File 0003-path-safeguard-.git-against-NTFS-Alternate... of Package git.9694

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File 0003-path-safeguard-.git-against-NTFS-Alternate-Streams-A.patch of Package git.9694

From c4475b2242ef5786ea9170f1e1f997c01a28ab9d Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Wed, 28 Aug 2019 12:22:17 +0200
Subject: [PATCH 03/17] path: safeguard `.git` against NTFS Alternate Streams
 Accesses

Probably inspired by HFS' resource streams, NTFS supports "Alternate
Data Streams": by appending `:<stream-name>` to the file name,
information in addition to the file contents can be written and read,
information that is copied together with the file (unless copied to a
non-NTFS location).

These Alternate Data Streams are typically used for things like marking
an executable as having just been downloaded from the internet (and
hence not necessarily being trustworthy).

In addition to a stream name, a stream type can be appended, like so:
`:<stream-name>:<stream-type>`. Unless specified, the default stream
type is `$DATA` for files and `$INDEX_ALLOCATION` for directories. In
other words, `.git::$INDEX_ALLOCATION` is a valid way to reference the
`.git` directory!

In our work in Git v2.2.1 to protect Git on NTFS drives under
`core.protectNTFS`, we focused exclusively on NTFS short names, unaware
of the fact that NTFS Alternate Data Streams offer a similar attack
vector.

Let's fix this.

Seeing as it is better to be safe than sorry, we simply disallow paths
referring to *any* NTFS Alternate Data Stream of `.git`, not just
`::$INDEX_ALLOCATION`. This also simplifies the implementation.

This closes CVE-2019-1352.

Further reading about NTFS Alternate Data Streams:
https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/c54dec26-1551-4d3a-a0ea-4fa40f848eb3

Reported-by: Nicolas Joly <Nicolas.Joly@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 path.c                         | 12 +++++++++++-
 t/t1014-read-tree-confusing.sh |  1 +
 2 files changed, 12 insertions(+), 1 deletion(-)

Index: git-2.12.3/path.c
===================================================================
--- git-2.12.3.orig/path.c
+++ git-2.12.3/path.c
@@ -1243,7 +1243,8 @@ int is_ntfs_dotgit(const char *name)
 	size_t len;
 
 	for (len = 0; ; len++)
-		if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
+		if (!name[len] || name[len] == '\\' || is_dir_sep(name[len]) ||
+		    name[len] == ':') {
 			if (only_spaces_and_periods(name, len, 4) &&
 					!strncasecmp(name, ".git", 4))
 				return 1;
Index: git-2.12.3/t/t1014-read-tree-confusing.sh
===================================================================
--- git-2.12.3.orig/t/t1014-read-tree-confusing.sh
+++ git-2.12.3/t/t1014-read-tree-confusing.sh
@@ -49,6 +49,7 @@ git~1
 .git.SPACE .git.{space}
 .\\\\.GIT\\\\foobar backslashes
 .git\\\\foobar backslashes2
+.git...:alternate-stream
 EOF
 
 test_expect_success 'utf-8 paths allowed with core.protectHFS off' '

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