linux/scripts/sign-file.c

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/* Sign a module file using the given key.
*
* Copyright © 2014-2015 Red Hat, Inc. All Rights Reserved.
* Copyright © 2015 Intel Corporation.
*
* Authors: David Howells <dhowells@redhat.com>
* David Woodhouse <dwmw2@infradead.org>
*
* 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 <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>
#include <openssl/engine.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 OPENSSL_VERSION_NUMBER < 0x10000000L
#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[] = "~Module signature appended~\n";
static __attribute__((noreturn))
void format(void)
{
fprintf(stderr,
"Usage: scripts/sign-file [-dp] <hash algo> <key> <x509> <module> [<dest>]\n");
exit(2);
}
static void display_openssl_errors(int l)
{
const char *file;
char buf[120];
int e, line;
if (ERR_peek_error() == 0)
return;
fprintf(stderr, "At main.c:%d:\n", l);
while ((e = ERR_get_error_line(&file, &line))) {
ERR_error_string(e, buf);
fprintf(stderr, "- SSL %s: %s:%d\n", buf, file, line);
}
}
static void drain_openssl_errors(void)
{
const char *file;
int line;
if (ERR_peek_error() == 0)
return;
while (ERR_get_error_line(&file, &line)) {}
}
#define ERR(cond, fmt, ...) \
do { \
bool __cond = (cond); \
display_openssl_errors(__LINE__); \
if (__cond) { \
err(1, fmt, ## __VA_ARGS__); \
} \
} while(0)
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;
}
int main(int argc, char **argv)
{
struct module_signature sig_info = { .id_type = PKEY_ID_PKCS7 };
char *hash_algo = NULL;
char *private_key_name, *x509_name, *module_name, *dest_name;
bool save_sig = false, replace_orig;
bool sign_only = false;
unsigned char buf[4096];
unsigned long module_size, sig_size;
unsigned int use_signed_attrs;
const EVP_MD *digest_algo;
EVP_PKEY *private_key;
#ifndef USE_PKCS7
CMS_ContentInfo *cms;
unsigned int use_keyid = 0;
#else
PKCS7 *pkcs7;
#endif
X509 *x509;
BIO *b, *bd = NULL, *bm;
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, "dpk");
switch (opt) {
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 < 4 || argc > 5)
format();
hash_algo = argv[0];
private_key_name = argv[1];
x509_name = argv[2];
module_name = argv[3];
if (argc == 5) {
dest_name = argv[4];
replace_orig = false;
} else {
ERR(asprintf(&dest_name, "%s.~signed~", module_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
/* Read the private key and the X.509 cert the PKCS#7 message
* will point to.
*/
if (!strncmp(private_key_name, "pkcs11:", 7)) {
ENGINE *e;
ENGINE_load_builtin_engines();
drain_openssl_errors();
e = ENGINE_by_id("pkcs11");
ERR(!e, "Load PKCS#11 ENGINE");
if (ENGINE_init(e))
drain_openssl_errors();
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 {
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);
}
b = BIO_new_file(x509_name, "rb");
ERR(!b, "%s", x509_name);
x509 = d2i_X509_bio(b, NULL); /* Binary encoded X.509 */
if (!x509) {
ERR(BIO_reset(b) != 1, "%s", x509_name);
x509 = PEM_read_bio_X509(b, NULL, NULL, NULL); /* PEM encoded X.509 */
if (x509)
drain_openssl_errors();
}
BIO_free(b);
ERR(!x509, "%s", x509_name);
/* Open the destination file now so that we can shovel the module data
* across as we read it.
