[PATCH 1/4] archive-tar: report wrong pax extended header length

["René Scharfe" <l.s.r@web.de>]

Extended header entries contain a length value that is a bit tricky to
calculate because it includes its own length (number of decimal digits)
as well.  We get it wrong in corner cases.  Add a check, report wrong
results as a warning and add a test for exercising it.

Signed-off-by: René Scharfe <l.s.r@web.de>
---
 archive-tar.c                   |  6 ++++++
 t/t5004-archive-corner-cases.sh | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/archive-tar.c b/archive-tar.c
index 3e53aac1e6..355c8142c6 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -144,6 +144,7 @@ static int stream_blocked(const struct object_id *oid)
 static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
 				     const char *value, unsigned int valuelen)
 {
+	size_t orig_len = sb->len;
 	int len, tmp;

 	/* "%u %s=%s\n" */
@@ -155,6 +156,11 @@ static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
 	strbuf_addf(sb, "%u %s=", len, keyword);
 	strbuf_add(sb, value, valuelen);
 	strbuf_addch(sb, '\n');
+
+	if (len != sb->len - orig_len)
+		warning("pax extended header length miscalculated as %d"
+			", should be %"PRIuMAX,
+			len, (uintmax_t)(sb->len - orig_len));
 }

 /*
diff --git a/t/t5004-archive-corner-cases.sh b/t/t5004-archive-corner-cases.sh
index 271eb5a1fd..2f15d1899d 100755
--- a/t/t5004-archive-corner-cases.sh
+++ b/t/t5004-archive-corner-cases.sh
@@ -204,4 +204,24 @@ test_expect_success EXPENSIVE,LONG_IS_64BIT,UNZIP,UNZIP_ZIP64_SUPPORT,ZIPINFO \
 	grep $size big.lst
 '

+build_tree() {
+	perl -e '
+		my $hash = $ARGV[0];
+		foreach my $order (2..6) {
+			$first = 10 ** $order;
+			foreach my $i (-13..-9) {
+				my $name = "a" x ($first + $i);
+				print "100644 blob $hash\t$name\n"
+			}
+		}
+	' "$1"
+}
+
+test_expect_failure 'tar archive with long paths' '
+	blob=$(echo foo | git hash-object -w --stdin) &&
+	tree=$(build_tree $blob | git mktree) &&
+	git archive -o long_paths.tar $tree 2>stderr &&
+	test_must_be_empty stderr
+'
+
 test_done
--
2.23.0