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‎Demo.AspNetCore.PushNotifications.Services.PushService/Client/Authentication/VapidAuthentication.cs‎

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using System;
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using System.Text;
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using System.Collections.Generic;
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using System.Security.Cryptography;
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using Newtonsoft.Json;
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using Org.BouncyCastle.Math;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Crypto.Signers;
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using Demo.AspNetCore.PushNotifications.Services.PushService.Client.Internals;
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namespace Demo.AspNetCore.PushNotifications.Services.PushService.Client.Authentication
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{
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internal class VapidAuthentication
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{
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#region Structures
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public readonly struct WebPushSchemeHeadersValues
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{
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public string AuthenticationHeaderValueParameter { get; }
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public string CryptoKeyHeaderValue { get; }
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public WebPushSchemeHeadersValues(string authenticationHeaderValueParameter, string cryptoKeyHeaderValue)
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: this()
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{
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AuthenticationHeaderValueParameter = authenticationHeaderValueParameter;
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CryptoKeyHeaderValue = cryptoKeyHeaderValue;
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}
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}
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#endregion
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#region Fields
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private const string AUDIENCE_CLAIM = "aud";
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private const string EXPIRATION_CLAIM = "exp";
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private const string SUBJECT_CLAIM = "sub";
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private const string P256ECDSA_PREFIX = "p256ecdsa=";
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private const string VAPID_AUTHENTICATION_HEADER_VALUE_PARAMETER_FORMAT = "t={0}, k={1}";
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private const int DEFAULT_EXPIRATION = 43200;
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private const int MAXIMUM_EXPIRATION = 86400;
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private string _subject;
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private string _publicKey;
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private string _privateKey;
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private ECPrivateKeyParameters _privateSigningKey;
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private int _expiration;
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private static readonly DateTime _unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0);
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private static readonly Dictionary<string, string> _jwtHeader = new Dictionary<string, string>
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{
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{ "typ", "JWT" },
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{ "alg", "ES256" }
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};
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#endregion
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#region Properties
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public string Subject
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{
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get { return _subject; }
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set
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{
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if (!String.IsNullOrWhiteSpace(value))
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{
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if (!value.StartsWith("mailto:"))
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{
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if (!Uri.IsWellFormedUriString(value, UriKind.Absolute) || ((new Uri(value)).Scheme != Uri.UriSchemeHttps))
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{
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throw new ArgumentException(nameof(Subject), "Subject should include a contact URI for the application server as either a 'mailto: ' (email) or an 'https:' URI");
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}
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}
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_subject = value;
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}
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else
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{
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_subject = null;
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}
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}
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}
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public string PublicKey
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{
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get { return _publicKey; }
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set
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{
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if (String.IsNullOrWhiteSpace(value))
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{
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throw new ArgumentNullException(nameof(PublicKey));
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}
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byte[] decodedPublicKey = UrlBase64Converter.FromUrlBase64String(value);
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if (decodedPublicKey.Length != 65)
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{
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throw new ArgumentException(nameof(PublicKey), "VAPID public key must be 65 bytes long");
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}
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_publicKey = value;
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}
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}
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public string PrivateKey
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{
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get { return _privateKey; }
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set
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{
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if (String.IsNullOrWhiteSpace(value))
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{
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throw new ArgumentNullException(nameof(PrivateKey));
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}
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byte[] decodedPrivateKey = UrlBase64Converter.FromUrlBase64String(value);
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if (decodedPrivateKey.Length != 32)
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{
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throw new ArgumentException(nameof(PrivateKey), "VAPID private key should be 32 bytes long");
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}
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_privateKey = value;
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_privateSigningKey = ECKeyHelper.GetECPrivateKeyParameters(decodedPrivateKey);
