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ecdsautils: verify: fix signature verification (CVE-2022-24884)
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Matthias Schiffer 2022-05-05 18:02:38 +02:00 committed by GitHub
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7 changed files with 108 additions and 13 deletions
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LICENSE
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@ -1,7 +1,7 @@
The code of Project Gluon may be distributed under the following terms, unless
noted otherwise in individual files or subtrees.
Copyright (c) 2013-2021, Project Gluon
Copyright (c) 2013-2022, Project Gluon
All rights reserved.
Redistribution and use in source and binary forms, with or without

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README.md
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@ -21,7 +21,7 @@ the future development of Gluon.
Please refrain from using the `master` branch for anything else but development purposes!
Use the most recent release instead. You can list all releases by running `git tag`
and switch to one by running `git checkout v2021.1.1 && make update`.
and switch to one by running `git checkout v2021.1.2 && make update`.
If you're using the autoupdater, do not autoupdate nodes with anything but releases.
If you upgrade using random master commits the nodes *will break* eventually.

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docs/conf.py
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@ -20,11 +20,11 @@
# -- Project information -----------------------------------------------------
project = 'Gluon'
copyright = '2015-2021, Project Gluon'
copyright = '2015-2022, Project Gluon'
author = 'Project Gluon'
# The short X.Y version
version = '2021.1.1'
version = '2021.1.2'
# The full version, including alpha/beta/rc tags
release = version

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docs/releases/v2021.1.2.rst
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@ -1,9 +1,12 @@
Gluon 2021.1.2 (unreleased)
===========================
Gluon 2021.1.2
==============
Important notes
---------------
This release fixes a **critical security vulnerability** in Gluon's
autoupdater.
Upgrades to v2021.1 and later releases are only supported from releases v2018.2
and later. Migration code for upgrades from older versions has been removed to
simplify maintenance.
@ -23,11 +26,30 @@ log.
Bugfixes
--------
* **[SECURITY]** This release will fix a critical security vulnerability
* **[SECURITY]** Autoupdater: Fix signature verification
This bugfix has not been pushed to the public Gluon repository yet to avoid
disclosing information on the issue. A detailed advisory will be published at
the same time as the Gluon release.
A recently discovered issue (CVE-2022-24884) in the *ecdsautils* package
allows forgery of cryptographic signatures. This vulnerability can be
exploited to create a manifest accepted by the autoupdater without knowledge
of the signers' private keys. By intercepting nodes' connections to the update
server, such a manifest allows to distribute malicious firmware updates.
This is a **critical** vulnerability. All nodes with autoupdater must be
updated. Requiring multiple signatures for an update does *not* mitigate the
issue.
As a temporary workaround, the issue can be mitigated on individual nodes by
disabling the autoupdater via config mode or using the following commands::
uci set autoupdater.settings.enabled=0
uci commit autoupdater
A fixed firmware should be installed manually before enabling the autoupdater
again.
See security advisory `GHSA-qhcg-9ffp-78pw
<https://github.com/freifunk-gluon/ecdsautils/security/advisories/GHSA-qhcg-9ffp-78pw>`_
for further information on this vulnerability.
* **[SECURITY]** Config Mode: Prevent Cross-Site Request Forgery (CSRF)

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docs/site-example/site.conf
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@ -1,4 +1,4 @@
-- This is an example site configuration for Gluon v2021.1.1
-- This is an example site configuration for Gluon v2021.1.2
--
-- Take a look at the documentation located at
-- https://gluon.readthedocs.io/ for details.

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docs/user/getting_started.rst
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@ -8,7 +8,7 @@ Gluon's releases are managed using `Git tags`_. If you are just getting
started with Gluon we recommend to use the latest stable release of Gluon.
Take a look at the `list of gluon releases`_ and notice the latest release,
e.g. *v2021.1.1*. Always get Gluon using git and don't try to download it
e.g. *v2021.1.2*. Always get Gluon using git and don't try to download it
as a Zip archive as the archive will be missing version information.
Please keep in mind that there is no "default Gluon" build; a site configuration
@ -50,7 +50,7 @@ Building the images
-------------------
To build Gluon, first check out the repository. Replace *RELEASE* with the
version you'd like to checkout, e.g. *v2021.1.1*.
version you'd like to checkout, e.g. *v2021.1.2*.
::

