// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Kylene Hall <kjhall@us.ibm.com>
 * Reiner Sailer <sailer@us.ibm.com>
 * Mimi Zohar <zohar@us.ibm.com>
 *
 * File: ima_fs.c
 *      implemenents security file system for reporting
 *      current measurement list and IMA statistics
 */

#include <linux/fcntl.h>
#include <linux/kernel_read_file.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/parser.h>
#include <linux/vmalloc.h>

#include "ima.h"

/*
 * Requests:
 * 'A\n': stage the entire measurements list
 * 'D\n': delete all staged measurements
 * '[1, ULONG_MAX]\n' delete N measurements records
 */
#define STAGED_REQ_LENGTH 21

static DEFINE_MUTEX(ima_write_mutex);
static DEFINE_MUTEX(ima_measure_mutex);
static long ima_measure_users;
static struct task_struct *measure_writer;
static long measure_writer_extra_writes;

bool ima_canonical_fmt;
static int __init default_canonical_fmt_setup(char *str)
{
#ifdef __BIG_ENDIAN
        ima_canonical_fmt = true;
#endif
        return 1;
}
__setup("ima_canonical_fmt", default_canonical_fmt_setup);

static int valid_policy = 1;

static ssize_t ima_show_counter(char __user *buf, size_t count, loff_t *ppos,
                                atomic_long_t *val)
{
        char tmpbuf[32];        /* greater than largest 'long' string value */
        ssize_t len;

        len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
        return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
}

static ssize_t ima_show_num_violations(struct file *filp, char __user *buf,
                                       size_t count, loff_t *ppos)
{
        return ima_show_counter(buf, count, ppos, &ima_num_violations);
}

static const struct file_operations ima_num_violations_ops = {
        .read = ima_show_num_violations,
        .llseek = generic_file_llseek,
};

static ssize_t ima_show_measurements_count(struct file *filp,
                                           char __user *buf,
                                           size_t count, loff_t *ppos)
{
        return ima_show_counter(buf, count, ppos, &ima_num_records[BINARY]);
}

static const struct file_operations ima_measurements_count_ops = {
        .read = ima_show_measurements_count,
        .llseek = generic_file_llseek,
};

/* returns pointer to hlist_node */
static void *_ima_measurements_start(struct seq_file *m, loff_t *pos,
                                     struct list_head *head)
{
        loff_t l = *pos;
        struct ima_queue_entry *qe;

        /* we need a lock since pos could point beyond last element */
        rcu_read_lock();
        list_for_each_entry_rcu(qe, head, later) {
                if (!l--) {
                        rcu_read_unlock();
                        return qe;
                }
        }
        rcu_read_unlock();
        return NULL;
}

static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
{
        return _ima_measurements_start(m, pos, &ima_measurements);
}

static void *ima_measurements_staged_start(struct seq_file *m, loff_t *pos)
{
        return _ima_measurements_start(m, pos, &ima_measurements_staged);
}

static void *_ima_measurements_next(struct seq_file *m, void *v, loff_t *pos,
                                    struct list_head *head)
{
        struct ima_queue_entry *qe = v;

        /* lock protects when reading beyond last element
         * against concurrent list-extension
         */
        rcu_read_lock();
        qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
        rcu_read_unlock();
        (*pos)++;

        return (&qe->later == head) ? NULL : qe;
}

static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
{
        return _ima_measurements_next(m, v, pos, &ima_measurements);
}

static void *ima_measurements_staged_next(struct seq_file *m, void *v,
                                          loff_t *pos)
{
        return _ima_measurements_next(m, v, pos, &ima_measurements_staged);
}

static void ima_measurements_stop(struct seq_file *m, void *v)
{
}

void ima_putc(struct seq_file *m, void *data, int datalen)
{
        while (datalen--)
                seq_putc(m, *(char *)data++);
}

