// SPDX-License-Identifier: GPL-2.0
/*
 * security/tomoyo/realpath.c
 *
 * Copyright (C) 2005-2011  NTT DATA CORPORATION
 */

#include "common.h"
#include <linux/magic.h>
#include <linux/proc_fs.h>

/**
 * tomoyo_encode2 - Encode binary string to ascii string.
 *
 * @str:     String in binary format.
 * @str_len: Size of @str in byte.
 *
 * Returns pointer to @str in ascii format on success, NULL otherwise.
 *
 * This function uses kzalloc(), so caller must kfree() if this function
 * didn't return NULL.
 */
char *tomoyo_encode2(const char *str, int str_len)
{
        int i;
        int len = 0;
        const char *p = str;
        char *cp;
        char *cp0;

        if (!p)
                return NULL;
        for (i = 0; i < str_len; i++) {
                const unsigned char c = p[i];

                if (c == '\\')
                        len += 2;
                else if (c > ' ' && c < 127)
                        len++;
                else
                        len += 4;
        }
        len++;
        /* Reserve space for appending "/". */
        cp = kzalloc(len + 10, GFP_NOFS);
        if (!cp)
                return NULL;
        cp0 = cp;
        p = str;
        for (i = 0; i < str_len; i++) {
                const unsigned char c = p[i];

                if (c == '\\') {
                        *cp++ = '\\';
                        *cp++ = '\\';
                } else if (c > ' ' && c < 127) {
                        *cp++ = c;
                } else {
                        *cp++ = '\\';
                        *cp++ = (c >> 6) + '0';
                        *cp++ = ((c >> 3) & 7) + '0';
                        *cp++ = (c & 7) + '0';
                }
        }
        return cp0;
}

/**
 * tomoyo_encode - Encode binary string to ascii string.
 *
 * @str: String in binary format.
 *
 * Returns pointer to @str in ascii format on success, NULL otherwise.
 *
 * This function uses kzalloc(), so caller must kfree() if this function
 * didn't return NULL.
 */
char *tomoyo_encode(const char *str)
{
        return str ? tomoyo_encode2(str, strlen(str)) : NULL;
}

/**
 * tomoyo_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
 *
 * @path:   Pointer to "struct path".
 * @buffer: Pointer to buffer to return value in.
 * @buflen: Sizeof @buffer.
 *
 * Returns the buffer on success, an error code otherwise.
 *
 * If dentry is a directory, trailing '/' is appended.
 */
static char *tomoyo_get_absolute_path(const struct path *path, char * const buffer,
                                      const int buflen)
{
        char *pos = ERR_PTR(-ENOMEM);

        if (buflen >= 256) {
                /* go to whatever namespace root we are under */
                pos = d_absolute_path(path, buffer, buflen - 1);
                if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
                        struct inode *inode = d_backing_inode(path->dentry);

                        if (inode && S_ISDIR(inode->i_mode)) {
                                buffer[buflen - 2] = '/';
                                buffer[buflen - 1] = '\0';
                        }
                }
        }
        return pos;
}

/**
 * tomoyo_get_dentry_path - Get the path of a dentry.
 *
 * @dentry: Pointer to "struct dentry".
 * @buffer: Pointer to buffer to return value in.
 * @buflen: Sizeof @buffer.
 *
 * Returns the buffer on success, an error code otherwise.
 *
 * If dentry is a directory, trailing '/' is appended.
 */
static char *tomoyo_get_dentry_path(struct dentry *dentry, char * const buffer,
                                    const int buflen)
{
        char *pos = ERR_PTR(-ENOMEM);

        if (buflen >= 256) {
                pos = dentry_path_raw(dentry, buffer, buflen - 1);
                if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
                        struct inode *inode = d_backing_inode(dentry);

                        if (inode && S_ISDIR(inode->i_mode)) {
                                buffer[buflen - 2] = '/';
                                buffer[buflen - 1] = '\0';
                        }
                }
        }
        return pos;
}

