Em Mon, 26 Jul 2021 18:36:49 +0200 Roberto Sassu roberto.sassu@huawei.com escreveu:

Add an overview of DIGLIM to Documentation/security/diglim/introduction.rst and the architecture to Documentation/security/diglim/architecture.rst

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

.../security/diglim/architecture.rst | 45 ++ Documentation/security/diglim/index.rst | 11 + .../security/diglim/introduction.rst | 631 ++++++++++++++++++ Documentation/security/index.rst | 1 + MAINTAINERS | 9 + 5 files changed, 697 insertions(+) create mode 100644 Documentation/security/diglim/architecture.rst create mode 100644 Documentation/security/diglim/index.rst create mode 100644 Documentation/security/diglim/introduction.rst

diff --git a/Documentation/security/diglim/architecture.rst b/Documentation/security/diglim/architecture.rst new file mode 100644 index 000000000000..a54fe2453715 --- /dev/null +++ b/Documentation/security/diglim/architecture.rst @@ -0,0 +1,45 @@ +.. SPDX-License-Identifier: GPL-2.0

+Architecture +============

+This section introduces the high level architecture of DIGLIM.

+::

• 5. add/delete from hash table and add refs to digest list

•    +---------------------------------------------+
  

•    |                            +-----+   +-------------+         +--+
  

•    |                            | key |-->| digest refs |-->...-->|  |
  

•    V                            +-----+   +-------------+         +--+
  

• +-------------+ +-----+ +-------------+
• | digest list | | key |-->| digest refs |
• | (compact) | +-----+ +-------------+
• +-------------+ +-----+ +-------------+

•    ^ 4. copy to                 | key |-->| digest refs |
  

•    |    kernel memory           +-----+   +-------------+ kernel space
  

• ---

•    ^                                          ^             user space
  

•    |<----------------+       3b. upload       |
  

• +-------------+ +------------+ | 6. query digest
• | digest list | | user space | 2b. convert
• | (compact) | | parser |
• +-------------+ +------------+
• 1a. upload ^ 1b. read

•                      |
  

•               +------------+
  

•               | RPM header |
  

•               +------------+
  

+As mentioned before, digest lists can be uploaded directly if they are in

"before"? This is at the beginning of this document ;-)

You should probably add a reference to introduction.rst here, like:

As mentioned at Documentation/security/diglim/introduction.rst, ...

+the compact format (step 1a) or can be uploaded indirectly by the user +space parser if they are in an alternative format (steps 1b-3b).

+During upload, the kernel makes a copy of the digest list to the kernel +memory (step 4), and creates the necessary structures to index the digests +(hash table and a linked list of digest list references to locate the +digests in the digest list) (step 5).

+Finally, digests can be searched from user space through a securityfs file +(step 6) or by the kernel itself.

This probably applies to Documentation/security as a hole, but the best is to split the documents on two separate parts: - the kAPI and internals; - the admin-guide part.

The audience for the admin-guide is distribution pagagers and syssadmins.

diff --git a/Documentation/security/diglim/index.rst b/Documentation/security/diglim/index.rst new file mode 100644 index 000000000000..0fc5ab019bc0 --- /dev/null +++ b/Documentation/security/diglim/index.rst @@ -0,0 +1,11 @@ +.. SPDX-License-Identifier: GPL-2.0

+====================================== +Digest Lists Integrity Module (DIGLIM) +======================================

+.. toctree::

• :maxdepth: 1
• introduction
• architecture

diff --git a/Documentation/security/diglim/introduction.rst b/Documentation/security/diglim/introduction.rst new file mode 100644 index 000000000000..d8d8b2a17222 --- /dev/null +++ b/Documentation/security/diglim/introduction.rst @@ -0,0 +1,631 @@ +.. SPDX-License-Identifier: GPL-2.0

+Introduction +============

+Digest Lists Integrity Module (DIGLIM) is a new component added to the +integrity subsystem in the kernel, primarily aiming to aid Integrity

I would replace:

"is a new component added to" -> "is a component of"

As this is the kind of text that tends to be outdated with time... Imagine someone reading this paragraph maybe 10 years in the future ;-)

+Measurement Architecture (IMA) in the process of checking the integrity of +file content and metadata. It accomplishes this task by storing reference +values coming from software vendors and by reporting whether or not the +digest of file content or metadata calculated by IMA (or EVM) is found +among those values. In this way, IMA can decide, depending on the result of +a query, if a measurement should be taken or access to the file should be +granted. The `Security Assumptions`_ section explains more in detail why +this component has been placed in the kernel.

+The main benefits of using IMA in conjunction with DIGLIM are the ability +to implement advanced remote attestation schemes based on the usage of a +TPM key for establishing a TLS secure channel [1][2], and to reduce the +burden on Linux distribution vendors to extend secure boot at OS level to +applications.

+DIGLIM does not have the complexity of feature-rich databases. In fact, its +main functionality comes from the hash table primitives already in the +kernel. It does not have an ad-hoc storage module, it just indexes data in +a fixed format (digest lists, a set of concatenated digests preceded by a +header), copied to kernel memory as they are. Lastly, it does not support +database-oriented languages such as SQL, but only accepts a digest and its +algorithm as a query.

+The only digest list format supported by DIGLIM is called ``compact``. +However, Linux distribution vendors don't have to generate new digest lists +in this format for the packages they release, as already available +information, such as RPM headers and DEB package metadata, can be already +used as a source for reference values (they already include file digests),

-ETOMANY_already

as "already" available... can be "already" ... "already" include...

I would simplify the above text removing such redundancy.

+with a user space parser taking care of the conversion to the compact +format.

+Although one might perceive that storing file or metadata digests for a +Linux distribution would significantly increase the memory usage, this does +not seem to be the case. As an anticipation of the evaluation done in the +`Preliminary Performance Evaluation`_ section, protecting binaries and +shared libraries of a minimal Fedora 33 installation requires 208K of +memory for the digest lists plus 556K for indexing.

+In exchange for a slightly increased memory usage, DIGLIM improves the +performance of the integrity subsystem. In the considered scenario, IMA +measurement and appraisal with digest lists requires respectively less than +one quarter and less than half the time, compared to the current solution.

I found this paragraph a little bit confusing to understand. Could you please improve the description?

I mean:

what improved by one quarter? what improved by "less than half of the time"?

+DIGLIM also keeps track of whether digest lists have been processed in some +way (e.g. measured or appraised by IMA). This is important for example for +remote attestation, so that remote verifiers understand what has been +uploaded to the kernel.

+DIGLIM behaves like a transactional database, i.e. it has the ability to +roll back to the beginning of the transaction if an error occurred during +the addition of a digest list (the deletion operation always succeeds).

I don't think it makes sense to compare it with a transactional database.

I would say, instead, something like:

The inserts on DIGLIM are atomic: if an error occurs during the addition of a digest list, it rolls back the entire insert operation.

+This capability has been tested with an ad-hoc fault injection mechanism +capable of simulating failures during the operations.

+Finally, DIGLIM exposes to user space, through securityfs, the digest lists +currently loaded, the number of digests added, a query interface and an +interface to set digest list labels.

+[1] LSS EU 2019

+- slides:

• https://static.sched.com/hosted_files/lsseu2019/bd/secure_attested_communica...

+- video: https://youtu.be/mffdQgkvDNY

+[2] FutureTPM EU project, final review meeting demo

+- slides:

• https://futuretpm.eu/images/07-3-FutureTPM-Final-Review-Slides-WP6-Device-Ma...

+- video: https://vimeo.com/528251864/4c1d55abcd

The above won't generate any cross-references with Sphinx.

For it correct syntax, see: https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html#cita...

+Binary Integrity +----------------

+Integrity is a fundamental security property in information systems.

+Integrity could be described as the condition in which a generic +component is just after it has been released by the entity that created it.

Sounds a weird description for me. (ISC)2 defines integrity on its glossary[1] as:

"Guarding against improper information modification or destruction and includes ensuring information non-repudiation and authenticity."

[1] https://www.isc2.org/Certifications/CISSP/CISSP-Student-Glossary

+One way to check whether a component is in this condition (called binary +integrity) is to calculate its digest and to compare it with a reference +value (i.e. the digest calculated in controlled conditions, when the +component is released).

+IMA, a software part of the integrity subsystem, can perform such +evaluation and execute different actions:

+- store the digest in an integrity-protected measurement list, so that it

• can be sent to a remote verifier for analysis;

+- compare the calculated digest with a reference value (usually protected

• with a signature) and deny operations if the file is found corrupted;

+- store the digest in the system log.

+Contribution +------------

I would rename this chapter to "Benefits".