/* print format:
 *       32bit-le=pcr#
 *       char[n]=template digest
 *       32bit-le=template name size
 *       char[n]=template name
 *       [eventdata length]
 *       eventdata[n]=template specific data
 */
int ima_measurements_show(struct seq_file *m, void *v)
{
        /* the list never shrinks, so we don't need a lock here */
        struct ima_queue_entry *qe = v;
        struct ima_template_entry *e;
        char *template_name;
        u32 pcr, namelen, template_data_len; /* temporary fields */
        bool is_ima_template = false;
        int i, algo_idx;

        algo_idx = ima_sha1_idx;

        if (m->file != NULL)
                algo_idx = (unsigned long)file_inode(m->file)->i_private;

        /* get entry */
        e = qe->entry;
        if (e == NULL)
                return -1;

        template_name = (e->template_desc->name[0] != '\0') ?
            e->template_desc->name : e->template_desc->fmt;

        /*
         * 1st: PCRIndex
         * PCR used defaults to the same (config option) in
         * little-endian format, unless set in policy
         */
        pcr = !ima_canonical_fmt ? e->pcr : (__force u32)cpu_to_le32(e->pcr);
        ima_putc(m, &pcr, sizeof(e->pcr));

        /* 2nd: template digest */
        ima_putc(m, e->digests[algo_idx].digest,
                 ima_algo_array[algo_idx].digest_size);

        /* 3rd: template name size */
        namelen = !ima_canonical_fmt ? strlen(template_name) :
                (__force u32)cpu_to_le32(strlen(template_name));
        ima_putc(m, &namelen, sizeof(namelen));

        /* 4th:  template name */
        ima_putc(m, template_name, strlen(template_name));

        /* 5th:  template length (except for 'ima' template) */
        if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
                is_ima_template = true;

        if (!is_ima_template) {
                template_data_len = !ima_canonical_fmt ? e->template_data_len :
                        (__force u32)cpu_to_le32(e->template_data_len);
                ima_putc(m, &template_data_len, sizeof(e->template_data_len));
        }

        /* 6th:  template specific data */
        for (i = 0; i < e->template_desc->num_fields; i++) {
                enum ima_show_type show = IMA_SHOW_BINARY;
                const struct ima_template_field *field =
                        e->template_desc->fields[i];

                if (is_ima_template && strcmp(field->field_id, "d") == 0)
                        show = IMA_SHOW_BINARY_NO_FIELD_LEN;
                if (is_ima_template && strcmp(field->field_id, "n") == 0)
                        show = IMA_SHOW_BINARY_OLD_STRING_FMT;
                field->field_show(m, show, &e->template_data[i]);
        }
        return 0;
}

static const struct seq_operations ima_measurments_seqops = {
        .start = ima_measurements_start,
        .next = ima_measurements_next,
        .stop = ima_measurements_stop,
        .show = ima_measurements_show
};

static const struct seq_operations ima_measurments_staged_seqops = {
        .start = ima_measurements_staged_start,
        .next = ima_measurements_staged_next,
        .stop = ima_measurements_stop,
        .show = ima_measurements_show
};

static int ima_measure_lock(bool write)
{
        mutex_lock(&ima_measure_mutex);
        /* Overflow check. */
        if (!write && ima_measure_users == LONG_MAX) {
                mutex_unlock(&ima_measure_mutex);
                return -ENFILE;
        }

        /* Same writer can do additional writes or read/writes. */
        if (write && current == measure_writer) {
                measure_writer_extra_writes++;
                mutex_unlock(&ima_measure_mutex);
                return 0;
        }

