[PATCH 25/27] PKCS#7: Appropriately require or forbid authenticated attributes [ver #7]

[David Howells]

A PKCS#7 or CMS message can have per-signature authenticated attributes
that are digested as a lump and signed by the authorising key for that
signature.  If such attributes exist, the content digest isn't itself
signed, but rather it is included in a special authattr which then
contributes to the signature.

Further, we already require the master message content type to be
pkcs7_signedData - but there's also a separate content type for the data
itself within the SignedData object and this must be repeated inside the
authattrs for each signer [RFC2315 9.2, RFC5652 11.1].

We should really validate the authattrs if they exist or forbid them
entirely as appropriate.  To this end:

 (1) Alter the PKCS#7 parser to reject any message that has more than one
     signature where at least one signature has authattrs and at least one
     that does not.

 (2) Validate authattrs if they are present and strongly restrict them.
     Only the following authattrs are permitted and all others are
     rejected:

     (a) contentType.  This is checked to be an OID that matches the
     	 content type in the SignedData object.

     (b) messageDigest.  This must match the crypto digest of the data.

     (c) signingTime.  If present, we check that this is a valid, parseable
     	 UTCTime or GeneralTime and that the date it encodes fits within
     	 the validity window of the matching X.509 cert.

     (d) S/MIME capabilities.  We don't check the contents.

     (e) Authenticode SP Opus Info.  We don't check the contents.

     (f) Authenticode Statement Type.  We don't check the contents.

     The message is rejected if (a) or (b) are missing.  If the message is
     an Authenticode type, the message is rejected if (e) is missing; if
     not Authenticode, the message is rejected if (d) - (f) are present.

     The S/MIME capabilities authattr (d) unfortunately has to be allowed
     to support kernels already signed by the pesign program.  This only
     affects kexec.  sign-file suppresses them (CMS_NOSMIMECAP).

     The message is also rejected if an authattr is given more than once or
     if it contains more than one element in its set of values.

 (3) Add a parameter to pkcs7_verify() to select one of three options:

     (A) Require pkcs7_data type content and forbid authattrs entirely.

     (B) Require pkcs7_data type content and require authattrs but to
     	 reject Microsoft Authenticode authattrs.

     (C) Require an Authenticode type content (only indirect data is
     	 currently supported) and permit/require certain Authenticode
     	 authattrs.

 (4) Have module verification choose option (A) above.  This means that
     with module signing, the signature is over the content digest only.
     sign-file sets CMS_NOATTR to suppress authattrs.  We could be more
     flexible and permit (A) or (B) for module signing.

 (5) Have kexec verification of PE executables choose option (C) above.  We
     may need to relax this if signed PE files may be encountered that
     don't have authattrs in their PKCS#7 message.

     Kexec does not currently verify non-PE executables - but if this is
     added in the future it should probably use option (A).

 (6) The pkcs7_test key type is given a module parameter to select between
     the above options for testing purposes.

Future patches add firmware signing support.  Firmware signing will require
a signed authattr containing the firmware name as passed to
request_firmware() and so would pick option (B) above, but we would also
need to permit the firmware name authattr.

Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
---

 crypto/asymmetric_keys/pkcs7.asn1       |    6 +
 crypto/asymmetric_keys/pkcs7_key_type.c |    9 ++
 crypto/asymmetric_keys/pkcs7_parser.c   |  138 ++++++++++++++++++++++++++++++-
 crypto/asymmetric_keys/pkcs7_parser.h   |   15 +++
 crypto/asymmetric_keys/pkcs7_verify.c   |   53 +++++++++++-
 crypto/asymmetric_keys/verify_pefile.c  |    2 
 include/crypto/pkcs7.h                  |   13 +++
 include/linux/oid_registry.h            |    4 +
 kernel/system_keyring.c                 |    2 
 scripts/sign-file.c                     |    5 +
 10 files changed, 226 insertions(+), 21 deletions(-)

