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 unsigned char *pathname = NULL, *pathbuf = NULL; 58 59 if (!S_ISREG(inode->i_mode) || !ima_initialized) 60 return; 61 62 mutex_lock(&inode->i_mutex); /* file metadata: permissions, xattr */ 63 64 if (mode & FMODE_WRITE) { 65 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) 66 send_tomtou = true; 67 goto out; 68 } 69 70 rc = ima_must_measure(inode, MAY_READ, FILE_CHECK); 71 if (rc < 0) 72 goto out; 73 74 if (atomic_read(&inode->i_writecount) > 0) 75 send_writers = true; 76 out: 77 mutex_unlock(&inode->i_mutex); 78 79 if (!send_tomtou && !send_writers) 80 return; 81 82 /* We will allow 11 spaces for ' (deleted)' to be appended */ 83 pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL); 84 if (pathbuf) { 85 pathname = d_path(&file->f_path, pathbuf, PATH_MAX + 11); 86 if (IS_ERR(pathname)) 87 pathname = NULL; 88 else if (strlen(pathname) > IMA_EVENT_NAME_LEN_MAX) 89 pathname = NULL; 90 } 91 if (send_tomtou) 92 ima_add_violation(inode, 93 !pathname ? dentry->d_name.name : pathname, 94 "invalid_pcr", "ToMToU"); 95 if (send_writers) 96 ima_add_violation(inode, 97 !pathname ? dentry->d_name.name : pathname, 98 "invalid_pcr", "open_writers"); 99 kfree(pathbuf); 100 } 101 102 static void ima_check_last_writer(struct integrity_iint_cache *iint, 103 struct inode *inode, 104 struct file *file) 105 { 106 fmode_t mode = file->f_mode; 107 108 mutex_lock(&iint->mutex); 109 if (mode & FMODE_WRITE && 110 atomic_read(&inode->i_writecount) == 1 && 111 iint->version != inode->i_version) 112 iint->flags &= ~IMA_MEASURED; 113 mutex_unlock(&iint->mutex); 114 } 115 116 /** 117 * ima_file_free - called on __fput() 118 * @file: pointer to file structure being freed 119 * 120 * Flag files that changed, based on i_version 121 */ 122 void ima_file_free(struct file *file) 123 { 124 struct inode *inode = file->f_dentry->d_inode; 125 struct integrity_iint_cache *iint; 126 127 if (!iint_initialized || !S_ISREG(inode->i_mode)) 128 return; 129 130 iint = integrity_iint_find(inode); 131 if (!iint) 132 return; 133 134 ima_check_last_writer(iint, inode, file); 135 } 136 137 static int process_measurement(struct file *file, const unsigned char *filename, 138 int mask, int function) 139 { 140 struct inode *inode = file->f_dentry->d_inode; 141 struct integrity_iint_cache *iint; 142 unsigned char *pathname = NULL, *pathbuf = NULL; 143 int rc = 0; 144 145 if (!ima_initialized || !S_ISREG(inode->i_mode)) 146 return 0; 147 148 rc = ima_must_measure(inode, mask, function); 149 if (rc != 0) 150 return rc; 151 retry: 152 iint = integrity_iint_find(inode); 153 if (!iint) { 154 rc = integrity_inode_alloc(inode); 155 if (!rc || rc == -EEXIST) 156 goto retry; 157 return rc; 158 } 159 160 mutex_lock(&iint->mutex); 161 162 rc = iint->flags & IMA_MEASURED ? 1 : 0; 163 if (rc != 0) 164 goto out; 165 166 rc = ima_collect_measurement(iint, file); 167 if (rc != 0) 168 goto out; 169 170 if (function != BPRM_CHECK) { 171 /* We will allow 11 spaces for ' (deleted)' to be appended */ 172 pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL); 173 if (pathbuf) { 174 pathname = 175 d_path(&file->f_path, pathbuf, PATH_MAX + 11); 176 if (IS_ERR(pathname)) 177 pathname = NULL; 178 } 179 } 180 ima_store_measurement(iint, file, !pathname ? filename : pathname); 181 kfree(pathbuf); 182 out: 183 mutex_unlock(&iint->mutex); 184 return rc; 185 } 186 187 /** 188 * ima_file_mmap - based on policy, collect/store measurement. 189 * @file: pointer to the file to be measured (May be NULL) 190 * @prot: contains the protection that will be applied by the kernel. 191 * 192 * Measure files being mmapped executable based on the ima_must_measure() 193 * policy decision. 194 * 195 * Return 0 on success, an error code on failure. 196 * (Based on the results of appraise_measurement().) 197 */ 198 int ima_file_mmap(struct file *file, unsigned long prot) 199 { 200 int rc; 201 202 if (!file) 203 return 0; 204 if (prot & PROT_EXEC) 205 rc = process_measurement(file, file->f_dentry->d_name.name, 206 MAY_EXEC, FILE_MMAP); 207 return 0; 208 } 209 210 /** 211 * ima_bprm_check - based on policy, collect/store measurement. 212 * @bprm: contains the linux_binprm structure 213 * 214 * The OS protects against an executable file, already open for write, 215 * from being executed in deny_write_access() and an executable file, 216 * already open for execute, from being modified in get_write_access(). 217 * So we can be certain that what we verify and measure here is actually 218 * what is being executed. 219 * 220 * Return 0 on success, an error code on failure. 221 * (Based on the results of appraise_measurement().) 222 */ 223 int ima_bprm_check(struct linux_binprm *bprm) 224 { 225 int rc; 226 227 rc = process_measurement(bprm->file, 228 (strcmp(bprm->filename, bprm->interp) == 0) ? 229 bprm->filename : bprm->interp, 230 MAY_EXEC, BPRM_CHECK); 231 return 0; 232 } 233 234 /** 235 * ima_path_check - based on policy, collect/store measurement. 236 * @file: pointer to the file to be measured 237 * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE 238 * 239 * Measure files based on the ima_must_measure() policy decision. 240 * 241 * Always return 0 and audit dentry_open failures. 242 * (Return code will be based upon measurement appraisal.) 243 */ 244 int ima_file_check(struct file *file, int mask) 245 { 246 int rc; 247 248 ima_rdwr_violation_check(file); 249 rc = process_measurement(file, file->f_dentry->d_name.name, 250 mask & (MAY_READ | MAY_WRITE | MAY_EXEC), 251 FILE_CHECK); 252 return 0; 253 } 254 EXPORT_SYMBOL_GPL(ima_file_check); 255 256 static int __init init_ima(void) 257 { 258 int error; 259 260 error = ima_init(); 261 if (!error) 262 ima_initialized = 1; 263 return error; 264 } 265 266 late_initcall(init_ima); /* Start IMA after the TPM is available */ 267 268 MODULE_DESCRIPTION("Integrity Measurement Architecture"); 269 MODULE_LICENSE("GPL"); 270