[PATCH 08/10] CaitSith: Add pathname calculation functions.
Tetsuo Handa
penguin-kernel at I-love.SAKURA.ne.jp
Wed Nov 2 17:10:23 UTC 2022
This file implements similar functions provided by
security/tomoyo/realpath.c file.
Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
---
security/caitsith/realpath.c | 415 +++++++++++++++++++++++++++++++++++
1 file changed, 415 insertions(+)
create mode 100644 security/caitsith/realpath.c
diff --git a/security/caitsith/realpath.c b/security/caitsith/realpath.c
new file mode 100644
index 000000000000..ed6b1407a54d
--- /dev/null
+++ b/security/caitsith/realpath.c
@@ -0,0 +1,415 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * realpath.c
+ *
+ * Copyright (C) 2005-2012 NTT DATA CORPORATION
+ *
+ * Version: 0.2.10 2021/06/06
+ */
+
+#include "caitsith.h"
+
+#include <linux/proc_fs.h>
+
+/***** SECTION1: Constants definition *****/
+
+/***** SECTION2: Structure definition *****/
+
+/***** SECTION3: Prototype definition section *****/
+
+static char *cs_get_absolute_path(const struct path *path, char * const buffer,
+ const int buflen);
+static char *cs_get_dentry_path(struct dentry *dentry, char * const buffer,
+ const int buflen);
+static char *cs_get_local_path(struct dentry *dentry, char * const buffer,
+ const int buflen);
+static int cs_const_part_length(const char *filename);
+
+/***** SECTION4: Standalone functions section *****/
+
+/**
+ * cs_realpath_lock - Take locks for __d_path().
+ *
+ * Returns nothing.
+ */
+static inline void cs_realpath_lock(void)
+{
+ /* dcache_lock is locked by __d_path(). */
+ /* vfsmount_lock is locked by __d_path(). */
+}
+
+/**
+ * cs_realpath_unlock - Release locks for __d_path().
+ *
+ * Returns nothing.
+ */
+static inline void cs_realpath_unlock(void)
+{
+ /* vfsmount_lock is unlocked by __d_path(). */
+ /* dcache_lock is unlocked by __d_path(). */
+}
+
+/***** SECTION5: Variables definition section *****/
+
+/***** SECTION6: Dependent functions section *****/
+
+/**
+ * cs_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.
+ *
+ * Caller holds the dcache_lock and vfsmount_lock.
+ * Based on __d_path() in fs/dcache.c
+ */
+static char *cs_get_absolute_path(const struct path *path, char * const buffer,
+ const int buflen)
+{
+ if (buflen < 256)
+ return ERR_PTR(-ENOMEM);
+ return d_absolute_path(path, buffer, buflen - 1);
+}
+
+/**
+ * cs_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.
+ *
+ * Based on dentry_path() in fs/dcache.c
+ */
+static char *cs_get_dentry_path(struct dentry *dentry, char * const buffer,
+ const int buflen)
+{
+ if (buflen < 256)
+ return ERR_PTR(-ENOMEM);
+ /* rename_lock is locked/unlocked by dentry_path_raw(). */
+ return dentry_path_raw(dentry, buffer, buflen - 1);
+}
+
+/**
+ * cs_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 *cs_get_local_path(struct dentry *dentry, char * const buffer,
+ const int buflen)
+{
+ struct super_block *sb = dentry->d_sb;
+ char *pos = cs_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, proc_pid_ns(sb))) {
+ 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 filesystems 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);
+}
+
+/**
+ * cs_realpath - 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.
+ *
+ * This function uses kzalloc(), so caller must kfree() if this function
+ * didn't return NULL.
+ */
+char *cs_realpath(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);
+ /*
+ * Use local name for "filesystems without rename() operation
+ * and device file" or "path without vfsmount" or "absolute
+ * name is unavailable" cases.
+ */
+ if (!path->mnt ||
+ (!inode->i_op->rename &&
+ !(sb->s_type->fs_flags & FS_REQUIRES_DEV)))
+ pos = ERR_PTR(-EINVAL);
+ else
+ pos = cs_get_absolute_path(path, buf, buf_len - 1);
+ if (pos == ERR_PTR(-EINVAL))
+ pos = cs_get_local_path(path->dentry, buf,
+ buf_len - 1);
+encode:
+ if (IS_ERR(pos))
+ continue;
+ name = cs_encode(pos);
+ break;
+ }
+ kfree(buf);
+ if (!name)
+ cs_warn_oom(__func__);
+ return name;
+}
+
+/**
+ * cs_encode2 - Encode binary string to ascii string.
