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, enum ima_hooks func, int mask) 38 { 39 if (!ima_appraise) 40 return 0; 41 42 return ima_match_policy(inode, func, mask, IMA_APPRAISE); 43 } 44 45 static void ima_fix_xattr(struct dentry *dentry, 46 struct integrity_iint_cache *iint) 47 { 48 iint->ima_xattr.type = IMA_XATTR_DIGEST; 49 __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, (u8 *)&iint->ima_xattr, 50 sizeof iint->ima_xattr, 0); 51 } 52 53 /* 54 * ima_appraise_measurement - appraise file measurement 55 * 56 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 57 * Assuming success, compare the xattr hash with the collected measurement. 58 * 59 * Return 0 on success, error code otherwise 60 */ 61 int ima_appraise_measurement(struct integrity_iint_cache *iint, 62 struct file *file, const unsigned char *filename) 63 { 64 struct dentry *dentry = file->f_dentry; 65 struct inode *inode = dentry->d_inode; 66 struct evm_ima_xattr_data *xattr_value = NULL; 67 enum integrity_status status = INTEGRITY_UNKNOWN; 68 const char *op = "appraise_data"; 69 char *cause = "unknown"; 70 int rc; 71 72 if (!ima_appraise) 73 return 0; 74 if (!inode->i_op->getxattr) 75 return INTEGRITY_UNKNOWN; 76 77 if (iint->flags & IMA_APPRAISED) 78 return iint->ima_status; 79 80 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value, 81 0, GFP_NOFS); 82 if (rc <= 0) { 83 if (rc && rc != -ENODATA) 84 goto out; 85 86 cause = "missing-hash"; 87 status = 88 (inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL; 89 goto out; 90 } 91 92 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); 93 if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) { 94 if ((status == INTEGRITY_NOLABEL) 95 || (status == INTEGRITY_NOXATTRS)) 96 cause = "missing-HMAC"; 97 else if (status == INTEGRITY_FAIL) 98 cause = "invalid-HMAC"; 99 goto out; 100 } 101 102 switch (xattr_value->type) { 103 case IMA_XATTR_DIGEST: 104 rc = memcmp(xattr_value->digest, iint->ima_xattr.digest, 105 IMA_DIGEST_SIZE); 106 if (rc) { 107 cause = "invalid-hash"; 108 status = INTEGRITY_FAIL; 109 print_hex_dump_bytes("security.ima: ", DUMP_PREFIX_NONE, 110 xattr_value, sizeof(*xattr_value)); 111 print_hex_dump_bytes("collected: ", DUMP_PREFIX_NONE, 112 (u8 *)&iint->ima_xattr, 113 sizeof iint->ima_xattr); 114 break; 115 } 116 status = INTEGRITY_PASS; 117 break; 118 case EVM_IMA_XATTR_DIGSIG: 119 iint->flags |= IMA_DIGSIG; 120 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 121 xattr_value->digest, rc - 1, 122 iint->ima_xattr.digest, 123 IMA_DIGEST_SIZE); 124 if (rc == -EOPNOTSUPP) { 125 status = INTEGRITY_UNKNOWN; 126 } else if (rc) { 127 cause = "invalid-signature"; 128 status = INTEGRITY_FAIL; 129 } else { 130 status = INTEGRITY_PASS; 131 } 132 break; 133 default: 134 status = INTEGRITY_UNKNOWN; 135 cause = "unknown-ima-data"; 136 break; 137 } 138 139 out: 140 if (status != INTEGRITY_PASS) { 141 if ((ima_appraise & IMA_APPRAISE_FIX) && 142 (!xattr_value || 143 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 144 ima_fix_xattr(dentry, iint); 145 status = INTEGRITY_PASS; 146 } 147 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 148 op, cause, rc, 0); 149 } else { 150 iint->flags |= IMA_APPRAISED; 151 } 152 iint->ima_status = status; 153 kfree(xattr_value); 154 return status; 155 } 156 157 /* 158 * ima_update_xattr - update 'security.ima' hash value 159 */ 160 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) 161 { 162 struct dentry *dentry = file->f_dentry; 163 int rc = 0; 164 165 /* do not collect and update hash for digital signatures */ 166 if (iint->flags & IMA_DIGSIG) 167 return; 168 169 rc = ima_collect_measurement(iint, file); 170 if (rc < 0) 171 return; 172 173 ima_fix_xattr(dentry, iint); 174 } 175 176 /** 177 * ima_inode_post_setattr - reflect file metadata changes 178 * @dentry: pointer to the affected dentry 179 * 180 * Changes to a dentry's metadata might result in needing to appraise. 181 * 182 * This function is called from notify_change(), which expects the caller 183 * to lock the inode's i_mutex. 184 */ 185 void ima_inode_post_setattr(struct dentry *dentry) 186 { 187 struct inode *inode = dentry->d_inode; 188 struct integrity_iint_cache *iint; 189 int must_appraise, rc; 190 191 if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode) 192 || !inode->i_op->removexattr) 193 return; 194 195 must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); 196 iint = integrity_iint_find(inode); 197 if (iint) { 198 if (must_appraise) 199 iint->flags |= IMA_APPRAISE; 200 else 201 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED); 202 } 203 if (!must_appraise) 204 rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA); 205 return; 206 } 207 208 /* 209 * ima_protect_xattr - protect 'security.ima' 210 * 211 * Ensure that not just anyone can modify or remove 'security.ima'. 212 */ 213 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 214 const void *xattr_value, size_t xattr_value_len) 215 { 216 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 217 if (!capable(CAP_SYS_ADMIN)) 218 return -EPERM; 219 return 1; 220 } 221 return 0; 222 } 223 224 static void ima_reset_appraise_flags(struct inode *inode) 225 { 226 struct integrity_iint_cache *iint; 227 228 if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)) 229 return; 230 231 iint = integrity_iint_find(inode); 232 if (!iint) 233 return; 234 235 iint->flags &= ~IMA_DONE_MASK; 236 return; 237 } 238 239 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, 240 const void *xattr_value, size_t xattr_value_len) 241 { 242 int result; 243 244 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 245 xattr_value_len); 246 if (result == 1) { 247 ima_reset_appraise_flags(dentry->d_inode); 248 result = 0; 249 } 250 return result; 251 } 252 253 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) 254 { 255 int result; 256 257 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 258 if (result == 1) { 259 ima_reset_appraise_flags(dentry->d_inode); 260 result = 0; 261 } 262 return result; 263 } 264