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[31.211.229.121]) by smtp.gmail.com with ESMTPSA id n3sm2608364ljc.114.2020.08.01.15.06.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 01 Aug 2020 15:06:51 -0700 (PDT) From: =?UTF-8?q?Martin=20=C3=85gren?= To: git@vger.kernel.org Cc: Jonathan Tan Subject: [PATCH] t1450: fix quoting of NUL byte when corrupting pack Date: Sun, 2 Aug 2020 00:06:11 +0200 Message-Id: <20200801220611.10453-1-martin.agren@gmail.com> X-Mailer: git-send-email 2.28.0.81.ge8ab941b67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org We use printf '\0' to generate a NUL byte which we then `dd` into the packfile to ensure that we modify the first byte of the first object, thereby (probabilistically) invalidating the checksum. Except the single quotes we're using are interpreted to match with the ones we enclose the whole test in. So we actually execute printf \0 and end up injecting the ASCII code for "0", 0x30, instead. The comment right above this `printf` invocation says that "at least one of [the type bits] is not zero, so setting the first byte to 0 is sufficient". Substituting "0x30" for "0" in that comment won't do: we'd need to reason about which bits go where and just what the packfile looks like that we're modifying in this test. Let's avoid all of that by actually executing printf "\0" to generate a NUL byte, as intended. Signed-off-by: Martin Ågren --- If my reading is correct, when we substitute 0x30, the type will be 3 (blob) and the size will be zero. So there might actually exist formally valid packfiles where this byte that we're modifying is already zero. What matters in the end is whether we might be using such a packfile in this exact test and from what I can tell, no, we won't be doing that. t/t1450-fsck.sh | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh index 344a2aad82..af2a2c4682 100755 --- a/t/t1450-fsck.sh +++ b/t/t1450-fsck.sh @@ -714,7 +714,7 @@ test_expect_success 'fsck fails on corrupt packfile' ' # at least one of which is not zero, so setting the first byte to 0 is # sufficient.) chmod a+w .git/objects/pack/pack-$pack.pack && - printf '\0' | dd of=.git/objects/pack/pack-$pack.pack bs=1 conv=notrunc seek=12 && + printf "\0" | dd of=.git/objects/pack/pack-$pack.pack bs=1 conv=notrunc seek=12 && test_when_finished "rm -f .git/objects/pack/pack-$pack.*" && remove_object $hsh && -- 2.28.0.81.ge8ab941b67