Don't rewind the temporary stream on write to the main one (#104)

grendello · web-flow · commit 9bccd749547b · 2022-01-25T18:54:05.000Z
Context: dbe3236 dbe3236 fixed an issue of data corruption when deleting files from the archive by properly creating temporary streams when `libzip` requested data modifications. However, a bug crept in which causes the temporary stream to be rewound, instead of the destination one, when data is written back. This has the effect of overwriting the ZIP local file header structure with, essentially, random data and causes errors similar to: error XABBA7000: Xamarin.Tools.Zip.ZipException: Zip archive inconsistent: entry 0: invalid WinZip AES extra field Xamarin.Android.Common.targets(2289,2): error ANDZA0000: zip W 01-25 15:03:13 9516 56652 WARNING: header mismatch The issue can be seen by either attempting to unpack the archive: $ 7z x base.zip ERROR: Headers Error : dex/classes.dex ERROR: Headers Error : root/assemblies/assemblies.blob $ unzip base.zip file #9: bad zipfile offset (local header sig): 49783 file #10: bad zipfile offset (local header sig): 127988 Or by looking at the file with `zipinfo -vv base.zip`: Central directory entry #10: --------------------------- There are an extra 9 bytes preceding this file. root/assemblies/assemblies.blob offset of local header from start of archive: 127988 (000000000001F3F4h) bytes Not only the local header is thought to be at the incorrect offset, it also doesn't have the correct signature: # show valid header $ hexdump -n 4 -C base.zip 00000000 50 4b 03 04 |PK..| # show invalid header $ hexdump -s 127988 -n 4 -C base.zip 0001f3f4 49 be 37 16 |I.7.| $ hexdump -s $((127988 - 9)) -n 4 -C base.zip 0001f3eb 88 26 de 2c |.&.,| Attempt to fix the problem by rewinding the destination stream on write. Fix found by Dean Ellis (@dellis1972)
diff --git a/LibZipSharp.props b/LibZipSharp.props
@@ -1,6 +1,6 @@
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
-    <_LibZipSharpAssemblyVersion>2.0.2</_LibZipSharpAssemblyVersion>
+    <_LibZipSharpAssemblyVersion>2.0.3</_LibZipSharpAssemblyVersion>
     <!--
       Nuget Version. You can append things like -alpha-1 etc to this value.
       But always leave the $(_LibZipSharpAssemblyVersion) value at the start.
diff --git a/LibZipSharp/Xamarin.Tools.Zip/ZipArchive.cs b/LibZipSharp/Xamarin.Tools.Zip/ZipArchive.cs
@@ -808,7 +808,7 @@ internal static unsafe Int64 stream_callback (IntPtr state, IntPtr data, UInt64
 					if (offset < 0) {
 						return offset;
 					}
-					if (offset != stream.Seek (offset, SeekOrigin.Begin)) {
+					if (offset != destination.Seek (offset, SeekOrigin.Begin)) {
 						return -1;
 					}
 					break;

Original file line number	Diff line number	Diff line change
`@@ -808,7 +808,7 @@ internal static unsafe Int64 stream_callback (IntPtr state, IntPtr data, UInt64`
`808`	`808`	`if (offset < 0) {`
`809`	`809`	`return offset;`
`810`	`810`	`}`
`811`		`- if (offset != stream.Seek (offset, SeekOrigin.Begin)) {`
	`811`	`+ if (offset != destination.Seek (offset, SeekOrigin.Begin)) {`
`812`	`812`	`return -1;`
`813`	`813`	`}`
`814`	`814`	`break;`