1 files changed, 310 insertions, 0 deletions
diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c
new file mode 100644
index 000000000..1c483ee7f
--- /dev/null
+++ b/security/tomoyo/realpath.c
@@ -0,0 +1,310 @@
+// 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;
+}