1 files changed, 455 insertions, 0 deletions

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
new file mode 100644
index 000000000..026c8c9db
--- /dev/null
+++ b/security/integrity/ima/ima_api.c
@@ -0,0 +1,455 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2008 IBM Corporation
+ *
+ * Author: Mimi Zohar <zohar@us.ibm.com>
+ *
+ * File: ima_api.c
+ *	Implements must_appraise_or_measure, collect_measurement,
+ *	appraise_measurement, store_measurement and store_template.
+ */
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/xattr.h>
+#include <linux/evm.h>
+#include <linux/iversion.h>
+#include <linux/fsverity.h>
+
+#include "ima.h"
+
+/*
+ * ima_free_template_entry - free an existing template entry
+ */
+void ima_free_template_entry(struct ima_template_entry *entry)
+{
+	int i;
+
+	for (i = 0; i < entry->template_desc->num_fields; i++)
+		kfree(entry->template_data[i].data);
+
+	kfree(entry->digests);
+	kfree(entry);
+}
+
+/*
+ * ima_alloc_init_template - create and initialize a new template entry
+ */
+int ima_alloc_init_template(struct ima_event_data *event_data,
+			    struct ima_template_entry **entry,
+			    struct ima_template_desc *desc)
+{
+	struct ima_template_desc *template_desc;
+	struct tpm_digest *digests;
+	int i, result = 0;
+
+	if (desc)
+		template_desc = desc;
+	else
+		template_desc = ima_template_desc_current();
+
+	*entry = kzalloc(struct_size(*entry, template_data,
+				     template_desc->num_fields), GFP_NOFS);
+	if (!*entry)
+		return -ENOMEM;
+
+	digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
+			  sizeof(*digests), GFP_NOFS);
+	if (!digests) {
+		kfree(*entry);
+		*entry = NULL;
+		return -ENOMEM;
+	}
+
+	(*entry)->digests = digests;
+	(*entry)->template_desc = template_desc;
+	for (i = 0; i < template_desc->num_fields; i++) {
+		const struct ima_template_field *field =
+			template_desc->fields[i];
+		u32 len;
+
+		result = field->field_init(event_data,
+					   &((*entry)->template_data[i]));
+		if (result != 0)
+			goto out;
+
+		len = (*entry)->template_data[i].len;
+		(*entry)->template_data_len += sizeof(len);
+		(*entry)->template_data_len += len;
+	}
+	return 0;
+out:
+	ima_free_template_entry(*entry);
+	*entry = NULL;
+	return result;
+}
+
+/*
+ * ima_store_template - store ima template measurements
+ *
+ * Calculate the hash of a template entry, add the template entry
+ * to an ordered list of measurement entries maintained inside the kernel,
+ * and also update the aggregate integrity value (maintained inside the
+ * configured TPM PCR) over the hashes of the current list of measurement
+ * entries.
+ *
+ * Applications retrieve the current kernel-held measurement list through
+ * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
+ * TPM PCR (called quote) can be retrieved using a TPM user space library
+ * and is used to validate the measurement list.
+ *
+ * Returns 0 on success, error code otherwise
+ */
+int ima_store_template(struct ima_template_entry *entry,
+		       int violation, struct inode *inode,
+		       const unsigned char *filename, int pcr)
+{
+	static const char op[] = "add_template_measure";
+	static const char audit_cause[] = "hashing_error";
+	char *template_name = entry->template_desc->name;
+	int result;
+
+	if (!violation) {
+		result = ima_calc_field_array_hash(&entry->template_data[0],
+						   entry);
+		if (result < 0) {
+			integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
+					    template_name, op,
+					    audit_cause, result, 0);
+			return result;
+		}
+	}
+	entry->pcr = pcr;
+	result = ima_add_template_entry(entry, violation, op, inode, filename);
+	return result;
+}
+
+/*
+ * ima_add_violation - add violation to measurement list.
+ *
+ * Violations are flagged in the measurement list with zero hash values.
+ * By extending the PCR with 0xFF's instead of with zeroes, the PCR
+ * value is invalidated.
+ */
+void ima_add_violation(struct file *file, const unsigned char *filename,
+		       struct integrity_iint_cache *iint,
+		       const char *op, const char *cause)
+{
+	struct ima_template_entry *entry;
+	struct inode *inode = file_inode(file);
+	struct ima_event_data event_data = { .iint = iint,
+					     .file = file,
+					     .filename = filename,
+					     .violation = cause };
+	int violation = 1;
+	int result;
+
+	/* can overflow, only indicator */
+	atomic_long_inc(&ima_htable.violations);
+
+	result = ima_alloc_init_template(&event_data, &entry, NULL);
+	if (result < 0) {
+		result = -ENOMEM;
+		goto err_out;
+	}
+	result = ima_store_template(entry, violation, inode,
+				    filename, CONFIG_IMA_MEASURE_PCR_IDX);
+	if (result < 0)
+		ima_free_template_entry(entry);
+err_out:
+	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
+			    op, cause, result, 0);
+}
+
+/**
+ * ima_get_action - appraise & measure decision based on policy.
