integrity/ima/ima_template.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (C) 2013 Politecnico di Torino, Italy
0004  *                    TORSEC group -- https://security.polito.it
0005  *
0006  * Author: Roberto Sassu <roberto.sassu@polito.it>
0007  *
0008  * File: ima_template.c
0009  *      Helpers to manage template descriptors.
0010  */
0011
0012 #include <linux/rculist.h>
0013 #include "ima.h"
0014 #include "ima_template_lib.h"
0015
0016 enum header_fields { HDR_PCR, HDR_DIGEST, HDR_TEMPLATE_NAME,
0017              HDR_TEMPLATE_DATA, HDR__LAST };
0018
0019 static struct ima_template_desc builtin_templates[] = {
0020     {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
0021     {.name = "ima-ng", .fmt = "d-ng|n-ng"},
0022     {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
0023     {.name = "ima-ngv2", .fmt = "d-ngv2|n-ng"},
0024     {.name = "ima-sigv2", .fmt = "d-ngv2|n-ng|sig"},
0025     {.name = "ima-buf", .fmt = "d-ng|n-ng|buf"},
0026     {.name = "ima-modsig", .fmt = "d-ng|n-ng|sig|d-modsig|modsig"},
0027     {.name = "evm-sig",
0028      .fmt = "d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode"},
0029     {.name = "", .fmt = ""},    /* placeholder for a custom format */
0030 };
0031
0032 static LIST_HEAD(defined_templates);
0033 static DEFINE_SPINLOCK(template_list);
0034 static int template_setup_done;
0035
0036 static const struct ima_template_field supported_fields[] = {
0037     {.field_id = "d", .field_init = ima_eventdigest_init,
0038      .field_show = ima_show_template_digest},
0039     {.field_id = "n", .field_init = ima_eventname_init,
0040      .field_show = ima_show_template_string},
0041     {.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
0042      .field_show = ima_show_template_digest_ng},
0043     {.field_id = "d-ngv2", .field_init = ima_eventdigest_ngv2_init,
0044      .field_show = ima_show_template_digest_ngv2},
0045     {.field_id = "n-ng", .field_init = ima_eventname_ng_init,
0046      .field_show = ima_show_template_string},
0047     {.field_id = "sig", .field_init = ima_eventsig_init,
0048      .field_show = ima_show_template_sig},
0049     {.field_id = "buf", .field_init = ima_eventbuf_init,
0050      .field_show = ima_show_template_buf},
0051     {.field_id = "d-modsig", .field_init = ima_eventdigest_modsig_init,
0052      .field_show = ima_show_template_digest_ng},
0053     {.field_id = "modsig", .field_init = ima_eventmodsig_init,
0054      .field_show = ima_show_template_sig},
0055     {.field_id = "evmsig", .field_init = ima_eventevmsig_init,
0056      .field_show = ima_show_template_sig},
0057     {.field_id = "iuid", .field_init = ima_eventinodeuid_init,
0058      .field_show = ima_show_template_uint},
0059     {.field_id = "igid", .field_init = ima_eventinodegid_init,
0060      .field_show = ima_show_template_uint},
0061     {.field_id = "imode", .field_init = ima_eventinodemode_init,
0062      .field_show = ima_show_template_uint},
0063     {.field_id = "xattrnames",
0064      .field_init = ima_eventinodexattrnames_init,
0065      .field_show = ima_show_template_string},
0066     {.field_id = "xattrlengths",
0067      .field_init = ima_eventinodexattrlengths_init,
0068      .field_show = ima_show_template_sig},
0069     {.field_id = "xattrvalues",
0070      .field_init = ima_eventinodexattrvalues_init,
0071      .field_show = ima_show_template_sig},
0072 };
0073
0074 /*
0075  * Used when restoring measurements carried over from a kexec. 'd' and 'n' don't
0076  * need to be accounted for since they shouldn't be defined in the same template
0077  * description as 'd-ng' and 'n-ng' respectively.
0078  */
0079 #define MAX_TEMPLATE_NAME_LEN \
0080     sizeof("d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode")
0081
0082 static struct ima_template_desc *ima_template;
0083 static struct ima_template_desc *ima_buf_template;
0084
0085 /**
0086  * ima_template_has_modsig - Check whether template has modsig-related fields.
0087  * @ima_template: IMA template to check.
0088  *
0089  * Tells whether the given template has fields referencing a file's appended
0090  * signature.
