Re: [PATCH] libkmod-signature: implement pkcs7 parsing with openssl

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

>>>>> On Fri, 16 Nov 2018 20:32:28 +0200, Yauheni Kaliuta  wrote:

 > The patch adds data fetching from the PKCS#7 certificate using
 > openssl library (which is used by scripts/sign-file.c in the linux
 > kernel to sign modules).

 > In general the certificate can contain many signatures, but since
 > kmod (modinfo) supports only one signature at the moment,

Did not finish the paragraph:

In general the certificate can contain many signatures, but since
kmod (modinfo) supports only one signature at the moment, only first
one is taken.

 > With the current sign-file.c certificate doesn't contain signer
 > key's fingerprint, so "serial number" is used for the key id.

 > Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
 > ---
 >  Makefile.am                 |   4 +-
 >  configure.ac                |  11 ++
 >  libkmod/libkmod-internal.h  |   3 +
 >  libkmod/libkmod-module.c    |   3 +
 >  libkmod/libkmod-signature.c | 195 +++++++++++++++++++++++++++++++++++-
 >  5 files changed, 211 insertions(+), 5 deletions(-)

 > diff --git a/Makefile.am b/Makefile.am
 > index 194e1115ae70..5ab7fc0b4750 100644
 > --- a/Makefile.am
 > +++ b/Makefile.am
 > @@ -35,6 +35,8 @@ SED_PROCESS = \
 >  	-e 's,@liblzma_LIBS\@,${liblzma_LIBS},g' \
 >  	-e 's,@zlib_CFLAGS\@,${zlib_CFLAGS},g' \
 >  	-e 's,@zlib_LIBS\@,${zlib_LIBS},g' \
 > +	-e 's,@openssl_CFLAGS\@,${openssl_CFLAGS},g' \
 > +	-e 's,@openssl_LIBS\@,${openssl_LIBS},g' \
 >  	< $< > $@ || rm $@
 
 >  %.pc: %.pc.in Makefile
 > @@ -87,7 +89,7 @@ libkmod_libkmod_la_DEPENDENCIES = \
 >  	${top_srcdir}/libkmod/libkmod.sym
 >  libkmod_libkmod_la_LIBADD = \
 >  	shared/libshared.la \
 > -	${liblzma_LIBS} ${zlib_LIBS}
 > +	${liblzma_LIBS} ${zlib_LIBS} ${openssl_LIBS}
 
 >  noinst_LTLIBRARIES += libkmod/libkmod-internal.la
 >  libkmod_libkmod_internal_la_SOURCES = $(libkmod_libkmod_la_SOURCES)
 > diff --git a/configure.ac b/configure.ac
 > index fbc7391b2d1b..2e33380a0cc2 100644
 > --- a/configure.ac
 > +++ b/configure.ac
 > @@ -106,6 +106,17 @@ AS_IF([test "x$with_zlib" != "xno"], [
 >  ])
 >  CC_FEATURE_APPEND([with_features], [with_zlib], [ZLIB])
 
 > +AC_ARG_WITH([openssl],
 > +	AS_HELP_STRING([--with-openssl], [handle PKCS7 signatures @<:@default=disabled@:>@]),
 > +	[], [with_openssl=no])
 > +AS_IF([test "x$with_openssl" != "xno"], [
 > +	PKG_CHECK_MODULES([openssl], [openssl])
 > +	AC_DEFINE([ENABLE_OPENSSL], [1], [Enable openssl for modinfo.])
 > +], [
 > +	AC_MSG_NOTICE([openssl support not requested])
 > +])
 > +CC_FEATURE_APPEND([with_features], [with_openssl], [OPENSSL])
 > +
 >  AC_ARG_WITH([bashcompletiondir],
 >  	AS_HELP_STRING([--with-bashcompletiondir=DIR], [Bash completions directory]),
 >  	[],
 > diff --git a/libkmod/libkmod-internal.h b/libkmod/libkmod-internal.h
 > index 346579c71aab..a65ddd156f18 100644
 > --- a/libkmod/libkmod-internal.h
 > +++ b/libkmod/libkmod-internal.h
 > @@ -188,5 +188,8 @@ struct kmod_signature_info {
 >  	const char *algo, *hash_algo, *id_type;
 >  	const char *sig;
 >  	size_t sig_len;
 > +	void (*free)(void *);
 > +	void *private;
 >  };
 >  bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signature_info *sig_info) _must_check_ __attribute__((nonnull(1, 2)));
 > +void kmod_module_signature_info_free(struct kmod_signature_info *sig_info) __attribute__((nonnull));
 > diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
 > index 889f26479a98..bffe715cdef4 100644
 > --- a/libkmod/libkmod-module.c
 > +++ b/libkmod/libkmod-module.c
 > @@ -2357,6 +2357,9 @@ KMOD_EXPORT int kmod_module_get_info(const struct kmod_module *mod, struct kmod_
 >  	ret = count;
 
