Merge branch 'dd/mailinfo-with-nul'

Tighten "git mailinfo" to notice and error out when decoded result
contains NUL in it.

* dd/mailinfo-with-nul:
  mailinfo: disallow NUL character in mail's header
  mailinfo.c: avoid strlen on strings that can contains NUL
  t4254: merge 2 steps of a single test

mailinfo.c

@@ -447,19 +447,21 @@ static int convert_to_utf8(struct mailinfo *mi,
 			   struct strbuf *line, const char *charset)
 {
 	char *out;
+	size_t out_len;
 
 	if (!mi->metainfo_charset || !charset || !*charset)
 		return 0;
 
 	if (same_encoding(mi->metainfo_charset, charset))
 		return 0;
-	out = reencode_string(line->buf, mi->metainfo_charset, charset);
+	out = reencode_string_len(line->buf, line->len,
+				  mi->metainfo_charset, charset, &out_len);
 	if (!out) {
 		mi->input_error = -1;
 		return error("cannot convert from %s to %s",
 			     charset, mi->metainfo_charset);
 	}
-	strbuf_attach(line, out, strlen(out), strlen(out));
+	strbuf_attach(line, out, out_len, out_len);
 	return 0;
 }
 
@@ -1136,6 +1138,11 @@ static void handle_info(struct mailinfo *mi)
 		else
 			continue;
 
+		if (memchr(hdr->buf, '\0', hdr->len)) {
+			error("a NUL byte in '%s' is not allowed.", header[i]);
+			mi->input_error = -1;
+		}
+
 		if (!strcmp(header[i], "Subject")) {
 			if (!mi->keep_subject) {
 				cleanup_subject(mi, hdr);

t/t4254-am-corrupt.sh

@@ -3,6 +3,37 @@
 test_description='git am with corrupt input'
 . ./test-lib.sh
 
+make_mbox_with_nul () {
+	space=' '
+	q_nul_in_subject=
+	q_nul_in_body=
+	while test $# -ne 0
+	do
+		case "$1" in
+		subject) q_nul_in_subject='=00' ;;
+		body)    q_nul_in_body='=00' ;;
+		esac &&
+		shift
+	done &&
+	cat <<-EOF
+	From ec7364544f690c560304f5a5de9428ea3b978b26 Mon Sep 17 00:00:00 2001
+	From: A U Thor <author@example.com>
+	Date: Sun, 19 Apr 2020 13:42:07 +0700
+	Subject: [PATCH] =?ISO-8859-1?q?=C4=CB${q_nul_in_subject}=D1=CF=D6?=
+	MIME-Version: 1.0
+	Content-Type: text/plain; charset=ISO-8859-1
+	Content-Transfer-Encoding: quoted-printable
+
+	abc${q_nul_in_body}def
+	---
+	diff --git a/afile b/afile
+	new file mode 100644
+	index 0000000000..e69de29bb2
+	--$space
+	2.26.1
+	EOF
+}
+
 test_expect_success setup '
 	# Note the missing "+++" line:
 	cat >bad-patch.diff <<-\EOF &&
@@ -25,13 +56,27 @@ test_expect_success setup '
 #   fatal: unable to write file '(null)' mode 100644: Bad address
 # Also, it had the unwanted side-effect of deleting f.
 test_expect_success 'try to apply corrupted patch' '
-	test_must_fail git -c advice.amWorkDir=false am bad-patch.diff 2>actual
+	test_when_finished "git am --abort" &&
-'
+	test_must_fail git -c advice.amWorkDir=false am bad-patch.diff 2>actual &&
-
-test_expect_success 'compare diagnostic; ensure file is still here' '
 	echo "error: git diff header lacks filename information (line 4)" >expected &&
 	test_path_is_file f &&
 	test_i18ncmp expected actual
 '
 
+test_expect_success "NUL in commit message's body" '
+	test_when_finished "git am --abort" &&
+	make_mbox_with_nul body >body.patch &&
+	test_must_fail git am body.patch 2>err &&
+	grep "a NUL byte in commit log message not allowed" err
+'
+
+test_expect_success "NUL in commit message's header" "
+	test_when_finished 'git am --abort' &&
+	make_mbox_with_nul subject >subject.patch &&
+	test_must_fail git mailinfo msg patch <subject.patch 2>err &&
+	grep \"a NUL byte in 'Subject' is not allowed\" err &&
+	test_must_fail git am subject.patch 2>err &&
+	grep \"a NUL byte in 'Subject' is not allowed\" err
+"
+
 test_done