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2019-12-06Git 2.15.4v2.15.4Johannes Schindelin
Signed-off-by: Johannes Schindelin <>
2019-12-06submodule: reject submodule.update = !command in .gitmodulesJonathan Nieder
Since ac1fbbda2013 (submodule: do not copy unknown update mode from .gitmodules, 2013-12-02), Git has been careful to avoid copying [submodule "foo"] update = !run an arbitrary scary command from .gitmodules to a repository's local config, copying in the setting 'update = none' instead. The gitmodules(5) manpage documents the intention: The !command form is intentionally ignored here for security reasons Unfortunately, starting with v2.20.0-rc0 (which integrated ee69b2a9 (submodule--helper: introduce new update-module-mode helper, 2018-08-13, first released in v2.20.0-rc0)), there are scenarios where we *don't* ignore it: if the config store contains no setting, the submodule-config API falls back to reading .gitmodules and the repository-supplied !command gets run after all. This was part of a general change over time in submodule support to read more directly from .gitmodules, since unlike .git/config it allows a project to change values between branches and over time (while still allowing .git/config to override things). But it was never intended to apply to this kind of dangerous configuration. The behavior change was not advertised in ee69b2a9's commit message and was missed in review. Let's take the opportunity to make the protection more robust, even in Git versions that are technically not affected: instead of quietly converting 'update = !command' to 'update = none', noisily treat it as an error. Allowing the setting but treating it as meaning something else was just confusing; users are better served by seeing the error sooner. Forbidding the construct makes the semantics simpler and means we can check for it in fsck (in a separate patch). As a result, the submodule-config API cannot read this value from .gitmodules under any circumstance, and we can declare with confidence For security reasons, the '!command' form is not accepted here. Reported-by: Joern Schneeweisz <> Signed-off-by: Jonathan Nieder <> Signed-off-by: Johannes Schindelin <>
2019-12-06Sync with 2.14.6Johannes Schindelin
* maint-2.14: (28 commits) Git 2.14.6 mingw: handle `subst`-ed "DOS drives" mingw: refuse to access paths with trailing spaces or periods mingw: refuse to access paths with illegal characters unpack-trees: let merged_entry() pass through do_add_entry()'s errors quote-stress-test: offer to test quoting arguments for MSYS2 sh t6130/t9350: prepare for stringent Win32 path validation quote-stress-test: allow skipping some trials quote-stress-test: accept arguments to test via the command-line tests: add a helper to stress test argument quoting mingw: fix quoting of arguments Disallow dubiously-nested submodule git directories protect_ntfs: turn on NTFS protection by default path: also guard `.gitmodules` against NTFS Alternate Data Streams is_ntfs_dotgit(): speed it up mingw: disallow backslash characters in tree objects' file names path: safeguard `.git` against NTFS Alternate Streams Accesses clone --recurse-submodules: prevent name squatting on Windows is_ntfs_dotgit(): only verify the leading segment test-path-utils: offer to run a protectNTFS/protectHFS benchmark ...
2019-12-06Git 2.14.6v2.14.6Johannes Schindelin
Signed-off-by: Johannes Schindelin <>
2019-12-05Merge branch 'win32-accommodate-funny-drive-names'Johannes Schindelin
While the only permitted drive letters for physical drives on Windows are letters of the US-English alphabet, this restriction does not apply to virtual drives assigned via `subst <letter>: <path>`. To prevent targeted attacks against systems where "funny" drive letters such as `1` or `!` are assigned, let's handle them as regular drive letters on Windows. This fixes CVE-2019-1351. Signed-off-by: Johannes Schindelin <>
2019-12-05Merge branch 'win32-filenames-cannot-have-trailing-spaces-or-periods'Johannes Schindelin
On Windows, filenames cannot have trailing spaces or periods, when opening such paths, they are stripped automatically. Read: you can open the file `README` via the file name `README . . .`. This ambiguity can be used in combination with other security bugs to cause e.g. remote code execution during recursive clones. This patch series fixes that. Signed-off-by: Johannes Schindelin <>
2019-12-05Merge branch 'fix-mingw-quoting-bug'Johannes Schindelin
This patch fixes a vulnerability in the Windows-specific code where a submodule names ending in a backslash were quoted incorrectly, and that bug could be abused to insert command-line parameters e.g. to `ssh` in a recursive clone. Note: this bug is Windows-only, as we have to construct a command line for the process-to-spawn, unlike Linux/macOS, where `execv()` accepts an already-split command line. While at it, other quoting issues are fixed as well. Signed-off-by: Johannes Schindelin <>
2019-12-05Merge branch 'dubiously-nested-submodules'Johannes Schindelin
Recursive clones are currently affected by a vulnerability that is caused by too-lax validation of submodule names. This topic branch fixes that. Signed-off-by: Johannes Schindelin <>
2019-12-05Merge branch 'turn-on-protectntfs-by-default'Johannes Schindelin
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 <>
2019-12-05mingw: handle `subst`-ed "DOS drives"Johannes Schindelin
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 <>
2019-12-05Merge branch 'disallow-dotgit-via-ntfs-alternate-data-streams'Johannes Schindelin
