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1 | /* |
2 | * Copyright (C) 2008 IBM Corporation | |
3 | * | |
4 | * Author: Mimi Zohar <zohar@us.ibm.com> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public License as | |
8 | * published by the Free Software Foundation, version 2 of the | |
9 | * License. | |
10 | * | |
11 | * File: ima_api.c | |
2fe5d6de MZ |
12 | * Implements must_appraise_or_measure, collect_measurement, |
13 | * appraise_measurement, store_measurement and store_template. | |
3323eec9 MZ |
14 | */ |
15 | #include <linux/module.h> | |
5a0e3ad6 | 16 | #include <linux/slab.h> |
2fe5d6de MZ |
17 | #include <linux/file.h> |
18 | #include <linux/fs.h> | |
19 | #include <linux/xattr.h> | |
20 | #include <linux/evm.h> | |
3323eec9 | 21 | #include "ima.h" |
2fe5d6de | 22 | |
523979ad | 23 | static const char *IMA_TEMPLATE_NAME = "ima"; |
3323eec9 MZ |
24 | |
25 | /* | |
26 | * ima_store_template - store ima template measurements | |
27 | * | |
28 | * Calculate the hash of a template entry, add the template entry | |
29 | * to an ordered list of measurement entries maintained inside the kernel, | |
30 | * and also update the aggregate integrity value (maintained inside the | |
31 | * configured TPM PCR) over the hashes of the current list of measurement | |
32 | * entries. | |
33 | * | |
34 | * Applications retrieve the current kernel-held measurement list through | |
35 | * the securityfs entries in /sys/kernel/security/ima. The signed aggregate | |
36 | * TPM PCR (called quote) can be retrieved using a TPM user space library | |
37 | * and is used to validate the measurement list. | |
38 | * | |
39 | * Returns 0 on success, error code otherwise | |
40 | */ | |
41 | int ima_store_template(struct ima_template_entry *entry, | |
42 | int violation, struct inode *inode) | |
43 | { | |
44 | const char *op = "add_template_measure"; | |
45 | const char *audit_cause = "hashing_error"; | |
46 | int result; | |
47 | ||
48 | memset(entry->digest, 0, sizeof(entry->digest)); | |
49 | entry->template_name = IMA_TEMPLATE_NAME; | |
50 | entry->template_len = sizeof(entry->template); | |
51 | ||
52 | if (!violation) { | |
53 | result = ima_calc_template_hash(entry->template_len, | |
54 | &entry->template, | |
55 | entry->digest); | |
56 | if (result < 0) { | |
57 | integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, | |
58 | entry->template_name, op, | |
59 | audit_cause, result, 0); | |
60 | return result; | |
61 | } | |
62 | } | |
63 | result = ima_add_template_entry(entry, violation, op, inode); | |
64 | return result; | |
65 | } | |
66 | ||
67 | /* | |
68 | * ima_add_violation - add violation to measurement list. | |
69 | * | |
70 | * Violations are flagged in the measurement list with zero hash values. | |
71 | * By extending the PCR with 0xFF's instead of with zeroes, the PCR | |
72 | * value is invalidated. | |
73 | */ | |
74 | void ima_add_violation(struct inode *inode, const unsigned char *filename, | |
75 | const char *op, const char *cause) | |
76 | { | |
77 | struct ima_template_entry *entry; | |
78 | int violation = 1; | |
79 | int result; | |
80 | ||
81 | /* can overflow, only indicator */ | |
82 | atomic_long_inc(&ima_htable.violations); | |
83 | ||
84 | entry = kmalloc(sizeof(*entry), GFP_KERNEL); | |
85 | if (!entry) { | |
86 | result = -ENOMEM; | |
87 | goto err_out; | |
88 | } | |
89 | memset(&entry->template, 0, sizeof(entry->template)); | |
90 | strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX); | |
91 | result = ima_store_template(entry, violation, inode); | |
92 | if (result < 0) | |
93 | kfree(entry); | |
94 | err_out: | |
95 | integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, | |
96 | op, cause, result, 0); | |
97 | } | |
98 | ||
99 | /** | |
d9d300cd | 100 | * ima_get_action - appraise & measure decision based on policy. |
3323eec9 MZ |
101 | * @inode: pointer to inode to measure |
102 | * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE) | |
16cac49f | 103 | * @function: calling function (FILE_CHECK, BPRM_CHECK, MMAP_CHECK, MODULE_CHECK) |
3323eec9 MZ |
104 | * |
105 | * The policy is defined in terms of keypairs: | |
106 | * subj=, obj=, type=, func=, mask=, fsmagic= | |
107 | * subj,obj, and type: are LSM specific. | |
16cac49f | 108 | * func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK |
3323eec9 MZ |
109 | * mask: contains the permission mask |
110 | * fsmagic: hex value | |
111 | * | |
2fe5d6de MZ |
112 | * Returns IMA_MEASURE, IMA_APPRAISE mask. |
113 | * | |
114 | */ | |
d9d300cd | 115 | int ima_get_action(struct inode *inode, int mask, int function) |
3323eec9 | 116 | { |
