crypto/asymmetric_keys/x509_public_key.c - pub/scm/linux/kernel/git/davidlohr/tip - Git at Google

 /* Instantiate a public key crypto key from an X.509 Certificate
  *
  * 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) "X.509: "fmt
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/mpi.h>
 #include <linux/asn1_decoder.h>
 #include <keys/asymmetric-subtype.h>
 #include <keys/asymmetric-parser.h>
 #include <keys/system_keyring.h>
 #include <crypto/hash.h>
 #include "asymmetric_keys.h"
 #include "public_key.h"
 #include "x509_parser.h"

 static bool use_builtin_keys;
 static char *ca_keyid;

 #ifndef MODULE
 static int __init ca_keys_setup(char *str)
 {
 	if (!str)		/* default system keyring */
 		return 1;

 	if (strncmp(str, "id:", 3) == 0)
 		ca_keyid = str;	/* owner key 'id:xxxxxx' */
 	else if (strcmp(str, "builtin") == 0)
 		use_builtin_keys = true;

 	return 1;
 }
 __setup("ca_keys=", ca_keys_setup);
 #endif

 /**
  * x509_request_asymmetric_key - Request a key by X.509 certificate params.
  * @keyring: The keys to search.
  * @subject: The name of the subject to whom the key belongs.
  * @key_id: The subject key ID as a hex string.
  *
  * Find a key in the given keyring by subject name and key ID.  These might,
  * for instance, be the issuer name and the authority key ID of an X.509
  * certificate that needs to be verified.
  */
 struct key *x509_request_asymmetric_key(struct key *keyring,
 					const char *subject,
 					const char *key_id)
 {
 	key_ref_t key;
 	size_t subject_len = strlen(subject), key_id_len = strlen(key_id);
 	char *id;

 	/* Construct an identifier "<subjname>:<keyid>". */
 	id = kmalloc(subject_len + 2 + key_id_len + 1, GFP_KERNEL);
 	if (!id)
 		return ERR_PTR(-ENOMEM);

 	memcpy(id, subject, subject_len);
 	id[subject_len + 0] = ':';
 	id[subject_len + 1] = ' ';
 	memcpy(id + subject_len + 2, key_id, key_id_len);
 	id[subject_len + 2 + key_id_len] = 0;

 	pr_debug("Look up: \"%s\"\n", id);

 	key = keyring_search(make_key_ref(keyring, 1),
 			     &key_type_asymmetric, id);
 	if (IS_ERR(key))
 		pr_debug("Request for key '%s' err %ld\n", id, PTR_ERR(key));
 	kfree(id);

 	if (IS_ERR(key)) {
 		switch (PTR_ERR(key)) {
 			/* Hide some search errors */
 		case -EACCES:
 		case -ENOTDIR:
 		case -EAGAIN:
 			return ERR_PTR(-ENOKEY);
 		default:
 			return ERR_CAST(key);
 		}
 	}

 	pr_devel("<==%s() = 0 [%x]\n", __func__,
 		 key_serial(key_ref_to_ptr(key)));
 	return key_ref_to_ptr(key);
 }
 EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);

 /*
  * Set up the signature parameters in an X.509 certificate.  This involves
  * digesting the signed data and extracting the signature.
  */
 int x509_get_sig_params(struct x509_certificate *cert)
 {
 	struct crypto_shash *tfm;
 	struct shash_desc *desc;
 	size_t digest_size, desc_size;
 	void *digest;
 	int ret;

 	pr_devel("==>%s()\n", __func__);

 	if (cert->sig.rsa.s)
 		return 0;

 	cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
 	if (!cert->sig.rsa.s)
 		return -ENOMEM;
 	cert->sig.nr_mpi = 1;

 	/* 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[cert->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);
 	digest_size = crypto_shash_digestsize(tfm);

