From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from www62.your-server.de (www62.your-server.de [213.133.104.62]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6FDFA3914FD; Fri, 28 Aug 2026 17:52:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.133.104.62 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787939558; cv=none; b=odB5eXCp5fC+Z15nARvLRGnZ+VuZyjEeF5qAuaUnzsfmvOAYSGQqxuz7XzoJk8C6S0VJoKfGD4vARxgPciMdLaM/R+DoyE3MWVN/IxyZY+igEgihJwUYT19/ngbw3JI/0o+peppSeu23XiLrOHbAbpFli1Ltc3A6yLWVcNA3GIQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787939558; c=relaxed/simple; bh=K4e3Bgnmza+1tOT3q4RCvmyMW7VH5CglEPFBipnHPLo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EY8DkVehtB1bPZavZY4k6qxG743tPBxvgTLrNS0kCDJAUJ2V0XXw3J7g1mrUrXIFF3vN3uVKRj8+FC76RmqHGqoJl5Mwh6nVPsWkrG1U0U9HTalAhFB8XiV9kdKGSHExhzZk2X68sUWrL9PzLOAWUIr9y0qLaXL7G7EViV++EAA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=iogearbox.net; spf=pass smtp.mailfrom=iogearbox.net; dkim=pass (2048-bit key) header.d=iogearbox.net header.i=@iogearbox.net header.b=K50b+L/S; arc=none smtp.client-ip=213.133.104.62 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=iogearbox.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=iogearbox.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=iogearbox.net header.i=@iogearbox.net header.b="K50b+L/S" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=iogearbox.net; s=default2302; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID; bh=HEm/EIc6Tx0BbH6j8VluF5TRjnLRV/IY+TjGi9Bzblo=; b=K50b+L/S3KaLfb0AnbyVISxhOn d0fG4a96001if3+Ix8Ykl8WqhUwIQwvbcgjCHs9kVFezqhn1wUy3SQa1eGvM7aq5RpjoFkuzyHFSn laG8s+H7H0xVOHi2HCiGc4KPB7zNXE9uVbhU6+4iQS0x9r6PukNPGoQ81DY6lIp9LlLRIrE6abIbu l6AQlnfKwcMTolO6efWS/upiZht5EatuL4MwtvOCpiRzs4xSdXc8xg7koZQkMUhwwT8YuosrbXwBr br6lFVXYxAqiK0prumt/tW6c09Dz3jQQq8M1VobjFilM1LszVt6zKnDFYMWMqdD/ShaVMR6Zn88W4 Peb4SsSA==; Received: from localhost ([127.0.0.1]) by www62.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96.2) (envelope-from ) id 1x00kg-0000aE-0k; Fri, 28 Aug 2026 19:52:30 +0200 From: Daniel Borkmann To: memxor@gmail.com Cc: brauner@kernel.org, kpsingh@kernel.org, ast@kernel.org, john.fastabend@gmail.com, a.s.protopopov@gmail.com, bpf@vger.kernel.org, dhowells@redhat.com, jarkko@kernel.org, keyrings@vger.kernel.org Subject: [PATCH bpf-next v4 02/11] bpf: Refuse caller-supplied keyrings when the bpf one is active Date: Fri, 28 Aug 2026 19:52:18 +0200 Message-ID: <20260828175227.1537793-3-daniel@iogearbox.net> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260828175227.1537793-1-daniel@iogearbox.net> References: <20260828175227.1537793-1-daniel@iogearbox.net> Precedence: bulk X-Mailing-List: keyrings@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Virus-Scanned: Clear (ClamAV 1.4.3/28106/Fri Aug 28 08:27:08 2026) Nothing changes for systems that do not use the bpf keyring. Without bpf.keyring_unsealed=1 a caller-supplied keyring behaves exactly as before, which also lets it serve as the staging step for software installed onto a running system whose signing key is not enrolled anywhere yet. Passing bpf.keyring_unsealed=1 states that the bpf keyring is the trust anchor for this boot, so from the first program load onwards a caller- supplied keyring is refused with -EPERM. Deriving this from the boot flag rather than from the keyring's runtime state keeps the decision immutable from userspace. Signed-off-by: Daniel Borkmann --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ include/linux/bpf.h | 6 ++++++ kernel/bpf/keys.c | 5 +++++ kernel/bpf/verifier.c | 10 +++++++--- 4 files changed, 26 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2beb61092bb3..e70fb15757d4 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -673,6 +673,14 @@ Kernel parameters keys. Once the keyring is restricted it becomes active and can be used for BPF program signature verification. + Setting this also means that the bpf keyring is the + only non-system keyring a loader may select for the + rest of the boot: caller-supplied user/session + keyrings are refused with -EPERM, whether or not + provisioning actually completed. The system keyrings + stay selectable. Leaving it unset keeps the prior + behaviour, where a caller-supplied keyring is allowed. + See Documentation/bpf/signing.rst bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 039674b2f875..3a7eb2185c35 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -3821,6 +3821,7 @@ struct bpf_key { struct bpf_key *bpf_lookup_user_key(s32 serial, u64 flags); struct bpf_key *bpf_lookup_system_key(u64 id); struct bpf_key *bpf_lookup_keyring(void); +bool bpf_keyring_enforced(void); void bpf_key_put(struct bpf_key *bkey); int bpf_verify_pkcs7_signature(const struct bpf_dynptr *data_p, const struct bpf_dynptr *sig_p, @@ -3846,6 +3847,11 @@ static inline struct bpf_key *bpf_lookup_keyring(void) return NULL; } +static inline bool bpf_keyring_enforced(void) +{ + return false; +} + static inline void bpf_key_put(struct bpf_key *bkey) { } diff --git a/kernel/bpf/keys.c b/kernel/bpf/keys.c index 08549b3220c1..bffc356839ac 100644 --- a/kernel/bpf/keys.c +++ b/kernel/bpf/keys.c @@ -18,6 +18,11 @@ static bool bpf_keyring_unsealed __ro_after_init; module_param_named(keyring_unsealed, bpf_keyring_unsealed, bool, 0444); MODULE_PARM_DESC(keyring_unsealed, "Leave the bpf keyring unsealed"); +bool bpf_keyring_enforced(void) +{ + return bpf_keyring_unsealed; +} + struct bpf_key *bpf_lookup_keyring(void) { struct bpf_key *bkey; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9c6624d2f5fb..2d50adf3800d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21019,12 +21019,16 @@ static int bpf_prog_verify_signature(struct bpf_verifier_env *env, if (!attr->signature_size || attr->signature_size > KMALLOC_MAX_CACHE_SIZE) return -EINVAL; - if (system_keyring_id_check(attr->keyring_id) == 0) + if (system_keyring_id_check(attr->keyring_id) == 0) { key = bpf_lookup_system_key(attr->keyring_id); - else if (attr->keyring_id == KEY_SPEC_BPF_KEYRING) + } else if (attr->keyring_id == KEY_SPEC_BPF_KEYRING) { key = bpf_lookup_keyring(); - else + } else if (bpf_keyring_enforced()) { + verbose(env, "caller-supplied keyring refused, use bpf keyring\n"); + return -EPERM; + } else { key = bpf_lookup_user_key(attr->keyring_id, 0); + } if (!key) { if (attr->keyring_id == KEY_SPEC_BPF_KEYRING) { verbose(env, "the bpf keyring is empty or has not been restricted\n"); -- 2.43.0