e7c568e0 | 117 | int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE; |
2fe5d6de MZ |
118 | |
119 | if (!ima_appraise) | |
120 | flags &= ~IMA_APPRAISE; | |
121 | ||
122 | return ima_match_policy(inode, function, mask, flags); | |
123 | } | |
3323eec9 | 124 | |
2fe5d6de MZ |
125 | int ima_must_measure(struct inode *inode, int mask, int function) |
126 | { | |
127 | return ima_match_policy(inode, function, mask, IMA_MEASURE); | |
3323eec9 MZ |
128 | } |
129 | ||
130 | /* | |
131 | * ima_collect_measurement - collect file measurement | |
132 | * | |
133 | * Calculate the file hash, if it doesn't already exist, | |
134 | * storing the measurement and i_version in the iint. | |
135 | * | |
136 | * Must be called with iint->mutex held. | |
137 | * | |
138 | * Return 0 on success, error code otherwise | |
139 | */ | |
f381c272 MZ |
140 | int ima_collect_measurement(struct integrity_iint_cache *iint, |
141 | struct file *file) | |
3323eec9 | 142 | { |
2fe5d6de MZ |
143 | struct inode *inode = file->f_dentry->d_inode; |
144 | const char *filename = file->f_dentry->d_name.name; | |
145 | int result = 0; | |
3323eec9 | 146 | |
2fe5d6de | 147 | if (!(iint->flags & IMA_COLLECTED)) { |
3323eec9 MZ |
148 | u64 i_version = file->f_dentry->d_inode->i_version; |
149 | ||
5a44b412 MZ |
150 | iint->ima_xattr.type = IMA_XATTR_DIGEST; |
151 | result = ima_calc_hash(file, iint->ima_xattr.digest); | |
2fe5d6de | 152 | if (!result) { |
3323eec9 | 153 | iint->version = i_version; |
2fe5d6de MZ |
154 | iint->flags |= IMA_COLLECTED; |
155 | } | |
3323eec9 | 156 | } |
2fe5d6de MZ |
157 | if (result) |
158 | integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, | |
159 | filename, "collect_data", "failed", | |
160 | result, 0); | |
3323eec9 MZ |
161 | return result; |
162 | } | |
163 | ||
164 | /* | |
165 | * ima_store_measurement - store file measurement | |
166 | * | |
167 | * Create an "ima" template and then store the template by calling | |
168 | * ima_store_template. | |
169 | * | |
170 | * We only get here if the inode has not already been measured, | |
171 | * but the measurement could already exist: | |
172 | * - multiple copies of the same file on either the same or | |
173 | * different filesystems. | |
174 | * - the inode was previously flushed as well as the iint info, | |
175 | * containing the hashing info. | |
176 | * | |
177 | * Must be called with iint->mutex held. | |
178 | */ | |
f381c272 MZ |
179 | void ima_store_measurement(struct integrity_iint_cache *iint, |
180 | struct file *file, const unsigned char *filename) | |
3323eec9 MZ |
181 | { |
182 | const char *op = "add_template_measure"; | |
183 | const char *audit_cause = "ENOMEM"; | |
184 | int result = -ENOMEM; | |
185 | struct inode *inode = file->f_dentry->d_inode; | |
186 | struct ima_template_entry *entry; | |
187 | int violation = 0; | |
188 | ||
2fe5d6de MZ |
189 | if (iint->flags & IMA_MEASURED) |
190 | return; | |
191 | ||
3323eec9 MZ |
192 | entry = kmalloc(sizeof(*entry), GFP_KERNEL); |
193 | if (!entry) { | |
194 | integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, | |
195 | op, audit_cause, result, 0); | |
196 | return; | |
197 | } | |
198 | memset(&entry->template, 0, sizeof(entry->template)); | |
5a44b412 | 199 | memcpy(entry->template.digest, iint->ima_xattr.digest, IMA_DIGEST_SIZE); |
08e1b76a MZ |
200 | strcpy(entry->template.file_name, |
201 | (strlen(filename) > IMA_EVENT_NAME_LEN_MAX) ? | |
202 | file->f_dentry->d_name.name : filename); | |
3323eec9 MZ |
203 | |
204 | result = ima_store_template(entry, violation, inode); | |
45fae749 | 205 | if (!result || result == -EEXIST) |
3323eec9 | 206 | iint->flags |= IMA_MEASURED; |
45fae749 | 207 | if (result < 0) |
3323eec9 MZ |
208 | kfree(entry); |
209 | } | |
e7c568e0 PM |
210 | |
211 | void ima_audit_measurement(struct integrity_iint_cache *iint, | |
212 | const unsigned char *filename) | |
213 | { | |
214 | struct audit_buffer *ab; | |
215 | char hash[(IMA_DIGEST_SIZE * 2) + 1]; | |
216 | int i; | |
217 | ||
218 | if (iint->flags & IMA_AUDITED) | |
219 | return; | |
220 | ||
221 | for (i = 0; i < IMA_DIGEST_SIZE; i++) | |
222 | hex_byte_pack(hash + (i * 2), iint->ima_xattr.digest[i]); | |
223 | hash[i * 2] = '\0'; | |
224 | ||
225 | ab = audit_log_start(current->audit_context, GFP_KERNEL, | |
226 | AUDIT_INTEGRITY_RULE); | |
227 | if (!ab) | |
228 | return; | |
229 | ||
230 | audit_log_format(ab, "file="); | |
231 | audit_log_untrustedstring(ab, filename); | |
232 | audit_log_format(ab, " hash="); | |
233 | audit_log_untrustedstring(ab, hash); | |
234 | ||
235 | audit_log_task_info(ab, current); | |
236 | audit_log_end(ab); | |
237 | ||
238 | iint->flags |= IMA_AUDITED; | |
239 | } |