From 15534f466af2389844b8ae545f4d2116197bbf4f Mon Sep 17 00:00:00 2001
From: Adam Hathcock <adam@hathcock.uk>
Date: Sat, 28 Apr 2018 18:20:40 +0100
Subject: [PATCH] Add basic rar5 crypt header

---
 .../Common/Rar/Headers/CryptHeader.cs         | 50 +++++++++++++++++++
 src/SharpCompress/Common/Rar/Headers/Flags.cs |  9 +++-
 .../Common/Rar/Headers/RarHeaderFactory.cs    |  6 +++
 .../Rar/RarHeaderFactoryTest.cs               |  2 +-
 4 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 src/SharpCompress/Common/Rar/Headers/CryptHeader.cs

diff --git a/src/SharpCompress/Common/Rar/Headers/CryptHeader.cs b/src/SharpCompress/Common/Rar/Headers/CryptHeader.cs
new file mode 100644
index 00000000..6cb347c6
--- /dev/null
+++ b/src/SharpCompress/Common/Rar/Headers/CryptHeader.cs
@@ -0,0 +1,50 @@
+using SharpCompress.IO;
+
+namespace SharpCompress.Common.Rar.Headers
+{
+    internal class CryptHeader : RarHeader
+    {
+        
+        private const int CRYPT_VERSION = 0; // Supported encryption version.
+        private const int SIZE_SALT50 = 16;
+        private const int SIZE_PSWCHECK = 8;
+        private const int SIZE_PSWCHECK_CSUM = 4;
+        
+        
+        private bool UsePswCheck;
+        private uint Lg2Count; // Log2 of PBKDF2 repetition count.
+        private byte[] Salt;
+        private byte[] PswCheck;
+        
+        public CryptHeader(RarHeader header, RarCrcBinaryReader reader)
+            : base(header, reader, HeaderType.Crypt)
+        {
+        }
+
+        protected override void ReadFinish(MarkingBinaryReader reader)
+        {
+            var cryptVersion = reader.ReadRarVIntUInt32();
+            if (cryptVersion > CRYPT_VERSION)
+            {
+                //error?
+                return;
+            }
+
+            UsePswCheck = HasHeaderFlag(EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
+            Lg2Count    = reader.ReadRarVIntByte(1);
+            if (Lg2Count > 0)
+            {
+                //error?
+                return;
+            }
+
+            Salt = reader.ReadBytes(SIZE_SALT50);
+            if (UsePswCheck)
+            {
+                PswCheck = reader.ReadBytes(SIZE_PSWCHECK);
+                
+                var csum = reader.ReadBytes(SIZE_PSWCHECK_CSUM);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/SharpCompress/Common/Rar/Headers/Flags.cs b/src/SharpCompress/Common/Rar/Headers/Flags.cs
index 9c5060e9..7fe7d9b2 100644
--- a/src/SharpCompress/Common/Rar/Headers/Flags.cs
+++ b/src/SharpCompress/Common/Rar/Headers/Flags.cs
@@ -12,7 +12,8 @@ namespace SharpCompress.Common.Rar.Headers
         Protect,
         Sign,
         NewSub,
-        EndArchive
+        EndArchive,
+        Crypt
     }
 
     internal static class HeaderCodeV
@@ -40,6 +41,12 @@ namespace SharpCompress.Common.Rar.Headers
         public const ushort HasData = 0x8000;
     }
 
+    internal static class EncryptionFlagsV5
+    {   
+        // RAR 5.0 archive encryption header specific flags.
+        public const ushort CHFL_CRYPT_PSWCHECK = 0x0001; // Password check data is present.
+    }
+
     internal static class HeaderFlagsV5
     {
         public const ushort HasExtra = 0x0001;
diff --git a/src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs b/src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs
index cb670368..0a637241 100644
--- a/src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs
+++ b/src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs
@@ -158,6 +158,12 @@ namespace SharpCompress.Common.Rar.Headers
                     {
                         return new EndArchiveHeader(header, reader);
                     }
+                case HeaderCodeV.Rar5EncryptionHeader:
+                {
+                    var ch = new CryptHeader(header, reader);
+                    IsEncrypted = true;
+                    return ch;
+                }
                 default:
                     {
                         throw new InvalidFormatException("Unknown Rar Header: " + header.HeaderCode);
diff --git a/tests/SharpCompress.Test/Rar/RarHeaderFactoryTest.cs b/tests/SharpCompress.Test/Rar/RarHeaderFactoryTest.cs
index f334903b..c2732522 100644
--- a/tests/SharpCompress.Test/Rar/RarHeaderFactoryTest.cs
+++ b/tests/SharpCompress.Test/Rar/RarHeaderFactoryTest.cs
@@ -51,7 +51,7 @@ namespace SharpCompress.Test.Rar
             {
                 foreach (var header in rarHeaderFactory.ReadHeaders(stream))
                 {
-                    if (header.HeaderType == HeaderType.Archive)
+                    if (header.HeaderType == HeaderType.Archive || header.HeaderType == HeaderType.Crypt)
                     {
                         Assert.Equal(isEncrypted, rarHeaderFactory.IsEncrypted);
                         break;