+ * @mnt_userns:	user namespace of the mount the inode was found from
+ * @inode: pointer to the inode associated with the object being validated
+ * @cred: pointer to credentials structure to validate
+ * @secid: secid of the task being validated
+ * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
+ *        MAY_APPEND)
+ * @func: caller identifier
+ * @pcr: pointer filled in if matched measure policy sets pcr=
+ * @template_desc: pointer filled in if matched measure policy sets template=
+ * @func_data: func specific data, may be NULL
+ * @allowed_algos: allowlist of hash algorithms for the IMA xattr
+ *
+ * The policy is defined in terms of keypairs:
+ *		subj=, obj=, type=, func=, mask=, fsmagic=
+ *	subj,obj, and type: are LSM specific.
+ *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
+ *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA
+ *	mask: contains the permission mask
+ *	fsmagic: hex value
+ *
+ * Returns IMA_MEASURE, IMA_APPRAISE mask.
+ *
+ */
+int ima_get_action(struct user_namespace *mnt_userns, struct inode *inode,
+		   const struct cred *cred, u32 secid, int mask,
+		   enum ima_hooks func, int *pcr,
+		   struct ima_template_desc **template_desc,
+		   const char *func_data, unsigned int *allowed_algos)
+{
+	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
+
+	flags &= ima_policy_flag;
+
+	return ima_match_policy(mnt_userns, inode, cred, secid, func, mask,
+				flags, pcr, template_desc, func_data,
+				allowed_algos);
+}
+
+static int ima_get_verity_digest(struct integrity_iint_cache *iint,
+				 struct ima_max_digest_data *hash)
+{
+	enum hash_algo verity_alg;
+	int ret;
+
+	/*
+	 * On failure, 'measure' policy rules will result in a file data
+	 * hash containing 0's.
+	 */
+	ret = fsverity_get_digest(iint->inode, hash->digest, &verity_alg);
+	if (ret)
+		return ret;
+
+	/*
+	 * Unlike in the case of actually calculating the file hash, in
+	 * the fsverity case regardless of the hash algorithm, return
+	 * the verity digest to be included in the measurement list. A
+	 * mismatch between the verity algorithm and the xattr signature
+	 * algorithm, if one exists, will be detected later.
+	 */
+	hash->hdr.algo = verity_alg;
+	hash->hdr.length = hash_digest_size[verity_alg];
+	return 0;
+}
+
+/*
+ * ima_collect_measurement - collect file measurement
+ *
+ * Calculate the file hash, if it doesn't already exist,
+ * storing the measurement and i_version in the iint.
+ *
+ * Must be called with iint->mutex held.
+ *
+ * Return 0 on success, error code otherwise
+ */
+int ima_collect_measurement(struct integrity_iint_cache *iint,
+			    struct file *file, void *buf, loff_t size,
+			    enum hash_algo algo, struct modsig *modsig)
+{
+	const char *audit_cause = "failed";
+	struct inode *inode = file_inode(file);
+	struct inode *real_inode = d_real_inode(file_dentry(file));
+	const char *filename = file->f_path.dentry->d_name.name;
+	struct ima_max_digest_data hash;
+	int result = 0;
+	int length;
+	void *tmpbuf;
+	u64 i_version;
+
+	/*
+	 * Always collect the modsig, because IMA might have already collected
+	 * the file digest without collecting the modsig in a previous
+	 * measurement rule.
+	 */
+	if (modsig)
+		ima_collect_modsig(modsig, buf, size);
+
+	if (iint->flags & IMA_COLLECTED)
+		goto out;
+
+	/*
+	 * Detecting file change is based on i_version. On filesystems
+	 * which do not support i_version, support was originally limited
+	 * to an initial measurement/appraisal/audit, but was modified to
+	 * assume the file changed.
