From 080105c6d379f7dac6f191f1996c00e7dcc1ddce Mon Sep 17 00:00:00 2001
From: Frode Petterson <frode.andre.petterson@gmail.com>
Date: Sun, 16 Jan 2022 23:28:25 +0100
Subject: [PATCH] MDL-73588 curl: Fix expected CURLOPT_FILE behavior

After cbf9dfb the CURLOPT_FILE no longer behaves as expected. All
redirect responses are appended to the same stream resource.  This fix
reverts back to the old behavior by setting the stream pointer back to
the beginning for each subsequent redirect.
---
 lib/filelib.php            | 10 ++++++++++
 lib/tests/filelib_test.php | 31 +++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/lib/filelib.php b/lib/filelib.php
index cd1cf4d3471..a5294a9d81e 100644
--- a/lib/filelib.php
+++ b/lib/filelib.php
@@ -3828,6 +3828,16 @@ class curl {
                     return $urlisblocked;
                 }
 
+                // If the response body is written to a seekable stream resource, reset the stream pointer to avoid
+                // appending multiple response bodies to the same resource.
+                if (!empty($this->options['CURLOPT_FILE'])) {
+                    $streammetadata = stream_get_meta_data($this->options['CURLOPT_FILE']);
+                    if ($streammetadata['seekable']) {
+                        ftruncate($this->options['CURLOPT_FILE'], 0);
+                        rewind($this->options['CURLOPT_FILE']);
+                    }
+                }
+
                 curl_setopt($curl, CURLOPT_URL, $redirecturl);
                 $ret = curl_exec($curl);
 
diff --git a/lib/tests/filelib_test.php b/lib/tests/filelib_test.php
index e796d786cef..b66a2481273 100644
--- a/lib/tests/filelib_test.php
+++ b/lib/tests/filelib_test.php
@@ -145,6 +145,9 @@ class core_filelib_testcase extends advanced_testcase {
         $contents = download_file_content("$testurl?redir=2");
         $this->assertSame('done', $contents);
 
+        $contents = download_file_content("$testurl?redir=2&verbose=1");
+        $this->assertSame('done', $contents);
+
         $response = download_file_content("$testurl?redir=2", null, null, true);
         $this->assertInstanceOf('stdClass', $response);
         $this->assertSame('200', $response->status);
@@ -153,6 +156,14 @@ class core_filelib_testcase extends advanced_testcase {
         $this->assertSame('done', $response->results);
         $this->assertSame('', $response->error);
 
+        $response = download_file_content("$testurl?redir=2&verbose=1", null, null, true);
+        $this->assertInstanceOf('stdClass', $response);
+        $this->assertSame('200', $response->status);
+        $this->assertTrue(is_array($response->headers));
+        $this->assertMatchesRegularExpression('|^HTTP/1\.[01] 200 OK$|', rtrim($response->response_code));
+        $this->assertSame('done', $response->results);
+        $this->assertSame('', $response->error);
+
         // Commented out this block if there are performance problems.
         /*
         $contents = download_file_content("$testurl?redir=6");
@@ -327,6 +338,17 @@ class core_filelib_testcase extends advanced_testcase {
         $this->assertSame('done', file_get_contents($tofile));
         @unlink($tofile);
 
+        $curl = new curl();
+        $tofile = "$CFG->tempdir/test.html";
+        @unlink($tofile);
+        $fp = fopen($tofile, 'w');
+        $result = $curl->get("$testurl?redir=1&verbose=1", array(), array('CURLOPT_FILE' => $fp));
+        $this->assertTrue($result);
+        fclose($fp);
+        $this->assertFileExists($tofile);
+        $this->assertSame('done', file_get_contents($tofile));
+        @unlink($tofile);
+
         $curl = new curl();
         $tofile = "$CFG->tempdir/test.html";
         @unlink($tofile);
@@ -335,6 +357,15 @@ class core_filelib_testcase extends advanced_testcase {
         $this->assertFileExists($tofile);
         $this->assertSame('done', file_get_contents($tofile));
         @unlink($tofile);
+
+        $curl = new curl();
+        $tofile = "$CFG->tempdir/test.html";
+        @unlink($tofile);
+        $result = $curl->download_one("$testurl?redir=1&verbose=1", array(), array('filepath' => $tofile));
+        $this->assertTrue($result);
+        $this->assertFileExists($tofile);
+        $this->assertSame('done', file_get_contents($tofile));
+        @unlink($tofile);
     }
 
     /**