1 files changed, 102 insertions, 0 deletions
diff --git a/crypto/src/openpgp/SXprUtilities.cs b/crypto/src/openpgp/SXprUtilities.cs
new file mode 100644
index 000000000..68ff373a8
--- /dev/null
+++ b/crypto/src/openpgp/SXprUtilities.cs
@@ -0,0 +1,102 @@
+using System;
+using System.IO;
+
+using Org.BouncyCastle.Utilities.IO;
+
+namespace Org.BouncyCastle.Bcpg.OpenPgp
+{
+    /**
+     * Utility functions for looking a S-expression keys. This class will move when it finds a better home!
+     * <p>
+     * Format documented here:
+     * http://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=blob;f=agent/keyformat.txt;h=42c4b1f06faf1bbe71ffadc2fee0fad6bec91a97;hb=refs/heads/master
+     * </p>
+     */
+    public sealed class SXprUtilities
+    {
+        private SXprUtilities()
+        {
+        }
+
+        private static int ReadLength(Stream input, int ch)
+        {
+            int len = ch - '0';
+
+            while ((ch = input.ReadByte()) >= 0 && ch != ':')
+            {
+                len = len * 10 + ch - '0';
+            }
+
+            return len;
+        }
+
+        internal static string ReadString(Stream input, int ch)
+        {
+            int len = ReadLength(input, ch);
+
+            char[] chars = new char[len];
+
+            for (int i = 0; i != chars.Length; i++)
+            {
+                chars[i] = (char)input.ReadByte();
+            }
+
+            return new string(chars);
+        }
+
+        internal static byte[] ReadBytes(Stream input, int ch)
+        {
+            int len = ReadLength(input, ch);
+
+            byte[] data = new byte[len];
+
+            Streams.ReadFully(input, data);
+
+            return data;
+        }
+
+        internal static S2k ParseS2k(Stream input)
+        {
+            SkipOpenParenthesis(input);
+
+            string alg = ReadString(input, input.ReadByte());
+            byte[] iv = ReadBytes(input, input.ReadByte());
+            long iterationCount = Int64.Parse(ReadString(input, input.ReadByte()));
+
+            SkipCloseParenthesis(input);
+
+            // we have to return the actual iteration count provided.
+            return new MyS2k(HashAlgorithmTag.Sha1, iv, iterationCount);
+        }
+
+        internal static void SkipOpenParenthesis(Stream input)
+        {
+            int ch = input.ReadByte();
+            if (ch != '(')
+                throw new IOException("unknown character encountered");
+        }
+
+        internal static void SkipCloseParenthesis(Stream input)
+        {
+            int ch = input.ReadByte();
+            if (ch != ')')
+                throw new IOException("unknown character encountered");
+        }
+
+        private class MyS2k : S2k
+        {
+            private readonly long mIterationCount64;
+
+            internal MyS2k(HashAlgorithmTag algorithm, byte[] iv, long iterationCount64)
+                : base(algorithm, iv, (int)iterationCount64)
+            {
+                this.mIterationCount64 = iterationCount64;
+            }
+
+            public override long IterationCount
+            {
+                get { return mIterationCount64; }
+            }
+        }
+    }
+}