tar: prevent empty file to be treated as valid tarball

function                                             old     new   delta
tar_main                                             879     895     +16

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/testsuite/tar.tests b/testsuite/tar.tests
index c947d33..93ba5f0 100755
--- a/testsuite/tar.tests
+++ b/testsuite/tar.tests
@@ -15,6 +15,15 @@ mkdir tar.tempdir && cd tar.tempdir || exit 1
 
 # testing "test name" "script" "expected result" "file input" "stdin"
 
+testing "Empty file is not a tarball" '\
+tar xvf - 2>&1; echo $?
+' "\
+tar: short read
+1
+" \
+"" ""
+SKIP=
+
 optional FEATURE_SEAMLESS_GZ
 testing "Empty file is not a tarball.tar.gz" '\
 tar xvzf - 2>&1; echo $?
@@ -26,6 +35,22 @@ tar: short read
 "" ""
 SKIP=
 
+testing "Two zeroed blocks is a ('truncated') empty tarball" '\
+dd if=/dev/zero bs=512 count=2 2>/dev/null | strace -o /tmp/zzz -tt -s99 tar xvf - 2>&1; echo $?
+' "\
+0
+" \
+"" ""
+SKIP=
+
+testing "Twenty zeroed blocks is an empty tarball" '\
+dd if=/dev/zero bs=512 count=20 2>/dev/null | tar xvf - 2>&1; echo $?
+' "\
+0
+" \
+"" ""
+SKIP=
+
 optional FEATURE_TAR_CREATE FEATURE_LS_SORTFILES
 testing "tar hardlinks and repeated files" '\
 rm -rf input_* test.tar 2>/dev/null