diff options
Diffstat (limited to 'security/integrity/evm/evm_main.c')
| -rw-r--r-- | security/integrity/evm/evm_main.c | 963 |
1 files changed, 963 insertions, 0 deletions
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c new file mode 100644 index 0000000000..ff9a939dad --- /dev/null +++ b/security/integrity/evm/evm_main.c @@ -0,0 +1,963 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2005-2010 IBM Corporation + * + * Author: + * Mimi Zohar <zohar@us.ibm.com> + * Kylene Hall <kjhall@us.ibm.com> + * + * File: evm_main.c + * implements evm_inode_setxattr, evm_inode_post_setxattr, + * evm_inode_removexattr, evm_verifyxattr, and evm_inode_set_acl. + */ + +#define pr_fmt(fmt) "EVM: "fmt + +#include <linux/init.h> +#include <linux/crypto.h> +#include <linux/audit.h> +#include <linux/xattr.h> +#include <linux/integrity.h> +#include <linux/evm.h> +#include <linux/magic.h> +#include <linux/posix_acl_xattr.h> +#include <linux/lsm_hooks.h> + +#include <crypto/hash.h> +#include <crypto/hash_info.h> +#include <crypto/algapi.h> +#include "evm.h" + +int evm_initialized; + +static const char * const integrity_status_msg[] = { + "pass", "pass_immutable", "fail", "fail_immutable", "no_label", + "no_xattrs", "unknown" +}; +int evm_hmac_attrs; + +static struct xattr_list evm_config_default_xattrnames[] = { + { + .name = XATTR_NAME_SELINUX, + .enabled = IS_ENABLED(CONFIG_SECURITY_SELINUX) + }, + { + .name = XATTR_NAME_SMACK, + .enabled = IS_ENABLED(CONFIG_SECURITY_SMACK) + }, + { + .name = XATTR_NAME_SMACKEXEC, + .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS) + }, + { + .name = XATTR_NAME_SMACKTRANSMUTE, + .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS) + }, + { + .name = XATTR_NAME_SMACKMMAP, + .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS) + }, + { + .name = XATTR_NAME_APPARMOR, + .enabled = IS_ENABLED(CONFIG_SECURITY_APPARMOR) + }, + { + .name = XATTR_NAME_IMA, + .enabled = IS_ENABLED(CONFIG_IMA_APPRAISE) + }, + { + .name = XATTR_NAME_CAPS, + .enabled = true + }, +}; + +LIST_HEAD(evm_config_xattrnames); + +static int evm_fixmode __ro_after_init; +static int __init evm_set_fixmode(char *str) +{ + if (strncmp(str, "fix", 3) == 0) + evm_fixmode = 1; + else + pr_err("invalid \"%s\" mode", str); + + return 1; +} +__setup("evm=", evm_set_fixmode); + +static void __init evm_init_config(void) +{ + int i, xattrs; + + xattrs = ARRAY_SIZE(evm_config_default_xattrnames); + + pr_info("Initialising EVM extended attributes:\n"); + for (i = 0; i < xattrs; i++) { + pr_info("%s%s\n", evm_config_default_xattrnames[i].name, + !evm_config_default_xattrnames[i].enabled ? + " (disabled)" : ""); + list_add_tail(&evm_config_default_xattrnames[i].list, + &evm_config_xattrnames); + } + +#ifdef CONFIG_EVM_ATTR_FSUUID + evm_hmac_attrs |= EVM_ATTR_FSUUID; +#endif + pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs); +} + +static bool evm_key_loaded(void) +{ + return (bool)(evm_initialized & EVM_KEY_MASK); +} + +/* + * This function determines whether or not it is safe to ignore verification + * errors, based on the ability of EVM to calculate HMACs. If the HMAC key + * is not loaded, and it cannot be loaded in the future due to the + * EVM_SETUP_COMPLETE initialization flag, allowing an operation despite the + * attrs/xattrs being found invalid will not make them valid. + */ +static bool evm_hmac_disabled(void) +{ + if (evm_initialized & EVM_INIT_HMAC) + return false; + + if (!(evm_initialized & EVM_SETUP_COMPLETE)) + return false; + + return true; +} + +static int evm_find_protected_xattrs(struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + struct xattr_list *xattr; + int error; + int count = 0; + + if (!