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}
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}
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public int Expiration
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{
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get { return _expiration; }
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set
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{
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if ((value <= 0) || (value > MAXIMUM_EXPIRATION))
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{
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throw new ArgumentOutOfRangeException(nameof(Expiration), "Expiration must be a number of seconds not longer than 24 hours");
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}
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_expiration = value;
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}
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}
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#endregion
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#region Constructor
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public VapidAuthentication(string publicKey, string privateKey)
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{
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PublicKey = publicKey;
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PrivateKey = privateKey;
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_expiration = DEFAULT_EXPIRATION;
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}
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#endregion
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#region Methods
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public string GetVapidSchemeAuthenticationHeaderValueParameter(string audience)
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{
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return String.Format(VAPID_AUTHENTICATION_HEADER_VALUE_PARAMETER_FORMAT, GetToken(audience), _publicKey);
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}
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public WebPushSchemeHeadersValues GetWebPushSchemeHeadersValues(string audience)
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{
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return new WebPushSchemeHeadersValues(GetToken(audience), P256ECDSA_PREFIX + _publicKey);
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}
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private string GetToken(string audience)
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{
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if (String.IsNullOrWhiteSpace(audience))
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{
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throw new ArgumentNullException(nameof(audience));
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}
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if (!Uri.IsWellFormedUriString(audience, UriKind.Absolute))
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{
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throw new ArgumentException(nameof(audience), "Audience should be an absolute URL");
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}
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Dictionary<string, object> jwtBody = GetJwtBody(audience);
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return GenerateJwtToken(_jwtHeader, jwtBody);
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}
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private Dictionary<string, object> GetJwtBody(string audience)
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{
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Dictionary<string, object> jwtBody = new Dictionary<string, object>
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{
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{ AUDIENCE_CLAIM, audience },
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{ EXPIRATION_CLAIM, GetAbsoluteExpiration(_expiration) }
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};
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if (_subject != null)
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{
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jwtBody.Add(SUBJECT_CLAIM, _subject);
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}
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return jwtBody;
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}
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private static long GetAbsoluteExpiration(int expirationSeconds)
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{
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TimeSpan unixEpochOffset = DateTime.UtcNow - _unixEpoch;
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return (long)unixEpochOffset.TotalSeconds + expirationSeconds;
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}
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private string GenerateJwtToken(Dictionary<string, string> jwtHeader, Dictionary<string, object> jwtBody)
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{
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string jwtInput = UrlBase64Converter.ToUrlBase64String(Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(jwtHeader)))
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+ "."
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+ UrlBase64Converter.ToUrlBase64String(Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(jwtBody)));
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byte[] jwtInputHash;
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using (var sha256Hasher = SHA256.Create())
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{
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jwtInputHash = sha256Hasher.ComputeHash(Encoding.UTF8.GetBytes(jwtInput));
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}
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ECDsaSigner jwtSigner = new ECDsaSigner();
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jwtSigner.Init(true, _privateSigningKey);
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BigInteger[] jwtSignature = jwtSigner.GenerateSignature(jwtInputHash);
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byte[] jwtSignatureFirstSegment = jwtSignature[0].ToByteArrayUnsigned();
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byte[] jwtSignatureSecondSegment = jwtSignature[1].ToByteArrayUnsigned();
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int jwtSignatureSegmentLength = Math.Max(jwtSignatureFirstSegment.Length, jwtSignatureSecondSegment.Length);
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byte[] combinedJwtSignature = new byte[2 * jwtSignatureSegmentLength];
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ByteArrayCopyWithPadLeft(jwtSignatureFirstSegment, combinedJwtSignature, 0, jwtSignatureSegmentLength);
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ByteArrayCopyWithPadLeft(jwtSignatureSecondSegment, combinedJwtSignature, jwtSignatureSegmentLength, jwtSignatureSegmentLength);
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return jwtInput + "." + UrlBase64Converter.ToUrlBase64String(combinedJwtSignature);
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}
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private static void ByteArrayCopyWithPadLeft(byte[] sourceArray, byte[] destinationArray, int destinationIndex, int destinationLengthToUse)
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{
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if (sourceArray.Length != destinationLengthToUse)
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{
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destinationIndex += (destinationLengthToUse - sourceArray.Length);
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}
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Array.Copy(sourceArray, 0, destinationArray, destinationIndex, sourceArray.Length);
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}
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#endregion
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}
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}

