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Add AES encryption support to ZipFile
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src/ICSharpCode.SharpZipLib/Encryption/ZipAESEncryptionStream.cs
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|---|---|---|
| @@ -0,0 +1,142 @@ | ||
| using System; | ||
| using System.IO; | ||
| using System.Security.Cryptography; | ||
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| namespace ICSharpCode.SharpZipLib.Encryption | ||
| { | ||
| /// <summary> | ||
| /// Encrypts AES ZIP entries. | ||
| /// </summary> | ||
| /// <remarks> | ||
| /// Based on information from http://www.winzip.com/aes_info.htm | ||
| /// and http://www.gladman.me.uk/cryptography_technology/fileencrypt/ | ||
| /// </remarks> | ||
| internal class ZipAESEncryptionStream : Stream | ||
| { | ||
| // The transform to use for encryption. | ||
| private ZipAESTransform transform; | ||
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| // The output stream to write the encrypted data to. | ||
| private readonly Stream outputStream; | ||
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| // Static to help ensure that multiple files within a zip will get different random salt | ||
| private static RandomNumberGenerator _aesRnd = RandomNumberGenerator.Create(); | ||
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| /// <summary> | ||
| /// Constructor | ||
| /// </summary> | ||
| /// <param name="stream">The stream on which to perform the cryptographic transformation.</param> | ||
| /// <param name="rawPassword">The password used to encrypt the entry.</param> | ||
| /// <param name="saltLength">The length of the salt to use.</param> | ||
| /// <param name="blockSize">The block size to use for transforming.</param> | ||
| public ZipAESEncryptionStream(Stream stream, string rawPassword, int saltLength, int blockSize) | ||
| { | ||
| // Set up stream. | ||
| this.outputStream = stream; | ||
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| // Initialise the encryption transform. | ||
| var salt = new byte[saltLength]; | ||
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| // Salt needs to be cryptographically random, and unique per file | ||
| if (_aesRnd == null) | ||
| _aesRnd = RandomNumberGenerator.Create(); | ||
| _aesRnd.GetBytes(salt); | ||
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| this.transform = new ZipAESTransform(rawPassword, salt, blockSize, true); | ||
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| // File format for AES: | ||
| // Size (bytes) Content | ||
| // ------------ ------- | ||
| // Variable Salt value | ||
| // 2 Password verification value | ||
| // Variable Encrypted file data | ||
| // 10 Authentication code | ||
| // | ||
| // Value in the "compressed size" fields of the local file header and the central directory entry | ||
| // is the total size of all the items listed above. In other words, it is the total size of the | ||
| // salt value, password verification value, encrypted data, and authentication code. | ||
| var pwdVerifier = this.transform.PwdVerifier; | ||
| this.outputStream.Write(salt, 0, salt.Length); | ||
| this.outputStream.Write(pwdVerifier, 0, pwdVerifier.Length); | ||
| } | ||
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| // This stream is write only. | ||
| public override bool CanRead => false; | ||
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| // We only support writing - no seeking about. | ||
| public override bool CanSeek => false; | ||
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| // Supports writing for encrypting. | ||
| public override bool CanWrite => true; | ||
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| // We don't track this. | ||
| public override long Length => throw new NotImplementedException(); | ||
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| // We don't track this, or support seeking. | ||
| public override long Position { get => throw new NotImplementedException(); set => throw new NotImplementedException(); } | ||
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| /// <summary> | ||
| /// When the stream is disposed, write the final blocks and AES Authentication code | ||
| /// </summary> | ||
| protected override void Dispose(bool disposing) | ||
| { | ||
| if (this.transform != null) | ||
| { | ||
| this.WriteAuthCode(); | ||
| this.transform.Dispose(); | ||
| this.transform = null; | ||
| } | ||
| } | ||
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| // <inheritdoc/> | ||
| public override void Flush() | ||
| { | ||
| this.outputStream.Flush(); | ||
| } | ||
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| // <inheritdoc/> | ||
| public override int Read(byte[] buffer, int offset, int count) | ||
| { | ||
| // ZipAESEncryptionStream is only used for encryption. | ||
| throw new NotImplementedException(); | ||
| } | ||
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| // <inheritdoc/> | ||
| public override long Seek(long offset, SeekOrigin origin) | ||
| { | ||
| // We don't support seeking. | ||
| throw new NotImplementedException(); | ||
| } | ||
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| // <inheritdoc/> | ||
| public override void SetLength(long value) | ||
| { | ||
| // We don't support setting the length. | ||
| throw new NotImplementedException(); | ||
| } | ||
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| // <inheritdoc/> | ||
| public override void Write(byte[] buffer, int offset, int count) | ||
| { | ||
| if (count == 0) | ||
| { | ||
| return; | ||
| } | ||
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| var outputBuffer = new byte[count]; | ||
| var outputCount = this.transform.TransformBlock(buffer, offset, count, outputBuffer, 0); | ||
| this.outputStream.Write(outputBuffer, 0, outputCount); | ||
| } | ||
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| // Write the auth code for the encrypted data to the output stream | ||
| private void WriteAuthCode() | ||
| { | ||
| // Transform the final block? | ||
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| // Write the AES Authentication Code (a hash of the compressed and encrypted data) | ||
| var authCode = this.transform.GetAuthCode(); | ||
| this.outputStream.Write(authCode, 0, 10); | ||
| this.outputStream.Flush(); | ||
| } | ||
| } | ||
| } |
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