Sync with 2.35.7

* maint-2.35:
  Git 2.35.7
  Git 2.34.7
  http: support CURLOPT_PROTOCOLS_STR
  http: prefer CURLOPT_SEEKFUNCTION to CURLOPT_IOCTLFUNCTION
  http-push: prefer CURLOPT_UPLOAD to CURLOPT_PUT
  Git 2.33.7
  Git 2.32.6
  Git 2.31.7
  Git 2.30.8
  apply: fix writing behind newly created symbolic links
  dir-iterator: prevent top-level symlinks without FOLLOW_SYMLINKS
  clone: delay picking a transport until after get_repo_path()
  t5619: demonstrate clone_local() with ambiguous transport

Documentation/RelNotes/2.30.8.txt

@@ -0,0 +1,52 @@
+Git v2.30.8 Release Notes
+=========================
+
+This release addresses the security issues CVE-2023-22490 and
+CVE-2023-23946.
+
+
+Fixes since v2.30.7
+-------------------
+
+ * CVE-2023-22490:
+
+   Using a specially-crafted repository, Git can be tricked into using
+   its local clone optimization even when using a non-local transport.
+   Though Git will abort local clones whose source $GIT_DIR/objects
+   directory contains symbolic links (c.f., CVE-2022-39253), the objects
+   directory itself may still be a symbolic link.
+
+   These two may be combined to include arbitrary files based on known
+   paths on the victim's filesystem within the malicious repository's
+   working copy, allowing for data exfiltration in a similar manner as
+   CVE-2022-39253.
+
+ * CVE-2023-23946:
+
+   By feeding a crafted input to "git apply", a path outside the
+   working tree can be overwritten as the user who is running "git
+   apply".
+
+ * A mismatched type in `attr.c::read_attr_from_index()` which could
+   cause Git to errantly reject attributes on Windows and 32-bit Linux
+   has been corrected.
+
+Credit for finding CVE-2023-22490 goes to yvvdwf, and the fix was
+developed by Taylor Blau, with additional help from others on the
+Git security mailing list.
+
+Credit for finding CVE-2023-23946 goes to Joern Schneeweisz, and the
+fix was developed by Patrick Steinhardt.
+
+
+Johannes Schindelin (1):
+      attr: adjust a mismatched data type
+
+Patrick Steinhardt (1):
+      apply: fix writing behind newly created symbolic links
+
+Taylor Blau (3):
+      t5619: demonstrate clone_local() with ambiguous transport
+      clone: delay picking a transport until after get_repo_path()
+      dir-iterator: prevent top-level symlinks without FOLLOW_SYMLINKS
+

Documentation/RelNotes/2.31.7.txt

@@ -0,0 +1,6 @@
+Git v2.31.7 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.30.8 to
+address the security issues CVE-2023-22490 and CVE-2023-23946;
+see the release notes for that version for details.

Documentation/RelNotes/2.32.6.txt

@@ -0,0 +1,6 @@
+Git v2.32.6 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.30.8 and v2.31.7
+to address the security issues CVE-2023-22490 and CVE-2023-23946;
+see the release notes for these versions for details.

Documentation/RelNotes/2.33.7.txt

@@ -0,0 +1,7 @@
+Git v2.33.7 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.30.8, v2.31.7
+and v2.32.6 to address the security issues CVE-2023-22490 and
+CVE-2023-23946; see the release notes for these versions for
+details.

Documentation/RelNotes/2.34.7.txt

@@ -0,0 +1,7 @@
+Git v2.34.7 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.30.8, v2.31.7,
+v2.32.6 and v2.33.7 to address the security issues CVE-2023-22490
+and CVE-2023-23946; see the release notes for these versions
+for details.

Documentation/RelNotes/2.35.7.txt

@@ -0,0 +1,7 @@
+Git v2.35.7 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.30.8, v2.31.7,
+v2.32.6, v2.33.7 and v2.34.7 to address the security issues
+CVE-2023-22490 and CVE-2023-23946; see the release notes for
+these versions for details.

INSTALL

@@ -144,7 +144,7 @@ Issues of note:
 	  not need that functionality, use NO_CURL to build without
 	  it.
 
-	  Git requires version "7.19.4" or later of "libcurl" to build
+	  Git requires version "7.19.5" or later of "libcurl" to build
 	  without NO_CURL. This version requirement may be bumped in
 	  the future.
 

apply.c

@@ -4408,6 +4408,33 @@ static int create_one_file(struct apply_state *state,
 	if (state->cached)
 		return 0;
 
+	/*
+	 * We already try to detect whether files are beyond a symlink in our
+	 * up-front checks. But in the case where symlinks are created by any
+	 * of the intermediate hunks it can happen that our up-front checks
+	 * didn't yet see the symlink, but at the point of arriving here there
+	 * in fact is one. We thus repeat the check for symlinks here.
+	 *
+	 * Note that this does not make the up-front check obsolete as the
+	 * failure mode is different:
+	 *
+	 * - The up-front checks cause us to abort before we have written
+	 *   anything into the working directory. So when we exit this way the
+	 *   working directory remains clean.
+	 *
+	 * - The checks here happen in the middle of the action where we have
+	 *   already started to apply the patch. The end result will be a dirty
+	 *   working directory.
+	 *
+	 * Ideally, we should update the up-front checks to catch what would
+	 * happen when we apply the patch before we damage the working tree.
+	 * We have all the information necessary to do so.  But for now, as a
+	 * part of embargoed security work, having this check would serve as a
+	 * reasonable first step.
+	 */
+	if (path_is_beyond_symlink(state, path))
+		return error(_("affected file '%s' is beyond a symbolic link"), path);
+
 	res = try_create_file(state, path, mode, buf, size);
 	if (res < 0)
 		return -1;

builtin/clone.c

@@ -1150,10 +1150,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	refspec_appendf(&remote->fetch, "+%s*:%s*", src_ref_prefix,
 			branch_top.buf);
 
-	transport = transport_get(remote, remote->url[0]);
-	transport_set_verbosity(transport, option_verbosity, option_progress);
-	transport->family = family;
-
 	path = get_repo_path(remote->url[0], &is_bundle);
 	is_local = option_local != 0 && path && !is_bundle;
 	if (is_local) {
@@ -1175,6 +1171,10 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	}
 	if (option_local > 0 && !is_local)
 		warning(_("--local is ignored"));
+
+	transport = transport_get(remote, path ? path : remote->url[0]);
+	transport_set_verbosity(transport, option_verbosity, option_progress);
+	transport->family = family;
 	transport->cloning = 1;
 
 	if (is_bundle) {

dir-iterator.c

@@ -203,7 +203,7 @@ struct dir_iterator *dir_iterator_begin(const char *path, unsigned int flags)
 {
 	struct dir_iterator_int *iter = xcalloc(1, sizeof(*iter));
 	struct dir_iterator *dir_iterator = &iter->base;
-	int saved_errno;
+	int saved_errno, err;
 
 	strbuf_init(&iter->base.path, PATH_MAX);
 	strbuf_addstr(&iter->base.path, path);
@@ -213,10 +213,15 @@ struct dir_iterator *dir_iterator_begin(const char *path, unsigned int flags)
 	iter->flags = flags;
 
 	/*
-	 * Note: stat already checks for NULL or empty strings and
-	 * inexistent paths.
+	 * Note: stat/lstat already checks for NULL or empty strings and
+	 * nonexistent paths.
 	 */
-	if (stat(iter->base.path.buf, &iter->base.st) < 0) {
+	if (iter->flags & DIR_ITERATOR_FOLLOW_SYMLINKS)
+		err = stat(iter->base.path.buf, &iter->base.st);
+	else
+		err = lstat(iter->base.path.buf, &iter->base.st);
+
+	if (err < 0) {
 		saved_errno = errno;
 		goto error_out;
 	}

dir-iterator.h

@@ -61,6 +61,11 @@
  *   not the symlinks themselves, which is the default behavior. Broken
  *   symlinks are ignored.
  *
+ *   Note: setting DIR_ITERATOR_FOLLOW_SYMLINKS affects resolving the
+ *   starting path as well (e.g., attempting to iterate starting at a
+ *   symbolic link pointing to a directory without FOLLOW_SYMLINKS will
+ *   result in an error).
+ *
  * Warning: circular symlinks are also followed when
  * DIR_ITERATOR_FOLLOW_SYMLINKS is set. The iteration may end up with
  * an ELOOP if they happen and DIR_ITERATOR_PEDANTIC is set.

