Add crypto helpers for working with RSA keys.
This commit is contained in:
Paul Chote
@@ -9,6 +9,7 @@
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*/
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#endregion
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using System;
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using System.IO;
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using System.Linq;
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using System.Security.Cryptography;
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@@ -18,6 +19,222 @@ namespace OpenRA
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{
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public static class CryptoUtil
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{
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// Fixed byte pattern for the OID header
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static readonly byte[] OIDHeader = { 0x30, 0xD, 0x6, 0x9, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0xD, 0x1, 0x1, 0x1, 0x5, 0x0 };
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public static string EncodePEMPublicKey(RSAParameters parameters)
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{
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var data = Convert.ToBase64String(EncodePublicKey(parameters));
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var output = new StringBuilder();
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output.AppendLine("-----BEGIN PUBLIC KEY-----");
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for (var i = 0; i < data.Length; i += 64)
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output.AppendLine(data.Substring(i, Math.Min(64, data.Length - i)));
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output.Append("-----END PUBLIC KEY-----");
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return output.ToString();
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}
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public static RSAParameters DecodePEMPublicKey(string key)
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{
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try
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{
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// Reconstruct original key data
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var lines = key.Split('\n');
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var data = Convert.FromBase64String(lines.Skip(1).Take(lines.Length - 2).JoinWith(""));
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// Pull the modulus and exponent bytes out of the ASN.1 tree
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// Expect this to blow up if the key is not correctly formatted
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using (var s = new MemoryStream(data))
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{
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// SEQUENCE
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s.ReadByte();
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ReadTLVLength(s);
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// SEQUENCE -> fixed header junk
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s.ReadByte();
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var headerLength = ReadTLVLength(s);
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s.Position += headerLength;
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// SEQUENCE -> BIT_STRING
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s.ReadByte();
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ReadTLVLength(s);
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s.ReadByte();
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// SEQUENCE -> BIT_STRING -> SEQUENCE
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s.ReadByte();
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ReadTLVLength(s);
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// SEQUENCE -> BIT_STRING -> SEQUENCE -> INTEGER (modulus)
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s.ReadByte();
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var modulusLength = ReadTLVLength(s);
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s.ReadByte();
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var modulus = s.ReadBytes(modulusLength - 1);
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// SEQUENCE -> BIT_STRING -> SEQUENCE -> INTEGER (exponent)
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s.ReadByte();
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var exponentLength = ReadTLVLength(s);
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s.ReadByte();
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var exponent = s.ReadBytes(exponentLength - 1);
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return new RSAParameters
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{
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Modulus = modulus,
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Exponent = exponent
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};
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}
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}
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catch (Exception e)
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{
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throw new InvalidDataException("Invalid PEM public key", e);
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}
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}
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static byte[] EncodePublicKey(RSAParameters parameters)
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{
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using (var stream = new MemoryStream())
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{
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var writer = new BinaryWriter(stream);
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var modExpLength = TripletFullLength(parameters.Modulus.Length + 1) + TripletFullLength(parameters.Exponent.Length + 1);
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var bitStringLength = TripletFullLength(modExpLength + 1);
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var sequenceLength = TripletFullLength(bitStringLength + OIDHeader.Length);
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// SEQUENCE
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writer.Write((byte)0x30);
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WriteTLVLength(writer, sequenceLength);
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// SEQUENCE -> fixed header junk
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writer.Write(OIDHeader);
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// SEQUENCE -> BIT_STRING
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writer.Write((byte)0x03);
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WriteTLVLength(writer, bitStringLength);
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writer.Write((byte)0x00);
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// SEQUENCE -> BIT_STRING -> SEQUENCE
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writer.Write((byte)0x30);
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WriteTLVLength(writer, modExpLength);
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// SEQUENCE -> BIT_STRING -> SEQUENCE -> INTEGER
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// Modulus is padded with a zero to avoid issues with the sign bit
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writer.Write((byte)0x02);
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WriteTLVLength(writer, parameters.Modulus.Length + 1);
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writer.Write((byte)0);
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writer.Write(parameters.Modulus);
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// SEQUENCE -> BIT_STRING -> SEQUENCE -> INTEGER
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// Exponent is padded with a zero to avoid issues with the sign bit
