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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 | |
12 | * Implements must_measure, collect_measurement, store_measurement, | |
13 | * and store_template. | |
14 | */ | |
15 | #include <linux/module.h> | |
16 | ||
17 | #include "ima.h" | |
18 | static char *IMA_TEMPLATE_NAME = "ima"; | |
19 | ||
20 | /* | |
21 | * ima_store_template - store ima template measurements | |
22 | * | |
23 | * Calculate the hash of a template entry, add the template entry | |
24 | * to an ordered list of measurement entries maintained inside the kernel, | |
25 | * and also update the aggregate integrity value (maintained inside the | |
26 | * configured TPM PCR) over the hashes of the current list of measurement | |
27 | * entries. | |
28 | * | |
29 | * Applications retrieve the current kernel-held measurement list through | |
30 | * the securityfs entries in /sys/kernel/security/ima. The signed aggregate | |
31 | * TPM PCR (called quote) can be retrieved using a TPM user space library | |
32 | * and is used to validate the measurement list. | |
33 | * | |
34 | * Returns 0 on success, error code otherwise | |
35 | */ | |
36 | int ima_store_template(struct ima_template_entry *entry, | |
37 | int violation, struct inode *inode) | |
38 | { | |
39 | const char *op = "add_template_measure"; | |
40 | const char *audit_cause = "hashing_error"; | |
41 | int result; | |
42 | ||
43 | memset(entry->digest, 0, sizeof(entry->digest)); | |
44 | entry->template_name = IMA_TEMPLATE_NAME; | |
45 | entry->template_len = sizeof(entry->template); | |
46 | ||
47 | if (!violation) { | |
48 | result = ima_calc_template_hash(entry->template_len, | |
49 | &entry->template, | |
50 | entry->digest); | |
51 | if (result < 0) { | |
52 | integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, | |
53 | entry->template_name, op, | |
54 | audit_cause, result, 0); | |
55 | return result; | |
56 | } | |
57 | } | |
58 | result = ima_add_template_entry(entry, violation, op, inode); | |
59 | return result; | |
60 | } | |
61 | ||
62 | /* | |
63 | * ima_add_violation - add violation to measurement list. | |
64 | * | |
65 | * Violations are flagged in the measurement list with zero hash values. | |
66 | * By extending the PCR with 0xFF's instead of with zeroes, the PCR | |
67 | * value is invalidated. | |
68 | */ | |
69 | void ima_add_violation(struct inode *inode, const unsigned char *filename, | |
70 | const char *op, const char *cause) | |
71 | { | |
72 | struct ima_template_entry *entry; | |
73 | int violation = 1; | |
74 | int result; | |
75 | ||
76 | /* can overflow, only indicator */ | |
77 | atomic_long_inc(&ima_htable.violations); | |
78 | ||
79 | entry = kmalloc(sizeof(*entry), GFP_KERNEL); | |
80 | if (!entry) { | |
81 | result = -ENOMEM; | |
82 | goto err_out; | |
83 | } | |
84 | memset(&entry->template, 0, sizeof(entry->template)); | |
85 | strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX); | |
86 | result = ima_store_template(entry, violation, inode); | |
87 | if (result < 0) | |
88 | kfree(entry); | |
89 | err_out: | |
90 | integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, | |
91 | op, cause, result, 0); | |
92 | } | |
93 | ||
94 | /** | |
95 | * ima_must_measure - measure decision based on policy. | |
96 | * @inode: pointer to inode to measure | |
97 | * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE) | |
98 | * @function: calling function (PATH_CHECK, BPRM_CHECK, FILE_MMAP) | |
99 | * | |
100 | * The policy is defined in terms of keypairs: | |
101 | * subj=, obj=, type=, func=, mask=, fsmagic= | |
102 | * subj,obj, and type: are LSM specific. | |
103 | * func: PATH_CHECK | BPRM_CHECK | FILE_MMAP | |
104 | * mask: contains the permission mask | |
105 | * fsmagic: hex value | |
106 | * | |
107 | * Must be called with iint->mutex held. | |
108 | * | |
109 | * Return 0 to measure. Return 1 if already measured. | |
110 | * For matching a DONT_MEASURE policy, no policy, or other | |
111 | * error, return an error code. | |
112 | */ | |
113 | int ima_must_measure(struct ima_iint_cache *iint, struct inode *inode, | |
114 | int mask, int function) | |
115 | { | |
116 | int must_measure; | |
117 | ||
118 | if (iint->flags & IMA_MEASURED) | |
119 | return 1; | |
120 | ||
121 | must_measure = ima_match_policy(inode, function, mask); | |
122 | return must_measure ? 0 : -EACCES; | |
123 | } | |
124 | ||
125 | /* | |
126 | * ima_collect_measurement - collect file measurement | |
127 | * | |
128 | * Calculate the file hash, if it doesn't already exist, | |
129 | * storing the measurement and i_version in the iint. | |
130 | * | |
131 | * Must be called with iint->mutex held. | |
132 | * | |
133 | * Return 0 on success, error code otherwise | |
134 | */ | |
135 | int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file) | |
136 | { | |
137 | int result = -EEXIST; | |
138 | ||
139 | if (!(iint->flags & IMA_MEASURED)) { | |
140 | u64 i_version = file->f_dentry->d_inode->i_version; | |
141 | ||
142 | memset(iint->digest, 0, IMA_DIGEST_SIZE); | |
143 | result = ima_calc_hash(file, iint->digest); | |
144 | if (!result) | |
145 | iint->version = i_version; | |
146 | } | |
147 | return result; | |
148 | } | |
149 | ||
150 | /* | |
151 | * ima_store_measurement - store file measurement | |
152 | * | |
153 | * Create an "ima" template and then store the template by calling | |
154 | * ima_store_template. | |
155 | * | |
156 | * We only get here if the inode has not already been measured, | |
157 | * but the measurement could already exist: | |
158 | * - multiple copies of the same file on either the same or | |
159 | * different filesystems. | |
160 | * - the inode was previously flushed as well as the iint info, | |
161 | * containing the hashing info. | |
162 | * | |
163 | * Must be called with iint->mutex held. | |
164 | */ | |
165 | void ima_store_measurement(struct ima_iint_cache *iint, struct file *file, | |
166 | const unsigned char *filename) | |
167 | { | |
168 | const char *op = "add_template_measure"; | |
169 | const char *audit_cause = "ENOMEM"; | |
170 | int result = -ENOMEM; | |
171 | struct inode *inode = file->f_dentry->d_inode; | |
172 | struct ima_template_entry *entry; | |
173 | int violation = 0; | |
174 | ||
175 | entry = kmalloc(sizeof(*entry), GFP_KERNEL); | |
176 | if (!entry) { | |
177 | integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, | |
178 | op, audit_cause, result, 0); | |
179 | return; | |
180 | } | |
181 | memset(&entry->template, 0, sizeof(entry->template)); | |
182 | memcpy(entry->template.digest, iint->digest, IMA_DIGEST_SIZE); | |
183 | strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX); | |
184 | ||
185 | result = ima_store_template(entry, violation, inode); | |
186 | if (!result) | |
187 | iint->flags |= IMA_MEASURED; | |
188 | else | |
189 | kfree(entry); | |
190 | } |