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Commit 283e8ba2 authored by David Howells's avatar David Howells
Browse files

MODSIGN: Change from CMS to PKCS#7 signing if the openssl is too old 



The sign-file.c program actually uses CMS rather than PKCS#7 to sign a file
since that allows the target X.509 certificate to be specified by
subjectKeyId rather than by issuer + serialNumber.

However, older versions of the OpenSSL crypto library (such as may be found
in CentOS 5.11) don't support CMS.  Assume everything prior to
OpenSSL-1.0.0 doesn't support CMS and switch to using PKCS#7 in that case.

Further, the pre-1.0.0 OpenSSL only supports PKCS#7 signing with SHA1, so
give an error from the sign-file script if the caller requests anything
other than SHA1.

The compiler gives the following error with an OpenSSL crypto library
that's too old:

  HOSTCC  scripts/sign-file
scripts/sign-file.c:23:25: fatal error: openssl/cms.h: No such file or directory
 #include <openssl/cms.h>

Reported-by: default avatarVinson Lee <vlee@twopensource.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent e7c87bef

Documentation/Changes

+1 −1
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ o udev 081 # udevd --version 
o  grub                   0.93                    # grub --version || grub-install --version

o  mcelog                 0.6                     # mcelog --version

o  iptables               1.4.2                   # iptables -V

o  openssl & libcrypto    1.0.1k                  # openssl version

o  openssl & libcrypto    1.0.0                   # openssl version





Kernel compilation

scripts/sign-file.c

+77 −17
Original line number Diff line number Diff line
@@ -20,13 +20,34 @@ 
#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/cms.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] */
@@ -110,30 +131,42 @@ 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_cms = false, replace_orig;

	bool save_sig = false, replace_orig;

	bool sign_only = false;

	unsigned char buf[4096];

	unsigned long module_size, cms_size;

	unsigned int use_keyid = 0, use_signed_attrs = CMS_NOATTR;

	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_cms = true; break;

		case 'd': sign_only = true; save_cms = 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();

		}
@@ -157,6 +190,14 @@ int main(int argc, char **argv) 
		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.

	 */
@@ -213,7 +254,8 @@ int main(int argc, char **argv) 
	bm = BIO_new_file(module_name, "rb");

	ERR(!bm, "%s", module_name);



	/* Load the CMS message from the digest buffer. */

#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");
@@ -221,17 +263,31 @@ int main(int argc, char **argv) 
	ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo,

			     CMS_NOCERTS | CMS_BINARY | CMS_NOSMIMECAP |

			     use_keyid | use_signed_attrs),

	    "CMS_sign_add_signer");

	    "CMS_add1_signer");

	ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) < 0,

	    "CMS_final");



	if (save_cms) {

		char *cms_name;

#else

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

			   PKCS7_NOCERTS | PKCS7_BINARY |

			   PKCS7_DETACHED | use_signed_attrs);

	ERR(!pkcs7, "PKCS7_sign");

#endif



		ERR(asprintf(&cms_name, "%s.p7s", module_name) < 0, "asprintf");

		b = BIO_new_file(cms_name, "wb");

		ERR(!b, "%s", cms_name);

		ERR(i2d_CMS_bio_stream(b, cms, NULL, 0) < 0, "%s", cms_name);

	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);

	}
@@ -247,9 +303,13 @@ int main(int argc, char **argv) 
	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);

	cms_size = BIO_number_written(bd) - module_size;

	sig_info.sig_len = htonl(cms_size);

#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);