Re: [RFC][PATCH v2 05/12] diglim: Parser

Em Mon, 26 Jul 2021 18:36:53 +0200 Roberto Sassu roberto.sassu@huawei.com escreveu:

Introduce the necessary functions to parse a digest list and to execute the requested operation.

The main function is digest_list_parse(), which coordinates the various steps required to add or delete a digest list, and has the logic to roll back when one of the steps fails.

A more detailed description about the steps can be found in Documentation/security/diglim/implementation.rst

LGTM.

Signed-off-by: Roberto Sassu roberto.sassu@huawei.com

.../security/diglim/implementation.rst | 35 +++ MAINTAINERS | 1 + security/integrity/diglim/Makefile | 2 +- security/integrity/diglim/diglim.h | 3 + security/integrity/diglim/parser.c | 274 ++++++++++++++++++ 5 files changed, 314 insertions(+), 1 deletion(-) create mode 100644 security/integrity/diglim/parser.c

diff --git a/Documentation/security/diglim/implementation.rst b/Documentation/security/diglim/implementation.rst index 54af23b2f5f1..9d679567a037 100644 --- a/Documentation/security/diglim/implementation.rst +++ b/Documentation/security/diglim/implementation.rst @@ -209,3 +209,38 @@ This section introduces the methods requires to manage the three objects defined. .. kernel-doc:: security/integrity/diglim/methods.c

+Parser +------

+This section introduces the necessary functions to parse a digest list and +to execute the requested operation.

+.. kernel-doc:: security/integrity/diglim/parser.c

+The main function is digest_list_parse(), which coordinates the various +steps required to add or delete a digest list, and has the logic to roll +back when one of the steps fails.

+#. Calls digest_list_validate() to validate the passed buffer containing

• the digest list to ensure that the format is correct.

+#. Calls get_digest_list() to create a new digest_list_item for the add

• operation, or to retrieve the existing one for the delete operation.
• get_digest_list() refuses to add digest lists that were previously
• added and to delete digest lists that weren't previously added. Also,
• get_digest_list() refuses to delete digest lists if there are actions
• done at addition time that are not currently being performed (it would
• guarantee that also deletion is notified to remote verifiers).

+#. Calls _digest_list_parse() which takes the created/retrieved

• struct digest_list_item and adds or delete the digests included in the
• digest list.

+#. If an error occurred, performs a rollback to the previous state, by

• calling _digest_list_parse() with the opposite operation and the buffer
• size at the time the error occurred.

+#. digest_list_parse() deletes the struct digest_list_item on unsuccessful

• add or successful delete.

diff --git a/MAINTAINERS b/MAINTAINERS index 9e085a36654a..77c3613c600a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5465,6 +5465,7 @@ F: include/linux/diglim.h F: include/uapi/linux/diglim.h F: security/integrity/diglim/diglim.h F: security/integrity/diglim/methods.c +F: security/integrity/diglim/parser.c DIOLAN U2C-12 I2C DRIVER M: Guenter Roeck linux@roeck-us.net diff --git a/security/integrity/diglim/Makefile b/security/integrity/diglim/Makefile index b761ed8cfb3e..34e4e154fff3 100644 --- a/security/integrity/diglim/Makefile +++ b/security/integrity/diglim/Makefile @@ -5,4 +5,4 @@ obj-$(CONFIG_DIGLIM) += diglim.o -diglim-y := methods.o +diglim-y := methods.o parser.o diff --git a/security/integrity/diglim/diglim.h b/security/integrity/diglim/diglim.h index 25851e7d4906..3adc218a0325 100644 --- a/security/integrity/diglim/diglim.h +++ b/security/integrity/diglim/diglim.h @@ -149,4 +149,7 @@ struct digest_item *digest_list_add(u8 *digest, enum hash_algo algo, const char *label); void digest_list_del(u8 *digest, enum hash_algo algo, u8 actions, struct digest_list_item *digest_list);

+int digest_list_parse(loff_t size, void *buf, enum ops op, u8 actions,

•       u8 *digest, enum hash_algo algo, const char *label);
  

#endif /*__DIGLIM_INTERNAL_H*/ diff --git a/security/integrity/diglim/parser.c b/security/integrity/diglim/parser.c new file mode 100644 index 000000000000..89a48945b460 --- /dev/null +++ b/security/integrity/diglim/parser.c @@ -0,0 +1,274 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Copyright (C) 2005,2006,2007,2008 IBM Corporation
• • Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
• • Author: Roberto Sassu roberto.sassu@huawei.com
• • Functions to parse digest lists.
• */

