Re: [RFC PATCH security-next 2/4] hornet: Introduce sign-ebpf

On Fri, Mar 21, 2025 at 09:45:04AM -0700, Blaise Boscaccy wrote:

This introduces the sign-ebpf tool. It is very similar to the existing sign-file script, with one key difference, it will sign a file with with a signature computed off of arbitrary input data. This can used to sign an ebpf light skeleton loader program for verification via hornet.

Typical usage is to provide a payload containing the lskel ebpf syscall program binary and it's associated maps, which can be extracted from the auto-generated skel header.

Signed-off-by: Blaise Boscaccy bboscaccy@linux.microsoft.com

scripts/Makefile | 1 + scripts/hornet/Makefile | 5 + scripts/hornet/sign-ebpf.c | 420 +++++++++++++++++++++++++++++++++++++ 3 files changed, 426 insertions(+) create mode 100644 scripts/hornet/Makefile create mode 100644 scripts/hornet/sign-ebpf.c

diff --git a/scripts/Makefile b/scripts/Makefile index 46f860529df5e..a2cace05d7342 100644 --- a/scripts/Makefile +++ b/scripts/Makefile @@ -57,6 +57,7 @@ subdir-$(CONFIG_GENKSYMS) += genksyms subdir-$(CONFIG_GENDWARFKSYMS) += gendwarfksyms subdir-$(CONFIG_SECURITY_SELINUX) += selinux subdir-$(CONFIG_SECURITY_IPE) += ipe +subdir-$(CONFIG_SECURITY_HORNET) += hornet # Let clean descend into subdirs subdir- += basic dtc gdb kconfig mod diff --git a/scripts/hornet/Makefile b/scripts/hornet/Makefile new file mode 100644 index 0000000000000..ab71dbb8688e4 --- /dev/null +++ b/scripts/hornet/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +hostprogs-always-y := sign-ebpf

+HOSTCFLAGS_sign-ebpf.o = $(shell $(HOSTPKG_CONFIG) --cflags libcrypto 2> /dev/null) +HOSTLDLIBS_sign-ebpf = $(shell $(HOSTPKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto) diff --git a/scripts/hornet/sign-ebpf.c b/scripts/hornet/sign-ebpf.c new file mode 100644 index 0000000000000..ff98fddb79a15 --- /dev/null +++ b/scripts/hornet/sign-ebpf.c @@ -0,0 +1,420 @@ +/* Sign ebpf programs and skeletons using the given key.

• • This program is heavily based on the kernel's sign-file tool
• • with some minor additions to support the signing of eBPF lskels.
• • Copyright © 2014-2016 Red Hat, Inc. All Rights Reserved.
• • Copyright © 2015 Intel Corporation.
• • Copyright © 2016 Hewlett Packard Enterprise Development LP
• • Copyright © 2025 Microsoft Corporation.
• • Authors: David Howells dhowells@redhat.com

• •      David Woodhouse <dwmw2@infradead.org>
    

• •      Juerg Haefliger <juerg.haefliger@hpe.com>
    

• •      Blaise Boscaccy <bboscaccy@linux.microsoft.com>
    

I don't think that for new code ad-hoc authors lists in source code make any sense.

• • This program is free software; you can redistribute it and/or
• • modify it under the terms of the GNU Lesser General Public License
• • as published by the Free Software Foundation; either version 2.1
• • of the licence, or (at your option) any later version.

Redundant given SPDX.

• */

+#define _GNU_SOURCE +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <stdbool.h> +#include <string.h> +#include <getopt.h> +#include <err.h> +#include <arpa/inet.h> +#include <openssl/opensslv.h> +#include <openssl/bio.h> +#include <openssl/evp.h> +#include <openssl/pem.h> +#include <openssl/err.h> +#if OPENSSL_VERSION_MAJOR >= 3 +# define USE_PKCS11_PROVIDER +# include <openssl/provider.h> +# include <openssl/store.h> +#else +# if !defined(OPENSSL_NO_ENGINE) && !defined(OPENSSL_NO_DEPRECATED_3_0) +# define USE_PKCS11_ENGINE +# include <openssl/engine.h> +# endif +#endif +#include "../ssl-common.h"

+/*

• • Use CMS if we have openssl-1.0.0 or newer available - otherwise we have to
• • assume that it's not available and its header file is missing and that we
• • should use PKCS#7 instead. Switching to the older PKCS#7 format restricts
• • the options we have on specifying the X.509 certificate we want.
• • Further, older versions of OpenSSL don't support manually adding signers to
• • the PKCS#7 message so have to accept that we get a certificate included in
• • the signature message. Nor do such older versions of OpenSSL support
• • signing with anything other than SHA1 - so we're stuck with that if such is
• • the case.
• */

+#if defined(LIBRESSL_VERSION_NUMBER) || \

• OPENSSL_VERSION_NUMBER < 0x10000000L || \
• defined(OPENSSL_NO_CMS)

+#define USE_PKCS7 +#endif +#ifndef USE_PKCS7 +#include <openssl/cms.h> +#else +#include <openssl/pkcs7.h> +#endif

+struct module_signature {

• uint8_t algo; /* Public-key crypto algorithm [0] */
• uint8_t hash; /* Digest algorithm [0] */
• uint8_t id_type; /* Key identifier type [PKEY_ID_PKCS7] */
• uint8_t signer_len; /* Length of signer's name [0] */
• uint8_t key_id_len; /* Length of key identifier [0] */
• uint8_t __pad[3];
• uint32_t sig_len; /* Length of signature data */

+};

+#define PKEY_ID_PKCS7 2

+static char magic_number[] = "~eBPF signature appended~\n";

+static __attribute__((noreturn)) +void format(void) +{

• fprintf(stderr,

• "Usage: scripts/sign-ebpf [-dp] <hash algo> <key> <x509> <bin> <loader> [<dest>]\n");
  

• exit(2);

+}

+static const char *key_pass;

+static int pem_pw_cb(char *buf, int len, int w, void *v) +{

• int pwlen;
• if (!key_pass)

• return -1;
  

• pwlen = strlen(key_pass);
• if (pwlen >= len)

• return -1;
  

• strcpy(buf, key_pass);
• /* If it's wrong, don't keep trying it. */
• key_pass = NULL;
• return pwlen;

+}

+static EVP_PKEY *read_private_key_pkcs11(const char *private_key_name) +{

• EVP_PKEY *private_key = NULL;

+#ifdef USE_PKCS11_PROVIDER

• OSSL_STORE_CTX *store;
• if (!OSSL_PROVIDER_try_load(NULL, "pkcs11", true))

• ERR(1, "OSSL_PROVIDER_try_load(pkcs11)");
  

• if (!OSSL_PROVIDER_try_load(NULL, "default", true))

• ERR(1, "OSSL_PROVIDER_try_load(default)");
  

• store = OSSL_STORE_open(private_key_name, NULL, NULL, NULL, NULL);
• ERR(!store, "OSSL_STORE_open");
• while (!OSSL_STORE_eof(store)) {

• OSSL_STORE_INFO *info = OSSL_STORE_load(store);
  

• if (!info) {
  

• 	drain_openssl_errors(__LINE__, 0);
  

• 	continue;
  

• }
  

• if (OSSL_STORE_INFO_get_type(info) == OSSL_STORE_INFO_PKEY) {
  

• 	private_key = OSSL_STORE_INFO_get1_PKEY(info);
  

• 	ERR(!private_key, "OSSL_STORE_INFO_get1_PKEY");
  

• }
  

• OSSL_STORE_INFO_free(info);
  

• if (private_key)
  

• 	break;
  

• }
• OSSL_STORE_close(store);

+#elif defined(USE_PKCS11_ENGINE)

• ENGINE *e;
• ENGINE_load_builtin_engines();
• drain_openssl_errors(__LINE__, 1);
• e = ENGINE_by_id("pkcs11");
• ERR(!e, "Load PKCS#11 ENGINE");
• if (ENGINE_init(e))

• drain_openssl_errors(__LINE__, 1);
  

• else

• ERR(1, "ENGINE_init");
  

• if (key_pass)

• ERR(!ENGINE_ctrl_cmd_string(e, "PIN", key_pass, 0), "Set PKCS#11 PIN");
  

• private_key = ENGINE_load_private_key(e, private_key_name, NULL, NULL);
• ERR(!private_key, "%s", private_key_name);

+#else

• fprintf(stderr, "no pkcs11 engine/provider available\n");
• exit(1);

+#endif

• return private_key;

+}

+static EVP_PKEY *read_private_key(const char *private_key_name) +{

• if (!strncmp(private_key_name, "pkcs11:", 7)) {

• return read_private_key_pkcs11(private_key_name);
  

• } else {

• EVP_PKEY *private_key;
  

• BIO *b;
  

• b = BIO_new_file(private_key_name, "rb");
  

• ERR(!b, "%s", private_key_name);
  