(inode->i_opflags & IOP_XATTR)) + return -EOPNOTSUPP; + + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { + error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0); + if (error < 0) { + if (error == -ENODATA) + continue; + return error; + } + count++; + } + + return count; +} + +/* + * 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 = NULL; + struct signature_v2_hdr *hdr; + enum integrity_status evm_status = INTEGRITY_PASS; + struct evm_digest digest; + struct inode *inode; + int rc, xattr_len, evm_immutable = 0; + + if (iint && (iint->evm_status == INTEGRITY_PASS || + iint->evm_status == INTEGRITY_PASS_IMMUTABLE)) + return iint->evm_status; + + /* if status is not PASS, try to check again - against -ENOMEM */ + + /* first need to know the sig type */ + rc = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_EVM, + (char **)&xattr_data, 0, GFP_NOFS); + if (rc <= 0) { + evm_status = INTEGRITY_FAIL; + if (rc == -ENODATA) { + rc = evm_find_protected_xattrs(dentry); + if (rc > 0) + evm_status = INTEGRITY_NOLABEL; + else if (rc == 0) + evm_status = INTEGRITY_NOXATTRS; /* new file */ + } else if (rc == -EOPNOTSUPP) { + evm_status = INTEGRITY_UNKNOWN; + } + goto out; + } + + xattr_len = rc; + + /* check value type */ + switch (xattr_data->type) { + case EVM_XATTR_HMAC: + if (xattr_len != sizeof(struct evm_xattr)) { + evm_status = INTEGRITY_FAIL; + goto out; + } + + digest.hdr.algo = HASH_ALGO_SHA1; + rc = evm_calc_hmac(dentry, xattr_name, xattr_value, + xattr_value_len, &digest); + if (rc) + break; + rc = crypto_memneq(xattr_data->data, digest.digest, + SHA1_DIGEST_SIZE); + if (rc) + rc = -EINVAL; + break; + case EVM_XATTR_PORTABLE_DIGSIG: + evm_immutable = 1; + fallthrough; + case EVM_IMA_XATTR_DIGSIG: + /* accept xattr with non-empty signature field */ + if (xattr_len <= sizeof(struct signature_v2_hdr)) { + evm_status = INTEGRITY_FAIL; + goto out; + } + + hdr = (struct signature_v2_hdr *)xattr_data; + digest.hdr.algo = hdr->hash_algo; + rc = evm_calc_hash(dentry, xattr_name, xattr_value, + xattr_value_len, xattr_data->type, &digest); + if (rc) + break; + rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, + (const char *)xattr_data, xattr_len, + digest.digest, digest.hdr.length); + if (!rc) { + inode = d_backing_inode(dentry); + + if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) { + if (iint) + iint->flags |= EVM_IMMUTABLE_DIGSIG; + evm_status = INTEGRITY_PASS_IMMUTABLE; + } else if (!IS_RDONLY(inode) && + !(inode->i_sb->s_readonly_remount) && + !IS_IMMUTABLE(inode)) { + evm_update_evmxattr(dentry, xattr_name, + xattr_value, + xattr_value_len); + } + } + break; + default: + rc = -EINVAL; + break; + } + + if (rc) { + if (rc == -ENODATA) + evm_status = INTEGRITY_NOXATTRS; + else if (evm_immutable) + evm_status = INTEGRITY_FAIL_IMMUTABLE; + else + evm_status = INTEGRITY_FAIL; + } + pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length, + digest.digest); +out: + if (iint) + iint->evm_status = evm_status; + kfree(xattr_data); + return evm_status; +} + +static int evm_protected_xattr_common(const char *req_xattr_name, + bool all_xattrs) +{ + int namelen; + int found = 0; + struct xattr_list *xattr; + + namelen = strlen(req_xattr_name); + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { + if (!all_xattrs && !xattr->enabled) + continue; + + if ((strlen(xattr->name) == namelen) + && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) { + found = 1; + break; + } + if (strncmp(req_xattr_name, + xattr->name + XATTR_SECURITY_PREFIX_LEN, + strlen(req_xattr_name)) == 0) { + found = 1; + break; + } + } + + return found; +} + +int evm_protected_xattr(const char *req_xattr_name) +{ + return evm_protected_xattr_common(req_xattr_name, false); +} + +int evm_protected_xattr_if_enabled(const char *req_xattr_name) +{ + return evm_protected_xattr_common(req_xattr_name, true); +} + +/** + * evm_read_protected_xattrs - read EVM protected xattr names, lengths, values + * @dentry: dentry of the read xattrs + * @buffer: buffer xattr names, lengths or values are copied to + * @buffer_size: size of buffer + * @type: n: names, l: lengths, v: values + * @canonical_fmt: data format (true: little endian, false: native format) + * + * Read protected xattr names (separated by |), lengths (u32) or values for a + * given dentry and return the total size of copied data. If buffer is NULL, + * just return the total size. + * + * Returns the total size on success, a negative value on error. + */ +int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer, + int buffer_size, char type, bool canonical_fmt) +{ + struct xattr_list *xattr; + int rc, size, total_size = 0; + + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { + rc = __vfs_getxattr(dentry, d_backing_inode(dentry), + xattr->name, NULL, 0); + if (rc < 0 && rc == -ENODATA) + continue; + else if (rc < 0) + return rc; + + switch (type) { + case 'n': + size = strlen(xattr->name) + 1; + if (buffer) { + if (total_size) + *(buffer + total_size - 1) = '|'; + + memcpy(buffer + total_size, xattr->name, size); + } + break; + case 'l': + size = sizeof(u32); + if (buffer) { + if (canonical_fmt) + rc = (__force int)cpu_to_le32(rc); + + *(u32 *)(buffer + total_size) = rc; + } + break; + case 'v': + size = rc; + if (buffer) { + rc = __vfs_getxattr(dentry, + d_backing_inode(dentry), xattr->name, + buffer + total_size, + buffer_size - total_size); + if (rc < 0) + return rc; + } + break; + default: + return -EINVAL; + } + + total_size += size; + } + + return total_size; +} + +/** + * 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 + * @iint: inode integrity metadata + * + * 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_key_loaded() || !evm_protected_xattr(xattr_name)) + return INTEGRITY_UNKNOWN; + + if (!iint) { + iint = integrity_iint_find(d_backing_inode(dentry)); + 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 = d_backing_inode(dentry); + + if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode) + return INTEGRITY_PASS; + return evm_verify_hmac(dentry, NULL, NULL, 0, NULL); +} + +/* + * evm_xattr_change - check if passed xattr value differs from current value + * @idmap: idmap of the mount + * @dentry: pointer to the affected dentry + * @xattr_name: requested xattr + * @xattr_value: requested xattr value + * @xattr_value_len: requested xattr value length + * + * Check if passed xattr value differs from current value. + * + * Returns 1 if passed xattr value differs from current value, 0 otherwise. + */ +static int evm_xattr_change(struct mnt_idmap *idmap, + struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + char *xattr_data = NULL; + int rc = 0; + + rc = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, xattr_name, &xattr_data, + 0, GFP_NOFS); + if (rc < 0) { + rc = 1; + goto out; + } + + if (rc == xattr_value_len) + rc = !!memcmp(xattr_value, xattr_data, rc); + else + rc = 1; + +out: + kfree(xattr_data); + return rc; +} + +/* + * 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 unless the EVM signature is immutable. + */ +static int evm_protect_xattr(struct mnt_idmap *idmap, + 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; + goto out; + } + + evm_status = evm_verify_current_integrity(dentry); + if (evm_status == INTEGRITY_NOXATTRS) { + struct integrity_iint_cache *iint; + + /* Exception if the HMAC is not going to be calculated. */ + if (evm_hmac_disabled()) + return 0; + + iint = integrity_iint_find(d_backing_inode(dentry)); + if (iint && (iint->flags & IMA_NEW_FILE)) + return 0; + + /* exception for pseudo filesystems */ + if (dentry->d_sb->s_magic == TMPFS_MAGIC + || dentry->d_sb->s_magic == SYSFS_MAGIC) + return 0; + + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, + dentry->d_inode, dentry->d_name.name, + "update_metadata", + integrity_status_msg[evm_status], + -EPERM, 0); + } +out: + /* Exception if the HMAC is not going to be calculated. */ + if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL || + evm_status == INTEGRITY_UNKNOWN)) + return 0; + + /* + * Writing other xattrs is safe for portable signatures, as portable + * signatures are immutable and can never be updated. + */ + if (evm_status == INTEGRITY_FAIL_IMMUTABLE) + return 0; + + if (evm_status == INTEGRITY_PASS_IMMUTABLE && + !evm_xattr_change(idmap, dentry, xattr_name, xattr_value, + xattr_value_len)) + return 0; + + if (evm_status != INTEGRITY_PASS && + evm_status != INTEGRITY_PASS_IMMUTABLE) + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), + dentry->d_name.name, "appraise_metadata", + integrity_status_msg[evm_status], + -EPERM, 0); + return evm_status == INTEGRITY_PASS ? 0 : -EPERM; +} + +/** + * evm_inode_setxattr - protect the EVM extended attribute + * @idmap: idmap of the mount + * @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 + * + * Before allowing the 'security.evm' protected xattr to be updated, + * verify the existing value is valid. As only the kernel should have + * access to the EVM encrypted key needed to calculate the HMAC, prevent + * userspace from writing HMAC value. Writing 'security.evm' requires + * requires CAP_SYS_ADMIN privileges. + */ +int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, + const char *xattr_name, const void *xattr_value, + size_t xattr_value_len) +{ + const