0091  */
0092 bool ima_template_has_modsig(const struct ima_template_desc *ima_template)
0093 {
0094     int i;
0095
0096     for (i = 0; i < ima_template->num_fields; i++)
0097         if (!strcmp(ima_template->fields[i]->field_id, "modsig") ||
0098             !strcmp(ima_template->fields[i]->field_id, "d-modsig"))
0099             return true;
0100
0101     return false;
0102 }
0103
0104 static int __init ima_template_setup(char *str)
0105 {
0106     struct ima_template_desc *template_desc;
0107     int template_len = strlen(str);
0108
0109     if (template_setup_done)
0110         return 1;
0111
0112     if (!ima_template)
0113         ima_init_template_list();
0114
0115     /*
0116      * Verify that a template with the supplied name exists.
0117      * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
0118      */
0119     template_desc = lookup_template_desc(str);
0120     if (!template_desc) {
0121         pr_err("template %s not found, using %s\n",
0122                str, CONFIG_IMA_DEFAULT_TEMPLATE);
0123         return 1;
0124     }
0125
0126     /*
0127      * Verify whether the current hash algorithm is supported
0128      * by the 'ima' template.
0129      */
0130     if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
0131         ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
0132         pr_err("template does not support hash alg\n");
0133         return 1;
0134     }
0135
0136     ima_template = template_desc;
0137     template_setup_done = 1;
0138     return 1;
0139 }
0140 __setup("ima_template=", ima_template_setup);
0141
0142 static int __init ima_template_fmt_setup(char *str)
0143 {
0144     int num_templates = ARRAY_SIZE(builtin_templates);
0145
0146     if (template_setup_done)
0147         return 1;
0148
0149     if (template_desc_init_fields(str, NULL, NULL) < 0) {
0150         pr_err("format string '%s' not valid, using template %s\n",
0151                str, CONFIG_IMA_DEFAULT_TEMPLATE);
0152         return 1;
0153     }
0154
0155     builtin_templates[num_templates - 1].fmt = str;
0156     ima_template = builtin_templates + num_templates - 1;
0157     template_setup_done = 1;
0158
0159     return 1;
0160 }
0161 __setup("ima_template_fmt=", ima_template_fmt_setup);
0162
0163 struct ima_template_desc *lookup_template_desc(const char *name)
0164 {
0165     struct ima_template_desc *template_desc;
0166     int found = 0;
0167
0168     rcu_read_lock();
0169     list_for_each_entry_rcu(template_desc, &defined_templates, list) {
0170         if ((strcmp(template_desc->name, name) == 0) ||
0171             (strcmp(template_desc->fmt, name) == 0)) {
0172             found = 1;
0173             break;
0174         }
0175     }
0176     rcu_read_unlock();
0177     return found ? template_desc : NULL;
0178 }
0179
0180 static const struct ima_template_field *
0181 lookup_template_field(const char *field_id)
0182 {
0183     int i;
0184
0185     for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
0186         if (strncmp(supported_fields[i].field_id, field_id,
0187                 IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
0188             return &supported_fields[i];
0189     return NULL;
0190 }
0191
0192 static int template_fmt_size(const char *template_fmt)
0193 {
0194     char c;
0195     int template_fmt_len = strlen(template_fmt);
0196     int i = 0, j = 0;
0197
0198     while (i < template_fmt_len) {
0199         c = template_fmt[i];
0200         if (c == '|')
0201             j++;
0202         i++;
0203     }
0204
0205     return j + 1;
0206 }
0207
0208 int template_desc_init_fields(const char *template_fmt,
0209                   const struct ima_template_field ***fields,
0210                   int *num_fields)
0211 {
0212     const char *template_fmt_ptr;
0213     const struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
0214     int template_num_fields;
0215     int i, len;
0216
0217     if (num_fields && *num_fields > 0) /* already initialized? */
0218         return 0;
0219
0220     template_num_fields = template_fmt_size(template_fmt);
0221
0222     if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
0223         pr_err("format string '%s' contains too many fields\n",
0224                template_fmt);
0225         return -EINVAL;
0226     }
0227
0228     for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
0229          i++, template_fmt_ptr += len + 1) {
0230         char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
0231
0232         len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
0233         if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
0234             pr_err("Invalid field with length %d\n", len);
0235             return -EINVAL;
0236         }
0237
0238         memcpy(tmp_field_id, template_fmt_ptr, len);
0239         tmp_field_id[len] = '\0';
0240         found_fields[i] = lookup_template_field(tmp_field_id);
0241         if (!found_fields[i]) {
0242             pr_err("field '%s' not found\n", tmp_field_id);
0243             return -ENOENT;
