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