This patch series plugs an attack vector we had overlooked in our December 2014 work on `core.protectNTFS`. Essentially, the path `.git::$INDEX_ALLOCATION/config` is interpreted as `.git/config` when NTFS Alternate Data Streams are available (which they are on Windows, and at least on network shares that are SMB-mounted on macOS). Needless to say: we don't want that. In fact, we want to stay on the very safe side and not even special-case the `$INDEX_ALLOCATION` stream type: let's just prevent Git from touching _any_ explicitly specified Alternate Data Stream of `.git`. In essence, we'll prevent Git from tracking, or writing to, any path with a segment of the form `.git:<anything>`. Signed-off-by: Johannes Schindelin <>
2019-12-05mingw: refuse to access paths with trailing spaces or periodsJohannes Schindelin
When creating a directory on Windows whose path ends in a space or a period (or chains thereof), the Win32 API "helpfully" trims those. For example, `mkdir("abc ");` will return success, but actually create a directory called `abc` instead. This stems back to the DOS days, when all file names had exactly 8 characters plus exactly 3 characters for the file extension, and the only way to have shorter names was by padding with spaces. Sadly, this "helpful" behavior is a bit inconsistent: after a successful `mkdir("abc ");`, a `mkdir("abc /def")` will actually _fail_ (because the directory `abc ` does not actually exist). Even if it would work, we now have a serious problem because a Git repository could contain directories `abc` and `abc `, and on Windows, they would be "merged" unintentionally. As these paths are illegal on Windows, anyway, let's disallow any accesses to such paths on that Operating System. For practical reasons, this behavior is still guarded by the config setting `core.protectNTFS`: it is possible (and at least two regression tests make use of it) to create commits without involving the worktree. In such a scenario, it is of course possible -- even on Windows -- to create such file names. Among other consequences, this patch disallows submodules' paths to end in spaces on Windows (which would formerly have confused Git enough to try to write into incorrect paths, anyway). While this patch does not fix a vulnerability on its own, it prevents an attack vector that was exploited in demonstrations of a number of recently-fixed security bugs. The regression test added to `t/` reflects that attack vector. Note that we have to adjust the test case "prevent git~1 squatting on Windows" in `t/` because of a very subtle issue. It tries to clone two submodules whose names differ only in a trailing period character, and as a consequence their git directories differ in the same way. Previously, when Git tried to clone the second submodule, it thought that the git directory already existed (because on Windows, when you create a directory with the name `b.` it actually creates `b`), but with this patch, the first submodule's clone will fail because of the illegal name of the git directory. Therefore, when cloning the second submodule, Git will take a different code path: a fresh clone (without an existing git directory). Both code paths fail to clone the second submodule, both because the the corresponding worktree directory exists and is not empty, but the error messages are worded differently. Signed-off-by: Johannes Schindelin <>
2019-12-05quote-stress-test: offer to test quoting arguments for MSYS2 shJohannes Schindelin
It is unfortunate that we need to quote arguments differently on Windows, depending whether we build a command-line for MSYS2's `sh` or for other Windows executables. We already have a test helper to verify the latter, with this patch we can also verify the former. Signed-off-by: Johannes Schindelin <>
2019-12-05mingw: refuse to access paths with illegal charactersJohannes Schindelin
Certain characters are not admissible in file names on Windows, even if Cygwin/MSYS2 (and therefore, Git for Windows' Bash) pretend that they are, e.g. `:`, `<`, `>`, etc Let's disallow those characters explicitly in Windows builds of Git. Note: just like trailing spaces or periods, it _is_ possible on Windows to create commits adding files with such illegal characters, as long as the operation leaves the worktree untouched. To allow for that, we continue to guard `is_valid_win32_path()` behind the config setting `core.protectNTFS`, so that users _can_ continue to do that, as long as they turn the protections off via that config setting. Among other problems, this prevents Git from trying to write to an "NTFS Alternate Data Stream" (which refers to metadata stored alongside a file, under a special name: "<filename>:<stream-name>"). This fix therefore also prevents an attack vector that was exploited in demonstrations of a number of recently-fixed security bugs. Further reading on illegal characters in Win32 filenames: Signed-off-by: Johannes Schindelin <>
2019-12-05unpack-trees: let merged_entry() pass through do_add_entry()'s errorsJohannes Schindelin
A `git clone` will end with exit code 0 when `merged_entry()` returns a positive value during a call of `unpack_trees()` to `traverse_trees()`. The reason is that `unpack_trees()` will interpret a positive value not to be an error. The problem is, however, that `add_index_entry()` (which is called by `merged_entry()` can report an error, and we really should fail the entire clone in such a case. Let's fix this problem, in preparation for a Windows-specific patch disallowing `mkdir()` with directory names that contain a trailing space (which is illegal on NTFS): we want `git clone` to abort when a path cannot be checked out due to that condition. Signed-off-by: Johannes Schindelin <>
