[PATCH v3 05/13] diglim: Parser

[Roberto Sassu]

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@xxxxxxxxxx>
---
 .../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 83342ec12f74..626af0d245ef 100644
--- a/Documentation/security/diglim/implementation.rst
+++ b/Documentation/security/diglim/implementation.rst
@@ -182,3 +182,38 @@ 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 06c6ba0b3f25..f5959936d490 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5515,6 +5515,7 @@ 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@xxxxxxxxxxxx>
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 75359f9cd3dd..afdb0affdc5e 100644
--- a/security/integrity/diglim/diglim.h
+++ b/security/integrity/diglim/diglim.h
@@ -218,4 +218,7 @@ 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..435d231028c7
--- /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@xxxxxxxxxx>
+ *
+ * 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("insufficient 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