sign-file: Generate CMS message as signature instead of PKCS#7

Make sign-file use the OpenSSL CMS routines to generate a message to be
used as the signature blob instead of the PKCS#7 routines.  This allows us
to change how the matching X.509 certificate is selected.  With PKCS#7 the
only option is to match on the serial number and issuer fields of an X.509
certificate; with CMS, we also have the option of matching by subjectKeyId
extension.  The new behaviour is selected with the "-k" flag.

Without the -k flag specified, the output is pretty much identical to the
PKCS#7 output.

Whilst we're at it, don't include the S/MIME capability list in the message
as it's irrelevant to us.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-By: David Woodhouse <David.Woodhouse@intel.com

1 files changed, 27 insertions, 24 deletions

diff --git a/scripts/sign-file.c b/scripts/sign-file.c
index ad0aa21bd3ac..de213e5c0cd3 100755
--- a/scripts/sign-file.c
+++ b/scripts/sign-file.c
@@ -20,7 +20,7 @@
 #include <openssl/bio.h>
 #include <openssl/evp.h>
 #include <openssl/pem.h>
-#include <openssl/pkcs7.h>
+#include <openssl/cms.h>
 #include <openssl/err.h>
 #include <openssl/engine.h>
 
@@ -107,13 +107,14 @@ 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_pkcs7 = false, replace_orig;
+        bool save_cms = false, replace_orig;
         bool sign_only = false;
         unsigned char buf[4096];
-        unsigned long module_size, pkcs7_size;
+        unsigned long module_size, cms_size;
+        unsigned int use_keyid = 0;
         const EVP_MD *digest_algo;
         EVP_PKEY *private_key;
-        PKCS7 *pkcs7;
+        CMS_ContentInfo *cms;
         X509 *x509;
         BIO *b, *bd = NULL, *bm;
         int opt, n;
@@ -125,10 +126,11 @@ int main(int argc, char **argv)
         key_pass = getenv("KBUILD_SIGN_PIN");
 
         do {
-                opt = getopt(argc, argv, "dp");
+                opt = getopt(argc, argv, "dpk");
                 switch (opt) {
-                case 'p': save_pkcs7 = true; break;
-                case 'd': sign_only = true; save_pkcs7 = true; break;
+                case 'p': save_cms = true; break;
+                case 'd': sign_only = true; save_cms = true; break;
+                case 'k': use_keyid = CMS_USE_KEYID; break;
                 case -1: break;
                 default: format();
                 }
@@ -208,23 +210,24 @@ int main(int argc, char **argv)
         bm = BIO_new_file(module_name, "rb");
         ERR(!bm, "%s", module_name);
 
-        /* Load the PKCS#7 message from the digest buffer. */
-        pkcs7 = PKCS7_sign(NULL, NULL, NULL, NULL,
-                           PKCS7_NOCERTS | PKCS7_PARTIAL | PKCS7_BINARY | PKCS7_DETACHED | PKCS7_STREAM);
-        ERR(!pkcs7, "PKCS7_sign");
+        /* Load the CMS 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(!PKCS7_sign_add_signer(pkcs7, x509, private_key, digest_algo, PKCS7_NOCERTS | PKCS7_BINARY),
-            "PKCS7_sign_add_signer");
-        ERR(PKCS7_final(pkcs7, bm, PKCS7_NOCERTS | PKCS7_BINARY) < 0,
-            "PKCS7_final");
+        ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo,
+                             CMS_NOCERTS | CMS_BINARY | CMS_NOSMIMECAP | use_keyid),
+            "CMS_sign_add_signer");
+        ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) < 0,
+            "CMS_final");
 
-        if (save_pkcs7) {
-                char *pkcs7_name;
+        if (save_cms) {
+                char *cms_name;
 
-                ERR(asprintf(&pkcs7_name, "%s.pkcs7", module_name) < 0, "asprintf");
-                b = BIO_new_file(pkcs7_name, "wb");
-                ERR(!b, "%s", pkcs7_name);
-                ERR(i2d_PKCS7_bio_stream(b, pkcs7, NULL, 0) < 0, "%s", pkcs7_name);
+                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);
                 BIO_free(b);
         }
 
@@ -240,9 +243,9 @@ int main(int argc, char **argv)
         ERR(n < 0, "%s", module_name);
         module_size = BIO_number_written(bd);
 
-        ERR(i2d_PKCS7_bio_stream(bd, pkcs7, NULL, 0) < 0, "%s", dest_name);
-        pkcs7_size = BIO_number_written(bd) - module_size;
-        sig_info.sig_len = htonl(pkcs7_size);
+        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);
         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);