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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Christian Couder <christian.couder@gmail.com>, git@vger.kernel.org
Subject: [PATCH 9/9] sequencer: handle ignore_footer when parsing trailers
Date: Wed, 22 Aug 2018 20:51:57 -0400	[thread overview]
Message-ID: <20180823005157.GI3126@sigill.intra.peff.net> (raw)
In-Reply-To: <20180823004300.GA1355@sigill.intra.peff.net>

The append_signoff() function takes an "ignore_footer"
argument, which specifies a number of bytes at the end of
the message buffer which should not be considered (they
cannot contain trailers, and the trailer is spliced in
before them).

But to find the existing trailers, it calls into
has_conforming_trailer(). That function takes an
ignore_footer parameter, but since 967dfd4d56 (sequencer:
use trailer's trailer layout, 2016-11-02) the parameter is
completely ignored.

The trailer interface we're using takes a single string,
with no option to tell it to use part of the string.
However, since we have a mutable strbuf, we can work around
this by simply overwriting (and later restoring) the
boundary with a NUL.

I'm not sure if this can actually trigger a bug in practice.
It's easy to get a non-zero ignore_footer by doing something
like this:

  git commit -F - --cleanup=verbatim <<-EOF
  subject

  body

  Signed-off-by: me

  # this looks like a comment, but is actually in the
  # message! That makes the earlier s-o-b fake.
  EOF

  git commit --amend -s

There git-commit calls ignore_non_trailer() to count up the
"#" cruft, which becomes the ignore_footer header. But it
works even without this patch! That's because the trailer
code _also_ calls ignore_non_trailer() and skips the cruft,
too. So it happens to work because the only callers with a
non-zero ignore_footer are using the exact same function
that the trailer parser uses internally.

And that seems true for all of the current callers, but
there's nothing guaranteeing it. We're better off only
feeding the correct buffer to the trailer code in the first
place.

Signed-off-by: Jeff King <peff@peff.net>
---
I think this is probably worth doing, even if it's a noop. But I'm
really leaning towards the idea that the trailer code calling
ignore_non_trailer() is probably the wrong thing (in which case this
would be very important, since we'd be relying on the caller to remove
any cruft).

 sequencer.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/sequencer.c b/sequencer.c
index c01ff79ab0..a1f0f17bcd 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -231,11 +231,20 @@ static int has_conforming_footer(struct strbuf *sb, struct strbuf *sob,
 	struct trailer_info info;
 	size_t i;
 	int found_sob = 0, found_sob_last = 0;
+	char saved_char;
 
 	opts.no_divider = 1;
 
+	if (ignore_footer) {
+		saved_char = sb->buf[sb->len - ignore_footer];
+		sb->buf[sb->len - ignore_footer] = '\0';
+	}
+
 	trailer_info_get(&info, sb->buf, &opts);
 
+	if (ignore_footer)
+		sb->buf[sb->len - ignore_footer] = saved_char;
+
 	if (info.trailer_start == info.trailer_end)
 		return 0;
 
-- 
2.19.0.rc0.412.g7005db4e88

  parent reply	other threads:[~2018-08-23  0:58 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-21 18:41 [PATCH] test-tool.h: include git-compat-util.h Jeff King
2018-08-21 19:03 ` Junio C Hamano
2018-08-21 19:06 ` [PATCH 1/6] t/perf: factor boilerplate out of test_perf Jeff King
2018-08-21 19:06 ` [PATCH 2/6] t/perf: factor out percent calculations Jeff King
2018-08-21 19:06 ` [PATCH 3/6] t/perf: add infrastructure for measuring sizes Jeff King
2018-08-22 13:40   ` Derrick Stolee
2018-08-22 15:31     ` Jeff King
2018-08-21 19:06 ` [PATCH 4/6] t/perf: add perf tests for fetches from a bitmapped server Jeff King
2018-08-21 19:07 ` [PATCH 5/6] pack-bitmap: save "have" bitmap from walk Jeff King
2018-08-21 19:47   ` Derrick Stolee
2018-08-21 19:54     ` Jeff King
2018-08-31 15:23   ` Ævar Arnfjörð Bjarmason
2018-08-31 22:55     ` Jeff King
2018-09-01  7:41       ` [PATCH 0/4] un-breaking pack-objects with bitmaps Jeff King
2018-09-01  7:44         ` [PATCH 1/4] bitmap_has_sha1_in_uninteresting(): drop BUG check Jeff King
2018-09-01  7:48         ` [PATCH 2/4] t5310: test delta reuse with bitmaps Jeff King
2018-09-01  8:03           ` Jeff King
2018-09-01 20:29             ` Ævar Arnfjörð Bjarmason
2018-09-01 22:46               ` Ben Peart
2018-09-02  5:51               ` Jeff King
2018-09-04 19:05             ` Stefan Beller
2018-09-04 19:45               ` Junio C Hamano
2018-09-04 20:02               ` Jeff King
2018-09-01  7:49         ` [PATCH 3/4] traverse_bitmap_commit_list(): don't free result Jeff King
2018-09-01  7:50         ` [PATCH 4/4] pack-bitmap: drop "loaded" flag Jeff King
2018-09-04 19:30         ` [PATCH 0/4] un-breaking pack-objects with bitmaps Stefan Beller
2018-09-04 20:03           ` Jeff King
2018-09-08  6:43         ` Ævar Arnfjörð Bjarmason
2018-09-10 16:53           ` Junio C Hamano
2018-09-10 18:48             ` Jeff King
2018-09-10 19:23               ` Junio C Hamano
2018-08-21 19:07 ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King
2018-08-21 19:43   ` Junio C Hamano
2018-08-21 19:50     ` Junio C Hamano
2018-08-21 20:07       ` Jeff King
2018-08-21 20:14         ` Jeff King
2018-08-21 20:52           ` Junio C Hamano
2018-08-21 21:30             ` Jeff King
2018-08-21 20:57         ` Junio C Hamano
2018-08-21 21:32           ` Jeff King
2018-08-23  0:43           ` [PATCH 0/9] trailer-parsing false positives Jeff King
2018-08-23  0:44             ` [PATCH 1/9] trailer: use size_t for string offsets Jeff King
2018-08-23  0:45             ` [PATCH 2/9] trailer: use size_t for iterating trailer list Jeff King
2018-08-23  0:46             ` [PATCH 3/9] trailer: pass process_trailer_opts to trailer_info_get() Jeff King
2018-08-23  0:48             ` [PATCH 4/9] interpret-trailers: tighten check for "---" patch boundary Jeff King
2018-08-23  0:49             ` [PATCH 5/9] interpret-trailers: allow suppressing "---" divider Jeff King
2018-08-23  0:50             ` [PATCH 6/9] pretty, ref-filter: format %(trailers) with no_divider option Jeff King
2018-08-23  0:50             ` [PATCH 7/9] sequencer: ignore "---" divider when parsing trailers Jeff King
2018-08-23  0:50             ` [PATCH 8/9] append_signoff: use size_t for string offsets Jeff King
2018-08-23  0:51             ` Jeff King [this message]
2018-08-23 18:30             ` [PATCH 0/9] trailer-parsing false positives Junio C Hamano
2018-08-24  7:26               ` Jeff King
2018-08-21 20:00     ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King

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