From: Glen Choo <chooglen@google.com>
To: git@vger.kernel.org
Cc: Glen Choo <chooglen@google.com>
Subject: [PATCH] fsck: detect bare repos in trees and warn
Date: Wed, 6 Apr 2022 16:22:31 -0700 [thread overview]
Message-ID: <20220406232231.47714-1-chooglen@google.com> (raw)
In-Reply-To: <kl6lsfqpygsj.fsf@chooglen-macbookpro.roam.corp.google.com>
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Git tries not to distribute configs in-repo because they are a security
risk. However, an attacker can do exactly this if they embed a bare
repo inside of another repo.
Teach fsck to detect whether a tree object contains a bare repo (as
determined by setup.c) and warn. This will help hosting sites detect and
prevent transmission of such malicious repos.
See [1] for a more in-depth discussion, including future steps and
alternatives.
[1] https://lore.kernel.org/git/kl6lsfqpygsj.fsf@chooglen-macbookpro.roam.corp.google.com/
Signed-off-by: Glen Choo <chooglen@google.com>
---
fsck.c | 19 +++++++++++++++++++
fsck.h | 1 +
setup.c | 4 ++++
t/t1450-fsck.sh | 36 ++++++++++++++++++++++++++++++++++++
4 files changed, 60 insertions(+)
diff --git a/fsck.c b/fsck.c
index 3ec500d707..11c11c348a 100644
--- a/fsck.c
+++ b/fsck.c
@@ -573,6 +573,9 @@ static int fsck_tree(const struct object_id *tree_oid,
int has_bad_modes = 0;
int has_dup_entries = 0;
int not_properly_sorted = 0;
+ int has_head = 0;
+ int has_refs_entry = 0;
+ int has_objects_entry = 0;
struct tree_desc desc;
unsigned o_mode;
const char *o_name;
@@ -602,6 +605,12 @@ static int fsck_tree(const struct object_id *tree_oid,
has_dotdot |= !strcmp(name, "..");
has_dotgit |= is_hfs_dotgit(name) || is_ntfs_dotgit(name);
has_zero_pad |= *(char *)desc.buffer == '0';
+ has_head |= !strcasecmp(name, "HEAD")
+ && (S_ISLNK(mode) || S_ISREG(mode));
+ has_refs_entry |= !strcasecmp(name, "refs")
+ && (S_ISLNK(mode) || S_ISDIR(mode));
+ has_objects_entry |= !strcasecmp(name, "objects")
+ && (S_ISLNK(mode) || S_ISDIR(mode));
if (is_hfs_dotgitmodules(name) || is_ntfs_dotgitmodules(name)) {
if (!S_ISLNK(mode))
@@ -739,6 +748,16 @@ static int fsck_tree(const struct object_id *tree_oid,
retval += report(options, tree_oid, OBJ_TREE,
FSCK_MSG_TREE_NOT_SORTED,
"not properly sorted");
+ /*
+ * Determine if this tree looks like a bare repository according
+ * to the rules of setup.c. If those are changed, this should be
+ * changed too.
+ */
+ if (has_head && has_refs_entry && has_objects_entry)
+ retval += report(options, tree_oid, OBJ_TREE,
+ FSCK_MSG_EMBEDDED_BARE_REPO,
+ "contains bare repository");
+
return retval;
}
diff --git a/fsck.h b/fsck.h
index d07f7a2459..3f0f73b0f3 100644
--- a/fsck.h
+++ b/fsck.h
@@ -65,6 +65,7 @@ enum fsck_msg_type {
FUNC(NULL_SHA1, WARN) \
FUNC(ZERO_PADDED_FILEMODE, WARN) \
FUNC(NUL_IN_COMMIT, WARN) \
+ FUNC(EMBEDDED_BARE_REPO, WARN) \
/* infos (reported as warnings, but ignored by default) */ \
FUNC(GITMODULES_PARSE, INFO) \
FUNC(GITIGNORE_SYMLINK, INFO) \
diff --git a/setup.c b/setup.c
index 04ce33cdcd..2600548776 100644
--- a/setup.c
+++ b/setup.c
@@ -336,6 +336,10 @@ int get_common_dir_noenv(struct strbuf *sb, const char *gitdir)
* - either a HEAD symlink or a HEAD file that is formatted as
* a proper "ref:", or a regular file HEAD that has a properly
* formatted sha1 object name.
+ *
+ * fsck.c checks for bare repositories in trees using similar rules, but a
+ * duplicated implementation. If these are changed, the correspnding code in
+ * fsck.c should change too.