‎Demo.AspNetCore.PushNotifications.Services.PushService/Client/Internals/ECKeyHelper.cs‎

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using System;
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using System.IO;
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using Org.BouncyCastle.Asn1;
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using Org.BouncyCastle.Asn1.Nist;
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using Org.BouncyCastle.Asn1.X9;
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using Org.BouncyCastle.Crypto;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.OpenSsl;
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using Org.BouncyCastle.Security;
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namespace Demo.AspNetCore.PushNotifications.Services.PushService.Client.Internals
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{
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internal static class ECKeyHelper
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{
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internal static ECPrivateKeyParameters GetECPrivateKeyParameters(byte[] privateKey)
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{
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Asn1Object derSequence = new DerSequence(
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new DerInteger(1),
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new DerOctetString(privateKey),
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new DerTaggedObject(0, new DerObjectIdentifier("1.2.840.10045.3.1.7"))
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);
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string pemKey = "-----BEGIN EC PRIVATE KEY-----\n"
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+ Convert.ToBase64String(derSequence.GetDerEncoded())
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+ "\n-----END EC PRIVATE KEY----";
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PemReader pemKeyReader = new PemReader(new StringReader(pemKey));
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AsymmetricCipherKeyPair keyPair = (AsymmetricCipherKeyPair)pemKeyReader.ReadObject();
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return (ECPrivateKeyParameters)keyPair.Private;
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}
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internal static ECPublicKeyParameters GetECPublicKeyParameters(byte[] publicKey)
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{
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Asn1Object derSequence = new DerSequence(
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new DerSequence(new DerObjectIdentifier(@"1.2.840.10045.2.1"), new DerObjectIdentifier(@"1.2.840.10045.3.1.7")),
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new DerBitString(publicKey)
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);
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string pemKey = "-----BEGIN PUBLIC KEY-----\n"
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+ Convert.ToBase64String(derSequence.GetDerEncoded())
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+ "\n-----END PUBLIC KEY-----";
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PemReader pemKeyReader = new PemReader(new StringReader(pemKey));
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return (ECPublicKeyParameters)pemKeyReader.ReadObject();
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}
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internal static AsymmetricCipherKeyPair GenerateAsymmetricCipherKeyPair()
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{
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X9ECParameters ecParameters = NistNamedCurves.GetByName("P-256");
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ECDomainParameters ecDomainParameters = new ECDomainParameters(ecParameters.Curve, ecParameters.G, ecParameters.N, ecParameters.H, ecParameters.GetSeed());
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IAsymmetricCipherKeyPairGenerator keyPairGenerator = GeneratorUtilities.GetKeyPairGenerator("ECDH");
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keyPairGenerator.Init(new ECKeyGenerationParameters(ecDomainParameters, new SecureRandom()));
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return keyPairGenerator.GenerateKeyPair();
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}
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}
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}

‎Demo.AspNetCore.PushNotifications.Services.PushService/Client/Internals/UrlBase64Converter.cs‎

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using System;
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namespace Demo.AspNetCore.PushNotifications.Services.PushService.Client.Internals
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{
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internal static class UrlBase64Converter
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{
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internal static byte[] FromUrlBase64String(string input)
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{
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input = input.Replace('-', '+').Replace('_', '/');
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while (input.Length % 4 != 0)
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{
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input += "=";
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}
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return Convert.FromBase64String(input);
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}
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internal static string ToUrlBase64String(byte[] input)
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{
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return Convert.ToBase64String(input).Replace('+', '-').Replace('/', '_').TrimEnd('=');
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}
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}
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}

‎Demo.AspNetCore.PushNotifications.Services.PushService/Client/PushMessage.cs‎

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using System;
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namespace Demo.AspNetCore.PushNotifications.Services.PushService.Client
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{
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internal class PushMessage
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{
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#region Fields
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private int? _timeToLive;
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#endregion
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#region Properties
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public string Content { get; set; }
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public int? TimeToLive
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{
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get { return _timeToLive; }
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set
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{
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if (value.HasValue && (value.Value < 0))
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{
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throw new ArgumentOutOfRangeException(nameof(TimeToLive), "The TTL must be a non-negative integer");
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}
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_timeToLive = value;
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}
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}
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#endregion
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#region Constructors
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public PushMessage(string content)
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{
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Content = content;
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}
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#endregion
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}
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}

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