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

Mauro Carvalho Chehab
2021-07-28T12:36:08Z

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;
> +}