diff --git a/crypto/asymmetric_keys/pkcs7.asn1 b/crypto/asymmetric_keys/pkcs7.asn1
index 6bf8ff4f7414..1eca740b816a 100644
--- a/crypto/asymmetric_keys/pkcs7.asn1
+++ b/crypto/asymmetric_keys/pkcs7.asn1
@@ -8,7 +8,7 @@ ContentType ::= OBJECT IDENTIFIER ({ pkcs7_note_OID })
 SignedData ::= SEQUENCE {
 	version			INTEGER ({ pkcs7_note_signeddata_version }),
 	digestAlgorithms	DigestAlgorithmIdentifiers,
-	contentInfo		ContentInfo,
+	contentInfo		ContentInfo ({ pkcs7_note_content }),
 	certificates		CHOICE {
 		certSet		[0] IMPLICIT ExtendedCertificatesAndCertificates,
 		certSequence	[2] IMPLICIT Certificates
@@ -21,7 +21,7 @@ SignedData ::= SEQUENCE {
 }
 
 ContentInfo ::= SEQUENCE {
-	contentType	ContentType,
+	contentType	ContentType ({ pkcs7_note_OID }),
 	content		[0] EXPLICIT Data OPTIONAL
 }
 
@@ -111,7 +111,7 @@ AuthenticatedAttribute ::= SEQUENCE {
 }
 
 UnauthenticatedAttribute ::= SEQUENCE {
-	type			OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+	type			OBJECT IDENTIFIER,
 	values			SET OF ANY
 }
 
diff --git a/crypto/asymmetric_keys/pkcs7_key_type.c b/crypto/asymmetric_keys/pkcs7_key_type.c
index 3d13b042da73..6eae1a30b143 100644
--- a/crypto/asymmetric_keys/pkcs7_key_type.c
+++ b/crypto/asymmetric_keys/pkcs7_key_type.c
@@ -19,6 +19,11 @@
 #include <keys/system_keyring.h>
 #include "pkcs7_parser.h"
 
+static unsigned pkcs7_want_authattrs;
+module_param_named(authattrs, pkcs7_want_authattrs, uint, S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(pkcs7_want_authattrs,
+		 "Whether or not a PKCS#7 message should contain authattrs (0-2)");
+
 /*
  * Preparse a PKCS#7 wrapped and validated data blob.
  */
@@ -40,7 +45,9 @@ static int pkcs7_preparse(struct key_preparsed_payload *prep)
 		goto error;
 	}
 
-	ret = pkcs7_verify(pkcs7);
+	if (pkcs7_want_authattrs > 2)
+		pkcs7_want_authattrs = 0;
+	ret = pkcs7_verify(pkcs7, pkcs7_want_authattrs);
 	if (ret < 0)
 		goto error_free;
 
diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
index 826e2f3f507b..e6298b7a945a 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.c
+++ b/crypto/asymmetric_keys/pkcs7_parser.c
@@ -81,6 +81,30 @@ void pkcs7_free_message(struct pkcs7_message *pkcs7)
 }
 EXPORT_SYMBOL_GPL(pkcs7_free_message);
 
+/*
+ * Check authenticatedAttributes are provided or not provided consistently.
+ */
+static int pkcs7_check_authattrs(struct pkcs7_message *msg)
+{
+	struct pkcs7_signed_info *sinfo;
+	bool want;
+
+	sinfo = msg->signed_infos;
+	if (sinfo->authattrs) {
+		want = true;
+		msg->have_authattrs = true;
+	}
+
+	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
+		if (!!sinfo->authattrs != want)
+			goto inconsistent;
+	return 0;
+
+inconsistent:
+	pr_warn("Inconsistently supplied authAttrs\n");
+	return -EINVAL;
+}
+
 /**
  * pkcs7_parse_message - Parse a PKCS#7 message
  * @data: The raw binary ASN.1 encoded message to be parsed
@@ -113,6 +137,10 @@ struct pkcs7_message *pkcs7_parse_message(const void *data, size_t datalen)
 		goto out;
 	}
 
+	ret = pkcs7_check_authattrs(ctx->msg);
+	if (ret < 0)
+		goto out;
+
 	msg = ctx->msg;
 	ctx->msg = NULL;
 
@@ -381,6 +409,25 @@ int pkcs7_note_certificate_list(void *context, size_t hdrlen,
 }
 
