Merge branch 'icasefs-symlink-confusion'

This topic branch fixes two vulnerabilities:

- Recursive clones on case-insensitive filesystems that support symbolic
  links are susceptible to case confusion that can be exploited to
  execute just-cloned code during the clone operation.

- Repositories can be configured to execute arbitrary code during local
  clones. To address this, the ownership checks introduced in v2.30.3
  are now extended to cover cloning local repositories.

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

5 files changed, 253 insertions, 2 deletions

diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index 502b4bcf9e..2ba219b18b 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh
@@ -1200,6 +1200,34 @@ test_expect_success 'very long name in the index handled sanely' '
 	test $len = 4098
 '
 
+# D/F conflict checking uses an optimization when adding to the end.
+# make sure it does not get confused by `a-` sorting _between_
+# `a` and `a/`.
+test_expect_success 'more update-index D/F conflicts' '
+	# empty the index to make sure our entry is last
+	git read-tree --empty &&
+	cacheinfo=100644,$(test_oid empty_blob) &&
+	git update-index --add --cacheinfo $cacheinfo,path5/a &&
+
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/c/file &&
+
+	# "a-" sorts between "a" and "a/"
+	git update-index --add --cacheinfo $cacheinfo,path5/a- &&
+
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/file &&
+	test_must_fail git update-index --add --cacheinfo $cacheinfo,path5/a/b/c/file &&
+
+	cat >expected <<-\EOF &&
+	path5/a
+	path5/a-
+	EOF
+	git ls-files >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'test_must_fail on a failing git command' '
 	test_must_fail git notacommand
 '
diff --git a/t/t0411-clone-from-partial.sh b/t/t0411-clone-from-partial.sh
new file mode 100755
index 0000000000..b3d6ddc4bc
--- /dev/null
+++ b/t/t0411-clone-from-partial.sh
@@ -0,0 +1,78 @@
+#!/bin/sh
+
+test_description='check that local clone does not fetch from promisor remotes'
+
+. ./test-lib.sh
+
+test_expect_success 'create evil repo' '
+	git init tmp &&
+	test_commit -C tmp a &&
+	git -C tmp config uploadpack.allowfilter 1 &&
+	git clone --filter=blob:none --no-local --no-checkout tmp evil &&
+	rm -rf tmp &&
+
+	git -C evil config remote.origin.uploadpack \"\$TRASH_DIRECTORY/fake-upload-pack\" &&
+	write_script fake-upload-pack <<-\EOF &&
+		echo >&2 "fake-upload-pack running"
+		>"$TRASH_DIRECTORY/script-executed"
+		exit 1
+	EOF
+	export TRASH_DIRECTORY &&
+
+	# empty shallow file disables local clone optimization
+	>evil/.git/shallow
+'
+
+test_expect_success 'local clone must not fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	test_must_fail git clone \
+		--upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
+		evil clone1 2>err &&
+	grep "detected dubious ownership" err &&
+	! grep "fake-upload-pack running" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'clone from file://... must not fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	test_must_fail git clone \
+		--upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
+		"file://$(pwd)/evil" clone2 2>err &&
+	grep "detected dubious ownership" err &&
+	! grep "fake-upload-pack running" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'fetch from file://... must not fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	test_must_fail git fetch \
+		--upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
+		"file://$(pwd)/evil" 2>err &&
+	grep "detected dubious ownership" err &&
+	! grep "fake-upload-pack running" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'pack-objects should fetch from promisor remote and execute script' '
+	rm -f script-executed &&
+	echo "HEAD" | test_must_fail git -C evil pack-objects --revs --stdout >/dev/null 2>err &&
+	grep "fake-upload-pack running" err &&
+	test_path_is_file script-executed
+'
+
+test_expect_success 'clone from promisor remote does not lazy-fetch by default' '
+	rm -f script-executed &&
+	test_must_fail git clone evil no-lazy 2>err &&
+	grep "lazy fetching disabled" err &&
+	test_path_is_missing script-executed
+'
+
+test_expect_success 'promisor lazy-fetching can be re-enabled' '
+	rm -f script-executed &&
+	test_must_fail env GIT_NO_LAZY_FETCH=0 \
+		git clone evil lazy-ok 2>err &&
+	grep "fake-upload-pack running" err &&
+	test_path_is_file script-executed
+'
+
+test_done
diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
index f094e3d7f3..63c24f7f7c 100755
--- a/t/t7406-submodule-update.sh
+++ b/t/t7406-submodule-update.sh
@@ -1179,4 +1179,52 @@ test_expect_success 'submodule update --recursive skip submodules with strategy=
 	test_cmp expect.err actual.err
 '
 
