From 18b5c8ec6da64da90706643ffa52736a85a2ca59 Mon Sep 17 00:00:00 2001
From: Inverle <inverle@proton.me>
Date: Sun, 22 Jun 2025 00:09:18 +0200
Subject: Handle redirects when scraping feed from HTML (#7654)

* Handle redirects when scraping feed from HTML

* pass codesniffer

* pass PHPStan

* Optimize

* Another approach relying on HTML base
Standard way to save an HTML document with relative references

* Fix case of existing HTML base
which should not be overriden

---------

Co-authored-by: Alexandre Alapetite <alexandre@alapetite.fr>
---
 lib/lib_rss.php | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 5 deletions(-)

(limited to 'lib/lib_rss.php')

diff --git a/lib/lib_rss.php b/lib/lib_rss.php
index b8c6bc3cd..9d315a26d 100644
--- a/lib/lib_rss.php
+++ b/lib/lib_rss.php
@@ -507,12 +507,47 @@ function enforceHttpEncoding(string $html, string $contentType = ''): string {
 	return $html;
 }
 
+/**
+ * Set an HTML base URL to the HTML content if there is none.
+ * @param string $html the raw downloaded HTML content
+ * @param string $href the HTML base URL
+ * @return string an HTML string
+ */
+function enforceHtmlBase(string $html, string $href): string {
+	$doc = new DOMDocument();
+	$doc->loadHTML($html, LIBXML_NONET | LIBXML_NOERROR | LIBXML_NOWARNING);
+	if ($doc->documentElement === null) {
+		return '';
+	}
+	$xpath = new DOMXPath($doc);
+	$bases = $xpath->evaluate('//base');
+	if (!($bases instanceof DOMNodeList) || $bases->length === 0) {
+		$base = $doc->createElement('base');
+		if ($base === false) {
+			return $html;
+		}
+		$base->setAttribute('href', $href);
+		$head = null;
+		$heads = $xpath->evaluate('//head');
+		if ($heads instanceof DOMNodeList && $heads->length > 0) {
+			$head = $heads->item(0);
+		}
+		if ($head instanceof DOMElement) {
+			$head->insertBefore($base, $head->firstChild);
+		} else {
+			$doc->insertBefore($base, $doc->documentElement->firstChild);
+		}
+	}
+	return $doc->saveHTML() ?: $html;
+}
+
 /**
  * @param string $type {html,json,opml,xml}
  * @param array<string,mixed> $attributes
  * @param array<int,mixed> $curl_options
+ * @return array{body:string,effective_url:string,redirect_count:int,fail:bool}
  */
-function httpGet(string $url, string $cachePath, string $type = 'html', array $attributes = [], array $curl_options = []): string {
+function httpGet(string $url, string $cachePath, string $type = 'html', array $attributes = [], array $curl_options = []): array {
 	$limits = FreshRSS_Context::systemConf()->limits;
 	$feed_timeout = empty($attributes['timeout']) || !is_numeric($attributes['timeout']) ? 0 : intval($attributes['timeout']);
 
@@ -521,7 +556,7 @@ function httpGet(string $url, string $cachePath, string $type = 'html', array $a
 		$body = @file_get_contents($cachePath);
 		if ($body != false) {
 			syslog(LOG_DEBUG, 'FreshRSS uses cache for ' . \SimplePie\Misc::url_remove_credentials($url));
-			return $body;
+			return ['body' => $body, 'effective_url' => $url, 'redirect_count' => 0, 'fail' => false];
 		}
 	}
 
@@ -553,7 +588,7 @@ function httpGet(string $url, string $cachePath, string $type = 'html', array $a
 	// TODO: Implement HTTP 1.1 conditional GET If-Modified-Since
 	$ch = curl_init();
 	if ($ch === false) {
-		return '';
+		return ['body' => '', 'effective_url' => '', 'redirect_count' => 0, 'fail' => true];
 	}
 	curl_setopt_array($ch, [
 		CURLOPT_URL => $url,
@@ -598,10 +633,13 @@ function httpGet(string $url, string $cachePath, string $type = 'html', array $a
 	$body = curl_exec($ch);
 	$c_status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
 	$c_content_type = '' . curl_getinfo($ch, CURLINFO_CONTENT_TYPE);
+	$c_effective_url = curl_getinfo($ch, CURLINFO_EFFECTIVE_URL);
+	$c_redirect_count = curl_getinfo($ch, CURLINFO_REDIRECT_COUNT);
 	$c_error = curl_error($ch);
 	curl_close($ch);
 
-	if ($c_status != 200 || $c_error != '' || $body === false) {
+	$fail = $c_status != 200 || $c_error != '' || $body === false;
+	if ($fail) {
 		Minz_Log::warning('Error fetching content: HTTP code ' . $c_status . ': ' . $c_error . ' ' . $url);
 		$body = '';
 		// TODO: Implement HTTP 410 Gone
@@ -611,6 +649,7 @@ function httpGet(string $url, string $cachePath, string $type = 'html', array $a
 		$body = trim($body, " \n\r\t\v");	// Do not trim \x00 to avoid breaking a BOM
 		if ($type !== 'json') {
 			$body = enforceHttpEncoding($body, $c_content_type);
+			$body = enforceHtmlBase($body, $c_effective_url);
 		}
 	}
 
@@ -618,7 +657,7 @@ function httpGet(string $url, string $cachePath, string $type = 'html', array $a
 		Minz_Log::warning("Error saving cache $cachePath for $url");
 	}
 
-	return $body;
+	return ['body' => $body, 'effective_url' => $c_effective_url, 'redirect_count' => $c_redirect_count, 'fail' => $fail];
 }
 
 /**
-- 
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