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patches/packages/packages/0004-ecdsautils-verify-fix-signature-verification-CVE-2022-24884.patch Normal file
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@ -0,0 +1,73 @@
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Wed, 27 Apr 2022 19:01:39 +0200
Subject: ecdsautils: verify: fix signature verification (CVE-2022-24884)
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
diff --git a/utils/ecdsautils/Makefile b/utils/ecdsautils/Makefile
index 7f1c76f0301f56b0a88c1f6a1a0147397fde25c7..5ba893be69d40279cd6f5c9e544e941d0011f451 100644
--- a/utils/ecdsautils/Makefile
+++ b/utils/ecdsautils/Makefile
@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
PKG_NAME:=ecdsautils
PKG_VERSION:=0.3.2.20160630
-PKG_RELEASE:=1
+PKG_RELEASE:=2
PKG_REV:=07538893fb6c2a9539678c45f9dbbf1e4f222b46
PKG_MAINTAINER:=Matthias Schiffer <mschiffer@universe-factory.net>
PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
diff --git a/utils/ecdsautils/patches/0001-verify-fix-signature-verification-CVE-2022-24884.patch b/utils/ecdsautils/patches/0001-verify-fix-signature-verification-CVE-2022-24884.patch
new file mode 100644
index 0000000000000000000000000000000000000000..34d80cc201c0e87ca654c3def4fbbbddf622b0ba
--- /dev/null
+++ b/utils/ecdsautils/patches/0001-verify-fix-signature-verification-CVE-2022-24884.patch
@@ -0,0 +1,48 @@
+From 1d4b091abdf15ad7b2312535b5b95ad70f6dbd08 Mon Sep 17 00:00:00 2001
+Message-Id: <1d4b091abdf15ad7b2312535b5b95ad70f6dbd08.1651078760.git.mschiffer@universe-factory.net>
+From: Matthias Schiffer <mschiffer@universe-factory.net>
+Date: Wed, 20 Apr 2022 22:04:07 +0200
+Subject: [PATCH] verify: fix signature verification (CVE-2022-24884)
+
+Verify that r and s are non-zero. Without these checks, an all-zero
+signature is always considered valid.
+
+While it would be nicer to error out in ecdsa_verify_prepare_legacy()
+already, that would require users of libecdsautil to check a return value
+of the prepare step. To be safe, implement the fix in an API/ABI-compatible
+way that doesn't need changes to the users.
+---
+ src/lib/ecdsa.c | 10 ++++++++++
+ 1 file changed, 10 insertions(+)
+
+diff --git a/src/lib/ecdsa.c b/src/lib/ecdsa.c
+index 8cd7722be8cd..a661b56bd7c8 100644
+--- a/src/lib/ecdsa.c
++++ b/src/lib/ecdsa.c
+@@ -135,6 +135,12 @@ regenerate:
+ void ecdsa_verify_prepare_legacy(ecdsa_verify_context_t *ctx, const ecc_int256_t *hash, const ecdsa_signature_t *signature) {
+ ecc_int256_t w, u1, tmp;
+
++ if (ecc_25519_gf_is_zero(&signature->s) || ecc_25519_gf_is_zero(&signature->r)) {
++ // Signature is invalid, mark by setting ctx->r to an invalid value
++ memset(&ctx->r, 0, sizeof(ctx->r));
++ return;
++ }
++
+ ctx->r = signature->r;
+
+ ecc_25519_gf_recip(&w, &signature->s);
+@@ -149,6 +155,10 @@ bool ecdsa_verify_legacy(const ecdsa_verify_context_t *ctx, const ecc_25519_work
+ ecc_25519_work_t s2, work;
+ ecc_int256_t w, tmp;
+
++ // Signature was detected as invalid in prepare step
++ if (ecc_25519_gf_is_zero(&ctx->r))
++ return false;
++
+ ecc_25519_scalarmult(&s2, &ctx->u2, pubkey);
+ ecc_25519_add(&work, &ctx->s1, &s2);
+ ecc_25519_store_xy_legacy(&w, NULL, &work);
+--
+2.36.0
+