RE: [RFC][PATCH v2 03/12] diglim: Objects

Roberto Sassu
2021-07-28T11:47:25Z

> From: Mauro Carvalho Chehab [mailto:mchehab+huawei@kernel.org]
> Sent: Wednesday, July 28, 2021 1:39 PM
> Em Mon, 26 Jul 2021 18:36:51 +0200
> Roberto Sassu <roberto.sassu@huawei.com> escreveu:
>
> > Define the objects to manage digest lists:
> >
> > - digest_list_item: a digest list loaded into the kernel;
> > - digest_list_item_ref: a reference to a digest list;
> > - digest_item: a digest of a digest list.
> >
> > Also define some helpers for the objects. More information can be found in
> > Documentation/security/diglim/implementation.rst.
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > ---
> > .../security/diglim/implementation.rst | 105 ++++++++++++++
> > MAINTAINERS | 1 +
> > security/integrity/diglim/diglim.h | 134 ++++++++++++++++++
> > 3 files changed, 240 insertions(+)
> > create mode 100644 security/integrity/diglim/diglim.h
> >
> > diff --git a/Documentation/security/diglim/implementation.rst
> b/Documentation/security/diglim/implementation.rst
> > index 59a180b3bb3f..6002049612a1 100644
> > --- a/Documentation/security/diglim/implementation.rst
> > +++ b/Documentation/security/diglim/implementation.rst
> > @@ -95,3 +95,108 @@ with digest lists:
> >
> > - ``DIGEST_LIST_ADD``: the digest list is being added;
> > - ``DIGEST_LIST_DEL``: the digest list is being deleted.
> > +
> > +
> > +Objects
> > +-------
> > +
> > +This section defines the objects to manage digest lists.
> > +
> > +.. kernel-doc:: security/integrity/diglim/diglim.h
> > +
> > +They are represented in the following class diagram:
> > +
> > +::
> > +
> > + digest_offset,
> > + hdr_offset---------------+
> > + |
> > + |
> > + +------------------+ | +----------------------+
> > + | digest_list_item |--- N:1 ---| digest_list_item_ref |
> > + +------------------+ +----------------------+
> > + |
> > + 1:N
> > + |
> > + +-------------+
> > + | digest_item |
> > + +-------------+
> > +
> > +A ``digest_list_item`` is associated to one or multiple
> > +``digest_list_item_ref``, one for each digest it contains. However,
> > +a ``digest_list_item_ref`` is associated to only one ``digest_list_item``,
> > +as it represents a single location within a specific digest list.
> > +
> > +Given that a ``digest_list_item_ref`` represents a single location, it is
> > +associated to only one ``digest_item``. However, a ``digest_item`` can have
> > +multiple references (as it might appears multiple times within the same
> > +digest list or in different digest lists, if it is duplicated).
> > +
> > +All digest list references are stored for a given digest, so that a query
> > +result can include the OR of the modifiers and actions of each referenced
> > +digest list.
> > +
> > +The relationship between the described objects can be graphically
> > +represented as:
> > +
> > +::
>
> Just merge "::" at the previous line (everywhere).

Ok.

> > +
> > + Hash table +-------------+ +-------------+
> > + PARSER +-----+ | digest_item | | digest_item |
> > + FILE | key |-->| |-->...-->| |
> > + METADATA +-----+ |ref0|...|refN| |ref0|...|refN|
> > + +-------------+ +-------------+
> > + ref0: | | refN:
> > + digest_offset | +-----------------------------+ digest_offset
> > + hdr_offset | | hdr_offset
> > + | |
> > + V V
> > + +--------------------+
> > + | digest_list_item |
> > + | |
> > + | size, buf, actions |
> > + +--------------------+
> > + ^
> > + |
> > + Hash table +-------------+ +-------------+
> > + DIGEST_LIST +-----+ |ref0 | |ref0 |
> > + | key |-->| |-->...-->| |
> > + +-----+ | digest_item | | digest_item |
> > + +-------------+ +-------------+
> > +
> > +The reference for the digest of the digest list differs from the references
> > +for the other digest types. ``digest_offset`` and ``hdr_offset`` are set to
> > +zero, so that the digest of the digest list is retrieved from the
> > +``digest_list_item`` structure directly (see ``get_digest()`` below).
> > +
> > +Finally, this section defines useful helpers to access a digest or the
> > +header the digest belongs to. For example:
> > +
> > +::
> > +
> > + static inline struct compact_list_hdr *get_hdr(
> > + struct digest_list_item *digest_list,
> > + loff_t hdr_offset)
>
> I would write this to avoid ending a line with an open parenthesis. You could,
> for instance, write it as:
>
> static inline struct compact_list_hdr *
> get_hdr(struct digest_list_item *digest_list,
> off_t hdr_offset)
>
> if you also want to avoid to have a line bigger than 80 columns.

Ok.

