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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Copyright (C) 2005-2010 IBM Corporation
- *
- * Author:
- * Mimi Zohar <[email protected]>
- * Kylene Hall <[email protected]>
- *
- * File: evm_main.c
- * implements evm_inode_setxattr, evm_inode_post_setxattr,
- * evm_inode_removexattr, and evm_verifyxattr
- */
- #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 <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(&init_user_ns, 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;
- }
- static 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_acl_change - check if passed ACL changes the inode mode
- * @mnt_userns: user namespace of the idmapped 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 ACL changes the inode mode, which is protected by EVM.
- *
- * Returns 1 if passed ACL causes inode mode change, 0 otherwise.
- */
- static int evm_xattr_acl_change(struct user_namespace *mnt_userns,
- struct dentry *dentry, const char *xattr_name,
- const void *xattr_value, size_t xattr_value_len)
- {
- #ifdef CONFIG_FS_POSIX_ACL
- umode_t mode;
- struct posix_acl *acl = NULL, *acl_res;
- struct inode *inode = d_backing_inode(dentry);
- int rc;
- /*
- * An earlier comment here mentioned that the idmappings for
- * ACL_{GROUP,USER} don't matter since EVM is only interested in the
- * mode stored as part of POSIX ACLs. Nonetheless, if it must translate
- * from the uapi POSIX ACL representation to the VFS internal POSIX ACL
- * representation it should do so correctly. There's no guarantee that
- * we won't change POSIX ACLs in a way that ACL_{GROUP,USER} matters
- * for the mode at some point and it's difficult to keep track of all
- * the LSM and integrity modules and what they do to POSIX ACLs.
- *
- * Frankly, EVM shouldn't try to interpret the uapi struct for POSIX
- * ACLs it received. It requires knowledge that only the VFS is
- * guaranteed to have.
- */
- acl = vfs_set_acl_prepare(mnt_userns, i_user_ns(inode),
- xattr_value, xattr_value_len);
- if (IS_ERR_OR_NULL(acl))
- return 1;
- acl_res = acl;
- /*
- * Passing mnt_userns is necessary to correctly determine the GID in
- * an idmapped mount, as the GID is used to clear the setgid bit in
- * the inode mode.
- */
- rc = posix_acl_update_mode(mnt_userns, inode, &mode, &acl_res);
- posix_acl_release(acl);
- if (rc)
- return 1;
- if (inode->i_mode != mode)
- return 1;
- #endif
- return 0;
- }
- /*
- * evm_xattr_change - check if passed xattr value differs from current value
- * @mnt_userns: user namespace of the idmapped 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 user_namespace *mnt_userns,
- struct dentry *dentry, const char *xattr_name,
- const void *xattr_value, size_t xattr_value_len)
- {
- char *xattr_data = NULL;
- int rc = 0;
- if (posix_xattr_acl(xattr_name))
- return evm_xattr_acl_change(mnt_userns, dentry, xattr_name,
- xattr_value, xattr_value_len);
- rc = vfs_getxattr_alloc(&init_user_ns, dentry, xattr_name, &xattr_data,
- 0, GFP_NOFS);
- if (rc < 0)
- return 1;
- if (rc == xattr_value_len)
- rc = !!memcmp(xattr_value, xattr_data, rc);
- else
- rc = 1;
- 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 user_namespace *mnt_userns,
- 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(mnt_userns, 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
- * @mnt_userns: user namespace of the idmapped 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 user_namespace *mnt_userns, 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(mnt_userns, dentry, xattr_name, xattr_value,
- xattr_value_len);
- }
- /**
- * evm_inode_removexattr - protect the EVM extended attribute
- * @mnt_userns: user namespace of the idmapped 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 user_namespace *mnt_userns,
- 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(mnt_userns, dentry, xattr_name, NULL, 0);
- }
- 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 user_namespace *mnt_userns,
- 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(mnt_userns, attr, inode) &&
- !i_gid_needs_update(mnt_userns, 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 user_namespace *mnt_userns, 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(mnt_userns, 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,
- const struct xattr *lsm_xattr,
- struct xattr *evm_xattr)
- {
- struct evm_xattr *xattr_data;
- int rc;
- if (!(evm_initialized & EVM_INIT_HMAC) ||
- !evm_protected_xattr(lsm_xattr->name))
- return 0;
- 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, 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 = 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);
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