From 4f95ab1f8110a8ab9d7b0e192731ce467f6e5c26 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Janne=20He=C3=9F?= Date: Sun, 4 Sep 2022 11:15:02 -0600 Subject: [PATCH] Allow loading token handlers from the default search path Since [1] landed in cryptsetup, token handlers (libcryptsetup-token-*.so) are loaded from a fixed path defined at compile-time. This is problematic with NixOS since it introduces a dependency cycle between cryptsetup and systemd. This downstream patch [2] allows loading token plugins from the default library search path. This approach is not accepted upstream [3] due to security concerns, but the potential attack vectors require root access and they are sufficiently addressed: * cryptsetup could be used as a setuid binary (not used in NixOS). In this case, LD_LIBRARY_PATH is ignored because of secure-execution mode. * cryptsetup running as root could lead to a malicious token handler being loaded through LD_LIBRARY_PATH. However, fixing the path doesn't prevent the same malicious .so being loaded through LD_PRELOAD. [1] https://gitlab.com/cryptsetup/cryptsetup/-/commit/5b9e98f94178d3cd179d9f6e2a0a68c7d9eb6507 [2] https://github.com/NixOS/nixpkgs/issues/167994#issuecomment-1094249369 [3] https://gitlab.com/cryptsetup/cryptsetup/-/issues/733 --- lib/luks2/luks2_token.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/lib/luks2/luks2_token.c b/lib/luks2/luks2_token.c index 26467253..6f8329f0 100644 --- a/lib/luks2/luks2_token.c +++ b/lib/luks2/luks2_token.c @@ -151,12 +151,10 @@ crypt_token_load_external(struct crypt_device *cd, const char *name, struct cryp token = &ret->u.v2; - r = snprintf(buf, sizeof(buf), "%s/libcryptsetup-token-%s.so", crypt_token_external_path(), name); + r = snprintf(buf, sizeof(buf), "libcryptsetup-token-%s.so", name); if (r < 0 || (size_t)r >= sizeof(buf)) return -EINVAL; - assert(*buf == '/'); - log_dbg(cd, "Trying to load %s.", buf); h = dlopen(buf, RTLD_LAZY); -- 2.37.2