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Date: Mon, 18 Nov 2013 17:35:50 +0200
From: Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To: Roberto Sassu <roberto.sassu@...ito.it>
Cc: linux-security-module@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-ima-devel@...ts.sourceforge.net,
Mimi Zohar <zohar@...ibm.com>,
Dmitry Kasatkin <d.kasatkin@...sung.com>,
james.l.morris@...cle.com
Subject: Re: [RFC][PATCH 4/4] ima: added support for new kernel cmdline
parameter ima_template_fmt
On Thu, Nov 7, 2013 at 4:00 PM, Roberto Sassu <roberto.sassu@...ito.it> wrote:
> This patch allows users to provide a custom template format through the
> new kernel command line parameter 'ima_template_fmt'. If the supplied
> format is not valid, IMA uses the default template descriptor.
>
Hi,
Why existing formats are not enough?
Why is it needed?
- Dmitry
> Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>
> ---
> Documentation/kernel-parameters.txt | 4 +++
> Documentation/security/IMA-templates.txt | 29 +++++++++---------
> security/integrity/ima/ima_template.c | 50 ++++++++++++++++++++++++++++++++
> 3 files changed, 68 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 1e8761c..27b14b2 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1199,6 +1199,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> Formats: { "ima" | "ima-ng" }
> Default: "ima-ng"
>
> + ima_template_fmt=
> + [IMA] Define a custom template format.
> + Format: { "field1|...|fieldN" }
> +
> init= [KNL]
> Format: <full_path>
> Run specified binary instead of /sbin/init as init
> diff --git a/Documentation/security/IMA-templates.txt b/Documentation/security/IMA-templates.txt
> index a777e5f..08ea2da 100644
> --- a/Documentation/security/IMA-templates.txt
> +++ b/Documentation/security/IMA-templates.txt
> @@ -27,25 +27,22 @@ 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. While in the current implementation it is possible
> -to define new template descriptors only by adding their definition in the
> -template specific code (ima_template.c), in a future version it will be
> -possible to register a new template on a running kernel by supplying to IMA
> -the desired format string. In this version, IMA initializes at boot time
> -all defined template descriptors by translating the format into an array
> -of template fields structures taken from the set of the supported ones.
> +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 all defined template descriptors
> +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=' kernel command line parameter. 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.
> +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,
> @@ -84,4 +81,6 @@ 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.
> + the 'ima_template=' parameter;
> + - register a new template descriptor with custom format through the kernel
> + command line parameter 'ima_template_fmt='.
> diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
> index bb33576..5a95d06 100644
> --- a/security/integrity/ima/ima_template.c
> +++ b/security/integrity/ima/ima_template.c
> @@ -21,6 +21,7 @@ static struct ima_template_desc defined_templates[] = {
> {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
> {.name = "ima-ng",.fmt = "d-ng|n-ng"},
> {.name = "ima-sig",.fmt = "d-ng|n-ng|sig"},
> + {.name = "",.fmt = ""}, /* placeholder for a custom format */
> };
>
> static struct ima_template_field supported_fields[] = {
> @@ -38,12 +39,16 @@ static struct ima_template_field supported_fields[] = {
>
> static struct ima_template_desc *ima_template;
> static struct ima_template_desc *lookup_template_desc(const char *name);
> +static struct ima_template_field *lookup_template_field(const char *field_id);
>
> static int __init ima_template_setup(char *str)
> {
> struct ima_template_desc *template_desc;
> int template_len = strlen(str);
>
> + if (ima_template)
> + return 1;
> +
> /*
> * Verify that a template with the supplied name exists.
> * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
> @@ -70,6 +75,48 @@ static int __init ima_template_setup(char *str)
> }
> __setup("ima_template=", ima_template_setup);
>
> +static int __init ima_template_fmt_setup(char *str)
> +{
> + int num_templates = ARRAY_SIZE(defined_templates);
> + char *str_ptr_start = str;
> + char *str_ptr_end = str_ptr_start;
> +
> + if (ima_template)
> + return 1;
> +
> + while (str_ptr_start != NULL) {
> + char field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN];
> + int len;
> +
> + str_ptr_end = strpbrk(str_ptr_start, "|");
> + if (str_ptr_end == NULL)
> + len = str + strlen(str) - str_ptr_start;
> + else
> + len = str_ptr_end++ - str_ptr_start;
> +
> + if (len >= IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
> + pr_err("IMA: field too long, using template %s\n",
> + CONFIG_IMA_DEFAULT_TEMPLATE);
> + return 1;
> + }
> +
> + memcpy(field_id, str_ptr_start, len);
> + field_id[len] = '\0';
> + if (lookup_template_field(field_id) == NULL) {
> + pr_err("IMA: field '%s' not found, using template %s\n",
> + field_id, CONFIG_IMA_DEFAULT_TEMPLATE);
> + return 1;
> + }
> +
> + str_ptr_start = str_ptr_end;
> + }
> +
> + defined_templates[num_templates - 1].fmt = str;
> + ima_template = defined_templates + num_templates - 1;
> + return 1;
> +}
> +__setup("ima_template_fmt=", ima_template_fmt_setup);
> +
> static struct ima_template_desc *lookup_template_desc(const char *name)
> {
> int i;
> @@ -160,6 +207,9 @@ static int init_defined_templates(void)
> for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
> struct ima_template_desc *template = &defined_templates[i];
>
> + if (strlen(template->fmt) == 0)
> + continue;
> +
> result = template_desc_init_fields(template->fmt,
> &(template->fields),
> &(template->num_fields));
> --
> 1.8.1.4
>
--
Thanks,
Dmitry
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