[linux-block.git] / security / tomoyo / realpath.c

// 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;

	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';
		/* 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
		 * or dentry without vfsmount.
		 */
		if (!path->mnt ||
		    (!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;
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
c73bd6d4 KT	2	/*
	3	* security/tomoyo/realpath.c
	4	*
0f2a55d5	5	* Copyright (C) 2005-2011 NTT DATA CORPORATION
c73bd6d4 KT	6	*/
c73bd6d4 KT	7
c73bd6d4	8	#include "common.h"
d10577a8	9	#include <linux/magic.h>
c59f415a	10	#include <linux/proc_fs.h>
c73bd6d4 KT	11
c73bd6d4 KT	12	/**
059d84db	13	* tomoyo_encode2 - Encode binary string to ascii string.
c73bd6d4	14	*
059d84db TH	15	* @str: String in binary format.
059d84db TH	16	* @str_len: Size of @str in byte.
c73bd6d4	17	*
c8c57e84 TH	18	* Returns pointer to @str in ascii format on success, NULL otherwise.
	19	*
	20	* This function uses kzalloc(), so caller must kfree() if this function
	21	* didn't return NULL.
c73bd6d4	22	*/
059d84db	23	char tomoyo_encode2(const char str, int str_len)
c73bd6d4	24	{
059d84db	25	int i;
c8c57e84 TH	26	int len = 0;
	27	const char *p = str;
	28	char *cp;
	29	char *cp0;
c73bd6d4	30
c8c57e84 TH	31	if (!p)
c8c57e84 TH	32	return NULL;
059d84db TH	33	for (i = 0; i < str_len; i++) {
	34	const unsigned char c = p[i];
	35
c8c57e84 TH	36	if (c == '\\')
	37	len += 2;
	38	else if (c > ' ' && c < 127)
	39	len++;
	40	else
	41	len += 4;
	42	}
	43	len++;
	44	/* Reserve space for appending "/". */
	45	cp = kzalloc(len + 10, GFP_NOFS);
	46	if (!cp)
	47	return NULL;
	48	cp0 = cp;
	49	p = str;
059d84db TH	50	for (i = 0; i < str_len; i++) {
059d84db TH	51	const unsigned char c = p[i];
c8c57e84 TH	52
	53	if (c == '\\') {
	54	*cp++ = '\\';
	55	*cp++ = '\\';
	56	} else if (c > ' ' && c < 127) {
	57	*cp++ = c;
	58	} else {
	59	*cp++ = '\\';
	60	*cp++ = (c >> 6) + '0';
	61	*cp++ = ((c >> 3) & 7) + '0';
	62	*cp++ = (c & 7) + '0';
c73bd6d4	63	}
c73bd6d4	64	}
c8c57e84	65	return cp0;
c73bd6d4 KT	66	}
c73bd6d4 KT	67
059d84db TH	68	/**
	69	* tomoyo_encode - Encode binary string to ascii string.
	70	*
	71	* @str: String in binary format.
	72	*
	73	* Returns pointer to @str in ascii format on success, NULL otherwise.
	74	*
	75	* This function uses kzalloc(), so caller must kfree() if this function
	76	* didn't return NULL.
	77	*/
	78	char tomoyo_encode(const char str)
	79	{
	80	return str ? tomoyo_encode2(str, strlen(str)) : NULL;
	81	}
	82
5625f2e3 TH	83	/**
	84	* tomoyo_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
	85	*
	86	* @path: Pointer to "struct path".
	87	* @buffer: Pointer to buffer to return value in.
	88	* @buflen: Sizeof @buffer.
	89	*
	90	* Returns the buffer on success, an error code otherwise.
	91	*
	92	* If dentry is a directory, trailing '/' is appended.
	93	*/
22473862	94	static char tomoyo_get_absolute_path(const struct path path, char * const buffer,
5625f2e3 TH	95	const int buflen)
	96	{
	97	char *pos = ERR_PTR(-ENOMEM);
cdcf6723	98
5625f2e3	99	if (buflen >= 256) {
5625f2e3	100	/* go to whatever namespace root we are under */
02125a82	101	pos = d_absolute_path(path, buffer, buflen - 1);
5625f2e3	102	if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
c6f493d6	103	struct inode *inode = d_backing_inode(path->dentry);
cdcf6723	104
5625f2e3 TH	105	if (inode && S_ISDIR(inode->i_mode)) {
	106	buffer[buflen - 2] = '/';
	107	buffer[buflen - 1] = '\0';
	108	}
	109	}
	110	}
	111	return pos;
	112	}
	113
	114	/**
	115	* tomoyo_get_dentry_path - Get the path of a dentry.
