--- /dev/null
+ 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. 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.
+
+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.
+
+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.
+
+
+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'.
+
+
+
+==== 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.
#define IMA_HASH_BITS 9
#define IMA_MEASURE_HTABLE_SIZE (1 << IMA_HASH_BITS)
+#define IMA_TEMPLATE_FIELD_ID_MAX_LEN 16
+#define IMA_TEMPLATE_NUM_FIELDS_MAX 15
+
/* set during initialization */
extern int ima_initialized;
extern int ima_used_chip;
extern int ima_hash_algo;
extern int ima_appraise;
+/* IMA template field data definition */
+struct ima_field_data {
+ u8 *data;
+ u32 len;
+};
+
+/* IMA template field definition */
+struct ima_template_field {
+ const char field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN];
+ int (*field_init) (struct integrity_iint_cache *iint, struct file *file,
+ const unsigned char *filename,
+ struct ima_field_data *field_data);
+ void (*field_show) (struct seq_file *m, enum ima_show_type show,
+ struct ima_field_data *field_data);
+};
+
+/* IMA template descriptor definition */
+struct ima_template_desc {
+ char *name;
+ char *fmt;
+ int num_fields;
+ struct ima_template_field **fields;
+};
+
/* IMA inode template definition */
struct ima_template_data {
u8 digest[IMA_DIGEST_SIZE]; /* sha1/md5 measurement hash */
const char *op, const char *cause);
int ima_init_crypto(void);
+int ima_init_template(void);
+
/*
* used to protect h_table and sha_table
*/
--- /dev/null
+/*
+ * Copyright (C) 2013 Politecnico di Torino, Italy
+ * TORSEC group -- http://security.polito.it
+ *
+ * Author: Roberto Sassu <roberto.sassu@polito.it>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ *
+ * File: ima_template.c
+ * Helpers to manage template descriptors.
+ */
+#include "ima.h"
+
+static struct ima_template_desc defined_templates[] = {
+};
+
+static struct ima_template_field supported_fields[] = {
+};
+
+static struct ima_template_field *ima_lookup_template_field(
+ const char *field_id)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
+ if (strncmp(supported_fields[i].field_id, field_id,
+ IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
+ return &supported_fields[i];
+ return NULL;
+}
+
+static int ima_template_fmt_size(char *template_fmt)
+{
+ char c;
+ int template_fmt_len = strlen(template_fmt);
+ int i = 0, j = 0;
+
+ while (i < template_fmt_len) {
+ c = template_fmt[i];
+ if (c == '|')
+ j++;
+ i++;
+ }
+
+ return j + 1;
+}
+
+static int template_desc_init_fields(char *template_fmt,
+ struct ima_template_field ***fields,
+ int *num_fields)
+{
+ char *c, *template_fmt_ptr = template_fmt;
+ int template_num_fields = ima_template_fmt_size(template_fmt);
+ int i, result = 0;
+
+ if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX)
+ return -EINVAL;
+
+ *fields = kzalloc(template_num_fields * sizeof(*fields), GFP_KERNEL);
+ if (*fields == NULL) {
+ result = -ENOMEM;
+ goto out;
+ }
+ for (i = 0; (c = strsep(&template_fmt_ptr, "|")) != NULL &&
+ i < template_num_fields; i++) {
+ struct ima_template_field *f = ima_lookup_template_field(c);
+
+ if (!f) {
+ result = -ENOENT;
+ goto out;
+ }
+ (*fields)[i] = f;
+ }
+ *num_fields = i;
+ return 0;
+out:
+ kfree(*fields);
+ *fields = NULL;
+ return result;
+}
+
+static int init_defined_templates(void)
+{
+ int i = 0;
+ int result = 0;
+
+ /* Init defined templates. */
+ for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
+ struct ima_template_desc *template = &defined_templates[i];
+
+ result = template_desc_init_fields(template->fmt,
+ &(template->fields),
+ &(template->num_fields));
+ if (result < 0)
+ return result;
+ }
+ return result;
+}
+
+int ima_init_template(void)
+{
+ int result;
+
+ result = init_defined_templates();
+ if (result < 0)
+ return result;
+
+ return 0;
+}
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff