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Update chroot symlink check #765

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Update chroot symlink check #765

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4192de8
start sftp chroot symlink fix
tgauth Oct 17, 2024
3624760
update symlink logic chroot check
tgauth Nov 18, 2024
48969a4
fix order
tgauth Nov 18, 2024
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36 changes: 27 additions & 9 deletions contrib/win32/win32compat/fileio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -435,14 +435,20 @@ file_in_chroot_jail(HANDLE handle) {
return 1;
}

return file_in_chroot_jail_helper(final_path);
}

/* returns 1 if true, 0 otherwise */
int
file_in_chroot_jail_helper(wchar_t* final_path) {
/* ensure final path is within chroot */
to_wlower_case(final_path);
if ((wcslen(final_path) < wcslen(chroot_pathw)) ||
memcmp(final_path, chroot_pathw, 2 * wcslen(chroot_pathw)) != 0 ||
final_path[wcslen(chroot_pathw)] != '\\') {
memcmp(final_path, chroot_pathw, 2 * wcslen(chroot_pathw)) != 0 ||
final_path[wcslen(chroot_pathw)] != '\\') {
debug3("access denied due to attempt to escape chroot jail");
return 0;
}

return 1;
}

Expand Down Expand Up @@ -1268,6 +1274,7 @@ fileio_symlink(const char *target, const char *linkpath)
DWORD ret = -1;
char target_modified[PATH_MAX] = { 0 };
char *linkpath_resolved = NULL, *target_resolved = NULL;
wchar_t *linkpath_utf16 = NULL, *resolved_target_utf16 = NULL, *resolved_target_chroot = NULL;

if (target == NULL || linkpath == NULL) {
errno = EFAULT;
Expand Down Expand Up @@ -1301,13 +1308,21 @@ fileio_symlink(const char *target, const char *linkpath)
strcpy_s(target_modified, _countof(target_modified), target_resolved);
}

wchar_t *linkpath_utf16 = resolved_path_utf16(linkpath);
wchar_t *resolved_target_utf16 = utf8_to_utf16(target_modified);
if (resolved_target_utf16 == NULL || linkpath_utf16 == NULL) {
if ((linkpath_utf16 = resolved_path_utf16(linkpath)) == NULL ||
(resolved_target_utf16 = utf8_to_utf16(target_modified)) == NULL) {
errno = ENOMEM;
goto cleanup;
}

/* if chroot, get full path for target, similar to behavior in realpath() in misc.c
note: _wfullpath() is required to resolve paths containing unicode characters */
if (chroot_pathw != NULL &&
(resolved_target_chroot = _wfullpath(NULL, resolved_target_utf16, 0)) != NULL &&
file_in_chroot_jail_helper(resolved_target_chroot) != 1) {
errno = EPERM;
goto cleanup;
}

/* unlike other platforms, we need to know whether the symbolic link target is
* a file or a directory. the only way we can confidently do this is to
* get the attributes of the target. therefore, our symlink() has the
Expand Down Expand Up @@ -1338,15 +1353,18 @@ fileio_symlink(const char *target, const char *linkpath)
ret = 0;
cleanup:

if (linkpath_resolved)
free(linkpath_resolved);

if (linkpath_utf16)
free(linkpath_utf16);

if (resolved_target_chroot)
free(resolved_target_chroot);

if (resolved_target_utf16)
free(resolved_target_utf16);

if (linkpath_resolved)
free(linkpath_resolved);

if (target_resolved)
free(target_resolved);

Expand Down
1 change: 1 addition & 0 deletions contrib/win32/win32compat/misc_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,7 @@ int load_user_profile(HANDLE user_token, char* user);
int create_directory_withsddl(wchar_t *path, wchar_t *sddl);
int is_absolute_path(const char *);
int file_in_chroot_jail(HANDLE);
int file_in_chroot_jail_helper(wchar_t*);
PSID lookup_sid(const wchar_t* name_utf16, PSID psid, DWORD * psid_len);
PSID get_sid(const char*);
int am_system();
Expand Down