crypto/asymmetric_keys/pkcs7_verify.c - kernel/msm-4.9 - Gitiles

 /* Verify the signature on a PKCS#7 message.
  *
  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public Licence
  * as published by the Free Software Foundation; either version
  * 2 of the Licence, or (at your option) any later version.
  */

 #define pr_fmt(fmt) "PKCS7: "fmt
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/asn1.h>
 #include <crypto/hash.h>
 #include <crypto/public_key.h>
 #include "pkcs7_parser.h"

 /*
  * Digest the relevant parts of the PKCS#7 data
  */
 static int pkcs7_digest(struct pkcs7_message *pkcs7,
 			struct pkcs7_signed_info *sinfo)
 {
 	struct crypto_shash *tfm;
 	struct shash_desc *desc;
 	size_t digest_size, desc_size;
 	void *digest;
 	int ret;

 	kenter(",%u,%s", sinfo->index, sinfo->sig.hash_algo);

 	if (!sinfo->sig.hash_algo)
 		return -ENOPKG;

 	/* Allocate the hashing algorithm we're going to need and find out how
 	 * big the hash operational data will be.
 	 */
 	tfm = crypto_alloc_shash(sinfo->sig.hash_algo, 0, 0);
 	if (IS_ERR(tfm))
 		return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);

 	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
 	sinfo->sig.digest_size = digest_size = crypto_shash_digestsize(tfm);

 	ret = -ENOMEM;
 	digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
 			 GFP_KERNEL);
 	if (!digest)
 		goto error_no_desc;

 	desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
 	desc->tfm   = tfm;
 	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

 	/* Digest the message [RFC2315 9.3] */
 	ret = crypto_shash_init(desc);
 	if (ret < 0)
 		goto error;
 	ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, digest);
 	if (ret < 0)
 		goto error;
 	pr_devel("MsgDigest = [%*ph]\n", 8, digest);

 	/* However, if there are authenticated attributes, there must be a
 	 * message digest attribute amongst them which corresponds to the
 	 * digest we just calculated.
 	 */
 	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);
 			ret = -EBADMSG;
 			goto error;
 		}

 		if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) {
 			pr_debug("Sig %u: Message digest doesn't match\n",
 				 sinfo->index);
 			ret = -EKEYREJECTED;
 			goto error;
 		}

 		/* We then calculate anew, using the authenticated attributes
 		 * as the contents of the digest instead.  Note that we need to
 		 * convert the attributes from a CONT.0 into a SET before we
 		 * hash it.
 		 */
 		memset(digest, 0, sinfo->sig.digest_size);

 		ret = crypto_shash_init(desc);
 		if (ret < 0)
 			goto error;
 		tag = ASN1_CONS_BIT | ASN1_SET;
 		ret = crypto_shash_update(desc, &tag, 1);
 		if (ret < 0)
 			goto error;
 		ret = crypto_shash_finup(desc, sinfo->authattrs,
 					 sinfo->authattrs_len, digest);
 		if (ret < 0)
 			goto error;
 		pr_devel("AADigest = [%*ph]\n", 8, digest);
 	}

 	sinfo->sig.digest = digest;
 	digest = NULL;

 error:
 	kfree(digest);
 error_no_desc:
 	crypto_free_shash(tfm);
 	kleave(" = %d", ret);
 	return ret;
 }

 /*
  * Find the key (X.509 certificate) to use to verify a PKCS#7 message.  PKCS#7
  * uses the issuer's name and the issuing certificate serial number for
  * matching purposes.  These must match the certificate issuer's name (not
  * subject's name) and the certificate serial number [RFC 2315 6.7].
  */
 static int pkcs7_find_key(struct pkcs7_message *pkcs7,
 			  struct pkcs7_signed_info *sinfo)
 {
 	struct x509_certificate *x509;
 	unsigned certix = 1;

 	kenter("%u", sinfo->index);

 	for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
 		/* I'm _assuming_ that the generator of the PKCS#7 message will
 		 * encode the fields from the X.509 cert in the same way in the
 		 * PKCS#7 message - but I can't be 100% sure of that.  It's
 		 * possible this will need element-by-element comparison.
 		 */
 		if (!asymmetric_key_id_same(x509->id, sinfo->signing_cert_id))
 			continue;
 		pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
 			 sinfo->index, certix);

 		if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) {
 			pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
 				sinfo->index);
 			continue;
 		}

 		sinfo->signer = x509;
 		return 0;
 	}

 	/* The relevant X.509 cert isn't found here, but it might be found in
 	 * the trust keyring.
 	 */
 	pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
 		 sinfo->index,
 		 sinfo->signing_cert_id->len, sinfo->signing_cert_id->data);
 	return 0;
 }