+DIGLIM further enhances the capabilities offered by IMA-based solutions +and, at the same time, makes them more practical to adopt by reusing +existing sources as reference values for integrity decisions.

+Possible sources for digest lists are:

+- RPM headers; +- Debian repository metadata.

+Benefits for IMA Measurement +~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+One of the issues that arises when files are measured by the OS is that, +due to parallel execution, the order in which file accesses happen cannot +be predicted. Since the TPM Platform Configuration Register (PCR) extend +operation, executed after each file measurement, cryptographically binds +the current measurement to the previous ones, the PCR value at the end of a +workload cannot be predicted too.

+Thus, even if the usage of a TPM key, bound to a PCR value, should be +allowed when only good files were accessed, the TPM could unexpectedly deny +an operation on that key if files accesses did not happen as stated by the +key policy (which allows only one of the possible sequences).

+DIGLIM solves this issue by making the PCR value stable over the time and +not dependent on file accesses. The following figure depicts the current +and the new approaches:

+::

• IMA measurement list (current)
• entry# 1st boot 2nd boot 3rd boot

•   +----+---------------+ +----+---------------+ +----+---------------+
  

• 1: | 10 | file1 measur. | | 10 | file3 measur. | | 10 | file2 measur. |

•   +----+---------------+ +----+---------------+ +----+---------------+
  

• 2: | 10 | file2 measur. | | 10 | file2 measur. | | 10 | file3 measur. |

•   +----+---------------+ +----+---------------+ +----+---------------+
  

• 3: | 10 | file3 measur. | | 10 | file1 measur. | | 10 | file4 measur. |

•   +----+---------------+ +----+---------------+ +----+---------------+
  

• PCR: Extend != Extend != Extend

•   file1, file2, file3    file3, file2, file1    file2, file3, file4
  

• PCR Extend definition:

•   PCR(new value) = Hash(Hash(meas. entry), PCR(previous value))
  

+A new entry in the measurement list is created by IMA for each file access. +Assuming that ``file1``, ``file2`` and ``file3`` are files provided by the +software vendor, ``file4`` is an unknown file, the first two PCR values +above represent a good system state, the third a bad system state. The PCR +values are the result of the PCR extend operation performed for each +measurement entry with the digest of the measurement entry as an input.

+::

• IMA measurement list (with DIGLIM)
• dlist
• +--------------+
• | header |
• +--------------+
• | file1 digest |
• | file2 digest |
• | file3 digest |
• +--------------+

+``dlist`` is a digest list containing the digest of ``file1``, ``file2`` +and ``file3``. In the intended scenario, it is generated by a software +vendor at the end of the building process, and retrieved by the +administrator of the system where the digest list is loaded.

+::

• entry# 1st boot 2nd boot 3rd boot

•   +----+---------------+ +----+---------------+ +----+---------------+
  

• 0: | 11 | dlist measur. | | 11 | dlist measur. | | 11 | dlist measur. |

•   +----+---------------+ +----+---------------+ +----+---------------+
  

• 1: < file1 measur. skip > < file3 measur. skip > < file2 measur. skip >
• 2: < file2 measur. skip > < file2 measur. skip > < file3 measur. skip >

•                                                 +----+---------------+
  

• 3: < file3 measur. skip > < file1 measur. skip > | 11 | file4 measur. |

•                                                 +----+---------------+
  

• PCR: Extend = Extend != Extend

•   dlist                  dlist                  dlist, file4
  

+The first entry in the measurement list contains the digest of the digest +list uploaded to the kernel at kernel initialization time.

+When a file is accessed, IMA queries DIGLIM with the calculated file digest +and, if it is found, IMA skips the measurement.

+Thus, the only information sent to remote verifiers are: the list of +files that could possibly be accessed (from the digest list), but not if +they were accessed and when; the measurement of unknown files.

+Despite providing less information, this solution has the advantage that +the good system state (i.e. when only ``file1``, ``file2`` and ``file3`` +are accessed) now can be represented with a deterministic PCR value (the +PCR is extended only with the measurement of the digest list). Also, the +bad system state can still be distinguished from the good state (the PCR is +extended also with the measurement of ``file4``).

+If a TPM key is bound to the good PCR value, the TPM would allow the key to +be used if ``file1``, ``file2`` or ``file3`` are accessed, regardless of +the sequence in which they are accessed (the PCR value does not change), +and would revoke the permission when the unknown ``file4`` is accessed (the +PCR value changes). If a system is able to establish a TLS connection with +a peer, this implicitly means that the system was in a good state (i.e. +``file4`` was not accessed, otherwise the TPM would have denied the usage +of the TPM key due to the key policy).

+Benefits for IMA Appraisal +~~~~~~~~~~~~~~~~~~~~~~~~~~

+Extending secure boot to applications means being able to verify the +provenance of files accessed. IMA does it by verifying file signatures with +a key that it trusts, which requires Linux distribution vendors to +additionally include in the package header a signature for each file that +must be verified (there is the dedicated ``RPMTAG_FILESIGNATURES`` section +in the RPM header).

+The proposed approach would be instead to verify data provenance from +already available metadata (file digests) in existing packages. IMA would +verify the signature of package metadata and search file digests extracted +from package metadata and added to the hash table in the kernel.

+For RPMs, file digests can be found in the ``RPMTAG_FILEDIGESTS`` section +of ``RPMTAG_IMMUTABLE``, whose signature is in ``RPMTAG_RSAHEADER``. For +DEBs, file digests (unsafe to use due to a weak digest algorithm) can be +found in the ``md5sum`` file, which can be indirectly verified from +``Release.gpg``.

+The following figure highlights the differences between the current and the +proposed approach.

+::

• IMA appraisal (current solution, with file signatures):

•                                                     appraise
  

•                                                  +-----------+
  

•                                                  V           |
  

• +-------------------------+-----+ +-------+-----+ |
• | RPM header | | ima rpm | file1 | sig | |
• | ... | | plugin +-------+-----+ +-----+
• | file1 sig [to be added] | sig |--------> ... | IMA |
• | ... | | +-------+-----+ +-----+
• | fileN sig [to be added] | | | fileN | sig |
• +-------------------------+-----+ +-------+-----+

+In this case, file signatures must be added to the RPM header, so that the +``ima`` rpm plugin can extract them together with the file content. The RPM +header signature is not used.

+::

• IMA appraisal (with DIGLIM):

•                                kernel hash table
  

•                                with RPM header content
  

•                                +---+    +--------------+
  

•                                |   |--->| file1 digest |
  

•                                +---+    +--------------+
  

•                                 ...
  

•                                +---+         appraise (file1)
  

•                                |   |  <--------------+
  

• +----------------+-----+ +---+ |
• | RPM header | | ^ |
• | ... | | digest_list | |
• | file1 digest | sig | rpm plugin | +-------+ +-----+
• | ... | |-------------+--->| file1 | | IMA |
• | fileN digest | | +-------+ +-----+
• +----------------+-----+ |

•                 ^                                    |
  

•                 +------------------------------------+
  

•                         appraise (RPM header)
  

+In this case, the RPM header is used as it is, and its signature is used +for IMA appraisal. Then, the ``digest_list`` rpm plugin executes the user +space parser to parse the RPM header and add the extracted digests to an +hash table in the kernel. IMA appraisal of the files in the RPM package +consists in searching their digest in the hash table.

+Other than reusing available information as digest list, another advantage +is the lower computational overhead compared to the solution with file +signatures (only one signature verification for many files and digest +lookup, instead of per file signature verification, see `Preliminary +Performance Evaluation`_ for more details).

+Lifecycle +---------

+The lifecycle of DIGLIM is represented in the following figure:

+::

You could just use:

The lifecycle of DIGLIM is represented in the following figure::

• Vendor premises (release process with modifications):
• +------------+ +-----------------------+ +------------------------+
• | 1. build a | | 2. generate and sign | | 3. publish the package |
• | package |-->| a digest list from |-->| and digest list in |
• | | | packaged files | | a repository |
• +------------+ +-----------------------+ +------------------------+

•                                                             |
  

•                                                             |
  

• User premises: |

•                                                             V
  

• +---------------------+ +------------------------+ +-----------------+
• | 6. use digest lists | | 5. download the digest | | 4. download and |
• | for measurement |<--| list and upload to |<--| install the |
• | and/or appraisal | | the kernel | | package |
• +---------------------+ +------------------------+ +-----------------+

+The figure above represents all the steps when a digest list is +generated separately. However, as mentioned in `Contribution`_, in most +cases existing packages can be already used as a source for digest lists, +limiting the effort for software vendors.

+If, for example, RPMs are used as a source for digest lists, the figure +above becomes:

+::

Same here.

