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

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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
This commit is contained in:
David Howells 2015-07-20 21:16:33 +01:00
parent 60d65cacd7
commit ed8c20762a
1 changed files with 27 additions and 24 deletions
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51
scripts/sign-file.c
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@ -20,7 +20,7 @@
#include <openssl/bio.h> #include <openssl/bio.h>
#include <openssl/evp.h> #include <openssl/evp.h>
#include <openssl/pem.h> #include <openssl/pem.h>
#include <openssl/pkcs7.h> #include <openssl/cms.h>
#include <openssl/err.h> #include <openssl/err.h>
#include <openssl/engine.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 }; struct module_signature sig_info = { .id_type = PKEY_ID_PKCS7 };
char *hash_algo = NULL; char *hash_algo = NULL;
char *private_key_name, *x509_name, *module_name, *dest_name; 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; bool sign_only = false;
unsigned char buf[4096]; 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; const EVP_MD *digest_algo;
EVP_PKEY *private_key; EVP_PKEY *private_key;
PKCS7 *pkcs7; CMS_ContentInfo *cms;
X509 *x509; X509 *x509;
BIO *b, *bd = NULL, *bm; BIO *b, *bd = NULL, *bm;
int opt, n; int opt, n;
@ -125,10 +126,11 @@ int main(int argc, char **argv)
key_pass = getenv("KBUILD_SIGN_PIN"); key_pass = getenv("KBUILD_SIGN_PIN");
do { do {
opt = getopt(argc, argv, "dp"); opt = getopt(argc, argv, "dpk");
switch (opt) { switch (opt) {
case 'p': save_pkcs7 = true; break; case 'p': save_cms = true; break;
case 'd': sign_only = true; save_pkcs7 = true; break; case 'd': sign_only = true; save_cms = true; break;
case 'k': use_keyid = CMS_USE_KEYID; break;
case -1: break; case -1: break;
default: format(); default: format();
} }
@ -208,23 +210,24 @@ int main(int argc, char **argv)
bm = BIO_new_file(module_name, "rb"); bm = BIO_new_file(module_name, "rb");
ERR(!bm, "%s", module_name); ERR(!bm, "%s", module_name);
/* Load the PKCS#7 message from the digest buffer. */ /* Load the CMS message from the digest buffer. */
pkcs7 = PKCS7_sign(NULL, NULL, NULL, NULL, cms = CMS_sign(NULL, NULL, NULL, NULL,
PKCS7_NOCERTS | PKCS7_PARTIAL | PKCS7_BINARY | PKCS7_DETACHED | PKCS7_STREAM); CMS_NOCERTS | CMS_PARTIAL | CMS_BINARY | CMS_DETACHED | CMS_STREAM);
ERR(!pkcs7, "PKCS7_sign"); ERR(!cms, "CMS_sign");
ERR(!PKCS7_sign_add_signer(pkcs7, x509, private_key, digest_algo, PKCS7_NOCERTS | PKCS7_BINARY), ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo,
"PKCS7_sign_add_signer"); CMS_NOCERTS | CMS_BINARY | CMS_NOSMIMECAP | use_keyid),
ERR(PKCS7_final(pkcs7, bm, PKCS7_NOCERTS | PKCS7_BINARY) < 0, "CMS_sign_add_signer");
"PKCS7_final"); ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) < 0,
"CMS_final");
if (save_pkcs7) { if (save_cms) {
char *pkcs7_name; char *cms_name;
ERR(asprintf(&pkcs7_name, "%s.pkcs7", module_name) < 0, "asprintf"); ERR(asprintf(&cms_name, "%s.p7s", module_name) < 0, "asprintf");
b = BIO_new_file(pkcs7_name, "wb"); b = BIO_new_file(cms_name, "wb");
ERR(!b, "%s", pkcs7_name); ERR(!b, "%s", cms_name);
ERR(i2d_PKCS7_bio_stream(b, pkcs7, NULL, 0) < 0, "%s", pkcs7_name); ERR(i2d_CMS_bio_stream(b, cms, NULL, 0) < 0, "%s", cms_name);
BIO_free(b); BIO_free(b);
} }
@ -240,9 +243,9 @@ int main(int argc, char **argv)
ERR(n < 0, "%s", module_name); ERR(n < 0, "%s", module_name);
module_size = BIO_number_written(bd); module_size = BIO_number_written(bd);
ERR(i2d_PKCS7_bio_stream(bd, pkcs7, NULL, 0) < 0, "%s", dest_name); ERR(i2d_CMS_bio_stream(bd, cms, NULL, 0) < 0, "%s", dest_name);
pkcs7_size = BIO_number_written(bd) - module_size; cms_size = BIO_number_written(bd) - module_size;
sig_info.sig_len = htonl(pkcs7_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, &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_write(bd, magic_number, sizeof(magic_number) - 1) < 0, "%s", dest_name);