| /* |
| * Copyright (C) 2005-2010 IBM Corporation |
| * |
| * Author: |
| * Mimi Zohar <zohar@us.ibm.com> |
| * Kylene Hall <kjhall@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. |
| * |
| * File: evm_main.c |
| * implements evm_inode_setxattr, evm_inode_post_setxattr, |
| * evm_inode_removexattr, and evm_verifyxattr |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/crypto.h> |
| #include <linux/xattr.h> |
| #include <linux/integrity.h> |
| #include <linux/evm.h> |
| #include <crypto/hash.h> |
| #include "evm.h" |
| |
| int evm_initialized; |
| |
| char *evm_hmac = "hmac(sha1)"; |
| |
| char *evm_config_xattrnames[] = { |
| #ifdef CONFIG_SECURITY_SELINUX |
| XATTR_NAME_SELINUX, |
| #endif |
| #ifdef CONFIG_SECURITY_SMACK |
| XATTR_NAME_SMACK, |
| #endif |
| XATTR_NAME_CAPS, |
| NULL |
| }; |
| |
| static int evm_fixmode; |
| static int __init evm_set_fixmode(char *str) |
| { |
| if (strncmp(str, "fix", 3) == 0) |
| evm_fixmode = 1; |
| return 0; |
| } |
| __setup("evm=", evm_set_fixmode); |
| |
| /* |
| * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr |
| * |
| * Compute the HMAC on the dentry's protected set of extended attributes |
| * and compare it against the stored security.evm xattr. |
| * |
| * For performance: |
| * - use the previoulsy retrieved xattr value and length to calculate the |
| * HMAC.) |
| * - cache the verification result in the iint, when available. |
| * |
| * Returns integrity status |
| */ |
| static enum integrity_status evm_verify_hmac(struct dentry *dentry, |
| const char *xattr_name, |
| char *xattr_value, |
| size_t xattr_value_len, |
| struct integrity_iint_cache *iint) |
| { |
| struct evm_ima_xattr_data xattr_data; |
| enum integrity_status evm_status = INTEGRITY_PASS; |
| int rc; |
| |
| if (iint && iint->evm_status == INTEGRITY_PASS) |
| return iint->evm_status; |
| |
| /* if status is not PASS, try to check again - against -ENOMEM */ |
| |
| rc = evm_calc_hmac(dentry, xattr_name, xattr_value, |
| xattr_value_len, xattr_data.digest); |
| if (rc < 0) { |
| evm_status = (rc == -ENODATA) |
| ? INTEGRITY_NOXATTRS : INTEGRITY_FAIL; |
| goto out; |
| } |
| |
| xattr_data.type = EVM_XATTR_HMAC; |
| rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data, |
| sizeof xattr_data, GFP_NOFS); |
| if (rc < 0) |
| evm_status = (rc == -ENODATA) |
| ? INTEGRITY_NOLABEL : INTEGRITY_FAIL; |
| out: |
| if (iint) |
| iint->evm_status = evm_status; |
| return evm_status; |
| } |
| |
| static int evm_protected_xattr(const char *req_xattr_name) |
| { |
| char **xattrname; |
| int namelen; |
| int found = 0; |
| |
| namelen = strlen(req_xattr_name); |
| for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) { |
| if ((strlen(*xattrname) == namelen) |
| && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) { |
| found = 1; |
| break; |
| } |
| if (strncmp(req_xattr_name, |
| *xattrname + XATTR_SECURITY_PREFIX_LEN, |
| strlen(req_xattr_name)) == 0) { |
| found = 1; |
| break; |
| } |
| } |
| return found; |
| } |
| |
| /** |
| * evm_verifyxattr - verify the integrity of the requested xattr |
| * @dentry: object of the verify xattr |
| * @xattr_name: requested xattr |
| * @xattr_value: requested xattr value |
| * @xattr_value_len: requested xattr value length |
| * |
| * Calculate the HMAC for the given dentry and verify it against the stored |
| * security.evm xattr. For performance, use the xattr value and length |
| * previously retrieved to calculate the HMAC. |
| * |
| * Returns the xattr integrity status. |
| * |
| * This function requires the caller to lock the inode's i_mutex before it |
| * is executed. |
| */ |
| enum integrity_status evm_verifyxattr(struct dentry *dentry, |
| const char *xattr_name, |
| void *xattr_value, size_t xattr_value_len, |
| struct integrity_iint_cache *iint) |
| { |