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writer.Write((byte)0x02);
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WriteTLVLength(writer, parameters.Exponent.Length + 1);
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writer.Write((byte)0);
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writer.Write(parameters.Exponent);
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return stream.ToArray();
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}
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}
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static void WriteTLVLength(BinaryWriter writer, int length)
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{
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if (length < 0x80)
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{
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// Length < 128 is stored in a single byte
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writer.Write((byte)length);
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}
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else
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{
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// If 128 <= length < 256**128 first byte encodes number of bytes required to hold the length
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// High-bit is set as a flag to use this long-form encoding
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var lengthBytes = BitConverter.GetBytes(length).Reverse().SkipWhile(b => b == 0).ToArray();
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writer.Write((byte)(0x80 | lengthBytes.Length));
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writer.Write(lengthBytes);
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}
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}
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static int ReadTLVLength(Stream s)
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{
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var length = s.ReadByte();
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if (length < 0x80)
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return length;
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var data = new byte[4];
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s.ReadBytes(data, 0, Math.Min(length & 0x7F, 4));
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return BitConverter.ToInt32(data.ToArray(), 0);
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}
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static int TripletFullLength(int dataLength)
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{
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if (dataLength < 0x80)
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return 2 + dataLength;
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return 2 + dataLength + BitConverter.GetBytes(dataLength).Reverse().SkipWhile(b => b == 0).Count();
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}
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public static string DecryptString(RSAParameters parameters, string data)
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{
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try
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{
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using (var rsa = new RSACryptoServiceProvider())
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{
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rsa.ImportParameters(parameters);
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return Encoding.UTF8.GetString(rsa.Decrypt(Convert.FromBase64String(data), false));
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}
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}
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catch (Exception e)
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{
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Log.Write("debug", "Failed to decrypt string with exception: {0}", e);
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Console.WriteLine("String decryption failed: {0}", e);
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return null;
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}
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}
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public static string Sign(RSAParameters parameters, string data)
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{
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return Sign(parameters, Encoding.UTF8.GetBytes(data));
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}
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public static string Sign(RSAParameters parameters, byte[] data)
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{
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try
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{
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using (var rsa = new RSACryptoServiceProvider())
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{
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rsa.ImportParameters(parameters);
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using (var csp = SHA1.Create())
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return Convert.ToBase64String(rsa.SignHash(csp.ComputeHash(data), CryptoConfig.MapNameToOID("SHA1")));
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}
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}
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catch (Exception e)
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{
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Log.Write("debug", "Failed to sign string with exception: {0}", e);
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Console.WriteLine("String signing failed: {0}", e);
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return null;
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}
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}
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public static bool VerifySignature(RSAParameters parameters, string data, string signature)
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{
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return VerifySignature(parameters, Encoding.UTF8.GetBytes(data), signature);
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}
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public static bool VerifySignature(RSAParameters parameters, byte[] data, string signature)
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{
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try
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{
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using (var rsa = new RSACryptoServiceProvider())
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{
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rsa.ImportParameters(parameters);
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using (var csp = SHA1.Create())
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return rsa.VerifyHash(csp.ComputeHash(data), CryptoConfig.MapNameToOID("SHA1"), Convert.FromBase64String(signature));
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}
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}
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catch (Exception e)
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{
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Log.Write("debug", "Failed to verify signature with exception: {0}", e);
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Console.WriteLine("Signature validation failed: {0}", e);
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return false;
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}
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}
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public static string SHA1Hash(Stream data)
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{
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using (var csp = SHA1.Create())
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