1 /* 2 * Copyright (C) 2011 IBM Corporation 3 * 4 * Author: 5 * Mimi Zohar <zohar@us.ibm.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation, version 2 of the License. 10 */ 11 #include <linux/module.h> 12 #include <linux/file.h> 13 #include <linux/fs.h> 14 #include <linux/xattr.h> 15 #include <linux/magic.h> 16 #include <linux/ima.h> 17 #include <linux/evm.h> 18 19 #include "ima.h" 20 21 static int __init default_appraise_setup(char *str) 22 { 23 if (strncmp(str, "off", 3) == 0) 24 ima_appraise = 0; 25 else if (strncmp(str, "fix", 3) == 0) 26 ima_appraise = IMA_APPRAISE_FIX; 27 return 1; 28 } 29 30 __setup("ima_appraise=", default_appraise_setup); 31 32 /* 33 * ima_must_appraise - set appraise flag 34 * 35 * Return 1 to appraise 36 */ 37 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) 38 { 39 if (!ima_appraise) 40 return 0; 41 42 return ima_match_policy(inode, func, mask, IMA_APPRAISE); 43 } 44 45 static int ima_fix_xattr(struct dentry *dentry, 46 struct integrity_iint_cache *iint) 47 { 48 iint->ima_xattr.type = IMA_XATTR_DIGEST; 49 return __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, 50 (u8 *)&iint->ima_xattr, 51 sizeof(iint->ima_xattr), 0); 52 } 53 54 /* Return specific func appraised cached result */ 55 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, 56 int func) 57 { 58 switch(func) { 59 case MMAP_CHECK: 60 return iint->ima_mmap_status; 61 case BPRM_CHECK: 62 return iint->ima_bprm_status; 63 case MODULE_CHECK: 64 return iint->ima_module_status; 65 case FILE_CHECK: 66 default: 67 return iint->ima_file_status; 68 } 69 } 70 71 static void ima_set_cache_status(struct integrity_iint_cache *iint, 72 int func, enum integrity_status status) 73 { 74 switch(func) { 75 case MMAP_CHECK: 76 iint->ima_mmap_status = status; 77 break; 78 case BPRM_CHECK: 79 iint->ima_bprm_status = status; 80 break; 81 case MODULE_CHECK: 82 iint->ima_module_status = status; 83 break; 84 case FILE_CHECK: 85 default: 86 iint->ima_file_status = status; 87 break; 88 } 89 } 90 91 static void ima_cache_flags(struct integrity_iint_cache *iint, int func) 92 { 93 switch(func) { 94 case MMAP_CHECK: 95 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); 96 break; 97 case BPRM_CHECK: 98 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); 99 break; 100 case MODULE_CHECK: 101 iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED); 102 break; 103 case FILE_CHECK: 104 default: 105 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); 106 break; 107 } 108 } 109 110 /* 111 * ima_appraise_measurement - appraise file measurement 112 * 113 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 114 * Assuming success, compare the xattr hash with the collected measurement. 115 * 116 * Return 0 on success, error code otherwise 117 */ 118 int ima_appraise_measurement(int func, struct integrity_iint_cache *iint, 119 struct file *file, const unsigned char *filename) 120 { 121 struct dentry *dentry = file->f_dentry; 122 struct inode *inode = dentry->d_inode; 123 struct evm_ima_xattr_data *xattr_value = NULL; 124 enum integrity_status status = INTEGRITY_UNKNOWN; 125 const char *op = "appraise_data"; 126 char *cause = "unknown"; 127 int rc; 128 129 if (!ima_appraise) 130 return 0; 131 if (!inode->i_op->getxattr) 132 return INTEGRITY_UNKNOWN; 133 134 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value, 135 0, GFP_NOFS); 136 if (rc <= 0) { 137 if (rc && rc != -ENODATA) 138 goto out; 139 140 cause = "missing-hash"; 141 status = 142 (inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL; 143 goto out; 144 } 145 146 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); 147 if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) { 148 if ((status == INTEGRITY_NOLABEL) 149 || (status == INTEGRITY_NOXATTRS)) 150 cause = "missing-HMAC"; 151 else if (status == INTEGRITY_FAIL) 152 cause = "invalid-HMAC"; 153 goto out; 154 } 155 switch (xattr_value->type) { 156 case IMA_XATTR_DIGEST: 157 if (iint->flags & IMA_DIGSIG_REQUIRED) { 158 cause = "IMA signature required"; 159 