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 261E64766BC; Wed, 26 Aug 2026 16:41:48 +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=1787762541; cv=none; b=Df4sEH6TfFUGJaGtvLDIQP7dM2I0y5yYd4BZGjJhLtvnCRRDG0S9+GUDKL9w8X1TUV2HvvetdvFflNoa3APs6ny9RQXS8hY4bQTLQOEt67EQBAIl3wvF1k6YdJ1MHVasrecxznX9DbovAeDiGYu3qltpb7uUTLxXNt3hQSvB9ug= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787762541; c=relaxed/simple; bh=xHMKdcIzJKEWbW2/jUBUyyWXvn6DxzwImcsRNLqSJ6M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=psGhr7mVK9SHztb3u7n2uJsDZJASsS2dTnXPeDqmUU0X5QbG0DaOQPvgmuwdGoPj+bOfbAyz2wvtqLxlcHHhA2hYUDVJ+Dnx04r7D2f5g2WwlrM1ub714r8loQMxp87peqC5YwOeVi5S33MmkprD+sHPbiNjpXkulfAmNXCscH0= 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=Q1SLbL71; 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="Q1SLbL71" 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=m+kFZoFWIAnD1BHv0Tlk8apirdS/rn7WPtfbgpd7TQU=; b=Q1SLbL71zqpaJfhOSfm1bliuDo 0sTnHDsfd7oORr5gNNIaZ5HTI1lSg67Wv7HONDNKWHD8UPUVq5pS+uasw3LIGAH1vAnxTAJRwxIpP evBwspGZwGlvxl5qKlpMDbWg53scSKglW+Re/i2OY/JWMIq1U90S5UwkHq908N7ntCQkvhzKzRAd6 SpAsaa2WaOXCr1IWKh5XLVC9ATuOdvmlXW9INpfVl0mtg0YGnvtUFAojP+x67NoWj4IUQuZ/riGMe 6YuERFRmqAwBYRB6470nvrrr0MHkNPR3BPMeTzeyPk+UL07QDGF56IsrzxxyyZpiaj/L1BPHK0PCA SJVH8NhA==; 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 1wzGh0-000IKY-11; Wed, 26 Aug 2026 18:41:38 +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 v3 01/11] bpf, keys: Add a bpf keyring for program signature validation Date: Wed, 26 Aug 2026 18:41:26 +0200 Message-ID: <20260826164136.1400997-2-daniel@iogearbox.net> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260826164136.1400997-1-daniel@iogearbox.net> References: <20260826164136.1400997-1-daniel@iogearbox.net> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Virus-Scanned: Clear (ClamAV 1.4.3/28104/Wed Aug 26 08:24:01 2026) BPF program signatures can currently be verified against one of the system keyrings (builtin, secondary, platform) or against an arbitrary user/session caller-supplied keyring named through keyring_id. There is nothing in between: the system keyrings need a kernel rebuild or a vouched-for enrollment to rotate a key, while a caller-supplied keyring is fully controlled by the loader and therefore carries no trust on its own (unless explicitly combined with BPF LSM to protect against key tampering). Add a dedicated bpf keyring to fill that gap, modelled after the dm-verity keyring which was added in commit 033724b1c627 ("dm-verity: add dm-verity keyring") and which can eventually be used also via systemd through the same enrollment method as in dm-verity's case. It is selected with the new KEY_SPEC_BPF_KEYRING special key id and gives an operator a place to enroll a BPF-only signing key at boot, specifically scoped to BPF program loading and nothing else in the kernel's trust hierarchy. The id is reserved from the KEY_SPEC space so that the latter is not linked into any process keyring, and lookup_user_key() resolves KEY_SPEC_BPF_KEYRING constant instead of having to look it up via /proc/keys first. By default the keyring is sealed empty at init. Systems that want to provision keys pass bpf.keyring_unsealed=1, which leaves the keyring open for the initrd to add keys to. The keyring is only ever consulted once it is both non-empty and restricted. An unrestricted keyring is ignored. Signed-off-by: Daniel Borkmann --- .../admin-guide/kernel-parameters.txt | 8 +++ include/linux/bpf.h | 7 ++ include/linux/key.h | 2 + include/uapi/linux/keyctl.h | 1 + kernel/bpf/Makefile | 3 + kernel/bpf/keys.c | 68 +++++++++++++++++++ kernel/bpf/verifier.c | 14 +++- security/keys/process_keys.c | 25 +++++++ 8 files changed, 126 insertions(+), 2 deletions(-) create mode 100644 kernel/bpf/keys.c diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index e4643634a9b1..2beb61092bb3 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -667,6 +667,14 @@ Kernel parameters See Documentation/admin-guide/bootconfig.rst + bpf.keyring_unsealed= + [BPF] When set to 1, leave the bpf keyring unsealed + after initialization so that userspace can provision + keys. Once the keyring is restricted it becomes active + and can be used for BPF program signature verification. + + See Documentation/bpf/signing.rst + bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) bttv.radio= Most important insmod options are available as kernel args too. diff --git a/include/linux/bpf.h b/include/linux/bpf.h index b3cd28d9e3b5..62b095f7f524 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1735,6 +1735,7 @@ enum bpf_sig_keyring { BPF_SIG_KEYRING_SECONDARY, BPF_SIG_KEYRING_PLATFORM, BPF_SIG_KEYRING_USER, + BPF_SIG_KEYRING_BPF, }; struct bpf_prog_aux { @@ -3819,6 +3820,7 @@ struct bpf_key { #if defined(CONFIG_KEYS) && defined(CONFIG_BPF_SYSCALL) 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); 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, @@ -3839,6 +3841,11 @@ static inline struct bpf_key *bpf_lookup_system_key(u64 id) return NULL; } +static inline struct bpf_key *bpf_lookup_keyring(void) +{ + return NULL; +} + static inline void bpf_key_put(struct bpf_key *bkey) { } diff --git a/include/linux/key.h b/include/linux/key.h index 81b8f05c6898..bd10fe45819d 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -440,6 +440,8 @@ extern key_ref_t keyring_search(key_ref_t keyring, extern int keyring_restrict(key_ref_t keyring, const char *type, const char *restriction); +extern void key_register_bpf_keyring(struct key *keyring); + extern struct key *key_lookup(key_serial_t id); static inline key_serial_t key_serial(const struct key *key) diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h index 4c8884eea808..fa85b9760391 100644 --- a/include/uapi/linux/keyctl.h +++ b/include/uapi/linux/keyctl.h @@ -24,6 +24,7 @@ #define KEY_SPEC_GROUP_KEYRING -6 /* - key ID for GID-specific keyring */ #define KEY_SPEC_REQKEY_AUTH_KEY -7 /* - key ID for assumed request_key auth key */ #define KEY_SPEC_REQUESTOR_KEYRING -8 /* - key ID for request_key() dest keyring */ +#define KEY_SPEC_BPF_KEYRING -9 /* - key ID for the BPF-specific keyring */ /* request-key default keyrings */ #define KEY_REQKEY_DEFL_NO_CHANGE -1 diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 90255d80e5be..9a92c348bbda 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -27,6 +27,9 @@ obj-$(CONFIG_BPF_SYSCALL) += offload.o obj-$(CONFIG_BPF_SYSCALL) += net_namespace.o obj-$(CONFIG_BPF_SYSCALL) += tcx.o endif +ifeq ($(CONFIG_KEYS),y) +obj-$(CONFIG_BPF_SYSCALL) += keys.o +endif ifeq ($(CONFIG_PERF_EVENTS),y) obj-$(CONFIG_BPF_SYSCALL) += stackmap.o endif diff --git a/kernel/bpf/keys.c b/kernel/bpf/keys.c new file mode 100644 index 000000000000..08549b3220c1 --- /dev/null +++ b/kernel/bpf/keys.