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Diffstat (limited to 'Duplicati/Server/WebServer/CaptchaUtil.cs')
| -rw-r--r-- | Duplicati/Server/WebServer/CaptchaUtil.cs | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/Duplicati/Server/WebServer/CaptchaUtil.cs b/Duplicati/Server/WebServer/CaptchaUtil.cs new file mode 100644 index 000000000..a7a56b5db --- /dev/null +++ b/Duplicati/Server/WebServer/CaptchaUtil.cs @@ -0,0 +1,115 @@ +// Copyright (C) 2016, The Duplicati Team
+// http://www.duplicati.com, info@duplicati.com
+//
+// This library is free software; you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation; either version 2.1 of the
+// License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+using System;
+using System.Linq;
+using System.Drawing;
+using System.Drawing.Drawing2D;
+using System.Drawing.Text;
+
+namespace Duplicati.Server.WebServer
+{
+ /// <summary>
+ /// Helper class for creating Captcha images
+ /// </summary>
+ public static class CaptchaUtil
+ {
+ /// <summary>
+ /// A lookup string with characters to use
+ /// </summary>
+ private static readonly string DEFAULT_CHARS = "ACDEFGHJKLMNPQRTUVWXY34679";
+
+ /// <summary>
+ /// A range of possible brush colors
+ /// </summary>
+ private static readonly Brush[] BRUSH_COLORS =
+ typeof(Brushes)
+ .GetProperties(System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.Public)
+ .Where(x => x.PropertyType == typeof(Brush))
+ .Select(x => x.GetValue(null, null) as Brush)
+ .Where(x => x != null)
+ .ToArray();
+
+ /// <summary>
+ /// Creates a random answer.
+ /// </summary>
+ /// <returns>The random answer.</returns>
+ /// <param name="allowedchars">The list of allowed chars, supply a character multiple times to change frequency.</param>
+ /// <param name="minlength">The minimum answer length.</param>
+ /// <param name="maxlength">The maximum answer length.</param>
+ public static string CreateRandomAnswer(string allowedchars = null, int minlength = 10, int maxlength = 12)
+ {
+ allowedchars = allowedchars ?? DEFAULT_CHARS;
+ var rnd = new Random();
+ var len = rnd.Next(Math.Min(minlength, maxlength), Math.Max(minlength, maxlength) + 1);
+ if (len <= 0)
+ throw new ArgumentException($"The values ${minlength} and ${maxlength} gave a final length of {len} and it must be greater than 0");
+
+ return new string(Enumerable.Range(0, len).Select(x => allowedchars[rnd.Next(0, allowedchars.Length)]).ToArray());
+ }
+
+ /// <summary>
+ /// Creates a captcha image.
+ /// </summary>
+ /// <returns>The captcha image.</returns>
+ /// <param name="answer">The captcha solution string.</param>
+ /// <param name="size">The size of the image, omit to get a size based on the string.</param>
+ /// <param name="fontsize">The size of the font used to create the captcha.</param>
+ public static Bitmap CreateCaptcha(string answer, Size size = default(Size), int fontsize = 24)
+ {
+ if (size.Width == 0 || size.Height == 0)
+ size = new Size((answer.Length + 1) * fontsize, fontsize * 2);
+
+ var bmp = new Bitmap(size.Width, size.Height);
+ var rnd = new Random();
+ var stray_x = fontsize / 4;
+ var stray_y = size.Height / 4;
+
+ using (var graphics = Graphics.FromImage(bmp))
+ using (var font1 = new Font("Ariel", fontsize))
+ using (var font2 = new Font("Ariel", fontsize))
+ using (var font3 = new HatchBrush(HatchStyle.Shingle, Color.GhostWhite, Color.DarkBlue))
+ {
+ graphics.Clear(Color.White);
+ graphics.TextRenderingHint = TextRenderingHint.AntiAlias;
+
+ // Apply a some background string to make it hard to do OCR
+ foreach (var color in new[] { Color.Yellow, Color.LightGreen, Color.GreenYellow })
+ using (var brush = new SolidBrush(color))
+ graphics.DrawString(CreateRandomAnswer(minlength: answer.Length, maxlength: answer.Length), font2, brush, rnd.Next(-stray_x, stray_x), rnd.Next(-stray_y, stray_y));
+
+
+ var spacing = (size.Width / fontsize) + rnd.Next(0, stray_x);
+
+ // Create a vertical background lines
+ for (var i = rnd.Next(0, stray_x); i < size.Width; i += spacing)
+ using (var pen = new Pen(BRUSH_COLORS[rnd.Next(0, BRUSH_COLORS.Length)]))
+ graphics.DrawLine(pen, i + rnd.Next(-stray_x, stray_x), rnd.Next(0, stray_y), i + rnd.Next(-stray_x, stray_x), size.Height - rnd.Next(0, stray_y));
+
+ spacing = (size.Height / fontsize) + rnd.Next(0, stray_y);
+ // Create a horizontal background lines
+ for (var i = rnd.Next(0, stray_y); i < size.Height; i += spacing)
+ using (var pen = new Pen(BRUSH_COLORS[rnd.Next(0, BRUSH_COLORS.Length)]))
+ graphics.DrawLine(pen, rnd.Next(0, stray_x), i + rnd.Next(-stray_y, stray_y), size.Width - rnd.Next(0, stray_x), i + rnd.Next(-stray_y, stray_y));
+
+ // Draw the actual answer
+ graphics.DrawString(answer, font1, font3, ((size.Width - (fontsize * answer.Length)) / 2) + rnd.Next(-stray_x, stray_x), ((size.Height - (fontsize * 2)) / 2) + rnd.Next(-stray_y, stray_y));
+
+ return bmp;
+ }
+ }
+ }
+}
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