Re: [PATCH v2] libkmod-signature: use PKCS#7 instead of CMS

[Lucas De Marchi <lucas.demarchi@intel.com>]

On Sun, May 19, 2019 at 03:42:01AM +0300, Stefan Strogin wrote:
>Linux uses either PKCS #7 or CMS for signing modules (see
>scripts/sign-file.c). CMS is not supported by LibreSSL or older OpenSSL,
>so PKCS #7 is used on systems with these libcrypto providers.
>
>CMS and PKCS #7 formats are very similar. CMS is newer but is as much as
>possible backward compatible with PKCS #7 [1]. PKCS #7 is supported in
>the latest OpenSSL as well as CMS. The fields used for signing kernel
>modules are supported both in PKCS #7 and CMS.
>
>For now modinfo uses CMS with no alternative requiring OpenSSL 1.1.0 or
>newer.
>
>Use PKCS #7 for parsing module signature information, so that modinfo
>could be used both with OpenSSL and LibreSSL.
>
>[1] https://tools.ietf.org/html/rfc5652#section-1.1
>
>Changes v1->v2:
>- Don't use ifdefs for keeping redundant CMS code, just use PKCS #7 both
>with OpenSSL and LibreSSL.

Much better now, thanks!

Applied.

Lucas De Marchi

>
>Signed-off-by: Stefan Strogin <steils@gentoo.org>
>---
> libkmod/libkmod-signature.c | 37 +++++++++++++++++++------------------
> 1 file changed, 19 insertions(+), 18 deletions(-)
>
>diff --git a/libkmod/libkmod-signature.c b/libkmod/libkmod-signature.c
>index 48d0145..4e8748c 100644
>--- a/libkmod/libkmod-signature.c
>+++ b/libkmod/libkmod-signature.c
>@@ -20,7 +20,7 @@
> #include <endian.h>
> #include <inttypes.h>
> #ifdef ENABLE_OPENSSL
>-#include <openssl/cms.h>
>+#include <openssl/pkcs7.h>
> #include <openssl/ssl.h>
> #endif
> #include <stdio.h>
>@@ -122,7 +122,7 @@ static bool fill_default(const char *mem, off_t size,
> #ifdef ENABLE_OPENSSL
>
> struct pkcs7_private {
>-	CMS_ContentInfo *cms;
>+	PKCS7 *pkcs7;
> 	unsigned char *key_id;
> 	BIGNUM *sno;
> };
>@@ -132,7 +132,7 @@ static void pkcs7_free(void *s)
> 	struct kmod_signature_info *si = s;
> 	struct pkcs7_private *pvt = si->private;
>
>-	CMS_ContentInfo_free(pvt->cms);
>+	PKCS7_free(pvt->pkcs7);
> 	BN_free(pvt->sno);
> 	free(pvt->key_id);
> 	free(pvt);
>@@ -197,11 +197,10 @@ static bool fill_pkcs7(const char *mem, off_t size,
> 		       struct kmod_signature_info *sig_info)
> {
> 	const char *pkcs7_raw;
>-	CMS_ContentInfo *cms;
>-	STACK_OF(CMS_SignerInfo) *sis;
>-	CMS_SignerInfo *si;
>-	int rc;
>-	ASN1_OCTET_STRING *key_id;
>+	PKCS7 *pkcs7;
>+	STACK_OF(PKCS7_SIGNER_INFO) *sis;
>+	PKCS7_SIGNER_INFO *si;
>+	PKCS7_ISSUER_AND_SERIAL *is;
> 	X509_NAME *issuer;
> 	ASN1_INTEGER *sno;
> 	ASN1_OCTET_STRING *sig;
>@@ -220,31 +219,33 @@ static bool fill_pkcs7(const char *mem, off_t size,
>
> 	in = BIO_new_mem_buf(pkcs7_raw, sig_len);
>
>-	cms = d2i_CMS_bio(in, NULL);
>-	if (cms == NULL) {
>+	pkcs7 = d2i_PKCS7_bio(in, NULL);
>+	if (pkcs7 == NULL) {
> 		BIO_free(in);
> 		return false;
> 	}
>
> 	BIO_free(in);
>
>-	sis = CMS_get0_SignerInfos(cms);
>+	sis = PKCS7_get_signer_info(pkcs7);
> 	if (sis == NULL)
> 		goto err;
>
>-	si = sk_CMS_SignerInfo_value(sis, 0);
>+	si = sk_PKCS7_SIGNER_INFO_value(sis, 0);
> 	if (si == NULL)
> 		goto err;
>
>-	rc = CMS_SignerInfo_get0_signer_id(si, &key_id, &issuer, &sno);
>-	if (rc == 0)
>+	is = si->issuer_and_serial;
>+	if (is == NULL)
> 		goto err;
>+	issuer = is->issuer;
>+	sno = is->serial;
>
>-	sig = CMS_SignerInfo_get0_signature(si);
>+	sig = si->enc_digest;
> 	if (sig == NULL)
> 		goto err;
>
>-	CMS_SignerInfo_get0_algs(si, NULL, NULL, &dig_alg, &sig_alg);
>+	PKCS7_SIGNER_INFO_get0_algs(si, NULL, &dig_alg, &sig_alg);
>
> 	sig_info->sig = (const char *)ASN1_STRING_get0_data(sig);
> 	sig_info->sig_len = ASN1_STRING_length(sig);
>@@ -277,7 +278,7 @@ static bool fill_pkcs7(const char *mem, off_t size,
> 	if (pvt == NULL)
> 		goto err3;
>
>-	pvt->cms = cms;
>+	pvt->pkcs7 = pkcs7;
> 	pvt->key_id = key_id_str;
> 	pvt->sno = sno_bn;
> 	sig_info->private = pvt;
>@@ -290,7 +291,7 @@ err3:
> err2:
> 	BN_free(sno_bn);
> err:
>-	CMS_ContentInfo_free(cms);
>+	PKCS7_free(pkcs7);
> 	return false;
> }
>
>-- 
>2.21.0
>