 /*
+ * Note the content type.
+ */
+int pkcs7_note_content(void *context, size_t hdrlen,
+		       unsigned char tag,
+		       const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	if (ctx->last_oid != OID_data &&
+	    ctx->last_oid != OID_msIndirectData) {
+		pr_warn("Unsupported data type %d\n", ctx->last_oid);
+		return -EINVAL;
+	}
+
+	ctx->msg->data_type = ctx->last_oid;
+	return 0;
+}
+
+/*
  * Extract the data from the message and store that and its content type OID in
  * the context.
  */
@@ -395,31 +442,90 @@ int pkcs7_note_data(void *context, size_t hdrlen,
 	ctx->msg->data = value;
 	ctx->msg->data_len = vlen;
 	ctx->msg->data_hdrlen = hdrlen;
-	ctx->msg->data_type = ctx->last_oid;
 	return 0;
 }
 
 /*
- * Parse authenticated attributes
+ * Parse authenticated attributes.
  */
 int pkcs7_sig_note_authenticated_attr(void *context, size_t hdrlen,
 				      unsigned char tag,
 				      const void *value, size_t vlen)
 {
 	struct pkcs7_parse_context *ctx = context;
+	struct pkcs7_signed_info *sinfo = ctx->sinfo;
+	enum OID content_type;
 
 	pr_devel("AuthAttr: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
 
 	switch (ctx->last_oid) {
+	case OID_contentType:
+		if (__test_and_set_bit(sinfo_has_content_type, &sinfo->aa_set))
+			goto repeated;
+		content_type = look_up_OID(value, vlen);
+		if (content_type != ctx->msg->data_type) {
+			pr_warn("Mismatch between global data type (%d) and sinfo %u (%d)\n",
+				ctx->msg->data_type, sinfo->index,
+				content_type);
+			return -EBADMSG;
+		}
+		return 0;
+
+	case OID_signingTime:
+		if (__test_and_set_bit(sinfo_has_signing_time, &sinfo->aa_set))
+			goto repeated;
+		/* Should we check that the signing time is consistent
+		 * with the signer's X.509 cert?
+		 */
+		return x509_decode_time(&sinfo->signing_time,
+					hdrlen, tag, value, vlen);
+
 	case OID_messageDigest:
+		if (__test_and_set_bit(sinfo_has_message_digest, &sinfo->aa_set))
+			goto repeated;
 		if (tag != ASN1_OTS)
 			return -EBADMSG;
-		ctx->sinfo->msgdigest = value;
-		ctx->sinfo->msgdigest_len = vlen;
+		sinfo->msgdigest = value;
+		sinfo->msgdigest_len = vlen;
+		return 0;
+
+	case OID_smimeCapabilites:
+		if (__test_and_set_bit(sinfo_has_smime_caps, &sinfo->aa_set))
+			goto repeated;
+		if (ctx->msg->data_type != OID_msIndirectData) {
+			pr_warn("S/MIME Caps only allowed with Authenticode\n");
+			return -EKEYREJECTED;
+		}
+		return 0;
+
+		/* Microsoft SpOpusInfo seems to be contain cont[0] 16-bit BE
+		 * char URLs and cont[1] 8-bit char URLs.
+		 *
+		 * Microsoft StatementType seems to contain a list of OIDs that
+		 * are also used as extendedKeyUsage types in X.509 certs.
+		 */
+	case OID_msSpOpusInfo:
+		if (__test_and_set_bit(sinfo_has_ms_opus_info, &sinfo->aa_set))
+			goto repeated;
+		goto authenticode_check;
+	case OID_msStatementType:
+		if (__test_and_set_bit(sinfo_has_ms_statement_type, &sinfo->aa_set))
+			goto repeated;
+	authenticode_check:
+		if (ctx->msg->data_type != OID_msIndirectData) {
+			pr_warn("Authenticode AuthAttrs only allowed with Authenticode\n");
+			return -EKEYREJECTED;
+		}
+		/* I'm not sure how to validate these */
 		return 0;
 	default:
 		return 0;
 	}
+
+repeated:
+	/* We permit max one item per AuthenticatedAttribute and no repeats */
+	pr_warn("Repeated/multivalue AuthAttrs not permitted\n");
+	return -EKEYREJECTED;
 }
 
