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- /*
- * 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 "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, NULL);
- }
- 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,
- enum ima_hooks func)
- {
- switch (func) {
- case MMAP_CHECK:
- return iint->ima_mmap_status;
- case BPRM_CHECK:
- return iint->ima_bprm_status;
- case FILE_CHECK:
- case POST_SETATTR:
- return iint->ima_file_status;
- case MODULE_CHECK ... MAX_CHECK - 1:
- default:
- return iint->ima_read_status;
- }
- }
- static void ima_set_cache_status(struct integrity_iint_cache *iint,
- enum ima_hooks 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 FILE_CHECK:
- case POST_SETATTR:
- iint->ima_file_status = status;
- break;
- case MODULE_CHECK ... MAX_CHECK - 1:
- default:
- iint->ima_read_status = status;
- break;
- }
- }
- static void ima_cache_flags(struct integrity_iint_cache *iint,
- enum ima_hooks 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 FILE_CHECK:
- case POST_SETATTR:
- iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
- break;
- case MODULE_CHECK ... MAX_CHECK - 1:
- default:
- iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
- break;
- }
- }
- enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
- int xattr_len)
- {
- struct signature_v2_hdr *sig;
- if (!xattr_value || xattr_len < 2)
- /* return default hash algo */
- return ima_hash_algo;
- switch (xattr_value->type) {
- case EVM_IMA_XATTR_DIGSIG:
- sig = (typeof(sig))xattr_value;
- if (sig->version != 2 || xattr_len <= sizeof(*sig))
- return ima_hash_algo;
- return sig->hash_algo;
- break;
- case IMA_XATTR_DIGEST_NG:
- return 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))
- return HASH_ALGO_MD5;
- else
- return HASH_ALGO_SHA1;
- } else if (xattr_len == 17)
- return HASH_ALGO_MD5;
- break;
- }
- /* return default hash algo */
- return ima_hash_algo;
- }
- int ima_read_xattr(struct dentry *dentry,
- struct evm_ima_xattr_data **xattr_value)
- {
- ssize_t ret;
- ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
- 0, GFP_NOFS);
- if (ret == -EOPNOTSUPP)
- ret = 0;
- return ret;
- }
- /*
- * 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(enum ima_hooks 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_dentry(file);
- struct inode *inode = d_backing_inode(dentry);
- enum integrity_status status = INTEGRITY_UNKNOWN;
- int rc = xattr_len, hash_start = 0;
- if (!(inode->i_opflags & IOP_XATTR))
- 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;
- if ((iint->flags & IMA_NEW_FILE) &&
- (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
- (inode->i_size == 0)))
- 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;
- } else if ((inode->i_size == 0) &&
- (iint->flags & IMA_NEW_FILE) &&
- (xattr_value &&
- xattr_value->type == EVM_IMA_XATTR_DIGSIG)) {
- 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_dentry(file);
- int rc = 0;
- /* do not collect and update hash for digital signatures */
- if (iint->flags & IMA_DIGSIG)
- return;
- if (iint->ima_file_status != INTEGRITY_PASS)
- return;
- rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
- 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 = d_backing_inode(dentry);
- struct integrity_iint_cache *iint;
- int must_appraise;
- if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
- || !(inode->i_opflags & IOP_XATTR))
- 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_RULE_FLAGS);
- if (must_appraise)
- iint->flags |= IMA_APPRAISE;
- }
- if (!must_appraise)
- __vfs_removexattr(dentry, XATTR_NAME_IMA);
- }
- /*
- * 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;
- iint->measured_pcrs = 0;
- 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(d_backing_inode(dentry),
- (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(d_backing_inode(dentry), 0);
- result = 0;
- }
- return result;
- }
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