From 99cb356b5ec17d9bc6b97b77ce5b17e6db33e93b Mon Sep 17 00:00:00 2001
From: Richard Webb <webby@beardmouse.co.uk>
Date: Tue, 12 May 2020 00:41:18 +0100
Subject: [PATCH] In ZipOutputStream.PutNextEntry, account for AES overhead
 when calculating compressed entry size

---
 src/ICSharpCode.SharpZipLib/Zip/ZipEntry.cs   | 22 ++++++++++++++++++-
 .../Zip/ZipOutputStream.cs                    | 17 ++++++--------
 2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/src/ICSharpCode.SharpZipLib/Zip/ZipEntry.cs b/src/ICSharpCode.SharpZipLib/Zip/ZipEntry.cs
index a6241cb0f..803c8a4ca 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/ZipEntry.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/ZipEntry.cs
@@ -655,7 +655,7 @@ public bool LocalHeaderRequiresZip64
 
 					if ((versionToExtract == 0) && IsCrypted)
 					{
-						trueCompressedSize += ZipConstants.CryptoHeaderSize;
+						trueCompressedSize += (ulong)this.EncryptionOverheadSize;
 					}
 
 					// TODO: A better estimation of the true limit based on compression overhead should be used
@@ -1013,6 +1013,26 @@ internal int AESOverheadSize
 			}
 		}
 
+		/// <summary>
+		/// Number of extra bytes required to hold the encryption header fields.
+		/// </summary>
+		internal int EncryptionOverheadSize
+		{
+			get
+			{
+				// Entry is not encrypted - no overhead
+				if (!this.IsCrypted)
+					return 0;
+
+				// Entry is encrypted using ZipCrypto
+				if (_aesEncryptionStrength == 0)
+					return ZipConstants.CryptoHeaderSize;
+
+				// Entry is encrypted using AES
+				return this.AESOverheadSize;
+			}
+		}
+
 		/// <summary>
 		/// Process extra data fields updating the entry based on the contents.
 		/// </summary>
diff --git a/src/ICSharpCode.SharpZipLib/Zip/ZipOutputStream.cs b/src/ICSharpCode.SharpZipLib/Zip/ZipOutputStream.cs
index bfd308daa..e7f72f048 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/ZipOutputStream.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/ZipOutputStream.cs
@@ -337,7 +337,9 @@ public void PutNextEntry(ZipEntry entry)
 				}
 				else
 				{
-					WriteLeInt(entry.IsCrypted ? (int)entry.CompressedSize + ZipConstants.CryptoHeaderSize : (int)entry.CompressedSize);
+					int entryCompressedSize = (int)entry.CompressedSize + entry.EncryptionOverheadSize;
+
+					WriteLeInt(entryCompressedSize);
 					WriteLeInt((int)entry.Size);
 				}
 			}
@@ -382,7 +384,9 @@ public void PutNextEntry(ZipEntry entry)
 				if (headerInfoAvailable)
 				{
 					ed.AddLeLong(entry.Size);
-					ed.AddLeLong(entry.CompressedSize);
+
+					long entryCompressedSize = entry.CompressedSize + entry.EncryptionOverheadSize;
+					ed.AddLeLong(entryCompressedSize);
 				}
 				else
 				{
@@ -540,14 +544,7 @@ public void CloseEntry()
 
 			if (curEntry.IsCrypted)
 			{
-				if (curEntry.AESKeySize > 0)
-				{
-					curEntry.CompressedSize += curEntry.AESOverheadSize;
-				}
-				else
-				{
-					curEntry.CompressedSize += ZipConstants.CryptoHeaderSize;
-				}
+				curEntry.CompressedSize += curEntry.EncryptionOverheadSize;
 			}
 
 			// Patch the header if possible