 /*
@@ -430,10 +536,25 @@ int pkcs7_sig_note_set_of_authattrs(void *context, size_t hdrlen,
 				    const void *value, size_t vlen)
 {
 	struct pkcs7_parse_context *ctx = context;
+	struct pkcs7_signed_info *sinfo = ctx->sinfo;
+
+	if (!test_bit(sinfo_has_content_type, &sinfo->aa_set) ||
+	    !test_bit(sinfo_has_message_digest, &sinfo->aa_set) ||
+	    (ctx->msg->data_type == OID_msIndirectData &&
+	     !test_bit(sinfo_has_ms_opus_info, &sinfo->aa_set))) {
+		pr_warn("Missing required AuthAttr\n");
+		return -EBADMSG;
+	}
+
+	if (ctx->msg->data_type != OID_msIndirectData &&
+	    test_bit(sinfo_has_ms_opus_info, &sinfo->aa_set)) {
+		pr_warn("Unexpected Authenticode AuthAttr\n");
+		return -EBADMSG;
+	}
 
 	/* We need to switch the 'CONT 0' to a 'SET OF' when we digest */
-	ctx->sinfo->authattrs = value - (hdrlen - 1);
-	ctx->sinfo->authattrs_len = vlen + (hdrlen - 1);
+	sinfo->authattrs = value - (hdrlen - 1);
+	sinfo->authattrs_len = vlen + (hdrlen - 1);
 	return 0;
 }
 
@@ -511,6 +632,11 @@ int pkcs7_note_signed_info(void *context, size_t hdrlen,
 	struct pkcs7_signed_info *sinfo = ctx->sinfo;
 	struct asymmetric_key_id *kid;
 
+	if (ctx->msg->data_type == OID_msIndirectData && !sinfo->authattrs) {
+		pr_warn("Authenticode requires AuthAttrs\n");
+		return -EBADMSG;
+	}
+
 	/* Generate cert issuer + serial number key ID */
 	if (!ctx->expect_skid) {
 		kid = asymmetric_key_generate_id(ctx->raw_serial,
diff --git a/crypto/asymmetric_keys/pkcs7_parser.h b/crypto/asymmetric_keys/pkcs7_parser.h
index 790dd7cec82c..a66b19ebcf47 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.h
+++ b/crypto/asymmetric_keys/pkcs7_parser.h
@@ -21,9 +21,9 @@
 struct pkcs7_signed_info {
 	struct pkcs7_signed_info *next;
 	struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
-	unsigned index;
-	bool trusted;
-	bool unsupported_crypto;	/* T if not usable due to missing crypto */
+	unsigned	index;
+	bool		trusted;
+	bool		unsupported_crypto;	/* T if not usable due to missing crypto */
 
 	/* Message digest - the digest of the Content Data (or NULL) */
 	const void	*msgdigest;
@@ -32,6 +32,14 @@ struct pkcs7_signed_info {
 	/* Authenticated Attribute data (or NULL) */
 	unsigned	authattrs_len;
 	const void	*authattrs;
+	unsigned long	aa_set;
+#define	sinfo_has_content_type		0
+#define	sinfo_has_signing_time		1
+#define	sinfo_has_message_digest	2
+#define sinfo_has_smime_caps		3
+#define	sinfo_has_ms_opus_info		4
+#define	sinfo_has_ms_statement_type	5
+	time64_t	signing_time;
 
 	/* Issuing cert serial number and issuer's name [PKCS#7 or CMS ver 1]
 	 * or issuing cert's SKID [CMS ver 3].
@@ -53,6 +61,7 @@ struct pkcs7_message {
 	struct x509_certificate *crl;	/* Revocation list */
 	struct pkcs7_signed_info *signed_infos;
 	u8		version;	/* Version of cert (1 -> PKCS#7 or CMS; 3 -> CMS) */
+	bool		have_authattrs;	/* T if have authattrs */
 