+	 */
+	i_version = inode_query_iversion(inode);
+	hash.hdr.algo = algo;
+	hash.hdr.length = hash_digest_size[algo];
+
+	/* Initialize hash digest to 0's in case of failure */
+	memset(&hash.digest, 0, sizeof(hash.digest));
+
+	if (iint->flags & IMA_VERITY_REQUIRED) {
+		result = ima_get_verity_digest(iint, &hash);
+		switch (result) {
+		case 0:
+			break;
+		case -ENODATA:
+			audit_cause = "no-verity-digest";
+			break;
+		default:
+			audit_cause = "invalid-verity-digest";
+			break;
+		}
+	} else if (buf) {
+		result = ima_calc_buffer_hash(buf, size, &hash.hdr);
+	} else {
+		result = ima_calc_file_hash(file, &hash.hdr);
+	}
+
+	if (result && result != -EBADF && result != -EINVAL)
+		goto out;
+
+	length = sizeof(hash.hdr) + hash.hdr.length;
+	tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
+	if (!tmpbuf) {
+		result = -ENOMEM;
+		goto out;
+	}
+
+	iint->ima_hash = tmpbuf;
+	memcpy(iint->ima_hash, &hash, length);
+	iint->version = i_version;
+	if (real_inode != inode) {
+		iint->real_ino = real_inode->i_ino;
+		iint->real_dev = real_inode->i_sb->s_dev;
+	}
+
+	/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
+	if (!result)
+		iint->flags |= IMA_COLLECTED;
+out:
+	if (result) {
+		if (file->f_flags & O_DIRECT)
+			audit_cause = "failed(directio)";
+
+		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
+				    filename, "collect_data", audit_cause,
+				    result, 0);
+	}
+	return result;
+}
+
+/*
+ * ima_store_measurement - store file measurement
+ *
+ * Create an "ima" template and then store the template by calling
+ * ima_store_template.
+ *
+ * We only get here if the inode has not already been measured,
+ * but the measurement could already exist:
+ *	- multiple copies of the same file on either the same or
+ *	  different filesystems.
+ *	- the inode was previously flushed as well as the iint info,
+ *	  containing the hashing info.
+ *
+ * Must be called with iint->mutex held.
+ */
+void ima_store_measurement(struct integrity_iint_cache *iint,
+			   struct file *file, const unsigned char *filename,
+			   struct evm_ima_xattr_data *xattr_value,
+			   int xattr_len, const struct modsig *modsig, int pcr,
+			   struct ima_template_desc *template_desc)
+{
+	static const char op[] = "add_template_measure";
+	static const char audit_cause[] = "ENOMEM";
+	int result = -ENOMEM;
+	struct inode *inode = file_inode(file);
+	struct ima_template_entry *entry;
+	struct ima_event_data event_data = { .iint = iint,
+					     .file = file,
+					     .filename = filename,
+					     .xattr_value = xattr_value,
+					     .xattr_len = xattr_len,
+					     .modsig = modsig };
+	int violation = 0;
+
+	/*
+	 * We still need to store the measurement in the case of MODSIG because
+	 * we only have its contents to put in the list at the time of
+	 * appraisal, but a file measurement from earlier might already exist in
+	 * the measurement list.
+	 */
+	if (iint->measured_pcrs & (0x1 << pcr) && !modsig)
+		return;
+
+	result = ima_alloc_init_template(&event_data, &entry, template_desc);
+	if (result < 0) {
+		integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
+				    op, audit_cause, result, 0);
+		return;
+	}
+
+	result = ima_store_template(entry, violation, inode, filename, pcr);
+	if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
+		iint->flags |= IMA_MEASURED;
+		iint->measured_pcrs |= (0x1 << pcr);
+	}
+	if (result < 0)
+		ima_free_template_entry(entry);
+}
+
+void ima_audit_measurement(struct integrity_iint_cache *iint,
+			   const unsigned char *filename)
+{
+	struct audit_buffer *ab;
+	char *hash;
+	const char *algo_name = hash_algo_name[iint->ima_hash->algo];
+	int i;
+
+	if (iint->flags & IMA_AUDITED)
+		return;
+
+	hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
+	if (!hash)
+		return;
+
+	for (i = 0; i < iint->ima_hash->length; i++)
+		hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
+	hash[i * 2] = '\0';
+
+	ab = audit_log_start(audit_context(), GFP_KERNEL,
+			     AUDIT_INTEGRITY_RULE);
+	if (!ab)
+		goto out;
+
+	audit_log_format(ab, "file=");
+	audit_log_untrustedstring(ab, filename);
+	audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
+
+	audit_log_task_info(ab);
+	audit_log_end(ab);
+
+	iint->flags |= IMA_AUDITED;
+out:
+	kfree(hash);
+	return;
+}
+
+/*
+ * ima_d_path - return a pointer to the full pathname
+ *
+ * Attempt to return a pointer to the full pathname for use in the
+ * IMA measurement list, IMA audit records, and auditing logs.
+ *
+ * On failure, return a pointer to a copy of the filename, not dname.
+ * Returning a pointer to dname, could result in using the pointer
+ * after the memory has been freed.
+ */
+const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
+{
+	char *pathname = NULL;
+
+	*pathbuf = __getname();
+	if (*pathbuf) {
+		pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
+		if (IS_ERR(pathname)) {
+			__putname(*pathbuf);
+			*pathbuf = NULL;
+			pathname = NULL;
+		}
+	}
+
+	if (!pathname) {
+		strscpy(namebuf, path->dentry->d_name.name, NAME_MAX);
+		pathname = namebuf;
+	}
+
+	return pathname;
+}