fix(core): handle Request -> Response regressions (#5991)

* fix(next): don't override `Content-Type` by `unstable_getServerSession`

* fix(core): handle `,` while setting `set-cookie`

Author: balazsorban44

Diff for: packages/next-auth/src/next/index.ts

@@ -1,5 +1,5 @@
 import { AuthHandler } from "../core"
-import { getURL, getBody } from "../utils/node"
+import { getURL, getBody, setHeaders } from "../utils/node"
 
 import type {
   GetServerSidePropsContext,
@@ -37,10 +37,7 @@ async function NextAuthHandler(
   const { status, headers } = response
   res.status(status)
 
-  for (const [key, val] of headers.entries()) {
-    const value = key === "set-cookie" ? val.split(",") : val
-    res.setHeader(key, value)
-  }
+  setHeaders(headers, res)
 
   // If the request expects a return URL, send it as JSON
   // instead of doing an actual redirect.
@@ -158,10 +155,11 @@ export async function unstable_getServerSession<
 
   const { status = 200, headers } = response
 
-  for (const [key, val] of headers.entries()) {
-    const value = key === "set-cookie" ? val.split(",") : val
-    res.setHeader(key, value)
-  }
+  setHeaders(headers, res)
+
+  // This would otherwise break rendering
+  // with `getServerSideProps` that needs to always return HTML
+  res.removeHeader?.("Content-Type")
 
   const data = await response.json()
 

Diff for: packages/next-auth/src/utils/node.ts

@@ -1,4 +1,4 @@
-import type { IncomingMessage } from "http"
+import type { IncomingMessage, ServerResponse } from "http"
 import type { GetServerSidePropsContext, NextApiRequest } from "next"
 
 export function setCookie(res, value: string) {
@@ -54,6 +54,93 @@ export function getURL(
   }
 }
 
+/**
+ * Set-Cookie header field-values are sometimes comma joined in one string. This splits them without choking on commas
+ * that are within a single set-cookie field-value, such as in the Expires portion.
+ * This is uncommon, but explicitly allowed - see https://tools.ietf.org/html/rfc2616#section-4.2
+ * Node.js does this for every header *except* set-cookie - see https://github.com/nodejs/node/blob/d5e363b77ebaf1caf67cd7528224b651c86815c1/lib/_http_incoming.js#L128
+ * Based on: https://github.com/google/j2objc/commit/16820fdbc8f76ca0c33472810ce0cb03d20efe25
+ * Credits to: https://github.com/tomball for original and https://github.com/chrusart for JavaScript implementation
+ * @source https://github.com/nfriedly/set-cookie-parser/blob/3eab8b7d5d12c8ed87832532861c1a35520cf5b3/lib/set-cookie.js#L144
+ */
+function getSetCookies(cookiesString: string) {
+  if (typeof cookiesString !== "string") {
+    return []
+  }
+
+  const cookiesStrings: string[] = []
+  let pos = 0
+  let start
+  let ch
+  let lastComma: number
+  let nextStart
+  let cookiesSeparatorFound
+
+  function skipWhitespace() {
+    while (pos < cookiesString.length && /\s/.test(cookiesString.charAt(pos))) {
+      pos += 1
+    }
+    return pos < cookiesString.length
+  }
+
+  function notSpecialChar() {
+    ch = cookiesString.charAt(pos)
+
+    return ch !== "=" && ch !== ";" && ch !== ","
+  }
+
+  while (pos < cookiesString.length) {
+    start = pos
+    cookiesSeparatorFound = false
+
+    while (skipWhitespace()) {
+      ch = cookiesString.charAt(pos)
+      if (ch === ",") {
+        // ',' is a cookie separator if we have later first '=', not ';' or ','
+        lastComma = pos
+        pos += 1
+
+        skipWhitespace()
+        nextStart = pos
+
+        while (pos < cookiesString.length && notSpecialChar()) {
+          pos += 1
+        }
+
+        // currently special character
+        if (pos < cookiesString.length && cookiesString.charAt(pos) === "=") {
+          // we found cookies separator
+          cookiesSeparatorFound = true
+          // pos is inside the next cookie, so back up and return it.
+          pos = nextStart
+          cookiesStrings.push(cookiesString.substring(start, lastComma))
+          start = pos
+        } else {
+          // in param ',' or param separator ';',
+          // we continue from that comma
+          pos = lastComma + 1
+        }
+      } else {
+        pos += 1
+      }
+    }
+
+    if (!cookiesSeparatorFound || pos >= cookiesString.length) {
+      cookiesStrings.push(cookiesString.substring(start, cookiesString.length))
+    }
+  }
+
+  return cookiesStrings
+}
+
+export function setHeaders(headers: Headers, res: ServerResponse) {
+  for (const [key, val] of headers.entries()) {
+    // See: https://github.com/whatwg/fetch/issues/973
+    const value = key === "set-cookie" ? getSetCookies(val) : val
+    res.setHeader(key, value)
+  }
+}
+
 declare global {
   // eslint-disable-next-line @typescript-eslint/no-namespace
   namespace NodeJS {