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![Lakshmi Ramasubramanian](/assets/img/avatar_default.png)
The default IMA template used for all policy rules is the value set for CONFIG_IMA_DEFAULT_TEMPLATE if the policy rule does not specify a template. The default IMA template for buffer measurements should be 'ima-buf' - so that the measured buffer is correctly included in the IMA measurement log entry. With the default template format, buffer measurements are added to the measurement list, but do not include the buffer data, making it difficult, if not impossible, to validate. Including 'ima-buf' template records in the measurement list by default, should not impact existing attestation servers without 'ima-buf' template support. Initialize a global 'ima-buf' template and select that template, by default, for buffer measurements. Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
505 lines
13 KiB
C
505 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2013 Politecnico di Torino, Italy
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* TORSEC group -- https://security.polito.it
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*
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* Author: Roberto Sassu <roberto.sassu@polito.it>
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*
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* File: ima_template.c
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* Helpers to manage template descriptors.
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*/
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#include <linux/rculist.h>
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#include "ima.h"
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#include "ima_template_lib.h"
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enum header_fields { HDR_PCR, HDR_DIGEST, HDR_TEMPLATE_NAME,
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HDR_TEMPLATE_DATA, HDR__LAST };
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static struct ima_template_desc builtin_templates[] = {
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{.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
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{.name = "ima-ng", .fmt = "d-ng|n-ng"},
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{.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
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{.name = "ima-buf", .fmt = "d-ng|n-ng|buf"},
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{.name = "ima-modsig", .fmt = "d-ng|n-ng|sig|d-modsig|modsig"},
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{.name = "", .fmt = ""}, /* placeholder for a custom format */
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};
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static LIST_HEAD(defined_templates);
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static DEFINE_SPINLOCK(template_list);
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static const struct ima_template_field supported_fields[] = {
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{.field_id = "d", .field_init = ima_eventdigest_init,
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.field_show = ima_show_template_digest},
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{.field_id = "n", .field_init = ima_eventname_init,
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.field_show = ima_show_template_string},
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{.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
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.field_show = ima_show_template_digest_ng},
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{.field_id = "n-ng", .field_init = ima_eventname_ng_init,
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.field_show = ima_show_template_string},
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{.field_id = "sig", .field_init = ima_eventsig_init,
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.field_show = ima_show_template_sig},
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{.field_id = "buf", .field_init = ima_eventbuf_init,
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.field_show = ima_show_template_buf},
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{.field_id = "d-modsig", .field_init = ima_eventdigest_modsig_init,
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.field_show = ima_show_template_digest_ng},
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{.field_id = "modsig", .field_init = ima_eventmodsig_init,
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.field_show = ima_show_template_sig},
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};
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/*
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* Used when restoring measurements carried over from a kexec. 'd' and 'n' don't
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* need to be accounted for since they shouldn't be defined in the same template
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* description as 'd-ng' and 'n-ng' respectively.
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*/
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#define MAX_TEMPLATE_NAME_LEN sizeof("d-ng|n-ng|sig|buf|d-modisg|modsig")
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static struct ima_template_desc *ima_template;
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static struct ima_template_desc *ima_buf_template;
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/**
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* ima_template_has_modsig - Check whether template has modsig-related fields.
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* @ima_template: IMA template to check.
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*
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* Tells whether the given template has fields referencing a file's appended
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* signature.
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*/
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bool ima_template_has_modsig(const struct ima_template_desc *ima_template)
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{
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int i;
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for (i = 0; i < ima_template->num_fields; i++)
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if (!strcmp(ima_template->fields[i]->field_id, "modsig") ||
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!strcmp(ima_template->fields[i]->field_id, "d-modsig"))
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return true;
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return false;
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}
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static int __init ima_template_setup(char *str)
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{
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struct ima_template_desc *template_desc;
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int template_len = strlen(str);
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if (ima_template)
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return 1;
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ima_init_template_list();
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/*
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* Verify that a template with the supplied name exists.
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* If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
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*/
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template_desc = lookup_template_desc(str);
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if (!template_desc) {
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pr_err("template %s not found, using %s\n",
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str, CONFIG_IMA_DEFAULT_TEMPLATE);
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return 1;
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}
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/*
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* Verify whether the current hash algorithm is supported
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* by the 'ima' template.
