diff options
author | Kees Cook <keescook@chromium.org> | 2017-05-13 04:51:39 -0700 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2017-05-18 10:30:14 -0600 |
commit | 7b05b116845bafe8fd19cccb3719333b5f5fe3a2 (patch) | |
tree | ca57a87a5eca7b6968c6e4ff6da12ce4393578ee /Documentation/security/IMA-templates.txt | |
parent | 40fde647ccb0ae8c11d256d271e24d385eed595b (diff) |
doc: ReSTify IMA-templates.txt
Adjust IMA-templates.txt for ReST markup and add to the index for
security/, under the Kernel API Documentation.
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/security/IMA-templates.txt')
-rw-r--r-- | Documentation/security/IMA-templates.txt | 88 |
1 files changed, 0 insertions, 88 deletions
diff --git a/Documentation/security/IMA-templates.txt b/Documentation/security/IMA-templates.txt deleted file mode 100644 index 839b5dad9226..000000000000 --- a/Documentation/security/IMA-templates.txt +++ /dev/null @@ -1,88 +0,0 @@ - IMA Template Management Mechanism - - -==== INTRODUCTION ==== - -The original 'ima' template is fixed length, containing the filedata hash -and pathname. The filedata hash is limited to 20 bytes (md5/sha1). -The pathname is a null terminated string, limited to 255 characters. -To overcome these limitations and to add additional file metadata, it is -necessary to extend the current version of IMA by defining additional -templates. For example, information that could be possibly reported are -the inode UID/GID or the LSM labels either of the inode and of the process -that is accessing it. - -However, the main problem to introduce this feature is that, each time -a new template is defined, the functions that generate and display -the measurements list would include the code for handling a new format -and, thus, would significantly grow over the time. - -The proposed solution solves this problem by separating the template -management from the remaining IMA code. The core of this solution is the -definition of two new data structures: a template descriptor, to determine -which information should be included in the measurement list; a template -field, to generate and display data of a given type. - -Managing templates with these structures is very simple. To support -a new data type, developers define the field identifier and implement -two functions, init() and show(), respectively to generate and display -measurement entries. Defining a new template descriptor requires -specifying the template format (a string of field identifiers separated -by the '|' character) through the 'ima_template_fmt' kernel command line -parameter. At boot time, IMA initializes the chosen template descriptor -by translating the format into an array of template fields structures taken -from the set of the supported ones. - -After the initialization step, IMA will call ima_alloc_init_template() -(new function defined within the patches for the new template management -mechanism) to generate a new measurement entry by using the template -descriptor chosen through the kernel configuration or through the newly -introduced 'ima_template' and 'ima_template_fmt' kernel command line parameters. -It is during this phase that the advantages of the new architecture are -clearly shown: the latter function will not contain specific code to handle -a given template but, instead, it simply calls the init() method of the template -fields associated to the chosen template descriptor and store the result -(pointer to allocated data and data length) in the measurement entry structure. - -The same mechanism is employed to display measurements entries. -The functions ima[_ascii]_measurements_show() retrieve, for each entry, -the template descriptor used to produce that entry and call the show() -method for each item of the array of template fields structures. - - - -==== SUPPORTED TEMPLATE FIELDS AND DESCRIPTORS ==== - -In the following, there is the list of supported template fields -('<identifier>': description), that can be used to define new template -descriptors by adding their identifier to the format string -(support for more data types will be added later): - - - 'd': the digest of the event (i.e. the digest of a measured file), - calculated with the SHA1 or MD5 hash algorithm; - - 'n': the name of the event (i.e. the file name), with size up to 255 bytes; - - 'd-ng': the digest of the event, calculated with an arbitrary hash - algorithm (field format: [<hash algo>:]digest, where the digest - prefix is shown only if the hash algorithm is not SHA1 or MD5); - - 'n-ng': the name of the event, without size limitations; - - 'sig': the file signature. - - -Below, there is the list of defined template descriptors: - - "ima": its format is 'd|n'; - - "ima-ng" (default): its format is 'd-ng|n-ng'; - - "ima-sig": its format is 'd-ng|n-ng|sig'. - - - -==== USE ==== - -To specify the template descriptor to be used to generate measurement entries, -currently the following methods are supported: - - - select a template descriptor among those supported in the kernel - configuration ('ima-ng' is the default choice); - - specify a template descriptor name from the kernel command line through - the 'ima_template=' parameter; - - register a new template descriptor with custom format through the kernel - command line parameter 'ima_template_fmt='. |