| | | 1 | | // Copyright (c) Microsoft Corporation. All rights reserved. |
| | | 2 | | // Licensed under the MIT License. |
| | | 3 | | |
| | | 4 | | using System.IO; |
| | | 5 | | using System.Threading; |
| | | 6 | | using System.Threading.Tasks; |
| | | 7 | | using Azure.Storage.Blobs.Models; |
| | | 8 | | using Azure.Storage.Cryptography; |
| | | 9 | | using Azure.Storage.Cryptography.Models; |
| | | 10 | | using Azure.Storage.Shared; |
| | | 11 | | using Metadata = System.Collections.Generic.IDictionary<string, string>; |
| | | 12 | | |
| | | 13 | | namespace Azure.Storage.Blobs |
| | | 14 | | { |
| | | 15 | | internal class BlobClientSideDecryptor |
| | | 16 | | { |
| | | 17 | | private readonly ClientSideDecryptor _decryptor; |
| | | 18 | | |
| | 0 | 19 | | public BlobClientSideDecryptor(ClientSideDecryptor decryptor) |
| | | 20 | | { |
| | 0 | 21 | | _decryptor = decryptor; |
| | 0 | 22 | | } |
| | | 23 | | |
| | | 24 | | public async Task<Stream> DecryptInternal( |
| | | 25 | | Stream content, |
| | | 26 | | Metadata metadata, |
| | | 27 | | HttpRange originalRange, |
| | | 28 | | string receivedContentRange, |
| | | 29 | | bool async, |
| | | 30 | | CancellationToken cancellationToken) |
| | | 31 | | { |
| | 0 | 32 | | ContentRange? contentRange = string.IsNullOrWhiteSpace(receivedContentRange) |
| | 0 | 33 | | ? default |
| | 0 | 34 | | : ContentRange.Parse(receivedContentRange); |
| | | 35 | | |
| | 0 | 36 | | EncryptionData encryptionData = GetAndValidateEncryptionDataOrDefault(metadata); |
| | 0 | 37 | | if (encryptionData == default) |
| | | 38 | | { |
| | 0 | 39 | | return await TrimStreamInternal(content, originalRange, contentRange, pulledOutIV: false, async, cancell |
| | | 40 | | } |
| | | 41 | | |
| | 0 | 42 | | bool ivInStream = originalRange.Offset >= Constants.ClientSideEncryption.EncryptionBlockSize; |
| | | 43 | | |
| | | 44 | | // this method throws when key cannot be resolved. Blobs is intended to throw on this failure. |
| | 0 | 45 | | var plaintext = await _decryptor.DecryptInternal( |
| | 0 | 46 | | content, |
| | 0 | 47 | | encryptionData, |
| | 0 | 48 | | ivInStream, |
| | 0 | 49 | | CanIgnorePadding(contentRange), |
| | 0 | 50 | | async, |
| | 0 | 51 | | cancellationToken).ConfigureAwait(false); |
| | | 52 | | |
| | 0 | 53 | | return await TrimStreamInternal(plaintext, originalRange, contentRange, ivInStream, async, cancellationToken |
| | 0 | 54 | | } |
| | | 55 | | |
| | | 56 | | private static async Task<Stream> TrimStreamInternal( |
| | | 57 | | Stream stream, |
| | | 58 | | HttpRange originalRange, |
| | | 59 | | ContentRange? receivedRange, |
| | | 60 | | bool pulledOutIV, |
| | | 61 | | bool async, |
| | | 62 | | CancellationToken cancellationToken) |
| | | 63 | | { |
| | | 64 | | // retrim start of stream to original requested location |
| | | 65 | | // keeping in mind whether we already pulled the IV out of the stream as well |
| | 0 | 66 | | int gap = (int)(originalRange.Offset - (receivedRange?.Start ?? 0)) |
| | 0 | 67 | | - (pulledOutIV ? Constants.ClientSideEncryption.EncryptionBlockSize : 0); |
| | | 68 | | |
| | 0 | 69 | | int read = 0; |
| | 0 | 70 | | while (gap > read) |
| | | 71 | | { |
| | 0 | 72 | | int toRead = gap - read; |
| | | 73 | | // throw away initial bytes we want to trim off; stream cannot seek into future |
| | 0 | 74 | | if (async) |
| | | 75 | | { |
| | 0 | 76 | | read += await stream.ReadAsync(new byte[toRead], 0, toRead, cancellationToken).ConfigureAwait(false) |
| | | 77 | | } |
| | | 78 | | else |
| | | 79 | | { |
| | 0 | 80 | | read += stream.Read(new byte[toRead], 0, toRead); |
| | | 81 | | } |
| | | 82 | | } |
| | | 83 | | |
| | 0 | 84 | | if (originalRange.Length.HasValue) |
| | | 85 | | { |
| | 0 | 86 | | stream = WindowStream.GetWindow(stream, originalRange.Length.Value); |
| | | 87 | | } |
| | | 88 | | |
| | 0 | 89 | | return stream; |
| | 0 | 90 | | } |
| | | 91 | | |
| | | 92 | | private static EncryptionData GetAndValidateEncryptionDataOrDefault(Metadata metadata) |
| | | 93 | | { |
| | 0 | 94 | | if (metadata == default) |
| | | 95 | | { |
| | 0 | 96 | | return default; |
| | | 97 | | } |
| | 0 | 98 | | if (!metadata.TryGetValue(Constants.ClientSideEncryption.EncryptionDataKey, out string encryptedDataString)) |
| | | 99 | | { |
| | 0 | 100 | | return default; |