 /*
  * Verify the internal certificate chain as best we can.
  */
 static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
 				  struct pkcs7_signed_info *sinfo)
 {
 	struct x509_certificate *x509 = sinfo->signer, *p;
 	struct asymmetric_key_id *auth;
 	int ret;

 	kenter("");

 	for (p = pkcs7->certs; p; p = p->next)
 		p->seen = false;

 	for (;;) {
 		pr_debug("verify %s: %*phN\n",
 			 x509->subject,
 			 x509->raw_serial_size, x509->raw_serial);
 		x509->seen = true;
 		ret = x509_get_sig_params(x509);
 		if (ret < 0)
 			goto maybe_missing_crypto_in_x509;

 		pr_debug("- issuer %s\n", x509->issuer);
 		if (x509->akid_id)
 			pr_debug("- authkeyid.id %*phN\n",
 				 x509->akid_id->len, x509->akid_id->data);
 		if (x509->akid_skid)
 			pr_debug("- authkeyid.skid %*phN\n",
 				 x509->akid_skid->len, x509->akid_skid->data);

 		if ((!x509->akid_id && !x509->akid_skid) ||
 		    strcmp(x509->subject, x509->issuer) == 0) {
 			/* If there's no authority certificate specified, then
 			 * the certificate must be self-signed and is the root
 			 * of the chain.  Likewise if the cert is its own
 			 * authority.
 			 */
 			pr_debug("- no auth?\n");
 			if (x509->raw_subject_size != x509->raw_issuer_size ||
 			    memcmp(x509->raw_subject, x509->raw_issuer,
 				   x509->raw_issuer_size) != 0)
 				return 0;

 			ret = x509_check_signature(x509->pub, x509);
 			if (ret < 0)
 				goto maybe_missing_crypto_in_x509;
 			x509->signer = x509;
 			pr_debug("- self-signed\n");
 			return 0;
 		}

 		/* Look through the X.509 certificates in the PKCS#7 message's
 		 * list to see if the next one is there.
 		 */
 		auth = x509->akid_id;
 		if (auth) {
 			pr_debug("- want %*phN\n", auth->len, auth->data);
 			for (p = pkcs7->certs; p; p = p->next) {
 				pr_debug("- cmp [%u] %*phN\n",
 					 p->index, p->id->len, p->id->data);
 				if (asymmetric_key_id_same(p->id, auth))
 					goto found_issuer_check_skid;
 			}
 		} else {
 			auth = x509->akid_skid;
 			pr_debug("- want %*phN\n", auth->len, auth->data);
 			for (p = pkcs7->certs; p; p = p->next) {
 				if (!p->skid)
 					continue;
 				pr_debug("- cmp [%u] %*phN\n",
 					 p->index, p->skid->len, p->skid->data);
 				if (asymmetric_key_id_same(p->skid, auth))
 					goto found_issuer;
 			}
 		}

 		/* We didn't find the root of this chain */
 		pr_debug("- top\n");
 		return 0;

 	found_issuer_check_skid:
 		/* We matched issuer + serialNumber, but if there's an
 		 * authKeyId.keyId, that must match the CA subjKeyId also.
 		 */
 		if (x509->akid_skid &&
 		    !asymmetric_key_id_same(p->skid, x509->akid_skid)) {
 			pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
 				sinfo->index, x509->index, p->index);
 			return -EKEYREJECTED;
 		}
 	found_issuer:
 		pr_debug("- subject %s\n", p->subject);
 		if (p->seen) {
 			pr_warn("Sig %u: X.509 chain contains loop\n",
 				sinfo->index);
 			return 0;
 		}
 		ret = x509_check_signature(p->pub, x509);
 		if (ret < 0)
 			return ret;
 		x509->signer = p;
 		if (x509 == p) {
 			pr_debug("- self-signed\n");
 			return 0;
 		}
 		x509 = p;
 		might_sleep();
 	}

 maybe_missing_crypto_in_x509:
 	/* Just prune the certificate chain at this point if we lack some
 	 * crypto module to go further.  Note, however, we don't want to set
 	 * sinfo->missing_crypto as the signed info block may still be
 	 * validatable against an X.509 cert lower in the chain that we have a
 	 * trusted copy of.
 	 */
 	if (ret == -ENOPKG)
 		return 0;
 	return ret;
 }

