Package: release.debian.org
Severity: normal
Tags: bullseye
User: release.debian.org@packages.debian.org
Usertags: pu
X-Debbugs-Cc: tang@packages.debian.org
Control: affects -1 + src:tang
This is the bullseye version of #1040646
[ Reason ]
Fix https://security-tracker.debian.org/tracker/CVE-2023-1672 for
Debian 11 ("bullseye"), tagged "no-dsa (minor)" by the security team.
The problem of creating key material without restrictive file
permissions probably existed upstream since always. Up to and including
Debian 10 ("buster") however, this situation was caught by enforcing
restrictive permissions on the key directory.
With Debian 11 ("bullseye") a change in the creation of that directory
caused it to be created with a too permissive mode.
[ Impact ]
Without the change being accepted, the directory that holds the private
key would stay world-readable. Also this would continue to put users at
risk who configured a different key directory but did not enforce
restrictive access permissions.
[ Tests ]
No automated tests I'm aware of. Of course I did a manual test, and the
outcome matched the expectations.
[ Risks ]
The changes are small and rather straight-forward. I'd be surprised if
they introduce problems.
[ Checklist ]
[x] *all* changes are documented in the d/changelog
[x] I reviewed all changes and I approve them
[x] attach debdiff against the package in oldstable
[x] the issue is verified as fixed in unstable (14.1)
[ Changes ]
* Assert restrictive permissions of the key directory in Debian's
postinst.
For regular users and new instaaltions.
* Upstream's change to create the key file with restrictive
permissions.
Mostly for users who configure a different key directory.
* Recommend a key rotation in setups where this seems wise, add
some details in NEWS.Debian.
* Make the key rotation program executable as it should always
have been.
Regards,
Christoph
diff -Nru tang-8/debian/changelog tang-8/debian/changelog
--- tang-8/debian/changelog 2021-12-16 20:47:10.000000000 +0100
+++ tang-8/debian/changelog 2023-07-08 12:41:29.000000000 +0200
@@ -1,3 +1,14 @@
+tang (8-3+deb11u2) bullseye; urgency=high
+
+ * Fix CVE-2023-1672:
+ - Cherry-pick "Fix race condition when creating/rotating keys"
+ - Assert restrictive permissions on tang's key directory
+ In existing multi-user bullseye installations, rotating the keys
+ is suggested.
+ * Make the tangd-rotate-keys program executable
+
+ -- Christoph Biedl <debian.axhn@manchmal.in-ulm.de> Sat, 08 Jul 2023 12:41:29 +0200
+
tang (8-3+deb11u1) bullseye-security; urgency=high
* Fix data leak [CVE-2021-4076]
diff -Nru tang-8/debian/patches/bullseye/1686750800.v13-3-g8dbbed1.fix-race-condition-when-creating-rotating-keys-123.patch tang-8/debian/patches/bullseye/1686750800.v13-3-g8dbbed1.fix-race-condition-when-creating-rotating-keys-123.patch
--- tang-8/debian/patches/bullseye/1686750800.v13-3-g8dbbed1.fix-race-condition-when-creating-rotating-keys-123.patch 1970-01-01 01:00:00.000000000 +0100
+++ tang-8/debian/patches/bullseye/1686750800.v13-3-g8dbbed1.fix-race-condition-when-creating-rotating-keys-123.patch 2023-07-08 12:41:29.000000000 +0200
@@ -0,0 +1,73 @@
+Subject: Fix race condition when creating/rotating keys (#123)
+Origin: v13-3-g8dbbed1 <https://github.com/latchset/tang/commit/v13-3-g8dbbed1>
+Upstream-Author: Sergio Correia <scorreia@redhat.com>
+Date: Wed Jun 14 10:53:20 2023 -0300
+
+ When we create/rotate keys using either the tangd-keygen and
+ tangd-rotate-keys helpers, there is a small window between the
+ keys being created and then the proper ownership permissions being
+ set. This also happens when there are no keys and tang creates a
+ pair of keys itself.
+
+ In certain situations, such as the keys directory having wide open
+ permissions, a user with local access could exploit this race
+ condition and read the keys before they are set to more restrictive
+ permissions.
+
+ To prevent this issue, we now set the default umask to 0337 before
+ creating the files, so that they are already created with restrictive
+ permissions; afterwards, we set the proper ownership as usual.
+
+ Issue reported by Brian McDermott of CENSUS labs.