	116	*
	117	* @dentry: Pointer to "struct dentry".
	118	* @buffer: Pointer to buffer to return value in.
	119	* @buflen: Sizeof @buffer.
	120	*
	121	* Returns the buffer on success, an error code otherwise.
	122	*
	123	* If dentry is a directory, trailing '/' is appended.
	124	*/
	125	static char tomoyo_get_dentry_path(struct dentry dentry, char * const buffer,
	126	const int buflen)
	127	{
	128	char *pos = ERR_PTR(-ENOMEM);
cdcf6723	129
5625f2e3 TH	130	if (buflen >= 256) {
	131	pos = dentry_path_raw(dentry, buffer, buflen - 1);
	132	if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
c6f493d6	133	struct inode *inode = d_backing_inode(dentry);
cdcf6723	134
5625f2e3 TH	135	if (inode && S_ISDIR(inode->i_mode)) {
	136	buffer[buflen - 2] = '/';
	137	buffer[buflen - 1] = '\0';
	138	}
	139	}
	140	}
	141	return pos;
	142	}
	143
	144	/**
	145	* tomoyo_get_local_path - Get the path of a dentry.
	146	*
	147	* @dentry: Pointer to "struct dentry".
	148	* @buffer: Pointer to buffer to return value in.
	149	* @buflen: Sizeof @buffer.
	150	*
	151	* Returns the buffer on success, an error code otherwise.
	152	*/
	153	static char tomoyo_get_local_path(struct dentry dentry, char * const buffer,
	154	const int buflen)
	155	{
	156	struct super_block *sb = dentry->d_sb;
	157	char *pos = tomoyo_get_dentry_path(dentry, buffer, buflen);
cdcf6723	158
5625f2e3 TH	159	if (IS_ERR(pos))
	160	return pos;
	161	/* Convert from $PID to self if $PID is current thread. */
	162	if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
	163	char *ep;
	164	const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
9d78edea	165	struct pid_namespace *proc_pidns = proc_pid_ns(sb);
cdcf6723	166
5625f2e3	167	if (*ep == '/' && pid && pid ==
c59f415a	168	task_tgid_nr_ns(current, proc_pidns)) {
5625f2e3 TH	169	pos = ep - 5;
	170	if (pos < buffer)
	171	goto out;
	172	memmove(pos, "/self", 5);
	173	}
	174	goto prepend_filesystem_name;
	175	}
	176	/* Use filesystem name for unnamed devices. */
	177	if (!MAJOR(sb->s_dev))
	178	goto prepend_filesystem_name;
	179	{
c6f493d6	180	struct inode *inode = d_backing_inode(sb->s_root);
cdcf6723	181
5625f2e3 TH	182	/*
	183	* Use filesystem name if filesystem does not support rename()
	184	* operation.
	185	*/
2773bf00	186	if (!inode->i_op->rename)
5625f2e3 TH	187	goto prepend_filesystem_name;
	188	}
	189	/* Prepend device name. */
	190	{
	191	char name[64];
	192	int name_len;
	193	const dev_t dev = sb->s_dev;
cdcf6723	194
5625f2e3 TH	195	name[sizeof(name) - 1] = '\0';
	196	snprintf(name, sizeof(name) - 1, "dev(%u,%u):", MAJOR(dev),
	197	MINOR(dev));
	198	name_len = strlen(name);
	199	pos -= name_len;
	200	if (pos < buffer)
	201	goto out;
	202	memmove(pos, name, name_len);
	203	return pos;
	204	}
	205	/* Prepend filesystem name. */
	206	prepend_filesystem_name:
	207	{
	208	const char *name = sb->s_type->name;
	209	const int name_len = strlen(name);
cdcf6723	210
5625f2e3 TH	211	pos -= name_len + 1;
	212	if (pos < buffer)
	213	goto out;
	214	memmove(pos, name, name_len);
	215	pos[name_len] = ':';
	216	}
	217	return pos;
	218	out:
	219	return ERR_PTR(-ENOMEM);
	220	}
	221
c73bd6d4	222	/**
c8c57e84	223	* tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
c73bd6d4	224	*
c8c57e84	225	* @path: Pointer to "struct path".
c73bd6d4	226	*
c8c57e84	227	* Returns the realpath of the given @path on success, NULL otherwise.
c73bd6d4 KT	228	*
	229	* If dentry is a directory, trailing '/' is appended.