        /*
         * ima_measure_users: > 0 open readers
         * ima_measure_users: == -1 open writer
         */
        if ((write && ima_measure_users != 0) ||
            (!write && ima_measure_users < 0)) {
                mutex_unlock(&ima_measure_mutex);
                return -EBUSY;
        }

        if (write) {
                ima_measure_users--;
                /* Pointer valid, no reuse while the file descriptor is open. */
                measure_writer = current;
        } else {
                ima_measure_users++;
        }
        mutex_unlock(&ima_measure_mutex);
        return 0;
}

static void ima_measure_unlock(bool write)
{
        mutex_lock(&ima_measure_mutex);
        /* Decrement additional writes or read/writes. */
        if (write && current == measure_writer &&
            measure_writer_extra_writes != 0) {
                measure_writer_extra_writes--;
                mutex_unlock(&ima_measure_mutex);
                return;
        }
        if (write) {
                ima_measure_users++;
                measure_writer = NULL;
        } else {
                ima_measure_users--;
        }
        mutex_unlock(&ima_measure_mutex);
}

static int _ima_measurements_open(struct inode *inode, struct file *file,
                                  const struct seq_operations *seq_ops)
{
        bool write = (file->f_mode & FMODE_WRITE);
        int ret;

        if (write && !capable(CAP_SYS_ADMIN))
                return -EPERM;

        ret = ima_measure_lock(write);
        if (ret < 0)
                return ret;

        ret = seq_open(file, seq_ops);
        if (ret < 0)
                ima_measure_unlock(write);

        return ret;
}

static int ima_measurements_open(struct inode *inode, struct file *file)
{
        return _ima_measurements_open(inode, file, &ima_measurments_seqops);
}

static int ima_measurements_release(struct inode *inode, struct file *file)
{
        bool write = (file->f_mode & FMODE_WRITE);
        int ret;

        /* seq_release() always returns zero. */
        ret = seq_release(inode, file);

        ima_measure_unlock(write);

        return ret;
}

static int ima_measurements_staged_open(struct inode *inode, struct file *file)
{
        return _ima_measurements_open(inode, file,
                                      &ima_measurments_staged_seqops);
}

static ssize_t _ima_measurements_write(struct file *file,
                                       const char __user *buf, size_t datalen,
                                       loff_t *ppos, bool staged_interface)
{
        char req[STAGED_REQ_LENGTH];
        unsigned long req_value;
        int ret;

        if (datalen < 2 || datalen > STAGED_REQ_LENGTH)
                return -EINVAL;

        if (copy_from_user(req, buf, datalen) != 0)
                return -EFAULT;

        if (req[datalen - 1] != '\n')
                return -EINVAL;

        req[datalen - 1] = '\0';

        switch (req[0]) {
        case 'A':
                if (datalen != 2 || !staged_interface)
                        return -EINVAL;

                ret = ima_queue_stage();
                break;
        case 'D':
                if (datalen != 2 || !staged_interface)
                        return -EINVAL;

                ret = ima_queue_staged_delete_all();
                break;
        default:
                if (staged_interface)
                        return -EINVAL;

                if (ima_flush_htable) {
                        pr_debug("Deleting staged N measurements not supported when flushing the hash table is requested\n");
                        return -EINVAL;
                }

                ret = kstrtoul(req, 10, &req_value);
                if (ret < 0)
                        return ret;

                if (req_value == 0) {
                        pr_debug("Must delete at least one entry\n");
                        return -EINVAL;
                }

                ret = ima_queue_delete_partial(req_value);
        }

        if (ret < 0)
                return ret;

        return datalen;
}

static ssize_t ima_measurements_write(struct file *file, const char __user *buf,
                                      size_t datalen, loff_t *ppos)
{
        return _ima_measurements_write(file, buf, datalen, ppos, false);
}

static ssize_t ima_measurements_staged_write(struct file *file,
                                             const char __user *buf,
                                             size_t datalen, loff_t *ppos)
{
        return _ima_measurements_write(file, buf, datalen, ppos, true);
}

static const struct file_operations ima_measurements_ops = {
        .open = ima_measurements_open,
        .read = seq_read,
        .write = ima_measurements_write,
        .llseek = seq_lseek,
        .release = ima_measurements_release,
};

static const struct file_operations ima_measurements_staged_ops = {
        .open = ima_measurements_staged_open,
        .read = seq_read,
        .write = ima_measurements_staged_write,
        .llseek = seq_lseek,
        .release = ima_measurements_release,
};

void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
{
        u32 i;

        for (i = 0; i < size; i++)
                seq_printf(m, "%02x", *(digest + i));
}

/* print in ascii */
static int ima_ascii_measurements_show(struct seq_file *m, void *v)
{
        /* the list never shrinks, so we don't need a lock here */
        struct ima_queue_entry *qe = v;
        struct ima_template_entry *e;
        char *template_name;
        int i, algo_idx;

        algo_idx = ima_sha1_idx;

        if (m->file != NULL)
                algo_idx = (unsigned long)file_inode(m->file)->i_private;

        /* get entry */
        e = qe->entry;
        if (e == NULL)
                return -1;

        template_name = (e->template_desc->name[0] != '\0') ?
            e->template_desc->name : e->template_desc->fmt;

        /* 1st: PCR used (config option) */
        seq_printf(m, "%2d ", e->pcr);

        /* 2nd: template hash */
        ima_print_digest(m, e->digests[algo_idx].digest,
                         ima_algo_array[algo_idx].digest_size);

        /* 3th:  template name */
        seq_printf(m, " %s", template_name);

        /* 4th:  template specific data */
        for (i = 0; i < e->template_desc->num_fields; i++) {
                seq_puts(m, " ");
                if (e->template_data[i].len == 0)
                        continue;

                e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
                                                        &e->template_data[i]);
        }
        seq_puts(m, "\n");
        return 0;
}

static const struct seq_operations ima_ascii_measurements_seqops = {
        .start = ima_measurements_start,
        .next = ima_measurements_next,
        .stop = ima_measurements_stop,
        .show = ima_ascii_measurements_show
};

static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
{
        return _ima_measurements_open(inode, file,
                                      &ima_ascii_measurements_seqops);
}

static const struct file_operations ima_ascii_measurements_ops = {
        .open = ima_ascii_measurements_open,
        .read = seq_read,
        .write = ima_measurements_write,
        .llseek = seq_lseek,
        .release = ima_measurements_release,
};

static const struct seq_operations ima_ascii_measurements_staged_seqops = {
        .start = ima_measurements_staged_start,
        .next = ima_measurements_staged_next,
        .stop = ima_measurements_stop,
        .show = ima_ascii_measurements_show
};

static int ima_ascii_measurements_staged_open(struct inode *inode,
                                              struct file *file)
{
        return _ima_measurements_open(inode, file,
                                      &ima_ascii_measurements_staged_seqops);
}

static const struct file_operations ima_ascii_measurements_staged_ops = {
        .open = ima_ascii_measurements_staged_open,
        .read = seq_read,
        .write = ima_measurements_staged_write,
        .llseek = seq_lseek,
        .release = ima_measurements_release,
};

static ssize_t ima_read_policy(char *path)
{
        void *data = NULL;
        char *datap;
        size_t size;
        int rc, pathlen = strlen(path);

        char *p;

        /* remove \n */
        datap = path;
        strsep(&datap, "\n");

        rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
                                        READING_POLICY);
        if (rc < 0) {
                pr_err("Unable to open file: %s (%d)", path, rc);
                return rc;
        }
        size = rc;
        rc = 0;

        datap = data;
        while (size > 0 && (p = strsep(&datap, "\n"))) {
                pr_debug("rule: %s\n", p);
                rc = ima_parse_add_rule(p);
                if (rc < 0)
                        break;
                size -= rc;
        }

        vfree(data);
        if (rc < 0)
                return rc;
        else if (size)
                return -EINVAL;
        else
                return pathlen;
}

static ssize_t ima_write_policy(struct file *file, const char __user *buf,
                                size_t datalen, loff_t *ppos)
{
        char *data;
        ssize_t result;

        if (datalen >= PAGE_SIZE)
                datalen = PAGE_SIZE - 1;

