// SPDX-License-Identifier: GPL-2.0-or-later

  /* Verify the signature on a PKCS#7 message.
   *
   * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */
  
  #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/hash_info.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 public_key_signature *sig = sinfo->sig;

  	struct crypto_shash *tfm;
  	struct shash_desc *desc;

  	size_t desc_size;

  	int ret;

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

  	/* The digest was calculated already. */
  	if (sig->digest)
  		return 0;

  	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);

  	sig->digest_size = crypto_shash_digestsize(tfm);

  
  	ret = -ENOMEM;

  	sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
  	if (!sig->digest)
  		goto error_no_desc;
  
  	desc = kzalloc(desc_size, GFP_KERNEL);
  	if (!desc)

  		goto error_no_desc;

  	desc->tfm   = tfm;

  
  	/* Digest the message [RFC2315 9.3] */

  	ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len,
  				  sig->digest);

  	if (ret < 0)
  		goto error;

  	pr_devel("MsgDigest = [%*ph]
  ", 8, sig->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
  ", sinfo->index);
  			ret = -EKEYREJECTED;
  			goto error;
  		}

  		if (sinfo->msgdigest_len != sig->digest_size) {

  			pr_debug("Sig %u: Invalid digest size (%u)
  ",
  				 sinfo->index, sinfo->msgdigest_len);
  			ret = -EBADMSG;
  			goto error;
  		}

  		if (memcmp(sig->digest, sinfo->msgdigest,
  			   sinfo->msgdigest_len) != 0) {

  			pr_debug("Sig %u: Message digest doesn't match
  ",
  				 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(sig->digest, 0, 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, sig->digest);

  		if (ret < 0)
  			goto error;

  		pr_devel("AADigest = [%*ph]
  ", 8, sig->digest);

  	}

  error:

  	kfree(desc);

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

  int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf, u32 *len,
  		     enum hash_algo *hash_algo)
  {
  	struct pkcs7_signed_info *sinfo = pkcs7->signed_infos;
  	int i, ret;
  
  	/*
  	 * This function doesn't support messages with more than one signature.
  	 */
  	if (sinfo == NULL || sinfo->next != NULL)
  		return -EBADMSG;
  
  	ret = pkcs7_digest(pkcs7, sinfo);
  	if (ret)
  		return ret;
  
  	*buf = sinfo->sig->digest;
  	*len = sinfo->sig->digest_size;

  	i = match_string(hash_algo_name, HASH_ALGO__LAST,
  			 sinfo->sig->hash_algo);
  	if (i >= 0)
  		*hash_algo = i;

  
  	return 0;
  }

  /*

   * 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->sig->auth_ids[0]))

  			continue;
  		pr_devel("Sig %u: Found cert serial match X.509[%u]
  ",
  			 sinfo->index, certix);

  		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)
  ",
  		 sinfo->index,

  		 sinfo->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->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 public_key_signature *sig;

  	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
  ",
  			 x509->subject,
  			 x509->raw_serial_size, x509->raw_serial);

  		x509->seen = true;

  
  		if (x509->blacklisted) {
  			/* If this cert is blacklisted, then mark everything
  			 * that depends on this as blacklisted too.
  			 */
  			sinfo->blacklisted = true;
  			for (p = sinfo->signer; p != x509; p = p->signer)
  				p->blacklisted = true;
  			pr_debug("- blacklisted
  ");
  			return 0;
  		}

  		if (x509->unsupported_key)
  			goto unsupported_crypto_in_x509;

  		pr_debug("- issuer %s
  ", x509->issuer);

  		sig = x509->sig;
  		if (sig->auth_ids[0])

  			pr_debug("- authkeyid.id %*phN
  ",

  				 sig->auth_ids[0]->len, sig->auth_ids[0]->data);
  		if (sig->auth_ids[1])

  			pr_debug("- authkeyid.skid %*phN
  ",

  				 sig->auth_ids[1]->len, sig->auth_ids[1]->data);

  		if (x509->self_signed) {

  			/* 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.
  			 */

  			if (x509->unsupported_sig)
  				goto unsupported_crypto_in_x509;

  			x509->signer = x509;
  			pr_debug("- self-signed
  ");
  			return 0;
  		}
  
  		/* Look through the X.509 certificates in the PKCS#7 message's
  		 * list to see if the next one is there.
  		 */

  		auth = sig->auth_ids[0];

  		if (auth) {
  			pr_debug("- want %*phN
  ", auth->len, auth->data);
  			for (p = pkcs7->certs; p; p = p->next) {
  				pr_debug("- cmp [%u] %*phN
  ",
  					 p->index, p->id->len, p->id->data);
  				if (asymmetric_key_id_same(p->id, auth))
  					goto found_issuer_check_skid;
  			}

