* 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

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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, git-submodule.sh 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: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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: Njoernchen <joernchen@phenoelit.de>
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

* 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

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

* 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

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

* jk/submodule-fix-loose:
  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

There are a few reasons it's not a good idea to make
.gitmodules a symlink, including:

  1. It won't be portable to systems without symlinks.

  2. It may behave inconsistently, since Git may look at
     this file in the index or a tree without bothering to
     resolve any symbolic links. We don't do this _yet_, but
     the config infrastructure is there and it's planned for
     the future.

With some clever code, we could make (2) work. And some
people may not care about (1) if they only work on one
platform. But there are a few security reasons to simply
disallow it:

  a. A symlinked .gitmodules file may circumvent any fsck
     checks of the content.

  b. Git may read and write from the on-disk file without
     sanity checking the symlink target. So for example, if
     you link ".gitmodules" to "../oops" and run "git
     submodule add", we'll write to the file "oops" outside
     the repository.

Again, both of those are problems that _could_ be solved
with sufficient code, but given the complications in (1) and
(2), we're better off just outlawing it explicitly.

Note the slightly tricky call to verify_path() in
update-index's update_one(). There we may not have a mode if
we're not updating from the filesystem (e.g., we might just
be removing the file). Passing "0" as the mode there works
fine; since it's not a symlink, we'll just skip the extra
checks.
Signed-off-by: NJeff King <peff@peff.net>

In the update_one(), we check verify_path() on the proposed
path before doing anything else. In preparation for having
verify_path() look at the file mode, let's stat the file
earlier, so we can check the mode accurately.

This is made a bit trickier by the fact that this function
only does an lstat in a few code paths (the ones that flow
down through process_path()). So we can speculatively do the
lstat() here and pass the results down, and just use a dummy
mode for cases where we won't actually be updating the index
from the filesystem.
Signed-off-by: NJeff King <peff@peff.net>

We're more restrictive than we need to be in matching ".GIT"
on case-sensitive filesystems; let's make a note that this
is intentional.
Signed-off-by: NJeff King <peff@peff.net>

We check ".git" and ".." in the same switch statement, and
fall through the cases to share the end-of-component check.
While this saves us a line or two, it makes modifying the
function much harder. Let's just write it out.
Signed-off-by: NJeff King <peff@peff.net>

We have the convenient skip_prefix() helper, but if you want
to do case-insensitive matching, you're stuck doing it by
hand. We could add an extra parameter to the function to
let callers ask for this, but the function is small and
somewhat performance-critical. Let's just re-implement it
for the case-insensitive version.
Signed-off-by: NJeff King <peff@peff.net>

This tests primarily for NTFS issues, but also adds one example of an
HFS+ issue.

Thanks go to Congyi Wu for coming up with the list of examples where
NTFS would possibly equate the filename with `.gitmodules`.
Signed-off-by: NJohannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: NJeff King <peff@peff.net>

When we started to catch NTFS short names that clash with .git, we only
looked for GIT~1. This is sufficient because we only ever clone into an
empty directory, so .git is guaranteed to be the first subdirectory or
file in that directory.

However, even with a fresh clone, .gitmodules is *not* necessarily the
first file to be written that would want the NTFS short name GITMOD~1: a
malicious repository can add .gitmodul0000 and friends, which sorts
before `.gitmodules` and is therefore checked out *first*. For that
reason, we have to test not only for ~1 short names, but for others,
too.

It's hard to just adapt the existing checks in is_ntfs_dotgit(): since
Windows 2000 (i.e., in all Windows versions still supported by Git),
NTFS short names are only generated in the <prefix>~<number> form up to
number 4. After that, a *different* prefix is used, calculated from the
long file name using an undocumented, but stable algorithm.

For example, the short name of .gitmodules would be GITMOD~1, but if it
is taken, and all of ~2, ~3 and ~4 are taken, too, the short name
GI7EBA~1 will be used. From there, collisions are handled by
incrementing the number, shortening the prefix as needed (until ~9999999
is reached, in which case NTFS will not allow the file to be created).