 	/* We allocate the hash operational data storage on the end of the
 	 * digest storage space.
 	 */
 	ret = -ENOMEM;
 	digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
 	if (!digest)
 		goto error;

 	cert->sig.digest = digest;
 	cert->sig.digest_size = digest_size;

 	desc = digest + digest_size;
 	desc->tfm = tfm;
 	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

 	ret = crypto_shash_init(desc);
 	if (ret < 0)
 		goto error;
 	might_sleep();
 	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
 error:
 	crypto_free_shash(tfm);
 	pr_devel("<==%s() = %d\n", __func__, ret);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(x509_get_sig_params);

 /*
  * Check the signature on a certificate using the provided public key
  */
 int x509_check_signature(const struct public_key *pub,
 			 struct x509_certificate *cert)
 {
 	int ret;

 	pr_devel("==>%s()\n", __func__);

 	ret = x509_get_sig_params(cert);
 	if (ret < 0)
 		return ret;

 	ret = public_key_verify_signature(pub, &cert->sig);
 	pr_debug("Cert Verification: %d\n", ret);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(x509_check_signature);

 /*
  * Check the new certificate against the ones in the trust keyring.  If one of
  * those is the signing key and validates the new certificate, then mark the
  * new certificate as being trusted.
  *
  * Return 0 if the new certificate was successfully validated, 1 if we couldn't
  * find a matching parent certificate in the trusted list and an error if there
  * is a matching certificate but the signature check fails.
  */
 static int x509_validate_trust(struct x509_certificate *cert,
 			       struct key *trust_keyring)
 {
 	struct key *key;
 	int ret = 1;

 	if (!trust_keyring)
 		return -EOPNOTSUPP;

 	if (ca_keyid && !asymmetric_keyid_match(cert->authority, ca_keyid))
 		return -EPERM;

 	key = x509_request_asymmetric_key(trust_keyring,
 					  cert->issuer, cert->authority);
 	if (!IS_ERR(key))  {
 		if (!use_builtin_keys
 		    || test_bit(KEY_FLAG_BUILTIN, &key->flags))
 			ret = x509_check_signature(key->payload.data, cert);
 		key_put(key);
 	}
 	return ret;
 }

 /*
  * Attempt to parse a data blob for a key as an X509 certificate.
  */
 static int x509_key_preparse(struct key_preparsed_payload *prep)
 {
 	struct x509_certificate *cert;
 	size_t srlen, sulen;
 	char *desc = NULL;
 	int ret;

 	cert = x509_cert_parse(prep->data, prep->datalen);
 	if (IS_ERR(cert))
 		return PTR_ERR(cert);

 	pr_devel("Cert Issuer: %s\n", cert->issuer);
 	pr_devel("Cert Subject: %s\n", cert->subject);

 	if (cert->pub->pkey_algo >= PKEY_ALGO__LAST ||
 	    cert->sig.pkey_algo >= PKEY_ALGO__LAST ||
 	    cert->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
 	    !pkey_algo[cert->pub->pkey_algo] ||
 	    !pkey_algo[cert->sig.pkey_algo] ||
 	    !hash_algo_name[cert->sig.pkey_hash_algo]) {
 		ret = -ENOPKG;
 		goto error_free_cert;
 	}

 	pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
 	pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
 		 cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
 		 cert->valid_from.tm_mday, cert->valid_from.tm_hour,
 		 cert->valid_from.tm_min,  cert->valid_from.tm_sec);
 	pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
 		 cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
 		 cert->valid_to.tm_mday, cert->valid_to.tm_hour,
 		 cert->valid_to.tm_min,  cert->valid_to.tm_sec);
 	pr_devel("Cert Signature: %s + %s\n",
 		 pkey_algo_name[cert->sig.pkey_algo],
 		 hash_algo_name[cert->sig.pkey_hash_algo]);

 	if (!cert->fingerprint) {
 		pr_warn("Cert for '%s' must have a SubjKeyId extension\n",
 			cert->subject);
 		ret = -EKEYREJECTED;
 		goto error_free_cert;
 	}

 	cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
 	cert->pub->id_type = PKEY_ID_X509;