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*/
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if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
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ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
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pr_err("template does not support hash alg\n");
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return 1;
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}
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ima_template = template_desc;
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return 1;
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}
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__setup("ima_template=", ima_template_setup);
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static int __init ima_template_fmt_setup(char *str)
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{
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int num_templates = ARRAY_SIZE(builtin_templates);
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if (ima_template)
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return 1;
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if (template_desc_init_fields(str, NULL, NULL) < 0) {
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pr_err("format string '%s' not valid, using template %s\n",
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str, CONFIG_IMA_DEFAULT_TEMPLATE);
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return 1;
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}
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builtin_templates[num_templates - 1].fmt = str;
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ima_template = builtin_templates + num_templates - 1;
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return 1;
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}
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__setup("ima_template_fmt=", ima_template_fmt_setup);
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struct ima_template_desc *lookup_template_desc(const char *name)
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{
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struct ima_template_desc *template_desc;
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int found = 0;
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rcu_read_lock();
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list_for_each_entry_rcu(template_desc, &defined_templates, list) {
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if ((strcmp(template_desc->name, name) == 0) ||
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(strcmp(template_desc->fmt, name) == 0)) {
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found = 1;
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break;
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}
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}
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rcu_read_unlock();
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return found ? template_desc : NULL;
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}
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static const struct ima_template_field *
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lookup_template_field(const char *field_id)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
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if (strncmp(supported_fields[i].field_id, field_id,
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IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
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return &supported_fields[i];
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return NULL;
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}
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static int template_fmt_size(const char *template_fmt)
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{
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char c;
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int template_fmt_len = strlen(template_fmt);
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int i = 0, j = 0;
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while (i < template_fmt_len) {
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c = template_fmt[i];
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if (c == '|')
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j++;
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i++;
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}
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return j + 1;
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}
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int template_desc_init_fields(const char *template_fmt,
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const struct ima_template_field ***fields,
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int *num_fields)
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{
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const char *template_fmt_ptr;
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const struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
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int template_num_fields;
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int i, len;
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if (num_fields && *num_fields > 0) /* already initialized? */
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return 0;
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template_num_fields = template_fmt_size(template_fmt);
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if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
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pr_err("format string '%s' contains too many fields\n",
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template_fmt);
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return -EINVAL;
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}
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for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
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i++, template_fmt_ptr += len + 1) {
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char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
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len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
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if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
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pr_err("Invalid field with length %d\n", len);
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return -EINVAL;
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}
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memcpy(tmp_field_id, template_fmt_ptr, len);
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tmp_field_id[len] = '\0';
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found_fields[i] = lookup_template_field(tmp_field_id);
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if (!found_fields[i]) {
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pr_err("field '%s' not found\n", tmp_field_id);
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return -ENOENT;
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}
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}
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if (fields && num_fields) {
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*fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
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if (*fields == NULL)
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return -ENOMEM;
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memcpy(*fields, found_fields, i * sizeof(*fields));
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*num_fields = i;
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}
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return 0;
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}
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void ima_init_template_list(void)
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{
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int i;
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if (!list_empty(&defined_templates))
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return;
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spin_lock(&template_list);
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for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
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list_add_tail_rcu(&builtin_templates[i].list,
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&defined_templates);
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}
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spin_unlock(&template_list);
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}
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struct ima_template_desc *ima_template_desc_current(void)
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{
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if (!ima_template) {
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ima_init_template_list();
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ima_template =
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lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
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}
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return ima_template;
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}
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struct ima_template_desc *ima_template_desc_buf(void)
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{
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if (!ima_buf_template) {
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ima_init_template_list();
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ima_buf_template = lookup_template_desc("ima-buf");
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}
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return ima_buf_template;
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}
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int __init ima_init_template(void)
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{
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struct ima_template_desc *template = ima_template_desc_current();
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int result;
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result = template_desc_init_fields(template->fmt,
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&(template->fields),
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&(template->num_fields));
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if (result < 0) {
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pr_err("template %s init failed, result: %d\n",
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(strlen(template->name) ?
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template->name : template->fmt), result);
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return result;
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}
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template = ima_template_desc_buf();
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if (!template) {
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pr_err("Failed to get ima-buf template\n");
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return -EINVAL;
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}
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result = template_desc_init_fields(template->fmt,
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&(template->fields),
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&(template->num_fields));
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if (result < 0)
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pr_err("template %s init failed, result: %d\n",
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(strlen(template->name) ?