git-curl-compat.h

@@ -126,4 +126,12 @@
 #define GIT_CURL_HAVE_CURLSSLSET_NO_BACKENDS
 #endif
 
+/**
+ * CURLOPT_PROTOCOLS_STR and CURLOPT_REDIR_PROTOCOLS_STR were added in 7.85.0,
+ * released in August 2022.
+ */
+#if LIBCURL_VERSION_NUM >= 0x075500
+#define GIT_CURL_HAVE_CURLOPT_PROTOCOLS_STR 1
+#endif
+
 #endif

http-push.c

@@ -198,13 +198,13 @@ static void curl_setup_http(CURL *curl, const char *url,
 		const char *custom_req, struct buffer *buffer,
 		curl_write_callback write_fn)
 {
-	curl_easy_setopt(curl, CURLOPT_PUT, 1);
+	curl_easy_setopt(curl, CURLOPT_UPLOAD, 1);
 	curl_easy_setopt(curl, CURLOPT_URL, url);
 	curl_easy_setopt(curl, CURLOPT_INFILE, buffer);
 	curl_easy_setopt(curl, CURLOPT_INFILESIZE, buffer->buf.len);
 	curl_easy_setopt(curl, CURLOPT_READFUNCTION, fread_buffer);
-	curl_easy_setopt(curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
-	curl_easy_setopt(curl, CURLOPT_IOCTLDATA, buffer);
+	curl_easy_setopt(curl, CURLOPT_SEEKFUNCTION, seek_buffer);
+	curl_easy_setopt(curl, CURLOPT_SEEKDATA, buffer);
 	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_fn);
 	curl_easy_setopt(curl, CURLOPT_NOBODY, 0);
 	curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, custom_req);

http.c

@@ -155,21 +155,19 @@ size_t fread_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
 	return size / eltsize;
 }
 
-curlioerr ioctl_buffer(CURL *handle, int cmd, void *clientp)
+int seek_buffer(void *clientp, curl_off_t offset, int origin)
 {
 	struct buffer *buffer = clientp;
 
-	switch (cmd) {
-	case CURLIOCMD_NOP:
-		return CURLIOE_OK;
-
-	case CURLIOCMD_RESTARTREAD:
-		buffer->posn = 0;
-		return CURLIOE_OK;
-
-	default:
-		return CURLIOE_UNKNOWNCMD;
+	if (origin != SEEK_SET)
+		BUG("seek_buffer only handles SEEK_SET");
+	if (offset < 0 || offset >= buffer->buf.len) {
+		error("curl seek would be outside of buffer");
+		return CURL_SEEKFUNC_FAIL;
 	}
+
+	buffer->posn = offset;
+	return CURL_SEEKFUNC_OK;
 }
 
 size_t fwrite_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
@@ -717,20 +715,37 @@ void setup_curl_trace(CURL *handle)
 	curl_easy_setopt(handle, CURLOPT_DEBUGDATA, NULL);
 }
 
-static long get_curl_allowed_protocols(int from_user)
+static void proto_list_append(struct strbuf *list, const char *proto)
 {
-	long allowed_protocols = 0;
+	if (!list)
+		return;
+	if (list->len)
+		strbuf_addch(list, ',');
+	strbuf_addstr(list, proto);
+}
 
-	if (is_transport_allowed("http", from_user))
-		allowed_protocols |= CURLPROTO_HTTP;
-	if (is_transport_allowed("https", from_user))
-		allowed_protocols |= CURLPROTO_HTTPS;
-	if (is_transport_allowed("ftp", from_user))
-		allowed_protocols |= CURLPROTO_FTP;
-	if (is_transport_allowed("ftps", from_user))
-		allowed_protocols |= CURLPROTO_FTPS;
+static long get_curl_allowed_protocols(int from_user, struct strbuf *list)
+{
+	long bits = 0;
 