 /*
  * Verify one signed information block from a PKCS#7 message.
  */
 static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
 			    struct pkcs7_signed_info *sinfo)
 {
 	int ret;

 	kenter(",%u", sinfo->index);

 	/* First of all, digest the data in the PKCS#7 message and the
 	 * signed information block
 	 */
 	ret = pkcs7_digest(pkcs7, sinfo);
 	if (ret < 0)
 		return ret;

 	/* Find the key for the signature if there is one */
 	ret = pkcs7_find_key(pkcs7, sinfo);
 	if (ret < 0)
 		return ret;

 	if (!sinfo->signer)
 		return 0;

 	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)
 		return ret;

 	pr_devel("Verified signature %u\n", sinfo->index);

 	/* Verify the internal certificate chain */
 	return pkcs7_verify_sig_chain(pkcs7, sinfo);
 }

 /**
  * pkcs7_verify - Verify a PKCS#7 message
  * @pkcs7: The PKCS#7 message to be verified
  * @usage: The use to which the key is being put
  *
  * 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
  * of the X.509 certificates it carries that matches another X.509 cert in the
  * message can be verified.
  *
  * This does not look to match the contents of the PKCS#7 message against any
  * external public keys.
  *
  * Returns, in order of descending priority:
  *
  *  (*) -EKEYREJECTED if a key was selected that had a usage restriction at
  *      odds with the specified usage, or:
  *
  *  (*) -EKEYREJECTED if a signature failed to match for which we found an
  *	appropriate X.509 certificate, or:
  *
  *  (*) -EBADMSG if some part of the message was invalid, or:
  *
  *  (*) -ENOPKG if none of the signature chains are verifiable because suitable
  *	crypto modules couldn't be found, or:
  *
  *  (*) 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,
 		 enum key_being_used_for usage)
 {
 	struct pkcs7_signed_info *sinfo;
 	struct x509_certificate *x509;
 	int enopkg = -ENOPKG;
 	int ret, n;

 	kenter("");

 	switch (usage) {
 	case VERIFYING_MODULE_SIGNATURE:
 		if (pkcs7->data_type != OID_data) {
 			pr_warn("Invalid module sig (not pkcs7-data)\n");
 			return -EKEYREJECTED;
 		}
 		if (pkcs7->have_authattrs) {
 			pr_warn("Invalid module sig (has authattrs)\n");
 			return -EKEYREJECTED;
 		}
 		break;
 	case VERIFYING_FIRMWARE_SIGNATURE:
 		if (pkcs7->data_type != OID_data) {
 			pr_warn("Invalid firmware sig (not pkcs7-data)\n");
 			return -EKEYREJECTED;
 		}
 		if (!pkcs7->have_authattrs) {
 			pr_warn("Invalid firmware sig (missing authattrs)\n");
 			return -EKEYREJECTED;
 		}
 		break;
 	case VERIFYING_KEXEC_PE_SIGNATURE:
 		if (pkcs7->data_type != OID_msIndirectData) {
 			pr_warn("Invalid kexec sig (not Authenticode)\n");
 			return -EKEYREJECTED;
 		}
 		/* Authattr presence checked in parser */
 		break;
 	case VERIFYING_UNSPECIFIED_SIGNATURE:
 		if (pkcs7->data_type != OID_data) {
 			pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
 			return -EKEYREJECTED;
 		}
 		break;
 	default:
 		return -EINVAL;
 	}

 	for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
 		ret = x509_get_sig_params(x509);
 		if (ret < 0)
 			return ret;
 	}

 	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
 		ret = pkcs7_verify_one(pkcs7, sinfo);
 		if (ret < 0) {
 			if (ret == -ENOPKG) {
 				sinfo->unsupported_crypto = true;
 				continue;
 			}
 			kleave(" = %d", ret);
 			return ret;
 		}
 		enopkg = 0;
 	}

 	kleave(" = %d", enopkg);
 	return enopkg;
 }
 EXPORT_SYMBOL_GPL(pkcs7_verify);

