* [PATCH 1/2] mingw: short-circuit the conversion of `/dev/null` to UTF-16
2019-12-21 22:04 [PATCH 0/2] Refuse to write to reserved filenames on Windows Johannes Schindelin via GitGitGadget
@ 2019-12-21 22:05 ` Johannes Schindelin via GitGitGadget
2019-12-21 22:05 ` [PATCH 2/2] mingw: refuse paths containing reserved names Johannes Schindelin via GitGitGadget
1 sibling, 0 replies; 3+ messages in thread
From: Johannes Schindelin via GitGitGadget @ 2019-12-21 22:05 UTC (permalink / raw)
To: git; +Cc: Johannes Schindelin, Junio C Hamano, Johannes Schindelin
From: Johannes Schindelin <johannes.schindelin@gmx.de>
In the next commit, we want to disallow accessing any path that contains
any segment that is equivalent to `NUL`. In particular, we want to
disallow accessing `NUL` (e.g. to prevent any repository from being
checked out that contains a file called `NUL`, as that is not a valid
file name on Windows).
However, there are legitimate use cases within Git itself to write to
the Null device. As Git is really a Linux project, it does not abstract
that idea, though, but instead uses `/dev/null` to describe this
intention.
So let's side-step the validation _specifically_ in the case that we
want to write to (or read from) `/dev/null`, via a dedicated short-cut
in the code that skips the call to `validate_win32_path()`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
compat/mingw.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)
diff --git a/compat/mingw.c b/compat/mingw.c
index bd24d913f9..03c4538ec8 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -484,16 +484,16 @@ int mingw_open (const char *filename, int oflags, ...)
return -1;
}
- if (filename && !strcmp(filename, "/dev/null"))
- filename = "nul";
-
if ((oflags & O_APPEND) && !is_local_named_pipe_path(filename))
open_fn = mingw_open_append;
else
open_fn = _wopen;
- if (xutftowcs_path(wfilename, filename) < 0)
+ if (filename && !strcmp(filename, "/dev/null"))
+ wcscpy(wfilename, L"nul");
+ else if (xutftowcs_path(wfilename, filename) < 0)
return -1;
+
fd = open_fn(wfilename, oflags, mode);
if (fd < 0 && (oflags & O_ACCMODE) != O_RDONLY && errno == EACCES) {
@@ -556,10 +556,13 @@ FILE *mingw_fopen (const char *filename, const char *otype)
return NULL;
}
if (filename && !strcmp(filename, "/dev/null"))
- filename = "nul";
- if (xutftowcs_path(wfilename, filename) < 0 ||
- xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
+ wcscpy(wfilename, L"nul");
+ else if (xutftowcs_path(wfilename, filename) < 0)
return NULL;
+
+ if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
+ return NULL;
+
if (hide && !access(filename, F_OK) && set_hidden_flag(wfilename, 0)) {
error("could not unhide %s", filename);
return NULL;
@@ -583,10 +586,13 @@ FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream)
return NULL;
}
if (filename && !strcmp(filename, "/dev/null"))
- filename = "nul";
- if (xutftowcs_path(wfilename, filename) < 0 ||
- xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
+ wcscpy(wfilename, L"nul");
+ else if (xutftowcs_path(wfilename, filename) < 0)
return NULL;
+
+ if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
+ return NULL;
+
if (hide && !access(filename, F_OK) && set_hidden_flag(wfilename, 0)) {
error("could not unhide %s", filename);
return NULL;
--
gitgitgadget
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] mingw: refuse paths containing reserved names
2019-12-21 22:04 [PATCH 0/2] Refuse to write to reserved filenames on Windows Johannes Schindelin via GitGitGadget
2019-12-21 22:05 ` [PATCH 1/2] mingw: short-circuit the conversion of `/dev/null` to UTF-16 Johannes Schindelin via GitGitGadget
@ 2019-12-21 22:05 ` Johannes Schindelin via GitGitGadget
1 sibling, 0 replies; 3+ messages in thread
From: Johannes Schindelin via GitGitGadget @ 2019-12-21 22:05 UTC (permalink / raw)
To: git; +Cc: Johannes Schindelin, Junio C Hamano, Johannes Schindelin
From: Johannes Schindelin <johannes.schindelin@gmx.de>
There are a couple of reserved names that cannot be file names on
Windows, such as `AUX`, `NUL`, etc. For an almost complete list, see
https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file
If one would try to create a directory named `NUL`, it would actually
"succeed", i.e. the call would return success, but nothing would be
created.
