security/integrity/ima/ima_template.c

   1 /*
   2  * Copyright (C) 2013 Politecnico di Torino, Italy
   3  *                    TORSEC group -- http://security.polito.it
   4  *
   5  * Author: Roberto Sassu <roberto.sassu@polito.it>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation, version 2 of the
  10  * License.
  11  *
  12  * File: ima_template.c
  13  *      Helpers to manage template descriptors.
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <crypto/hash_info.h>
  19
  20 #include "ima.h"
  21 #include "ima_template_lib.h"
  22
  23 static struct ima_template_desc defined_templates[] = {
  24         {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
  25         {.name = "ima-ng", .fmt = "d-ng|n-ng"},
  26         {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
  27 };
  28
  29 static struct ima_template_field supported_fields[] = {
  30         {.field_id = "d", .field_init = ima_eventdigest_init,
  31          .field_show = ima_show_template_digest},
  32         {.field_id = "n", .field_init = ima_eventname_init,
  33          .field_show = ima_show_template_string},
  34         {.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
  35          .field_show = ima_show_template_digest_ng},
  36         {.field_id = "n-ng", .field_init = ima_eventname_ng_init,
  37          .field_show = ima_show_template_string},
  38         {.field_id = "sig", .field_init = ima_eventsig_init,
  39          .field_show = ima_show_template_sig},
  40 };
  41
  42 static struct ima_template_desc *ima_template;
  43 static struct ima_template_desc *lookup_template_desc(const char *name);
  44
  45 static int __init ima_template_setup(char *str)
  46 {
  47         struct ima_template_desc *template_desc;
  48         int template_len = strlen(str);
  49
  50         /*
  51          * Verify that a template with the supplied name exists.
  52          * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
  53          */
  54         template_desc = lookup_template_desc(str);
  55         if (!template_desc)
  56                 return 1;
  57
  58         /*
  59          * Verify whether the current hash algorithm is supported
  60          * by the 'ima' template.
  61          */
  62         if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
  63             ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
  64                 pr_err("template does not support hash alg\n");
  65                 return 1;
  66         }
  67
  68         ima_template = template_desc;
  69         return 1;
  70 }
  71 __setup("ima_template=", ima_template_setup);
  72
  73 static struct ima_template_desc *lookup_template_desc(const char *name)
  74 {
  75         int i;
  76
  77         for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
  78                 if (strcmp(defined_templates[i].name, name) == 0)
  79                         return defined_templates + i;
  80         }
  81
  82         return NULL;
  83 }
  84
  85 static struct ima_template_field *lookup_template_field(const char *field_id)
  86 {
  87         int i;
  88
  89         for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
  90                 if (strncmp(supported_fields[i].field_id, field_id,
  91                             IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
  92                         return &supported_fields[i];
  93         return NULL;
  94 }
  95
  96 static int template_fmt_size(const char *template_fmt)
  97 {
  98         char c;
  99         int template_fmt_len = strlen(template_fmt);
 100         int i = 0, j = 0;
 101
 102         while (i < template_fmt_len) {
 103                 c = template_fmt[i];
 104                 if (c == '|')
 105                         j++;
 106                 i++;
 107         }
 108
 109         return j + 1;
 110 }
 111
 112 static int template_desc_init_fields(const char *template_fmt,
 113                                      struct ima_template_field ***fields,
 114                                      int *num_fields)
 115 {
 116         char *c, *template_fmt_copy, *template_fmt_ptr;
 117         int template_num_fields = template_fmt_size(template_fmt);
 118         int i, result = 0;
 119
 120         if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX)
 121                 return -EINVAL;
 122
 123         /* copying is needed as strsep() modifies the original buffer */
 124         template_fmt_copy = kstrdup(template_fmt, GFP_KERNEL);
 125         if (template_fmt_copy == NULL)
 126                 return -ENOMEM;
 127
 128         *fields = kzalloc(template_num_fields * sizeof(*fields), GFP_KERNEL);
 129         if (*fields == NULL) {
 130                 result = -ENOMEM;
 131                 goto out;
 132         }
 133
 134         template_fmt_ptr = template_fmt_copy;
 135         for (i = 0; (c = strsep(&template_fmt_ptr, "|")) != NULL &&
 136              i < template_num_fields; i++) {
 137                 struct ima_template_field *f = lookup_template_field(c);
 138
 139                 if (!f) {
 140                         result = -ENOENT;
 141                         goto out;
 142                 }
 143                 (*fields)[i] = f;
 144         }
 145         *num_fields = i;
 146 out:
 147         if (result < 0) {
 148                 kfree(*fields);
 149                 *fields = NULL;
 150         }
 151         kfree(template_fmt_copy);
 152         return result;
 153 }
 154
 155 static int init_defined_templates(void)
 156 {
 157         int i = 0;
 158         int result = 0;
 159
 160         /* Init defined templates. */
 161         for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
 162                 struct ima_template_desc *template = &defined_templates[i];
 163
 164                 result = template_desc_init_fields(template->fmt,
 165                                                    &(template->fields),
 166                                                    &(template->num_fields));
 167                 if (result < 0)
 168                         return result;
 169         }
 170         return result;
 171 }
 172
 173 struct ima_template_desc *ima_template_desc_current(void)
 174 {
 175         if (!ima_template)
 176                 ima_template =
 177                     lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
 178         return ima_template;
 179 }
 180
 181 int ima_init_template(void)
 182 {
 183         int result;
 184
 185         result = init_defined_templates();
 186         if (result < 0)
 187                 return result;
 188
 189         return 0;
 190 }