 	/* Check the signature on the key if it appears to be self-signed */
 	if (!cert->authority ||
 	    strcmp(cert->fingerprint, cert->authority) == 0) {
 		ret = x509_check_signature(cert->pub, cert); /* self-signed */
 		if (ret < 0)
 			goto error_free_cert;
 	} else if (!prep->trusted) {
 		ret = x509_validate_trust(cert, get_system_trusted_keyring());
 		if (!ret)
 			prep->trusted = 1;
 	}

 	/* Propose a description */
 	sulen = strlen(cert->subject);
 	srlen = strlen(cert->fingerprint);
 	ret = -ENOMEM;
 	desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
 	if (!desc)
 		goto error_free_cert;
 	memcpy(desc, cert->subject, sulen);
 	desc[sulen] = ':';
 	desc[sulen + 1] = ' ';
 	memcpy(desc + sulen + 2, cert->fingerprint, srlen);
 	desc[sulen + 2 + srlen] = 0;

 	/* We're pinning the module by being linked against it */
 	__module_get(public_key_subtype.owner);
 	prep->type_data[0] = &public_key_subtype;
 	prep->type_data[1] = cert->fingerprint;
 	prep->payload[0] = cert->pub;
 	prep->description = desc;
 	prep->quotalen = 100;

 	/* We've finished with the certificate */
 	cert->pub = NULL;
 	cert->fingerprint = NULL;
 	desc = NULL;
 	ret = 0;

 error_free_cert:
 	x509_free_certificate(cert);
 	return ret;
 }

 static struct asymmetric_key_parser x509_key_parser = {
 	.owner	= THIS_MODULE,
 	.name	= "x509",
 	.parse	= x509_key_preparse,
 };

 /*
  * Module stuff
  */
 static int __init x509_key_init(void)
 {
 	return register_asymmetric_key_parser(&x509_key_parser);
 }

 static void __exit x509_key_exit(void)
 {
 	unregister_asymmetric_key_parser(&x509_key_parser);
 }

 module_init(x509_key_init);
 module_exit(x509_key_exit);

 MODULE_DESCRIPTION("X.509 certificate parser");
 MODULE_LICENSE("GPL");
	/* Instantiate a public key crypto key from an X.509 Certificate
	*
	* 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) "X.509: "fmt
	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/err.h>
	#include <linux/mpi.h>
	#include <linux/asn1_decoder.h>
	#include <keys/asymmetric-subtype.h>
	#include <keys/asymmetric-parser.h>
	#include <keys/system_keyring.h>
	#include <crypto/hash.h>
	#include "asymmetric_keys.h"
	#include "public_key.h"
	#include "x509_parser.h"

	static bool use_builtin_keys;
	static char *ca_keyid;

	#ifndef MODULE
	static int __init ca_keys_setup(char *str)
	{
	if (!str) /* default system keyring */
	return 1;

	if (strncmp(str, "id:", 3) == 0)
	ca_keyid = str; /* owner key 'id:xxxxxx' */
	else if (strcmp(str, "builtin") == 0)
	use_builtin_keys = true;

	return 1;
	}
	__setup("ca_keys=", ca_keys_setup);
	#endif

	/**
	* x509_request_asymmetric_key - Request a key by X.509 certificate params.
	* @keyring: The keys to search.
	* @subject: The name of the subject to whom the key belongs.
	* @key_id: The subject key ID as a hex string.
	*
	* Find a key in the given keyring by subject name and key ID. These might,
	* for instance, be the issuer name and the authority key ID of an X.509
	* certificate that needs to be verified.
	*/
	struct key x509_request_asymmetric_key(struct key keyring,
	const char *subject,
	const char *key_id)
	{
	key_ref_t key;
	size_t subject_len = strlen(subject), key_id_len = strlen(key_id);
	char *id;