• Vendor premises (release process without modifications):
• +------------+ +------------------------+
• | 1. build a | | 2. publish the package |
• | package |-->| in a repository |---------------------+
• | | | | |
• +------------+ +------------------------+ |

•                                                             |
  

•                                                             |
  

• User premises: |

•                                                             V
  

• +---------------------+ +------------------------+ +-----------------+
• | 5. use digest lists | | 4. extract digest list | | 3. download and |
• | for measurement |<--| from the package |<--| install the |
• | and/or appraisal | | and upload to the | | package |
• | | | kernel | | |
• +---------------------+ +------------------------+ +-----------------+

+Step 4 can be performed with the ``digest_list`` rpm plugin and the user +space parser, without changes to rpm itself.

+Security Assumptions +--------------------

+As mentioned in the `Introduction`_, DIGLIM will be primarily used in +conjunction with IMA to enforce a mandatory policy on all user space +processes, including those owned by root. Even root, in a system with a +locked-down kernel, cannot affect the enforcement of the mandatory policy +or, if changes are permitted, it cannot do so without being detected.

+Given that the target of the enforcement are user space processes, DIGLIM +cannot be placed in the target, as a Mandatory Access Control (MAC) design +is required to have the components responsible to enforce the mandatory +policy separated from the target.

+While locking-down a system and limiting actions with a mandatory policy is +generally perceived by users as an obstacle, it has noteworthy benefits for +the users themselves.

+First, it would timely block attempts by malicious software to steal or +misuse user assets. Although users could query the package managers to +detect them, detection would happen after the fact, or it wouldn't happen +at all if the malicious software tampered with package managers. With a +mandatory policy enforced by the kernel, users would still be able to +decide which software they want to be executed except that, unlike package +managers, the kernel is not affected by user space processes or root.

+Second, it might make systems more easily verifiable from outside, due to +the limited actions the system allows. When users connect to a server, not +only they would be able to verify the server identity, which is already +possible with communication protocols like TLS, but also if the software +running on that server can be trusted to handle their sensitive data.

+Adoption +--------

+A former version of DIGLIM is used in the following OSes:

+- openEuler 20.09

• https://github.com/openeuler-mirror/kernel/tree/openEuler-20.09

+- openEuler 21.03

• https://github.com/openeuler-mirror/kernel/tree/openEuler-21.03

+Originally, DIGLIM was part of IMA (known as IMA Digest Lists). In this +version, it has been redesigned as a standalone module with an API that +makes its functionality accessible by IMA and, eventually, other +subsystems.

+User Space Support +------------------

+Digest lists can be generated and managed with ``digest-list-tools``:

+https://github.com/openeuler-mirror/digest-list-tools

+It includes two main applications:

+- ``gen_digest_lists``: generates digest lists from files in the

• filesystem or from the RPM database (more digest list sources can be
• supported);

+- ``manage_digest_lists``: converts and uploads digest lists to the

• kernel.

+Integration with rpm is done with the ``digest_list`` plugin:

+https://gitee.com/src-openeuler/rpm/blob/master/Add-digest-list-plugin.patch

+This plugin writes the RPM header and its signature to a file, so that the +file is ready to be appraised by IMA, and calls the user space parser to +convert and upload the digest list to the kernel.

+Simple Usage Example (Tested with Fedora 33) +--------------------------------------------

+1. Digest list generation (RPM headers and their signature are copied to

• the specified directory):

+.. code-block:: bash

• # mkdir /etc/digest_lists
• # gen_digest_lists -t file -f rpm+db -d /etc/digest_lists -o add

+2. Digest list upload with the user space parser:

+.. code-block:: bash

• # manage_digest_lists -p add-digest -d /etc/digest_lists

+3. First digest list query:

+.. code-block:: bash

• # echo sha256-$(sha256sum /bin/cat) > /sys/kernel/security/integrity/diglim/digest_query
• # cat /sys/kernel/security/integrity/diglim/digest_query
• sha256-[...]-0-file_list-rpm-coreutils-8.32-18.fc33.x86_64 (actions: 0): version: 1, algo: sha256, type: 2, modifiers: 1, count: 106, datalen: 3392

+4. Second digest list query:

+.. code-block:: bash

• # echo sha256-$(sha256sum /bin/zip) > /sys/kernel/security/integrity/diglim/digest_query
• # cat /sys/kernel/security/integrity/diglim/digest_query
• sha256-[...]-0-file_list-rpm-zip-3.0-27.fc33.x86_64 (actions: 0): version: 1, algo: sha256, type: 2, modifiers: 1, count: 4, datalen: 128

+Preliminary Performance Evaluation +----------------------------------

+This section provides an initial estimation of the overhead introduced by +DIGLIM. The estimation has been performed on a Fedora 33 virtual machine +with 1447 packages installed. The virtual machine has 16 vCPU (host CPU: +AMD Ryzen Threadripper PRO 3955WX 16-Cores) and 2G of RAM (host memory: +64G). The virtual machine also has a vTPM with libtpms and swtpm as +backend.

+After writing the RPM headers to files, the size of the directory +containing them is 36M.

+After converting the RPM headers to the compact digest list, the size of +the data being uploaded to the kernel is 3.6M.

+The time to load the entire RPM database is 0.628s.

+After loading the digest lists to the kernel, the slab usage due to +indexing is (obtained with slab_nomerge in the kernel command line):

+::

• OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
• 118144 118144 100% 0,03K 923 128 3692K digest_list_item_ref_cache
• 102400 102400 100% 0,03K 800 128 3200K digest_item_cache
• 2646 2646 100% 0,09K 63 42 252K digest_list_item_cache

+The stats, obtained from the ``digests_count`` interface, introduced later, +are:

+::

• Parser digests: 0
• File digests: 99100
• Metadata digests: 0
• Digest list digests: 1423

+On this installation, this would be the worst case in which all files are +measured and/or appraised, which is currently not recommended without +enforcing an integrity policy protecting mutable files. Infoflow LSM is a +component to accomplish this task:

+https://patchwork.kernel.org/project/linux-integrity/cover/20190818235745.14...

+The first manageable goal of IMA with DIGLIM is to use an execution policy, +with measurement and/or appraisal of files executed or mapped in memory as +executable (in addition to kernel modules and firmware). In this +case, the digest list contains the digest only for those files. The numbers +above change as follows.

+After converting the RPM headers to the compact digest list, the size of +the data being uploaded to the kernel is 208K.

+The time to load the digest of binaries and shared libraries is 0.062s.

+After loading the digest lists to the kernel, the slab usage due to +indexing is:

+::

• OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
• 7168 7168 100% 0,03K 56 128 224K digest_list_item_ref_cache
• 7168 7168 100% 0,03K 56 128 224K digest_item_cache
• 1134 1134 100% 0,09K 27 42 108K digest_list_item_cache

+The stats, obtained from the ``digests_count`` interface, are:

+::

• Parser digests: 0
• File digests: 5986
• Metadata digests: 0
• Digest list digests: 1104

+Comparison with IMA +~~~~~~~~~~~~~~~~~~~

+This section compares the performance between the current solution for IMA +measurement and appraisal, and IMA with DIGLIM.

+Workload A (without DIGLIM):

+#. cat file[0-5985] > /dev/null

+Workload B (with DIGLIM):

+#. echo $PWD/0-file_list-compact-file[0-1103] > <securityfs>/integrity/diglim/digest_list_add +#. cat file[0-5985] > /dev/null

+Workload A execution time without IMA policy:

+::

• real 0m0,155s
• user 0m0,008s
• sys 0m0,066s

+Measurement +...........

+IMA policy:

+::

• measure fowner=2000 func=FILE_CHECK mask=MAY_READ use_diglim=allow pcr=11 ima_template=ima-sig

+``use_diglim`` is a policy keyword not yet supported by IMA.

+Workload A execution time with IMA and 5986 files with signature measured:

+::

• real 0m8,273s
• user 0m0,008s
• sys 0m2,537s

+Workload B execution time with IMA, 1104 digest lists with signature +measured and uploaded to the kernel, and 5986 files with signature accessed +but not measured (due to the file digest being found in the hash table):

+::

• real 0m1,837s
• user 0m0,036s
• sys 0m0,583s

+Appraisal +.........

+IMA policy:

+::

• appraise fowner=2000 func=FILE_CHECK mask=MAY_READ use_diglim=allow

+``use_diglim`` is a policy keyword not yet supported by IMA.

