/* * Copyright (C) 2011 IBM Corporation * * Author: * Mimi Zohar <zohar@us.ibm.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, version 2 of the License. */ #include <linux/module.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/xattr.h> #include <linux/magic.h> #include <linux/ima.h> #include <linux/evm.h> #include <crypto/hash_info.h> #include "ima.h" static int __init default_appraise_setup(char *str) { if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0) ima_appraise = IMA_APPRAISE_LOG; else if (strncmp(str, "fix", 3) == 0) ima_appraise = IMA_APPRAISE_FIX; return 1; } __setup("ima_appraise=", default_appraise_setup); /* * ima_must_appraise - set appraise flag * * Return 1 to appraise */ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) { if (!ima_appraise) return 0; return ima_match_policy(inode, func, mask, IMA_APPRAISE); } static int ima_fix_xattr(struct dentry *dentry, struct integrity_iint_cache *iint) { int rc, offset; u8 algo = iint->ima_hash->algo; if (algo <= HASH_ALGO_SHA1) { offset = 1; iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; } else { offset = 0; iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; iint->ima_hash->xattr.ng.algo = algo; } rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, &iint->ima_hash->xattr.data[offset], (sizeof(iint->ima_hash->xattr) - offset) + iint->ima_hash->length, 0); return rc; } /* Return specific func appraised cached result */ enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, int func) { switch (func) { case MMAP_CHECK: return iint->ima_mmap_status; case BPRM_CHECK: return iint->ima_bprm_status; case MODULE_CHECK: return iint->ima_module_status; case FIRMWARE_CHECK: return iint->ima_firmware_status; case FILE_CHECK: default: return iint->ima_file_status; } } static void ima_set_cache_status(struct integrity_iint_cache *iint, int func, enum integrity_status status) { switch (func) { case MMAP_CHECK: iint->ima_mmap_status = status; break; case BPRM_CHECK: iint->ima_bprm_status = status; break; case MODULE_CHECK: iint->ima_module_status = status; break; case FIRMWARE_CHECK: iint->ima_firmware_status = status; break; case FILE_CHECK: default: iint->ima_file_status = status; break; } } static void ima_cache_flags(struct integrity_iint_cache *iint, int func) { switch (func) { case MMAP_CHECK: iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); break; case BPRM_CHECK: iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); break; case MODULE_CHECK: iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED); break; case FIRMWARE_CHECK: iint->flags |= (IMA_FIRMWARE_APPRAISED | IMA_APPRAISED); break; case FILE_CHECK: default: iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); break; } } void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len, struct ima_digest_data *hash) { struct signature_v2_hdr *sig; if (!xattr_value || xattr_len < 2) return; switch (xattr_value->type) { case EVM_IMA_XATTR_DIGSIG: sig = (typeof(sig))xattr_value; if (sig->version != 2 || xattr_len <= sizeof(*sig)) return; hash->algo = sig->hash_algo; break; case IMA_XATTR_DIGEST_NG: hash->algo = xattr_value->digest[0]; break; case IMA_XATTR_DIGEST: /* this is for backward compatibility */ if (xattr_len == 21) { unsigned int zero = 0; if (!memcmp(&xattr_value->digest[16], &zero, 4)) hash->algo = HASH_ALGO_MD5; else hash->algo = HASH_ALGO_SHA1; } else if (xattr_len == 17) hash->algo = HASH_ALGO_MD5; break; } } int ima_read_xattr(struct dentry *dentry, struct evm_ima_xattr_data **xattr_value) { struct inode *inode = dentry->d_inode; if (!inode->i_op->getxattr) return 0; return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, 0, GFP_NOFS); } /* * ima_appraise_measurement - appraise file measurement * * Call evm_verifyxattr() to verify the integrity of 'security.ima'. * Assuming success, compare the xattr hash with the collected measurement. * * Return 0 on success, error code otherwise */ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint, struct file *file, const unsigned char *filename, struct evm_ima_xattr_data *xattr_value, int xattr_len, int opened) { static const char op[] = "appraise_data"; char *cause = "unknown"; struct dentry *dentry = file->f_dentry; struct inode *inode = dentry->d_inode; enum integrity_status status = INTEGRITY_UNKNOWN; int rc = xattr_len, hash_start = 0; if (!inode->i_op->getxattr) return INTEGRITY_UNKNOWN; if (rc <= 0) { if (rc && rc != -ENODATA) goto out; cause = "missing-hash"; status = INTEGRITY_NOLABEL; if (opened & FILE_CREATED) { iint->flags |= IMA_NEW_FILE; status = INTEGRITY_PASS; } goto out; } status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) { if ((status == INTEGRITY_NOLABEL) || (status == INTEGRITY_NOXATTRS)) cause = "missing-HMAC"; else if (status == INTEGRITY_FAIL) cause = "invalid-HMAC"; goto out; } switch (xattr_value->type) { case IMA_XATTR_DIGEST_NG: /* first byte contains algorithm id */ hash_start = 1; case IMA_XATTR_DIGEST: if (iint->flags & IMA_DIGSIG_REQUIRED) { cause = "IMA-signature-required"; status = INTEGRITY_FAIL; break; } if (xattr_len - sizeof(xattr_value->type) - hash_start >= iint->ima_hash->length) /* xattr length may be longer. md5 hash in previous version occupied 20 bytes in xattr, instead of 16 */ rc = memcmp(&xattr_value->digest[hash_start], iint->ima_hash->digest, iint->ima_hash->length); else rc = -EINVAL; if (rc) { cause = "invalid-hash"; status = INTEGRITY_FAIL; break; } status = INTEGRITY_PASS; break; case EVM_IMA_XATTR_DIGSIG: iint->flags |= IMA_DIGSIG; rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, (const char *)xattr_value, rc, iint->ima_hash->digest, iint->ima_hash->length); if (rc == -EOPNOTSUPP) { status = INTEGRITY_UNKNOWN; } else if (rc) { cause = "invalid-signature"; status = INTEGRITY_FAIL; } else { status = INTEGRITY_PASS; } break; default: status = INTEGRITY_UNKNOWN; cause = "unknown-ima-data"; break; } out: if (status != INTEGRITY_PASS) { if ((ima_appraise & IMA_APPRAISE_FIX) && (!xattr_value || xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { if (!ima_fix_xattr(dentry, iint)) status = INTEGRITY_PASS; } integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, op, cause, rc, 0); } else { ima_cache_flags(iint, func); } ima_set_cache_status(iint, func, status); return status; } /* * ima_update_xattr - update 'security.ima' hash value */ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) { struct dentry *dentry = file->f_dentry; int rc = 0; /* do not collect and update hash for digital signatures */ if (iint->flags & IMA_DIGSIG) return; rc = ima_collect_measurement(iint, file, NULL, NULL); if (rc < 0) return; ima_fix_xattr(dentry, iint); } /** * ima_inode_post_setattr - reflect file metadata changes * @dentry: pointer to the affected dentry * * Changes to a dentry's metadata might result in needing to appraise. * * This function is called from notify_change(), which expects the caller * to lock the inode's i_mutex. */ void ima_inode_post_setattr(struct dentry *dentry) { struct inode *inode = dentry->d_inode; struct integrity_iint_cache *iint; int must_appraise, rc; if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) || !inode->i_op->removexattr) return; must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); iint = integrity_iint_find(inode); if (iint) { iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | IMA_ACTION_FLAGS); if (must_appraise) iint->flags |= IMA_APPRAISE; } if (!must_appraise) rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA); return; } /* * ima_protect_xattr - protect 'security.ima' * * Ensure that not just anyone can modify or remove 'security.ima'. */ static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, size_t xattr_value_len) { if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { if (!capable(CAP_SYS_ADMIN)) return -EPERM; return 1; } return 0; } static void ima_reset_appraise_flags(struct inode *inode, int digsig) { struct integrity_iint_cache *iint; if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) return; iint = integrity_iint_find(inode); if (!iint) return; iint->flags &= ~IMA_DONE_MASK; if (digsig) iint->flags |= IMA_DIGSIG; return; } int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, size_t xattr_value_len) { const struct evm_ima_xattr_data *xvalue = xattr_value; int result; result = ima_protect_xattr(dentry, xattr_name, xattr_value, xattr_value_len); if (result == 1) { if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) return -EINVAL; ima_reset_appraise_flags(dentry->d_inode, (xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0); result = 0; } return result; } int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) { int result; result = ima_protect_xattr(dentry, xattr_name, NULL, 0); if (result == 1) { ima_reset_appraise_flags(dentry->d_inode, 0); result = 0; } return result; }