2019-12-05quote-stress-test: allow skipping some trialsJohannes Schindelin
When the, say, 93rd trial run fails, it is a good idea to have a way to skip the first 92 trials and dig directly into the 93rd in a debugger. Signed-off-by: Johannes Schindelin <>
2019-12-05t6130/t9350: prepare for stringent Win32 path validationJohannes Schindelin
On Windows, file names cannot contain asterisks nor newline characters. In an upcoming commit, we will make this limitation explicit, disallowing even the creation of commits that introduce such file names. However, in the test scripts touched by this patch, we _know_ that those paths won't be checked out, so we _want_ to allow such file names. Happily, the stringent path validation will be guarded via the `core.protectNTFS` flag, so all we need to do is to force that flag off temporarily. Signed-off-by: Johannes Schindelin <>
2019-12-05quote-stress-test: accept arguments to test via the command-lineJohannes Schindelin
When the stress test reported a problem with quoting certain arguments, it is helpful to have a facility to play with those arguments in order to find out whether variations of those arguments are affected, too. Let's allow `test-run-command quote-stress-test -- <args>` to be used for that purpose. Signed-off-by: Johannes Schindelin <>
2019-12-05tests: add a helper to stress test argument quotingGarima Singh
On Windows, we have to do all the command-line argument quoting ourselves. Worse: we have to have two versions of said quoting, one for MSYS2 programs (which have their own dequoting rules) and the rest. We care mostly about the rest, and to make sure that that works, let's have a stress test that comes up with all kinds of awkward arguments, verifying that a spawned sub-process receives those unharmed. Signed-off-by: Garima Singh <> Signed-off-by: Johannes Schindelin <>
2019-12-05Disallow dubiously-nested submodule git directoriesJohannes Schindelin
Currently it is technically possible to let a submodule's git directory point right into the git dir of a sibling submodule. Example: the git directories of two submodules with the names `hippo` and `hippo/hooks` would be `.git/modules/hippo/` and `.git/modules/hippo/hooks/`, respectively, but the latter is already intended to house the former's hooks. In most cases, this is just confusing, but there is also a (quite contrived) attack vector where Git can be fooled into mistaking remote content for file contents it wrote itself during a recursive clone. Let's plug this bug. To do so, we introduce the new function `validate_submodule_git_dir()` which simply verifies that no git dir exists for any leading directories of the submodule name (if there are any). Note: this patch specifically continues to allow sibling modules names of the form `core/lib`, `core/doc`, etc, as long as `core` is not a submodule name. This fixes CVE-2019-1387. Reported-by: Nicolas Joly <> Signed-off-by: Johannes Schindelin <>
2019-12-05protect_ntfs: turn on NTFS protection by defaultJohannes Schindelin
Back in the DOS days, in the FAT file system, file names always consisted of a base name of length 8 plus a file extension of length 3. Shorter file names were simply padded with spaces to the full 8.3 format. Later, the FAT file system was taught to support _also_ longer names, with an 8.3 "short name" as primary file name. While at it, the same facility allowed formerly illegal file names, such as `.git` (empty base names were not allowed), which would have the "short name" `git~1` associated with it. For backwards-compatibility, NTFS supports alternative 8.3 short filenames, too, even if starting with Windows Vista, they are only generated on the system drive by default. We addressed the problem that the `.git/` directory can _also_ be accessed via `git~1/` (when short names are enabled) in 2b4c6efc821 (read-cache: optionally disallow NTFS .git variants, 2014-12-16), i.e. since Git v1.9.5, by introducing the config setting `core.protectNTFS` and enabling it by default on Windows. In the meantime, Windows 10 introduced the "Windows Subsystem for Linux" (short: WSL), i.e. a way to run Linux applications/distributions in a thinly-isolated subsystem on Windows (giving rise to many a "2016 is the Year of Linux on the Desktop" jokes). WSL is getting increasingly popular, also due to the painless way Linux application can operate directly ("natively") on files on Windows' file system: the Windows drives are mounted automatically (e.g. `C:` as `/mnt/c/`). Taken together, this means that we now have to enable the safe-guards of Git v1.9.5 also in WSL: it is possible to access a `.git` directory inside `/mnt/c/` via the 8.3 name `git~1` (unless short name generation was disabled manually). Since regular Linux distributions run in WSL, this means we have to enable `core.protectNTFS` at least on Linux, too. To enable Services for Macintosh in Windows NT to store so-called resource forks, NTFS introduced "Alternate Data Streams". Essentially, these constitute additional metadata that are connected to (and copied with) their associated files, and they are accessed via pseudo file names of the form `filename:<stream-name>:<stream-type>`. In a recent patch, we extended `core.protectNTFS` to also protect against accesses via NTFS Alternate Data Streams, e.g. to prevent contents of the `.git/` directory to be "tracked" via yet another alternative file name. While it is not possible (at least by default) to access files via NTFS Alternate Data Streams from within WSL, the defaults on macOS when mounting network shares via SMB _do_ allow accessing files and directories in that way. Therefore, we need to enable `core.protectNTFS` on macOS by default, too, and really, on any Operating System that can mount network shares via SMB/CIFS. A couple of approaches were considered for fixing this: 1. We could perform a dynamic NTFS check similar to the `core.symlinks` check in `init`/`clone`: instead of trying to create a symbolic link in the `.git/` directory, we could create a test file and try to access `.git/config` via 8.3 name and/or Alternate Data Stream. 