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apis/Google.Cloud.Storage.V1/Google.Cloud.Storage.V1/UrlSigner.HmacBlobSigner.cs
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| // Copyright 2023 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"). | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // https://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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|
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| using Google.Api.Gax; | ||
| using System; | ||
| using System.Globalization; | ||
| using System.Security.Cryptography; | ||
| using System.Text; | ||
| using System.Threading; | ||
| using System.Threading.Tasks; | ||
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| namespace Google.Cloud.Storage.V1; | ||
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| public sealed partial class UrlSigner | ||
| { | ||
| /// <summary> | ||
| /// Blob signer to implement signing using an HMAC secret. | ||
| /// </summary> | ||
| public sealed class HmacBlobSigner : IBlobSigner | ||
| { | ||
| private const string DefaultPrefix = "GOOG4"; | ||
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| private readonly string _secret; | ||
| private readonly string _prefix; | ||
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| /// <inheritdoc/> | ||
| public string Id { get; } | ||
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| /// <inheritdoc/> | ||
| public string Algorithm => "GOOG4-HMAC-SHA256"; | ||
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| /// <summary> | ||
| /// Creates a new HMAC Blob Signer from an HMAC Key ID and Secret. | ||
| /// </summary> | ||
| /// <param name="keyId">The HMAC key ID. Must not be null or empty.</param> | ||
| /// <param name="secret">The HMAC key secret. Must not be null or empty.</param> | ||
| private HmacBlobSigner(string keyId, string secret) => | ||
| (Id, _secret, _prefix) = (GaxPreconditions.CheckNotNullOrEmpty(keyId, nameof(keyId)), GaxPreconditions.CheckNotNullOrEmpty(secret, nameof(secret)), DefaultPrefix); | ||
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| /// <summary> | ||
| /// Creates a new HMAC Blob Signer from an HMAC Key ID and Secret. | ||
| /// </summary> | ||
| /// <param name="keyId">The HMAC key ID. Must not be null or empty.</param> | ||
| /// <param name="secret">The HMAC key secret. Must not be null or empty.</param> | ||
| public static HmacBlobSigner Create(string keyId, string secret) => new HmacBlobSigner(keyId, secret); | ||
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| /// <inheritdoc/> | ||
| public string CreateSignature(byte[] data, BlobSignerParameters parameters) | ||
| { | ||
| GaxPreconditions.CheckNotNull(data, nameof(data)); | ||
| GaxPreconditions.CheckNotNull(parameters, nameof(parameters)); | ||
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| string date = parameters.SignatureTimestamp.ToString("yyyyMMdd", CultureInfo.InvariantCulture); | ||
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| // Implements the steps in https://cloud.google.com/storage/docs/authentication/signatures#derive-key | ||
| var utf8 = Encoding.UTF8; | ||
| byte[] initialKey = utf8.GetBytes(_prefix + _secret); | ||
| byte[] keyDate = Hash(initialKey, utf8.GetBytes(date)); | ||
| byte[] keyRegion = Hash(keyDate, utf8.GetBytes(parameters.Region)); | ||
| byte[] keyService = Hash(keyRegion, utf8.GetBytes(parameters.Service)); | ||
| byte[] signingKey = Hash(keyService, utf8.GetBytes(parameters.RequestType)); | ||
| byte[] signature = Hash(signingKey, data); | ||
| return Convert.ToBase64String(signature); | ||
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| static byte[] Hash(byte[] key, byte[] data) | ||
| { | ||
| using (HMACSHA256 hmac = new HMACSHA256(key)) | ||
| { | ||
| return hmac.ComputeHash(data); | ||
| } | ||
| } | ||
| } | ||
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| /// <inheritdoc/> | ||
| public Task<string> CreateSignatureAsync(byte[] data, BlobSignerParameters parameters, CancellationToken cancellationToken) => | ||
| Task.FromResult(CreateSignature(data, parameters)); | ||
| } | ||
| } |
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