+Workload A execution time with IMA and 5986 files with file signature +appraised:

+::

• real 0m2,197s
• user 0m0,011s
• sys 0m2,022s

+Workload B execution time with IMA, 1104 digest lists with signature +appraised and uploaded to the kernel, and with 5986 files with signature +not verified (due to the file digest being found in the hash table):

+::

• real 0m0,982s
• user 0m0,020s
• sys 0m0,865s

diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst index 16335de04e8c..6c3aea41c55b 100644 --- a/Documentation/security/index.rst +++ b/Documentation/security/index.rst @@ -17,3 +17,4 @@ Security Documentation tpm/index digsig landlock

• diglim/index

diff --git a/MAINTAINERS b/MAINTAINERS index 6c8be735cc91..c914dadd7e65 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5452,6 +5452,15 @@ L: linux-gpio@vger.kernel.org S: Maintained F: drivers/gpio/gpio-gpio-mm.c +DIGLIM +M: Roberto Sassu roberto.sassu@huawei.com +L: linux-integrity@vger.kernel.org +S: Supported +T: git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git +F: Documentation/security/diglim/architecture.rst +F: Documentation/security/diglim/index.rst +F: Documentation/security/diglim/introduction.rst

DIOLAN U2C-12 I2C DRIVER M: Guenter Roeck linux@roeck-us.net L: linux-i2c@vger.kernel.org

Thanks, Mauro

From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Tuesday, July 27, 2021 4:44 PM On Mon, Jul 26, 2021 at 06:36:50PM +0200, Roberto Sassu wrote:

...

--- /dev/null +++ b/include/uapi/linux/diglim.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/*

• • Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
• • Author: Roberto Sassu roberto.sassu@huawei.com
• • DIGLIM definitions exported to user space, useful for generating digest
• • lists.
• */

+#ifndef _UAPI__LINUX_DIGLIM_H +#define _UAPI__LINUX_DIGLIM_H

+#include <linux/types.h> +#include <linux/hash_info.h>

+enum compact_types { COMPACT_KEY, COMPACT_PARSER,

COMPACT_FILE,

...

•      COMPACT_METADATA, COMPACT_DIGEST_LIST,
  

COMPACT__LAST };

...

+enum compact_modifiers { COMPACT_MOD_IMMUTABLE,

COMPACT_MOD__LAST };

...

+enum compact_actions { COMPACT_ACTION_IMA_MEASURED,

•        COMPACT_ACTION_IMA_APPRAISED,
  

•        COMPACT_ACTION_IMA_APPRAISED_DIGSIG,
  

•        COMPACT_ACTION__LAST };
  

+enum ops { DIGEST_LIST_ADD, DIGEST_LIST_DEL, DIGEST_LIST_OP__LAST };

+/**

• • struct compact_list_hdr - header of the following concatenated digests
• • @version: version of the digest list
• • @_reserved: field reserved for future use
• • @type: type of digest list among enum compact_types
• • @modifiers: additional attributes among (1 << enum compact_modifiers)

I do not understand this description, what does it mean?

Hi Greg

yes, it is not very clear.

@modifiers is a bitmask where each bit corresponds to a different attribute. enum compact_modifiers defines which bit position is assigned to each attribute.

...

• • @algo: digest algorithm

Is this also a #define or an enum? Where is the list of them?

@algo is an enum defined in include/uapi/linux/hash_info.h.

...

• • @count: number of digests
• • @datalen: length of concatenated digests

Where does this count and length come into play as nothing else is in this structure?

Each digest list must begin with this structure. From it, the parser knows how much data it should expect afterwards. After the data, there could be another or more blocks of this structure and following data.

There is an example in the 'Compact Digest List Example' subsection, in Documentation/security/diglim/implementation.rst.

...

• • A digest list is a set of blocks composed by struct compact_list_hdr and
• • the following concatenated digests.
• */

+struct compact_list_hdr {

• __u8 version;
• __u8 _reserved;

You MUST check this for 0 today, and document it above. If not, you can never use it in the future.

Ok, yes. I will add it.

Thanks

Roberto

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

...

• __le16 type;
• __le16 modifiers;
• __le16 algo;
• __le32 count;
• __le32 datalen;

+} __packed;

+#endif /*_UAPI__LINUX_DIGLIM_H*/

2.25.1

From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Tuesday, July 27, 2021 5:44 PM On Tue, Jul 27, 2021 at 03:35:16PM +0000, Roberto Sassu wrote:

...

...

From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Tuesday, July 27, 2021 4:44 PM On Mon, Jul 26, 2021 at 06:36:50PM +0200, Roberto Sassu wrote:

...

--- /dev/null +++ b/include/uapi/linux/diglim.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/*

• • Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
• • Author: Roberto Sassu roberto.sassu@huawei.com
• • DIGLIM definitions exported to user space, useful for generating

digest

...

...

...

• • lists.
• */

+#ifndef _UAPI__LINUX_DIGLIM_H +#define _UAPI__LINUX_DIGLIM_H

+#include <linux/types.h> +#include <linux/hash_info.h>

+enum compact_types { COMPACT_KEY, COMPACT_PARSER,

COMPACT_FILE,

...

•      COMPACT_METADATA, COMPACT_DIGEST_LIST,
  

COMPACT__LAST };

...

+enum compact_modifiers { COMPACT_MOD_IMMUTABLE,

COMPACT_MOD__LAST };

...

+enum compact_actions { COMPACT_ACTION_IMA_MEASURED,

•        COMPACT_ACTION_IMA_APPRAISED,
  

•        COMPACT_ACTION_IMA_APPRAISED_DIGSIG,
  

•        COMPACT_ACTION__LAST };
  

+enum ops { DIGEST_LIST_ADD, DIGEST_LIST_DEL,

DIGEST_LIST_OP__LAST };

...

...

...

+/**

• • struct compact_list_hdr - header of the following concatenated

digests

...

...

...

• • @version: version of the digest list
• • @_reserved: field reserved for future use
• • @type: type of digest list among enum compact_types
• • @modifiers: additional attributes among (1 << enum

compact_modifiers)

...

...

I do not understand this description, what does it mean?

Hi Greg

yes, it is not very clear.

@modifiers is a bitmask where each bit corresponds to a different attribute. enum compact_modifiers defines which bit position is assigned to each attribute.

Watch out with endian issues and bitmasks... Anyway, please document this.

...

...

...

• • @algo: digest algorithm

Is this also a #define or an enum? Where is the list of them?

@algo is an enum defined in include/uapi/linux/hash_info.h.

Please say that.

...

...

...

• • @count: number of digests
• • @datalen: length of concatenated digests

Where does this count and length come into play as nothing else is in this structure?

Each digest list must begin with this structure. From it, the parser knows how much data it should expect afterwards. After the data, there could be another or more blocks of this structure and following data.

Ah, that was not obvious at all :)

Why do you not have a __u8 data[]; type field as the last one here for that memory so you can access it easier?

After the digest list is parsed, I'm accessing the digest with the offset from the beginning of the digest list. If the offset was relative to the header, it could have been useful. I could add the new field, but I'm afraid of the incompatibility with existing tools that we have.

Thanks

Roberto

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

thanks,

greg k-h

From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Tuesday, July 27, 2021 6:13 PM On Tue, Jul 27, 2021 at 04:09:37PM +0000, Roberto Sassu wrote:

...

...

From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Tuesday, July 27, 2021 5:44 PM On Tue, Jul 27, 2021 at 03:35:16PM +0000, Roberto Sassu wrote:

...

...

From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: Tuesday, July 27, 2021 4:44 PM On Mon, Jul 26, 2021 at 06:36:50PM +0200, Roberto Sassu wrote:

...

--- /dev/null +++ b/include/uapi/linux/diglim.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/*

• • Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
• • Author: Roberto Sassu roberto.sassu@huawei.com
• • DIGLIM definitions exported to user space, useful for generating

digest

...

...

...

• • lists.
• */

+#ifndef _UAPI__LINUX_DIGLIM_H +#define _UAPI__LINUX_DIGLIM_H

+#include <linux/types.h> +#include <linux/hash_info.h>

+enum compact_types { COMPACT_KEY, COMPACT_PARSER,

COMPACT_FILE,

...

•      COMPACT_METADATA, COMPACT_DIGEST_LIST,
  

COMPACT__LAST };

...

+enum compact_modifiers { COMPACT_MOD_IMMUTABLE,

COMPACT_MOD__LAST };

...

+enum compact_actions { COMPACT_ACTION_IMA_MEASURED,

•        COMPACT_ACTION_IMA_APPRAISED,
  

•        COMPACT_ACTION_IMA_APPRAISED_DIGSIG,
  

•        COMPACT_ACTION__LAST };
  

+enum ops { DIGEST_LIST_ADD, DIGEST_LIST_DEL,

DIGEST_LIST_OP__LAST };

...

...

...

+/**

• • struct compact_list_hdr - header of the following concatenated

digests

...

...

...

• • @version: version of the digest list
• • @_reserved: field reserved for future use
• • @type: type of digest list among enum compact_types
• • @modifiers: additional attributes among (1 << enum

compact_modifiers)

...

...

I do not understand this description, what does it mean?

Hi Greg

yes, it is not very clear.

@modifiers is a bitmask where each bit corresponds to a different attribute. enum compact_modifiers defines which bit position is assigned to each attribute.

Watch out with endian issues and bitmasks... Anyway, please document this.

...

...

...

• • @algo: digest algorithm

Is this also a #define or an enum? Where is the list of them?

@algo is an enum defined in include/uapi/linux/hash_info.h.

Please say that.

...

...

...

• • @count: number of digests
• • @datalen: length of concatenated digests

Where does this count and length come into play as nothing else is in this structure?

Each digest list must begin with this structure. From it, the parser knows how much data it should expect afterwards. After the data, there could

be

...

...

...

another or more blocks of this structure and following data.

Ah, that was not obvious at all :)

Why do you not have a __u8 data[]; type field as the last one here for that memory so you can access it easier?

After the digest list is parsed, I'm accessing the digest with the offset from the beginning of the digest list. If the offset was relative to the header, it

could

...

have been useful. I could add the new field, but I'm afraid of the

incompatibility

...

with existing tools that we have.

What tools? This isn't a feature in the kernel yet, so we have no legacy to support, right?

Yes, right. We shouldn't be limited by previously written code.

Thanks

Roberto

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

thanks,

greg k-h

From: Mauro Carvalho Chehab [mailto:mchehab+huawei@kernel.org] Sent: Wednesday, July 28, 2021 1:31 PM Em Mon, 26 Jul 2021 18:36:50 +0200 Roberto Sassu roberto.sassu@huawei.com escreveu:

...

Introduce the basic definitions, exported to user space, to use digest lists. The definitions, added to include/uapi/linux/diglim.h, are documented in Documentation/security/diglim/implementation.rst.

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

.../security/diglim/implementation.rst | 97 +++++++++++++++++++ Documentation/security/diglim/index.rst | 1 + MAINTAINERS | 2 + include/uapi/linux/diglim.h | 51 ++++++++++ 4 files changed, 151 insertions(+) create mode 100644 Documentation/security/diglim/implementation.rst create mode 100644 include/uapi/linux/diglim.h

diff --git a/Documentation/security/diglim/implementation.rst

b/Documentation/security/diglim/implementation.rst

...

new file mode 100644 index 000000000000..59a180b3bb3f --- /dev/null +++ b/Documentation/security/diglim/implementation.rst @@ -0,0 +1,97 @@ +.. SPDX-License-Identifier: GPL-2.0

+Implementation +==============

+This section describes the implementation of DIGLIM.

+Basic Definitions +-----------------

+This section introduces the basic definitions required to use DIGLIM.

+Compact Digest List Format +~~~~~~~~~~~~~~~~~~~~~~~~~~

+.. kernel-doc:: include/uapi/linux/diglim.h

• :identifiers: compact_list_hdr

+Compact Types +.............

+Digests can be of different types:

+- ``COMPACT_PARSER``: digests of executables which are given the ability

to

...

• parse digest lists not in the compact format and to upload to the kernel
• the digest list converted to the compact format;

+- ``COMPACT_FILE``: digests of regular files; +- ``COMPACT_METADATA``: digests of file metadata (e.g. the digest

• calculated by EVM to verify a portable signature);

+- ``COMPACT_DIGEST_LIST``: digests of digest lists (only used internally by

• the kernel).

+Different users of DIGLIM might query digests with different compact types. +For example, IMA would be interested in COMPACT_FILE, as it deals with +regular files, while EVM would be interested in COMPACT_METADATA, as it +verifies file metadata.

+Compact Modifiers +.................

+Digests can also have specific attributes called modifiers (bit position):

+- ``COMPACT_MOD_IMMUTABLE``: file content or metadata should not be

• modifiable.

+IMA might use this information to deny open for writing, or EVM to deny +setxattr operations.

+Actions +.......

+This section defines a set of possible actions that have been executed on +the digest lists (bit position):

+- ``COMPACT_ACTION_IMA_MEASURED``: the digest list has been

measured by

...

• IMA;

+- ``COMPACT_ACTION_IMA_APPRAISED``: the digest list has been

successfully

...

• appraised by IMA;

+- ``COMPACT_ACTION_IMA_APPRAISED_DIGSIG``: the digest list has been

• successfully appraised by IMA by verifying a digital signature.

+This information might help users of DIGLIM to decide whether to use the +result of a queried digest.

+For example, if a digest belongs to a digest list that was not measured +before, IMA should ignore the result of the query, as the measurement list +sent to remote verifiers would lack which digests have been uploaded to

the

...

+kernel.

+Compact Digest List Example +...........................

+::

• version: 1, type: 2, modifiers: 0 algo: 4, count: 3, datalen: 96
• <SHA256 digest1><SHA256 digest2><SHA256 digest3>
• version: 1, type: 3, modifiers: 1 algo: 6, count: 2, datalen: 128
• <SHA512 digest1><SHA512 digest2>

+This digest list consists of two blocks. The first block contains three +SHA256 digests of regular files. The second block contains two SHA512 +digests of immutable metadata.

+Compact Digest List Operations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+Finally, this section defines the possible operations that can be performed +with digest lists:

+- ``DIGEST_LIST_ADD``: the digest list is being added; +- ``DIGEST_LIST_DEL``: the digest list is being deleted. diff --git a/Documentation/security/diglim/index.rst

b/Documentation/security/diglim/index.rst

...

index 0fc5ab019bc0..4771134c2f0d 100644 --- a/Documentation/security/diglim/index.rst +++ b/Documentation/security/diglim/index.rst @@ -9,3 +9,4 @@ Digest Lists Integrity Module (DIGLIM)

introduction
architecture

• implementation

diff --git a/MAINTAINERS b/MAINTAINERS index c914dadd7e65..f61f5239468a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5458,8 +5458,10 @@ L: linux-integrity@vger.kernel.org S: Supported T: git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git F: Documentation/security/diglim/architecture.rst +F: Documentation/security/diglim/implementation.rst F: Documentation/security/diglim/index.rst F: Documentation/security/diglim/introduction.rst +F: include/uapi/linux/diglim.h

DIOLAN U2C-12 I2C DRIVER M: Guenter Roeck linux@roeck-us.net diff --git a/include/uapi/linux/diglim.h b/include/uapi/linux/diglim.h new file mode 100644 index 000000000000..8a33d1f0fefb --- /dev/null +++ b/include/uapi/linux/diglim.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/*

• • Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
• • Author: Roberto Sassu roberto.sassu@huawei.com
• • DIGLIM definitions exported to user space, useful for generating digest
• • lists.
• */

+#ifndef _UAPI__LINUX_DIGLIM_H +#define _UAPI__LINUX_DIGLIM_H

+#include <linux/types.h> +#include <linux/hash_info.h>

+enum compact_types { COMPACT_KEY, COMPACT_PARSER,

COMPACT_FILE,

...

•      COMPACT_METADATA, COMPACT_DIGEST_LIST,
  

COMPACT__LAST };

...

+enum compact_modifiers { COMPACT_MOD_IMMUTABLE,

COMPACT_MOD__LAST };

...

+enum compact_actions { COMPACT_ACTION_IMA_MEASURED,

•        COMPACT_ACTION_IMA_APPRAISED,
  

•        COMPACT_ACTION_IMA_APPRAISED_DIGSIG,
  

•        COMPACT_ACTION__LAST };
  

+enum ops { DIGEST_LIST_ADD, DIGEST_LIST_DEL, DIGEST_LIST_OP__LAST };

+/**

• • struct compact_list_hdr - header of the following concatenated digests
• • @version: version of the digest list
• • @_reserved: field reserved for future use
• • @type: type of digest list among enum compact_types
• • @modifiers: additional attributes among (1 << enum compact_modifiers)
• • @algo: digest algorithm
• • @count: number of digests
• • @datalen: length of concatenated digests
• • A digest list is a set of blocks composed by struct compact_list_hdr and
• • the following concatenated digests.
• */

+struct compact_list_hdr {

• __u8 version;
• __u8 _reserved;
• __le16 type;
• __le16 modifiers;
• __le16 algo;
• __le32 count;
• __le32 datalen;

+} __packed; +#endif /*_UAPI__LINUX_DIGLIM_H*/

Besides Greg's notes, I'm wondering why to enforce a particular endness here. I mean, this is uAPI. I would expect it to use the CPU endianness instead, in order to avoid uneeded conversions.

Also Greg had the same concern. I hoped the Lifecycle section clarified the fact that digest lists are generated by software vendors not the local system. Should I add something more in the documentation?