We'd also want to handle .gitignore and .gitattributes, which suffer
from a similar problem, using the fall-back short names GI250A~1 and
GI7D29~1, respectively.

To accommodate for that, we could reimplement the hashing algorithm, but
it is just safer and simpler to provide the known prefixes. This
algorithm has been reverse-engineered and described at
https://usn.pw/blog/gen/2015/06/09/filenames/, which is defunct but
still available via https://web.archive.org/.

These can be recomputed by running the following Perl script:

-- snip --
use warnings;
use strict;

sub compute_short_name_hash ($) {
        my $checksum = 0;
        foreach (split('', $_[0])) {
                $checksum = ($checksum * 0x25 + ord($_)) & 0xffff;
        }

        $checksum = ($checksum * 314159269) & 0xffffffff;
        $checksum = 1 + (~$checksum & 0x7fffffff) if ($checksum & 0x80000000);
        $checksum -= (($checksum * 1152921497) >> 60) * 1000000007;

        return scalar reverse sprintf("%x", $checksum & 0xffff);
}

print compute_short_name_hash($ARGV[0]);
-- snap --

E.g., running that with the argument ".gitignore" will
result in "250a" (which then becomes "gi250a" in the code).
Signed-off-by: NJohannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: NJeff King <peff@peff.net>

Both verify_path() and fsck match ".git", ".GIT", and other
variants specific to HFS+. Let's allow matching other
special files like ".gitmodules", which we'll later use to
enforce extra restrictions via verify_path() and fsck.
Signed-off-by: NJeff King <peff@peff.net>

We walk through the "name" string using an int, which can
wrap to a negative value and cause us to read random memory
before our array (e.g., by creating a tree with a name >2GB,
since "int" is still 32 bits even on most 64-bit platforms).
Worse, this is easy to trigger during the fsck_tree() check,
which is supposed to be protecting us from malicious
garbage.

Note one bit of trickiness in the existing code: we
sometimes assign -1 to "len" at the end of the loop, and
then rely on the "len++" in the for-loop's increment to take
it back to 0. This is still legal with a size_t, since
assigning -1 will turn into SIZE_MAX, which then wraps
around to 0 on increment.
Signed-off-by: NJeff King <peff@peff.net>

Submodule "names" come from the untrusted .gitmodules file,
but we blindly append them to $GIT_DIR/modules to create our
on-disk repo paths. This means you can do bad things by
putting "../" into the name (among other things).

Let's sanity-check these names to avoid building a path that
can be exploited. There are two main decisions:

  1. What should the allowed syntax be?

     It's tempting to reuse verify_path(), since submodule
     names typically come from in-repo paths. But there are
     two reasons not to:

       a. It's technically more strict than what we need, as
          we really care only about breaking out of the
          $GIT_DIR/modules/ hierarchy.  E.g., having a
          submodule named "foo/.git" isn't actually
          dangerous, and it's possible that somebody has
          manually given such a funny name.

       b. Since we'll eventually use this checking logic in
          fsck to prevent downstream repositories, it should
          be consistent across platforms. Because
          verify_path() relies on is_dir_sep(), it wouldn't
          block "foo\..\bar" on a non-Windows machine.

  2. Where should we enforce it? These days most of the
     .gitmodules reads go through submodule-config.c, so
     I've put it there in the reading step. That should
     cover all of the C code.

     We also construct the name for "git submodule add"
     inside the git-submodule.sh script. This is probably
     not a big deal for security since the name is coming
     from the user anyway, but it would be polite to remind
     them if the name they pick is invalid (and we need to
     expose the name-checker to the shell anyway for our
     test scripts).

     This patch issues a warning when reading .gitmodules
     and just ignores the related config entry completely.
     This will generally end up producing a sensible error,
     as it works the same as a .gitmodules file which is
     missing a submodule entry (so "submodule update" will
     barf, but "git clone --recurse-submodules" will print
     an error but not abort the clone.