 /**
  * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
  * @pkcs7: The PKCS#7 message
  * @data: The data to be verified
  * @datalen: The amount of data
  *
  * Supply the detached data needed to verify a PKCS#7 message.  Note that no
  * attempt to retain/pin the data is made.  That is left to the caller.  The
  * data will not be modified by pkcs7_verify() and will not be freed when the
  * PKCS#7 message is freed.
  *
  * Returns -EINVAL if data is already supplied in the message, 0 otherwise.
  */
 int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
 			       const void *data, size_t datalen)
 {
 	if (pkcs7->data) {
 		pr_debug("Data already supplied\n");
 		return -EINVAL;
 	}
 	pkcs7->data = data;
 	pkcs7->data_len = datalen;
 	return 0;
 }
	/* Verify the signature on a PKCS#7 message.
	*
	* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public Licence
	* as published by the Free Software Foundation; either version
	* 2 of the Licence, or (at your option) any later version.
	*/

	#define pr_fmt(fmt) "PKCS7: "fmt
	#include <linux/kernel.h>
	#include <linux/export.h>
	#include <linux/slab.h>
	#include <linux/err.h>
	#include <linux/asn1.h>
	#include <crypto/hash.h>
	#include <crypto/public_key.h>
	#include "pkcs7_parser.h"

	/*
	* Digest the relevant parts of the PKCS#7 data
	*/
	static int pkcs7_digest(struct pkcs7_message *pkcs7,
	struct pkcs7_signed_info *sinfo)
	{
	struct crypto_shash *tfm;
	struct shash_desc *desc;
	size_t digest_size, desc_size;
	void *digest;
	int ret;

	kenter(",%u,%s", sinfo->index, sinfo->sig.hash_algo);

	if (!sinfo->sig.hash_algo)
	return -ENOPKG;

	/* Allocate the hashing algorithm we're going to need and find out how
	* big the hash operational data will be.
	*/
	tfm = crypto_alloc_shash(sinfo->sig.hash_algo, 0, 0);
	if (IS_ERR(tfm))
	return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);

	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
	sinfo->sig.digest_size = digest_size = crypto_shash_digestsize(tfm);

	ret = -ENOMEM;
	digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
	GFP_KERNEL);
	if (!digest)
	goto error_no_desc;

	desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
	desc->tfm = tfm;
	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

	/* Digest the message [RFC2315 9.3] */
	ret = crypto_shash_init(desc);
	if (ret < 0)
	goto error;
	ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, digest);
	if (ret < 0)
	goto error;
	pr_devel("MsgDigest = [%*ph]\n", 8, digest);

	/* However, if there are authenticated attributes, there must be a
	* message digest attribute amongst them which corresponds to the
	* digest we just calculated.
	*/
	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);
	ret = -EBADMSG;
	goto error;
	}

	if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) {
	pr_debug("Sig %u: Message digest doesn't match\n",
	sinfo->index);
	ret = -EKEYREJECTED;
	goto error;
	}

	/* We then calculate anew, using the authenticated attributes
	* as the contents of the digest instead. Note that we need to
	* convert the attributes from a CONT.0 into a SET before we
	* hash it.
	*/
	memset(digest, 0, sinfo->sig.digest_size);

	ret = crypto_shash_init(desc);
	if (ret < 0)
	goto error;
	tag = ASN1_CONS_BIT \| ASN1_SET;
	ret = crypto_shash_update(desc, &tag, 1);
	if (ret < 0)
	goto error;
	ret = crypto_shash_finup(desc, sinfo->authattrs,
	sinfo->authattrs_len, digest);
	if (ret < 0)
	goto error;
	pr_devel("AADigest = [%*ph]\n", 8, digest);
	}

	sinfo->sig.digest = digest;
	digest = NULL;

	error:
	kfree(digest);
	error_no_desc:
	crypto_free_shash(tfm);
	kleave(" = %d", ret);
	return ret;
	}

	/*
	* Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
	* uses the issuer's name and the issuing certificate serial number for
	* matching purposes. These must match the certificate issuer's name (not
	* subject's name) and the certificate serial number [RFC 2315 6.7].
	*/
	static int pkcs7_find_key(struct pkcs7_message *pkcs7,
	struct pkcs7_signed_info *sinfo)
	{
	struct x509_certificate *x509;
	unsigned certix = 1;

	kenter("%u", sinfo->index);

	for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
	/* I'm _assuming_ that the generator of the PKCS#7 message will
	* encode the fields from the X.509 cert in the same way in the
	* PKCS#7 message - but I can't be 100% sure of that. It's
	* possible this will need element-by-element comparison.
	*/
	if (!asymmetric_key_id_same(x509->id, sinfo->signing_cert_id))
	continue;
	pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
	sinfo->index, certix);

	if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) {
	pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
	sinfo->index);
	continue;
	}

	sinfo->signer = x509;
	return 0;
	}

	/* The relevant X.509 cert isn't found here, but it might be found in
	* the trust keyring.
	*/
	pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n",
	sinfo->index,
	sinfo->signing_cert_id->len, sinfo->signing_cert_id->data);
	return 0;
	}

