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AppProtocolVersion.cs
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AppProtocolVersion.cs
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using System;
using System.Collections.Immutable;
using System.Diagnostics.Contracts;
using System.Globalization;
using System.Linq;
using Bencodex;
using Bencodex.Types;
using Libplanet.Crypto;
using NetMQ;
namespace Libplanet.Net
{
/// <summary>
/// A <em>claim</em> of a version.
/// <para>Every peer in network shows others their <see cref="AppProtocolVersion"/> information.
/// As every peer can change its software by itself, this <see cref="AppProtocolVersion"/>
/// is theoretically arbitrary, hence a “claim.” (i.e., no authority).</para>
/// <para>In order to verify who claimed a version, every <see cref="AppProtocolVersion"/>
/// has its <see cref="Signature"/> which is made by its <see cref="Signer"/>.
/// <see cref="Verify(PublicKey)"/> method purposes to determine whether an information
/// is claimed by its corresponding <see cref="Signer"/> in fact.</para>
/// </summary>
public readonly struct AppProtocolVersion : IEquatable<AppProtocolVersion>
{
/// <summary>
/// The version number. This does not have to be increased by only 1, but can be more
/// than that.
/// </summary>
public readonly int Version;
/// <summary>
/// Optional extra data about the version. This can be used for any purpose
/// by apps, such as a URL to download the software.
/// </summary>
public readonly IValue Extra;
/// <summary>
/// A signer who claims presence of a version.
/// </summary>
public readonly Address Signer;
private static readonly Codec _codec = new Codec();
private readonly ImmutableArray<byte> _signature;
/// <summary>
/// Initializes an <see cref="AppProtocolVersion"/> value with field values.
/// </summary>
/// <param name="version">Sets the <see cref="Version"/>.</param>
/// <param name="extra">Sets the <see cref="Extra"/>.</param>
/// <param name="signature">Sets the <see cref="Signature"/>.</param>
/// <param name="signer">Gets the <see cref="Signer"/>.</param>
public AppProtocolVersion(
int version,
IValue extra,
ImmutableArray<byte> signature,
Address signer
)
{
Version = version;
Extra = extra;
_signature = signature;
Signer = signer;
}
/// <summary>
/// A signature which verifies <seealso cref="Signer"/>'s claim of a version.
/// </summary>
public ImmutableArray<byte> Signature =>
_signature.IsDefault ? ImmutableArray<byte>.Empty : _signature;
/// <summary>
/// A token string which serializes an <see cref="AppProtocolVersion"/>.
/// <para>As this is designed to be easy to copy and paste, the format consists of only
/// printable characters in the ASCII character set.</para>
/// <para>A token can be deserialized into an <see cref="AppProtocolVersion"/> through
/// <see cref="FromToken(string)"/> method.</para>
/// </summary>
/// <seealso cref="FromToken(string)"/>
[Pure]
public string Token
{
get
{
string sig = Convert.ToBase64String(
Signature.ToBuilder().ToArray(),
Base64FormattingOptions.None
).Replace('/', '.');
var prefix =
$"{Version.ToString(CultureInfo.InvariantCulture)}/{Signer.ToHex()}/{sig}";
if (Extra is null)
{
return prefix;
}
string extra = Convert.ToBase64String(
_codec.Encode(Extra),
Base64FormattingOptions.None
).Replace('/', '.');
return $"{prefix}/{extra}";
}
}
[Pure]
public static bool operator ==(AppProtocolVersion left, AppProtocolVersion right) =>
left.Equals(right);
[Pure]
public static bool operator !=(AppProtocolVersion left, AppProtocolVersion right) =>
!(left == right);
/// <summary>
/// Claim a <paramref name="version"/> with <paramref name="extra"/> data and sign it
/// using the given private key.
/// </summary>
/// <param name="signer">A private key to sign the claim.</param>
/// <param name="version">A version to claim.</param>
/// <param name="extra">Extra data to claim.</param>
/// <returns>A signed version claim.</returns>
/// <exception cref="ArgumentNullException">Thrown when <paramref name="signer"/> is
/// <c>null</c>.</exception>
public static AppProtocolVersion Sign(PrivateKey signer, int version, IValue extra = null)
{
if (signer is null)
{
throw new ArgumentNullException(nameof(signer));
}
return new AppProtocolVersion(
version,
extra,
ImmutableArray.Create(signer.Sign(GetMessage(version, extra))),
new Address(signer.PublicKey)
);
}
/// <summary>
/// Deserializes a <see cref="Token"/> into an <see cref="AppProtocolVersion"/> object.
