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
23static 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	{.name = "", .fmt = ""},	/* placeholder for a custom format */
28};
29
30static struct ima_template_field supported_fields[] = {
31	{.field_id = "d", .field_init = ima_eventdigest_init,
32	 .field_show = ima_show_template_digest},
33	{.field_id = "n", .field_init = ima_eventname_init,
34	 .field_show = ima_show_template_string},
35	{.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
36	 .field_show = ima_show_template_digest_ng},
37	{.field_id = "n-ng", .field_init = ima_eventname_ng_init,
38	 .field_show = ima_show_template_string},
39	{.field_id = "sig", .field_init = ima_eventsig_init,
40	 .field_show = ima_show_template_sig},
41};
42
43static struct ima_template_desc *ima_template;
44static struct ima_template_desc *lookup_template_desc(const char *name);
45static int template_desc_init_fields(const char *template_fmt,
46				     struct ima_template_field ***fields,
47				     int *num_fields);
48
49static int __init ima_template_setup(char *str)
50{
51	struct ima_template_desc *template_desc;
52	int template_len = strlen(str);
53
54	if (ima_template)
55		return 1;
56
57	/*
58	 * Verify that a template with the supplied name exists.
59	 * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
60	 */
61	template_desc = lookup_template_desc(str);
62	if (!template_desc) {
63		pr_err("template %s not found, using %s\n",
64		       str, CONFIG_IMA_DEFAULT_TEMPLATE);
65		return 1;
66	}
67
68	/*
69	 * Verify whether the current hash algorithm is supported
70	 * by the 'ima' template.
71	 */
72	if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
73	    ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
74		pr_err("template does not support hash alg\n");
75		return 1;
76	}
77
78	ima_template = template_desc;
79	return 1;
80}
81__setup("ima_template=", ima_template_setup);
82
83static int __init ima_template_fmt_setup(char *str)
84{
85	int num_templates = ARRAY_SIZE(defined_templates);
86
87	if (ima_template)
88		return 1;
89
90	if (template_desc_init_fields(str, NULL, NULL) < 0) {
91		pr_err("format string '%s' not valid, using template %s\n",
92		       str, CONFIG_IMA_DEFAULT_TEMPLATE);
93		return 1;
94	}
95
96	defined_templates[num_templates - 1].fmt = str;
97	ima_template = defined_templates + num_templates - 1;
98	return 1;
99}
100__setup("ima_template_fmt=", ima_template_fmt_setup);
101
102static struct ima_template_desc *lookup_template_desc(const char *name)
103{
104	int i;
105
106	for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
107		if (strcmp(defined_templates[i].name, name) == 0)
108			return defined_templates + i;
109	}
110
111	return NULL;
112}
113
114static struct ima_template_field *lookup_template_field(const char *field_id)
115{
116	int i;
117
118	for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
119		if (strncmp(supported_fields[i].field_id, field_id,
120			    IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
121			return &supported_fields[i];
122	return NULL;
123}
124
125static int template_fmt_size(const char *template_fmt)
126{
127	char c;
128	int template_fmt_len = strlen(template_fmt);
129	int i = 0, j = 0;
130
131	while (i < template_fmt_len) {
132		c = template_fmt[i];
133		if (c == '|')
134			j++;
135		i++;
136	}
137
138	return j + 1;
139}
140
141static int template_desc_init_fields(const char *template_fmt,
142				     struct ima_template_field ***fields,
143				     int *num_fields)
144{
145	const char *template_fmt_ptr;
146	struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
147	int template_num_fields = template_fmt_size(template_fmt);
148	int i, len;
149
150	if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
151		pr_err("format string '%s' contains too many fields\n",
152		       template_fmt);
153		return -EINVAL;
154	}
155
156	for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
157	     i++, template_fmt_ptr += len + 1) {
158		char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
159
160		len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
161		if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
162			pr_err("Invalid field with length %d\n", len);
163			return -EINVAL;
164		}
165
166		memcpy(tmp_field_id, template_fmt_ptr, len);
167		tmp_field_id[len] = '\0';
168		found_fields[i] = lookup_template_field(tmp_field_id);
169		if (!found_fields[i]) {
170			pr_err("field '%s' not found\n", tmp_field_id);
171			return -ENOENT;
172		}
173	}
174
175	if (fields && num_fields) {
176		*fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
177		if (*fields == NULL)
178			return -ENOMEM;
179
180		memcpy(*fields, found_fields, i * sizeof(*fields));
181		*num_fields = i;
182	}
183
184	return 0;
185}
186
187struct ima_template_desc *ima_template_desc_current(void)
188{
189	if (!ima_template)
190		ima_template =
191		    lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
192	return ima_template;
193}
194
195int __init ima_init_template(void)
196{
197	struct ima_template_desc *template = ima_template_desc_current();
198	int result;
199
200	result = template_desc_init_fields(template->fmt,
201					   &(template->fields),
202					   &(template->num_fields));
203	if (result < 0)
204		pr_err("template %s init failed, result: %d\n",
205		       (strlen(template->name) ?
206		       template->name : template->fmt), result);
207
208	return result;
209}
210