     There is one minor oddity, which is that we print the
     warning once per malformed config key (since that's how
     the config subsystem gives us the entries). So in the
     new test, for example, the user would see three
     warnings. That's OK, since the intent is that this case
     should never come up outside of malicious repositories
     (and then it might even benefit the user to see the
     message multiple times).

Credit for finding this vulnerability and the proof of
concept from which the test script was adapted goes to
Etienne Stalmans.
Signed-off-by: NJeff King <peff@peff.net>

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Clarify and enhance documentation for "merge-base --fork-point", as
it was clear what it computed but not why/what for.

* jc/merge-base-fork-point-doc:
  merge-base --fork-point doc: clarify the example and failure modes

A few scripts (both in production and tests) incorrectly redirected
their error output.  These have been corrected.

* tz/redirect-fix:
  rebase: fix stderr redirect in apply_autostash()
  t/lib-gpg: fix gpgconf stderr redirect to /dev/null

"git notes" sent its error message to its standard output stream,
which was corrected.

* tz/notes-error-to-stderr:
  notes: send "Automatic notes merge failed" messages to stderr

The three-way merge performed by "git cherry-pick" was confused
when a new submodule was added in the meantime, which has been
fixed (or "papered over").

* sb/test-cherry-pick-submodule-getting-in-a-way:
  merge-recursive: handle addition of submodule on our side of history
  t/3512: demonstrate unrelated submodule/file conflict as cherry-pick failure

The sequencer machinery (used by "git cherry-pick A..B", and "git
rebase -i", among other things) would have lost a commit if stopped
due to an unlockable index file, which has been fixed.

* pw/sequencer-recover-from-unlockable-index:
  sequencer: reschedule pick if index can't be locked

"git apply --inaccurate-eof" when used with "--ignore-space-change"
triggered an internal sanity check, which has been fixed.

* rs/apply-inaccurate-eof-with-incomplete-line:
  apply: update line lengths for --inaccurate-eof

Command line completion (in contrib/) has been taught about the
"--copy" option of "git branch".

* tz/complete-branch-copy:
  completion: add '--copy' option to 'git branch'

When "git rebase" prepared an mailbox of changes and fed it to "git
am" to replay them, it was confused when a stray "From " happened
to be in the log message of one of the replayed changes.  This has
been corrected.

* ew/rebase-mboxrd:
  rebase: use mboxrd format to avoid split errors

Code clean-up.

* sd/branch-copy:
  config: avoid "write_in_full(fd, buf, len) != len" pattern

Contrary to the documentation, "git pull -4/-6 other-args" did not
ask the underlying "git fetch" to go over IPv4/IPv6, which has been
corrected.

* sw/pull-ipv46-passthru:
  pull: pass -4/-6 option to 'git fetch'

The SubmittingPatches document has been converted to produce an
HTML version via AsciiDoc/Asciidoctor.

* bc/submitting-patches-in-asciidoc:
  Documentation: convert SubmittingPatches to AsciiDoc
  Documentation: enable compat-mode for Asciidoctor

Recent update to the refs infrastructure implementation started
rewriting packed-refs file more often than before; this has been
optimized again for most trivial cases.

* mh/avoid-rewriting-packed-refs:
  files-backend: don't rewrite the `packed-refs` file unnecessarily
  t1409: check that `packed-refs` is not rewritten unnecessarily

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

There was a recent semantic mismerge in the codepath to write out a
section of a configuration section, which has been corrected.

* rs/config-write-section-fix:
  config: flip return value of write_section()

We've been waiting long enough, a few more would not hurt ;-)
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Leak fixes.

* ma/reduce-heads-leakfix:
  reduce_heads: fix memory leaks
  builtin/merge-base: free commit lists

Leak fixes.

* ma/bisect-leakfix:
  bisect: fix memory leak when returning best element
  bisect: fix off-by-one error in `best_bisection_sorted()`
  bisect: fix memory leak in `find_bisection()`
  bisect: change calling-convention of `find_bisection()`

A fix for an ancient bug in "git apply --ignore-space-change" codepath.

* rs/apply-fuzzy-match-fix:
  apply: avoid out-of-bounds access in fuzzy_matchlines()