| if (!evm_initialized || !evm_protected_xattr(xattr_name)) |
| return INTEGRITY_UNKNOWN; |
| |
| if (!iint) { |
| iint = integrity_iint_find(dentry->d_inode); |
| if (!iint) |
| return INTEGRITY_UNKNOWN; |
| } |
| return evm_verify_hmac(dentry, xattr_name, xattr_value, |
| xattr_value_len, iint); |
| } |
| EXPORT_SYMBOL_GPL(evm_verifyxattr); |
| |
| /* |
| * evm_verify_current_integrity - verify the dentry's metadata integrity |
| * @dentry: pointer to the affected dentry |
| * |
| * Verify and return the dentry's metadata integrity. The exceptions are |
| * before EVM is initialized or in 'fix' mode. |
| */ |
| static enum integrity_status evm_verify_current_integrity(struct dentry *dentry) |
| { |
| struct inode *inode = dentry->d_inode; |
| |
| if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode) |
| return 0; |
| return evm_verify_hmac(dentry, NULL, NULL, 0, NULL); |
| } |
| |
| /* |
| * evm_protect_xattr - protect the EVM extended attribute |
| * |
| * Prevent security.evm from being modified or removed without the |
| * necessary permissions or when the existing value is invalid. |
| * |
| * The posix xattr acls are 'system' prefixed, which normally would not |
| * affect security.evm. An interesting side affect of writing posix xattr |
| * acls is their modifying of the i_mode, which is included in security.evm. |
| * For posix xattr acls only, permit security.evm, even if it currently |
| * doesn't exist, to be updated. |
| */ |
| static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, |
| const void *xattr_value, size_t xattr_value_len) |
| { |
| enum integrity_status evm_status; |
| |
| if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { |
| if (!capable(CAP_SYS_ADMIN)) |
| return -EPERM; |
| } else if (!evm_protected_xattr(xattr_name)) { |
| if (!posix_xattr_acl(xattr_name)) |
| return 0; |
| evm_status = evm_verify_current_integrity(dentry); |
| if ((evm_status == INTEGRITY_PASS) || |
| (evm_status == INTEGRITY_NOXATTRS)) |
| return 0; |
| return -EPERM; |
| } |
| evm_status = evm_verify_current_integrity(dentry); |
| return evm_status == INTEGRITY_PASS ? 0 : -EPERM; |
| } |
| |
| /** |
| * evm_inode_setxattr - protect the EVM extended attribute |
| * @dentry: pointer to the affected dentry |
| * @xattr_name: pointer to the affected extended attribute name |
| * @xattr_value: pointer to the new extended attribute value |
| * @xattr_value_len: pointer to the new extended attribute value length |
| * |
| * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that |
| * the current value is valid. |
| */ |
| int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name, |
| const void *xattr_value, size_t xattr_value_len) |
| { |
| return evm_protect_xattr(dentry, xattr_name, xattr_value, |
| xattr_value_len); |
| } |
| |
| /** |
| * evm_inode_removexattr - protect the EVM extended attribute |
| * @dentry: pointer to the affected dentry |
| * @xattr_name: pointer to the affected extended attribute name |
| * |
| * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that |
| * the current value is valid. |
| */ |
| int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name) |
| { |
| return evm_protect_xattr(dentry, xattr_name, NULL, 0); |
| } |
| |
| /** |
| * evm_inode_post_setxattr - update 'security.evm' to reflect the changes |
| * @dentry: pointer to the affected dentry |
| * @xattr_name: pointer to the affected extended attribute name |
| * @xattr_value: pointer to the new extended attribute value |
| * @xattr_value_len: pointer to the new extended attribute value length |
| * |
| * Update the HMAC stored in 'security.evm' to reflect the change. |
| * |
| * No need to take the i_mutex lock here, as this function is called from |
| * __vfs_setxattr_noperm(). The caller of which has taken the inode's |
| * i_mutex lock. |
