240 lines
8.7 KiB
C#
240 lines
8.7 KiB
C#
// Copyright (C) 2024, The Duplicati Team
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// https://duplicati.com, hello@duplicati.com
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//
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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using System;
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using System.Collections.Generic;
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using System.Security.Cryptography;
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namespace Duplicati.Library.Utility
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{
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public class SignatureReadingStream : System.IO.Stream, IDisposable
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{
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/// <summary>
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/// The size of the SHA256 output hash in bytes
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/// </summary>
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///
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internal const int SIGNED_HASH_SIZE = 128;
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/// <summary>
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/// The stream to read from
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/// </summary>
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private readonly System.IO.Stream m_stream;
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protected SignatureReadingStream()
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{
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}
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/// <summary>
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/// Creates a new stream that reads from the given stream and verifies the signature using any of the given keys
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/// </summary>
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/// <param name="stream">The stream with a signature</param>
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/// <param name="keys">The allowed keys</param>
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public SignatureReadingStream(System.IO.Stream stream, IEnumerable<System.Security.Cryptography.RSA> keys)
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{
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if (!VerifySignature(stream, keys))
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throw new System.IO.InvalidDataException("Unable to verify signature");
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m_stream = stream;
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this.Position = 0;
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}
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/// <summary>
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/// Wraps trying the keys one by one, returning true if any of the keys validate
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/// </summary>
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/// <param name="stream">The stream to verify</param>
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/// <param name="keys">The keys to try</param>
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/// <returns><c>true</c> if the stream is valid; <c>false</c> otherwise</returns>
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private static bool VerifySignature(System.IO.Stream stream, IEnumerable<System.Security.Cryptography.RSA> keys)
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{
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if (keys == null)
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return false;
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foreach (var key in keys)
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try
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{
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if (VerifySignature(stream, key))
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return true;
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}
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catch
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{
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}
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return false;
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}
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/// <summary>
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/// Verifies the signature of the stream using the given key
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/// </summary>
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/// <param name="stream">The stream to verify</param>
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/// <param name="key">The key to validate with</param>
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/// <returns><c>true</c> if the stream signature matches the key; <c>false</c> otherwise</returns>
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private static bool VerifySignature(System.IO.Stream stream, System.Security.Cryptography.RSA key)
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{
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stream.Position = 0;
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var signature = new byte[SIGNED_HASH_SIZE];
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if (Duplicati.Library.Utility.Utility.ForceStreamRead(stream, signature, signature.Length) != signature.Length)
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throw new System.IO.InvalidDataException("Unexpected end-of-stream while reading signature");
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var sha256 = System.Security.Cryptography.SHA256.Create();
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sha256.Initialize();
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var bytes = stream.Length - (signature.Length);
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var buf = new byte[8 * 1024];
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while (bytes > 0)
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{
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var r = stream.Read(buf, 0, (int)Math.Min(bytes, buf.Length));
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if (r == 0)
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throw new Exception("Unexpected end-of-stream while reading content");
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bytes -= r;
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sha256.TransformBlock(buf, 0, r, buf, 0);
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}
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sha256.TransformFinalBlock(buf, 0, 0);
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var hash = sha256.Hash;
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return key.VerifyHash(hash, signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
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}
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/// <summary>
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/// Creates a signed stream from the given data stream and writes the signature to the signed stream
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/// </summary>
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/// <param name="datastream">The stream to sign</param>
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/// <param name="signedstream">The stream with the signature</param>
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/// <param name="key">The key used to sign it</param>
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public static void CreateSignedStream(System.IO.Stream datastream, System.IO.Stream signedstream, System.Security.Cryptography.RSA key)
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{
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var sha256 = System.Security.Cryptography.SHA256.Create();
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datastream.Position = 0;
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signedstream.Position = SIGNED_HASH_SIZE;
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var buf = new byte[8 * 1024];
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var bytes = datastream.Length;
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while (bytes > 0)
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{
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var r = datastream.Read(buf, 0, (int)Math.Min(bytes, buf.Length));
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if (r == 0)
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throw new Exception("Unexpected end-of-stream while reading content");
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signedstream.Write(buf, 0, r);
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bytes -= r;
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sha256.TransformBlock(buf, 0, r, buf, 0);
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}
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sha256.TransformFinalBlock(buf, 0, 0);
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var hash = sha256.Hash;
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var signature = key.SignHash(hash, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
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if (signature.Length != SIGNED_HASH_SIZE)
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throw new System.IO.InvalidDataException("Unexpected signature length");
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signedstream.Position = 0;
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signedstream.Write(signature, 0, signature.Length);
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signedstream.Position = 0;
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if (!VerifySignature(signedstream, key))
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throw new System.IO.InvalidDataException("Unable to verify signature");
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}
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#region implemented abstract members of Stream
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public override void Flush()
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{
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try { m_stream.Flush(); }
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catch { }
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}
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public override int Read(byte[] buffer, int offset, int count)
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{
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return m_stream.Read(buffer, offset, count);
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}
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public override long Seek(long offset, System.IO.SeekOrigin origin)
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{
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switch (origin)
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{
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case System.IO.SeekOrigin.Current:
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return Seek(offset + this.Position, System.IO.SeekOrigin.Begin);
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case System.IO.SeekOrigin.End:
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return Seek(this.Length - offset, System.IO.SeekOrigin.Begin);
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case System.IO.SeekOrigin.Begin:
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default:
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return this.Position = offset;
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}
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}
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public override void SetLength(long value)
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{
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throw new InvalidOperationException();
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}
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public override void Write(byte[] buffer, int offset, int count)
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{
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throw new InvalidOperationException();
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}
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public override bool CanRead
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{
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get
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{
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return true;
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}
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}
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public override bool CanSeek
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{
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get
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{
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return true;
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}
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}
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public override bool CanWrite
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{
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get
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{
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return false;
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}
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}
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public override long Length
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{
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get
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{
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return m_stream.Length - SIGNED_HASH_SIZE;
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}
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}
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// Since the constructor sets the Position, we seal the implementation here to prevent subclasses
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// from potentially referencing uninitialized members.
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public sealed override long Position
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{
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get
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{
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return m_stream.Position - SIGNED_HASH_SIZE;
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}
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set
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{
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m_stream.Position = value + SIGNED_HASH_SIZE;
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}
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}
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#endregion
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}
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}
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