Worse, even adding a file extension to the reserved name does not make
it a valid file name. To understand the rationale behind that behavior,
see https://devblogs.microsoft.com/oldnewthing/20031022-00/?p=42073
Let's just disallow them all.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
compat/mingw.c | 104 ++++++++++++++++++++++++++++++++++++------
compat/mingw.h | 11 ++++-
t/t0060-path-utils.sh | 13 +++++-
3 files changed, 110 insertions(+), 18 deletions(-)
diff --git a/compat/mingw.c b/compat/mingw.c
index 03c4538ec8..f482ecd6da 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -393,7 +393,7 @@ int mingw_mkdir(const char *path, int mode)
int ret;
wchar_t wpath[MAX_PATH];
- if (!is_valid_win32_path(path)) {
+ if (!is_valid_win32_path(path, 0)) {
errno = EINVAL;
return -1;
}
@@ -479,7 +479,7 @@ int mingw_open (const char *filename, int oflags, ...)
mode = va_arg(args, int);
va_end(args);
- if (!is_valid_win32_path(filename)) {
+ if (!is_valid_win32_path(filename, !create)) {
errno = create ? EINVAL : ENOENT;
return -1;
}
@@ -550,14 +550,13 @@ FILE *mingw_fopen (const char *filename, const char *otype)
int hide = needs_hiding(filename);
FILE *file;
wchar_t wfilename[MAX_PATH], wotype[4];
- if (!is_valid_win32_path(filename)) {
+ if (filename && !strcmp(filename, "/dev/null"))
+ wcscpy(wfilename, L"nul");
+ else if (!is_valid_win32_path(filename, 1)) {
int create = otype && strchr(otype, 'w');
errno = create ? EINVAL : ENOENT;
return NULL;
- }
- if (filename && !strcmp(filename, "/dev/null"))
- wcscpy(wfilename, L"nul");
- else if (xutftowcs_path(wfilename, filename) < 0)
+ } else if (xutftowcs_path(wfilename, filename) < 0)
return NULL;
if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
@@ -580,14 +579,13 @@ FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream)
int hide = needs_hiding(filename);
FILE *file;
wchar_t wfilename[MAX_PATH], wotype[4];
- if (!is_valid_win32_path(filename)) {
+ if (filename && !strcmp(filename, "/dev/null"))
+ wcscpy(wfilename, L"nul");
+ else if (!is_valid_win32_path(filename, 1)) {
int create = otype && strchr(otype, 'w');
errno = create ? EINVAL : ENOENT;
return NULL;
- }
- if (filename && !strcmp(filename, "/dev/null"))
- wcscpy(wfilename, L"nul");
- else if (xutftowcs_path(wfilename, filename) < 0)
+ } else if (xutftowcs_path(wfilename, filename) < 0)
return NULL;
if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
@@ -2412,14 +2410,16 @@ static void setup_windows_environment(void)
}
}
-int is_valid_win32_path(const char *path)
+int is_valid_win32_path(const char *path, int allow_literal_nul)
{
+ const char *p = path;
int preceding_space_or_period = 0, i = 0, periods = 0;
if (!protect_ntfs)
return 1;
skip_dos_drive_prefix((char **)&path);
+ goto segment_start;
for (;;) {
char c = *(path++);
@@ -2434,7 +2434,83 @@ int is_valid_win32_path(const char *path)
return 1;
i = periods = preceding_space_or_period = 0;
- continue;
+
+segment_start:
+ switch (*path) {
+ case 'a': case 'A': /* AUX */
+ if (((c = path[++i]) != 'u' && c != 'U') ||
+ ((c = path[++i]) != 'x' && c != 'X')) {
+not_a_reserved_name:
+ path += i;
+ continue;
+ }
+ break;
+ case 'c': case 'C': /* COM<N>, CON, CONIN$, CONOUT$ */
+ if ((c = path[++i]) != 'o' && c != 'O')
+ goto not_a_reserved_name;
+ c = path[++i];