	/*
	* Verify the internal certificate chain as best we can.
	*/
	static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
	struct pkcs7_signed_info *sinfo)
	{
	struct x509_certificate x509 = sinfo->signer, p;
	struct asymmetric_key_id *auth;
	int ret;

	kenter("");

	for (p = pkcs7->certs; p; p = p->next)
	p->seen = false;

	for (;;) {
	pr_debug("verify %s: %*phN\n",
	x509->subject,
	x509->raw_serial_size, x509->raw_serial);
	x509->seen = true;
	ret = x509_get_sig_params(x509);
	if (ret < 0)
	goto maybe_missing_crypto_in_x509;

	pr_debug("- issuer %s\n", x509->issuer);
	if (x509->akid_id)
	pr_debug("- authkeyid.id %*phN\n",
	x509->akid_id->len, x509->akid_id->data);
	if (x509->akid_skid)
	pr_debug("- authkeyid.skid %*phN\n",
	x509->akid_skid->len, x509->akid_skid->data);

	if ((!x509->akid_id && !x509->akid_skid) \|\|
	strcmp(x509->subject, x509->issuer) == 0) {
	/* If there's no authority certificate specified, then
	* the certificate must be self-signed and is the root
	* of the chain. Likewise if the cert is its own
	* authority.
	*/
	pr_debug("- no auth?\n");
	if (x509->raw_subject_size != x509->raw_issuer_size \|\|
	memcmp(x509->raw_subject, x509->raw_issuer,
	x509->raw_issuer_size) != 0)
	return 0;

	ret = x509_check_signature(x509->pub, x509);
	if (ret < 0)
	goto maybe_missing_crypto_in_x509;
	x509->signer = x509;
	pr_debug("- self-signed\n");
	return 0;
	}

	/* Look through the X.509 certificates in the PKCS#7 message's
	* list to see if the next one is there.
	*/
	auth = x509->akid_id;
	if (auth) {
	pr_debug("- want %*phN\n", auth->len, auth->data);
	for (p = pkcs7->certs; p; p = p->next) {
	pr_debug("- cmp [%u] %*phN\n",
	p->index, p->id->len, p->id->data);
	if (asymmetric_key_id_same(p->id, auth))
	goto found_issuer_check_skid;
	}
	} else {
	auth = x509->akid_skid;
	pr_debug("- want %*phN\n", auth->len, auth->data);
	for (p = pkcs7->certs; p; p = p->next) {
	if (!p->skid)
	continue;
	pr_debug("- cmp [%u] %*phN\n",
	p->index, p->skid->len, p->skid->data);
	if (asymmetric_key_id_same(p->skid, auth))
	goto found_issuer;
	}
	}

	/* We didn't find the root of this chain */
	pr_debug("- top\n");
	return 0;

	found_issuer_check_skid:
	/* We matched issuer + serialNumber, but if there's an
	* authKeyId.keyId, that must match the CA subjKeyId also.
	*/
	if (x509->akid_skid &&
	!asymmetric_key_id_same(p->skid, x509->akid_skid)) {
	pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
	sinfo->index, x509->index, p->index);
	return -EKEYREJECTED;
	}
	found_issuer:
	pr_debug("- subject %s\n", p->subject);
	if (p->seen) {
	pr_warn("Sig %u: X.509 chain contains loop\n",
	sinfo->index);
	return 0;
	}
	ret = x509_check_signature(p->pub, x509);
	if (ret < 0)
	return ret;
	x509->signer = p;
	if (x509 == p) {
	pr_debug("- self-signed\n");
	return 0;
	}
	x509 = p;
	might_sleep();
	}

	maybe_missing_crypto_in_x509:
	/* Just prune the certificate chain at this point if we lack some
	* crypto module to go further. Note, however, we don't want to set
	* sinfo->missing_crypto as the signed info block may still be
	* validatable against an X.509 cert lower in the chain that we have a
	* trusted copy of.
	*/
	if (ret == -ENOPKG)
	return 0;
	return ret;
	}

	/*
	* Verify one signed information block from a PKCS#7 message.
	*/
	static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
	struct pkcs7_signed_info *sinfo)
	{
	int ret;

	kenter(",%u", sinfo->index);

