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

Roberto Sassu
2021-07-26T16:41:35Z

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

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;
+}
--
2.25.1