 >  list_error:
 > +	/* aux structures freed in normal case also */
 > +	kmod_module_signature_info_free(&sig_info);
 > +
 >  	if (ret < 0) {
 >  		kmod_module_info_free_list(*list);
 >  		*list = NULL;
 > diff --git a/libkmod/libkmod-signature.c b/libkmod/libkmod-signature.c
 > index 429ffbd8a957..4b44c3701d28 100644
 > --- a/libkmod/libkmod-signature.c
 > +++ b/libkmod/libkmod-signature.c
 > @@ -19,6 +19,10 @@
 
 >  #include <endian.h>
 >  #include <inttypes.h>
 > +#ifdef ENABLE_OPENSSL
 > +#include <openssl/cms.h>
 > +#include <openssl/ssl.h>
 > +#endif
 >  #include <stdio.h>
 >  #include <stdlib.h>
 >  #include <string.h>
 > @@ -115,15 +119,192 @@ static bool fill_default(const char *mem, off_t size,
 >  	return true;
 >  }
 
 > -static bool fill_unknown(const char *mem, off_t size,
 > -			 const struct module_signature *modsig, size_t sig_len,
 > -			 struct kmod_signature_info *sig_info)
 > +#ifdef ENABLE_OPENSSL
 > +
 > +struct pkcs7_private {
 > +	CMS_ContentInfo *cms;
 > +	unsigned char *key_id;
 > +	BIGNUM *sno;
 > +};
 > +
 > +static void pkcs7_free(void *s)
 > +{
 > +	struct kmod_signature_info *si = s;
 > +	struct pkcs7_private *pvt = si->private;
 > +
 > +	CMS_ContentInfo_free(pvt->cms);
 > +	BN_free(pvt->sno);
 > +	free(pvt->key_id);
 > +	free(pvt);
 > +	si->private = NULL;
 > +}
 > +
 > +static int obj_to_hash_algo(const ASN1_OBJECT *o)
 > +{
 > +	int nid;
 > +
 > +	nid = OBJ_obj2nid(o);
 > +	switch (nid) {
 > +	case NID_md4:
 > +		return PKEY_HASH_MD4;
 > +	case NID_md5:
 > +		return PKEY_HASH_MD5;
 > +	case NID_sha1:
 > +		return PKEY_HASH_SHA1;
 > +	case NID_ripemd160:
 > +		return PKEY_HASH_RIPE_MD_160;
 > +	case NID_sha256:
 > +		return PKEY_HASH_SHA256;
 > +	case NID_sha384:
 > +		return PKEY_HASH_SHA384;
 > +	case NID_sha512:
 > +		return PKEY_HASH_SHA512;
 > +	case NID_sha224:
 > +		return PKEY_HASH_SHA224;
 > +	default:
 > +		return -1;
 > +	}
 > +	return -1;
 > +}
 > +
 > +static const char *x509_name_to_str(X509_NAME *name)
 > +{
 > +	int i;
 > +	X509_NAME_ENTRY *e;
 > +	ASN1_STRING *d;
 > +	ASN1_OBJECT *o;
 > +	int nid = -1;
 > +	const char *str;
 > +
 > +	for (i = 0; i < X509_NAME_entry_count(name); i++) {
 > +		e = X509_NAME_get_entry(name, i);
 > +		o = X509_NAME_ENTRY_get_object(e);
 > +		nid = OBJ_obj2nid(o);
 > +		if (nid == NID_commonName)
 > +			break;
 > +	}
 > +	if (nid == -1)
 > +		return NULL;
 > +
 > +	d = X509_NAME_ENTRY_get_data(e);
 > +	str = (const char *)ASN1_STRING_get0_data(d);
 > +
 > +	return str;
 > +}
 > +
 > +static bool fill_pkcs7(const char *mem, off_t size,
 > +		       const struct module_signature *modsig, size_t sig_len,
 > +		       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;
 > +	X509_NAME *issuer;
 > +	ASN1_INTEGER *sno;
 > +	ASN1_OCTET_STRING *sig;
 > +	BIGNUM *sno_bn;
 > +	X509_ALGOR *dig_alg;
 > +	X509_ALGOR *sig_alg;
 > +	const ASN1_OBJECT *o;
 > +	BIO *in;
