Re: [PATCH-v2 3/3] ima: added support for new kernel cmdline parameterima_template_fmt
From: Roberto Sassu
Date: Sat Dec 07 2013 - 04:58:30 EST
On 12/06/2013 08:36 PM, Mimi Zohar wrote:
On Fri, 2013-12-06 at 13:57 +0100, Roberto Sassu 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.
Changelog:
- simplified code of ima_template_fmt_setup()
(Roberto Sassu, suggested by Mimi Zohar)
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxx>
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 4 +++
Documentation/security/IMA-templates.txt | 29 +++++++++++----------
security/integrity/ima/ima_template.c | 43 ++++++++++++++++++++++++++++++++
3 files changed, 61 insertions(+), 15 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 50680a5..bb45dbc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1208,6 +1208,10 @@ 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 a4e102d..7d065f0 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,
@@ -86,4 +83,6 @@ 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 a001477..11adf4a 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 +75,41 @@ 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 = str;
+
+ if (ima_template)
+ return 1;
+
+ while (str_ptr != NULL) {
+ char field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN];
+ int len = strcspn(str_ptr, "|");
+
+ 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, 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 = (str_ptr[len] == '|') ? str_ptr + len + 1 : NULL;
Personally, I think it would be cleaner to use a 'for' loop. Something
like: for (bufp = buf; bufp < bufend; bufp += len + 1)
Hi Mimi
this solution will not work because it does not properly
handle a string like 'validfield|'. Indeed, at the second
iteration, you already reached the end of the string and
exit without detecting a field identifier of length zero.
Thanks
Roberto Sassu
thanks,
Mimi
+ }
+
+ 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;
@@ -162,6 +202,9 @@ 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));
--
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