Thanks

Roberto

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

Thanks, Mauro

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).

• 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.

• {

•     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.

+#endif /*__DIGLIM_INTERNAL_H*/

Thanks, Mauro

From: Mauro Carvalho Chehab [mailto:mchehab+huawei@kernel.org] Sent: Wednesday, July 28, 2021 2:19 PM Em Mon, 26 Jul 2021 18:36:52 +0200 Roberto Sassu roberto.sassu@huawei.com escreveu:

...

Introduce the methods requires to manage the three objects defined.

• digest_item methods:

  • digest_add()
  • digest_del()
  • __digest_lookup()
  • diglim_digest_get_info()

• digest_list_item_ref methods:

  • digest_list_ref_add()
  • digest_list_ref_del()

• digest_list_item methods:

  • digest_list_add()
  • digest_list_del()

More information about these functions can be found in Documentation/security/diglim/implementation.rst.

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

.../security/diglim/implementation.rst | 9 + MAINTAINERS | 2 + include/linux/diglim.h | 28 + security/integrity/Kconfig | 1 + security/integrity/Makefile | 1 + security/integrity/diglim/Kconfig | 11 + security/integrity/diglim/Makefile | 8 + security/integrity/diglim/diglim.h | 20 +- security/integrity/diglim/methods.c | 499 ++++++++++++++++++ 9 files changed, 578 insertions(+), 1 deletion(-) create mode 100644 include/linux/diglim.h create mode 100644 security/integrity/diglim/Kconfig create mode 100644 security/integrity/diglim/Makefile create mode 100644 security/integrity/diglim/methods.c

diff --git a/Documentation/security/diglim/implementation.rst

b/Documentation/security/diglim/implementation.rst

...

index 6002049612a1..54af23b2f5f1 100644 --- a/Documentation/security/diglim/implementation.rst +++ b/Documentation/security/diglim/implementation.rst @@ -200,3 +200,12 @@ Similarly: 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).

+Methods +-------

+This section introduces the methods requires to manage the three objects +defined.

+.. kernel-doc:: security/integrity/diglim/methods.c diff --git a/MAINTAINERS b/MAINTAINERS index f7592d41367d..9e085a36654a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5461,8 +5461,10 @@ F:

Documentation/security/diglim/architecture.rst

...

F: Documentation/security/diglim/implementation.rst F: Documentation/security/diglim/index.rst F: Documentation/security/diglim/introduction.rst +F: include/linux/diglim.h F: include/uapi/linux/diglim.h F: security/integrity/diglim/diglim.h +F: security/integrity/diglim/methods.c

DIOLAN U2C-12 I2C DRIVER M: Guenter Roeck linux@roeck-us.net diff --git a/include/linux/diglim.h b/include/linux/diglim.h new file mode 100644 index 000000000000..d4b4548a288b --- /dev/null +++ b/include/linux/diglim.h @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/*

• • Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
• • Author: Roberto Sassu roberto.sassu@huawei.com
• • DIGLIM functions available for use by kernel subsystems.
• */

+#ifndef __DIGLIM_H +#define __DIGLIM_H

+#include <crypto/hash_info.h> +#include <uapi/linux/diglim.h>

+#ifdef CONFIG_DIGLIM +extern int diglim_digest_get_info(u8 *digest, enum hash_algo algo,

• 		  enum compact_types type, u16 *modifiers,
  

• 		  u8 *actions);
  

+#else +static inline int diglim_digest_get_info(u8 *digest, enum hash_algo algo,

• 			 enum compact_types type,
  

• 			 u16 *modifiers, u8 *actions)
  

+{

• return -ENOENT;

+} +#endif /*CONFIG_DIGLIM*/ +#endif /*__DIGLIM_H*/ diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig index 71f0177e8716..8f94f4dcc052 100644 --- a/security/integrity/Kconfig +++ b/security/integrity/Kconfig @@ -98,5 +98,6 @@ config INTEGRITY_AUDIT

source "security/integrity/ima/Kconfig" source "security/integrity/evm/Kconfig" +source "security/integrity/diglim/Kconfig"

endif # if INTEGRITY diff --git a/security/integrity/Makefile b/security/integrity/Makefile index 7ee39d66cf16..d6166550a6b8 100644 --- a/security/integrity/Makefile +++ b/security/integrity/Makefile @@ -19,3 +19,4 @@ integrity-$(CONFIG_LOAD_PPC_KEYS) +=

platform_certs/efi_parser.o \

...

                                  platform_certs/keyring_handler.o

obj-$(CONFIG_IMA) += ima/ obj-$(CONFIG_EVM) += evm/ +obj-$(CONFIG_DIGLIM) += diglim/ diff --git a/security/integrity/diglim/Kconfig

b/security/integrity/diglim/Kconfig

...

new file mode 100644 index 000000000000..436a76a14337 --- /dev/null +++ b/security/integrity/diglim/Kconfig @@ -0,0 +1,11 @@ +# SPDX-License-Identifier: GPL-2.0-only +# Digest Lists Integrity Module (DIGLIM) +# +config DIGLIM

• bool "Digest Lists Integrity Module (DIGLIM)"
• select SECURITYFS
• select CRYPTO
• select CRYPTO_HASH_INFO
• help

•  DIGLIM provides reference values for file content and metadata,
  

•  that can be used for measurement and appraisal with IMA.
  

diff --git a/security/integrity/diglim/Makefile

b/security/integrity/diglim/Makefile

...

new file mode 100644 index 000000000000..b761ed8cfb3e --- /dev/null +++ b/security/integrity/diglim/Makefile @@ -0,0 +1,8 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Makefile for building Digest Lists Integrity Module (DIGLIM). +#

+obj-$(CONFIG_DIGLIM) += diglim.o

+diglim-y := methods.o diff --git a/security/integrity/diglim/diglim.h

b/security/integrity/diglim/diglim.h

...

index 578253d7e1d1..25851e7d4906 100644 --- a/security/integrity/diglim/diglim.h +++ b/security/integrity/diglim/diglim.h @@ -20,7 +20,7 @@ #include <linux/audit.h> #include <crypto/hash_info.h> #include <linux/hash_info.h> -#include <uapi/linux/diglim.h> +#include <linux/diglim.h>

#define MAX_DIGEST_SIZE 64 #define HASH_BITS 10 @@ -81,6 +81,8 @@ static inline unsigned int hash_key(u8 *digest) return (digest[0] | digest[1] << 8) % DIGLIM_HTABLE_SIZE; }

+extern struct h_table htable[COMPACT__LAST];

it sounds somewhat risky to use just "htable" for a var declared as external.

Ok, adding diglim_ as prefix should be enough.

...

static inline struct compact_list_hdr *get_hdr( struct digest_list_item *digest_list, loff_t hdr_offset) @@ -131,4 +133,20 @@ static inline u8 *get_digest_ref(struct

digest_list_item_ref *ref)

...

return ref->digest_list->buf + ref->digest_offset; }

+struct digest_item *__digest_lookup(u8 *digest, enum hash_algo algo,

• 		    enum compact_types type, u16 *modifiers,
  

• 		    u8 *actions);
  

+struct digest_item *digest_add(u8 *digest, enum hash_algo algo,

• 	       enum compact_types type,
  

• 	       struct digest_list_item *digest_list,
  

• 	       loff_t digest_offset, loff_t hdr_offset);
  

+void digest_del(u8 *digest, enum hash_algo algo, enum compact_types

type,

...

• struct digest_list_item *digest_list, loff_t digest_offset,
  

• loff_t hdr_offset);
  

+struct digest_item *digest_list_add(u8 *digest, enum hash_algo algo,

• 		    loff_t size, u8 *buf, u8 actions,
  

• 		    const char *label);
  

+void digest_list_del(u8 *digest, enum hash_algo algo, u8 actions,

•      struct digest_list_item *digest_list);
  

#endif /*__DIGLIM_INTERNAL_H*/ diff --git a/security/integrity/diglim/methods.c

b/security/integrity/diglim/methods.c

...

new file mode 100644 index 000000000000..7ed61399cfe8 --- /dev/null +++ b/security/integrity/diglim/methods.c @@ -0,0 +1,499 @@ +// 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 manage digest lists.
• */

+#include <linux/vmalloc.h> +#include <linux/module.h> +#include <linux/fault-inject.h>

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

+/* Define a cache for each object type. */ +static struct kmem_cache *digest_list_item_cache __read_mostly; +static struct kmem_cache *digest_list_item_ref_cache __read_mostly; +static struct kmem_cache *digest_item_cache __read_mostly;

+/* Define a hash table for each digest type. */ +struct h_table htable[COMPACT__LAST] = {{

• .queue[0 ... DIGLIM_HTABLE_SIZE - 1] = HLIST_HEAD_INIT

+}};

...