| */ |
| void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, |
| const void *xattr_value, size_t xattr_value_len) |
| { |
| if (!evm_initialized || (!evm_protected_xattr(xattr_name) |
| && !posix_xattr_acl(xattr_name))) |
| return; |
| |
| evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len); |
| return; |
| } |
| |
| /** |
| * evm_inode_post_removexattr - update 'security.evm' after removing the xattr |
| * @dentry: pointer to the affected dentry |
| * @xattr_name: pointer to the affected extended attribute name |
| * |
| * Update the HMAC stored in 'security.evm' to reflect removal of the xattr. |
| */ |
| void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) |
| { |
| struct inode *inode = dentry->d_inode; |
| |
| if (!evm_initialized || !evm_protected_xattr(xattr_name)) |
| return; |
| |
| mutex_lock(&inode->i_mutex); |
| evm_update_evmxattr(dentry, xattr_name, NULL, 0); |
| mutex_unlock(&inode->i_mutex); |
| return; |
| } |
| |
| /** |
| * evm_inode_setattr - prevent updating an invalid EVM extended attribute |
| * @dentry: pointer to the affected dentry |
| */ |
| int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) |
| { |
| unsigned int ia_valid = attr->ia_valid; |
| enum integrity_status evm_status; |
| |
| if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))) |
| return 0; |
| evm_status = evm_verify_current_integrity(dentry); |
| if ((evm_status == INTEGRITY_PASS) || |
| (evm_status == INTEGRITY_NOXATTRS)) |
| return 0; |
| return -EPERM; |
| } |
| |
| /** |
| * evm_inode_post_setattr - update 'security.evm' after modifying metadata |
| * @dentry: pointer to the affected dentry |
| * @ia_valid: for the UID and GID status |
| * |
| * For now, update the HMAC stored in 'security.evm' to reflect UID/GID |
| * changes. |
| * |
| * This function is called from notify_change(), which expects the caller |
| * to lock the inode's i_mutex. |
| */ |
| void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) |
| { |
| if (!evm_initialized) |
| return; |
| |
| if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) |
| evm_update_evmxattr(dentry, NULL, NULL, 0); |
| return; |
| } |
| |
| /* |
| * evm_inode_init_security - initializes security.evm |
| */ |
| int evm_inode_init_security(struct inode *inode, |
| const struct xattr *lsm_xattr, |
| struct xattr *evm_xattr) |
| { |
| struct evm_ima_xattr_data *xattr_data; |
| int rc; |
| |
| if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name)) |
| return 0; |
| |
| xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); |
| if (!xattr_data) |
| return -ENOMEM; |
| |
| xattr_data->type = EVM_XATTR_HMAC; |
| rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest); |
| if (rc < 0) |
| goto out; |
| |
| evm_xattr->value = xattr_data; |
| evm_xattr->value_len = sizeof(*xattr_data); |
| evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS); |
| return 0; |
| out: |
| kfree(xattr_data); |
| return rc; |
| } |
| EXPORT_SYMBOL_GPL(evm_inode_init_security); |
| |
| static int __init init_evm(void) |
| { |
| int error; |
| |
| error = evm_init_secfs(); |
| if (error < 0) { |
| printk(KERN_INFO "EVM: Error registering secfs\n"); |
| goto err; |
| } |
| err: |
| return error; |
| } |
| |
| static void __exit cleanup_evm(void) |
| { |
| evm_cleanup_secfs(); |
| if (hmac_tfm) |
| crypto_free_shash(hmac_tfm); |
| } |
| |
| /* |
| * evm_display_config - list the EVM protected security extended attributes |
| */ |
| static int __init evm_display_config(void) |
| { |
| char **xattrname; |
| |
| for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) |
| printk(KERN_INFO "EVM: %s\n", *xattrname); |
| return 0; |
| } |
| |
| pure_initcall(evm_display_config); |
| late_initcall(init_evm); |
| |
| MODULE_DESCRIPTION("Extended Verification Module"); |
| MODULE_LICENSE("GPL"); |