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[PATCH 2/2] receive-pack: Add receive.denyObjectLimit to refuse push with too many objects

From
Johan Herland <johan@herland.net>
Date
May 13, 2011, 16:54 UTC
Message-ID
<201105131854.31540.johan@herland.net>

The new receive.denyObjectLimit config variable defines an upper limit on the number of objects to accept in a single push. If the number of objects in a push exceeds this limit, the entire push is immediately aborted without storing the pushed objects on the server at all.

This is meant to prevent an unintended large push (typically a result of the user not being aware of exactly what is being pushed, e.g. pushing a large rewritten history) from entering the repo.

Usually, this kind of limit could be imposed by a pre-receive or update hook, but both of those run _after_ the pack has been received and stored by receive-pack, so they cannot prevent the pack from being transferred in the first place.

Documentation and tests are included.
Signed-off-by: Johan Herland <johan@herland.net>
---

There's something weird going on here: The included test case works as intended, but when I try to test this in "real-world" conditions, I don't get the expected error message in the output:

  # From inside my git.git repo:
  $ git init --bare foo.git
  $ (cd foo.git && git config receive.denyObjectLimit 100000)
  $ git push foo.git/ master
  Pushing to foo.git/
  Counting objects: 112383, done.
  Delta compression using up to 8 threads.
  Compressing objects: 100% (27658/27658), done.
  error: pack-objects died of signal 13
  error: failed to push some refs to 'foo.git/'
  $

So the pack-objects on the local side dies of a broken pipe (as expected), but the error message from the remote side:

  error: unpack failed: received pack exceeds configured receive.denyObjectLimit

is never printed, so the user gets no clue as to why the push failed. This should be fixed before this patch can be considered for inclusion.

...Johan
 Documentation/config.txt |    9 +++++++++
 builtin/receive-pack.c   |   10 +++++++++-
 t/t5400-send-pack.sh     |   44 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 1 deletions(-)
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 285c7f7..7c60146 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1591,6 +1591,15 @@ receive.unpackLimit::
 	especially on slow filesystems.  If not set, the value of
 	`transfer.unpackLimit` is used instead.
 
+receive.denyObjectLimit::
+	If the number of objects received in a push exceeds this limit,
+	then the entire push will be refused. This is meant to prevent
+	an unintended large push (typically a result of the user not
+	being aware of exactly what is being pushed, e.g. pushing a
+	large rewritten history) from entering the repo. If not set,
+	there is no upper limit on the number of objects transferred
+	in a single push.
+
 receive.denyDeletes::
 	If set to true, git-receive-pack will deny a ref update that deletes
 	the ref. Use this to prevent such a ref deletion via a push.
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e1ba4dc..856650f 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -25,6 +25,7 @@ static int deny_non_fast_forwards;
 static enum deny_action deny_current_branch = DENY_UNCONFIGURED;
 static enum deny_action deny_delete_current = DENY_UNCONFIGURED;
 static int receive_fsck_objects;
+static int receive_deny_limit;
 static int receive_unpack_limit = -1;
 static int transfer_unpack_limit = -1;
 static int unpack_limit = 100;
@@ -63,6 +64,11 @@ static int receive_pack_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (strcmp(var, "receive.denyobjectlimit") == 0) {
+		receive_deny_limit = git_config_int(var, value);
+		return 0;
+	}
+
 	if (strcmp(var, "receive.unpacklimit") == 0) {
 		receive_unpack_limit = git_config_int(var, value);
 		return 0;
@@ -648,7 +654,9 @@ static const char *unpack(void)
 			"--pack_header=%"PRIu32",%"PRIu32,
 			ntohl(hdr.hdr_version), ntohl(hdr.hdr_entries));
 
-	if (ntohl(hdr.hdr_entries) < unpack_limit) {
+	if (receive_deny_limit > 0 && ntohl(hdr.hdr_entries) > receive_deny_limit)
+		return "received pack exceeds configured receive.denyObjectLimit";
+	else if (ntohl(hdr.hdr_entries) < unpack_limit) {
 		int code, i = 0;
 		const char *unpacker[4];
 		unpacker[i++] = "unpack-objects";
diff --git a/t/t5400-send-pack.sh b/t/t5400-send-pack.sh
index 0eace37..2fbe34b 100755
--- a/t/t5400-send-pack.sh
+++ b/t/t5400-send-pack.sh
@@ -222,4 +222,48 @@ test_expect_success 'deny pushing to delete current branch' '
 	)
 '
 