+ if (c == 'm' || c == 'M') { /* COM<N> */
+ if (!isdigit(path[++i]))
+ goto not_a_reserved_name;
+ } else if (c == 'n' || c == 'N') { /* CON */
+ c = path[i + 1];
+ if ((c == 'i' || c == 'I') &&
+ ((c = path[i + 2]) == 'n' ||
+ c == 'N') &&
+ path[i + 3] == '$')
+ i += 3; /* CONIN$ */
+ else if ((c == 'o' || c == 'O') &&
+ ((c = path[i + 2]) == 'u' ||
+ c == 'U') &&
+ ((c = path[i + 3]) == 't' ||
+ c == 'T') &&
+ path[i + 4] == '$')
+ i += 4; /* CONOUT$ */
+ } else
+ goto not_a_reserved_name;
+ break;
+ case 'l': case 'L': /* LPT<N> */
+ if (((c = path[++i]) != 'p' && c != 'P') ||
+ ((c = path[++i]) != 't' && c != 'T') ||
+ !isdigit(path[++i]))
+ goto not_a_reserved_name;
+ break;
+ case 'n': case 'N': /* NUL */
+ if (((c = path[++i]) != 'u' && c != 'U') ||
+ ((c = path[++i]) != 'l' && c != 'L') ||
+ (allow_literal_nul &&
+ !path[i + 1] && p == path))
+ goto not_a_reserved_name;
+ break;
+ case 'p': case 'P': /* PRN */
+ if (((c = path[++i]) != 'r' && c != 'R') ||
+ ((c = path[++i]) != 'n' && c != 'N'))
+ goto not_a_reserved_name;
+ break;
+ default:
+ continue;
+ }
+
+ /*
+ * So far, this looks like a reserved name. Let's see
+ * whether it actually is one: trailing spaces, a file
+ * extension, or an NTFS Alternate Data Stream do not
+ * matter, the name is still reserved if any of those
+ * follow immediately after the actual name.
+ */
+ i++;
+ if (path[i] == ' ') {
+ preceding_space_or_period = 1;
+ while (path[++i] == ' ')
+ ; /* skip all spaces */
+ }
+
+ c = path[i];
+ if (c && c != '.' && c != ':' && c != '/' && c != '\\')
+ goto not_a_reserved_name;
+
+ /* contains reserved name */
+ return 0;
case '.':
periods++;
/* fallthru */
diff --git a/compat/mingw.h b/compat/mingw.h
index 04ca731a6b..ebc1e6a773 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -461,10 +461,17 @@ char *mingw_query_user_email(void);
*
* - contain any of the reserved characters, e.g. `:`, `;`, `*`, etc
*
+ * - correspond to reserved names (such as `AUX`, `PRN`, etc)
+ *
+ * The `allow_literal_nul` parameter controls whether the path `NUL` should
+ * be considered valid (this makes sense e.g. before opening files, as it is
+ * perfectly legitimate to open `NUL` on Windows, just as it is to open
+ * `/dev/null` on Unix/Linux).
+ *
* Returns 1 upon success, otherwise 0.
*/
-int is_valid_win32_path(const char *path);
-#define is_valid_path(path) is_valid_win32_path(path)
+int is_valid_win32_path(const char *path, int allow_literal_nul);
+#define is_valid_path(path) is_valid_win32_path(path, 0)
/**
* Converts UTF-8 encoded string to UTF-16LE.
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index b193ed4205..eaf3be94e3 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -465,11 +465,14 @@ test_expect_success 'match .gitmodules' '
'
test_expect_success MINGW 'is_valid_path() on Windows' '
- test-tool path-utils is_valid_path \
+ test-tool path-utils is_valid_path \
win32 \
"win32 x" \
../hello.txt \
C:\\git \
+ comm \
+ conout.c \
+ lptN \
\
--not \
"win32 " \
@@ -477,7 +480,13 @@ test_expect_success MINGW 'is_valid_path() on Windows' '
"win32." \
"win32 . ." \
.../hello.txt \
- colon:test
+ colon:test \
+ "AUX.c" \
+ "abc/conOut\$ .xyz/test" \
+ lpt8 \
+ "lpt*" \
+ Nul \
+ "PRN./abc"
'
test_done
--
gitgitgadget
^ permalink raw reply related [flat|nested] 3+ messages in thread