[Openvpn-devel] [PATCH v4] Load OpenSSL config on Windows from trusted location

From: Lev Stipakov <le...@op...> Commits - 92535b6 ("contrib/vcpkg-ports: add openssl port with --no-autoload-config option set (CVE-2121-3606)") - 447cfb4 ("crypto_openssl.c: disable explicit initialization on Windows (CVE-2121-3606)") disabled OpenSSL config loading functionality, which could be exploited by loading config from untrusted locations. This feature might be useful for some users. This brings it back and sets OpenSSL enviroment variables OPENSSL_CONF, OPENSSL_ENGINES, OPENSSL_MODULES which are used to load config, engines and modules, to a trusted location. The location is constructed based on installation path, read from registry on startup. If installation path cannot be read, Windows\System32 is used as a fallback. While on it, remove unused "bool impersonate_as_system();" declaration. Signed-off-by: Lev Stipakov <le...@op...> --- v4: - make set_openssl_env_vars() code more succint - use security-enhanced _wputenv_s/_wgetenv_s v3: - do not assume that installation path ends with directory separator - set enviroment variables only if they're not already set - bring back explicit initialization on Windows (might be needed on some cases) - slightly revamp commit message v2: - add missing "static" modifier to set_openssl_env_vars() declaration spotted by gcc .../vcpkg-triplets/arm64-windows-ovpn.cmake | 2 - contrib/vcpkg-triplets/x64-windows-ovpn.cmake | 2 - contrib/vcpkg-triplets/x86-windows-ovpn.cmake | 2 - src/openvpn/buffer.c | 23 ----- src/openvpn/crypto_openssl.c | 2 - src/openvpn/win32.c | 88 +++++++++++++++++++ src/openvpn/win32.h | 8 +- 7 files changed, 95 insertions(+), 32 deletions(-) diff --git a/contrib/vcpkg-triplets/arm64-windows-ovpn.cmake b/contrib/vcpkg-triplets/arm64-windows-ovpn.cmake index 89f6a279..dd3c6c0a 100644 --- a/contrib/vcpkg-triplets/arm64-windows-ovpn.cmake +++ b/contrib/vcpkg-triplets/arm64-windows-ovpn.cmake @@ -5,5 +5,3 @@ set(VCPKG_LIBRARY_LINKAGE dynamic) if(PORT STREQUAL "lz4") set(VCPKG_LIBRARY_LINKAGE static) endif() - -set(OPENSSL_NO_AUTOLOAD_CONFIG ON) diff --git a/contrib/vcpkg-triplets/x64-windows-ovpn.cmake b/contrib/vcpkg-triplets/x64-windows-ovpn.cmake index d860eed6..7036ed2d 100644 --- a/contrib/vcpkg-triplets/x64-windows-ovpn.cmake +++ b/contrib/vcpkg-triplets/x64-windows-ovpn.cmake @@ -5,5 +5,3 @@ set(VCPKG_LIBRARY_LINKAGE dynamic) if(PORT STREQUAL "lz4") set(VCPKG_LIBRARY_LINKAGE static) endif() - -set(OPENSSL_NO_AUTOLOAD_CONFIG ON) diff --git a/contrib/vcpkg-triplets/x86-windows-ovpn.cmake b/contrib/vcpkg-triplets/x86-windows-ovpn.cmake index c1ea6ef3..7d3bf340 100644 --- a/contrib/vcpkg-triplets/x86-windows-ovpn.cmake +++ b/contrib/vcpkg-triplets/x86-windows-ovpn.cmake @@ -5,5 +5,3 @@ set(VCPKG_LIBRARY_LINKAGE dynamic) if(PORT STREQUAL "lz4") set(VCPKG_LIBRARY_LINKAGE static) endif() - -set(OPENSSL_NO_AUTOLOAD_CONFIG ON) diff --git a/src/openvpn/buffer.c b/src/openvpn/buffer.c index c82d3d4d..54e758af 100644 --- a/src/openvpn/buffer.c +++ b/src/openvpn/buffer.c @@ -310,29 +310,6 @@ openvpn_snprintf(char *str, size_t size, const char *format, ...) return (len >= 0 && len < size); } -/* - * openvpn_swprintf() is currently only used by Windows code paths - * and when enabled for all platforms it will currently break older - * OpenBSD versions lacking vswprintf(3) support in their libc. - */ - -#ifdef _WIN32 -bool -openvpn_swprintf(wchar_t *const str, const size_t size, const wchar_t *const format, ...) -{ - va_list arglist; - int len = -1; - if (size > 0) - { - va_start(arglist, format); - len = vswprintf(str, size, format, arglist); - va_end(arglist); - str[size - 1] = L'\0'; - } - return (len >= 0 && len < size); -} -#endif - /* * write a string to the end of a buffer that was * truncated by buf_printf diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c index c9dc9d0a..ef520928 100644 --- a/src/openvpn/crypto_openssl.c +++ b/src/openvpn/crypto_openssl.c @@ -154,13 +154,11 @@ crypto_init_lib_engine(const char *engine_name) void crypto_init_lib(void) { -#ifndef _WIN32 #if (OPENSSL_VERSION_NUMBER >= 0x10100000L) OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CONFIG, NULL); #else OPENSSL_config(NULL); #endif -#endif /* _WIN32 */ /* * If you build the OpenSSL library and OpenVPN with * CRYPTO_MDEBUG, you will get a listing of OpenSSL diff --git a/src/openvpn/win32.c b/src/openvpn/win32.c index 6cff17b2..ee4d3f66 100644 --- a/src/openvpn/win32.c +++ b/src/openvpn/win32.c @@ -101,6 +101,12 @@ struct semaphore netcmd_semaphore; /* GLOBAL */ */ static char *win_sys_path = NULL; /* GLOBAL */ +/** + * Set OpenSSL environment variables to a safe directory + */ +static void +set_openssl_env_vars(); + void init_win32(void) { @@ -110,6 +116,8 @@ init_win32(void) } window_title_clear(&window_title); win32_signal_clear(&win32_signal); + + set_openssl_env_vars(); } void @@ -1509,4 +1517,84 @@ send_msg_iservice(HANDLE pipe, const void *data, size_t size, return ret; } +bool +openvpn_swprintf(wchar_t* const str, const size_t size, const wchar_t* const format, ...) +{ + va_list arglist; + int len = -1; + if (size > 0) + { + va_start(arglist, format); + len = vswprintf(str, size, format, arglist); + va_end(arglist); + str[size - 1] = L'\0'; + } + return (len >= 0 && len < size); +} + +static BOOL +get_install_path(WCHAR *path, DWORD size) +{ + WCHAR reg_path[256]; + HKEY key; + BOOL res = FALSE; + openvpn_swprintf(reg_path, _countof(reg_path), L"SOFTWARE\\" PACKAGE_NAME); + + LONG status = RegOpenKeyExW(HKEY_LOCAL_MACHINE, reg_path, 0, KEY_READ, &key); + if (status != ERROR_SUCCESS) + { + return res; + } + + /* The default value of REG_KEY is the install path */ + status = RegGetValueW(key, NULL, NULL, RRF_RT_REG_SZ, NULL, (LPBYTE)path, &size); + res = status == ERROR_SUCCESS; + + RegCloseKey(key); + + return res; +} + +static void +set_openssl_env_vars() +{ + const WCHAR* ssl_fallback_dir = L"C:\\Windows\\System32"; + + WCHAR install_path[MAX_PATH] = { 0 }; + if (!get_install_path(install_path, _countof(install_path))) + { + /* if we cannot find installation path from the registry, + * use Windows directory as a fallback + */ + openvpn_swprintf(install_path, _countof(install_path), L"%ls", ssl_fallback_dir); + } + + if ((install_path[wcslen(install_path) - 1]) == L'\\') + { + install_path[wcslen(install_path) - 1] = L'\0'; + } + + static struct { + WCHAR* name; + WCHAR* value; + } ossl_env[] = { + {L"OPENSSL_CONF", L"openssl.cnf"}, + {L"OPENSSL_ENGINES", L"engines"}, + {L"OPENSSL_MODULES", L"modules"} + }; + + for (size_t i = 0; i < SIZE(ossl_env); ++i) + { + size_t size = 0; + + _wgetenv_s(&size, NULL, 0, ossl_env[i].name); + if (size == 0) + { + WCHAR val[MAX_PATH] = {0}; + openvpn_swprintf(val, _countof(val), L"%ls\\ssl\\%ls", install_path, ossl_env[i].value); + _wputenv_s(ossl_env[i].name, val); + } + } +} + #endif /* ifdef _WIN32 */ diff --git a/src/openvpn/win32.h b/src/openvpn/win32.h index 5d3371a0..4a992d91 100644 --- a/src/openvpn/win32.h +++ b/src/openvpn/win32.h @@ -327,7 +327,13 @@ bool send_msg_iservice(HANDLE pipe, const void *data, size_t size, int openvpn_execve(const struct argv *a, const struct env_set *es, const unsigned int flags); -bool impersonate_as_system(); +/* + * openvpn_swprintf() is currently only used by Windows code paths + * and when enabled for all platforms it will currently break older + * OpenBSD versions lacking vswprintf(3) support in their libc. + */ +bool +openvpn_swprintf(wchar_t* const str, const size_t size, const wchar_t* const format, ...); #endif /* ifndef OPENVPN_WIN32_H */ #endif /* ifdef _WIN32 */ -- 2.23.0.windows.1