions & 0 deletions test/rules.unicode.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
var express = require("express");
var assert = require("chai").assert;
var request = require("supertest");
var respMod = require("..");

var inputString = "<body>příliš žluťoučký kůň</body>";

describe("Correctly decodes unicode characters split by chunk boundary", function () {

var app, lr;

before(function () {

app = express();

lr = respMod.create({
rules: [
{
match: "something",
replace: "something else"
}
]
});

app.use(lr.middleware);

app.get("/", function (req, res) {
var inputBuf = Buffer.from(inputString, "utf8");

res.write(inputBuf.slice(0, 8)); // split in the middle of ř
res.end(inputBuf.slice(8));
});
});

it("should correctly handle split unicode character", function (done) {

request(app)
.get("/")
.set("Accept", "text/html")
.end(function (err, res) {
assert.equal(res.text, inputString);
done();
});
});
});