0244         }
0245     }
0246
0247     if (fields && num_fields) {
0248         *fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
0249         if (*fields == NULL)
0250             return -ENOMEM;
0251
0252         memcpy(*fields, found_fields, i * sizeof(*fields));
0253         *num_fields = i;
0254     }
0255
0256     return 0;
0257 }
0258
0259 void ima_init_template_list(void)
0260 {
0261     int i;
0262
0263     if (!list_empty(&defined_templates))
0264         return;
0265
0266     spin_lock(&template_list);
0267     for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
0268         list_add_tail_rcu(&builtin_templates[i].list,
0269                   &defined_templates);
0270     }
0271     spin_unlock(&template_list);
0272 }
0273
0274 struct ima_template_desc *ima_template_desc_current(void)
0275 {
0276     if (!ima_template) {
0277         ima_init_template_list();
0278         ima_template =
0279             lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
0280     }
0281     return ima_template;
0282 }
0283
0284 struct ima_template_desc *ima_template_desc_buf(void)
0285 {
0286     if (!ima_buf_template) {
0287         ima_init_template_list();
0288         ima_buf_template = lookup_template_desc("ima-buf");
0289     }
0290     return ima_buf_template;
0291 }
0292
0293 int __init ima_init_template(void)
0294 {
0295     struct ima_template_desc *template = ima_template_desc_current();
0296     int result;
0297
0298     result = template_desc_init_fields(template->fmt,
0299                        &(template->fields),
0300                        &(template->num_fields));
0301     if (result < 0) {
0302         pr_err("template %s init failed, result: %d\n",
0303                (strlen(template->name) ?
0304                template->name : template->fmt), result);
0305         return result;
0306     }
0307
0308     template = ima_template_desc_buf();
0309     if (!template) {
0310         pr_err("Failed to get ima-buf template\n");
0311         return -EINVAL;
0312     }
0313
0314     result = template_desc_init_fields(template->fmt,
0315                        &(template->fields),
0316                        &(template->num_fields));
0317     if (result < 0)
0318         pr_err("template %s init failed, result: %d\n",
0319                (strlen(template->name) ?
0320                template->name : template->fmt), result);
0321
0322     return result;
0323 }
0324
0325 static struct ima_template_desc *restore_template_fmt(char *template_name)
0326 {
0327     struct ima_template_desc *template_desc = NULL;
0328     int ret;
0329
0330     ret = template_desc_init_fields(template_name, NULL, NULL);
0331     if (ret < 0) {
0332         pr_err("attempting to initialize the template \"%s\" failed\n",
0333             template_name);
0334         goto out;
0335     }
0336
0337     template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
0338     if (!template_desc)
0339         goto out;
0340
0341     template_desc->name = "";
0342     template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
0343     if (!template_desc->fmt)
0344         goto out;
0345
0346     spin_lock(&template_list);
0347     list_add_tail_rcu(&template_desc->list, &defined_templates);
0348     spin_unlock(&template_list);
0349 out:
0350     return template_desc;
0351 }
0352
0353 static int ima_restore_template_data(struct ima_template_desc *template_desc,
0354                      void *template_data,
0355                      int template_data_size,
0356                      struct ima_template_entry **entry)
0357 {
0358     struct tpm_digest *digests;
0359     int ret = 0;
0360     int i;
0361
0362     *entry = kzalloc(struct_size(*entry, template_data,
0363                      template_desc->num_fields), GFP_NOFS);
0364     if (!*entry)
0365         return -ENOMEM;
0366
0367     digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
0368               sizeof(*digests), GFP_NOFS);
0369     if (!digests) {
0370         kfree(*entry);
0371         return -ENOMEM;
0372     }
0373
0374     (*entry)->digests = digests;
0375
0376     ret = ima_parse_buf(template_data, template_data + template_data_size,
0377                 NULL, template_desc->num_fields,
0378                 (*entry)->template_data, NULL, NULL,
0379                 ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
0380     if (ret < 0) {
0381         kfree((*entry)->digests);
0382         kfree(*entry);
0383         return ret;
0384     }
0385
0386     (*entry)->template_desc = template_desc;
0387     for (i = 0; i < template_desc->num_fields; i++) {
0388         struct ima_field_data *field_data = &(*entry)->template_data[i];
0389         u8 *data = field_data->data;
0390
0391         (*entry)->template_data[i].data =
0392             kzalloc(field_data->len + 1, GFP_KERNEL);
0393         if (!(*entry)->template_data[i].data) {
0394             ret = -ENOMEM;
0395             break;
0396         }
0397         memcpy((*entry)->template_data[i].data, data, field_data->len);