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template->name : template->fmt), result);
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return result;
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}
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static struct ima_template_desc *restore_template_fmt(char *template_name)
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{
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struct ima_template_desc *template_desc = NULL;
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int ret;
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ret = template_desc_init_fields(template_name, NULL, NULL);
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if (ret < 0) {
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pr_err("attempting to initialize the template \"%s\" failed\n",
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template_name);
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goto out;
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}
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template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
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if (!template_desc)
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goto out;
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template_desc->name = "";
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template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
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if (!template_desc->fmt)
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goto out;
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spin_lock(&template_list);
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list_add_tail_rcu(&template_desc->list, &defined_templates);
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spin_unlock(&template_list);
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out:
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return template_desc;
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}
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static int ima_restore_template_data(struct ima_template_desc *template_desc,
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void *template_data,
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int template_data_size,
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struct ima_template_entry **entry)
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{
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struct tpm_digest *digests;
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int ret = 0;
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int i;
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*entry = kzalloc(struct_size(*entry, template_data,
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template_desc->num_fields), GFP_NOFS);
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if (!*entry)
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return -ENOMEM;
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digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
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sizeof(*digests), GFP_NOFS);
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if (!digests) {
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kfree(*entry);
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return -ENOMEM;
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}
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(*entry)->digests = digests;
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ret = ima_parse_buf(template_data, template_data + template_data_size,
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NULL, template_desc->num_fields,
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(*entry)->template_data, NULL, NULL,
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ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
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if (ret < 0) {
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kfree((*entry)->digests);
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kfree(*entry);
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return ret;
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}
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(*entry)->template_desc = template_desc;
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for (i = 0; i < template_desc->num_fields; i++) {
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struct ima_field_data *field_data = &(*entry)->template_data[i];
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u8 *data = field_data->data;
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(*entry)->template_data[i].data =
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kzalloc(field_data->len + 1, GFP_KERNEL);
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if (!(*entry)->template_data[i].data) {
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ret = -ENOMEM;
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break;
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}
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memcpy((*entry)->template_data[i].data, data, field_data->len);
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(*entry)->template_data_len += sizeof(field_data->len);
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(*entry)->template_data_len += field_data->len;
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}
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if (ret < 0) {
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ima_free_template_entry(*entry);
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*entry = NULL;
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}
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return ret;
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}
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/* Restore the serialized binary measurement list without extending PCRs. */
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int ima_restore_measurement_list(loff_t size, void *buf)
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{
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char template_name[MAX_TEMPLATE_NAME_LEN];
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unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
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struct ima_kexec_hdr *khdr = buf;
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struct ima_field_data hdr[HDR__LAST] = {
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[HDR_PCR] = {.len = sizeof(u32)},
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[HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
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};
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void *bufp = buf + sizeof(*khdr);
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void *bufendp;
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struct ima_template_entry *entry;
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struct ima_template_desc *template_desc;
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DECLARE_BITMAP(hdr_mask, HDR__LAST);
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unsigned long count = 0;
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int ret = 0;
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if (!buf || size < sizeof(*khdr))
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return 0;
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if (ima_canonical_fmt) {
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khdr->version = le16_to_cpu(khdr->version);
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khdr->count = le64_to_cpu(khdr->count);
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khdr->buffer_size = le64_to_cpu(khdr->buffer_size);
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}
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if (khdr->version != 1) {
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pr_err("attempting to restore a incompatible measurement list");
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return -EINVAL;
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}
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if (khdr->count > ULONG_MAX - 1) {
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pr_err("attempting to restore too many measurements");
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return -EINVAL;
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}
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bitmap_zero(hdr_mask, HDR__LAST);
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bitmap_set(hdr_mask, HDR_PCR, 1);
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bitmap_set(hdr_mask, HDR_DIGEST, 1);
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/*
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* ima kexec buffer prefix: version, buffer size, count
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* v1 format: pcr, digest, template-name-len, template-name,
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* template-data-size, template-data
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*/
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bufendp = buf + khdr->buffer_size;
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while ((bufp < bufendp) && (count++ < khdr->count)) {
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int enforce_mask = ENFORCE_FIELDS;
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enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
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ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
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hdr_mask, enforce_mask, "entry header");
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if (ret < 0)
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break;
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if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
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pr_err("attempting to restore a template name that is too long\n");
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ret = -EINVAL;
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break;
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}
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/* template name is not null terminated */
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memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
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hdr[HDR_TEMPLATE_NAME].len);
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template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
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if (strcmp(template_name, "ima") == 0) {
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pr_err("attempting to restore an unsupported template \"%s\" failed\n",
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template_name);
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ret = -EINVAL;
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break;
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}
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template_desc = lookup_template_desc(template_name);
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if (!template_desc) {
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template_desc = restore_template_fmt(template_name);
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if (!template_desc)
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break;
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}
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/*
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* Only the running system's template format is initialized
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* on boot. As needed, initialize the other template formats.
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*/
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ret = template_desc_init_fields(template_desc->fmt,
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&(template_desc->fields),
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&(template_desc->num_fields));
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if (ret < 0) {
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pr_err("attempting to restore the template fmt \"%s\" failed\n",
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template_desc->fmt);
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ret = -EINVAL;
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break;
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}
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ret = ima_restore_template_data(template_desc,
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hdr[HDR_TEMPLATE_DATA].data,
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hdr[HDR_TEMPLATE_DATA].len,
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&entry);
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if (ret < 0)
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break;
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if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
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ret = ima_calc_field_array_hash(
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&entry->template_data[0],
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entry);
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if (ret < 0) {
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pr_err("cannot calculate template digest\n");
|
|
ret = -EINVAL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
entry->pcr = !ima_canonical_fmt ? *(hdr[HDR_PCR].data) :
|
|
le32_to_cpu(*(hdr[HDR_PCR].data));
|
|
ret = ima_restore_measurement_entry(entry);
|
|
if (ret < 0)
|
|
break;
|
|
|
|
}
|
|
return ret;
|
|
}
|