2. We could simply "flip the switch" on `core.protectNTFS`, to make it "on by default". The obvious downside of 1. is that it won't protect worktrees that were clone with a vulnerable Git version already. We considered patching code paths that check out files to check whether we're running on an NTFS system dynamically and persist the result in the repository-local config setting `core.protectNTFS`, but in the end decided that this solution would be too fragile, and too involved. The obvious downside of 2. is that everybody will have to "suffer" the performance penalty incurred from calling `is_ntfs_dotgit()` on every path, even in setups where. After the recent work to accelerate `is_ntfs_dotgit()` in most cases, it looks as if the time spent on validating ten million random file names increases only negligibly (less than 20ms, well within the standard deviation of ~50ms). Therefore the benefits outweigh the cost. Another downside of this is that paths that might have been acceptable previously now will be forbidden. Realistically, though, this is an improvement because public Git hosters already would reject any `git push` that contains such file names. Note: There might be a similar problem mounting HFS+ on Linux. However, this scenario has been considered unlikely and in light of the cost (in the aforementioned benchmark, `core.protectHFS = true` increased the time from ~440ms to ~610ms), it was decided _not_ to touch the default of `core.protectHFS`. This change addresses CVE-2019-1353. Reported-by: Nicolas Joly <> Helped-by: Garima Singh <> Signed-off-by: Johannes Schindelin <>
2019-12-05path: also guard `.gitmodules` against NTFS Alternate Data StreamsJohannes Schindelin
We just safe-guarded `.git` against NTFS Alternate Data Stream-related attack vectors, and now it is time to do the same for `.gitmodules`. Note: In the added regression test, we refrain from verifying all kinds of variations between short names and NTFS Alternate Data Streams: as the new code disallows _all_ Alternate Data Streams of `.gitmodules`, it is enough to test one in order to know that all of them are guarded against. Signed-off-by: Johannes Schindelin <>
2019-12-05mingw: fix quoting of argumentsJohannes Schindelin
We need to be careful to follow proper quoting rules. For example, if an argument contains spaces, we have to quote them. Double-quotes need to be escaped. Backslashes need to be escaped, but only if they are followed by a double-quote character. We need to be _extra_ careful to consider the case where an argument ends in a backslash _and_ needs to be quoted: in this case, we append a double-quote character, i.e. the backslash now has to be escaped! The current code, however, fails to recognize that, and therefore can turn an argument that ends in a single backslash into a quoted argument that now ends in an escaped double-quote character. This allows subsequent command-line parameters to be split and part of them being mistaken for command-line options, e.g. through a maliciously-crafted submodule URL during a recursive clone. Technically, we would not need to quote _all_ arguments which end in a backslash _unless_ the argument needs to be quoted anyway. For example, `test\` would not need to be quoted, while `test \` would need to be. To keep the code simple, however, and therefore easier to reason about and ensure its correctness, we now _always_ quote an argument that ends in a backslash. This addresses CVE-2019-1350. Signed-off-by: Johannes Schindelin <>
2019-12-05is_ntfs_dotgit(): speed it upJohannes Schindelin
Previously, this function was written without focusing on speed, intending to make reviewing the code as easy as possible, to avoid any bugs in this critical code. Turns out: we can do much better on both accounts. With this patch, we make it as fast as this developer can make it go: - We avoid the call to `is_dir_sep()` and make all the character comparisons explicit. - We avoid the cost of calling `strncasecmp()` and unroll the test for `.git` and `git~1`, not even using `tolower()` because it is faster to compare against two constant values. - We look for `.git` and `.git~1` first thing, and return early if not found. - We also avoid calling a separate function for detecting chains of spaces and periods. Each of these improvements has a noticeable impact on the speed of `is_ntfs_dotgit()`. Signed-off-by: Johannes Schindelin <>
2019-12-05path: safeguard `.git` against NTFS Alternate Streams AccessesJohannes Schindelin
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: Reported-by: Nicolas Joly <> Signed-off-by: Johannes Schindelin <>
2019-12-05is_ntfs_dotgit(): only verify the leading segmentJohannes Schindelin