• private_key = PEM_read_bio_PrivateKey(b, NULL, pem_pw_cb,
  

• 				      NULL);
  

• ERR(!private_key, "%s", private_key_name);
  

• BIO_free(b);
  

• return private_key;
  

• }

+}

+static X509 *read_x509(const char *x509_name) +{

• unsigned char buf[2];
• X509 *x509;
• BIO *b;
• int n;
• b = BIO_new_file(x509_name, "rb");
• ERR(!b, "%s", x509_name);
• /* Look at the first two bytes of the file to determine the encoding */
• n = BIO_read(b, buf, 2);
• if (n != 2) {

• if (BIO_should_retry(b)) {
  

• 	fprintf(stderr, "%s: Read wanted retry\n", x509_name);
  

• 	exit(1);
  

• }
  

• if (n >= 0) {
  

• 	fprintf(stderr, "%s: Short read\n", x509_name);
  

• 	exit(1);
  

• }
  

• ERR(1, "%s", x509_name);
  

• }
• ERR(BIO_reset(b) != 0, "%s", x509_name);
• if (buf[0] == 0x30 && buf[1] >= 0x81 && buf[1] <= 0x84)

• /* Assume raw DER encoded X.509 */
  

• x509 = d2i_X509_bio(b, NULL);
  

• else

• /* Assume PEM encoded X.509 */
  

• x509 = PEM_read_bio_X509(b, NULL, NULL, NULL);
  

• BIO_free(b);
• ERR(!x509, "%s", x509_name);
• return x509;

+}

+int main(int argc, char **argv) +{

• struct module_signature sig_info = { .id_type = PKEY_ID_PKCS7 };
• char *hash_algo = NULL;
• char *private_key_name = NULL, *raw_sig_name = NULL;
• char *x509_name, *bin_name, *loader_name, *dest_name;
• bool save_sig = false, replace_orig;
• bool sign_only = false;
• bool raw_sig = false;
• unsigned char buf[4096];
• unsigned long loader_size, sig_size;
• unsigned int use_signed_attrs;
• const EVP_MD *digest_algo;
• EVP_PKEY *private_key;

+#ifndef USE_PKCS7

• CMS_ContentInfo *cms = NULL;
• unsigned int use_keyid = 0;

+#else

• PKCS7 *pkcs7 = NULL;

+#endif

• X509 *x509;
• BIO *bd, *bm, *bl;
• int opt, n;
• OpenSSL_add_all_algorithms();
• ERR_load_crypto_strings();
• ERR_clear_error();
• key_pass = getenv("KBUILD_SIGN_PIN");

+#ifndef USE_PKCS7

• use_signed_attrs = CMS_NOATTR;

+#else

• use_signed_attrs = PKCS7_NOATTR;

+#endif

• do {

• opt = getopt(argc, argv, "sdpk");
  

• switch (opt) {
  

• case 's': raw_sig = true; break;
  

• case 'p': save_sig = true; break;
  

• case 'd': sign_only = true; save_sig = true; break;
  

+#ifndef USE_PKCS7

• case 'k': use_keyid = CMS_USE_KEYID; break;
  

+#endif

• case -1: break;
  

• default: format();
  

• }
  

• } while (opt != -1);
• argc -= optind;
• argv += optind;
• if (argc < 5 || argc > 6)

• format();
  

• if (raw_sig) {

• raw_sig_name = argv[0];
  

• hash_algo = argv[1];
  

• } else {

• hash_algo = argv[0];
  

• private_key_name = argv[1];
  

• }
• x509_name = argv[2];
• bin_name = argv[3];
• loader_name = argv[4];
• if (argc == 6 && strcmp(argv[4], argv[5]) != 0) {

• dest_name = argv[5];
  

• replace_orig = false;
  

• } else {

• ERR(asprintf(&dest_name, "%s.~signed~", loader_name) < 0,
  

•     "asprintf");
  

• replace_orig = true;
  

• }

+#ifdef USE_PKCS7

• if (strcmp(hash_algo, "sha1") != 0) {

• fprintf(stderr, "sign-file: %s only supports SHA1 signing\n",
  

• 	OPENSSL_VERSION_TEXT);
  

• exit(3);
  

• }

+#endif

• /* Open the bin file */
• bm = BIO_new_file(bin_name, "rb");
• ERR(!bm, "%s", bin_name);
• if (!raw_sig) {

• /* Read the private key and the X.509 cert the PKCS#7 message
  

•  * will point to.
  