| | | 101 | | } |
| | | 102 | | |
| | 0 | 103 | | EncryptionData encryptionData = EncryptionDataSerializer.Deserialize(encryptedDataString); |
| | | 104 | | |
| | 0 | 105 | | _ = encryptionData.ContentEncryptionIV ?? throw Errors.ClientSideEncryption.MissingEncryptionMetadata( |
| | 0 | 106 | | nameof(EncryptionData.ContentEncryptionIV)); |
| | 0 | 107 | | _ = encryptionData.WrappedContentKey.EncryptedKey ?? throw Errors.ClientSideEncryption.MissingEncryptionMeta |
| | 0 | 108 | | nameof(EncryptionData.WrappedContentKey.EncryptedKey)); |
| | | 109 | | |
| | 0 | 110 | | return encryptionData; |
| | | 111 | | } |
| | | 112 | | |
| | | 113 | | /// <summary> |
| | | 114 | | /// Gets whether to ignore padding options for decryption. |
| | | 115 | | /// </summary> |
| | | 116 | | /// <param name="contentRange">Downloaded content range.</param> |
| | | 117 | | /// <returns>True if we should ignore padding.</returns> |
| | | 118 | | /// <remarks> |
| | | 119 | | /// If the last cipher block of the blob was returned, we need the padding. Otherwise, we can ignore it. |
| | | 120 | | /// </remarks> |
| | | 121 | | private static bool CanIgnorePadding(ContentRange? contentRange) |
| | | 122 | | { |
| | | 123 | | // if Content-Range not present, we requested the whole blob |
| | 0 | 124 | | if (contentRange == null) |
| | | 125 | | { |
| | 0 | 126 | | return false; |
| | | 127 | | } |
| | | 128 | | |
| | | 129 | | // if range is wildcard, we requested the whole blob |
| | 0 | 130 | | if (!contentRange.Value.End.HasValue) |
| | | 131 | | { |
| | 0 | 132 | | return false; |
| | | 133 | | } |
| | | 134 | | |
| | | 135 | | // blob storage will always return ContentRange.Size |
| | | 136 | | // we don't have to worry about the impossible decision of what to do if it doesn't |
| | | 137 | | |
| | | 138 | | // did we request the last block? |
| | | 139 | | // end is inclusive/0-index, so end = n and size = n+1 means we requested the last block |
| | 0 | 140 | | if (contentRange.Value.Size - contentRange.Value.End == 1) |
| | | 141 | | { |
| | 0 | 142 | | return false; |
| | | 143 | | } |
| | | 144 | | |
| | 0 | 145 | | return true; |
| | | 146 | | } |
| | | 147 | | |
| | | 148 | | internal static HttpRange GetEncryptedBlobRange(HttpRange originalRange) |
| | | 149 | | { |
| | 0 | 150 | | int offsetAdjustment = 0; |
| | 0 | 151 | | long? adjustedDownloadCount = originalRange.Length; |
| | | 152 | | |
| | | 153 | | // Calculate offsetAdjustment. |
| | 0 | 154 | | if (originalRange.Offset != 0) |
| | | 155 | | { |
| | | 156 | | // Align with encryption block boundary. |
| | | 157 | | int diff; |
| | 0 | 158 | | if ((diff = (int)(originalRange.Offset % Constants.ClientSideEncryption.EncryptionBlockSize)) != 0) |
| | | 159 | | { |
| | 0 | 160 | | offsetAdjustment += diff; |
| | 0 | 161 | | if (adjustedDownloadCount != default) |
| | | 162 | | { |
| | 0 | 163 | | adjustedDownloadCount += diff; |
| | | 164 | | } |
| | | 165 | | } |
| | | 166 | | |
| | | 167 | | // Account for IV. |
| | 0 | 168 | | if (originalRange.Offset >= Constants.ClientSideEncryption.EncryptionBlockSize) |
| | | 169 | | { |
| | 0 | 170 | | offsetAdjustment += Constants.ClientSideEncryption.EncryptionBlockSize; |
| | | 171 | | // Increment adjustedDownloadCount if necessary. |
| | 0 | 172 | | if (adjustedDownloadCount != default) |
| | | 173 | | { |
| | 0 | 174 | | adjustedDownloadCount += Constants.ClientSideEncryption.EncryptionBlockSize; |
| | | 175 | | } |
| | | 176 | | } |
| | | 177 | | } |
| | | 178 | | |
| | | 179 | | // Align adjustedDownloadCount with encryption block boundary at the end of the range. Note that it is impos |
| | | 180 | | // to adjust past the end of the blob as an encrypted blob was padded to align to an encryption block bounda |
| | 0 | 181 | | if (adjustedDownloadCount != null) |
| | | 182 | | { |
| | 0 | 183 | | adjustedDownloadCount += ( |
| | 0 | 184 | | Constants.ClientSideEncryption.EncryptionBlockSize - (int)(adjustedDownloadCount |
| | 0 | 185 | | % Constants.ClientSideEncryption.EncryptionBlockSize) |
| | 0 | 186 | | ) % Constants.ClientSideEncryption.EncryptionBlockSize; |
| | | 187 | | } |
| | | 188 | | |
| | 0 | 189 | | return new HttpRange(originalRange.Offset - offsetAdjustment, adjustedDownloadCount); |
| | | 190 | | } |
| | | 191 | | } |
| | | 192 | | } |