        /* No partial writes. */
        result = -EINVAL;
        if (*ppos != 0)
                goto out;

        data = memdup_user_nul(buf, datalen);
        if (IS_ERR(data)) {
                result = PTR_ERR(data);
                goto out;
        }

        result = mutex_lock_interruptible(&ima_write_mutex);
        if (result < 0)
                goto out_free;

        if (data[0] == '/') {
                result = ima_read_policy(data);
        } else if (ima_appraise & IMA_APPRAISE_POLICY) {
                pr_err("signed policy file (specified as an absolute pathname) required\n");
                integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
                                    "policy_update", "signed policy required",
                                    1, 0);
                result = -EACCES;
        } else {
                result = ima_parse_add_rule(data);
        }
        mutex_unlock(&ima_write_mutex);
out_free:
        kfree(data);
out:
        if (result < 0)
                valid_policy = 0;

        return result;
}

static struct dentry *ima_dir;
static struct dentry *ima_symlink;

enum ima_fs_flags {
        IMA_FS_BUSY,
};

static unsigned long ima_fs_flags;

#ifdef  CONFIG_IMA_READ_POLICY
static const struct seq_operations ima_policy_seqops = {
                .start = ima_policy_start,
                .next = ima_policy_next,
                .stop = ima_policy_stop,
                .show = ima_policy_show,
};
#endif

static int __init create_securityfs_measurement_lists(bool staging)
{
        const struct file_operations *ascii_ops = &ima_ascii_measurements_ops;
        const struct file_operations *binary_ops = &ima_measurements_ops;
        umode_t permissions = (S_IRUSR | S_IRGRP | S_IWUSR | S_IWGRP);
        const char *file_suffix = "";
        int count = NR_BANKS(ima_tpm_chip);

        if (staging) {
                ascii_ops = &ima_ascii_measurements_staged_ops;
                binary_ops = &ima_measurements_staged_ops;
                file_suffix = "_staged";
        }

        if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip))
                count++;

        for (int i = 0; i < count; i++) {
                u16 algo = ima_algo_array[i].algo;
                char file_name[NAME_MAX + 1];
                struct dentry *dentry;

                if (algo == HASH_ALGO__LAST)
                        snprintf(file_name, sizeof(file_name),
                                 "ascii_runtime_measurements_tpm_alg_%x%s",
                                 ima_tpm_chip->allocated_banks[i].alg_id,
                                 file_suffix);
                else
                        snprintf(file_name, sizeof(file_name),
                                 "ascii_runtime_measurements_%s%s",
                                 hash_algo_name[algo], file_suffix);
                dentry = securityfs_create_file(file_name, permissions,
                                                ima_dir, (void *)(uintptr_t)i,
                                                ascii_ops);
                if (IS_ERR(dentry))
                        return PTR_ERR(dentry);

                if (algo == HASH_ALGO__LAST)
                        snprintf(file_name, sizeof(file_name),
                                 "binary_runtime_measurements_tpm_alg_%x%s",
                                 ima_tpm_chip->allocated_banks[i].alg_id,
                                 file_suffix);
                else
                        snprintf(file_name, sizeof(file_name),
                                 "binary_runtime_measurements_%s%s",
                                 hash_algo_name[algo], file_suffix);

                dentry = securityfs_create_file(file_name, permissions,
                                                ima_dir, (void *)(uintptr_t)i,
                                                binary_ops);
                if (IS_ERR(dentry))
                        return PTR_ERR(dentry);
        }

        return 0;
}

static int __init create_securityfs_staging_links(void)
{
        struct dentry *dentry;

        dentry = securityfs_create_symlink("binary_runtime_measurements_staged",
                ima_dir, "binary_runtime_measurements_sha1_staged", NULL);
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);

        dentry = securityfs_create_symlink("ascii_runtime_measurements_staged",
                ima_dir, "ascii_runtime_measurements_sha1_staged", NULL);
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);

        return 0;
}

/*
 * ima_open_policy: sequentialize access to the policy file
 */
static int ima_open_policy(struct inode *inode, struct file *filp)
{
        if (!(filp->f_flags & O_WRONLY)) {
#ifndef CONFIG_IMA_READ_POLICY
                return -EACCES;
#else
                if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
                        return -EACCES;
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                return seq_open(filp, &ima_policy_seqops);
#endif
        }
        if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
                return -EBUSY;
        return 0;
}

