From 563ea09789613bcfc78ca0a16e89a85e81774cee Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Tue, 16 Feb 2021 18:40:29 +0000
Subject: [PATCH] Filesystem API: Make sure to only call `fread()` on non-empty
 files in the PclZip library.

This avoids a fatal error on PHP 8 caused by passing a zero value to `fread()` as the `$length` argument, which must be greater than zero.

Props yakimun, fierevere, jrf, DavidAnderson, SergeyBiryukov.
Fixes #52018.

git-svn-id: https://develop.svn.wordpress.org/trunk@50355 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-admin/includes/class-pclzip.php | 35 ++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/src/wp-admin/includes/class-pclzip.php b/src/wp-admin/includes/class-pclzip.php
index 8a085f8bd0..b8f2fdca86 100644
--- a/src/wp-admin/includes/class-pclzip.php
+++ b/src/wp-admin/includes/class-pclzip.php
@@ -3884,7 +3884,12 @@
 
 
             // ----- Read the compressed file in a buffer (one shot)
-            $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+            if ( $p_entry['compressed_size'] > 0 ) {
+              $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+            }
+            else {
+              $v_buffer = false;
+            }
 
             // ----- Decompress the file
             $v_file_content = @gzinflate($v_buffer);
@@ -4096,7 +4101,12 @@
         if ($p_entry['compressed_size'] == $p_entry['size']) {
 
           // ----- Read the file in a buffer (one shot)
-          $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ( $p_entry['compressed_size'] > 0 ) {
+            $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $v_buffer = false;
+          }
 
           // ----- Send the file to the output
           echo $v_buffer;
@@ -4105,7 +4115,12 @@
         else {
 
           // ----- Read the compressed file in a buffer (one shot)
-          $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ( $p_entry['compressed_size'] > 0 ) {
+            $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $v_buffer = false;
+          }
 
           // ----- Decompress the file
           $v_file_content = gzinflate($v_buffer);
@@ -4209,12 +4224,22 @@
         if ($p_entry['compression'] == 0) {
 
           // ----- Reading the file
-          $p_string = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ( $p_entry['compressed_size'] > 0 ) {
+            $p_string = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $p_string = false;
+          }
         }
         else {
 
           // ----- Reading the file
-          $v_data = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ( $p_entry['compressed_size'] > 0 ) {
+            $v_data = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $v_data = false;
+          }
 
           // ----- Decompress the file
           if (($p_string = @gzinflate($v_data)) === FALSE) {