	230	* Characters out of 0x20 < c < 0x7F range are converted to
	231	* \ooo style octal string.
	232	* Character \ is converted to \\ string.
c8c57e84 TH	233	*
	234	* These functions use kzalloc(), so the caller must call kfree()
	235	* if these functions didn't return NULL.
c73bd6d4	236	*/
22473862	237	char tomoyo_realpath_from_path(const struct path path)
c73bd6d4	238	{
c8c57e84 TH	239	char *buf = NULL;
	240	char *name = NULL;
	241	unsigned int buf_len = PAGE_SIZE / 2;
c73bd6d4	242	struct dentry *dentry = path->dentry;
5625f2e3	243	struct super_block *sb;
cdcf6723	244
c8c57e84 TH	245	if (!dentry)
c8c57e84 TH	246	return NULL;
5625f2e3	247	sb = dentry->d_sb;
c8c57e84	248	while (1) {
c8c57e84	249	char *pos;
5625f2e3	250	struct inode *inode;
cdcf6723	251
c8c57e84 TH	252	buf_len <<= 1;
	253	kfree(buf);
	254	buf = kmalloc(buf_len, GFP_NOFS);
	255	if (!buf)
	256	break;
5625f2e3 TH	257	/* To make sure that pos is '\0' terminated. */
5625f2e3 TH	258	buf[buf_len - 1] = '\0';
6f7c4137	259	/* For "pipe:[\$]" and "socket:[\$]". */
c8c57e84 TH	260	if (dentry->d_op && dentry->d_op->d_dname) {
c8c57e84 TH	261	pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
5625f2e3	262	goto encode;
c73bd6d4	263	}
c6f493d6	264	inode = d_backing_inode(sb->s_root);
5625f2e3 TH	265	/*
	266	* Get local name for filesystems without rename() operation
	267	* or dentry without vfsmount.
	268	*/
8fe7a268	269	if (!path->mnt \|\|
27df4b4a TH	270	(!inode->i_op->rename &&
27df4b4a TH	271	!(sb->s_type->fs_flags & FS_REQUIRES_DEV)))
5625f2e3 TH	272	pos = tomoyo_get_local_path(path->dentry, buf,
	273	buf_len - 1);
	274	/* Get absolute name for the rest. */
1418a3e5	275	else {
5625f2e3	276	pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
1418a3e5 TH	277	/*
	278	* Fall back to local name if absolute name is not
	279	* available.
	280	*/
	281	if (pos == ERR_PTR(-EINVAL))
	282	pos = tomoyo_get_local_path(path->dentry, buf,
	283	buf_len - 1);
	284	}
5625f2e3	285	encode:
c8c57e84 TH	286	if (IS_ERR(pos))
	287	continue;
	288	name = tomoyo_encode(pos);
	289	break;
c73bd6d4	290	}
8e2d39a1	291	kfree(buf);
c8c57e84 TH	292	if (!name)
c8c57e84 TH	293	tomoyo_warn_oom(__func__);
c8c57e84	294	return name;
c73bd6d4 KT	295	}
c73bd6d4 KT	296
c73bd6d4 KT	297	/**
	298	* tomoyo_realpath_nofollow - Get realpath of a pathname.
	299	*
	300	* @pathname: The pathname to solve.
	301	*
	302	* Returns the realpath of @pathname on success, NULL otherwise.
	303	*/
	304	char tomoyo_realpath_nofollow(const char pathname)
	305	{
e24977d4	306	struct path path;
c73bd6d4	307
e24977d4 AV	308	if (pathname && kern_path(pathname, 0, &path) == 0) {
e24977d4 AV	309	char *buf = tomoyo_realpath_from_path(&path);
cdcf6723	310
e24977d4	311	path_put(&path);
c73bd6d4 KT	312	return buf;
	313	}
	314	return NULL;
	315	}