/**
 * tomoyo_get_local_path - Get the path of a dentry.
 *
 * @dentry: Pointer to "struct dentry".
 * @buffer: Pointer to buffer to return value in.
 * @buflen: Sizeof @buffer.
 *
 * Returns the buffer on success, an error code otherwise.
 */
static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
                                   const int buflen)
{
        struct super_block *sb = dentry->d_sb;
        char *pos = tomoyo_get_dentry_path(dentry, buffer, buflen);

        if (IS_ERR(pos))
                return pos;
        /* Convert from $PID to self if $PID is current thread. */
        if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
                char *ep;
                const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
                struct pid_namespace *proc_pidns = proc_pid_ns(sb);

                if (*ep == '/' && pid && pid ==
                    task_tgid_nr_ns(current, proc_pidns)) {
                        pos = ep - 5;
                        if (pos < buffer)
                                goto out;
                        memmove(pos, "/self", 5);
                }
                goto prepend_filesystem_name;
        }
        /* Use filesystem name for unnamed devices. */
        if (!MAJOR(sb->s_dev))
                goto prepend_filesystem_name;
        {
                struct inode *inode = d_backing_inode(sb->s_root);

                /*
                 * Use filesystem name if filesystem does not support rename()
                 * operation.
                 */
                if (!inode->i_op->rename)
                        goto prepend_filesystem_name;
        }
        /* Prepend device name. */
        {
                char name[64];
                int name_len;
                const dev_t dev = sb->s_dev;

                name[sizeof(name) - 1] = '\0';
                snprintf(name, sizeof(name) - 1, "dev(%u,%u):", MAJOR(dev),
                         MINOR(dev));
                name_len = strlen(name);
                pos -= name_len;
                if (pos < buffer)
                        goto out;
                memmove(pos, name, name_len);
                return pos;
        }
        /* Prepend filesystem name. */
prepend_filesystem_name:
        {
                const char *name = sb->s_type->name;
                const int name_len = strlen(name);

                pos -= name_len + 1;
                if (pos < buffer)
                        goto out;
                memmove(pos, name, name_len);
                pos[name_len] = ':';
        }
        return pos;
out:
        return ERR_PTR(-ENOMEM);
}

/**
 * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 *
 * @path: Pointer to "struct path".
 *
 * Returns the realpath of the given @path on success, NULL otherwise.
 *
 * If dentry is a directory, trailing '/' is appended.
 * Characters out of 0x20 < c < 0x7F range are converted to
 * \ooo style octal string.
 * Character \ is converted to \\ string.
 *
 * These functions use kzalloc(), so the caller must call kfree()
 * if these functions didn't return NULL.
 */
char *tomoyo_realpath_from_path(const struct path *path)
{
        char *buf = NULL;
        char *name = NULL;
        unsigned int buf_len = PAGE_SIZE / 2;
        struct dentry *dentry = path->dentry;
        struct super_block *sb = dentry->d_sb;

        while (1) {
                char *pos;
                struct inode *inode;

                buf_len <<= 1;
                kfree(buf);
                buf = kmalloc(buf_len, GFP_NOFS);
                if (!buf)
                        break;
                /* To make sure that pos is '\0' terminated. */
                buf[buf_len - 1] = '\0';
                /* For "pipe:[\$]" and "socket:[\$]". */
                if (dentry->d_op && dentry->d_op->d_dname) {
                        pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
                        goto encode;
                }
                inode = d_backing_inode(sb->s_root);
                /*
                 * Get local name for filesystems without rename() operation
                 */
                if ((!inode->i_op->rename &&
                     !(sb->s_type->fs_flags & FS_REQUIRES_DEV)))
                        pos = tomoyo_get_local_path(path->dentry, buf,
                                                    buf_len - 1);
                /* Get absolute name for the rest. */
                else {
                        pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
                        /*
                         * Fall back to local name if absolute name is not
                         * available.
                         */
                        if (pos == ERR_PTR(-EINVAL))
                                pos = tomoyo_get_local_path(path->dentry, buf,
                                                            buf_len - 1);
                }
encode:
                if (IS_ERR(pos))
                        continue;
                name = tomoyo_encode(pos);
                break;
        }
        kfree(buf);
        if (!name)
                tomoyo_warn_oom(__func__);
        return name;
}

/**
 * tomoyo_realpath_nofollow - Get realpath of a pathname.
 *
 * @pathname: The pathname to solve.
 *
 * Returns the realpath of @pathname on success, NULL otherwise.
 */
char *tomoyo_realpath_nofollow(const char *pathname)
{
        struct path path;

        if (pathname && kern_path(pathname, 0, &path) == 0) {
                char *buf = tomoyo_realpath_from_path(&path);

                path_put(&path);
                return buf;
        }
        return NULL;
}