struct evm_ima_xattr_data *xattr_data = xattr_value; + + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { + if (!xattr_value_len) + return -EINVAL; + if (xattr_data->type != EVM_IMA_XATTR_DIGSIG && + xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG) + return -EPERM; + } + return evm_protect_xattr(idmap, dentry, xattr_name, xattr_value, + xattr_value_len); +} + +/** + * evm_inode_removexattr - protect the EVM extended attribute + * @idmap: idmap of the mount + * @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 mnt_idmap *idmap, + struct dentry *dentry, const char *xattr_name) +{ + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + return evm_protect_xattr(idmap, dentry, xattr_name, NULL, 0); +} + +#ifdef CONFIG_FS_POSIX_ACL +static int evm_inode_set_acl_change(struct mnt_idmap *idmap, + struct dentry *dentry, const char *name, + struct posix_acl *kacl) +{ + int rc; + + umode_t mode; + struct inode *inode = d_backing_inode(dentry); + + if (!kacl) + return 1; + + rc = posix_acl_update_mode(idmap, inode, &mode, &kacl); + if (rc || (inode->i_mode != mode)) + return 1; + + return 0; +} +#else +static inline int evm_inode_set_acl_change(struct mnt_idmap *idmap, + struct dentry *dentry, + const char *name, + struct posix_acl *kacl) +{ + return 0; +} +#endif + +/** + * evm_inode_set_acl - protect the EVM extended attribute from posix acls + * @idmap: idmap of the idmapped mount + * @dentry: pointer to the affected dentry + * @acl_name: name of the posix acl + * @kacl: pointer to the posix acls + * + * Prevent modifying posix acls causing the EVM HMAC to be re-calculated + * and 'security.evm' xattr updated, unless the existing 'security.evm' is + * valid. + */ +int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, + const char *acl_name, struct posix_acl *kacl) +{ + enum integrity_status evm_status; + + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + evm_status = evm_verify_current_integrity(dentry); + if ((evm_status == INTEGRITY_PASS) || + (evm_status == INTEGRITY_NOXATTRS)) + return 0; + + /* Exception if the HMAC is not going to be calculated. */ + if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL || + evm_status == INTEGRITY_UNKNOWN)) + return 0; + + /* + * Writing other xattrs is safe for portable signatures, as portable + * signatures are immutable and can never be updated. + */ + if (evm_status == INTEGRITY_FAIL_IMMUTABLE) + return 0; + + if (evm_status == INTEGRITY_PASS_IMMUTABLE && + !evm_inode_set_acl_change(idmap, dentry, acl_name, kacl)) + return 0; + + if (evm_status != INTEGRITY_PASS_IMMUTABLE) + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), + dentry->d_name.name, "appraise_metadata", + integrity_status_msg[evm_status], + -EPERM, 0); + return -EPERM; +} + +static void evm_reset_status(struct inode *inode) +{ + struct integrity_iint_cache *iint; + + iint = integrity_iint_find(inode); + if (iint) + iint->evm_status = INTEGRITY_UNKNOWN; +} + +/** + * evm_revalidate_status - report whether EVM status re-validation is necessary + * @xattr_name: pointer to the affected extended attribute name + * + * Report whether callers of evm_verifyxattr() should re-validate the + * EVM status. + * + * Return true if re-validation is necessary, false otherwise. + */ +bool evm_revalidate_status(const char *xattr_name) +{ + if (!evm_key_loaded()) + return false; + + /* evm_inode_post_setattr() passes NULL */ + if (!xattr_name) + return true; + + if (!evm_protected_xattr(xattr_name) && !posix_xattr_acl(xattr_name) && + strcmp(xattr_name, XATTR_NAME_EVM)) + return false; + + return true; +} + +/** + * 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_revalidate_status(xattr_name)) + return; + + evm_reset_status(dentry->d_inode); + + if (!strcmp(xattr_name, XATTR_NAME_EVM)) + return; + + if (!(evm_initialized & EVM_INIT_HMAC)) + return; + + evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len); +} + +/** + * 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. + * + * No need to take the i_mutex lock here, as this function is called from + * vfs_removexattr() which takes the i_mutex. + */ +void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) +{ + if (!evm_revalidate_status(xattr_name)) + return; + + evm_reset_status(dentry->d_inode); + + if (!strcmp(xattr_name, XATTR_NAME_EVM)) + return; + + if (!