 	/* Content Data (or NULL) */
 	enum OID	data_type;	/* Type of Data */
diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 404f89a0f852..320f9a0b0ae9 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -70,9 +70,15 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7,
 	 * message digest attribute amongst them which corresponds to the
 	 * digest we just calculated.
 	 */
-	if (sinfo->msgdigest) {
+	if (sinfo->authattrs) {
 		u8 tag;
 
+		if (!sinfo->msgdigest) {
+			pr_warn("Sig %u: No messageDigest\n", sinfo->index);
+			ret = -EKEYREJECTED;
+			goto error;
+		}
+
 		if (sinfo->msgdigest_len != sinfo->sig.digest_size) {
 			pr_debug("Sig %u: Invalid digest size (%u)\n",
 				 sinfo->index, sinfo->msgdigest_len);
@@ -314,6 +320,18 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
 	pr_devel("Using X.509[%u] for sig %u\n",
 		 sinfo->signer->index, sinfo->index);
 
+	/* Check that the PKCS#7 signing time is valid according to the X.509
+	 * certificate.  We can't, however, check against the system clock
+	 * since that may not have been set yet and may be wrong.
+	 */
+	if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
+		if (sinfo->signing_time < sinfo->signer->valid_from ||
+		    sinfo->signing_time > sinfo->signer->valid_to) {
+			pr_warn("Message signed outside of X.509 validity window\n");
+			return -EKEYREJECTED;
+		}
+	}
+
 	/* Verify the PKCS#7 binary against the key */
 	ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig);
 	if (ret < 0)
@@ -328,6 +346,7 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
 /**
  * pkcs7_verify - Verify a PKCS#7 message
  * @pkcs7: The PKCS#7 message to be verified
+ * @attr_style: Whether we want authenticatedAttributes or not.
  *
  * Verify a PKCS#7 message is internally consistent - that is, the data digest
  * matches the digest in the AuthAttrs and any signature in the message or one
@@ -350,7 +369,7 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
  *  (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
  *	(note that a signature chain may be of zero length), or:
  */
-int pkcs7_verify(struct pkcs7_message *pkcs7)
+int pkcs7_verify(struct pkcs7_message *pkcs7, enum pkcs7_attr_style attr_style)
 {
 	struct pkcs7_signed_info *sinfo;
 	struct x509_certificate *x509;
@@ -359,6 +378,36 @@ int pkcs7_verify(struct pkcs7_message *pkcs7)
 
 	kenter("");
 
+	switch (attr_style) {
+	case PKCS7_REJECT_AUTHATTRS:
+		if (pkcs7->data_type != OID_data) {
+			pr_warn("Signed message is not ordinary data\n");
+			return -EKEYREJECTED;
+		}
+		if (pkcs7->have_authattrs) {
+			pr_warn("Message contains unwanted authAttrs\n");
+			return -EKEYREJECTED;
+		}
+		break;
+	case PKCS7_REQUIRE_AUTHATTRS:
+		if (pkcs7->data_type != OID_data) {
+			pr_warn("Signed message is not ordinary data\n");
+			return -EKEYREJECTED;
+		}
+		if (!pkcs7->have_authattrs) {
+			pr_warn("Message does not contain authAttrs\n");
+			return -EKEYREJECTED;
+		}
+		break;
+	case PKCS7_AUTHENTICODE_AUTHATTRS:
+		if (pkcs7->data_type != OID_msIndirectData) {
+			pr_warn("Signed message is not Authenticode\n");
+			return -EKEYREJECTED;
+		}
+		/* Authattr presence checked in parser */
+		break;
+	}
+
 	for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
 		ret = x509_get_sig_params(x509);
 		if (ret < 0)
diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c
index 2421f46184ce..d2044eeb72f4 100644
--- a/crypto/asymmetric_keys/verify_pefile.c
+++ b/crypto/asymmetric_keys/verify_pefile.c
@@ -462,7 +462,7 @@ int verify_pefile_signature(const void *pebuf, unsigned pelen,
 	if (ret < 0)
 		goto error;
 
-	ret = pkcs7_verify(pkcs7);
+	ret = pkcs7_verify(pkcs7, PKCS7_AUTHENTICODE_AUTHATTRS);
 	if (ret < 0)
 		goto error;
 
diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index e235ab4957ee..15214059f408 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -9,6 +9,9 @@
  * 2 of the Licence, or (at your option) any later version.
  */
 
