From c78e53edb802d04f7e4e070fe8314f2544749e7a Mon Sep 17 00:00:00 2001 From: Andrew Tridgell Date: Tue, 26 Nov 2024 09:16:31 +1100 Subject: [PATCH 4/4] disallow ../ elements in relpath for secure_relative_open --- syscall.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/syscall.c b/syscall.c index a4b7f542..47c5ea57 100644 --- a/syscall.c +++ b/syscall.c @@ -721,6 +721,8 @@ int do_open_nofollow(const char *pathname, int flags) must be a relative path, and the relpath must not contain any elements in the path which follow symlinks (ie. like O_NOFOLLOW, but applies to all path components, not just the last component) + + The relpath must also not contain any ../ elements in the path */ int secure_relative_open(const char *basedir, const char *relpath, int flags, mode_t mode) { @@ -729,6 +731,11 @@ int secure_relative_open(const char *basedir, const char *relpath, int flags, mo errno = EINVAL; return -1; } + if (strncmp(relpath, "../", 3) == 0 || strstr(relpath, "/../")) { + // no ../ elements allowed in the relpath + errno = EINVAL; + return -1; + } #if !defined(O_NOFOLLOW) || !defined(O_DIRECTORY) // really old system, all we can do is live with the risks -- 2.34.1