From patchwork Wed Aug 10 16:59:28 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 12940815 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0CC3C00140 for ; Wed, 10 Aug 2022 17:01:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233044AbiHJRBO (ORCPT ); Wed, 10 Aug 2022 13:01:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232685AbiHJRBK (ORCPT ); Wed, 10 Aug 2022 13:01:10 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A65960F6; Wed, 10 Aug 2022 10:01:09 -0700 (PDT) Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4M2x673NVnz67vrS; Thu, 11 Aug 2022 01:01:03 +0800 (CST) Received: from roberto-ThinkStation-P620.huawei.com (10.204.63.22) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 10 Aug 2022 19:01:05 +0200 From: Roberto Sassu To: , , , , , , , , , , , , , , , , , , , CC: , , , , , , Roberto Sassu Subject: [PATCH v10 5/9] bpf: Add bpf_lookup_*_key() and bpf_key_put() kfuncs Date: Wed, 10 Aug 2022 18:59:28 +0200 Message-ID: <20220810165932.2143413-6-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220810165932.2143413-1-roberto.sassu@huawei.com> References: <20220810165932.2143413-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.63.22] X-ClientProxiedBy: lhrpeml100005.china.huawei.com (7.191.160.25) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org Add the bpf_lookup_user_key(), bpf_lookup_system_key() and bpf_key_put() kfuncs, to respectively search a key with a given serial and flags, obtain a key from a pre-determined ID defined in include/linux/verification.h, and cleanup. Signed-off-by: Roberto Sassu --- include/linux/bpf.h | 6 ++ kernel/trace/bpf_trace.c | 146 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 152 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index a82f8c559ae2..d415e5e97551 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2573,4 +2573,10 @@ static inline void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype) {} static inline void bpf_cgroup_atype_put(int cgroup_atype) {} #endif /* CONFIG_BPF_LSM */ +#ifdef CONFIG_KEYS +struct bpf_key { + struct key *key; + bool has_ref; +}; +#endif /* CONFIG_KEYS */ #endif /* _LINUX_BPF_H */ diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 68e5cdd24cef..a607bb0be738 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -20,6 +20,8 @@ #include #include #include +#include +#include #include @@ -1181,6 +1183,150 @@ static const struct bpf_func_proto bpf_get_func_arg_cnt_proto = { .arg1_type = ARG_PTR_TO_CTX, }; +#ifdef CONFIG_KEYS +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "kfuncs which will be used in BPF programs"); + +/** + * bpf_lookup_user_key - lookup a key by its serial + * @serial: key serial + * @flags: lookup-specific flags + * + * Search a key with a given *serial* and the provided *flags*. The + * returned key, if found, has the reference count incremented by + * one, and is stored in a bpf_key structure, returned to the caller. + * The bpf_key structure must be passed to bpf_key_put() when done + * with it, so that the key reference count is decremented and the + * bpf_key structure is freed. + * + * Permission checks are deferred to the time the key is used by + * one of the available key-specific kfuncs. + * + * Set *flags* with 1, to attempt creating a requested special + * keyring (e.g. session keyring), if it doesn't yet exist. Set + * *flags* with 2 to lookup a key without waiting for the key + * construction, and to retrieve uninstantiated keys (keys without + * data attached to them). + * + * Return: a bpf_key pointer with a valid key pointer if the key is found, a + * NULL pointer otherwise. + */ +struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags) +{ + key_ref_t key_ref; + struct bpf_key *bkey; + + /* Keep in sync with include/linux/key.h. */ + if (flags & ~(KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL)) + return NULL; + + /* + * Permission check is deferred until actual kfunc using the key, + * since here the intent of the caller is not yet known. + * + * We cannot trust the caller to provide the needed permission as + * argument, since nothing prevents the caller from using the + * obtained key for a different purpose than the one declared. + */ + key_ref = lookup_user_key(serial, flags, KEY_DEFER_PERM_CHECK); + if (IS_ERR(key_ref)) + return NULL; + + bkey = kmalloc(sizeof(*bkey), GFP_ATOMIC); + if (!bkey) { + key_put(key_ref_to_ptr(key_ref)); + return NULL; + } + + bkey->key = key_ref_to_ptr(key_ref); + bkey->has_ref = true; + + return bkey; +} + +/** + * bpf_lookup_system_key - lookup a key by a system-defined ID + * @id: key ID + * + * Obtain a bpf_key structure with a key pointer set to the passed key ID. + * The key pointer is marked as invalid, to prevent bpf_key_put() from + * attempting to decrement the key reference count on that pointer. The key + * pointer set in such way is currently understood only by + * verify_pkcs7_signature(). + * + * Set *id* to one of the values defined in include/linux/verification.h: + * 0 for the primary keyring (immutable keyring of system keys); 1 for both + * the primary and secondary keyring (where keys can be added only if they + * are vouched for by existing keys in those keyrings); 2 for the platform + * keyring (primarily used by the integrity subsystem to verify a kexec'ed + * kerned image and, possibly, the initramfs signature). + * + * Return: a bpf_key pointer with an invalid key pointer set from the + * pre-determined ID on success, a NULL pointer otherwise + */ +struct bpf_key *bpf_lookup_system_key(u64 id) +{ + struct bpf_key *bkey; + + /* Keep in sync with defs in include/linux/verification.h. */ + if (id > (unsigned long)VERIFY_USE_PLATFORM_KEYRING) + return NULL; + + bkey = kmalloc(sizeof(*bkey), GFP_ATOMIC); + if (!bkey) + return NULL; + + bkey->key = (struct key *)(unsigned long)id; + bkey->has_ref = false; + + return bkey; +} + +/** + * bpf_key_put - decrement key reference count if key is valid and free bpf_key + * @bkey: bpf_key structure + * + * Decrement the reference count of the key inside *bkey*, if the pointer + * is valid, and free *bkey*. + */ +void bpf_key_put(struct bpf_key *bkey) +{ + if (bkey->has_ref) + key_put(bkey->key); + + kfree(bkey); +} + +__diag_pop(); + +BTF_SET8_START(key_sig_kfunc_set) +BTF_ID_FLAGS(func, bpf_lookup_user_key, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_lookup_system_key, KF_ACQUIRE | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_key_put, KF_RELEASE) +BTF_SET8_END(key_sig_kfunc_set) + +static const struct btf_kfunc_id_set bpf_key_sig_kfunc_set = { + .owner = THIS_MODULE, + .set = &key_sig_kfunc_set, +}; + +static int __init bpf_key_sig_kfuncs_init(void) +{ + int ret; + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, + &bpf_key_sig_kfunc_set); + if (!ret) + return 0; + + return register_btf_kfunc_id_set(BPF_PROG_TYPE_LSM, + &bpf_key_sig_kfunc_set); +} + +late_initcall(bpf_key_sig_kfuncs_init); +#endif /* CONFIG_KEYS */ + static const struct bpf_func_proto * bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) {