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 }
191