+test_expect_success CASE_INSENSITIVE_FS,SYMLINKS \
+	'submodule paths must not follow symlinks' '
+
+	# This is only needed because we want to run this in a self-contained
+	# test without having to spin up an HTTP server; However, it would not
+	# be needed in a real-world scenario where the submodule is simply
+	# hosted on a public site.
+	test_config_global protocol.file.allow always &&
+
+	# Make sure that Git tries to use symlinks on Windows
+	test_config_global core.symlinks true &&
+
+	tell_tale_path="$PWD/tell.tale" &&
+	git init hook &&
+	(
+		cd hook &&
+		mkdir -p y/hooks &&
+		write_script y/hooks/post-checkout <<-EOF &&
+		echo HOOK-RUN >&2
+		echo hook-run >"$tell_tale_path"
+		EOF
+		git add y/hooks/post-checkout &&
+		test_tick &&
+		git commit -m post-checkout
+	) &&
+
+	hook_repo_path="$(pwd)/hook" &&
+	git init captain &&
+	(
+		cd captain &&
+		git submodule add --name x/y "$hook_repo_path" A/modules/x &&
+		test_tick &&
+		git commit -m add-submodule &&
+
+		printf .git >dotgit.txt &&
+		git hash-object -w --stdin <dotgit.txt >dot-git.hash &&
+		printf "120000 %s 0\ta\n" "$(cat dot-git.hash)" >index.info &&
+		git update-index --index-info <index.info &&
+		test_tick &&
+		git commit -m add-symlink
+	) &&
+
+	test_path_is_missing "$tell_tale_path" &&
+	test_must_fail git clone --recursive captain hooked 2>err &&
+	grep "directory not empty" err &&
+	test_path_is_missing "$tell_tale_path"
+'
+
 test_done
diff --git a/t/t7423-submodule-symlinks.sh b/t/t7423-submodule-symlinks.sh
new file mode 100755
index 0000000000..3d3c7af3ce
--- /dev/null
+++ b/t/t7423-submodule-symlinks.sh
@@ -0,0 +1,67 @@
+#!/bin/sh
+
+test_description='check that submodule operations do not follow symlinks'
+
+. ./test-lib.sh
+
+test_expect_success 'prepare' '
+	git config --global protocol.file.allow always &&
+	test_commit initial &&
+	git init upstream &&
+	test_commit -C upstream upstream submodule_file &&
+	git submodule add ./upstream a/sm &&
+	test_tick &&
+	git commit -m submodule
+'
+
+test_expect_success SYMLINKS 'git submodule update must not create submodule behind symlink' '
+	rm -rf a b &&
+	mkdir b &&
+	ln -s b a &&
+	test_path_is_missing b/sm &&
+	test_must_fail git submodule update &&
+	test_path_is_missing b/sm
+'
+
+test_expect_success SYMLINKS,CASE_INSENSITIVE_FS 'git submodule update must not create submodule behind symlink on case insensitive fs' '
+	rm -rf a b &&
+	mkdir b &&
+	ln -s b A &&
+	test_must_fail git submodule update &&
+	test_path_is_missing b/sm
+'
+
+prepare_symlink_to_repo() {
+	rm -rf a &&
+	mkdir a &&
+	git init a/target &&
+	git -C a/target fetch ../../upstream &&
+	ln -s target a/sm
+}
+
+test_expect_success SYMLINKS 'git restore --recurse-submodules must not be confused by a symlink' '
+	prepare_symlink_to_repo &&
+	test_must_fail git restore --recurse-submodules a/sm &&
+	test_path_is_missing a/sm/submodule_file &&
+	test_path_is_dir a/target/.git &&
+	test_path_is_missing a/target/submodule_file
+'
+
+test_expect_success SYMLINKS 'git restore --recurse-submodules must not migrate git dir of symlinked repo' '
+	prepare_symlink_to_repo &&
+	rm -rf .git/modules &&
+	test_must_fail git restore --recurse-submodules a/sm &&
+	test_path_is_dir a/target/.git &&
+	test_path_is_missing .git/modules/a/sm &&
+	test_path_is_missing a/target/submodule_file
+'
+
+test_expect_success SYMLINKS 'git checkout -f --recurse-submodules must not migrate git dir of symlinked repo when removing submodule' '
+	prepare_symlink_to_repo &&
+	rm -rf .git/modules &&
+	test_must_fail git checkout -f --recurse-submodules initial &&
+	test_path_is_dir a/target/.git &&
+	test_path_is_missing .git/modules/a/sm
+'
+
+test_done
diff --git a/t/t7450-bad-git-dotfiles.sh b/t/t7450-bad-git-dotfiles.sh
index ba1f569bcb..8f94129e74 100755
--- a/t/t7450-bad-git-dotfiles.sh
+++ b/t/t7450-bad-git-dotfiles.sh
@@ -292,7 +292,7 @@ test_expect_success WINDOWS 'prevent git~1 squatting on Windows' '
 	fi
 '
 
-test_expect_success 'git dirs of sibling submodules must not be nested' '
+test_expect_success 'setup submodules with nested git dirs' '
 	git init nested &&
 	test_commit -C nested nested &&
 	(
@@ -310,9 +310,39 @@ test_expect_success 'git dirs of sibling submodules must not be nested' '
 		git add .gitmodules thing1 thing2 &&
 		test_tick &&
 		git commit -m nested
-	) &&
+	)
+'
+
+test_expect_success 'git dirs of sibling submodules must not be nested' '
 	test_must_fail git clone --recurse-submodules nested clone 2>err &&
 	test_i18ngrep "is inside git dir" err
 '
 
+test_expect_success 'submodule git dir nesting detection must work with parallel cloning' '
+	test_must_fail git clone --recurse-submodules --jobs=2 nested clone_parallel 2>err &&
+	cat err &&
+	grep -E "(already exists|is inside git dir|not a git repository)" err &&
+	{
+		test_path_is_missing .git/modules/hippo/HEAD ||
+		test_path_is_missing .git/modules/hippo/hooks/HEAD
+	}
+'
+
+test_expect_success 'checkout -f --recurse-submodules must not use a nested gitdir' '
+	git clone nested nested_checkout &&
+	(
+		cd nested_checkout &&
+		git submodule init &&
+		git submodule update thing1 &&
+		mkdir -p .git/modules/hippo/hooks/refs &&
+		mkdir -p .git/modules/hippo/hooks/objects/info &&
+		echo "../../../../objects" >.git/modules/hippo/hooks/objects/info/alternates &&
+		echo "ref: refs/heads/master" >.git/modules/hippo/hooks/HEAD
+	) &&
+	test_must_fail git -C nested_checkout checkout -f --recurse-submodules HEAD 2>err &&
+	cat err &&
+	grep "is inside git dir" err &&
+	test_path_is_missing nested_checkout/thing2/.git
+'
+
 test_done