+#ifndef _CRYPTO_PKCS7_H
+#define _CRYPTO_PKCS7_H
+
 struct key;
 struct pkcs7_message;
 
@@ -33,7 +36,15 @@ extern int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
 /*
  * pkcs7_verify.c
  */
-extern int pkcs7_verify(struct pkcs7_message *pkcs7);
+enum pkcs7_attr_style {
+	PKCS7_REJECT_AUTHATTRS,
+	PKCS7_REQUIRE_AUTHATTRS,
+	PKCS7_AUTHENTICODE_AUTHATTRS,
+};
+extern int pkcs7_verify(struct pkcs7_message *pkcs7,
+			enum pkcs7_attr_style attr_style);
 
 extern int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
 				      const void *data, size_t datalen);
+
+#endif /* _CRYPTO_PKCS7_H */
diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index c2bbf672b84e..93e0ff92fb9b 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -41,7 +41,7 @@ enum OID {
 	OID_signed_data,		/* 1.2.840.113549.1.7.2 */
 	/* PKCS#9 {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)} */
 	OID_email_address,		/* 1.2.840.113549.1.9.1 */
-	OID_content_type,		/* 1.2.840.113549.1.9.3 */
+	OID_contentType,		/* 1.2.840.113549.1.9.3 */
 	OID_messageDigest,		/* 1.2.840.113549.1.9.4 */
 	OID_signingTime,		/* 1.2.840.113549.1.9.5 */
 	OID_smimeCapabilites,		/* 1.2.840.113549.1.9.15 */
@@ -54,6 +54,8 @@ enum OID {
 
 	/* Microsoft Authenticode & Software Publishing */
 	OID_msIndirectData,		/* 1.3.6.1.4.1.311.2.1.4 */
+	OID_msStatementType,		/* 1.3.6.1.4.1.311.2.1.11 */
+	OID_msSpOpusInfo,		/* 1.3.6.1.4.1.311.2.1.12 */
 	OID_msPeImageDataObjId,		/* 1.3.6.1.4.1.311.2.1.15 */
 	OID_msIndividualSPKeyPurpose,	/* 1.3.6.1.4.1.311.2.1.21 */
 	OID_msOutlookExpress,		/* 1.3.6.1.4.1.311.16.4 */
diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
index 95f2dcbc7616..f9e1a75db59b 100644
--- a/kernel/system_keyring.c
+++ b/kernel/system_keyring.c
@@ -132,7 +132,7 @@ int system_verify_data(const void *data, unsigned long len,
 		goto error;
 	}
 
-	ret = pkcs7_verify(pkcs7);
+	ret = pkcs7_verify(pkcs7, PKCS7_REJECT_AUTHATTRS);
 	if (ret < 0)
 		goto error;
 
diff --git a/scripts/sign-file.c b/scripts/sign-file.c
index de213e5c0cd3..e9741e879bbd 100755
--- a/scripts/sign-file.c
+++ b/scripts/sign-file.c
@@ -111,7 +111,7 @@ int main(int argc, char **argv)
 	bool sign_only = false;
 	unsigned char buf[4096];
 	unsigned long module_size, cms_size;
-	unsigned int use_keyid = 0;
+	unsigned int use_keyid = 0, use_signed_attrs = CMS_NOATTR;
 	const EVP_MD *digest_algo;
 	EVP_PKEY *private_key;
 	CMS_ContentInfo *cms;
@@ -216,7 +216,8 @@ int main(int argc, char **argv)
 	ERR(!cms, "CMS_sign");
 
 	ERR(!CMS_add1_signer(cms, x509, private_key, digest_algo,
-			     CMS_NOCERTS | CMS_BINARY | CMS_NOSMIMECAP | use_keyid),
+			     CMS_NOCERTS | CMS_BINARY | CMS_NOSMIMECAP |
+			     use_keyid | use_signed_attrs),
 	    "CMS_sign_add_signer");
 	ERR(CMS_final(cms, bm, NULL, CMS_NOCERTS | CMS_BINARY) < 0,
 	    "CMS_final");

--
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