0398         (*entry)->template_data_len += sizeof(field_data->len);
0399         (*entry)->template_data_len += field_data->len;
0400     }
0401
0402     if (ret < 0) {
0403         ima_free_template_entry(*entry);
0404         *entry = NULL;
0405     }
0406
0407     return ret;
0408 }
0409
0410 /* Restore the serialized binary measurement list without extending PCRs. */
0411 int ima_restore_measurement_list(loff_t size, void *buf)
0412 {
0413     char template_name[MAX_TEMPLATE_NAME_LEN];
0414     unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
0415
0416     struct ima_kexec_hdr *khdr = buf;
0417     struct ima_field_data hdr[HDR__LAST] = {
0418         [HDR_PCR] = {.len = sizeof(u32)},
0419         [HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
0420     };
0421
0422     void *bufp = buf + sizeof(*khdr);
0423     void *bufendp;
0424     struct ima_template_entry *entry;
0425     struct ima_template_desc *template_desc;
0426     DECLARE_BITMAP(hdr_mask, HDR__LAST);
0427     unsigned long count = 0;
0428     int ret = 0;
0429
0430     if (!buf || size < sizeof(*khdr))
0431         return 0;
0432
0433     if (ima_canonical_fmt) {
0434         khdr->version = le16_to_cpu((__force __le16)khdr->version);
0435         khdr->count = le64_to_cpu((__force __le64)khdr->count);
0436         khdr->buffer_size = le64_to_cpu((__force __le64)khdr->buffer_size);
0437     }
0438
0439     if (khdr->version != 1) {
0440         pr_err("attempting to restore a incompatible measurement list");
0441         return -EINVAL;
0442     }
0443
0444     if (khdr->count > ULONG_MAX - 1) {
0445         pr_err("attempting to restore too many measurements");
0446         return -EINVAL;
0447     }
0448
0449     bitmap_zero(hdr_mask, HDR__LAST);
0450     bitmap_set(hdr_mask, HDR_PCR, 1);
0451     bitmap_set(hdr_mask, HDR_DIGEST, 1);
0452
0453     /*
0454      * ima kexec buffer prefix: version, buffer size, count
0455      * v1 format: pcr, digest, template-name-len, template-name,
0456      *        template-data-size, template-data
0457      */
0458     bufendp = buf + khdr->buffer_size;
0459     while ((bufp < bufendp) && (count++ < khdr->count)) {
0460         int enforce_mask = ENFORCE_FIELDS;
0461
0462         enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
0463         ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
0464                     hdr_mask, enforce_mask, "entry header");
0465         if (ret < 0)
0466             break;
0467
0468         if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
0469             pr_err("attempting to restore a template name that is too long\n");
0470             ret = -EINVAL;
0471             break;
0472         }
0473
0474         /* template name is not null terminated */
0475         memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
0476                hdr[HDR_TEMPLATE_NAME].len);
0477         template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
0478
0479         if (strcmp(template_name, "ima") == 0) {
0480             pr_err("attempting to restore an unsupported template \"%s\" failed\n",
0481                    template_name);
0482             ret = -EINVAL;
0483             break;
0484         }
0485
0486         template_desc = lookup_template_desc(template_name);
0487         if (!template_desc) {
0488             template_desc = restore_template_fmt(template_name);
0489             if (!template_desc)
0490                 break;
0491         }
0492
0493         /*
0494          * Only the running system's template format is initialized
0495          * on boot.  As needed, initialize the other template formats.
0496          */
0497         ret = template_desc_init_fields(template_desc->fmt,
0498                         &(template_desc->fields),
0499                         &(template_desc->num_fields));
0500         if (ret < 0) {
0501             pr_err("attempting to restore the template fmt \"%s\" failed\n",
0502                    template_desc->fmt);
0503             ret = -EINVAL;
0504             break;
0505         }
0506
0507         ret = ima_restore_template_data(template_desc,
0508                         hdr[HDR_TEMPLATE_DATA].data,
0509                         hdr[HDR_TEMPLATE_DATA].len,
0510                         &entry);
0511         if (ret < 0)
0512             break;
0513
0514         if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
0515             ret = ima_calc_field_array_hash(
0516                         &entry->template_data[0],
0517                         entry);
0518             if (ret < 0) {
0519                 pr_err("cannot calculate template digest\n");
0520                 ret = -EINVAL;
0521                 break;
0522             }
0523         }
0524
0525         entry->pcr = !ima_canonical_fmt ? *(u32 *)(hdr[HDR_PCR].data) :
0526                  le32_to_cpu(*(__le32 *)(hdr[HDR_PCR].data));
0527         ret = ima_restore_measurement_entry(entry);
0528         if (ret < 0)
0529             break;
0530
0531     }
0532     return ret;
0533 }