From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2295C2E7BD4; Wed, 13 Aug 2025 20:55:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755118553; cv=none; b=NphwSE5PwiHRYlEr8sdYy6iS8k1WuA0FKweM4U72LzZTSxZzWsNQ/vg1YL+yixcsdNIUYyab3/qqhL42epkJYznvjTKAPb6vgsFkixQIueraNremUyrJCXVc3O+0f5utew8YFXVv5gP+JQxsUiQdfvuSvZQtkANLI5WpwvLkeEA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755118553; c=relaxed/simple; bh=kt1W0T6gZ4NsTNJJRE7jFQLra+UpfRhHrEgV9lmCcA0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e9pP0LNcsYbp1pX377qx+oSUwcRy9g6rVcb4kmvLcZWj5bwRVG0CnJ58WmrMj2uvybp1UrzvwpkPg7ZmVasqVF0Aho+5mtcTB8dPfTN4RtxlxTxpY4X6Lk/rmUnehHZWwci2+z6uVZURoQJsD/DaBybDCUqPrpsfqIwtdpIYc6w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nFgKU0B9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nFgKU0B9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0814C4CEED; Wed, 13 Aug 2025 20:55:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755118552; bh=kt1W0T6gZ4NsTNJJRE7jFQLra+UpfRhHrEgV9lmCcA0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nFgKU0B9y/J4YZxWfRKeRIaEQPZleUGM7jwK/HuzLN/9LSNdv+csm9VOmPwW6HquM zRE3ayfozNVY/Eb7iTkhvKMcBprQGs0ofAqqEHyu1+Xo5SDATYNXrYrv2Lb9fZpcQt 2+ze1Y2vYxvxB7xjuqK4rkKQ/Cdsr2kvnhabDFewkkcduJdCmjUKWxIkp2iwokeaCB pf70Xv4z7y4zbcAUzQlVzpNz/u14lWAEXsJb6vjRizKZTyXctYueM7/ua9OmrSQDxM B0jOG25jMPKYIpXEfezPa8Qatkv/qa0/6pzsRBgYLZMdce5zqHtZ5qal60s3pNNqy+ mqtSbaj6Ep8uw== From: KP Singh To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org Cc: bboscaccy@linux.microsoft.com, paul@paul-moore.com, kys@microsoft.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, KP Singh Subject: [PATCH v3 09/12] libbpf: Update light skeleton for signing Date: Wed, 13 Aug 2025 22:55:23 +0200 Message-ID: <20250813205526.2992911-10-kpsingh@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250813205526.2992911-1-kpsingh@kernel.org> References: <20250813205526.2992911-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit * The metadata map is created with as an exclusive map (with an excl_prog_hash) This restricts map access exclusively to the signed loader program, preventing tampering by other processes. * The map is then frozen, making it read-only from userspace. * BPF_OBJ_GET_INFO_BY_ID instructs the kernel to compute the hash of the metadata map (H') and store it in bpf_map->sha. * The loader is then loaded with the signature which is then verified by the kernel. The sekeleton currently uses the session keyring (KEY_SPEC_SESSION_KEYRING) by default but this can be overridden by the user of the skeleton. loading signed programs prebuilt into the kernel are not currently supported. These can supported by enabling BPF_OBJ_GET_INFO_BY_ID to be called from the kernel. Signed-off-by: KP Singh --- tools/lib/bpf/skel_internal.h | 75 +++++++++++++++++++++++++++++++++-- 1 file changed, 71 insertions(+), 4 deletions(-) diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h index 4d5fa079b5d6..0e8330b85735 100644 --- a/tools/lib/bpf/skel_internal.h +++ b/tools/lib/bpf/skel_internal.h @@ -13,10 +13,15 @@ #include #include #include +#include #include #include "bpf.h" #endif +#ifndef SHA256_DIGEST_LENGTH +#define SHA256_DIGEST_LENGTH 32 +#endif + #ifndef __NR_bpf # if defined(__mips__) && defined(_ABIO32) # define __NR_bpf 4355 @@ -64,6 +69,11 @@ struct bpf_load_and_run_opts { __u32 data_sz; __u32 insns_sz; const char *errstr; + void *signature; + __u32 signature_sz; + __s32 