/// </summary>
/// <param name="token">A <see cref="Token"/> string.</param>
/// <returns>A deserialized <see cref="AppProtocolVersion"/> object.</returns>
/// <exception cref="ArgumentNullException">Thrown when <c>null</c> is passed to
/// <paramref name="token"/>.</exception>
/// <exception cref="FormatException">Thrown when the given <paramref name="token"/>'s
/// format is invalid. The detailed reason is in the message.</exception>
/// <seealso cref="Token"/>
public static AppProtocolVersion FromToken(string token)
{
if (token is null)
{
throw new ArgumentNullException(nameof(token));
}
int pos, pos2;
pos = token.IndexOf('/');
if (pos < 0)
{
throw new FormatException("Failed to find the first field delimiter.");
}
int version;
try
{
version = int.Parse(token.Substring(0, pos), CultureInfo.InvariantCulture);
}
catch (Exception e) when (e is OverflowException || e is FormatException)
{
throw new FormatException($"Failed to parse a version number: {e}", e);
}
pos++;
pos2 = token.IndexOf('/', pos);
if (pos2 < 0)
{
throw new FormatException("Failed to find the second field delimiter.");
}
Address signer;
try
{
signer = new Address(token.Substring(pos, pos2 - pos));
}
catch (ArgumentException e)
{
throw new FormatException($"Failed to parse a signer address: {e}", e);
}
pos2++;
pos = token.IndexOf('/', pos2);
string sigEncoded = pos < 0 ? token.Substring(pos2) : token.Substring(pos2, pos - pos2);
ImmutableArray<byte> sig;
try
{
sig = ImmutableArray.Create(Convert.FromBase64String(sigEncoded.Replace('.', '/')));
}
catch (FormatException e)
{
throw new FormatException($"Failed to parse a signature: {e}", e);
}
IValue extra = null;
if (pos >= 0)
{
pos++;
string extraEncoded = token.Substring(pos);
byte[] extraBytes = Convert.FromBase64String(extraEncoded.Replace('.', '/'));
try
{
extra = _codec.Decode(extraBytes);
}
catch (DecodingException e)
{
throw new FormatException(
$"Failed to parse extra data (offset = {pos}): {e}",
e
);
}
}
return new AppProtocolVersion(version, extra, sig, signer);
}
/// <summary>
/// Verifies whether the claim is certainly signed by the <see cref="Signer"/>.
/// </summary>
/// <param name="publicKey">A public key of the <see cref="Signer"/>.</param>
/// <returns><c>true</c> if and only if the given <paramref name="publicKey"/> is
/// <see cref="Signer"/>'s and the <see cref="Signature"/> is certainly signed by
/// the <see cref="Signer"/>.</returns>
[Pure]
public bool Verify(PublicKey publicKey) =>
Signer.Equals(new Address(publicKey)) &&
publicKey.Verify(GetMessage(Version, Extra), Signature.ToBuilder().ToArray());
/// <inheritdoc/>
[Pure]
public bool Equals(AppProtocolVersion other) =>
/* The reason why we need to check other fields than the Signature is that
this struct in itself does not guarantee its Signature is derived from
other field values. A value of this struct can represent an invalid claim. */
Version == other.Version &&
Signer.Equals(other.Signer) &&
Equals(Extra, other.Extra) &&
Signature.SequenceEqual(other.Signature);
/// <inheritdoc/>
[Pure]
public override bool Equals(object obj) =>
obj is AppProtocolVersion other && Equals(other);
/// <inheritdoc/>
[Pure]
public override int GetHashCode()
{
int hash = 17;
unchecked
{
hash *= 31 + Version.GetHashCode();
hash *= 31 + (Extra is null ? 0 : Extra.GetHashCode());
hash *= 31 + Signature.GetHashCode();
hash *= 31 + Signer.GetHashCode();
}
return hash;
}
/// <inheritdoc/>
[Pure]
public override string ToString() => string.Format(
CultureInfo.InvariantCulture,
Extra is null ? "{0}" : "{0} ({1})",
Version,
Extra
);
/// <summary>
/// Gets a deterministic message to sign.
/// </summary>
/// <returns>A deterministic message to sign.</returns>
[Pure]
private static byte[] GetMessage(int version, IValue extra)
{
byte[] msg = NetworkOrderBitsConverter.GetBytes(version);
if (!(extra is null))
{
byte[] extraBytes = _codec.Encode(extra);
int versionLength = msg.Length;
Array.Resize(ref msg, versionLength + extraBytes.Length);
extraBytes.CopyTo(msg, versionLength);
}
return msg;
}
}
}