(evm_initialized & EVM_INIT_HMAC)) + return; + + evm_update_evmxattr(dentry, xattr_name, NULL, 0); +} + +static int evm_attr_change(struct mnt_idmap *idmap, + struct dentry *dentry, struct iattr *attr) +{ + struct inode *inode = d_backing_inode(dentry); + unsigned int ia_valid = attr->ia_valid; + + if (!i_uid_needs_update(idmap, attr, inode) && + !i_gid_needs_update(idmap, attr, inode) && + (!(ia_valid & ATTR_MODE) || attr->ia_mode == inode->i_mode)) + return 0; + + return 1; +} + +/** + * evm_inode_setattr - prevent updating an invalid EVM extended attribute + * @idmap: idmap of the mount + * @dentry: pointer to the affected dentry + * @attr: iattr structure containing the new file attributes + * + * Permit update of file attributes when files have a valid EVM signature, + * except in the case of them having an immutable portable signature. + */ +int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry, + struct iattr *attr) +{ + unsigned int ia_valid = attr->ia_valid; + enum integrity_status evm_status; + + /* Policy permits modification of the protected attrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))) + return 0; + evm_status = evm_verify_current_integrity(dentry); + /* + * Writing attrs is safe for portable signatures, as portable signatures + * are immutable and can never be updated. + */ + if ((evm_status == INTEGRITY_PASS) || + (evm_status == INTEGRITY_NOXATTRS) || + (evm_status == INTEGRITY_FAIL_IMMUTABLE) || + (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL || + evm_status == INTEGRITY_UNKNOWN))) + return 0; + + if (evm_status == INTEGRITY_PASS_IMMUTABLE && + !evm_attr_change(idmap, dentry, attr)) + return 0; + + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), + dentry->d_name.name, "appraise_metadata", + integrity_status_msg[evm_status], -EPERM, 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_revalidate_status(NULL)) + return; + + evm_reset_status(dentry->d_inode); + + if (!(evm_initialized & EVM_INIT_HMAC)) + return; + + if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) + evm_update_evmxattr(dentry, NULL, NULL, 0); +} + +/* + * evm_inode_init_security - initializes security.evm HMAC value + */ +int evm_inode_init_security(struct inode *inode, struct inode *dir, + const struct qstr *qstr, struct xattr *xattrs, + int *xattr_count) +{ + struct evm_xattr *xattr_data; + struct xattr *xattr, *evm_xattr; + bool evm_protected_xattrs = false; + int rc; + + if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs) + return 0; + + /* + * security_inode_init_security() makes sure that the xattrs array is + * contiguous, there is enough space for security.evm, and that there is + * a terminator at the end of the array. + */ + for (xattr = xattrs; xattr->name; xattr++) { + if (evm_protected_xattr(xattr->name)) + evm_protected_xattrs = true; + } + + /* EVM xattr not needed. */ + if (!evm_protected_xattrs) + return 0; + + evm_xattr = lsm_get_xattr_slot(xattrs, xattr_count); + /* + * Array terminator (xattr name = NULL) must be the first non-filled + * xattr slot. + */ + WARN_ONCE(evm_xattr != xattr, + "%s: xattrs terminator is not the first non-filled slot\n", + __func__); + + xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); + if (!xattr_data) + return -ENOMEM; + + xattr_data->data.type = EVM_XATTR_HMAC; + rc = evm_init_hmac(inode, xattrs, xattr_data->digest); + if (rc < 0) + goto out; + + evm_xattr->value = xattr_data; + evm_xattr->value_len = sizeof(*xattr_data); + evm_xattr->name = XATTR_EVM_SUFFIX; + return 0; +out: + kfree(xattr_data); + return rc; +} +EXPORT_SYMBOL_GPL(evm_inode_init_security); + +#ifdef CONFIG_EVM_LOAD_X509 +void __init evm_load_x509(void) +{ + int rc; + + rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH); + if (!rc) + evm_initialized |= EVM_INIT_X509; +} +#endif + +static int __init init_evm(void) +{ + int error; + struct list_head *pos, *q; + + evm_init_config(); + + error = integrity_init_keyring(INTEGRITY_KEYRING_EVM); + if (error) + goto error; + + error = evm_init_secfs(); + if (error < 0) { + pr_info("Error registering secfs\n"); + goto error; + } + +error: + if (error != 0) { + if (!list_empty(&evm_config_xattrnames)) { + list_for_each_safe(pos, q, &evm_config_xattrnames) + list_del(pos); + } + } + + return error; +} + +late_initcall(init_evm); |