[PATCH v2 7/8] fast-import: forbid escaped NUL in paths

[Thalia Archibald <thalia@archibald.dev>]

NUL cannot appear in paths. Even disregarding filesystem path
limitations, the tree object format delimits with NUL, so such a path
cannot be encoded by Git.

When a quoted path is unquoted, it could possibly contain NUL from
"\000". Forbid it so it isn't truncated.

fast-import still has other issues with NUL, but those will be addressed
later.

Signed-off-by: Thalia Archibald <thalia@archibald.dev>
---
 Documentation/git-fast-import.txt | 1 +
 builtin/fast-import.c             | 2 ++
 t/t9300-fast-import.sh            | 1 +
 3 files changed, 4 insertions(+)

diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
index db53b50268..edda30f90c 100644
--- a/Documentation/git-fast-import.txt
+++ b/Documentation/git-fast-import.txt
@@ -660,6 +660,7 @@ and must be in canonical form. That is it must not:
 
 The root of the tree can be represented by an empty string as `<path>`.
 
+`<path>` cannot contain NUL, either literally or escaped as `\000`.
 It is recommended that `<path>` always be encoded using UTF-8.
 
 `filedelete`
diff --git a/builtin/fast-import.c b/builtin/fast-import.c
index fc6eeaf89c..9d0f53fe04 100644
--- a/builtin/fast-import.c
+++ b/builtin/fast-import.c
@@ -2268,6 +2268,8 @@ static void parse_path(struct strbuf *sb, const char *p, const char **endp, int
 	if (*p == '"') {
 		if (unquote_c_style(sb, p, endp))
 			die("Invalid %s: %s", field, command_buf.buf);
+		if (strlen(sb->buf) != sb->len)
+			die("NUL in %s: %s", field, command_buf.buf);
 	} else {
 		if (include_spaces)
 			*endp = p + strlen(p);
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index e10962dffe..794a96df38 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -3294,6 +3294,7 @@ test_path_base_fail () {
 	local change="$1" prefix="$2" field="$3" suffix="$4"
 	test_path_fail "$change" 'unclosed " in '"$field"          "$prefix" '"hello.c'    "$suffix" "Invalid $field"
 	test_path_fail "$change" "invalid escape in quoted $field" "$prefix" '"hello\xff"' "$suffix" "Invalid $field"
+	test_path_fail "$change" "escaped NUL in quoted $field"    "$prefix" '"hello\000"' "$suffix" "NUL in $field"
 }
 test_path_eol_quoted_fail () {
 	local change="$1" prefix="$2" field="$3" suffix="$4"
-- 
2.44.0