  		} else if (sig->auth_ids[1]) {

  			auth = sig->auth_ids[1];

  			pr_debug("- want %*phN
  ", auth->len, auth->data);
  			for (p = pkcs7->certs; p; p = p->next) {
  				if (!p->skid)
  					continue;
  				pr_debug("- cmp [%u] %*phN
  ",
  					 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
  ");
  		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 (sig->auth_ids[1] &&
  		    !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {

  			pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)
  ",
  				sinfo->index, x509->index, p->index);
  			return -EKEYREJECTED;
  		}

  	found_issuer:

  		pr_debug("- subject %s
  ", p->subject);

  		if (p->seen) {
  			pr_warn("Sig %u: X.509 chain contains loop
  ",
  				sinfo->index);
  			return 0;
  		}

  		ret = public_key_verify_signature(p->pub, x509->sig);

  		if (ret < 0)
  			return ret;
  		x509->signer = p;
  		if (x509 == p) {
  			pr_debug("- self-signed
  ");
  			return 0;
  		}
  		x509 = p;
  		might_sleep();
  	}

  unsupported_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->unsupported_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.
  	 */

  	return 0;

  }
  
  /*

   * 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
  ",
  		 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
  ");
  			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
  ", 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:
   *

   *  (*) 0 if a signature chain passed verification, or:

   *

   *  (*) -EKEYREJECTED if a blacklisted key was encountered, or:
   *
   *  (*) -ENOPKG if none of the signature chains are verifiable because suitable
   *	crypto modules couldn't be found.

   */

  int pkcs7_verify(struct pkcs7_message *pkcs7,
  		 enum key_being_used_for usage)

  {
  	struct pkcs7_signed_info *sinfo;

  	int actual_ret = -ENOPKG;

  	int ret;

  
  	kenter("");

  	switch (usage) {
  	case VERIFYING_MODULE_SIGNATURE:
  		if (pkcs7->data_type != OID_data) {
  			pr_warn("Invalid module sig (not pkcs7-data)
  ");
  			return -EKEYREJECTED;
  		}
  		if (pkcs7->have_authattrs) {
  			pr_warn("Invalid module sig (has authattrs)
  ");
  			return -EKEYREJECTED;
  		}
  		break;
  	case VERIFYING_FIRMWARE_SIGNATURE:
  		if (pkcs7->data_type != OID_data) {
  			pr_warn("Invalid firmware sig (not pkcs7-data)
  ");
  			return -EKEYREJECTED;
  		}
  		if (!pkcs7->have_authattrs) {
  			pr_warn("Invalid firmware sig (missing authattrs)
  ");
  			return -EKEYREJECTED;
  		}
  		break;
  	case VERIFYING_KEXEC_PE_SIGNATURE:
  		if (pkcs7->data_type != OID_msIndirectData) {
  			pr_warn("Invalid kexec sig (not Authenticode)
  ");
  			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)
  ");
  			return -EKEYREJECTED;
  		}
  		break;
  	default:
  		return -EINVAL;
  	}

  	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
  		ret = pkcs7_verify_one(pkcs7, sinfo);

  		if (sinfo->blacklisted) {
  			if (actual_ret == -ENOPKG)
  				actual_ret = -EKEYREJECTED;
  			continue;
  		}

  		if (ret < 0) {

  			if (ret == -ENOPKG) {
  				sinfo->unsupported_crypto = true;
  				continue;
  			}

  			kleave(" = %d", ret);
  			return ret;
  		}

  		actual_ret = 0;

  	}

  	kleave(" = %d", actual_ret);
  	return actual_ret;

  }
  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
  ");
  		return -EINVAL;
  	}
  	pkcs7->data = data;
  	pkcs7->data_len = datalen;
  	return 0;
  }