•  */
  

• private_key = read_private_key(private_key_name);
  

• x509 = read_x509(x509_name);
  

• /* Digest the module data. */
  

• OpenSSL_add_all_digests();
  

• drain_openssl_errors(__LINE__, 0);
  

• digest_algo = EVP_get_digestbyname(hash_algo);
  

• ERR(!digest_algo, "EVP_get_digestbyname");
  

+#ifndef USE_PKCS7

• /* Load the signature message from the digest buffer. */
  

• cms = CMS_sign(NULL, NULL, NULL, NULL,
  

• 	       CMS_NOCERTS | CMS_PARTIAL | CMS_BINARY |
  

• 	       CMS_DETACHED | CMS_STREAM);
  

• ERR(!cms, "CMS_sign");
  

• ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo,
  

• 		     CMS_NOCERTS | CMS_BINARY |
  

• 		     CMS_NOSMIMECAP | use_keyid |
  

• 		     use_signed_attrs),
  

•     "CMS_add1_signer");
  

• ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) != 1,
  

•     "CMS_final");
  

+#else

• pkcs7 = PKCS7_sign(x509, private_key, NULL, bm,
  

• 		   PKCS7_NOCERTS | PKCS7_BINARY |
  

• 		   PKCS7_DETACHED | use_signed_attrs);
  

• ERR(!pkcs7, "PKCS7_sign");
  

+#endif

• if (save_sig) {
  

• 	char *sig_file_name;
  

• 	BIO *b;
  

• 	ERR(asprintf(&sig_file_name, "%s.p7s", bin_name) < 0,
  

• 	    "asprintf");
  

• 	b = BIO_new_file(sig_file_name, "wb");
  

• 	ERR(!b, "%s", sig_file_name);
  

+#ifndef USE_PKCS7

• 	ERR(i2d_CMS_bio_stream(b, cms, NULL, 0) != 1,
  

• 	    "%s", sig_file_name);
  

+#else

• 	ERR(i2d_PKCS7_bio(b, pkcs7) != 1,
  

• 	    "%s", sig_file_name);
  

+#endif

• 	BIO_free(b);
  

• }
  

• if (sign_only) {
  

• 	BIO_free(bm);
  

• 	return 0;
  

• }
  

• }
• /* Open the destination file now so that we can shovel the loader data

• * across as we read it.
  

• */
  

• bd = BIO_new_file(dest_name, "wb");
• ERR(!bd, "%s", dest_name);
• bl = BIO_new_file(loader_name, "rb");
• ERR(!bl, "%s", loader_name);
• /* Append the marker and the PKCS#7 message to the destination file */
• ERR(BIO_reset(bm) < 0, "%s", bin_name);
• ERR(BIO_reset(bl) < 0, "%s", loader_name);
• while ((n = BIO_read(bl, buf, sizeof(buf))),

•       n > 0) {
  

• ERR(BIO_write(bd, buf, n) < 0, "%s", dest_name);
  

• }
• BIO_free(bl);
• BIO_free(bm);
• ERR(n < 0, "%s", loader_name);
• loader_size = BIO_number_written(bd);
• if (!raw_sig) {

+#ifndef USE_PKCS7

• ERR(i2d_CMS_bio_stream(bd, cms, NULL, 0) != 1, "%s", dest_name);
  

+#else

• ERR(i2d_PKCS7_bio(bd, pkcs7) != 1, "%s", dest_name);
  

+#endif

• } else {

• BIO *b;
  

• /* Read the raw signature file and write the data to the
  

•  * destination file
  

•  */
  

• b = BIO_new_file(raw_sig_name, "rb");
  

• ERR(!b, "%s", raw_sig_name);
  

• while ((n = BIO_read(b, buf, sizeof(buf))), n > 0)
  

• 	ERR(BIO_write(bd, buf, n) < 0, "%s", dest_name);
  

• BIO_free(b);
  

• }
• sig_size = BIO_number_written(bd) - loader_size;
• sig_info.sig_len = htonl(sig_size);
• ERR(BIO_write(bd, &sig_info, sizeof(sig_info)) < 0, "%s", dest_name);
• ERR(BIO_write(bd, magic_number, sizeof(magic_number) - 1) < 0, "%s", dest_name);
• ERR(BIO_free(bd) != 1, "%s", dest_name);
• /* Finally, if we're signing in place, replace the original. */
• if (replace_orig)

• ERR(rename(dest_name, loader_name) < 0, "%s", dest_name);
  

• return 0;

+}

2.48.1

BR, Jarkko