From 6d06f34e2dcbdc4a5cb8e4652a3b1aacefb4e266 Mon Sep 17 00:00:00 2001
From: Daniel Winzen <daniel@danwin1210.de>
Date: Fri, 5 Sep 2025 10:43:01 +0200
Subject: [PATCH] Change simple and moderate captchas so that characters are no
 longer in fixed positions. Also avoid using fixed colours. In the moderate
 captcha, use filled, blurred rectangles instead of dots and lines to obscure
 the solution. In setup page, remove deprecation from both captchas.

---
 chat.php | 51 +++++++++++++++++++++++++++------------------------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/chat.php b/chat.php
index 88495d7..ec8c93f 100644
--- a/chat.php
+++ b/chat.php
@@ -677,29 +677,34 @@ function send_captcha(): void
 	} else {
 		echo _('Type the characters in the image:');
 	}
-	if($difficulty===1){
-		$im=imagecreatetruecolor(55, 24);
-		$bg=imagecolorallocate($im, 0, 0, 0);
-		$fg=imagecolorallocate($im, 255, 255, 255);
+	if($difficulty===1 || $difficulty===2){
+		$fontwidth = imagefontwidth(5);
+		$fontheight = imagefontheight(5);
+		$CAPTCHAWIDTH = $fontwidth * 5 * 3;
+		$CAPTCHAHEIGHT = $fontheight * 3;
+		$im=imagecreatetruecolor($CAPTCHAWIDTH, $CAPTCHAHEIGHT);
+		$bg=imagecolorallocate($im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));
 		imagefill($im, 0, 0, $bg);
-		imagestring($im, 5, 5, 5, $code, $fg);
-		echo '<img alt="" width="55" height="24" src="data:image/png;base64,';
-	}elseif($difficulty===2){
-		$im=imagecreatetruecolor(55, 24);
-		$bg=imagecolorallocate($im, 0, 0, 0);
-		$fg=imagecolorallocate($im, 255, 255, 255);
-		imagefill($im, 0, 0, $bg);
-		imagestring($im, 5, 5, 5, $code, $fg);
-		$line=imagecolorallocate($im, 255, 255, 255);
-		for($i=0;$i<2;++$i){
-			imageline($im, 0, mt_rand(0, 24), 55, mt_rand(0, 24), $line);
+		$margins = 0;
+		if($difficulty===2){
+			for($i=0; $i<5; $i++){
+				for($j=0; $j<2; $j++){
+					imagefilledrectangle($im, mt_rand($i * $CAPTCHAWIDTH / 5, ($i + 1) * $CAPTCHAWIDTH / 5), mt_rand(0, $CAPTCHAHEIGHT), mt_rand(($i + 0.5) * $CAPTCHAWIDTH / 5, ($i + 1.5) * $CAPTCHAWIDTH / 5), mt_rand(0, $CAPTCHAHEIGHT), imagecolorallocate($im, mt_rand(128, 255), mt_rand(128, 255), mt_rand(128, 255)));
+				}
+			}
 		}
-		$dots=imagecolorallocate($im, 255, 255, 255);
-		for($i=0;$i<100;++$i){
-			imagesetpixel($im, mt_rand(0, 55), mt_rand(0, 24), $dots);
+		imagefilter($im, IMG_FILTER_SMOOTH, 5);
+		$xoffset=0;
+		for($i=0; $i<5; $i++){
+			$xoffset+= mt_rand(0, ($CAPTCHAWIDTH - (5 * $fontwidth)) - $xoffset); // randomly shift characters to the right
+			imagechar($im, 5, $xoffset + $i * $fontwidth, mt_rand(0, $CAPTCHAHEIGHT - $fontheight), $code[$i], imagecolorallocate($im, mt_rand(224, 255), mt_rand(224, 255), mt_rand(224, 255)));
+			if($difficulty===2){
+				imagelayereffect($im,IMG_EFFECT_OVERLAY);
+			}
 		}
-		echo '<img alt="" width="55" height="24" src="data:image/png;base64,';
 	}elseif($difficulty===3){ // hard
+		$CAPTCHAWIDTH=120;
+		$CAPTCHAHEIGHT=80;
 		$im=imagecreatetruecolor(55, 24);
 		$bg=imagecolorallocatealpha($im, 0, 0, 0, 127);
 		$fg=imagecolorallocate($im, 255, 255, 255);
@@ -737,7 +742,6 @@ function send_captcha(): void
 			imagesetpixel($im, mt_rand(0, 120), mt_rand(0, 80), $dots);
 		}
 		imagedestroy($char);
-		echo '<img width="120" height="80" src="data:image/png;base64,';
 	}elseif($difficulty===4){ // extreme
 		$CAPTCHAWIDTH = 300;
 		$CAPTCHAHEIGHT = 300;
@@ -812,7 +816,6 @@ function send_captcha(): void
 			$follow=imagecolorallocate($im, mt_rand(10, 255), mt_rand(10, 255), mt_rand(10, 255));
 			imageline($im, $chars[$i]['x']+ $fontwidth / 2, $chars[$i]['y']+ $fontheight / 2, $chars[$i+1]['x']+4, $chars[$i+1]['y']+8, IMG_COLOR_STYLED);
 		}
-		echo '<img alt="CAPTCHA" width="' . $CAPTCHAWIDTH . '" height="' . $CAPTCHAHEIGHT . '" src="data:image/png;base64,';
 	} elseif ($difficulty===5 || $difficulty===6 || $difficulty===7 || $difficulty===8 || $difficulty===9 || $difficulty===10){ // TrueType
 		$CAPTCHAWIDTH = 620;
 		$CAPTCHAHEIGHT = 177;
@@ -943,8 +946,8 @@ function send_captcha(): void
 				}
 			}
 		}
-		echo '<img alt="" width="' . $CAPTCHAWIDTH . '" height="' .$CAPTCHAHEIGHT . '" src="data:image/png;base64,';
 	}
+	echo '<img alt="CAPTCHA" width="' . $CAPTCHAWIDTH . '" height="' . $CAPTCHAHEIGHT . '" src="data:image/png;base64,';
 	ob_start();
 	imagepng($im);
 	imagedestroy($im);
@@ -1079,12 +1082,12 @@ function send_setup(array $C): void
 		if($captcha===1){
 			echo ' selected';
 		}
-		echo '>'._('Simple (deprecated)').'</option>';
+		echo '>'._('Simple').'</option>';
 		echo '<option value="2"';
 		if($captcha===2){
 			echo ' selected';
 		}
-		echo '>'._('Moderate (deprecated)').'</option>';
+		echo '>'._('Moderate').'</option>';
 		echo '<option value="3"';
 		if($captcha===3){
 			echo ' selected';