The config setting `core.protectNTFS` is specifically designed to work not only on Windows, but anywhere, to allow for repositories hosted on, say, Linux servers to be protected against NTFS-specific attack vectors. As a consequence, `is_ntfs_dotgit()` manually splits backslash-separated paths (but does not do the same for paths separated by forward slashes), under the assumption that the backslash might not be a valid directory separator on the _current_ Operating System. However, the two callers, `verify_path()` and `fsck_tree()`, are supposed to feed only individual path segments to the `is_ntfs_dotgit()` function. This causes a lot of duplicate scanning (and very inefficient scanning, too, as the inner loop of `is_ntfs_dotgit()` was optimized for readability rather than for speed. Let's simplify the design of `is_ntfs_dotgit()` by putting the burden of splitting the paths by backslashes as directory separators on the callers of said function. Consequently, the `verify_path()` function, which already splits the path by directory separators, now treats backslashes as directory separators _explicitly_ when `core.protectNTFS` is turned on, even on platforms where the backslash is _not_ a directory separator. Note that we have to repeat some code in `verify_path()`: if the backslash is not a directory separator on the current Operating System, we want to allow file names like `\`, but we _do_ want to disallow paths that are clearly intended to cause harm when the repository is cloned on Windows. The `fsck_tree()` function (the other caller of `is_ntfs_dotgit()`) now needs to look for backslashes in tree entries' names specifically when `core.protectNTFS` is turned on. While it would be tempting to completely disallow backslashes in that case (much like `fsck` reports names containing forward slashes as "full paths"), this would be overzealous: when `core.protectNTFS` is turned on in a non-Windows setup, backslashes are perfectly valid characters in file names while we _still_ want to disallow tree entries that are clearly designed to exploit NTFS-specific behavior. This simplification will make subsequent changes easier to implement, such as turning `core.protectNTFS` on by default (not only on Windows) or protecting against attack vectors involving NTFS Alternate Data Streams. Incidentally, this change allows for catching malicious repositories that contain tree entries of the form `dir\.gitmodules` already on the server side rather than only on the client side (and previously only on Windows): in contrast to `is_ntfs_dotgit()`, the `is_ntfs_dotgitmodules()` function already expects the caller to split the paths by directory separators. Signed-off-by: Johannes Schindelin <>
2019-12-05test-path-utils: offer to run a protectNTFS/protectHFS benchmarkGarima Singh
In preparation to flipping the default on `core.protectNTFS`, let's have some way to measure the speed impact of this config setting reliably (and for comparison, the `core.protectHFS` config setting). For now, this is a manual performance benchmark: ./t/helper/test-path-utils protect_ntfs_hfs [arguments...] where the arguments are an optional number of file names to test with, optionally followed by minimum and maximum length of the random file names. The default values are one million, 3 and 20, respectively. Just like `sqrti()` in `bisect.c`, we introduce a very simple function to approximation the square root of a given value, in order to avoid having to introduce the first user of `<math.h>` in Git's source code. Note: this is _not_ implemented as a Unix shell script in t/perf/ because we really care about _very_ precise timings here, and Unix shell scripts are simply unsuited for precise and consistent benchmarking. Signed-off-by: Garima Singh <> Signed-off-by: Johannes Schindelin <>
2019-12-04Merge branch 'prevent-name-squatting-on-windows'Johannes Schindelin
This patch series fixes an issue where Git could formerly have been tricked into creating a `.git` file with an unexpected (and therefore unprotected) NTFS short name. Incidentally, it also fixes an issue where a tree entry containing a backslash could be tricked into following a symbolic link, i.e. Git could be tricked into writing files outside the worktree. Signed-off-by: Johannes Schindelin <>
2019-12-04Merge branch 'jk/fast-import-unsafe'Johannes Schindelin
The `--export-marks` option of `git fast-import` is exposed also via the in-stream command `feature export-marks=...` and it allows overwriting arbitrary paths. This topic branch prevents the in-stream version, to prevent arbitrary file accesses by `git fast-import` streams coming from untrusted sources (e.g. in remote helpers that are based on `git fast-import`). This fixes CVE-2019-1348. Signed-off-by: Johannes Schindelin <>
2019-12-04path.c: document the purpose of `is_ntfs_dotgit()`Johannes Schindelin
Previously, this function was completely undocumented. It is worth, though, to explain what is going on, as it is not really obvious at all. Suggested-by: Garima Singh <> Signed-off-by: Johannes Schindelin <>
2019-12-04mingw: disallow backslash characters in tree objects' file namesJohannes Schindelin
The backslash character is not a valid part of a file name on Windows. Hence it is dangerous to allow writing files that were unpacked from tree objects, when the stored file name contains a backslash character: it will be misinterpreted as directory separator. This not only causes ambiguity when a tree contains a blob `a\b` and a tree `a` that contains a blob `b`, but it also can be used as part of an attack vector to side-step the careful protections against writing into the `.git/` directory during a clone of a maliciously-crafted repository. Let's prevent that, addressing CVE-2019-1354. Note: we guard against backslash characters in tree objects' file names _only_ on Windows (because on other platforms, even on those where NTFS volumes can be mounted, the backslash character is _not_ a directory separator), and _only_ when `core.protectNTFS = true` (because users might need to generate tree objects for other platforms, of course without touching the worktree, e.g. using `git update-index --cacheinfo`). Signed-off-by: Johannes Schindelin <>