+test_expect_success 'deny pushing when receive.denyObjectLimit is exceeded' '
+	rewound_push_setup &&
+	(
+	    cd parent &&
+	    git config receive.denyObjectLimit 1
+	) &&
+	(
+	    cd child &&
+	    git reset --hard origin/master &&
+	    echo three > file && git commit -a -m three &&
+	    test_must_fail git send-pack ../parent master 2>errs &&
+	    grep -q "receive\\.denyObjectLimit" errs
+	) &&
+	parent_head=$(cd parent && git rev-parse --verify master) &&
+	child_head=$(cd child && git rev-parse --verify master) &&
+	test "$parent_head" != "$child_head"
+'
+
+test_expect_success 'repeated push failure proves that objects were not stored remotely' '
+	(
+	    cd child &&
+	    test_must_fail git send-pack ../parent master 2>errs &&
+	    grep -q "receive\\.denyObjectLimit" errs
+	) &&
+	parent_head=$(cd parent && git rev-parse --verify master) &&
+	child_head=$(cd child && git rev-parse --verify master) &&
+	test "$parent_head" != "$child_head"
+'
+
+test_expect_success 'increasing receive.denyObjectLimit allows the push' '
+	(
+	    cd parent &&
+	    git config receive.denyObjectLimit 10
+	) &&
+	(
+	    cd child &&
+	    git send-pack ../parent master 2>errs &&
+	    test_must_fail grep -q "receive\\.denyObjectLimit" errs
+	) &&
+	parent_head=$(cd parent && git rev-parse --verify master) &&
+	child_head=$(cd child && git rev-parse --verify master) &&
+	test "$parent_head" = "$child_head"
+'
+
 test_done

-- 
1.7.5.1.354.g761178


-- 
Johan Herland, <johan@herland.net>
www.herland.net
Next: Junio C Hamano
Message 1 of 53 in “receive-pack: Add receive.denyObjectLimit to refuse push with too many objects”
  1. 2/2 receive-pack: Add receive.denyObjectLimit to refuse push with too many objectsJohan Herland, May 13, 2011
  2. Junio C HamanoMay 13, 2011
  3. Johan HerlandMay 14, 2011
  4. 2/2 receive-pack: Add receive.objectCountLimit to refuse push with too many objectsJohan Herland, May 14, 2011
  5. Shawn PearceMay 14, 2011
  6. Johan HerlandMay 14, 2011
  7. Shawn PearceMay 14, 2011
  8. Johan HerlandMay 15, 2011
  9. 0/9 Push limitsJohan Herland, May 15, 2011
  10. 1/9 Update technical docs to reflect side-band-64k capability in receive-packJohan Herland, May 15, 2011
  11. 2/9 send-pack: Attempt to retrieve remote status even if pack-objects failsJohan Herland, May 15, 2011
  12. Jeff KingMay 16, 2011
  13. Jeff KingMay 16, 2011
  14. Jeff KingMay 16, 2011
  15. 1/3 connect: treat generic proxy processes like ssh processesJeff King, May 16, 2011
  16. Johannes SixtMay 16, 2011
  17. Junio C HamanoMay 16, 2011
  18. Jeff KingMay 17, 2011
  19. Johannes SixtMay 17, 2011
  20. Jeff KingMay 18, 2011
  21. 2/3 connect: let callers know if connection is a socketJeff King, May 16, 2011
  22. 3/3 send-pack: avoid deadlock on git:// push with failed pack-objectsJeff King, May 16, 2011
  23. Johannes SixtMay 16, 2011
  24. Jeff KingMay 17, 2011
  25. Windows: add a wrapper for the shutdown() system callJohannes Sixt, May 18, 2011
  26. 3/9 pack-objects: Allow --max-pack-size to be used together with --stdoutJohan Herland, May 15, 2011
  27. Shawn PearceMay 15, 2011
  28. Johan HerlandMay 16, 2011
  29. Junio C HamanoMay 16, 2011
  30. Johan HerlandMay 16, 2011
  31. 4/9 pack-objects: Teach new option --max-object-count, similar to --max-pack-sizeJohan Herland, May 15, 2011
  32. Shawn PearceMay 15, 2011
  33. Johan HerlandMay 15, 2011
  34. Shawn PearceMay 15, 2011
  35. Junio C HamanoMay 16, 2011
  36. Johan HerlandMay 16, 2011
  37. 5/9 pack-objects: Teach new option --max-commit-count, limiting #commits in packJohan Herland, May 15, 2011
  38. 6/9 receive-pack: Prepare for addition of the new 'limit-*' family of capabilitiesJohan Herland, May 15, 2011
  39. Junio C HamanoMay 16, 2011
  40. Johan HerlandMay 16, 2011
  41. Sverre RabbelierMay 16, 2011
  42. Junio C HamanoMay 16, 2011
  43. Sverre RabbelierMay 16, 2011
  44. Junio C HamanoMay 16, 2011
  45. Sverre RabbelierMay 16, 2011
  46. 7/9 send-pack/receive-pack: Allow server to refuse pushes with too many objectsJohan Herland, May 15, 2011
  47. 8/9 send-pack/receive-pack: Allow server to refuse pushing too large packsJohan Herland, May 15, 2011
  48. 9/9 send-pack/receive-pack: Allow server to refuse pushes with too many commitsJohan Herland, May 15, 2011
  49. Ævar Arnfjörð BjarmasonMay 15, 2011
  50. Junio C HamanoMay 14, 2011
  51. Shawn PearceMay 14, 2011
  52. Johannes SixtMay 13, 2011
  53. Johan HerlandMay 14, 2011

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