+#include <linux/vmalloc.h> +#include <linux/module.h>

+#include "diglim.h" +#include "../integrity.h"

+/**

• • digest_list_validate - validate format of digest list
• • @size: buffer size
• • @buf: buffer containing the digest list
• • This function validates the format of the passed digest list.
• • Return: 0 if the digest list was successfully validated, -EINVAL otherwise.
• */

+static int digest_list_validate(loff_t size, void *buf) +{

• void *bufp = buf, *bufendp = buf + size;
• struct compact_list_hdr *hdr;
• size_t digest_len;
• while (bufp < bufendp) {

• if (bufp + sizeof(*hdr) > bufendp) {
  

• 	pr_err("invalid data\n");
  

• 	return -EINVAL;
  

• }
  

• hdr = bufp;
  

• if (hdr->version != 1) {
  

• 	pr_err("unsupported version\n");
  

• 	return -EINVAL;
  

• }
  

• if (hdr->_reserved != 0) {
  

• 	pr_err("unexpected value for _reserved field\n");
  

• 	return -EINVAL;
  

• }
  

• hdr->type = le16_to_cpu(hdr->type);
  

• hdr->modifiers = le16_to_cpu(hdr->modifiers);
  

• hdr->algo = le16_to_cpu(hdr->algo);
  

• hdr->count = le32_to_cpu(hdr->count);
  

• hdr->datalen = le32_to_cpu(hdr->datalen);
  

• if (hdr->algo >= HASH_ALGO__LAST) {
  

• 	pr_err("invalid hash algorithm\n");
  

• 	return -EINVAL;
  

• }
  

• digest_len = hash_digest_size[hdr->algo];
  

• if (hdr->type >= COMPACT__LAST ||
  

•     hdr->type == COMPACT_DIGEST_LIST) {
  

• 	pr_err("invalid type %d\n", hdr->type);
  

• 	return -EINVAL;
  

• }
  

• bufp += sizeof(*hdr);
  

• if (hdr->datalen != hdr->count * digest_len ||
  

•     bufp + hdr->datalen > bufendp) {
  

• 	pr_err("invalid data\n");
  

• 	return -EINVAL;
  

• }
  

• bufp += hdr->count * digest_len;
  

• }
• return 0;

+}

+/**

• • _digest_list_parse - parse digest list and add/delete digests
• • @size: buffer size
• • @buf: buffer containing the digest list
• • @op: operation to be performed
• • @digest_list: digest list digests being added/deleted belong to
• • This function parses the digest list and adds or delete the digests in the
• • found digest blocks.
• • Return: the buffer size if all digests were successfully added or deleted,
• • the size of the already parsed buffer on error.
• */

+static int _digest_list_parse(loff_t size, void *buf, enum ops op,

• 	      struct digest_list_item *digest_list)
  

+{

• void *bufp = buf, *bufendp = buf + size;
• struct compact_list_hdr *hdr;
• struct digest_item *d = ERR_PTR(-EINVAL);
• size_t digest_len;
• int i;
• while (bufp < bufendp) {

• if (bufp + sizeof(*hdr) > bufendp)
  

• 	break;
  

• hdr = bufp;
  

• bufp += sizeof(*hdr);
  

• digest_len = hash_digest_size[hdr->algo];
  

• for (i = 0; i < hdr->count && bufp + digest_len <= bufendp;
  

•      i++, bufp += digest_len) {
  

• 	switch (op) {
  

• 	case DIGEST_LIST_ADD:
  

• 		d = digest_add(bufp, hdr->algo, hdr->type,
  

• 			       digest_list, bufp - buf,
  

• 			       (void *)hdr - buf);
  

• 		if (IS_ERR(d)) {
  

• 			pr_err(
  

• 			    "failed to add a digest from %s\n",
  

• 			    digest_list->label);
  

• 			goto out;
  

• 		}
  

• 		break;
  

• 	case DIGEST_LIST_DEL:
  

• 		digest_del(bufp, hdr->algo, hdr->type,
  

• 			   digest_list, bufp - buf,
  

• 			   (void *)hdr - buf);
  

• 		break;
  

• 	default:
  

• 		break;
  

• 	}
  

• }
  

• }

+out:

• return bufp - buf;

