From: Johannes Schindelin <johannes.schindelin@gmx.de>
To: cygwin-patches@cygwin.com
Subject: [PATCH 1/2] Treat Windows Store's "app execution aliases" as symbolic links
Date: Fri, 12 Mar 2021 16:11:47 +0100 (CET) [thread overview]
Message-ID: <nycvar.QRO.7.76.6.2103121611440.50@tvgsbejvaqbjf.bet> (raw)
When the Windows Store version of Python is installed, so-called "app
execution aliases" are put into the `PATH`. These are reparse points
under the hood, with an undocumented format.
We do know a bit about this format, though, as per the excellent analysis:
https://www.tiraniddo.dev/2019/09/overview-of-windows-execution-aliases.html
The first 4 bytes is the reparse tag, in this case it's
0x8000001B which is documented in the Windows SDK as
IO_REPARSE_TAG_APPEXECLINK. Unfortunately there doesn't seem to
be a corresponding structure, but with a bit of reverse
engineering we can work out the format is as follows:
Version: <4 byte integer>
Package ID: <NUL Terminated Unicode String>
Entry Point: <NUL Terminated Unicode String>
Executable: <NUL Terminated Unicode String>
Application Type: <NUL Terminated Unicode String>
Let's treat them as symbolic links. For example, in this developer's
setup, this will result in the following nice output:
$ cd $LOCALAPPDATA/Microsoft/WindowsApps/
$ ls -l python3.exe
lrwxrwxrwx 1 me 4096 105 Aug 23 2020 python3.exe -> '/c/Program Files/WindowsApps/PythonSoftwareFoundation.Python.3.7_3.7.2544.0_x64__qbz5n2kfra8p0/python.exe'
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
winsup/cygwin/path.cc | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index f3b9913bd0..63f377efb1 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -2538,6 +2538,30 @@ check_reparse_point_target (HANDLE h, bool remote, PREPARSE_DATA_BUFFER rp,
if (check_reparse_point_string (psymbuf))
return PATH_SYMLINK | PATH_REP;
}
+ else if (!remote && rp->ReparseTag == IO_REPARSE_TAG_APPEXECLINK)
+ {
+ /* App execution aliases are commonly used by Windows Store apps. */
+ WCHAR *buf = (WCHAR *)(rp->GenericReparseBuffer.DataBuffer + 4);
+ DWORD size = rp->ReparseDataLength / sizeof(WCHAR), n;
+
+ /*
+ It seems that app execution aliases have a payload of four
+ NUL-separated wide string: package id, entry point, executable
+ and application type. We're interested in the executable. */
+ for (int i = 0; i < 3 && size > 0; i++)
+ {
+ n = wcsnlen (buf, size - 1);
+ if (i == 2 && n > 0 && n < size)
+ {
+ RtlInitCountedUnicodeString (psymbuf, buf, n * sizeof(WCHAR));
+ return PATH_SYMLINK | PATH_REP;
+ }
+ if (i == 2)
+ break;
+ buf += n + 1;
+ size -= n + 1;
+ }
+ }
else if (rp->ReparseTag == IO_REPARSE_TAG_LX_SYMLINK)
{
/* WSL symlink. Problem: We have to convert the path to UTF-16 for
--
2.30.2
next reply other threads:[~2021-03-12 15:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 15:11 Johannes Schindelin [this message]
2021-03-12 17:03 ` Joe Lowe
2021-03-14 0:21 ` Johannes Schindelin
2021-03-14 3:41 ` Joe Lowe
2021-03-15 3:19 ` Johannes Schindelin
2021-03-15 19:04 ` Hans-Bernhard Bröker
2021-03-22 15:22 ` Johannes Schindelin
2021-03-22 21:54 ` Hans-Bernhard Bröker
2021-03-23 9:30 ` Corinna Vinschen
2021-03-24 18:55 ` Hans-Bernhard Bröker
2021-03-24 20:58 ` Ken Brown
2021-03-26 1:29 ` Hans-Bernhard Bröker
2021-03-15 10:17 ` Corinna Vinschen
2021-03-15 19:52 ` Corinna Vinschen
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