This introduces the gen_sig tool. It creates a pkcs#7 signature of a data payload. Additionally it appends a signed attribute containing a set of hashes. Typical usage is to provide a payload containing the light skeleton ebpf syscall program binary and it's associated maps, which can be extracted from the auto-generated skeleton header. Signed-off-by: Blaise Boscaccy --- scripts/Makefile | 1 + scripts/hornet/Makefile | 5 + scripts/hornet/gen_sig.c | 392 ++++++++++++++++++++++++++++++++++++ scripts/hornet/write-sig.sh | 27 +++ 4 files changed, 425 insertions(+) create mode 100644 scripts/hornet/Makefile create mode 100644 scripts/hornet/gen_sig.c create mode 100755 scripts/hornet/write-sig.sh diff --git a/scripts/Makefile b/scripts/Makefile index 0941e5ce7b57..dea8ab91bbe4 100644 --- a/scripts/Makefile +++ b/scripts/Makefile @@ -63,6 +63,7 @@ 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 000000000000..3ee41e5e9a9f --- /dev/null +++ b/scripts/hornet/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +hostprogs-always-y := gen_sig + +HOSTCFLAGS_gen_sig.o = $(shell $(HOSTPKG_CONFIG) --cflags libcrypto 2> /dev/null) +HOSTLDLIBS_gen_sig = $(shell $(HOSTPKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto) diff --git a/scripts/hornet/gen_sig.c b/scripts/hornet/gen_sig.c new file mode 100644 index 000000000000..f966516ebc99 --- /dev/null +++ b/scripts/hornet/gen_sig.c @@ -0,0 +1,392 @@ +/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause + * + * Generate a signature for an eBPF program along with appending + * map hashes as signed attributes + * + * Copyright © 2025 Microsoft Corporation. + * + * Authors: Blaise Boscaccy + * + * 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. + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#if OPENSSL_VERSION_MAJOR >= 3 +# define USE_PKCS11_PROVIDER +# include +# include +#else +# if !defined(OPENSSL_NO_ENGINE) && !defined(OPENSSL_NO_DEPRECATED_3_0) +# define USE_PKCS11_ENGINE +# include +# endif +#endif +#include "../ssl-common.h" + +#define SHA256_LEN 32 +#define BUF_SIZE (1 << 15) // 32 KiB +#define MAX_HASHES 64 + +struct hash_spec { + char *file; + int index; +}; + +typedef struct { + ASN1_INTEGER *index; + ASN1_OCTET_STRING *hash; + +} HORNET_MAP; + +DECLARE_ASN1_FUNCTIONS(HORNET_MAP) +ASN1_SEQUENCE(HORNET_MAP) = { + ASN1_SIMPLE(HORNET_MAP, index, ASN1_INTEGER), + ASN1_SIMPLE(HORNET_MAP, hash, ASN1_OCTET_STRING) +} ASN1_SEQUENCE_END(HORNET_MAP); + +IMPLEMENT_ASN1_FUNCTIONS(HORNET_MAP) + +DEFINE_STACK_OF(HORNET_MAP) + +typedef struct { + STACK_OF(HORNET_MAP) * maps; +} MAP_SET; + +DECLARE_ASN1_FUNCTIONS(MAP_SET) +ASN1_SEQUENCE(MAP_SET) = { + ASN1_SET_OF(MAP_SET, maps, HORNET_MAP) +} ASN1_SEQUENCE_END(MAP_SET); + +IMPLEMENT_ASN1_FUNCTIONS(MAP_SET) + +#define DIE(...) do { fprintf(stderr, __VA_ARGS__); fputc('\n', stderr); \ + exit(EXIT_FAILURE); } while (0) + +static BIO *bio_open_wr(const char *path) +{ + BIO *b = BIO_new_file(path, "wb"); + + if (!b) { + perror(path); + ERR_print_errors_fp(stderr); + exit(EXIT_FAILURE); + } + return b; +} + +static void usage(const char *prog) +{ + fprintf(stderr, + "Usage:\n" + " %s --data content.bin --cert signer.crt --key signer.key [-pass pass]\n" + " --out newsig.p7b \n" + " --add FILE:index [--add FILE:index ...]\n", + prog); +} + +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); + + key_pass = NULL; + + return pwlen; +} + +static EVP_PKEY *read_private_key(const char *private_key_name) +{ + 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; +} + +static int sha256(const char *path, unsigned char out[SHA256_LEN], unsigned int *out_len) +{ + FILE *f; + int rc; + EVP_MD_CTX *ctx; + unsigned char buf[BUF_SIZE]; + size_t n; + unsigned int mdlen = 0; + + if (!path || !out) + return -1; + + f = fopen(path, "rb"); + if (!f) { + perror("fopen"); + return -2; + } + + ERR_load_crypto_strings(); + + rc = -3; + ctx = EVP_MD_CTX_new(); + if (!ctx) { + rc = -4; + goto done; + } + +#if OPENSSL_VERSION_NUMBER >= 0x30000000L + if (EVP_DigestInit_ex2(ctx, EVP_sha256(), NULL) != 1) { + rc = -5; + goto done; + } +#else + if (EVP_DigestInit_ex(ctx, EVP_sha256(), NULL) != 1) { + rc = -5; + goto done; + } +#endif + while ((n = fread(buf, 1, sizeof(buf), f)) > 0) { + if (EVP_DigestUpdate(ctx, buf, n) != 1) { + rc = -6; + goto done; + } + } + if (ferror(f)) { + rc = -7; + goto done; + } + + if (EVP_DigestFinal_ex(ctx, out, &mdlen) != 1) { + rc = -8; + goto done; + } + if (mdlen != SHA256_LEN) { + rc = -9; + goto done; + } + + if (out_len) + *out_len = mdlen; + rc = 0; + +done: + EVP_MD_CTX_free(ctx); + fclose(f); + ERR_free_strings(); + return rc; +} + +static void add_hash(MAP_SET *set, unsigned char *buffer, int buffer_len, int index) +{ + HORNET_MAP *map = NULL; + + map = HORNET_MAP_new(); + ASN1_INTEGER_set(map->index, index); + ASN1_OCTET_STRING_set(map->hash, buffer, buffer_len); + sk_HORNET_MAP_push(set->maps, map); +} + +int main(int argc, char **argv) +{ + const char *cert_path = NULL; + const char *key_path = NULL; + const char *data_path = NULL; + const char *out_path = NULL; + + X509 *signer; + EVP_PKEY *pkey; + BIO *data_in; + CMS_ContentInfo *cms_out; + struct hash_spec hashes[MAX_HASHES]; + int hash_count = 0; + int flags; + CMS_SignerInfo *si; + MAP_SET *set; + unsigned char hash_buffer[SHA256_LEN]; + unsigned int hash_len; + ASN1_OBJECT *oid; + unsigned char *der = NULL; + int der_len; + int err; + BIO *b_out; + int i; + char opt; + + const char *short_opts = "C:K:P:O:A:Sh"; + + static const struct option long_opts[] = { + {"cert", required_argument, 0, 'C'}, + {"key", required_argument, 0, 'K'}, + {"pass", required_argument, 0, 'P'}, + {"out", required_argument, 0, 'O'}, + {"data", required_argument, 0, 'D'}, + {"add", required_argument, 0, 'A'}, + {"help", no_argument, 0, 'h'}, + {0, 0, 0, 0} + }; + + while ((opt = getopt_long_only(argc, argv, short_opts, long_opts, NULL)) != -1) { + switch (opt) { + case 'C': + cert_path = optarg; + break; + case 'K': + key_path = optarg; + break; + case 'P': + key_pass = optarg; + break; + case 'O': + out_path = optarg; + break; + case 'D': + data_path = optarg; + break; + case 'A': + if (strchr(optarg, ':')) { + hashes[hash_count].file = strsep(&optarg, ":"); + hashes[hash_count].index = atoi(optarg); + hash_count++; + } else { + usage(argv[0]); + return EXIT_FAILURE; + } + } + } + + if (!cert_path || !key_path || !out_path || !data_path) { + usage(argv[0]); + return EXIT_FAILURE; + } + + OpenSSL_add_all_algorithms(); + ERR_load_crypto_strings(); + + signer = read_x509(cert_path); + ERR(!signer, "Load cert failed"); + + pkey = read_private_key(key_path); + ERR(!pkey, "Load key failed"); + + data_in = BIO_new_file(data_path, "rb"); + ERR(!data_in, "Load data failed"); + + cms_out = CMS_sign(NULL, NULL, NULL, NULL, + CMS_NOCERTS | CMS_PARTIAL | CMS_BINARY | CMS_DETACHED); + ERR(!cms_out, "create cms failed"); + + flags = CMS_NOCERTS | CMS_PARTIAL | CMS_BINARY | CMS_NOSMIMECAP | CMS_DETACHED; + + si = CMS_add1_signer(cms_out, signer, pkey, EVP_sha256(), flags); + ERR(!si, "add signer failed"); + + set = MAP_SET_new(); + set->maps = sk_HORNET_MAP_new_null(); + + for (i = 0; i < hash_count; i++) { + sha256(hashes[i].file, hash_buffer, &hash_len); + add_hash(set, hash_buffer, hash_len, hashes[i].index); + } + + oid = OBJ_txt2obj("2.25.316487325684022475439036912669789383960", 1); + if (!oid) { + ERR_print_errors_fp(stderr); + DIE("create oid failed"); + } + + der_len = ASN1_item_i2d((ASN1_VALUE *)set, &der, ASN1_ITEM_rptr(MAP_SET)); + CMS_signed_add1_attr_by_OBJ(si, oid, V_ASN1_SEQUENCE, der, der_len); + + err = CMS_final(cms_out, data_in, NULL, CMS_NOCERTS | CMS_BINARY); + ERR(!err, "cms final failed"); + + OPENSSL_free(der); + MAP_SET_free(set); + + b_out = bio_open_wr(out_path); + ERR(!b_out, "opening output path failed"); + + i2d_CMS_bio_stream(b_out, cms_out, NULL, 0); + + BIO_free(data_in); + BIO_free(b_out); + EVP_cleanup(); + ERR_free_strings(); + return 0; +} diff --git a/scripts/hornet/write-sig.sh b/scripts/hornet/write-sig.sh new file mode 100755 index 000000000000..7eaabe3bab9a --- /dev/null +++ b/scripts/hornet/write-sig.sh @@ -0,0 +1,27 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (c) 2025 Microsoft Corporation +# +# This program is free software; you can redistribute it and/or +# modify it under the terms of version 2 of the GNU General Public +# License as published by the Free Software Foundation. + +function usage() { + echo "Sample for rewriting an autogenerated eBPF lskel headers" + echo "with a new signature" + echo "" + echo "USAGE: header_file sig" + exit +} + +ARGC=$# + +EXPECTED_ARGS=2 + +if [ $ARGC -ne $EXPECTED_ARGS ] ; then + usage +else + SIG=$(xxd -p $2 | tr -d '\n' | sed 's/\(..\)/\\\\x\1/g') + sed '/const char opts_sig/,/;/c\\tstatic const char opts_sig[] __attribute__((__aligned__(8))) = "\\\n'"$(printf '%s\n' "$SIG")"'\";' $1 +fi -- 2.52.0