2019-12-04clone --recurse-submodules: prevent name squatting on WindowsJohannes Schindelin
In addition to preventing `.git` from being tracked by Git, on Windows we also have to prevent `git~1` from being tracked, as the default NTFS short name (also known as the "8.3 filename") for the file name `.git` is `git~1`, otherwise it would be possible for malicious repositories to write directly into the `.git/` directory, e.g. a `post-checkout` hook that would then be executed _during_ a recursive clone. When we implemented appropriate protections in 2b4c6efc821 (read-cache: optionally disallow NTFS .git variants, 2014-12-16), we had analyzed carefully that the `.git` directory or file would be guaranteed to be the first directory entry to be written. Otherwise it would be possible e.g. for a file named `..git` to be assigned the short name `git~1` and subsequently, the short name generated for `.git` would be `git~2`. Or `git~3`. Or even `~9999999` (for a detailed explanation of the lengths we have to go to protect `.gitmodules`, see the commit message of e7cb0b4455c (is_ntfs_dotgit: match other .git files, 2018-05-11)). However, by exploiting two issues (that will be addressed in a related patch series close by), it is currently possible to clone a submodule into a non-empty directory: - On Windows, file names cannot end in a space or a period (for historical reasons: the period separating the base name from the file extension was not actually written to disk, and the base name/file extension was space-padded to the full 8/3 characters, respectively). Helpfully, when creating a directory under the name, say, `sub.`, that trailing period is trimmed automatically and the actual name on disk is `sub`. This means that while Git thinks that the submodule names `sub` and `sub.` are different, they both access `.git/modules/sub/`. - While the backslash character is a valid file name character on Linux, it is not so on Windows. As Git tries to be cross-platform, it therefore allows backslash characters in the file names stored in tree objects. Which means that it is totally possible that a submodule `c` sits next to a file `c\..git`, and on Windows, during recursive clone a file called `..git` will be written into `c/`, of course _before_ the submodule is cloned. Note that the actual exploit is not quite as simple as having a submodule `c` next to a file `c\..git`, as we have to make sure that the directory `.git/modules/b` already exists when the submodule is checked out, otherwise a different code path is taken in `module_clone()` that does _not_ allow a non-empty submodule directory to exist already. Even if we will address both issues nearby (the next commit will disallow backslash characters in tree entries' file names on Windows, and another patch will disallow creating directories/files with trailing spaces or periods), it is a wise idea to defend in depth against this sort of attack vector: when submodules are cloned recursively, we now _require_ the directory to be empty, addressing CVE-2019-1349. Note: the code path we patch is shared with the code path of `git submodule update --init`, which must not expect, in general, that the directory is empty. Hence we have to introduce the new option `--force-init` and hand it all the way down from `git submodule` to the actual `git submodule--helper` process that performs the initial clone. Reported-by: Nicolas Joly <> Signed-off-by: Johannes Schindelin <>
2019-12-04fast-import: disallow "feature import-marks" by defaultJeff King
As with export-marks in the previous commit, import-marks can access the filesystem. This is significantly less dangerous than export-marks because it only involves reading from arbitrary paths, rather than writing them. However, it could still be surprising and have security implications (e.g., exfiltrating data from a service that accepts fast-import streams). Let's lump it (and its "if-exists" counterpart) in with export-marks, and enable the in-stream version only if --allow-unsafe-features is set. Signed-off-by: Jeff King <>
2019-12-04fast-import: disallow "feature export-marks" by defaultJeff King
The fast-import stream command "feature export-marks=<path>" lets the stream write marks to an arbitrary path. This may be surprising if you are running fast-import against an untrusted input (which otherwise cannot do anything except update Git objects and refs). Let's disallow the use of this feature by default, and provide a command-line option to re-enable it (you can always just use the command-line --export-marks as well, but the in-stream version provides an easy way for exporters to control the process). This is a backwards-incompatible change, since the default is flipping to the new, safer behavior. However, since the main users of the in-stream versions would be import/export-based remote helpers, and since we trust remote helpers already (which are already running arbitrary code), we'll pass the new option by default when reading a remote helper's stream. This should minimize the impact. Note that the implementation isn't totally simple, as we have to work around the fact that fast-import doesn't parse its command-line options until after it has read any "feature" lines from the stream. This is how it lets command-line options override in-stream. But in our case, it's important to parse the new --allow-unsafe-features first. There are three options for resolving this: 1. Do a separate "early" pass over the options. This is easy for us to do because there are no command-line options that allow the "unstuck" form (so there's no chance of us mistaking an argument for an option), though it does introduce a risk of incorrect parsing later (e.g,. if we convert to parse-options). 