	/* Construct an identifier "<subjname>:<keyid>". */
	id = kmalloc(subject_len + 2 + key_id_len + 1, GFP_KERNEL);
	if (!id)
	return ERR_PTR(-ENOMEM);

	memcpy(id, subject, subject_len);
	id[subject_len + 0] = ':';
	id[subject_len + 1] = ' ';
	memcpy(id + subject_len + 2, key_id, key_id_len);
	id[subject_len + 2 + key_id_len] = 0;

	pr_debug("Look up: \"%s\"\n", id);

	key = keyring_search(make_key_ref(keyring, 1),
	&key_type_asymmetric, id);
	if (IS_ERR(key))
	pr_debug("Request for key '%s' err %ld\n", id, PTR_ERR(key));
	kfree(id);

	if (IS_ERR(key)) {
	switch (PTR_ERR(key)) {
	/* Hide some search errors */
	case -EACCES:
	case -ENOTDIR:
	case -EAGAIN:
	return ERR_PTR(-ENOKEY);
	default:
	return ERR_CAST(key);
	}
	}

	pr_devel("<==%s() = 0 [%x]\n", __func__,
	key_serial(key_ref_to_ptr(key)));
	return key_ref_to_ptr(key);
	}
	EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);

	/*
	* Set up the signature parameters in an X.509 certificate. This involves
	* digesting the signed data and extracting the signature.
	*/
	int x509_get_sig_params(struct x509_certificate *cert)
	{
	struct crypto_shash *tfm;
	struct shash_desc *desc;
	size_t digest_size, desc_size;
	void *digest;
	int ret;

	pr_devel("==>%s()\n", __func__);

	if (cert->sig.rsa.s)
	return 0;

	cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
	if (!cert->sig.rsa.s)
	return -ENOMEM;
	cert->sig.nr_mpi = 1;

	/* 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[cert->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);
	digest_size = crypto_shash_digestsize(tfm);

	/* We allocate the hash operational data storage on the end of the
	* digest storage space.
	*/
	ret = -ENOMEM;
	digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
	if (!digest)
	goto error;

	cert->sig.digest = digest;
	cert->sig.digest_size = digest_size;

	desc = digest + digest_size;
	desc->tfm = tfm;
	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

	ret = crypto_shash_init(desc);
	if (ret < 0)
	goto error;
	might_sleep();
	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
	error:
	crypto_free_shash(tfm);
	pr_devel("<==%s() = %d\n", __func__, ret);
	return ret;
	}
	EXPORT_SYMBOL_GPL(x509_get_sig_params);

	/*
	* Check the signature on a certificate using the provided public key
	*/
	int x509_check_signature(const struct public_key *pub,
	struct x509_certificate *cert)
	{
	int ret;

	pr_devel("==>%s()\n", __func__);

	ret = x509_get_sig_params(cert);
	if (ret < 0)
	return ret;

	ret = public_key_verify_signature(pub, &cert->sig);
	pr_debug("Cert Verification: %d\n", ret);
	return ret;
	}
	EXPORT_SYMBOL_GPL(x509_check_signature);

	/*
	* Check the new certificate against the ones in the trust keyring. If one of
	* those is the signing key and validates the new certificate, then mark the
	* new certificate as being trusted.
	*
	* Return 0 if the new certificate was successfully validated, 1 if we couldn't
	* find a matching parent certificate in the trusted list and an error if there
	* is a matching certificate but the signature check fails.
	*/
	static int x509_validate_trust(struct x509_certificate *cert,
	struct key *trust_keyring)
	{
	struct key *key;
	int ret = 1;

	if (!trust_keyring)
	return -EOPNOTSUPP;

	if (ca_keyid && !asymmetric_keyid_match(cert->authority, ca_keyid))
	return -EPERM;

	key = x509_request_asymmetric_key(trust_keyring,
	cert->issuer, cert->authority);
	if (!IS_ERR(key)) {
	if (!use_builtin_keys
	\|\| test_bit(KEY_FLAG_BUILTIN, &key->flags))
	ret = x509_check_signature(key->payload.data, cert);
	key_put(key);
	}
	return ret;
	}

