From: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org,
kpsingh@kernel.org, bboscaccy@linux.microsoft.com,
paul@paul-moore.com, kys@microsoft.com, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org,
James.Bottomley@hansenpartnership.com, wufan@linux.microsoft.com
Subject: [RFC 2/2] libbpf: Add hash chain signing support to light skeletons.
Date: Tue, 9 Sep 2025 09:20:59 -0700 [thread overview]
Message-ID: <20250909162345.569889-3-bboscaccy@linux.microsoft.com> (raw)
In-Reply-To: <20250909162345.569889-1-bboscaccy@linux.microsoft.com>
This patch introduces a hash chain signing support for light-skeleton
assets. A new flag '-M' is added which constructs a hash chain with
the loader program and the target payload.
Signed-off-by: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
---
tools/bpf/bpftool/gen.c | 25 +++++++++++++++++++++++++
tools/bpf/bpftool/main.c | 8 +++++++-
tools/bpf/bpftool/main.h | 1 +
tools/bpf/bpftool/sign.c | 17 ++++++++++++++---
tools/lib/bpf/libbpf.h | 3 ++-
tools/lib/bpf/skel_internal.h | 6 +++++-
6 files changed, 54 insertions(+), 6 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index ab6fc86598ad3..e660fbc701c5d 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -699,6 +699,9 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
if (sign_progs)
opts.gen_hash = true;
+ if (sign_maps)
+ opts.sign_maps = true;
+
err = bpf_object__gen_loader(obj, &opts);
if (err)
return err;
@@ -793,6 +796,8 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
if (sign_progs) {
sopts.insns = opts.insns;
sopts.insns_sz = opts.insns_sz;
+ sopts.data = opts.data;
+ sopts.data_sz = opts.data_sz;
sopts.excl_prog_hash = prog_sha;
sopts.excl_prog_hash_sz = sizeof(prog_sha);
sopts.signature = sig_buf;
@@ -821,6 +826,13 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
\n\
\";\n");
+ if (sign_maps) {
+ codegen("\
+ \n\
+ static const int opts_signature_maps[1] __attribute__((__aligned__(8))) = {0}; \n\
+ ");
+ }
+
codegen("\
\n\
opts.signature = (void *)opts_sig; \n\
@@ -829,6 +841,19 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
opts.excl_prog_hash_sz = sizeof(opts_excl_hash) - 1; \n\
opts.keyring_id = KEY_SPEC_SESSION_KEYRING; \n\
");
+ if (sign_maps) {
+ codegen("\
+ \n\
+ opts.signature_maps = (void *)opts_signature_maps; \n\
+ opts.signature_maps_sz = 1; \n\
+ ");
+ } else {
+ codegen("\
+ \n\
+ opts.signature_maps = (void *)NULL; \n\
+ opts.signature_maps_sz = 0; \n\
+ ");
+ }
}
codegen("\
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index fc25bb390ec71..287e8205494cb 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -34,6 +34,7 @@ bool use_loader;
struct btf *base_btf;
struct hashmap *refs_table;
bool sign_progs;
+bool sign_maps;
const char *private_key_path;
const char *cert_path;
@@ -477,7 +478,7 @@ int main(int argc, char **argv)
bin_name = "bpftool";
opterr = 0;
- while ((opt = getopt_long(argc, argv, "VhpjfLmndSi:k:B:l",
+ while ((opt = getopt_long(argc, argv, "VhpjfLmndSMi:k:B:l",
options, NULL)) >= 0) {
switch (opt) {
case 'V':
@@ -527,6 +528,11 @@ int main(int argc, char **argv)
sign_progs = true;
use_loader = true;
break;
+ case 'M':
+ sign_maps = true;
+ sign_progs = true;
+ use_loader = true;
+ break;
case 'k':
private_key_path = optarg;
break;
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index f921af3cda87f..805c3d87a1330 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -92,6 +92,7 @@ extern bool use_loader;