status = INTEGRITY_FAIL; 160 break; 161 } 162 rc = memcmp(xattr_value->digest, iint->ima_xattr.digest, 163 IMA_DIGEST_SIZE); 164 if (rc) { 165 cause = "invalid-hash"; 166 status = INTEGRITY_FAIL; 167 break; 168 } 169 status = INTEGRITY_PASS; 170 break; 171 case EVM_IMA_XATTR_DIGSIG: 172 iint->flags |= IMA_DIGSIG; 173 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 174 xattr_value->digest, rc - 1, 175 iint->ima_xattr.digest, 176 IMA_DIGEST_SIZE); 177 if (rc == -EOPNOTSUPP) { 178 status = INTEGRITY_UNKNOWN; 179 } else if (rc) { 180 cause = "invalid-signature"; 181 status = INTEGRITY_FAIL; 182 } else { 183 status = INTEGRITY_PASS; 184 } 185 break; 186 default: 187 status = INTEGRITY_UNKNOWN; 188 cause = "unknown-ima-data"; 189 break; 190 } 191 192 out: 193 if (status != INTEGRITY_PASS) { 194 if ((ima_appraise & IMA_APPRAISE_FIX) && 195 (!xattr_value || 196 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 197 if (!ima_fix_xattr(dentry, iint)) 198 status = INTEGRITY_PASS; 199 } 200 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 201 op, cause, rc, 0); 202 } else { 203 ima_cache_flags(iint, func); 204 } 205 ima_set_cache_status(iint, func, status); 206 kfree(xattr_value); 207 return status; 208 } 209 210 /* 211 * ima_update_xattr - update 'security.ima' hash value 212 */ 213 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) 214 { 215 struct dentry *dentry = file->f_dentry; 216 int rc = 0; 217 218 /* do not collect and update hash for digital signatures */ 219 if (iint->flags & IMA_DIGSIG) 220 return; 221 222 rc = ima_collect_measurement(iint, file); 223 if (rc < 0) 224 return; 225 226 ima_fix_xattr(dentry, iint); 227 } 228 229 /** 230 * ima_inode_post_setattr - reflect file metadata changes 231 * @dentry: pointer to the affected dentry 232 * 233 * Changes to a dentry's metadata might result in needing to appraise. 234 * 235 * This function is called from notify_change(), which expects the caller 236 * to lock the inode's i_mutex. 237 */ 238 void ima_inode_post_setattr(struct dentry *dentry) 239 { 240 struct inode *inode = dentry->d_inode; 241 struct integrity_iint_cache *iint; 242 int must_appraise, rc; 243 244 if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode) 245 || !inode->i_op->removexattr) 246 return; 247 248 must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); 249 iint = integrity_iint_find(inode); 250 if (iint) { 251 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | 252 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | 253 IMA_ACTION_FLAGS); 254 if (must_appraise) 255 iint->flags |= IMA_APPRAISE; 256 } 257 if (!must_appraise) 258 rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA); 259 return; 260 } 261 262 /* 263 * ima_protect_xattr - protect 'security.ima' 264 * 265 * Ensure that not just anyone can modify or remove 'security.ima'. 266 */ 267 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 268 const void *xattr_value, size_t xattr_value_len) 269 { 270 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 271 if (!capable(CAP_SYS_ADMIN)) 272 return -EPERM; 273 return 1; 274 } 275 return 0; 276 } 277 278 static void ima_reset_appraise_flags(struct inode *inode) 279 { 280 struct integrity_iint_cache *iint; 281 282 if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)) 283 return; 284 285 iint = integrity_iint_find(inode); 286 if (!iint) 287 return; 288 289 iint->flags &= ~IMA_DONE_MASK; 290 return; 291 } 292 293 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, 294 const void *xattr_value, size_t xattr_value_len) 295 { 296 int result; 297 298 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 299 xattr_value_len); 300 if (result == 1) { 301 ima_reset_appraise_flags(dentry->d_inode); 302 result = 0; 303 } 304 return result; 305 } 306 307 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) 308 { 309 int result; 310 311 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 312 if (result == 1) { 313 ima_reset_appraise_flags(dentry->d_inode); 314 result = 0; 315 } 316 return result; 317 } 318