From 6854cb3f4d8219cf1829e32122eb2502a916eae9 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Sat, 1 Feb 2020 09:05:48 +0100
Subject: initial checkin

---
 includes/class.csp.php | 106 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 includes/class.csp.php

(limited to 'includes/class.csp.php')

diff --git a/includes/class.csp.php b/includes/class.csp.php
new file mode 100644
index 0000000..ecf4541
--- /dev/null
+++ b/includes/class.csp.php
@@ -0,0 +1,106 @@
+<?php
+/**
+ *
+ * A simple class for dynamic construction of Content-Security-Policy HTTP header string.
+ *
+ * This is just quick write to get the job for Flyspray done. May change completely!
+ *
+ * It does not check if the added rules are valid or make sense in the context and http request/response!
+ * So it is currently up to the code sections who use that class that the resulting csp string is correct.
+ *
+ * @license http://opensource.org/licenses/lgpl-license.php Lesser GNU Public License
+ * @author peterdd
+ *
+ * @see https://www.w3.org/TR/CSP2/
+ * @see https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP
+ * @see https://caniuse.com/#search=csp
+ *
+ * Example: $csp=new ContentSecurityPolicy(); $csp->add('default-src', "'none'"); $csp->add('style-src', "'self'"); $csp->emit();
+ */
+class ContentSecurityPolicy {
+
+	#private $csp=array();
+	public $csp=array();
+
+	# for debugging just to track which extension/plugins wants to add csp-entries
+	#public $history=array();
+
+	function __construct(){
+		$this->csp=array();
+	}
+
+	/**
+	* get the constructed concatenated value string part for the http Content-Security-Header
+	*
+	* TODO: maybe some syntax checks and logical verification when building the string.
+	*
+	* MAYBE: add optional parameter to get only a part like $csp->get('img-src')
+	* Alternatively the user can just access the currently public $csp->csp['img-src'] to get that values as array.
+	*
+	*/
+	public function get(){
+		$out = '';
+		foreach ( $this->csp as $key => $values ) {
+			$out .= $key.' '.implode(' ', $values).'; ';
+		}
+		$out = trim($out, '; ');
+		return $out;
+	}
+	
+	/**
+	 * adds a value to a csp type
+	 *
+	 * @param type
+	 * @param value single values for a type
+	 *
+	 * examples:
+	 * $csp->add('default-src', "'self'"); # surrounding double quotes "" used to pass the single quotes
+	 * $csp->add('img-src', 'mycdn.example.com'); # single quoted string ok
+	*/
+	public function add($type, $value){
+		if( isset($this->csp[$type]) ) {
+			if( !in_array( $value, $this->csp[$type] ) ) {
+				$this->csp[$type][] = $value;
+			}
+		} else {
+			$this->csp[$type] = array($value);
+		}
+		#$this->history[]=debug_backtrace()[1];
+	}
+
+	/**
+	* sends the Content-Security-Policy http headers
+	*/
+	public function emit() {
+		$string=$this->get();
+		header('Content-Security-Policy: '.$string );
+		# some older web browsers used vendor prefixes before csp got w3c recommendation.
+		# maybe use useragent string to detect who should receive this outdated vendor csp strings.
+		# for IE 10-11
+		header('X-Content-Security-Policy: '.$string );
+		# for Chrome 15-24, Safari 5.1-6, ..
+		header('X-WebKit-CSP: '.$string );
+	}
+
+	/**
+	* Put the csp as meta-tags in the HTML-head section.
+	*
+	* Q: What is the benefit of adding csp as meta tags too?
+	*
+	* I don't know, maybe this way the csp persist if someone saves a page to his harddrive for instance or if bad web proxies rip off csp http headers?
+	* Do webbrowsers store the CSP-HTTP header to the HTML-head as metatags automatically if there is no related metatag in the original page? Mhh..
+	*/
+	public function getMeta() {
+		$string=$this->get();
+		$out= '<meta http-equiv="Content-Security-Policy" content="'.$string.'">';
+		# enable if you think it is necessary for your customers.
+		# older web browsers used vendor prefixes before csp2 got a w3c recommendation standard..
+		# maybe use useragent string to detect who should receive this outdated vendor csp strings.
+		# for IE 10-11
+		$out.= '<meta http-equiv="X-Content-Security-Policy" content="'.$string.'">';
+		# for Chrome 15-24, Safari 5.1-6, ..
+		$out.= '<meta http-equiv="X-WebKit-CSP" content="'.$string.'">';
+		return $out;
+	}
+
+}
-- 
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