*/
if (!sign_only) {
bd = BIO_new_file(dest_name, "wb");
ERR(!bd, "%s", dest_name);
}
/* Digest the module data. */
OpenSSL_add_all_digests();
display_openssl_errors(__LINE__);
digest_algo = EVP_get_digestbyname(hash_algo);
ERR(!digest_algo, "EVP_get_digestbyname");
bm = BIO_new_file(module_name, "rb");
ERR(!bm, "%s", module_name);
#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,
PKCS#7: Appropriately restrict authenticated attributes and content type A PKCS#7 or CMS message can have per-signature authenticated attributes that are digested as a lump and signed by the authorising key for that signature. If such attributes exist, the content digest isn't itself signed, but rather it is included in a special authattr which then contributes to the signature. Further, we already require the master message content type to be pkcs7_signedData - but there's also a separate content type for the data itself within the SignedData object and this must be repeated inside the authattrs for each signer [RFC2315 9.2, RFC5652 11.1]. We should really validate the authattrs if they exist or forbid them entirely as appropriate. To this end: (1) Alter the PKCS#7 parser to reject any message that has more than one signature where at least one signature has authattrs and at least one that does not. (2) Validate authattrs if they are present and strongly restrict them. Only the following authattrs are permitted and all others are rejected: (a) contentType. This is checked to be an OID that matches the content type in the SignedData object. (b) messageDigest. This must match the crypto digest of the data. (c) signingTime. If present, we check that this is a valid, parseable UTCTime or GeneralTime and that the date it encodes fits within the validity window of the matching X.509 cert. (d) S/MIME capabilities. We don't check the contents. (e) Authenticode SP Opus Info. We don't check the contents. (f) Authenticode Statement Type. We don't check the contents. The message is rejected if (a) or (b) are missing. If the message is an Authenticode type, the message is rejected if (e) is missing; if not Authenticode, the message is rejected if (d) - (f) are present. The S/MIME capabilities authattr (d) unfortunately has to be allowed to support kernels already signed by the pesign program. This only affects kexec. sign-file suppresses them (CMS_NOSMIMECAP). The message is also rejected if an authattr is given more than once or if it contains more than one element in its set of values. (3) Add a parameter to pkcs7_verify() to select one of the following restrictions and pass in the appropriate option from the callers: (*) VERIFYING_MODULE_SIGNATURE This requires that the SignedData content type be pkcs7-data and forbids authattrs. sign-file sets CMS_NOATTR. We could be more flexible and permit authattrs optionally, but only permit minimal content. (*) VERIFYING_FIRMWARE_SIGNATURE This requires that the SignedData content type be pkcs7-data and requires authattrs. In future, this will require an attribute holding the target firmware name in addition to the minimal set. (*) VERIFYING_UNSPECIFIED_SIGNATURE This requires that the SignedData content type be pkcs7-data but allows either no authattrs or only permits the minimal set. (*) VERIFYING_KEXEC_PE_SIGNATURE This only supports the Authenticode SPC_INDIRECT_DATA content type and requires at least an SpcSpOpusInfo authattr in addition to the minimal set. It also permits an SPC_STATEMENT_TYPE authattr (and an S/MIME capabilities authattr because the pesign program doesn't remove these). (*) VERIFYING_KEY_SIGNATURE (*) VERIFYING_KEY_SELF_SIGNATURE These are invalid in this context but are included for later use when limiting the use of X.509 certs. (4) The pkcs7_test key type is given a module parameter to select between the above options for testing purposes. For example: echo 1 >/sys/module/pkcs7_test_key/parameters/usage keyctl padd pkcs7_test foo @s </tmp/stuff.pkcs7 will attempt to check the signature on stuff.pkcs7 as if it contains a firmware blob (1 being VERIFYING_FIRMWARE_SIGNATURE). Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Marcel Holtmann <marcel@holtmann.org> Reviewed-by: David Woodhouse <David.Woodhouse@intel.com>
2015-08-05 14:22:27 +00:00
CMS_NOCERTS | CMS_BINARY | CMS_NOSMIMECAP |
use_keyid | use_signed_attrs),
"CMS_add1_signer");
ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) < 0,
"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;
ERR(asprintf(&sig_file_name, "%s.p7s", module_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) < 0,
"%s", sig_file_name);
#else
ERR(i2d_PKCS7_bio(b, pkcs7) < 0,
"%s", sig_file_name);
#endif
BIO_free(b);
}
if (sign_only)
return 0;
/* Append the marker and the PKCS#7 message to the destination file */
ERR(BIO_reset(bm) < 0, "%s", module_name);
while ((n = BIO_read(bm, buf, sizeof(buf))),
n > 0) {
ERR(BIO_write(bd, buf, n) < 0, "%s", dest_name);
}
ERR(n < 0, "%s", module_name);
module_size = BIO_number_written(bd);
#ifndef USE_PKCS7
ERR(i2d_CMS_bio_stream(bd, cms, NULL, 0) < 0, "%s", dest_name);
#else
ERR(i2d_PKCS7_bio(bd, pkcs7) < 0, "%s", dest_name);
#endif
sig_size = BIO_number_written(bd) - module_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) < 0, "%s", dest_name);
/* Finally, if we're signing in place, replace the original. */
if (replace_orig)
ERR(rename(dest_name, module_name) < 0, "%s", dest_name);
return 0;
}