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bh=YJjYoiTj3WSsEa5+kzx49B/Y4qCMzV1a+UUijYo12BQ=; b=CF9WajvGcxT5rr8esgeijt2bGio37iTrU4G8M+Jtuk3uPlNsJGc1VdcscgnCngCTV9EZoa n7JcbBj9fiCOiUS3z5C0jbbB8Bznl541gTxbXfpBRwpcen/rfgKiUQ5KAAuNF4wiKLXOpc zcfaGrt7ObN0O6jFaAYWABySSmKgVww= X-MC-Unique: 5lfOiD3mN1imtGEcTBYA5A-1 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: Markus Armbruster , Michael Roth , Konstantin Kostiuk , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Subject: [PATCH 13/14] qga: add command line to block user authentication commands Date: Tue, 4 Jun 2024 16:32:41 +0100 Message-ID: <20240604153242.251334-14-berrange@redhat.com> In-Reply-To: <20240604153242.251334-1-berrange@redhat.com> References: <20240604153242.251334-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1717515216021100008 Historically there has been no default policy on command usage in the QEMU guest agent. A wide variety of commands have been added for various purposes * Co-ordinating host mgmt tasks (FS freezing, CPU hotplug, memory block hotplug) * Guest information querying (CPU stats, mount info, etc) * Arbitrary file read/write and command execution * User account auth setup (passwords, SSH keys) All of these have valid use cases, but they come with very different levels of risk to the guest OS. The commands supporting alteration of user authentication credentials are giving the guest agent client effectively unrestricted access to do anything at all in the guest OS by enabling them to subsequently access a user login shell. The guest agent client is the host OS, so in effect running the QEMU guest agent gives the host admin a trivial direct backdoor into the guest OS. In the absense of confidential computing, the host admin already has to be considered largely trustworthy, as they will typically have direct access to any guest RAM regardless. None the less, to limit their exposure, guest OS admins may choose to limit these commands by passing '--no-user-auth' / '-e' to QGA The --allowedrpcs / --blockedrpcs arguments take precedence over the --unrestricted arg (whether present or not), thus allowing fine tuning the defaults further. Signed-off-by: Daniel P. Berrang=C3=A9 --- qga/main.c | 15 +++++++++++++++ qga/qapi-schema.json | 5 ++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/qga/main.c b/qga/main.c index 66068ad535..0d792cd92e 100644 --- a/qga/main.c +++ b/qga/main.c @@ -88,6 +88,7 @@ struct GAConfig { GList *allowedrpcs; bool only_confidential; bool no_unrestricted; + bool no_user_auth; int daemonize; GLogLevelFlags log_level; int dumpconf; @@ -436,6 +437,16 @@ static bool ga_command_is_allowed(const QmpCommand *cm= d, GAState *state) allowed =3D false; } =20 + /* + * If user auth commands are not allowed that sets + * a new default, but an explicit allow/block list can + * override + */ + if (config->no_user_auth && + qmp_command_has_feature(cmd, QAPI_FEATURE_USER_AUTH)) { + allowed =3D false; + } + if (config->allowedrpcs) { /* * If an allow-list is given, this changes the fallback @@ -1220,6 +1231,7 @@ static void config_parse(GAConfig *config, int argc, = char **argv) { "retry-path", 0, NULL, 'r' }, { "confidential", 0, NULL, 'i' }, { "no-unrestricted", 0, NULL, 'u' }, + { "no-user-auth", 0, NULL, 'e' }, { NULL, 0, NULL, 0 } }; =20 @@ -1322,6 +1334,9 @@ static void config_parse(GAConfig *config, int argc, = char **argv) case 'u': config->no_unrestricted =3D true; break; + case 'e': + config->no_user_auth =3D true; + break; case 'h': usage(argv[0]); exit(EXIT_SUCCESS); diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json index a4f8653446..25068b8110 100644 --- a/qga/qapi-schema.json +++ b/qga/qapi-schema.json @@ -45,7 +45,10 @@ 'confidential', # Commands which allow unrestricted access to or # modification of guest files or execute arbitrary commands - 'unrestricted' + 'unrestricted', + # Commands which allow changes to user account + # authentication credentials (keys, passwords) + 'user-auth' ] } } =20 ## --=20 2.45.1