 > +	int len;
 > +	unsigned char *key_id_str;
 > +	struct pkcs7_private *pvt;
 > +	const char *issuer_str;
 > +
 > +	size -= sig_len;
 > +	pkcs7_raw = mem + size;
 > +
 > +	in = BIO_new_mem_buf(pkcs7_raw, sig_len);
 > +
 > +	cms = d2i_CMS_bio(in, NULL);
 > +	if (cms == NULL) {
 > +		BIO_free(in);
 > +		return false;
 > +	}
 > +
 > +	BIO_free(in);
 > +
 > +	sis = CMS_get0_SignerInfos(cms);
 > +	if (sis == NULL)
 > +		goto err;
 > +
 > +	si = sk_CMS_SignerInfo_value(sis, 0);
 > +	if (si == NULL)
 > +		goto err;
 > +
 > +	rc = CMS_SignerInfo_get0_signer_id(si, &key_id, &issuer, &sno);
 > +	if (rc == 0)
 > +		goto err;
 > +
 > +	sig = CMS_SignerInfo_get0_signature(si);
 > +	if (sig == NULL)
 > +		goto err;
 > +
 > +	CMS_SignerInfo_get0_algs(si, NULL, NULL, &dig_alg, &sig_alg);
 > +
 > +	sig_info->sig = (const char *)ASN1_STRING_get0_data(sig);
 > +	sig_info->sig_len = ASN1_STRING_length(sig);
 > +
 > +
 > +	sno_bn = ASN1_INTEGER_to_BN(sno, NULL);
 > +	if (sno_bn == NULL)
 > +		goto err;
 > +
 > +	len = BN_num_bytes(sno_bn);
 > +	key_id_str = malloc(len);
 > +	BN_bn2bin(sno_bn, key_id_str);
 > +
 > +	sig_info->key_id = (const char *)key_id_str;
 > +	sig_info->key_id_len = len;
 > +
 > +	issuer_str = x509_name_to_str(issuer);
 > +	if (issuer_str != NULL) {
 > +		sig_info->signer = issuer_str;
 > +		sig_info->signer_len = strlen(issuer_str);
 > +	}
 > +
 > +	sig_info->algo = NULL;
 > +
 > +	X509_ALGOR_get0(&o, NULL, NULL, dig_alg);
 > +
 > +	sig_info->hash_algo = pkey_hash_algo[obj_to_hash_algo(o)];
 > +	sig_info->id_type = pkey_id_type[modsig->id_type];
 > +
 > +	pvt = malloc(sizeof(*pvt));
 > +	if (pvt == NULL)
 > +		goto err;
 > +
 > +	pvt->cms = cms;
 > +	pvt->key_id = key_id_str;
 > +	pvt->sno = sno_bn;
 > +	sig_info->private = pvt;
 > +
 > +	sig_info->free = pkcs7_free;
 > +
 > +	return true;
 > +
 > +err:
 > +	CMS_ContentInfo_free(cms);
 > +	return false;
 > +}
 > +
 > +#else /* ENABLE OPENSSL */
 > +
 > +static bool fill_pkcs7(const char *mem, off_t size,
 > +		       const struct module_signature *modsig, size_t sig_len,
 > +		       struct kmod_signature_info *sig_info)
 >  {
 sig_info-> hash_algo = "unknown";
 sig_info-> id_type = pkey_id_type[modsig->id_type];
 >  	return true;
 >  }
 
 > +#endif /* ENABLE OPENSSL */
 > +
 >  #define SIG_MAGIC "~Module signature appended~\n"
 
 >  /*
 > @@ -167,8 +348,14 @@ bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signat
 
 >  	switch (modsig->id_type) {
 >  	case PKEY_ID_PKCS7:
 > -		return fill_unknown(mem, size, modsig, sig_len, sig_info);
 > +		return fill_pkcs7(mem, size, modsig, sig_len, sig_info);
 >  	default:
 >  		return fill_default(mem, size, modsig, sig_len, sig_info);
 >  	}
 >  }
 > +
 > +void kmod_module_signature_info_free(struct kmod_signature_info *sig_info)
 > +{
 > +	if (sig_info->free)
 > +		sig_info->free(sig_info);
 > +}
 > -- 
 > 2.19.1


-- 
WBR,
Yauheni Kaliuta