diff options
Diffstat (limited to '')
| -rw-r--r-- | security/integrity/evm/evm_secfs.c | 334 |
1 files changed, 334 insertions, 0 deletions
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c new file mode 100644 index 000000000..8a9db7dfc --- /dev/null +++ b/security/integrity/evm/evm_secfs.c @@ -0,0 +1,334 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2010 IBM Corporation + * + * Authors: + * Mimi Zohar <zohar@us.ibm.com> + * + * File: evm_secfs.c + * - Used to signal when key is on keyring + * - Get the key and enable EVM + */ + +#include <linux/audit.h> +#include <linux/uaccess.h> +#include <linux/init.h> +#include <linux/mutex.h> +#include "evm.h" + +static struct dentry *evm_dir; +static struct dentry *evm_init_tpm; +static struct dentry *evm_symlink; + +#ifdef CONFIG_EVM_ADD_XATTRS +static struct dentry *evm_xattrs; +static DEFINE_MUTEX(xattr_list_mutex); +static int evm_xattrs_locked; +#endif + +/** + * evm_read_key - read() for <securityfs>/evm + * + * @filp: file pointer, not actually used + * @buf: where to put the result + * @count: maximum to send along + * @ppos: where to start + * + * Returns number of bytes read or error code, as appropriate + */ +static ssize_t evm_read_key(struct file *filp, char __user *buf, + size_t count, loff_t *ppos) +{ + char temp[80]; + ssize_t rc; + + if (*ppos != 0) + return 0; + + sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE)); + rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); + + return rc; +} + +/** + * evm_write_key - write() for <securityfs>/evm + * @file: file pointer, not actually used + * @buf: where to get the data from + * @count: bytes sent + * @ppos: where to start + * + * Used to signal that key is on the kernel key ring. + * - get the integrity hmac key from the kernel key ring + * - create list of hmac protected extended attributes + * Returns number of bytes written or error code, as appropriate + */ +static ssize_t evm_write_key(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + unsigned int i; + int ret; + + if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE)) + return -EPERM; + + ret = kstrtouint_from_user(buf, count, 0, &i); + + if (ret) + return ret; + + /* Reject invalid values */ + if (!i || (i & ~EVM_INIT_MASK) != 0) + return -EINVAL; + + /* + * Don't allow a request to enable metadata writes if + * an HMAC key is loaded. + */ + if ((i & EVM_ALLOW_METADATA_WRITES) && + (evm_initialized & EVM_INIT_HMAC) != 0) + return -EPERM; + + if (i & EVM_INIT_HMAC) { + ret = evm_init_key(); + if (ret != 0) + return ret; + /* Forbid further writes after the symmetric key is loaded */ + i |= EVM_SETUP_COMPLETE; + } + + evm_initialized |= i; + + /* Don't allow protected metadata modification if a symmetric key + * is loaded + */ + if (evm_initialized & EVM_INIT_HMAC) + evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES); + + return count; +} + +static const struct file_operations evm_key_ops = { + .read = evm_read_key, + .write = evm_write_key, +}; + +#ifdef CONFIG_EVM_ADD_XATTRS +/** + * evm_read_xattrs - read() for <securityfs>/evm_xattrs + * + * @filp: file pointer, not actually used + * @buf: where to put the result + * @count: maximum to send along + * @ppos: where to start + * + * Returns number of bytes read or error code, as appropriate + */ +static ssize_t evm_read_xattrs(struct file *filp, char __user *buf, + size_t count, loff_t *ppos) +{ + char *temp; + int offset = 0; + ssize_t rc, size = 0; + struct xattr_list *xattr; + + if (*ppos != 0) + return 0; + + rc = mutex_lock_interruptible(&xattr_list_mutex); + if (rc) + return -ERESTARTSYS; + + list_for_each_entry(xattr, &evm_config_xattrnames, list) { + if (!xattr->enabled) + continue; + + size += strlen(xattr->name) + 1; + } + + temp = kmalloc(size + 1, GFP_KERNEL); + if (!temp) { + mutex_unlock(&xattr_list_mutex); + return -ENOMEM; + } + + list_for_each_entry(xattr, &evm_config_xattrnames, list) { + if (!xattr->enabled) + continue; + + sprintf(temp + offset, "%s\n", xattr->name); + offset += strlen(xattr->name) + 1; + } + + mutex_unlock(&xattr_list_mutex); + rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); + + kfree(temp); + + return rc; +} + +/** + * evm_write_xattrs - write() for <securityfs>/evm_xattrs + * @file: file pointer, not actually used + * @buf: where to get the data from + * @count: bytes sent + * @ppos: where to start + * + * Returns number of bytes written or error code, as appropriate + */ +static ssize_t evm_write_xattrs(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + int len, err; + struct xattr_list *xattr, *tmp; + struct audit_buffer *ab; + struct iattr newattrs; + struct inode *inode; + + if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked) + return -EPERM; + + if (*ppos != 0) + return -EINVAL; + + if (count > XATTR_NAME_MAX) + return -E2BIG; + + ab = audit_log_start(audit_context(), GFP_KERNEL, + AUDIT_INTEGRITY_EVM_XATTR); + if (!ab && IS_ENABLED(CONFIG_AUDIT)) + return -ENOMEM; + + xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL); + if (!xattr) { + err = -ENOMEM; + goto out; + } + + xattr->enabled = true; + xattr->name = memdup_user_nul(buf, count); + if (IS_ERR(xattr->name)) { + err = PTR_ERR(xattr->name); + xattr->name = NULL; + goto out; + } + + /* Remove any trailing newline */ + len = strlen(xattr->name); + if (len && xattr->name[len-1] == '\n') + xattr->name[len-1] = '\0'; + + audit_log_format(ab, "xattr="); + audit_log_untrustedstring(ab, xattr->name); + + if (strcmp(xattr->name, ".") == 0) { + evm_xattrs_locked = 1; + newattrs.ia_mode = S_IFREG | 0440; + newattrs.ia_valid = ATTR_MODE; + inode = evm_xattrs->d_inode; + inode_lock(inode); + err = simple_setattr(&init_user_ns, evm_xattrs, &newattrs); + inode_unlock(inode); + if (!err) + err = count; + goto out; + } + + if (strncmp(xattr->name, XATTR_SECURITY_PREFIX, + XATTR_SECURITY_PREFIX_LEN) != 0) { + err = -EINVAL; + goto out; + } + + /* + * xattr_list_mutex guards against races in evm_read_xattrs(). + * Entries are only added to the evm_config_xattrnames list + * and never deleted. Therefore, the list is traversed + * using list_for_each_entry_lockless() without holding + * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs() + * and evm_protected_xattr(). + */ + mutex_lock(&xattr_list_mutex); + list_for_each_entry(tmp, &evm_config_xattrnames, list) { + if (strcmp(xattr->name, tmp->name) == 0) { + err = -EEXIST; + if (!tmp->enabled) { + tmp->enabled = true; + err = count; + } + mutex_unlock(&xattr_list_mutex); + goto out; + } + } + list_add_tail_rcu(&xattr->list, &evm_config_xattrnames); + mutex_unlock(&xattr_list_mutex); + + audit_log_format(ab, " res=0"); + audit_log_end(ab); + return count; +out: + audit_log_format(ab, " res=%d", (err < 0) ? err : 0); + audit_log_end(ab); + if (xattr) { + kfree(xattr->name); + kfree(xattr); + } + return err; +} + +static const struct file_operations evm_xattr_ops = { + .read = evm_read_xattrs, + .write = evm_write_xattrs, +}; + +static int evm_init_xattrs(void) +{ + evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL, + &evm_xattr_ops); + if (!evm_xattrs || IS_ERR(evm_xattrs)) + return -EFAULT; + + return 0; +} +#else +static int evm_init_xattrs(void) +{ + return 0; +} +#endif + +int __init evm_init_secfs(void) +{ + int error = 0; + + evm_dir = securityfs_create_dir("evm", integrity_dir); + if (!evm_dir || IS_ERR(evm_dir)) + return -EFAULT; + + evm_init_tpm = securityfs_create_file("evm", 0660, + evm_dir, NULL, &evm_key_ops); + if (!evm_init_tpm || IS_ERR(evm_init_tpm)) { + error = -EFAULT; + goto out; + } + + evm_symlink = securityfs_create_symlink("evm", NULL, + "integrity/evm/evm", NULL); + if (!evm_symlink || IS_ERR(evm_symlink)) { + error = -EFAULT; + goto out; + } + + if (evm_init_xattrs() != 0) { + error = -EFAULT; + goto out; + } + + return 0; +out: + securityfs_remove(evm_symlink); + securityfs_remove(evm_init_tpm); + securityfs_remove(evm_dir); + return error; +} |