extern struct btf *base_btf;
extern struct hashmap *refs_table;
extern bool sign_progs;
+extern bool sign_maps;
extern const char *private_key_path;
extern const char *cert_path;
diff --git a/tools/bpf/bpftool/sign.c b/tools/bpf/bpftool/sign.c
index f0b5dd10a46b2..d5514b7d2b82d 100644
--- a/tools/bpf/bpftool/sign.c
+++ b/tools/bpf/bpftool/sign.c
@@ -22,6 +22,7 @@
#include <errno.h>
#include <bpf/skel_internal.h>
+#include <bpf/libbpf_internal.h>
#include "main.h"
@@ -129,8 +130,18 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
long actual_sig_len = 0;
X509 *x509 = NULL;
int err = 0;
-
- bd_in = BIO_new_mem_buf(opts->insns, opts->insns_sz);
+ unsigned char hash[SHA256_DIGEST_LENGTH * 2];
+ unsigned char term[SHA256_DIGEST_LENGTH];
+
+ if (sign_maps) {
+ libbpf_sha256(opts->insns, opts->insns_sz, hash, SHA256_DIGEST_LENGTH);
+ libbpf_sha256(opts->data, opts->data_sz, hash + SHA256_DIGEST_LENGTH,
+ SHA256_DIGEST_LENGTH);
+ libbpf_sha256(hash, sizeof(hash), term, sizeof(term));
+ bd_in = BIO_new_mem_buf(term, sizeof(term));
+ } else {
+ bd_in = BIO_new_mem_buf(opts->insns, opts->insns_sz);
+ }
if (!bd_in) {
err = -ENOMEM;
goto cleanup;
@@ -171,7 +182,7 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
EVP_Digest(opts->insns, opts->insns_sz, opts->excl_prog_hash,
&opts->excl_prog_hash_sz, EVP_sha256(), NULL);
- bd_out = BIO_new(BIO_s_mem());
+ bd_out = BIO_new(BIO_s_mem());
if (!bd_out) {
err = -ENOMEM;
goto cleanup;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 7cad8470d9ebe..aad0288cd05e3 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1827,9 +1827,10 @@ struct gen_loader_opts {
__u32 data_sz;
__u32 insns_sz;
bool gen_hash;
+ bool sign_maps;
};
-#define gen_loader_opts__last_field gen_hash
+#define gen_loader_opts__last_field sign_maps
LIBBPF_API int bpf_object__gen_loader(struct bpf_object *obj,
struct gen_loader_opts *opts);
diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index 5b6d1b09dc8a6..c25a4f1308e44 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -74,6 +74,8 @@ struct bpf_load_and_run_opts {
__u32 keyring_id;
void * excl_prog_hash;
__u32 excl_prog_hash_sz;
+ const int *signature_maps;
+ __u32 signature_maps_sz;
};
long kern_sys_bpf(__u32 cmd, void *attr, __u32 attr_size);
@@ -351,7 +353,7 @@ static inline int skel_map_freeze(int 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, keyring_id);
+ const size_t prog_load_attr_sz = offsetofend(union bpf_attr, signature_maps_size);
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;
@@ -394,6 +396,8 @@ static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts)
#ifndef __KERNEL__
attr.signature = (long) opts->signature;
attr.signature_size = opts->signature_sz;
+ attr.signature_maps = (long) opts->signature_maps;
+ attr.signature_maps_size = opts->signature_maps_sz;
#else
if (opts->signature || opts->signature_sz)
pr_warn("signatures are not supported from bpf_preload\n");
--
2.48.1
prev parent reply other threads:[~2025-09-09 16:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 16:20 [RFC 0/2] BPF signature hash chains Blaise Boscaccy
2025-09-09 16:20 ` [RFC 1/2] bpf: Add hash chain signature support for arbitrary maps Blaise Boscaccy
2025-09-09 16:20 ` Blaise Boscaccy [this message]
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