From a94971b023f4583ea4b2c9c9f7a71d53f9781d58 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Fri, 6 Sep 2019 00:09:10 +0200 Subject: [PATCH] mingw: handle `subst`-ed "DOS drives" MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Over a decade ago, in 25fe217b86c (Windows: Treat Windows style path names., 2008-03-05), Git was taught to handle absolute Windows paths, i.e. paths that start with a drive letter and a colon. Unbeknownst to us, while drive letters of physical drives are limited to letters of the English alphabet, there is a way to assign virtual drive letters to arbitrary directories, via the `subst` command, which is _not_ limited to English letters. It is therefore possible to have absolute Windows paths of the form `1:\what\the\hex.txt`. Even "better": pretty much arbitrary Unicode letters can also be used, e.g. `ä:\tschibät.sch`. While it can be sensibly argued that users who set up such funny drive letters really seek adverse consequences, the Windows Operating System is known to be a platform where many users are at the mercy of administrators who have their very own idea of what constitutes a reasonable setup. Therefore, let's just make sure that such funny paths are still considered absolute paths by Git, on Windows. In addition to Unicode characters, pretty much any character is a valid drive letter, as far as `subst` is concerned, even `:` and `"` or even a space character. While it is probably the opposite of smart to use them, let's safeguard `is_dos_drive_prefix()` against all of them. Note: `[::1]:repo` is a valid URL, but not a valid path on Windows. As `[` is now considered a valid drive letter, we need to be very careful to avoid misinterpreting such a string as valid local path in `url_is_local_not_ssh()`. To do that, we use the just-introduced function `is_valid_path()` (which will label the string as invalid file name because of the colon characters). This fixes CVE-2019-1351. Reported-by: Nicolas Joly Signed-off-by: Johannes Schindelin --- compat/win32/path-utils.c | 24 ++++++++++++++++++++++++ compat/win32/path-utils.h | 4 ++-- connect.c | 2 +- t/t0060-path-utils.sh | 9 +++++++++ 4 files changed, 36 insertions(+), 3 deletions(-) diff --git a/compat/win32/path-utils.c b/compat/win32/path-utils.c index d9d3641de8..70352af283 100644 --- a/compat/win32/path-utils.c +++ b/compat/win32/path-utils.c @@ -1,5 +1,29 @@ #include "../../git-compat-util.h" +int mingw_has_dos_drive_prefix(const char *path) +{ + int i; + + /* + * Does it start with an ASCII letter (i.e. highest bit not set), + * followed by a colon? + */ + if (!(0x80 & (unsigned char)*path)) + return *path && path[1] == ':' ? 2 : 0; + + /* + * While drive letters must be letters of the English alphabet, it is + * possible to assign virtually _any_ Unicode character via `subst` as + * a drive letter to "virtual drives". Even `1`, or `ä`. Or fun stuff + * like this: + * + * subst ֍: %USERPROFILE%\Desktop + */ + for (i = 1; i < 4 && (0x80 & (unsigned char)path[i]); i++) + ; /* skip first UTF-8 character */ + return path[i] == ':' ? i + 1 : 0; +} + int win32_skip_dos_drive_prefix(char **path) { int ret = has_dos_drive_prefix(*path); diff --git a/compat/win32/path-utils.h b/compat/win32/path-utils.h index 0f70d43920..22b0c63349 100644 --- a/compat/win32/path-utils.h +++ b/compat/win32/path-utils.h @@ -1,5 +1,5 @@ -#define has_dos_drive_prefix(path) \ - (isalpha(*(path)) && (path)[1] == ':' ? 2 : 0) +int mingw_has_dos_drive_prefix(const char *path); +#define has_dos_drive_prefix mingw_has_dos_drive_prefix int win32_skip_dos_drive_prefix(char **path); #define skip_dos_drive_prefix win32_skip_dos_drive_prefix static inline int win32_is_dir_sep(int c) diff --git a/connect.c b/connect.c index 2778481264..4050a797bf 100644 --- a/connect.c +++ b/connect.c @@ -511,7 +511,7 @@ int url_is_local_not_ssh(const char *url) const char *colon = strchr(url, ':'); const char *slash = strchr(url, '/'); return !colon || (slash && slash < colon) || - has_dos_drive_prefix(url); + (has_dos_drive_prefix(url) && is_valid_path(url)); } static const char *prot_name(enum protocol protocol) diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh index c7b53e494b..e9b61efdff 100755 --- a/t/t0060-path-utils.sh +++ b/t/t0060-path-utils.sh @@ -165,6 +165,15 @@ test_expect_success 'absolute path rejects the empty string' ' test_must_fail test-tool path-utils absolute_path "" ' +test_expect_success MINGW ':\\abc is an absolute path' ' + for letter in : \" C Z 1 ä + do + path=$letter:\\abc && + absolute="$(test-path-utils absolute_path "$path")" && + test "$path" = "$absolute" || return 1 + done +' + test_expect_success 'real path rejects the empty string' ' test_must_fail test-tool path-utils real_path "" ' -- 2.23.0