+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS +static DECLARE_FAULT_ATTR(fail_diglim);

+static int __init fail_diglim_debugfs(void) +{

• struct dentry *dir = fault_create_debugfs_attr("fail_diglim", NULL,

• 				       &fail_diglim);
  

• return PTR_ERR_OR_ZERO(dir);

+}

+static inline bool should_fail_diglim(void) +{

• return should_fail(&fail_diglim, 1);

+}

+late_initcall(fail_diglim_debugfs); +#else +static inline bool should_fail_diglim(void) +{

• return false;

+} +#endif

I guess this is a matter of personal preference, but, IMO, it is a lot better to place the debugfs stuff on a separate source file, avoiding ugly #ifdefs in the middle of the code.

Ok, the current code is too small to deserve a separate file, but if later patches would add more stuff, then I would opt to have this on a separate file.

Ok.

Thanks

Roberto

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

...

+/**

• • __digest_lookup - lookup digest and return associated modifiers and

actions

...

• • @digest: digest to lookup
• • @algo: digest algorithm
• • @type: type of digest to lookup (e.g. file, metadata)
• • @modifiers: modifiers (attributes) associated to the found digest
• • @actions: actions performed by IMA on the digest list containing the

digest

...

• • This function searches the given digest in the hash table depending on

the

...

• • passed type and sets the modifiers and actions associated to the digest, if
• • the pointers are not NULL.
• • This function is not intended for external use, as the returned digest item
• • could be freed at any time after it has been returned.
• • diglim_digest_get_info() should be used instead by external callers, as it
• • only returns the modifiers and the actions associated to the digest at the
• • time the digest is searched.
• • RCU protects both the hash table and the linked list of references to the
• • digest lists containing the found digest.
• • Return: a digest_item structure if the digest is found, NULL otherwise.
• */

+struct digest_item *__digest_lookup(u8 *digest, enum hash_algo algo,

• 		    enum compact_types type, u16 *modifiers,
  

• 		    u8 *actions)
  

+{

• struct digest_item *d = NULL;
• struct digest_list_item_ref *ref;
• int digest_len = hash_digest_size[algo];
• unsigned int key = hash_key(digest);
• bool found = false;
• rcu_read_lock();
• hlist_for_each_entry_rcu(d, &htable[type].queue[key], hnext) {

• list_for_each_entry_rcu(ref, &d->refs, list) {
  

• 	if (get_algo_ref(ref) != algo ||
  

• 	    memcmp(get_digest_ref(ref), digest, digest_len))
  

• 		break;
  

• 	found = true;
  

• 	/* There is no need to scan all digest list refs. */
  

• 	if (!modifiers || !actions)
  

• 		break;
  

• 	/*
  

• 	 * The resulting modifiers and actions are the OR of
  

the

...

• 	 * modifiers and actions for each digest list.
  

• 	 */
  

• 	*modifiers |= get_hdr_ref(ref)->modifiers;
  

• 	*actions |= ref->digest_list->actions;
  

• }
  

• if (found)
  

• 	break;
  

• }
• rcu_read_unlock();
• return d;

+}

+/**

• • diglim_digest_get_info - lookup digest and return modifiers and actions
• • @digest: digest to lookup
• • @algo: digest algorithm
• • @type: type of digest to lookup (e.g. file, metadata)
• • @modifiers: modifiers (attributes) associated to the found digest
• • @actions: actions performed by IMA on the digest lists containing the

digest

...

• • This function searches the given digest in the hash table depending on

the

...

• • passed type and sets the modifiers and actions associated to the digest, if
• • the pointers are not NULL.
• • This function is safe for external use, as it does not return pointers of
• • objects that can be freed without the caller notices it.
• • Return: 0 if the digest is found, -ENOENT otherwise.
• */

+int diglim_digest_get_info(u8 *digest, enum hash_algo algo,

• 	   enum compact_types type, u16 *modifiers, u8
  

*actions)

...

+{

• struct digest_item *d;
• d = __digest_lookup(digest, algo, type, modifiers, actions);
• if (!d)

• return -ENOENT;
  

• return 0;

+}

+/**

• • digest_list_ref_add - add reference to a digest list
• • @d: digest a new reference is added to
• • @digest_list: digest list whose reference is being added
• • @digest_offset: offset of the digest in the buffer of the digest list
• • @hdr_offset: offset of the header within the digest list the digest refers

to

...

• • This function adds a new reference to an existing digest list for a given
• • digest. The reference is described by the digest_list_item_ref structure

and

...

• • consists of a pointer of the digest list, the offset of the digest to the
• • beginning of the digest list buffer and the offset of the header the digest
• • refers to (each digest list might be composed of several digest blocks,

each

...

• • prefixed by a header describing the attributes of those digests).
• • Return: 0 if a new digest list reference was successfully added, a negative
• • value otherwise.
• */

+static int digest_list_ref_add(struct digest_item *d,

• 	       struct digest_list_item *digest_list,
  

• 	       loff_t digest_offset, loff_t hdr_offset)
  

+{

• struct digest_list_item_ref *new_ref = NULL;
• u8 *digest = get_digest(digest_list, digest_offset, hdr_offset);
• enum hash_algo algo = get_algo(digest_list, digest_offset, hdr_offset);
• int digest_len = hash_digest_size[algo];
• /* Allocate a new reference. */
• if (!should_fail_diglim())

• new_ref = kmem_cache_alloc(digest_list_item_ref_cache,
  

• 			   GFP_KERNEL);
  

• if (!new_ref) {

• print_hex_dump(KERN_ERR, "digest list ref allocation failed: ",
  

• 	       DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 	       digest_len, true);
  

• return -ENOMEM;
  

• }
• /* Set the new reference. */
• new_ref->digest_list = digest_list;
• /* Converting loff_t -> u32 is fine as long as the digest list < 4G. */
• new_ref->digest_offset = digest_offset;
• new_ref->hdr_offset = hdr_offset;
• list_add_tail_rcu(&new_ref->list, &d->refs);
• print_hex_dump_debug("add digest list ref: ", DUMP_PREFIX_NONE,

• 	     digest_len, 1, digest, digest_len, true);
  

• return 0;

+}

+/**

• • digest_list_ref_del - del reference to a digest list
• • @d: digest a reference is deleted from
• • @digest_list: digest list whose reference is being deleted
• • @digest_offset: offset of the digest in the buffer of the digest list
• • @hdr_offset: offset of the header within the digest list the digest refers

to

...

• • This function searches the reference to an already loaded digest list in

the

...

• • linked list of references stored for each digest item. If the reference is
• • found (if not, it is a bug), the function deletes it from the linked list.
• */

+static void digest_list_ref_del(struct digest_item *d,

• 		struct digest_list_item *digest_list,
  

• 		loff_t digest_offset, loff_t hdr_offset)
  

+{

• struct digest_list_item_ref *ref;
• u8 *digest = get_digest(digest_list, digest_offset, hdr_offset);
• enum hash_algo algo = get_algo(digest_list, digest_offset, hdr_offset);
• int digest_len = hash_digest_size[algo];
• /* Search for a digest list reference. */
• list_for_each_entry(ref, &d->refs, list)

• if (ref->digest_list == digest_list)
  

• 	break;
  

• if (!ref) {

• print_hex_dump(KERN_ERR, "digest list ref not found: ",
  

• 	       DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 	       digest_len, true);
  

• return;
  

• }
• list_del_rcu(&ref->list);
• kmem_cache_free(digest_list_item_ref_cache, ref);
• print_hex_dump_debug("del digest list ref: ", DUMP_PREFIX_NONE,

• 	     digest_len, 1, digest, digest_len, true);
  

+}

+/**

• • digest_add - add a new digest
• • @digest: digest in binary form
• • @algo: digest algorithm
• • @type: digest type
• • @digest_list: digest list the new digest belongs to
• • @digest_offset: offset of the digest in the buffer of the digest list
• • @hdr_offset: offset of the header within the digest list the digest refers

to

...

• • This function first searches if the digest is already in the hash table for
• • the given type. The digest is searched by comparing the passed digest

and

...

• • algorithm with the digest obtained from the first digest list reference
• • (buffer + digest_offset), or from the digest field of a digest list item,
• • for a digest list.
• • If the digest exists, only a new reference is added (there might be

multiple

...

• • references to the same digest list).
• • If the digest is not found, a new digest item is allocated and a reference

to

...