-	return allowed_protocols;
+	if (is_transport_allowed("http", from_user)) {
+		bits |= CURLPROTO_HTTP;
+		proto_list_append(list, "http");
+	}
+	if (is_transport_allowed("https", from_user)) {
+		bits |= CURLPROTO_HTTPS;
+		proto_list_append(list, "https");
+	}
+	if (is_transport_allowed("ftp", from_user)) {
+		bits |= CURLPROTO_FTP;
+		proto_list_append(list, "ftp");
+	}
+	if (is_transport_allowed("ftps", from_user)) {
+		bits |= CURLPROTO_FTPS;
+		proto_list_append(list, "ftps");
+	}
+
+	return bits;
 }
 
 #ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
@@ -874,10 +889,26 @@ static CURL *get_curl_handle(void)
 
 	curl_easy_setopt(result, CURLOPT_MAXREDIRS, 20);
 	curl_easy_setopt(result, CURLOPT_POSTREDIR, CURL_REDIR_POST_ALL);
+
+#ifdef GIT_CURL_HAVE_CURLOPT_PROTOCOLS_STR
+	{
+		struct strbuf buf = STRBUF_INIT;
+
+		get_curl_allowed_protocols(0, &buf);
+		curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS_STR, buf.buf);
+		strbuf_reset(&buf);
+
+		get_curl_allowed_protocols(-1, &buf);
+		curl_easy_setopt(result, CURLOPT_PROTOCOLS_STR, buf.buf);
+		strbuf_release(&buf);
+	}
+#else
 	curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS,
-			 get_curl_allowed_protocols(0));
+			 get_curl_allowed_protocols(0, NULL));
 	curl_easy_setopt(result, CURLOPT_PROTOCOLS,
-			 get_curl_allowed_protocols(-1));
+			 get_curl_allowed_protocols(-1, NULL));
+#endif
+
 	if (getenv("GIT_CURL_VERBOSE"))
 		http_trace_curl_no_data();
 	setup_curl_trace(result);

http.h

@@ -40,7 +40,7 @@ struct buffer {
 size_t fread_buffer(char *ptr, size_t eltsize, size_t nmemb, void *strbuf);
 size_t fwrite_buffer(char *ptr, size_t eltsize, size_t nmemb, void *strbuf);
 size_t fwrite_null(char *ptr, size_t eltsize, size_t nmemb, void *strbuf);
-curlioerr ioctl_buffer(CURL *handle, int cmd, void *clientp);
+int seek_buffer(void *clientp, curl_off_t offset, int origin);
 
 /* Slot lifecycle functions */
 struct active_request_slot *get_active_slot(void);

remote-curl.c

@@ -714,25 +714,23 @@ static size_t rpc_out(void *ptr, size_t eltsize,
 	return avail;
 }
 
-static curlioerr rpc_ioctl(CURL *handle, int cmd, void *clientp)
+static int rpc_seek(void *clientp, curl_off_t offset, int origin)
 {
 	struct rpc_state *rpc = clientp;
 
-	switch (cmd) {
-	case CURLIOCMD_NOP:
-		return CURLIOE_OK;
+	if (origin != SEEK_SET)
+		BUG("rpc_seek only handles SEEK_SET, not %d", origin);
 
-	case CURLIOCMD_RESTARTREAD:
-		if (rpc->initial_buffer) {
-			rpc->pos = 0;
-			return CURLIOE_OK;
+	if (rpc->initial_buffer) {
+		if (offset < 0 || offset > rpc->len) {
+			error("curl seek would be outside of rpc buffer");
+			return CURL_SEEKFUNC_FAIL;
 		}
-		error(_("unable to rewind rpc post data - try increasing http.postBuffer"));
-		return CURLIOE_FAILRESTART;
-
-	default:
-		return CURLIOE_UNKNOWNCMD;
+		rpc->pos = offset;
+		return CURL_SEEKFUNC_OK;
 	}
+	error(_("unable to rewind rpc post data - try increasing http.postBuffer"));
+	return CURL_SEEKFUNC_FAIL;
 }
 
 struct check_pktline_state {
@@ -952,8 +950,8 @@ retry:
 		rpc->initial_buffer = 1;
 		curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, rpc_out);
 		curl_easy_setopt(slot->curl, CURLOPT_INFILE, rpc);
-		curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, rpc_ioctl);
-		curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, rpc);
+		curl_easy_setopt(slot->curl, CURLOPT_SEEKFUNCTION, rpc_seek);
+		curl_easy_setopt(slot->curl, CURLOPT_SEEKDATA, rpc);
 		if (options.verbosity > 1) {
 			fprintf(stderr, "POST %s (chunked)\n", rpc->service_name);
 			fflush(stderr);

