diff options
Diffstat (limited to 'debian/patches/CVE-2023-23946.patch')
| -rw-r--r-- | debian/patches/CVE-2023-23946.patch | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/debian/patches/CVE-2023-23946.patch b/debian/patches/CVE-2023-23946.patch new file mode 100644 index 0000000..17c51d7 --- /dev/null +++ b/debian/patches/CVE-2023-23946.patch @@ -0,0 +1,179 @@ +From fade728df1221598f42d391cf377e9e84a32053f Mon Sep 17 00:00:00 2001 +From: Patrick Steinhardt <ps@pks.im> +Date: Thu, 2 Feb 2023 11:54:34 +0100 +Subject: [PATCH] apply: fix writing behind newly created symbolic links + +When writing files git-apply(1) initially makes sure that none of the +files it is about to create are behind a symlink: + +``` + $ git init repo + Initialized empty Git repository in /tmp/repo/.git/ + $ cd repo/ + $ ln -s dir symlink + $ git apply - <<EOF + diff --git a/symlink/file b/symlink/file + new file mode 100644 + index 0000000..e69de29 + EOF + error: affected file 'symlink/file' is beyond a symbolic link +``` + +This safety mechanism is crucial to ensure that we don't write outside +of the repository's working directory. It can be fooled though when the +patch that is being applied creates the symbolic link in the first +place, which can lead to writing files in arbitrary locations. + +Fix this by checking whether the path we're about to create is +beyond a symlink or not. Tightening these checks like this should be +fine as we already have these precautions in Git as explained +above. Ideally, we should update the check we do up-front before +starting to reflect the computed changes to the working tree so that +we catch this case as well, but as part of embargoed security work, +adding an equivalent check just before we try to write out a file +should serve us well as a reasonable first step. + +Digging back into history shows that this vulnerability has existed +since at least Git v2.9.0. As Git v2.8.0 and older don't build on my +system anymore I cannot tell whether older versions are affected, as +well. + +Reported-by: Joern Schneeweisz <jschneeweisz@gitlab.com> +Signed-off-by: Patrick Steinhardt <ps@pks.im> +Signed-off-by: Junio C Hamano <gitster@pobox.com> +--- + apply.c | 27 ++++++++++++++ + t/t4115-apply-symlink.sh | 81 ++++++++++++++++++++++++++++++++++++++++ + 2 files changed, 108 insertions(+) + +diff --git a/apply.c b/apply.c +index 668b16e989..d80382c940 100644 +--- a/apply.c ++++ b/apply.c +@@ -4400,6 +4400,33 @@ static int create_one_file(struct apply_state *state, + if (state->cached) + return 0; + ++ /* ++ * We already try to detect whether files are beyond a symlink in our ++ * up-front checks. But in the case where symlinks are created by any ++ * of the intermediate hunks it can happen that our up-front checks ++ * didn't yet see the symlink, but at the point of arriving here there ++ * in fact is one. We thus repeat the check for symlinks here. ++ * ++ * Note that this does not make the up-front check obsolete as the ++ * failure mode is different: ++ * ++ * - The up-front checks cause us to abort before we have written ++ * anything into the working directory. So when we exit this way the ++ * working directory remains clean. ++ * ++ * - The checks here happen in the middle of the action where we have ++ * already started to apply the patch. The end result will be a dirty ++ * working directory. ++ * ++ * Ideally, we should update the up-front checks to catch what would ++ * happen when we apply the patch before we damage the working tree. ++ * We have all the information necessary to do so. But for now, as a ++ * part of embargoed security work, having this check would serve as a ++ * reasonable first step. ++ */ ++ if (path_is_beyond_symlink(state, path)) ++ return error(_("affected file '%s' is beyond a symbolic link"), path); ++ + res = try_create_file(state, path, mode, buf, size); + if (res < 0) + return -1; +diff --git a/t/t4115-apply-symlink.sh b/t/t4115-apply-symlink.sh +index 872fcda6cb..1acb7b2582 100755 +--- a/t/t4115-apply-symlink.sh ++++ b/t/t4115-apply-symlink.sh +@@ -44,4 +44,85 @@ test_expect_success 'apply --index symlink patch' ' + + ' + ++test_expect_success 'symlink setup' ' ++ ln -s .git symlink && ++ git add symlink && ++ git commit -m "add symlink" ++' ++ ++test_expect_success SYMLINKS 'symlink escape when creating new files' ' ++ test_when_finished "git reset --hard && git clean -dfx" && ++ ++ cat >patch <<-EOF && ++ diff --git a/symlink b/renamed-symlink ++ similarity index 100% ++ rename from symlink ++ rename to renamed-symlink ++ -- ++ diff --git /dev/null b/renamed-symlink/create-me ++ new file mode 100644 ++ index 0000000..039727e ++ --- /dev/null ++ +++ b/renamed-symlink/create-me ++ @@ -0,0 +1,1 @@ ++ +busted ++ EOF ++ ++ test_must_fail git apply patch 2>stderr && ++ cat >expected_stderr <<-EOF && ++ error: affected file ${SQ}renamed-symlink/create-me${SQ} is beyond a symbolic link ++ EOF ++ test_cmp expected_stderr stderr && ++ ! test_path_exists .git/create-me ++' ++ ++test_expect_success SYMLINKS 'symlink escape when modifying file' ' ++ test_when_finished "git reset --hard && git clean -dfx" && ++ touch .git/modify-me && ++ ++ cat >patch <<-EOF && ++ diff --git a/symlink b/renamed-symlink ++ similarity index 100% ++ rename from symlink ++ rename to renamed-symlink ++ -- ++ diff --git a/renamed-symlink/modify-me b/renamed-symlink/modify-me ++ index 1111111..2222222 100644 ++ --- a/renamed-symlink/modify-me ++ +++ b/renamed-symlink/modify-me ++ @@ -0,0 +1,1 @@ ++ +busted ++ EOF ++ ++ test_must_fail git apply patch 2>stderr && ++ cat >expected_stderr <<-EOF && ++ error: renamed-symlink/modify-me: No such file or directory ++ EOF ++ test_cmp expected_stderr stderr && ++ test_must_be_empty .git/modify-me ++' ++ ++test_expect_success SYMLINKS 'symlink escape when deleting file' ' ++ test_when_finished "git reset --hard && git clean -dfx && rm .git/delete-me" && ++ touch .git/delete-me && ++ ++ cat >patch <<-EOF && ++ diff --git a/symlink b/renamed-symlink ++ similarity index 100% ++ rename from symlink ++ rename to renamed-symlink ++ -- ++ diff --git a/renamed-symlink/delete-me b/renamed-symlink/delete-me ++ deleted file mode 100644 ++ index 1111111..0000000 100644 ++ EOF ++ ++ test_must_fail git apply patch 2>stderr && ++ cat >expected_stderr <<-EOF && ++ error: renamed-symlink/delete-me: No such file or directory ++ EOF ++ test_cmp expected_stderr stderr && ++ test_path_is_file .git/delete-me ++' ++ + test_done +-- +2.30.2 + |