Attempt to get AES decryption working in the case where reading the underlying stream returns less data than requested.

Author: Numpsy

src/ICSharpCode.SharpZipLib/Core/StreamUtils.cs

@@ -64,6 +64,54 @@ static public void ReadFully(Stream stream, byte[] buffer, int offset, int count
 			}
 		}
 
+		/// <summary>
+		/// Read as much data as possible from a <see cref="Stream"/>", up to the requested number of bytes
+		/// </summary>
+		/// <param name="stream">The stream to read data from.</param>
+		/// <param name="buffer">The buffer to store data in.</param>
+		/// <param name="offset">The offset at which to begin storing data.</param>
+		/// <param name="count">The number of bytes of data to store.</param>
+		/// <exception cref="ArgumentNullException">Required parameter is null</exception>
+		/// <exception cref="ArgumentOutOfRangeException"><paramref name="offset"/> and or <paramref name="count"/> are invalid.</exception>
+		static public int ReadRequestedBytes(Stream stream, byte[] buffer, int offset, int count)
+		{
+			if (stream == null)
+			{
+				throw new ArgumentNullException(nameof(stream));
+			}
+
+			if (buffer == null)
+			{
+				throw new ArgumentNullException(nameof(buffer));
+			}
+
+			// Offset can equal length when buffer and count are 0.
+			if ((offset < 0) || (offset > buffer.Length))
+			{
+				throw new ArgumentOutOfRangeException(nameof(offset));
+			}
+
+			if ((count < 0) || (offset + count > buffer.Length))
+			{
+				throw new ArgumentOutOfRangeException(nameof(count));
+			}
+
+			int totalReadCount = 0;
+			while (count > 0)
+			{
+				int readCount = stream.Read(buffer, offset, count);
+				if (readCount <= 0)
+				{
+					break;
+				}
+				offset += readCount;
+				count -= readCount;
+				totalReadCount += readCount;
+			}
+
+			return totalReadCount;
+		}
+
 		/// <summary>
 		/// Copy the contents of one <see cref="Stream"/> to another.
 		/// </summary>

src/ICSharpCode.SharpZipLib/Encryption/ZipAESStream.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Security.Cryptography;
+using ICSharpCode.SharpZipLib.Core;
 
 namespace ICSharpCode.SharpZipLib.Encryption
 {
@@ -78,7 +79,7 @@ public override int Read(byte[] buffer, int offset, int count)
 					_slideBufFreePos -= _slideBufStartPos;      // Note the -=
 					_slideBufStartPos = 0;
 				}
-				int obtained = _stream.Read(_slideBuffer, _slideBufFreePos, lengthToRead);
+				int obtained = StreamUtils.ReadRequestedBytes(_stream, _slideBuffer, _slideBufFreePos, lengthToRead);
 				_slideBufFreePos += obtained;
 
 				// Recalculate how much data we now have

src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs

@@ -3523,12 +3523,12 @@ private Stream CreateAndInitDecryptionStream(Stream baseStream, ZipEntry entry)
 					}
 					int saltLen = entry.AESSaltLen;
 					byte[] saltBytes = new byte[saltLen];
-					int saltIn = baseStream.Read(saltBytes, 0, saltLen);
+					int saltIn = StreamUtils.ReadRequestedBytes(baseStream, saltBytes, 0, saltLen);
 					if (saltIn != saltLen)
 						throw new ZipException("AES Salt expected " + saltLen + " got " + saltIn);
 					//
 					byte[] pwdVerifyRead = new byte[2];
-					baseStream.Read(pwdVerifyRead, 0, 2);
+					StreamUtils.ReadFully(baseStream, pwdVerifyRead);
 					int blockSize = entry.AESKeySize / 8;   // bits to bytes
 
 					var decryptor = new ZipAESTransform(rawPassword_, saltBytes, blockSize, false);