+ *
+ * @str: String in binary format. Maybe NULL.
+ * @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 *cs_encode2(const char *str, int str_len)
+{
+ int i;
+ int len;
+ const char *p = str;
+ char *cp;
+ char *cp0;
+
+ if (!p)
+ return NULL;
+ len = str_len;
+ for (i = 0; i < str_len; i++) {
+ const unsigned char c = p[i];
+
+ if (!(c > ' ' && c < 127 && c != '\\'))
+ len += 3;
+ }
+ len++;
+ cp = kzalloc(len, 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 > ' ' && c < 127 && c != '\\') {
+ *cp++ = c;
+ } else {
+ *cp++ = '\\';
+ *cp++ = (c >> 6) + '0';
+ *cp++ = ((c >> 3) & 7) + '0';
+ *cp++ = (c & 7) + '0';
+ }
+ }
+ return cp0;
+}
+
+/**
+ * cs_encode - Encode binary string to ascii string.
+ *
+ * @str: String in binary format. Maybe NULL.
+ *
+ * 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 *cs_encode(const char *str)
+{
+ return str ? cs_encode2(str, strlen(str)) : NULL;
+}
+
+/**
+ * cs_const_part_length - Evaluate the initial length without a pattern in a token.
+ *
+ * @filename: The string to evaluate. Maybe NULL.
+ *
+ * Returns the initial length without a pattern in @filename.
+ */
+static int cs_const_part_length(const char *filename)
+{
+ char c;
+ int len = 0;
+
+ if (!filename)
+ return 0;
+ while (1) {
+ c = *filename++;
+ if (!c)
+ break;
+ if (c != '\\') {
+ len++;
+ continue;
+ }
+ c = *filename++;
+ switch (c) {
+ case '0': /* "\ooo" */
+ case '1':
+ case '2':
+ case '3':
+ c = *filename++;
+ if (c < '0' || c > '7')
+ break;
+ c = *filename++;
+ if (c < '0' || c > '7')
+ break;
+ len += 4;
+ continue;
+ }
+ break;
+ }
+ return len;
+}
+
+/**
+ * cs_fill_path_info - Fill in "struct cs_path_info" members.
+ *
+ * @ptr: Pointer to "struct cs_path_info" to fill in.
+ *
+ * Returns nothing.
+ *
+ * The caller sets "struct cs_path_info"->name.
+ */
+void cs_fill_path_info(struct cs_path_info *ptr)
+{
+ const char *name = ptr->name;
+ const int len = strlen(name);
+
+ ptr->total_len = len;
+ ptr->const_len = cs_const_part_length(name);
+ ptr->hash = full_name_hash(NULL, name, len);
+}
+
+/**
+ * cs_get_exe - Get cs_realpath() of current process.
+ *
+ * Returns the cs_realpath() of current process on success, NULL otherwise.
+ *
+ * This function uses kzalloc(), so the caller must kfree()
+ * if this function didn't return NULL.
+ */
+char *cs_get_exe(void)
+{
+ struct mm_struct *mm;
+ struct file *exe_file;
+
+ if (current->flags & PF_KTHREAD)
+ return kstrdup("<kernel>", GFP_NOFS);
+ mm = current->mm;
+ if (!mm)
+ goto task_has_no_mm;
+ /* Not using get_mm_exe_file() as it is not exported. */
+ rcu_read_lock();
+ exe_file = rcu_dereference(mm->exe_file);
+ if (exe_file && !get_file_rcu(exe_file))
+ exe_file = NULL;
+ rcu_read_unlock();
+ if (exe_file) {
+ char *cp = cs_realpath(&exe_file->f_path);
+
+ fput(exe_file);
+ return cp;
+ }
+task_has_no_mm:
+ /* I'don't know. */
+ return kstrdup("<unknown>", GFP_NOFS);
+}
+
+/**
+ * cs_get_exename - Get cs_realpath() of current process.
+ *
+ * @buf: Pointer to "struct cs_path_info".
+ *
+ * Returns true on success, false otherwise.
+ *
+ * This function uses kzalloc(), so the caller must kfree()
+ * if this function returned true.
+ */
+bool cs_get_exename(struct cs_path_info *buf)
+{
+ buf->name = cs_get_exe();
+ if (buf->name) {
+ cs_fill_path_info(buf);
+ return true;
+ }
+ return false;
+}
--
2.18.4
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