*/
int is_git_directory(const char *suspect)
{
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index de50c0ea01..a65827bc03 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -563,6 +563,42 @@ dot-backslash-case .\\\\.GIT\\\\foobar
dotgit-case-backslash .git\\\\foobar
EOF
+test_expect_success "fsck notices bare repo" '
+(
+ mkdir -p embedded-bare-repo/bare &&
+ git init embedded-bare-repo &&
+ (
+ cd embedded-bare-repo/bare &&
+ echo content >HEAD &&
+ mkdir refs/ objects/ &&
+ echo content >refs/foo &&
+ echo content >objects/foo &&
+ git add . &&
+ git commit -m base &&
+ bad_tree=$(git rev-parse HEAD:bare) &&
+ git fsck 2>out &&
+ test_i18ngrep "warning.*tree $bad_tree: embeddedBareRepo: contains bare repository" out
+ )
+)'
+
+test_expect_success "fsck notices bare repo with odd casing" '
+(
+ mkdir -p embedded-bare-repo-case/bare &&
+ git init embedded-bare-repo-case &&
+ (
+ cd embedded-bare-repo-case/bare &&
+ echo content >heAD &&
+ mkdir Refs/ objectS/ &&
+ echo content >Refs/foo &&
+ echo content >objectS/foo &&
+ git add . &&
+ git commit -m base &&
+ bad_tree=$(git rev-parse HEAD:bare) &&
+ git fsck 2>out &&
+ test_i18ngrep "warning.*tree $bad_tree: embeddedBareRepo: contains bare repository" out
+ )
+)'
+
test_expect_success 'fsck allows .Ňit' '
(
git init not-dotgit &&
base-commit: 805e0a68082a217f0112db9ee86a022227a9c81b
--
2.33.GIT
next prev parent reply other threads:[~2022-04-06 23:22 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-06 22:43 Bare repositories in the working tree are a security risk Glen Choo
2022-04-06 23:22 ` Glen Choo [this message]
2022-04-07 12:42 ` [PATCH] fsck: detect bare repos in trees and warn Johannes Schindelin
2022-04-07 13:21 ` Derrick Stolee
2022-04-07 14:14 ` Ævar Arnfjörð Bjarmason
2022-04-14 20:02 ` Glen Choo
2022-04-15 12:46 ` Ævar Arnfjörð Bjarmason
2022-04-07 15:11 ` Junio C Hamano
2022-04-13 22:24 ` Glen Choo
2022-04-07 13:12 ` Ævar Arnfjörð Bjarmason
2022-04-07 15:20 ` Junio C Hamano
2022-04-07 18:38 ` Bare repositories in the working tree are a security risk John Cai
2022-04-07 21:24 ` brian m. carlson
2022-04-07 21:53 ` Justin Steven
2022-04-07 22:10 ` brian m. carlson
2022-04-07 22:40 ` rsbecker
2022-04-08 5:54 ` Junio C Hamano
2022-04-14 0:03 ` Junio C Hamano
2022-04-14 0:04 ` Glen Choo
2022-04-13 23:44 ` Glen Choo
2022-04-13 20:37 ` Glen Choo
2022-04-13 23:36 ` Junio C Hamano
2022-04-14 16:41 ` Glen Choo
2022-04-14 17:35 ` Junio C Hamano
2022-04-14 18:19 ` Junio C Hamano
2022-04-15 21:33 ` Glen Choo
2022-04-15 22:17 ` Junio C Hamano
2022-04-16 0:52 ` Taylor Blau
2022-04-15 22:43 ` Glen Choo
2022-04-15 20:13 ` Junio C Hamano
2022-04-15 23:45 ` Glen Choo
2022-04-15 23:59 ` Glen Choo
2022-04-16 1:00 ` Taylor Blau
2022-04-16 1:18 ` Junio C Hamano
2022-04-16 1:30 ` Taylor Blau
2022-04-16 0:34 ` Glen Choo
2022-04-16 0:41 ` Glen Choo
2022-04-16 1:28 ` Taylor Blau
2022-04-21 18:25 ` Emily Shaffer
2022-04-21 18:29 ` Emily Shaffer
2022-04-21 18:47 ` Junio C Hamano
2022-04-21 18:54 ` Taylor Blau
2022-04-21 19:09 ` Taylor Blau
2022-04-21 21:01 ` Emily Shaffer
2022-04-21 21:22 ` Taylor Blau
2022-04-29 23:57 ` Glen Choo
2022-04-30 1:14 ` Taylor Blau
2022-05-02 19:39 ` Glen Choo
2022-05-02 14:05 ` Philip Oakley
2022-05-02 18:50 ` Junio C Hamano
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