t/t0066-dir-iterator.sh

@@ -110,7 +110,9 @@ test_expect_success SYMLINKS 'setup dirs with symlinks' '
 	mkdir -p dir5/a/c &&
 	ln -s ../c dir5/a/b/d &&
 	ln -s ../ dir5/a/b/e &&
-	ln -s ../../ dir5/a/b/f
+	ln -s ../../ dir5/a/b/f &&
+
+	ln -s dir4 dir6
 '
 
 test_expect_success SYMLINKS 'dir-iterator should not follow symlinks by default' '
@@ -146,4 +148,27 @@ test_expect_success SYMLINKS 'dir-iterator should follow symlinks w/ follow flag
 	test_cmp expected-follow-sorted-output actual-follow-sorted-output
 '
 
+test_expect_success SYMLINKS 'dir-iterator does not resolve top-level symlinks' '
+	test_must_fail test-tool dir-iterator ./dir6 >out &&
+
+	grep "ENOTDIR" out
+'
+
+test_expect_success SYMLINKS 'dir-iterator resolves top-level symlinks w/ follow flag' '
+	cat >expected-follow-sorted-output <<-EOF &&
+	[d] (a) [a] ./dir6/a
+	[d] (a/f) [f] ./dir6/a/f
+	[d] (a/f/c) [c] ./dir6/a/f/c
+	[d] (b) [b] ./dir6/b
+	[d] (b/c) [c] ./dir6/b/c
+	[f] (a/d) [d] ./dir6/a/d
+	[f] (a/e) [e] ./dir6/a/e
+	EOF
+
+	test-tool dir-iterator --follow-symlinks ./dir6 >out &&
+	sort out >actual-follow-sorted-output &&
+
+	test_cmp expected-follow-sorted-output actual-follow-sorted-output
+'
+
 test_done

t/t4115-apply-symlink.sh

@@ -45,4 +45,85 @@ test_expect_success 'apply --index symlink patch' '
 
 '
 
+test_expect_success 'symlink setup' '
+	ln -s .git symlink &&
+	git add symlink &&
+	git commit -m "add symlink"
+'
+
+test_expect_success SYMLINKS 'symlink escape when creating new files' '
+	test_when_finished "git reset --hard && git clean -dfx" &&
+
+	cat >patch <<-EOF &&
+	diff --git a/symlink b/renamed-symlink
+	similarity index 100%
+	rename from symlink
+	rename to renamed-symlink
+	--
+	diff --git /dev/null b/renamed-symlink/create-me
+	new file mode 100644
+	index 0000000..039727e
+	--- /dev/null
+	+++ b/renamed-symlink/create-me
+	@@ -0,0 +1,1 @@
+	+busted
+	EOF
+
+	test_must_fail git apply patch 2>stderr &&
+	cat >expected_stderr <<-EOF &&
+	error: affected file ${SQ}renamed-symlink/create-me${SQ} is beyond a symbolic link
+	EOF
+	test_cmp expected_stderr stderr &&
+	! test_path_exists .git/create-me
+'
+
+test_expect_success SYMLINKS 'symlink escape when modifying file' '
+	test_when_finished "git reset --hard && git clean -dfx" &&
+	touch .git/modify-me &&
+
+	cat >patch <<-EOF &&
+	diff --git a/symlink b/renamed-symlink
+	similarity index 100%
+	rename from symlink
+	rename to renamed-symlink
+	--
+	diff --git a/renamed-symlink/modify-me b/renamed-symlink/modify-me
+	index 1111111..2222222 100644
+	--- a/renamed-symlink/modify-me
+	+++ b/renamed-symlink/modify-me
+	@@ -0,0 +1,1 @@
+	+busted
+	EOF
+
+	test_must_fail git apply patch 2>stderr &&
+	cat >expected_stderr <<-EOF &&
+	error: renamed-symlink/modify-me: No such file or directory
+	EOF
+	test_cmp expected_stderr stderr &&
+	test_must_be_empty .git/modify-me
+'
+
+test_expect_success SYMLINKS 'symlink escape when deleting file' '
+	test_when_finished "git reset --hard && git clean -dfx && rm .git/delete-me" &&
+	touch .git/delete-me &&
+
+	cat >patch <<-EOF &&
+	diff --git a/symlink b/renamed-symlink
+	similarity index 100%
+	rename from symlink
+	rename to renamed-symlink
+	--
+	diff --git a/renamed-symlink/delete-me b/renamed-symlink/delete-me
+	deleted file mode 100644
+	index 1111111..0000000 100644
+	EOF
+
+	test_must_fail git apply patch 2>stderr &&
+	cat >expected_stderr <<-EOF &&
+	error: renamed-symlink/delete-me: No such file or directory
+	EOF
+	test_cmp expected_stderr stderr &&
+	test_path_is_file .git/delete-me
+'
+
 test_done