2. Move the option parsing phase back to the start of the program, but teach the stream-reading code never to override an existing value. This is tricky, because stream "feature" lines override each other (meaning we'd have to start tracking the source for every option). 3. Accept that we might parse a "feature export-marks" line that is forbidden, as long we don't _act_ on it until after we've parsed the command line options. This would, in fact, work with the current code, but only because the previous patch fixed the export-marks parser to avoid touching the filesystem. So while it works, it does carry risk of somebody getting it wrong in the future in a rather subtle and unsafe way. I've gone with option (1) here as simple, safe, and unlikely to cause regressions. This fixes CVE-2019-1348. Signed-off-by: Jeff King <>
2019-12-04fast-import: delay creating leading directories for export-marksJeff King
When we parse the --export-marks option, we don't immediately open the file, but we do create any leading directories. This can be especially confusing when a command-line option overrides an in-stream one, in which case we'd create the leading directory for the in-stream file, even though we never actually write the file. Let's instead create the directories just before opening the file, which means we'll create only useful directories. Note that this could change the handling of relative paths if we chdir() in between, but we don't actually do so; the only permanent chdir is from setup_git_directory() which runs before either code path (potentially we should take the pre-setup dir into account to avoid surprising the user, but that's an orthogonal change). The test just adapts the existing "override" test to use paths with leading directories. This checks both that the correct directory is created (which worked before but was not tested), and that the overridden one is not (our new fix here). While we're here, let's also check the error result of safe_create_leading_directories(). We'd presumably notice any failure immediately after when we try to open the file itself, but we can give a more specific error message in this case. Signed-off-by: Jeff King <>
2019-12-04fast-import: stop creating leading directories for import-marksJeff King
When asked to import marks from "subdir/file.marks", we create the leading directory "subdir" if it doesn't exist. This makes no sense for importing marks, where we only ever open the path for reading. Most of the time this would be a noop, since if the marks file exists, then the leading directories exist, too. But if it doesn't (e.g., because --import-marks-if-exists was used), then we'd create the useless directory. This dates back to 580d5f83e7 (fast-import: always create marks_file directories, 2010-03-29). Even then it was useless, so it seems to have been added in error alongside the --export-marks case (which _is_ helpful). Signed-off-by: Jeff King <>
2019-12-04fast-import: tighten parsing of boolean command line optionsJeff King
We parse options like "--max-pack-size=" using skip_prefix(), which makes sense to get at the bytes after the "=". However, we also parse "--quiet" and "--stats" with skip_prefix(), which allows things like "--quiet-nonsense" to behave like "--quiet". This was a mistaken conversion in 0f6927c229 (fast-import: put option parsing code in separate functions, 2009-12-04). Let's tighten this to an exact match, which was the original intent. Signed-off-by: Jeff King <>
2019-12-04t9300: create marks files for double-import-marks testJeff King
Our tests confirm that providing two "import-marks" options in a fast-import stream is an error. However, the invoked command would fail even without covering this case, because the marks files themselves do not actually exist. Let's create the files to make sure we fail for the right reason (we actually do, because the option parsing happens before we open anything, but this future-proofs our test). Signed-off-by: Jeff King <>
2019-12-04t9300: drop some useless uses of catJeff King
These waste a process, and make the line longer than it needs to be. Signed-off-by: Jeff King <>
2018-09-27Git 2.15.3v2.15.3Junio C Hamano
Signed-off-by: Junio C Hamano <>
2018-09-27Sync with Git 2.14.4Junio C Hamano
* maint-2.14: Git 2.14.5 submodule-config: ban submodule paths that start with a dash submodule-config: ban submodule urls that start with dash submodule--helper: use "--" to signal end of clone options
2018-09-27Git 2.14.5v2.14.5Junio C Hamano
Signed-off-by: Junio C Hamano <>
2018-09-27submodule-config: ban submodule paths that start with a dashJeff King