• • the passed digest list is added to that item. The digest item is finally
• • added to the hash table for the given type.
• • Proper locking must be provided by the caller.
• • Return: a new or the found digest item on success, an error pointer
• • otherwise.
• */

+struct digest_item *digest_add(u8 *digest, enum hash_algo algo,

• 	       enum compact_types type,
  

• 	       struct digest_list_item *digest_list,
  

• 	       loff_t digest_offset, loff_t hdr_offset)
  

+{

• int digest_len = hash_digest_size[algo];
• struct digest_item *d;
• int ret;
• /* Search the digest. */
• d = __digest_lookup(digest, algo, type, NULL, NULL);
• if (d) {

• /*
  

•  * Add a new digest list reference to the existing digest item.
  

•  */
  

• ret = digest_list_ref_add(d, digest_list, digest_offset,
  

• 			  hdr_offset);
  

• if (ret < 0)
  

• 	return ERR_PTR(ret);
  

• print_hex_dump_debug("digest add duplicate: ",
  

DUMP_PREFIX_NONE,

...

• 		     digest_len, 1, digest, digest_len, true);
  

• return d;
  

• }
• /* Allocate a new digest item. */
• if (!should_fail_diglim())

• d = kmem_cache_alloc(digest_item_cache, GFP_KERNEL);
  

• if (!d) {

• print_hex_dump_debug("digest allocation failed: ",
  

• 		     DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 		     digest_len, true);
  

• return ERR_PTR(-ENOMEM);
  

• }
• INIT_LIST_HEAD(&d->refs);
• /* Add a new digest list reference to the new digest item. */
• ret = digest_list_ref_add(d, digest_list, digest_offset, hdr_offset);
• if (ret < 0) {

• kmem_cache_free(digest_item_cache, d);
  

• return ERR_PTR(ret);
  

• }
• /* Add the new digest item to the hash table for the given type. */
• hlist_add_head_rcu(&d->hnext,

&htable[type].queue[hash_key(digest)]);

...

• htable[type].len++;
• print_hex_dump_debug("digest add: ", DUMP_PREFIX_NONE,

digest_len, 1,

...

• 	     digest, digest_len, true);
  

• return d;

+}

+/**

• • digest_del - delete a digest with one reference, or just a reference
• • @digest: digest in binary form
• • @algo: digest algorithm
• • @type: digest type
• • @digest_list: digest list the digest belongs to
• • @digest_offset: offset of the digest in the buffer of the digest list
• • @hdr_offset: offset of the header within the digest list the digest refers

to

...

• • This function is called when a digest list is being removed. The digest is
• • first searched in the hash table for the given type. If it is found (if not,
• • it is a bug, because digest lists can be deleted only if they were added
• • previously), a reference of the passed digest list is deleted from the

linked

...

• • list of references of the digest item.
• • If the last reference was deleted, the digest item is also deleted and
• • removed from the hash table.
• • Proper locking must be provided by the caller.
• */

+void digest_del(u8 *digest, enum hash_algo algo, enum compact_types

type,

...

• struct digest_list_item *digest_list, loff_t digest_offset,
  

• loff_t hdr_offset)
  

+{

• struct digest_item *d;
• int digest_len = hash_digest_size[algo];
• /* Search the digest. */
• d = __digest_lookup(digest, algo, type, NULL, NULL);
• if (!d) {

• print_hex_dump(KERN_ERR, "digest not found: ",
  

DUMP_PREFIX_NONE,

...

• 	       digest_len, 1, digest, digest_len, true);
  

• return;
  

• }
• /* Delete a reference of the passed digest list. */
• digest_list_ref_del(d, digest_list, digest_offset, hdr_offset);
• print_hex_dump_debug(!list_empty(&d->refs) ?

• 	     "digest del duplicate: " : "digest del: ",
  

• 	     DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 	     digest_len, true);
  

• /* Return if there are still references. */
• if (!list_empty(&d->refs))

• return;
  

• /*

• * Remove the digest item from the hash table and free it if there are
  

• * no more references left.
  

• */
  

• hlist_del_rcu(&d->hnext);
• htable[type].len--;
• kmem_cache_free(digest_item_cache, d);

+}

+/**

• • digest_list_add - add a new digest list
• • @digest: digest of the digest list in binary form
• • @algo: digest algorithm
• • @size: digest list size
• • @buf: digest list buffer
• • @actions: actions (measure/appraise) performed by IMA on the digest

list

...

• • @label: label to be used to identify the digest list
• • This function allocates a new digest list item, which contains the buffer,
• • size, actions performed by IMA and a label. Each digest list item is
• • associated to a digest item representing the digest of the digest list.
• • This function prevents the same digest list to be added multiple times by
• • searching its digest in the hash table for the COMPACT_DIGEST_LIST

type.

...

• • The passed buffer is copied in a new memory area, to avoid to reference
• • memory that could be freed by the caller.
• • If allocation of a new digest list and the associated buffer was successful,
• • its digest is added to the hash table for the COMPACT_DIGEST_LIST type.
• • Proper locking must be provided by the caller.
• • Return: the digest item associated to the digest list item on success, an
• • error pointer otherwise.
• */

+struct digest_item *digest_list_add(u8 *digest, enum hash_algo algo,

• 		    loff_t size, u8 *buf, u8 actions,
  

• 		    const char *label)
  

+{

• struct digest_item *d;
• struct digest_list_item *digest_list = NULL;
• int digest_len = hash_digest_size[algo];
• /* Search the digest of the digest list. */
• d = __digest_lookup(digest, algo, COMPACT_DIGEST_LIST, NULL,

NULL);

...

• if (d) {

• print_hex_dump(KERN_ERR, "digest list already uploaded: ",
  

• 	       DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 	       digest_len, true);
  

• return ERR_PTR(-EEXIST);
  

• }
• /* Allocate a new digest list. */
• if (!should_fail_diglim())

• digest_list = kmem_cache_alloc(digest_list_item_cache,
  

• 			       GFP_KERNEL);
  

• if (!digest_list) {

• print_hex_dump(KERN_ERR, "digest list allocation failed: ",
  

• 	       DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 	       digest_len, true);
  

• return ERR_PTR(-ENOMEM);
  

• }
• digest_list->buf = NULL;
• digest_list->size = size;
• if (!should_fail_diglim())

• digest_list->buf = kmemdup(buf, size, GFP_KERNEL);
  

• if (!digest_list->buf) {

• print_hex_dump(KERN_ERR, "digest list allocation failed: ",
  

• 	       DUMP_PREFIX_NONE, digest_len, 1, digest,
  

• 	       digest_len, true);
  

• kmem_cache_free(digest_list_item_cache, digest_list);
  

• return ERR_PTR(-ENOMEM);
  

• }
• digest_list->actions = actions;
• memcpy(digest_list->digest, digest, hash_digest_size[algo]);
• digest_list->algo = algo;
• digest_list->label = label;
• /* Add the digest of the digest list to the hash table. */
• d = digest_add(digest, algo, COMPACT_DIGEST_LIST, digest_list, 0, 0);
• if (IS_ERR(d)) {

• kfree(digest_list->buf);
  

• kmem_cache_free(digest_list_item_cache, digest_list);
  

• }
• return d;

+}

+/**

• • digest_list_del - delete an existing digest list
• • @digest: digest of the digest list in binary form
• • @algo: digest algorithm
• • @actions: actions (measure/appraise) performed by IMA on the digest

list

...

• • @digest_list: digest list to delete
• • This function searches the digest of the digest list in the hash table for
• • the COMPACT_DIGEST_LIST type. If it is found, this function frees the

buffer

...

• • and the digest list item allocated in digest_list_add().
• • This function will be executed only for digest lists that were previously
• • added.
• • Proper locking must be provided by the caller.
• */

+void digest_list_del(u8 *digest, enum hash_algo algo, u8 actions,

•      struct digest_list_item *digest_list)
  

+{

• /* Delete the digest item associated to the digest list. */
• digest_del(digest, algo, COMPACT_DIGEST_LIST, digest_list, 0, 0);
• /*

• * Free the buffer and the digest list item allocated when the digest
  

• * list was added.
  

• */
  

• kfree(digest_list->buf);
• kmem_cache_free(digest_list_item_cache, digest_list);

+}

+static int __init digest_list_cache_init(void) +{

• digest_list_item_cache =

kmem_cache_create("digest_list_item_cache",

...

• 				sizeof(struct digest_list_item),
  

• 				0, SLAB_PANIC, NULL);
  

• digest_list_item_ref_cache = kmem_cache_create(

• 			"digest_list_item_ref_cache",
  

• 			sizeof(struct digest_list_item_ref), 0,
  

• 			SLAB_PANIC, NULL);
  

• digest_item_cache = kmem_cache_create("digest_item_cache",

• 			      sizeof(struct digest_item), 0,
  

• 			      SLAB_PANIC, NULL);
  

• return 0;

+}

+late_initcall(digest_list_cache_init)

Thanks, Mauro