/*
 * Copyright (C) 2008 IBM Corporation
 *
 * Author: Mimi Zohar <zohar@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: ima_api.c
 *      Implements must_appraise_or_measure, collect_measurement,
 *      appraise_measurement, store_measurement and store_template.
 */
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/evm.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);
}

/*
 * 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 *template_desc = ima_template_desc_current();
        int i, result = 0;

        *entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
                         sizeof(struct ima_field_data), GFP_NOFS);
        if (!*entry)
                return -ENOMEM;

        (*entry)->template_desc = template_desc;
        for (i = 0; i < template_desc->num_fields; i++) {
                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)
{
        static const char op[] = "add_template_measure";
        static const char audit_cause[] = "hashing_error";
        char *template_name = entry->template_desc->name;
        int result;
        struct {
                struct ima_digest_data hdr;
                char digest[TPM_DIGEST_SIZE];
        } hash;

        if (!violation) {
                int num_fields = entry->template_desc->num_fields;

                /* this function uses default algo */
                hash.hdr.algo = HASH_ALGO_SHA1;
                result = ima_calc_field_array_hash(&entry->template_data[0],
                                                   entry->template_desc,
                                                   num_fields, &hash.hdr);
                if (result < 0) {
                        integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
                                            template_name, op,
                                            audit_cause, result, 0);
                        return result;
                }
                memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
        }
        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, file, filename, NULL, 0,
                                            cause};
        int violation = 1;
        int result;

        /* can overflow, only indicator */
        atomic_long_inc(&ima_htable.violations);

        result = ima_alloc_init_template(&event_data, &entry);
        if (result < 0) {
                result = -ENOMEM;
                goto err_out;
        }
        result = ima_store_template(entry, violation, inode, filename);
        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.
 * @inode: pointer to inode to measure
 * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
 * @func: caller identifier
 *
 * 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 | MMAP_CHECK | MODULE_CHECK
 *      mask: contains the permission mask
 *      fsmagic: hex value
 *
 * Returns IMA_MEASURE, IMA_APPRAISE mask.
 *
 */
int ima_get_action(struct inode *inode, int mask, enum ima_hooks func)
{
        int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;

        flags &= ima_policy_flag;

        return ima_match_policy(inode, func, mask, flags);
}

/*
 * 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)
{
        const char *audit_cause = "failed";
        struct inode *inode = file_inode(file);
        const char *filename = file->f_path.dentry->d_name.name;
        int result = 0;
        struct {
                struct ima_digest_data hdr;
                char digest[IMA_MAX_DIGEST_SIZE];
        } hash;

        if (!(iint->flags & IMA_COLLECTED)) {
                u64 i_version = file_inode(file)->i_version;

                if (file->f_flags & O_DIRECT) {
                        audit_cause = "failed(directio)";
                        result = -EACCES;
                        goto out;
                }

                hash.hdr.algo = algo;

                result = (!buf) ?  ima_calc_file_hash(file, &hash.hdr) :
                        ima_calc_buffer_hash(buf, size, &hash.hdr);
                if (!result) {
                        int length = sizeof(hash.hdr) + hash.hdr.length;
                        void *tmpbuf = krealloc(iint->ima_hash, length,
                                                GFP_NOFS);
                        if (tmpbuf) {
                                iint->ima_hash = tmpbuf;
                                memcpy(iint->ima_hash, &hash, length);
                                iint->version = i_version;
                                iint->flags |= IMA_COLLECTED;
                        } else
                                result = -ENOMEM;
                }
        }
out:
        if (result)
                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)
{
        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, file, filename, xattr_value,
                                            xattr_len, NULL};
        int violation = 0;

        if (iint->flags & IMA_MEASURED)
                return;

        result = ima_alloc_init_template(&event_data, &entry);
        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);
        if (!result || result == -EEXIST)
                iint->flags |= IMA_MEASURED;
        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[(iint->ima_hash->length * 2) + 1];
        const char *algo_name = hash_algo_name[iint->ima_hash->algo];
        char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
        int i;

        if (iint->flags & IMA_AUDITED)
                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(current->audit_context, GFP_KERNEL,
                             AUDIT_INTEGRITY_RULE);
        if (!ab)
                return;

        audit_log_format(ab, "file=");
        audit_log_untrustedstring(ab, filename);
        audit_log_format(ab, " hash=");
        snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
        audit_log_untrustedstring(ab, algo_hash);

        audit_log_task_info(ab, current);
        audit_log_end(ab);

        iint->flags |= IMA_AUDITED;
}

const char *ima_d_path(struct path *path, char **pathbuf)
{
        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;
                }
        }
        return pathname ?: (const char *)path->dentry->d_name.name;
}