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2026 Isovalent */ + +#include +#include +#include +#include +#include +#include +#include + +#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "bpf." + +static struct key *bpf_keyring; + +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"); + +struct bpf_key *bpf_lookup_keyring(void) +{ + struct bpf_key *bkey; + + if (!bpf_keyring) + return NULL; + if (!READ_ONCE(bpf_keyring->keys.nr_leaves_on_tree) || + !READ_ONCE(bpf_keyring->restrict_link)) + return NULL; + + bkey = kmalloc_obj(*bkey); + if (!bkey) + return NULL; + + bkey->key = bpf_keyring; + bkey->has_ref = false; + return bkey; +} + +static int __init bpf_keyring_init(void) +{ + struct key *keyring; + + keyring = keyring_alloc(".bpf", + GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, + current_cred(), KEY_POS_SEARCH | + KEY_USR_VIEW | KEY_USR_READ | + KEY_USR_WRITE | KEY_USR_SEARCH | + KEY_USR_SETATTR, KEY_ALLOC_NOT_IN_QUOTA, + NULL, NULL); + if (IS_ERR(keyring)) { + pr_err("bpf: cannot allocate bpf keyring: %ld\n", + PTR_ERR(keyring)); + return 0; + } + if (!bpf_keyring_unsealed && + keyring_restrict(make_key_ref(keyring, true), NULL, NULL)) { + pr_err("bpf: cannot seal bpf keyring\n"); + key_revoke(keyring); + key_put(keyring); + return 0; + } + + bpf_keyring = keyring; + key_register_bpf_keyring(keyring); + return 0; +} +late_initcall(bpf_keyring_init); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e036ae20bf6b..b45d201c2535 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -20981,6 +20982,8 @@ static enum bpf_sig_keyring bpf_classify_keyring(s32 keyring_id) return BPF_SIG_KEYRING_SECONDARY; case (s32)(unsigned long)VERIFY_USE_PLATFORM_KEYRING: return BPF_SIG_KEYRING_PLATFORM; + case KEY_SPEC_BPF_KEYRING: + return BPF_SIG_KEYRING_BPF; default: return BPF_SIG_KEYRING_USER; } @@ -21016,10 +21019,17 @@ 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 (attr->keyring_id == KEY_SPEC_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) { key = bpf_lookup_system_key(attr->keyring_id); - else + } else { key = bpf_lookup_user_key(attr->keyring_id, 0); + } if (!key) { verbose(env, "cannot resolve signing keyring with keyring_id %d\n", attr->keyring_id); diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index a63c46bb2d14..44358388e395 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -22,6 +22,9 @@ /* Session keyring create vs join semaphore */ static DEFINE_MUTEX(key_session_mutex); +/* BPF keyring reachable through KEY_SPEC_BPF_KEYRING */ +static struct key *bpf_keyring __ro_after_init; + /* The root user's tracking struct */ struct key_user root_key_user = { .usage = REFCOUNT_INIT(3), @@ -590,6 +593,20 @@ bool lookup_user_key_possessed(const struct key *key, return key == match_data->raw_data; } +/** + * key_register_bpf_keyring - Publish the BPF keyring for KEY_SPEC_BPF_KEYRING + * @keyring: The keyring to publish + * + * Make @keyring reachable by userspace through the KEY_SPEC_BPF_KEYRING + * special key ID, so that provisioning it does not require scraping its + * serial out of /proc/keys first. Called once, from an initcall, and never + * undone. + */ +void key_register_bpf_keyring(struct key *keyring) +{ + bpf_keyring = keyring; +} + /* * Look up a key ID given us by userspace with a given permissions mask to get * the key it refers to. @@ -741,6 +758,14 @@ key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags, key_ref = make_key_ref(key, 1); break; + case KEY_SPEC_BPF_KEYRING: + key = bpf_keyring; + if (!key) + goto error; + __key_get(key); + key_ref = make_key_ref(key, 0); + break; + default: key_ref = ERR_PTR(-EINVAL); if (id < 1) -- 2.43.0