> > + {
> > + return (struct compact_list_hdr *)(digest_list->buf + hdr_offset);
> > + }
> > +
> > +the header can be obtained by summing the address of the digest list buffer
> > +in the ``digest_list_item`` structure with ``hdr_offset``.
> > +
> > +Similarly:
> > +
> > +::
> > +
> > + static inline u8 *get_digest(struct digest_list_item *digest_list,
> > + loff_t digest_offset, loff_t hdr_offset)
> > + {
> > + /* Digest list digest is stored in a different place. */
> > + if (!digest_offset)
> > + return digest_list->digest;
> > + return digest_list->buf + digest_offset;
> > + }
> > +
> > +the digest can be obtained by summing the address of the digest list buffer
> > +with ``digest_offset`` (except for the digest lists, where the digest is
> > +stored in the ``digest`` field of the ``digest_list_item`` structure).
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index f61f5239468a..f7592d41367d 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -5462,6 +5462,7 @@ F:
> Documentation/security/diglim/implementation.rst
> > F: Documentation/security/diglim/index.rst
> > F: Documentation/security/diglim/introduction.rst
> > F: include/uapi/linux/diglim.h
> > +F: security/integrity/diglim/diglim.h
> >
> > DIOLAN U2C-12 I2C DRIVER
> > M: Guenter Roeck <linux@roeck-us.net>
> > diff --git a/security/integrity/diglim/diglim.h
> b/security/integrity/diglim/diglim.h
> > new file mode 100644
> > index 000000000000..578253d7e1d1
> > --- /dev/null
> > +++ b/security/integrity/diglim/diglim.h
> > @@ -0,0 +1,134 @@
> > +/* 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>
> > + *
> > + * Definitions only used inside DIGLIM.
> > + */
> > +
> > +#ifndef __DIGLIM_INTERNAL_H
> > +#define __DIGLIM_INTERNAL_H
> > +
> > +#include <linux/types.h>
> > +#include <linux/crypto.h>
> > +#include <linux/fs.h>
> > +#include <linux/security.h>
> > +#include <linux/hash.h>
> > +#include <linux/tpm.h>
> > +#include <linux/audit.h>
> > +#include <crypto/hash_info.h>
> > +#include <linux/hash_info.h>
> > +#include <uapi/linux/diglim.h>
> > +
> > +#define MAX_DIGEST_SIZE 64
> > +#define HASH_BITS 10
> > +#define DIGLIM_HTABLE_SIZE (1 << HASH_BITS)
> > +
> > +/**
> > + * struct digest_list_item - a digest list loaded into the kernel
> > + *
> > + * @size: size of the digest list buffer
> > + * @buf: digest list buffer
> > + * @digest: digest of the digest list
> > + * @label: label used to identify the digest list (e.g. file name)
> > + * @actions: actions performed on the digest list
> > + * @algo: digest algorithm
> > + */
> > +struct digest_list_item {
> > + loff_t size;
> > + u8 *buf;
> > + u8 digest[64];
> > + const char *label;
> > + u8 actions;
> > + enum hash_algo algo;
> > +};
> > +
> > +/**
> > + * struct digest_list_item_ref - a reference to a digest list
> > + *
> > + * @list: linked list pointers
> > + * @digest_list: pointer to struct digest_list_item
> > + * @digest_offset: offset of the digest in the referenced digest list
> > + * @hdr_offset: offset of the header the digest refers to in the digest list
> > + */
> > +struct digest_list_item_ref {
> > + struct list_head list;
> > + struct digest_list_item *digest_list;
> > + u32 digest_offset;
> > + u32 hdr_offset;
> > +};
> > +
> > +/**
> > + * struct digest_item - a digest of a digest list
> > + *
> > + * @hnext: pointers of the hash table
> > + * @refs: linked list of struct digest_list_item_ref
> > + */
> > +struct digest_item {
> > + struct hlist_node hnext;
> > + struct list_head refs;
> > +};
> > +
>
>
> > +struct h_table {
> > + unsigned long len;
> > + struct hlist_head queue[DIGLIM_HTABLE_SIZE];
> > +};
> > +
> > +static inline unsigned int hash_key(u8 *digest)
> > +{
> > + return (digest[0] | digest[1] << 8) % DIGLIM_HTABLE_SIZE;
> > +}
> > +
> > +static inline struct compact_list_hdr *get_hdr(
> > + struct digest_list_item *digest_list,
> > + loff_t hdr_offset)
>
> Same here with regards to open parenthesis.
>
> > +{
> > + return (struct compact_list_hdr *)(digest_list->buf + hdr_offset);
> > +}
> > +
> > +static inline enum hash_algo get_algo(struct digest_list_item *digest_list,
> > + loff_t digest_offset, loff_t hdr_offset)
> > +{
> > + /* Digest list digest algorithm is stored in a different place. */
> > + if (!digest_offset)
> > + return digest_list->algo;
> > +
> > + return get_hdr(digest_list, hdr_offset)->algo;
> > +}
> > +
> > +static inline u8 *get_digest(struct digest_list_item *digest_list,
> > + loff_t digest_offset, loff_t hdr_offset)
> > +{
> > + /* Digest list digest is stored in a different place. */
> > + if (!digest_offset)
> > + return digest_list->digest;
> > +
> > + return digest_list->buf + digest_offset;
> > +}
> > +
> > +static inline struct compact_list_hdr *get_hdr_ref(
> > + struct digest_list_item_ref *ref)
> > +{
> > + return get_hdr(ref->digest_list, ref->hdr_offset);
> > +}
> > +
> > +static inline enum hash_algo get_algo_ref(struct digest_list_item_ref *ref)
> > +{
> > + /* Digest list digest algorithm is stored in a different place. */
> > + if (!ref->digest_offset)
> > + return ref->digest_list->algo;
> > +
> > + return get_hdr_ref(ref)->algo;
> > +}
> > +
> > +static inline u8 *get_digest_ref(struct digest_list_item_ref *ref)
> > +{
> > + /* Digest list digest is stored in a different place. */
> > + if (!ref->digest_offset)
> > + return ref->digest_list->digest;
> > +
> > + return ref->digest_list->buf + ref->digest_offset;
> > +}
>
> I would also document the above static inline functions and
> struct h_table.

Ok.

Thanks

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli

> > +#endif /*__DIGLIM_INTERNAL_H*/
>
>
>
> Thanks,
> Mauro