keyring_id; + void * excl_prog_hash; + __u32 excl_prog_hash_sz; }; long kern_sys_bpf(__u32 cmd, void *attr, __u32 attr_size); @@ -220,14 +230,19 @@ static inline int skel_map_create(enum bpf_map_type map_type, const char *map_name, __u32 key_size, __u32 value_size, - __u32 max_entries) + __u32 max_entries, + const void *excl_prog_hash, + __u32 excl_prog_hash_sz) { - const size_t attr_sz = offsetofend(union bpf_attr, map_extra); + const size_t attr_sz = offsetofend(union bpf_attr, excl_prog_hash); union bpf_attr attr; memset(&attr, 0, attr_sz); attr.map_type = map_type; + attr.excl_prog_hash = (unsigned long) excl_prog_hash; + attr.excl_prog_hash_size = excl_prog_hash_sz; + strncpy(attr.map_name, map_name, sizeof(attr.map_name)); attr.key_size = key_size; attr.value_size = value_size; @@ -300,6 +315,34 @@ static inline int skel_link_create(int prog_fd, int target_fd, return skel_sys_bpf(BPF_LINK_CREATE, &attr, attr_sz); } +static inline int skel_obj_get_info_by_fd(int fd) +{ + const size_t attr_sz = offsetofend(union bpf_attr, info); + __u8 sha[SHA256_DIGEST_LENGTH]; + struct bpf_map_info info = {}; + __u32 info_len = sizeof(info); + union bpf_attr attr; + + info.hash = (long) &sha; + info.hash_size = SHA256_DIGEST_LENGTH; + + memset(&attr, 0, attr_sz); + attr.info.bpf_fd = fd; + attr.info.info = (long) &info; + attr.info.info_len = info_len; + return skel_sys_bpf(BPF_OBJ_GET_INFO_BY_FD, &attr, attr_sz); +} + +static inline int skel_map_freeze(int fd) +{ + const size_t attr_sz = offsetofend(union bpf_attr, map_fd); + union bpf_attr attr; + + memset(&attr, 0, attr_sz); + attr.map_fd = fd; + + return skel_sys_bpf(BPF_MAP_FREEZE, &attr, attr_sz); +} #ifdef __KERNEL__ #define set_err #else @@ -308,12 +351,13 @@ static inline int skel_link_create(int prog_fd, int target_fd, static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts) { - const size_t prog_load_attr_sz = offsetofend(union bpf_attr, fd_array); + const size_t prog_load_attr_sz = offsetofend(union bpf_attr, keyring_id); const size_t test_run_attr_sz = offsetofend(union bpf_attr, test); int map_fd = -1, prog_fd = -1, key = 0, err; union bpf_attr attr; - err = map_fd = skel_map_create(BPF_MAP_TYPE_ARRAY, "__loader.map", 4, opts->data_sz, 1); + err = map_fd = skel_map_create(BPF_MAP_TYPE_ARRAY, "__loader.map", 4, opts->data_sz, 1, + opts->excl_prog_hash, opts->excl_prog_hash_sz); if (map_fd < 0) { opts->errstr = "failed to create loader map"; set_err; @@ -327,11 +371,34 @@ static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts) goto out; } +#ifndef __KERNEL__ + err = skel_map_freeze(map_fd); + if (err < 0) { + opts->errstr = "failed to freeze map"; + set_err; + goto out; + } + err = skel_obj_get_info_by_fd(map_fd); + if (err < 0) { + opts->errstr = "failed to fetch obj info"; + set_err; + goto out; + } +#endif + memset(&attr, 0, prog_load_attr_sz); attr.prog_type = BPF_PROG_TYPE_SYSCALL; attr.insns = (long) opts->insns; attr.insn_cnt = opts->insns_sz / sizeof(struct bpf_insn); attr.license = (long) "Dual BSD/GPL"; +#ifndef __KERNEL__ + attr.signature = (long) opts->signature; + attr.signature_size = opts->signature_sz; +#else + if (opts->signature || opts->signature_sz) + pr_warn("signatures are not supported from bpf_preload\n"); +#endif + attr.keyring_id = opts->keyring_id; memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog")); attr.fd_array = (long) &map_fd; attr.log_level = opts->ctx->log_level; -- 2.43.0