+
+ Fixes CVE-2023-1672
+
+
+ Reviewed-by: Sergio Arroutbi <sarroutb@redhat.com>
+ Signed-off-by: Sergio Correia <scorreia@redhat.com>
+
+--- a/src/keys.c
++++ b/src/keys.c
+@@ -17,6 +17,7 @@
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
++#include <sys/stat.h>
+ #include <stdlib.h>
+ #include <string.h>
+ #include <dirent.h>
+@@ -304,6 +305,9 @@
+ const char** hashes = supported_hashes();
+ const char* alg[] = {"ES512", "ECMR", NULL};
+ char path[PATH_MAX];
++
++ /* Set default umask for file creation. */
++ umask(0337);
+ for (int i = 0; alg[i] != NULL; i++) {
+ json_auto_t* jwk = jwk_generate(alg[i]);
+ if (!jwk) {
+--- a/src/tangd-keygen
++++ b/src/tangd-keygen
+@@ -27,6 +27,9 @@
+
+ [ $# -eq 3 ] && sig=$2 && exc=$3
+
++# Set default umask for file creation.
++umask 0337
++
+ jwe=`jose jwk gen -i '{"alg":"ES512"}'`
+ [ -z "$sig" ] && sig=`echo "$jwe" | jose jwk thp -i-`
+ echo "$jwe" > $1/$sig.jwk
+--- a/src/tangd-rotate-keys
++++ b/src/tangd-rotate-keys
+@@ -72,6 +72,10 @@
+
+ # Create a new set of keys.
+ DEFAULT_THP_HASH="S256"
++
++ # Set default umask for file creation.
++ umask 0337
++
+ for alg in "ES512" "ECMR"; do
+ json="$(printf '{"alg": "%s"}' "${alg}")"
+ jwe="$(jose jwk gen --input "${json}")"
diff -Nru tang-8/debian/patches/series tang-8/debian/patches/series
--- tang-8/debian/patches/series 2021-12-16 20:47:10.000000000 +0100
+++ tang-8/debian/patches/series 2023-07-08 12:41:29.000000000 +0200
@@ -13,5 +13,7 @@
debian/2021-04-19.non-usrmerged.patch
# cherry-picked after the stable release
-# CVE-2021-4076:
+# CVE-2021-4076
bullseye/1639480721.v10-9-ge82459f.keys-move-signing-part-out-of-find-by-thp-and-to-find-jws-81.patch
+# CVE-2023-1672
+bullseye/1686750800.v13-3-g8dbbed1.fix-race-condition-when-creating-rotating-keys-123.patch
diff -Nru tang-8/debian/rules tang-8/debian/rules
--- tang-8/debian/rules 2021-12-15 23:52:10.000000000 +0100
+++ tang-8/debian/rules 2023-07-08 12:41:29.000000000 +0200
@@ -10,4 +10,8 @@
override_dh_auto_install:
dh_auto_install --buildsystem=meson
rm -rf debian/tang/usr/share/licenses
- mkdir -p debian/tang/var/db/tang
+ mkdir -m0750 -p debian/tang/var/db/tang
+
+override_dh_fixperms:
+ chmod 755 debian/tang/usr/libexec/tangd-rotate-keys
+ dh_fixperms $@ -Xvar/db/tang
diff -Nru tang-8/debian/tang.NEWS tang-8/debian/tang.NEWS
--- tang-8/debian/tang.NEWS 1970-01-01 01:00:00.000000000 +0100
+++ tang-8/debian/tang.NEWS 2023-07-08 12:41:29.000000000 +0200
@@ -0,0 +1,13 @@
+tang (8-3+deb11u2) bullseye; urgency=high
+
+ * In existing bullseye installations, the key directory has world-
+ readable access permissions. If untrusted users have access to that
+ systems, administrators might want to do a key rotation after this
+ upgrade.
+
+ To do so, run: /usr/libexec/tangd-rotate-keys -v -d /var/db/tang
+
+ See https://manpages.debian.org/bookworm/tang-common/tangd-rotate-keys.1.en.html
+ for details.
+
+ -- Christoph Biedl <debian.axhn@manchmal.in-ulm.de> Sat, 08 Jul 2023 12:41:29 +0200
diff -Nru tang-8/debian/tang.postinst tang-8/debian/tang.postinst
--- tang-8/debian/tang.postinst 1970-01-01 01:00:00.000000000 +0100
+++ tang-8/debian/tang.postinst 2023-07-08 12:41:29.000000000 +0200
@@ -0,0 +1,19 @@
+#!/bin/sh
+
+set -e
+
+case "$1" in
+ configure)
+ # assert restrictive permissions on the key directory
+ chmod 0750 /var/db/tang
+ ;;
+ abort-upgrade | abort-remove | abort-deconfigure) ;;
+
+ *)
+ echo "postinst called with unknown argument '$1'" >&2
+ exit 1
+ ;;
+esac
+
+#DEBHELPER#
+exit 0
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