	/*
	* Attempt to parse a data blob for a key as an X509 certificate.
	*/
	static int x509_key_preparse(struct key_preparsed_payload *prep)
	{
	struct x509_certificate *cert;
	size_t srlen, sulen;
	char *desc = NULL;
	int ret;

	cert = x509_cert_parse(prep->data, prep->datalen);
	if (IS_ERR(cert))
	return PTR_ERR(cert);

	pr_devel("Cert Issuer: %s\n", cert->issuer);
	pr_devel("Cert Subject: %s\n", cert->subject);

	if (cert->pub->pkey_algo >= PKEY_ALGO__LAST \|\|
	cert->sig.pkey_algo >= PKEY_ALGO__LAST \|\|
	cert->sig.pkey_hash_algo >= PKEY_HASH__LAST \|\|
	!pkey_algo[cert->pub->pkey_algo] \|\|
	!pkey_algo[cert->sig.pkey_algo] \|\|
	!hash_algo_name[cert->sig.pkey_hash_algo]) {
	ret = -ENOPKG;
	goto error_free_cert;
	}

	pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
	pr_devel("Cert Valid From: %04ld-%02d-%02d %02d:%02d:%02d\n",
	cert->valid_from.tm_year + 1900, cert->valid_from.tm_mon + 1,
	cert->valid_from.tm_mday, cert->valid_from.tm_hour,
	cert->valid_from.tm_min, cert->valid_from.tm_sec);
	pr_devel("Cert Valid To: %04ld-%02d-%02d %02d:%02d:%02d\n",
	cert->valid_to.tm_year + 1900, cert->valid_to.tm_mon + 1,
	cert->valid_to.tm_mday, cert->valid_to.tm_hour,
	cert->valid_to.tm_min, cert->valid_to.tm_sec);
	pr_devel("Cert Signature: %s + %s\n",
	pkey_algo_name[cert->sig.pkey_algo],
	hash_algo_name[cert->sig.pkey_hash_algo]);

	if (!cert->fingerprint) {
	pr_warn("Cert for '%s' must have a SubjKeyId extension\n",
	cert->subject);
	ret = -EKEYREJECTED;
	goto error_free_cert;
	}

	cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
	cert->pub->id_type = PKEY_ID_X509;

	/* Check the signature on the key if it appears to be self-signed */
	if (!cert->authority \|\|
	strcmp(cert->fingerprint, cert->authority) == 0) {
	ret = x509_check_signature(cert->pub, cert); /* self-signed */
	if (ret < 0)
	goto error_free_cert;
	} else if (!prep->trusted) {
	ret = x509_validate_trust(cert, get_system_trusted_keyring());
	if (!ret)
	prep->trusted = 1;
	}

	/* Propose a description */
	sulen = strlen(cert->subject);
	srlen = strlen(cert->fingerprint);
	ret = -ENOMEM;
	desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
	if (!desc)
	goto error_free_cert;
	memcpy(desc, cert->subject, sulen);
	desc[sulen] = ':';
	desc[sulen + 1] = ' ';
	memcpy(desc + sulen + 2, cert->fingerprint, srlen);
	desc[sulen + 2 + srlen] = 0;

	/* We're pinning the module by being linked against it */
	__module_get(public_key_subtype.owner);
	prep->type_data[0] = &public_key_subtype;
	prep->type_data[1] = cert->fingerprint;
	prep->payload[0] = cert->pub;
	prep->description = desc;
	prep->quotalen = 100;

	/* We've finished with the certificate */
	cert->pub = NULL;
	cert->fingerprint = NULL;
	desc = NULL;
	ret = 0;

	error_free_cert:
	x509_free_certificate(cert);
	return ret;
	}

	static struct asymmetric_key_parser x509_key_parser = {
	.owner = THIS_MODULE,
	.name = "x509",
	.parse = x509_key_preparse,
	};

	/*
	* Module stuff
	*/
	static int __init x509_key_init(void)
	{
	return register_asymmetric_key_parser(&x509_key_parser);
	}

	static void __exit x509_key_exit(void)
	{
	unregister_asymmetric_key_parser(&x509_key_parser);
	}

	module_init(x509_key_init);
	module_exit(x509_key_exit);

	MODULE_DESCRIPTION("X.509 certificate parser");
	MODULE_LICENSE("GPL");