Merge branch 'turn-on-protectntfs-by-default'

This patch series makes it safe to use Git on Windows drives, even if
running on a mounted network share or within the Windows Subsystem for
Linux (WSL).

This topic branch addresses CVE-2019-1353.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

3 files changed, 31 insertions, 28 deletions

diff --git a/config.mak.uname b/config.mak.uname
index 6604b130f8..333bd399d0 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -379,7 +379,6 @@ ifeq ($(uname_S),Windows)
 	EXTLIBS = user32.lib advapi32.lib shell32.lib wininet.lib ws2_32.lib invalidcontinue.obj
 	PTHREAD_LIBS =
 	lib =
-	BASIC_CFLAGS += -DPROTECT_NTFS_DEFAULT=1
 ifndef DEBUG
 	BASIC_CFLAGS += -GL -Os -MD
 	BASIC_LDFLAGS += -LTCG
@@ -516,7 +515,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	COMPAT_OBJS += compat/mingw.o compat/winansi.o \
 		compat/win32/pthread.o compat/win32/syslog.o \
 		compat/win32/dirent.o
-	BASIC_CFLAGS += -DPROTECT_NTFS_DEFAULT=1
 	EXTLIBS += -lws2_32
 	GITLIBS += git.res
 	PTHREAD_LIBS =
diff --git a/environment.c b/environment.c
index 3fd4b10845..ab38deefa5 100644
--- a/environment.c
+++ b/environment.c
@@ -73,7 +73,7 @@ enum log_refs_config log_all_ref_updates = LOG_REFS_UNSET;
 int protect_hfs = PROTECT_HFS_DEFAULT;
 
 #ifndef PROTECT_NTFS_DEFAULT
-#define PROTECT_NTFS_DEFAULT 0
+#define PROTECT_NTFS_DEFAULT 1
 #endif
 int protect_ntfs = PROTECT_NTFS_DEFAULT;
 
diff --git a/path.c b/path.c
index 2037e2d8c1..43b16aabd4 100644
--- a/path.c
+++ b/path.c
@@ -1288,20 +1288,6 @@ int daemon_avoid_alias(const char *p)
 	}
 }
 
-static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
-{
-	if (len < skip)
-		return 0;
-	len -= skip;
-	path += skip;
-	while (len-- > 0) {
-		char c = *(path++);
-		if (c != ' ' && c != '.')
-			return 0;
-	}
-	return 1;
-}
-
 /*
  * On NTFS, we need to be careful to disallow certain synonyms of the `.git/`
  * directory:
@@ -1341,19 +1327,38 @@ static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
  */
 int is_ntfs_dotgit(const char *name)
 {
-	size_t len;
+	char c;
 
-	for (len = 0; ; 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;
-			if (only_spaces_and_periods(name, len, 5) &&
-					!strncasecmp(name, "git~1", 5))
-				return 1;
+	/*
+	 * Note that when we don't find `.git` or `git~1` we end up with `name`
+	 * advanced partway through the string. That's okay, though, as we
+	 * return immediately in those cases, without looking at `name` any
+	 * further.
+	 */
+	c = *(name++);
+	if (c == '.') {
+		/* .git */
+		if (((c = *(name++)) != 'g' && c != 'G') ||
+		    ((c = *(name++)) != 'i' && c != 'I') ||
+		    ((c = *(name++)) != 't' && c != 'T'))
 			return 0;
-		}
+	} else if (c == 'g' || c == 'G') {
+		/* git ~1 */
+		if (((c = *(name++)) != 'i' && c != 'I') ||
+		    ((c = *(name++)) != 't' && c != 'T') ||
+		    *(name++) != '~' ||
+		    *(name++) != '1')
+			return 0;
+	} else
+		return 0;
+
+	for (;;) {
+		c = *(name++);
+		if (!c || c == '\\' || c == '/' || c == ':')
+			return 1;
+		if (c != '.' && c != ' ')
+			return 0;
+	}
 }
 
 static int is_ntfs_dot_generic(const char *name,