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

[Yauheni Kaliuta <yauheni.kaliuta@redhat.com>]

Hi, Stefan!

Just in case, I have no objections.

>>>>> On Sun, 19 May 2019 03:42:01 +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.

 > 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


-- 
WBR,
Yauheni Kaliuta