/*
   * security/tomoyo/realpath.c
   *
   * Copyright (C) 2005-2011  NTT DATA CORPORATION
   */
  
  #include "common.h"
  #include <linux/magic.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(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 = path->dentry->d_inode;
  			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 = dentry->d_inode;
  			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);
  		if (*ep == '/' && pid && pid ==
  		    task_tgid_nr_ns(current, sb->s_fs_info)) {
  			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 = sb->s_root->d_inode;
  		/*
  		 * Use filesystem name if filesystem does not support rename()
  		 * operation.
  		 */
  		if (inode->i_op && !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_get_socket_name - Get the name of a socket.
   *
   * @path:   Pointer to "struct path".
   * @buffer: Pointer to buffer to return value in.
   * @buflen: Sizeof @buffer.
   *
   * Returns the buffer.
   */
  static char *tomoyo_get_socket_name(struct path *path, char * const buffer,
  				    const int buflen)
  {
  	struct inode *inode = path->dentry->d_inode;
  	struct socket *sock = inode ? SOCKET_I(inode) : NULL;
  	struct sock *sk = sock ? sock->sk : NULL;
  	if (sk) {
  		snprintf(buffer, buflen, "socket:[family=%u:type=%u:"
  			 "protocol=%u]", sk->sk_family, sk->sk_type,
  			 sk->sk_protocol);
  	} else {
  		snprintf(buffer, buflen, "socket:[unknown]");
  	}
  	return buffer;
  }
  
  /**
   * 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(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;
  	if (!dentry)
  		return NULL;
  	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';
  		/* Get better name for socket. */
  		if (sb->s_magic == SOCKFS_MAGIC) {
  			pos = tomoyo_get_socket_name(path, buf, buf_len - 1);
  			goto encode;
  		}
  		/* For "pipe:[\$]". */
  		if (dentry->d_op && dentry->d_op->d_dname) {
  			pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
  			goto encode;
  		}
  		inode = sb->s_root->d_inode;
  		/*
  		 * Get local name for filesystems without rename() operation
  		 * or dentry without vfsmount.
  		 */
  		if (!path->mnt || (inode->i_op && !inode->i_op->rename))
  			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;
  }