Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 604 insertions, 0 deletions

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
new file mode 100644
index 000000000..6d1efe135
--- /dev/null
+++ b/security/integrity/evm/evm_main.c
@@ -0,0 +1,604 @@
+/*
+ * 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
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.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 <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", "no_label", "no_xattrs", "unknown"
+};
+int evm_hmac_attrs;
+
+static struct xattr_list evm_config_default_xattrnames[] = {
+#ifdef CONFIG_SECURITY_SELINUX
+	{.name = XATTR_NAME_SELINUX},
+#endif
+#ifdef CONFIG_SECURITY_SMACK
+	{.name = XATTR_NAME_SMACK},
+#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
+	{.name = XATTR_NAME_SMACKEXEC},
+	{.name = XATTR_NAME_SMACKTRANSMUTE},
+	{.name = XATTR_NAME_SMACKMMAP},
+#endif
+#endif
+#ifdef CONFIG_SECURITY_APPARMOR
+	{.name = XATTR_NAME_APPARMOR},
+#endif
+#ifdef CONFIG_IMA_APPRAISE
+	{.name = XATTR_NAME_IMA},
+#endif
+	{.name = XATTR_NAME_CAPS},
+};
+
+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;
+	return 0;
+}
+__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\n", evm_config_default_xattrnames[i].name);
+		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);
+}
+
+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;
+
+	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(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_ima_xattr_data)) {
+			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->digest, digest.digest,
+				   SHA1_DIGEST_SIZE);
+		if (rc)
+			rc = -EINVAL;
+		break;
+	case EVM_IMA_XATTR_DIGSIG:
+	case EVM_XATTR_PORTABLE_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)
+		evm_status = (rc == -ENODATA) ?
+				INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
+out:
+	if (iint)
+		iint->evm_status = evm_status;
+	kfree(xattr_data);
+	return evm_status;
+}
+
+static int evm_protected_xattr(const char *req_xattr_name)
+{
+	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 ((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;
+}
+
+/**
+ * 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_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 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 unless the EVM signature is immutable.
+ */
+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;
+		goto out;
+	}
+
+	evm_status = evm_verify_current_integrity(dentry);
+	if (evm_status == INTEGRITY_NOXATTRS) {
+		struct integrity_iint_cache *iint;
+
+		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:
+	if (evm_status != INTEGRITY_PASS)
+		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
+ * @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 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(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)
+{
+	/* 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(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_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_key_loaded() || (!evm_protected_xattr(xattr_name)
+				  && !posix_xattr_acl(xattr_name)))
+		return;
+
+	evm_reset_status(dentry->d_inode);
+
+	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_key_loaded() || !evm_protected_xattr(xattr_name))
+		return;
+
+	evm_reset_status(dentry->d_inode);
+
+	evm_update_evmxattr(dentry, xattr_name, NULL, 0);
+}
+
+/**
+ * evm_inode_setattr - prevent updating an invalid EVM extended attribute
+ * @dentry: pointer to the affected dentry
+ *
+ * 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 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);
+	if ((evm_status == INTEGRITY_PASS) ||
+	    (evm_status == INTEGRITY_NOXATTRS))
+		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_key_loaded())
+		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_ima_xattr_data *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->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;
+	struct xattr_list *xattr;
+
+	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) {
+				xattr = list_entry(pos, struct xattr_list,
+						   list);
+				list_del(pos);
+			}
+		}
+	}
+
+	return error;
+}
+
+late_initcall(init_evm);
+
+MODULE_DESCRIPTION("Extended Verification Module");
+MODULE_LICENSE("GPL");