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 "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,%u", sinfo->index, sinfo->sig.pkey_hash_algo);

 	if (sinfo->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
 	    !hash_algo_name[sinfo->sig.pkey_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(hash_algo_name[sinfo->sig.pkey_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(digest_size + desc_size, GFP_KERNEL);
 	if (!digest)
 		goto error_no_desc;

 	desc = digest + digest_size;
 	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->msgdigest) {
 		u8 tag;

 		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,%u,%u",
 	       sinfo->index, sinfo->raw_serial_size, sinfo->raw_issuer_size);

 	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 (x509->raw_serial_size != sinfo->raw_serial_size ||
 		    memcmp(x509->raw_serial, sinfo->raw_serial,
 			   sinfo->raw_serial_size) != 0)
 			continue;
 		pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
 			 sinfo->index, certix);

 		if (x509->raw_issuer_size != sinfo->raw_issuer_size ||
 		    memcmp(x509->raw_issuer, sinfo->raw_issuer,
 			   sinfo->raw_issuer_size) != 0) {
 			pr_warn("Sig %u: X.509 subject and PKCS#7 issuer don't match\n",
 				sinfo->index);
 			continue;
 		}

 		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;
 	}
 	pr_warn("Sig %u: Issuing X.509 cert not found (#%*ph)\n",
 		sinfo->index, sinfo->raw_serial_size, sinfo->raw_serial);
 	return -ENOKEY;
 }

 /*
  * 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;
 	int ret;

 	kenter("");

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

 	for (;;) {
 		pr_debug("verify %s: %s\n", x509->subject, x509->fingerprint);
 		x509->seen = true;
 		ret = x509_get_sig_params(x509);
 		if (ret < 0)
 			return ret;

 		pr_debug("- issuer %s\n", x509->issuer);
 		if (x509->authority)
 			pr_debug("- authkeyid %s\n", x509->authority);

 		if (!x509->authority ||
 		    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)
 				return ret;
 			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.
 		 */
 		pr_debug("- want %s\n", x509->authority);
 		for (p = pkcs7->certs; p; p = p->next) {
 			pr_debug("- cmp [%u] %s\n", p->index, p->fingerprint);
 			if (p->raw_subject_size == x509->raw_issuer_size &&
 			    strcmp(p->fingerprint, x509->authority) == 0 &&
 			    memcmp(p->raw_subject, x509->raw_issuer,
 				   x509->raw_issuer_size) == 0)
 				goto found_issuer;
 		}

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

 	found_issuer:
 		pr_debug("- issuer %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();
 	}
 }

 /*
  * 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 */
 	ret = pkcs7_find_key(pkcs7, sinfo);
 	if (ret < 0)
 		return ret;

 	pr_devel("Using X.509[%u] for sig %u\n",
 		 sinfo->signer->index, sinfo->index);

 	/* 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
  */
 int pkcs7_verify(struct pkcs7_message *pkcs7)
 {
 	struct pkcs7_signed_info *sinfo;
 	struct x509_certificate *x509;
 	int ret, n;

 	kenter("");

 	for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
 		ret = x509_get_sig_params(x509);
 		if (ret < 0)
 			return ret;
 		pr_debug("X.509[%u] %s\n", n, x509->authority);
 	}

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

 	kleave(" = 0");
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pkcs7_verify);
	/* 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 "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,%u", sinfo->index, sinfo->sig.pkey_hash_algo);

	if (sinfo->sig.pkey_hash_algo >= PKEY_HASH__LAST \|\|
	!hash_algo_name[sinfo->sig.pkey_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(hash_algo_name[sinfo->sig.pkey_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(digest_size + desc_size, GFP_KERNEL);
	if (!digest)
	goto error_no_desc;

	desc = digest + digest_size;
	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->msgdigest) {
	u8 tag;

	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,%u,%u",
	sinfo->index, sinfo->raw_serial_size, sinfo->raw_issuer_size);

	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 (x509->raw_serial_size != sinfo->raw_serial_size \|\|
	memcmp(x509->raw_serial, sinfo->raw_serial,
	sinfo->raw_serial_size) != 0)
	continue;
	pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
	sinfo->index, certix);

	if (x509->raw_issuer_size != sinfo->raw_issuer_size \|\|
	memcmp(x509->raw_issuer, sinfo->raw_issuer,
	sinfo->raw_issuer_size) != 0) {
	pr_warn("Sig %u: X.509 subject and PKCS#7 issuer don't match\n",
	sinfo->index);
	continue;
	}

	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;
	}
	pr_warn("Sig %u: Issuing X.509 cert not found (#%*ph)\n",
	sinfo->index, sinfo->raw_serial_size, sinfo->raw_serial);
	return -ENOKEY;
	}

	/*
	* 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;
	int ret;

	kenter("");

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

	for (;;) {
	pr_debug("verify %s: %s\n", x509->subject, x509->fingerprint);
	x509->seen = true;
	ret = x509_get_sig_params(x509);
	if (ret < 0)
	return ret;

	pr_debug("- issuer %s\n", x509->issuer);
	if (x509->authority)
	pr_debug("- authkeyid %s\n", x509->authority);

	if (!x509->authority \|\|
	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)
	return ret;
	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.
	*/
	pr_debug("- want %s\n", x509->authority);
	for (p = pkcs7->certs; p; p = p->next) {
	pr_debug("- cmp [%u] %s\n", p->index, p->fingerprint);
	if (p->raw_subject_size == x509->raw_issuer_size &&
	strcmp(p->fingerprint, x509->authority) == 0 &&
	memcmp(p->raw_subject, x509->raw_issuer,
	x509->raw_issuer_size) == 0)
	goto found_issuer;
	}

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

	found_issuer:
	pr_debug("- issuer %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();
	}
	}

	/*
	* 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 */
	ret = pkcs7_find_key(pkcs7, sinfo);
	if (ret < 0)
	return ret;

	pr_devel("Using X.509[%u] for sig %u\n",
	sinfo->signer->index, sinfo->index);

	/* 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
	*/
	int pkcs7_verify(struct pkcs7_message *pkcs7)
	{
	struct pkcs7_signed_info *sinfo;
	struct x509_certificate *x509;
	int ret, n;

	kenter("");

	for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) {
	ret = x509_get_sig_params(x509);
	if (ret < 0)
	return ret;
	pr_debug("X.509[%u] %s\n", n, x509->authority);
	}

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

	kleave(" = 0");
	return 0;
	}
	EXPORT_SYMBOL_GPL(pkcs7_verify);