t/t5604-clone-reference.sh

@@ -344,4 +344,20 @@ test_expect_success SYMLINKS 'clone repo with symlinked or unknown files at obje
 	test_must_be_empty T--shared.objects-symlinks.raw
 '
 
+test_expect_success SYMLINKS 'clone repo with symlinked objects directory' '
+	test_when_finished "rm -fr sensitive malicious" &&
+
+	mkdir -p sensitive &&
+	echo "secret" >sensitive/file &&
+
+	git init malicious &&
+	rm -fr malicious/.git/objects &&
+	ln -s "$(pwd)/sensitive" ./malicious/.git/objects &&
+
+	test_must_fail git clone --local malicious clone 2>err &&
+
+	test_path_is_missing clone &&
+	grep "failed to start iterator over" err
+'
+
 test_done

t/t5619-clone-local-ambiguous-transport.sh

@@ -0,0 +1,70 @@
+#!/bin/sh
+
+test_description='test local clone with ambiguous transport'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-httpd.sh"
+
+if ! test_have_prereq SYMLINKS
+then
+	skip_all='skipping test, symlink support unavailable'
+	test_done
+fi
+
+start_httpd
+
+REPO="$HTTPD_DOCUMENT_ROOT_PATH/sub.git"
+URI="$HTTPD_URL/dumb/sub.git"
+
+test_expect_success 'setup' '
+	mkdir -p sensitive &&
+	echo "secret" >sensitive/secret &&
+
+	git init --bare "$REPO" &&
+	test_commit_bulk -C "$REPO" --ref=main 1 &&
+
+	git -C "$REPO" update-ref HEAD main &&
+	git -C "$REPO" update-server-info &&
+
+	git init malicious &&
+	(
+		cd malicious &&
+
+		git submodule add "$URI" &&
+
+		mkdir -p repo/refs &&
+		touch repo/refs/.gitkeep &&
+		printf "ref: refs/heads/a" >repo/HEAD &&
+		ln -s "$(cd .. && pwd)/sensitive" repo/objects &&
+
+		mkdir -p "$HTTPD_URL/dumb" &&
+		ln -s "../../../.git/modules/sub/../../../repo/" "$URI" &&
+
+		git add . &&
+		git commit -m "initial commit"
+	) &&
+
+	# Delete all of the references in our malicious submodule to
+	# avoid the client attempting to checkout any objects (which
+	# will be missing, and thus will cause the clone to fail before
+	# we can trigger the exploit).
+	git -C "$REPO" for-each-ref --format="delete %(refname)" >in &&
+	git -C "$REPO" update-ref --stdin <in &&
+	git -C "$REPO" update-server-info
+'
+
+test_expect_success 'ambiguous transport does not lead to arbitrary file-inclusion' '
+	git clone malicious clone &&
+	test_must_fail git -C clone submodule update --init 2>err &&
+
+	test_path_is_missing clone/.git/modules/sub/objects/secret &&
+	# We would actually expect "transport .file. not allowed" here,
+	# but due to quirks of the URL detection in Git, we mis-parse
+	# the absolute path as a bogus URL and die before that step.
+	#
+	# This works for now, and if we ever fix the URL detection, it
+	# is OK to change this to detect the transport error.
+	grep "protocol .* is not supported" err
+'
+
+test_done