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 6C6A843FD1F; Tue, 25 Aug 2026 14:25:40 +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=1787667942; cv=none; b=fXvVsNvFewPgXaKiLdayWGqLbYrrjcE1L2ViP2JY4Ibwu7cXAwlDD1WIn7tH9YakYzePg8XvKFCG0dnkn6UzdbtTL91+74K6y100H8n02je4FggELS6ho0qLmn+Rk343qTb3xujGVMd/OugUkKErgveRAopF1vRafm6YV9Wn2KY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787667942; c=relaxed/simple; bh=dK1n0kahTudmPAQEH5o5eu+skcIU4UJ839qrMPRvaZE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I0Fyi98wd0qMedLz/0oHZLZ7DXRbCV1eyq5vWdFp0Za6TdMcY66dItX0w4nXhfnLbcIIy6SCLbwTFq+k9f5TEqjasweQ7kqTMiFNlM3q16h0WAkmAwm73lm21tWlKgUIGu+8rA3Htz8ljujeREeiXc9yAzt1rezBXo2j0jlHj0k= 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=TbO2WR2/; 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="TbO2WR2/" 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=FIGrtRBtyoISaXPlqwZ8Fz3tQRiiUUr6mm9yzBGQJLw=; b=TbO2WR2/9aBy98QDPkZDi2aHpw Hi+gYIlswhh1Z3s46ubxLoDejuW7TXDmasAYw9ZRdN9HUSfGD+AdAkjS6UXVnN126C02phl6OOwsf 9VIzOJ5j+kOdnK7LPDwKIqHoH0k6D8LXgI8Y1fGOUxaIS7ITb4PfXPEtSzN3SxBu5BYhYsSRKIMpU 02qQ9YMdLneN+17T0QfvSpUZIWaO1cAmrg1hQ+9gxfFoJ088IWoAHOZ9u0V+r9fygtejj1Pe8kMuf nvS1pFr93lvSQE72Bk0SCpIwhmciR9z6pCLIW4n/cJ9PkrY19vNZVM/ugzm63YOQkNiEbP8UHFqiJ uhfaFNpw==; 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 1wys5l-000N8C-0D; Tue, 25 Aug 2026 16:25:33 +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 v2 02/11] bpf: Refuse caller-supplied keyrings when the bpf one is active Date: Tue, 25 Aug 2026 16:25:21 +0200 Message-ID: <20260825142530.1329706-3-daniel@iogearbox.net> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260825142530.1329706-1-daniel@iogearbox.net> References: <20260825142530.1329706-1-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 1.4.3/28103/Tue Aug 25 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 --- .../admin-guide/kernel-parameters.txt | 8 +++++ include/linux/bpf.h | 6 ++++ kernel/bpf/keys.c | 5 ++++ kernel/bpf/verifier.c | 29 ++++++++++++------- 4 files changed, 37 insertions(+), 11 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 62b095f7f524..571f7792a5c4 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 dc4d3a33158a..60cb85295c89 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 3be8d51d35ac..a93a8dc427d8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21018,21 +21018,28 @@ 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 (attr->keyring_id == VERIFY_USE_BPF_KEYRING) { - key = bpf_lookup_keyring(); - if (!key) { - verbose(env, "the bpf keyring is empty or has not been restricted\n"); - return -ENOKEY; - } - } else if (system_keyring_id_check(attr->keyring_id) == 0) { + if (!system_keyring_id_check(attr->keyring_id)) { key = bpf_lookup_system_key(attr->keyring_id); } else { - key = bpf_lookup_user_key(attr->keyring_id, 0); + if (attr->keyring_id != VERIFY_USE_BPF_KEYRING) { + if (bpf_keyring_enforced()) { + verbose(env, "caller-supplied keyring refused, use bpf keyring\n"); + return -EPERM; + } + key = bpf_lookup_user_key(attr->keyring_id, 0); + } else { + key = bpf_lookup_keyring(); + } } if (!key) { - verbose(env, "cannot resolve signing keyring with keyring_id %d\n", - attr->keyring_id); - return -EINVAL; + if (attr->keyring_id == VERIFY_USE_BPF_KEYRING) { + verbose(env, "the bpf keyring is empty or has not been restricted\n"); + return -ENOKEY; + } else { + verbose(env, "cannot resolve signing keyring with keyring_id %d\n", + attr->keyring_id); + return -EINVAL; + } } sig = kvmemdup_bpfptr(usig, attr->signature_size); -- 2.43.0