	/* First of all, digest the data in the PKCS#7 message and the
	* signed information block
	*/
	ret = pkcs7_digest(pkcs7, sinfo);
	if (ret < 0)
	return ret;

	/* Find the key for the signature if there is one */
	ret = pkcs7_find_key(pkcs7, sinfo);
	if (ret < 0)
	return ret;

	if (!sinfo->signer)
	return 0;

	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)
	return ret;

	pr_devel("Verified signature %u\n", sinfo->index);

	/* Verify the internal certificate chain */
	return pkcs7_verify_sig_chain(pkcs7, sinfo);
	}

	/**
	* pkcs7_verify - Verify a PKCS#7 message
	* @pkcs7: The PKCS#7 message to be verified
	* @usage: The use to which the key is being put
	*
	* 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
	* of the X.509 certificates it carries that matches another X.509 cert in the
	* message can be verified.
	*
	* This does not look to match the contents of the PKCS#7 message against any
	* external public keys.
	*
	* Returns, in order of descending priority:
	*
	* (*) -EKEYREJECTED if a key was selected that had a usage restriction at
	* odds with the specified usage, or:
	*
	* (*) -EKEYREJECTED if a signature failed to match for which we found an
	* appropriate X.509 certificate, or:
	*
	* (*) -EBADMSG if some part of the message was invalid, or:
	*
	* (*) -ENOPKG if none of the signature chains are verifiable because suitable
	* crypto modules couldn't be found, or:
	*
	* (*) 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,
	enum key_being_used_for usage)
	{
	struct pkcs7_signed_info *sinfo;
	struct x509_certificate *x509;
	int enopkg = -ENOPKG;
	int ret, n;

	kenter("");

	switch (usage) {
	case VERIFYING_MODULE_SIGNATURE:
	if (pkcs7->data_type != OID_data) {
	pr_warn("Invalid module sig (not pkcs7-data)\n");
	return -EKEYREJECTED;
	}
	if (pkcs7->have_authattrs) {
	pr_warn("Invalid module sig (has authattrs)\n");
	return -EKEYREJECTED;
	}
	break;
	case VERIFYING_FIRMWARE_SIGNATURE:
	if (pkcs7->data_type != OID_data) {
	pr_warn("Invalid firmware sig (not pkcs7-data)\n");
	return -EKEYREJECTED;
	}
	if (!pkcs7->have_authattrs) {
	pr_warn("Invalid firmware sig (missing authattrs)\n");
	return -EKEYREJECTED;
	}
	break;
	case VERIFYING_KEXEC_PE_SIGNATURE:
	if (pkcs7->data_type != OID_msIndirectData) {
	pr_warn("Invalid kexec sig (not Authenticode)\n");
	return -EKEYREJECTED;
	}
	/* Authattr presence checked in parser */
	break;
	case VERIFYING_UNSPECIFIED_SIGNATURE:
	if (pkcs7->data_type != OID_data) {
	pr_warn("Invalid unspecified sig (not pkcs7-data)\n");
	return -EKEYREJECTED;
	}
	break;
	default:
	return -EINVAL;
	}

	for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
	ret = x509_get_sig_params(x509);
	if (ret < 0)
	return ret;
	}

	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
	ret = pkcs7_verify_one(pkcs7, sinfo);
	if (ret < 0) {
	if (ret == -ENOPKG) {
	sinfo->unsupported_crypto = true;
	continue;
	}
	kleave(" = %d", ret);
	return ret;
	}
	enopkg = 0;
	}

	kleave(" = %d", enopkg);
	return enopkg;
	}
	EXPORT_SYMBOL_GPL(pkcs7_verify);

	/**
	* pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message
	* @pkcs7: The PKCS#7 message
	* @data: The data to be verified
	* @datalen: The amount of data
	*
	* Supply the detached data needed to verify a PKCS#7 message. Note that no
	* attempt to retain/pin the data is made. That is left to the caller. The
	* data will not be modified by pkcs7_verify() and will not be freed when the
	* PKCS#7 message is freed.
	*
	* Returns -EINVAL if data is already supplied in the message, 0 otherwise.
	*/
	int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7,
	const void *data, size_t datalen)
	{
	if (pkcs7->data) {
	pr_debug("Data already supplied\n");
	return -EINVAL;
	}
	pkcs7->data = data;
	pkcs7->data_len = datalen;
	return 0;
	}