We recently banned submodule urls that look like command-line options. This is the matching change to ban leading-dash paths. As with the urls, this should not break any use cases that currently work. Even with our "--" separator passed to git-clone, gets confused. Without the code portion of this patch, the clone of "-sub" added in t7417 would yield results like: /path/to/git-submodule: 410: cd: Illegal option -s /path/to/git-submodule: 417: cd: Illegal option -s /path/to/git-submodule: 410: cd: Illegal option -s /path/to/git-submodule: 417: cd: Illegal option -s Fetched in submodule path '-sub', but it did not contain b56243f8f4eb91b2f1f8109452e659f14dd3fbe4. Direct fetching of that commit failed. Moreover, naively adding such a submodule doesn't work: $ git submodule add $url -sub The following path is ignored by one of your .gitignore files: -sub even though there is no such ignore pattern (the test script hacks around this with a well-placed "git mv"). Unlike leading-dash urls, though, it's possible that such a path _could_ be useful if we eventually made it work. So this commit should be seen not as recommending a particular policy, but rather temporarily closing off a broken and possibly dangerous code-path. We may revisit this decision later. There are two minor differences to the tests in t7416 (that covered urls): 1. We don't have a "./-sub" escape hatch to make this work, since the submodule code expects to be able to match canonical index names to the path field (so you are free to add submodule config with that path, but we would never actually use it, since an index entry would never start with "./"). 2. After this patch, cloning actually succeeds. Since we ignore the submodule.*.path value, we fail to find a config stanza for our submodule at all, and simply treat it as inactive. We still check for the "ignoring" message. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2018-09-27submodule-config: ban submodule urls that start with dashJeff King
The previous commit taught the submodule code to invoke our "git clone $url $path" with a "--" separator so that we aren't confused by urls or paths that start with dashes. However, that's just one code path. It's not clear if there are others, and it would be an easy mistake to add one in the future. Moreover, even with the fix in the previous commit, it's quite hard to actually do anything useful with such an entry. Any url starting with a dash must fall into one of three categories: - it's meant as a file url, like "-path". But then any clone is not going to have the matching path, since it's by definition relative inside the newly created clone. If you spell it as "./-path", the submodule code sees the "/" and translates this to an absolute path, so it at least works (assuming the receiver has the same filesystem layout as you). But that trick does not apply for a bare "-path". - it's meant as an ssh url, like "-host:path". But this already doesn't work, as we explicitly disallow ssh hostnames that begin with a dash (to avoid option injection against ssh). - it's a remote-helper scheme, like "-scheme::data". This _could_ work if the receiver bends over backwards and creates a funny-named helper like "git-remote--scheme". But normally there would not be any helper that matches. Since such a url does not work today and is not likely to do anything useful in the future, let's simply disallow them entirely. That protects the existing "git clone" path (in a belt-and-suspenders way), along with any others that might exist. Our tests cover two cases: 1. A file url with "./" continues to work, showing that there's an escape hatch for people with truly silly repo names. 2. A url starting with "-" is rejected. Note that we expect case (2) to fail, but it would have done so even without this commit, for the reasons given above. So instead of just expecting failure, let's also check for the magic word "ignoring" on stderr. That lets us know that we failed for the right reason. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2018-09-27submodule--helper: use "--" to signal end of clone optionsJeff King
When we clone a submodule, we call "git clone $url $path". But there's nothing to say that those components can't begin with a dash themselves, confusing git-clone into thinking they're options. Let's pass "--" to make it clear what we expect. There's no test here, because it's actually quite hard to make these names work, even with "git clone" parsing them correctly. And we're going to restrict these cases even further in future commits. So we'll leave off testing until then; this is just the minimal fix to prevent us from doing something stupid with a badly formed entry. Reported-by: joernchen <> Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2018-05-22Git 2.15.2v2.15.2Junio C Hamano
Signed-off-by: Junio C Hamano <>
2018-05-22Sync with Git 2.14.4Junio C Hamano
* maint-2.14: Git 2.14.4 Git 2.13.7 verify_path: disallow symlinks in .gitmodules update-index: stat updated files earlier verify_dotfile: mention case-insensitivity in comment verify_path: drop clever fallthrough skip_prefix: add case-insensitive variant is_{hfs,ntfs}_dotgitmodules: add tests is_ntfs_dotgit: match other .git files is_hfs_dotgit: match other .git files is_ntfs_dotgit: use a size_t for traversing string submodule-config: verify submodule names as paths
2018-05-22Git 2.14.4v2.14.4Junio C Hamano
Signed-off-by: Junio C Hamano <>
2018-05-22Sync with Git 2.13.7Junio C Hamano
* maint-2.13: Git 2.13.7 verify_path: disallow symlinks in .gitmodules update-index: stat updated files earlier verify_dotfile: mention case-insensitivity in comment verify_path: drop clever fallthrough skip_prefix: add case-insensitive variant is_{hfs,ntfs}_dotgitmodules: add tests is_ntfs_dotgit: match other .git files is_hfs_dotgit: match other .git files is_ntfs_dotgit: use a size_t for traversing string submodule-config: verify submodule names as paths
2018-05-22Git 2.13.7v2.13.7Junio C Hamano
Signed-off-by: Junio C Hamano <>