+}

+/**

• • get_digest_list - get the digest list extracted digests will be associated to
• • @size: buffer size
• • @buf: buffer containing the digest list
• • @op: digest list operation
• • @actions: actions performed on the digest list being processed
• • @digest: digest of the digest list
• • @algo: digest algorithm
• • @label: label to identify the digest list (e.g. file name)
• • This function retrieves the digest list item for the passed digest and
• • algorithm. If it is not found at addition time, this function creates a new
• • one.
• • This function prevents the imbalance of digests (references left after
• • delete) by ensuring that only digest lists that were previously added can be
• • deleted.
• • This function also ensures that the actions done at the time of addition are
• • also performed at the time of deletion (it would guarantee that also deletion
• • is notified to remote verifiers).
• • Return: the retrieved/created digest list item on success, an error pointer
• • otherwise.
• */

+static struct digest_list_item *get_digest_list(loff_t size, void *buf,

• 				enum ops op, u8 actions,
  

• 				u8 *digest, enum hash_algo algo,
  

• 				const char *label)
  

+{

• struct digest_item *d;
• struct digest_list_item *digest_list;
• int digest_len = hash_digest_size[algo];
• switch (op) {
• case DIGEST_LIST_ADD:

• /* Add digest list to be associated to each digest. */
  

• d = digest_list_add(digest, algo, size, buf, actions, label);
  

• if (IS_ERR(d))
  

• 	return (void *)d;
  

• digest_list = list_first_entry(&d->refs,
  

• 		struct digest_list_item_ref, list)->digest_list;
  

• break;
  

• case DIGEST_LIST_DEL:

• /* Lookup digest list to delete the references. */
  

• d = __digest_lookup(digest, algo, COMPACT_DIGEST_LIST, NULL,
  

• 		    NULL);
  

• if (!d) {
  

• 	print_hex_dump(KERN_ERR,
  

• 		       "digest list digest not found: ",
  

• 		       DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 		       digest_len, true);
  

• 	return ERR_PTR(-ENOENT);
  

• }
  

• digest_list = list_first_entry(&d->refs,
  

• 		struct digest_list_item_ref, list)->digest_list;
  

• /*
  

•  * Reject deletion if there are actions done at addition time
  

•  * that are currently not being performed.
  

•  */
  

• if ((digest_list->actions & actions) != digest_list->actions) {
  

• 	pr_err("missing actions, add: %d, del: %d\n",
  

• 	       digest_list->actions, actions);
  

• 	return ERR_PTR(-EPERM);
  

• }
  

• break;
  

• default:

• return ERR_PTR(-EINVAL);
  

• }
• return digest_list;

+}

+/**

• • digest_list_parse - parse a digest list
• • @size: buffer size
• • @buf: buffer containing the digest list
• • @op: digest list operation
• • @actions: actions performed on the digest list being processed
• • @digest: digest of the digest list
• • @algo: digest algorithm
• • @label: label to identify the digest list (e.g. file name)
• • This function parses the passed digest list and executed the requested
• • operation. If the operation cannot be successfully executed, this function
• • performs a rollback to the previous state.
• • Return: the buffer size on success, a negative value otherwise.
• */

+int digest_list_parse(loff_t size, void *buf, enum ops op, u8 actions,

•       u8 *digest, enum hash_algo algo, const char *label)
  

+{

• struct digest_list_item *digest_list;
• enum ops rollback_op = (op == DIGEST_LIST_ADD) ?

• 	       DIGEST_LIST_DEL : DIGEST_LIST_ADD;
  

• int ret, rollback_size;
• ret = digest_list_validate(size, buf);
• if (ret < 0)

• return ret;
  

• digest_list = get_digest_list(size, buf, op, actions, digest, algo,

• 		      label);
  

• if (IS_ERR(digest_list))

• return PTR_ERR(digest_list);
  

• ret = _digest_list_parse(size, buf, op, digest_list);
• if (ret < 0)

• goto out;
  

• if (ret != size) {

• rollback_size = ret;
  

• ret = _digest_list_parse(rollback_size, buf, rollback_op,
  

• 			 digest_list);
  

• if (ret != rollback_size)
  

• 	pr_err("rollback failed\n");
  

• ret = -EINVAL;
  

• }

+out:

• /* Delete digest list on unsuccessful add or successful delete. */
• if ((op == DIGEST_LIST_ADD && ret < 0) ||

•    (op == DIGEST_LIST_DEL && ret == size))
  

• digest_list_del(digest, algo, actions, digest_list);
  

• return ret;

+}