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: Vinson Lee <vlee@twopensource.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/scripts/sign-file.c b/scripts/sign-file.c
index c3899ca..250a7a6 100755
--- a/scripts/sign-file.c
+++ b/scripts/sign-file.c
@@ -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 @@
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 @@
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 @@
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 @@
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 @@
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);