/*
 * ima_release_policy - start using the new measure policy rules.
 *
 * Initially, ima_measure points to the default policy rules, now
 * point to the new policy rules, and remove the securityfs policy file,
 * assuming a valid policy.
 */
static int ima_release_policy(struct inode *inode, struct file *file)
{
        const char *cause = valid_policy ? "completed" : "failed";

        if ((file->f_flags & O_ACCMODE) == O_RDONLY)
                return seq_release(inode, file);

        if (valid_policy && ima_check_policy() < 0) {
                cause = "failed";
                valid_policy = 0;
        }

        pr_info("policy update %s\n", cause);
        integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
                            "policy_update", cause, !valid_policy, 0);

        if (!valid_policy) {
                ima_delete_rules();
                valid_policy = 1;
                clear_bit(IMA_FS_BUSY, &ima_fs_flags);
                return 0;
        }

        ima_update_policy();
#if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
        securityfs_remove(file->f_path.dentry);
#elif defined(CONFIG_IMA_WRITE_POLICY)
        clear_bit(IMA_FS_BUSY, &ima_fs_flags);
#elif defined(CONFIG_IMA_READ_POLICY)
        inode->i_mode &= ~S_IWUSR;
#endif
        return 0;
}

static const struct file_operations ima_measure_policy_ops = {
        .open = ima_open_policy,
        .write = ima_write_policy,
        .read = seq_read,
        .release = ima_release_policy,
        .llseek = generic_file_llseek,
};

int __init ima_fs_init(void)
{
        struct dentry *dentry;
        int ret;

        ret = integrity_fs_init();
        if (ret < 0)
                return ret;

        ima_dir = securityfs_create_dir("ima", integrity_dir);
        if (IS_ERR(ima_dir)) {
                ret = PTR_ERR(ima_dir);
                goto out;
        }

        ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
                                                NULL);
        if (IS_ERR(ima_symlink)) {
                ret = PTR_ERR(ima_symlink);
                goto out;
        }

        ret = create_securityfs_measurement_lists(false);
        if (ret == 0 && IS_ENABLED(CONFIG_IMA_STAGING)) {
                ret = create_securityfs_measurement_lists(true);
                if (ret == 0)
                        ret = create_securityfs_staging_links();
        }

        if (ret != 0)
                goto out;

        dentry = securityfs_create_symlink("binary_runtime_measurements", ima_dir,
                                      "binary_runtime_measurements_sha1", NULL);
        if (IS_ERR(dentry)) {
                ret = PTR_ERR(dentry);
                goto out;
        }

        dentry = securityfs_create_symlink("ascii_runtime_measurements", ima_dir,
                                      "ascii_runtime_measurements_sha1", NULL);
        if (IS_ERR(dentry)) {
                ret = PTR_ERR(dentry);
                goto out;
        }

        dentry = securityfs_create_file("runtime_measurements_count",
                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
                                   &ima_measurements_count_ops);
        if (IS_ERR(dentry)) {
                ret = PTR_ERR(dentry);
                goto out;
        }

        dentry = securityfs_create_file("violations", S_IRUSR | S_IRGRP,
                                   ima_dir, NULL, &ima_num_violations_ops);
        if (IS_ERR(dentry)) {
                ret = PTR_ERR(dentry);
                goto out;
        }

        dentry = securityfs_create_file("policy", POLICY_FILE_FLAGS,
                                            ima_dir, NULL,
                                            &ima_measure_policy_ops);
        if (IS_ERR(dentry)) {
                ret = PTR_ERR(dentry);
                goto out;
        }

        return 0;
out:
        securityfs_remove(ima_symlink);
        securityfs_remove(ima_dir);
        integrity_fs_fini();

        return ret;
}