1 /*
2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3  *
4  * Authors:
5  * Reiner Sailer <sailer@watson.ibm.com>
6  * Serge Hallyn <serue@us.ibm.com>
7  * Kylene Hall <kylene@us.ibm.com>
8  * Mimi Zohar <zohar@us.ibm.com>
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public License as
12  * published by the Free Software Foundation, version 2 of the
13  * License.
14  *
15  * File: ima_main.c
16  *	implements the IMA hooks: ima_bprm_check, ima_file_mmap,
17  *	and ima_file_check.
18  */
19 #include <linux/module.h>
20 #include <linux/file.h>
21 #include <linux/binfmts.h>
22 #include <linux/mount.h>
23 #include <linux/mman.h>
24 #include <linux/slab.h>
25 #include <linux/ima.h>
26 
27 #include "ima.h"
28 
29 int ima_initialized;
30 
31 char *ima_hash = "sha1";
32 static int __init hash_setup(char *str)
33 {
34 	if (strncmp(str, "md5", 3) == 0)
35 		ima_hash = "md5";
36 	return 1;
37 }
38 __setup("ima_hash=", hash_setup);
39 
40 /*
41  * ima_rdwr_violation_check
42  *
43  * Only invalidate the PCR for measured files:
44  * 	- Opening a file for write when already open for read,
45  *	  results in a time of measure, time of use (ToMToU) error.
46  *	- Opening a file for read when already open for write,
47  * 	  could result in a file measurement error.
48  *
49  */
50 static void ima_rdwr_violation_check(struct file *file)
51 {
52 	struct dentry *dentry = file->f_path.dentry;
53 	struct inode *inode = dentry->d_inode;
54 	fmode_t mode = file->f_mode;
55 	int rc;
56 	bool send_tomtou = false, send_writers = false;
57 
58 	if (!S_ISREG(inode->i_mode) || !ima_initialized)
59 		return;
60 
61 	mutex_lock(&inode->i_mutex);	/* file metadata: permissions, xattr */
62 
63 	if (mode & FMODE_WRITE) {
64 		if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
65 			send_tomtou = true;
66 		goto out;
67 	}
68 
69 	rc = ima_must_measure(inode, MAY_READ, FILE_CHECK);
70 	if (rc < 0)
71 		goto out;
72 
73 	if (atomic_read(&inode->i_writecount) > 0)
74 		send_writers = true;
75 out:
76 	mutex_unlock(&inode->i_mutex);
77 
78 	if (send_tomtou)
79 		ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
80 				  "ToMToU");
81 	if (send_writers)
82 		ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
83 				  "open_writers");
84 }
85 
86 static void ima_check_last_writer(struct integrity_iint_cache *iint,
87 				  struct inode *inode,
88 				  struct file *file)
89 {
90 	fmode_t mode = file->f_mode;
91 
92 	mutex_lock(&iint->mutex);
93 	if (mode & FMODE_WRITE &&
94 	    atomic_read(&inode->i_writecount) == 1 &&
95 	    iint->version != inode->i_version)
96 		iint->flags &= ~IMA_MEASURED;
97 	mutex_unlock(&iint->mutex);
98 }
99 
100 /**
101  * ima_file_free - called on __fput()
102  * @file: pointer to file structure being freed
103  *
104  * Flag files that changed, based on i_version
105  */
106 void ima_file_free(struct file *file)
107 {
108 	struct inode *inode = file->f_dentry->d_inode;
109 	struct integrity_iint_cache *iint;
110 
111 	if (!iint_initialized || !S_ISREG(inode->i_mode))
112 		return;
113 
114 	iint = integrity_iint_find(inode);
115 	if (!iint)
116 		return;
117 
118 	ima_check_last_writer(iint, inode, file);
119 }
120 
121 static int process_measurement(struct file *file, const unsigned char *filename,
122 			       int mask, int function)
123 {
124 	struct inode *inode = file->f_dentry->d_inode;
125 	struct integrity_iint_cache *iint;
126 	int rc = 0;
127 
128 	if (!ima_initialized || !S_ISREG(inode->i_mode))
129 		return 0;
130 
131 	rc = ima_must_measure(inode, mask, function);
132 	if (rc != 0)
133 		return rc;
134 retry:
135 	iint = integrity_iint_find(inode);
136 	if (!iint) {
137 		rc = integrity_inode_alloc(inode);
138 		if (!rc || rc == -EEXIST)
139 			goto retry;
140 		return rc;
141 	}
142 
143 	mutex_lock(&iint->mutex);
144 
145 	rc = iint->flags & IMA_MEASURED ? 1 : 0;
146 	if (rc != 0)
147 		goto out;
148 
149 	rc = ima_collect_measurement(iint, file);
150 	if (!rc)
151 		ima_store_measurement(iint, file, filename);
152 out:
153 	mutex_unlock(&iint->mutex);
154 	return rc;
155 }
156 
157 /**
158  * ima_file_mmap - based on policy, collect/store measurement.
159  * @file: pointer to the file to be measured (May be NULL)
160  * @prot: contains the protection that will be applied by the kernel.
161  *
162  * Measure files being mmapped executable based on the ima_must_measure()
163  * policy decision.
164  *
165  * Return 0 on success, an error code on failure.
166  * (Based on the results of appraise_measurement().)
167  */
168 int ima_file_mmap(struct file *file, unsigned long prot)
169 {
170 	int rc;
171 
172 	if (!file)
173 		return 0;
174 	if (prot & PROT_EXEC)
175 		rc = process_measurement(file, file->f_dentry->d_name.name,
176 					 MAY_EXEC, FILE_MMAP);
177 	return 0;
178 }
179 
180 /**
181  * ima_bprm_check - based on policy, collect/store measurement.
182  * @bprm: contains the linux_binprm structure
183  *
184  * The OS protects against an executable file, already open for write,
185  * from being executed in deny_write_access() and an executable file,
186  * already open for execute, from being modified in get_write_access().
187  * So we can be certain that what we verify and measure here is actually
188  * what is being executed.
189  *
190  * Return 0 on success, an error code on failure.
191  * (Based on the results of appraise_measurement().)
192  */
193 int ima_bprm_check(struct linux_binprm *bprm)
194 {
195 	int rc;
196 
197 	rc = process_measurement(bprm->file, bprm->filename,
198 				 MAY_EXEC, BPRM_CHECK);
199 	return 0;
200 }
201 
202 /**
203  * ima_path_check - based on policy, collect/store measurement.
204  * @file: pointer to the file to be measured
205  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
206  *
207  * Measure files based on the ima_must_measure() policy decision.
208  *
209  * Always return 0 and audit dentry_open failures.
210  * (Return code will be based upon measurement appraisal.)
211  */
212 int ima_file_check(struct file *file, int mask)
213 {
214 	int rc;
215 
216 	ima_rdwr_violation_check(file);
217 	rc = process_measurement(file, file->f_dentry->d_name.name,
218 				 mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
219 				 FILE_CHECK);
220 	return 0;
221 }
222 EXPORT_SYMBOL_GPL(ima_file_check);
223 
224 static int __init init_ima(void)
225 {
226 	int error;
227 
228 	error = ima_init();
229 	ima_initialized = 1;
230 	return error;
231 }
232 
233 static void __exit cleanup_ima(void)
234 {
235 	ima_cleanup();
236 }
237 
238 late_initcall(init_ima);	/* Start IMA after the TPM is available */
239 
240 MODULE_DESCRIPTION("Integrity Measurement Architecture");
241 MODULE_LICENSE("GPL");
242