Create, and use for all loads of system DLLs, a wrapper function

called load_system32_dll() which constructs a full pathname for the
DLL using GetSystemDirectory.

The only DLL load not covered by this change is the one for
gssapi32.dll, because that one's not in the system32 directory.

git-svn-id: svn://svn.tartarus.org/sgt/putty@8993 cda61777-01e9-0310-a592-d414129be87e

diff --git a/windows/window.c b/windows/window.c
index 18a1109..2b80430 100644 (file)
--- a/windows/window.c
+++ b/windows/window.c
@@ -5019,7 +5019,7 @@ DECL_WINDOWS_FUNCTION(static, BOOL, FlashWindowEx, (PFLASHWINFO));
 
 static void init_flashwindow(void)
 {
-    HMODULE user32_module = LoadLibrary("USER32.DLL");
+    HMODULE user32_module = load_system32_dll("user32.dll");
     GET_WINDOWS_FUNCTION(user32_module, FlashWindowEx);
 }
 

diff --git a/windows/wingss.c b/windows/wingss.c
index 5f45c98..ac0b3cf 100644 (file)
--- a/windows/wingss.c
+++ b/windows/wingss.c
@@ -102,7 +102,7 @@ void ssh_gss_init(void)
     }
 
     /* Microsoft SSPI Implementation */
-    module = LoadLibrary("secur32.dll");
+    module = load_system32_dll("secur32.dll");
     if (module) {
        struct ssh_gss_library *lib =
            &ssh_gss_libraries[n_ssh_gss_libraries++];

diff --git a/windows/winhelp.c b/windows/winhelp.c
index 078b724..a8d63a5 100644 (file)
--- a/windows/winhelp.c
+++ b/windows/winhelp.c
@@ -55,7 +55,7 @@ void init_help(void)
     } else
        chm_path = NULL;
     if (chm_path) {
-       HINSTANCE dllHH = LoadLibrary("hhctrl.ocx");
+       HINSTANCE dllHH = load_system32_dll("hhctrl.ocx");
        GET_WINDOWS_FUNCTION(dllHH, HtmlHelpA);
        if (!p_HtmlHelpA) {
            chm_path = NULL;

diff --git a/windows/winmisc.c b/windows/winmisc.c
index c7ac835..d05a07a 100644 (file)
--- a/windows/winmisc.c
+++ b/windows/winmisc.c
@@ -49,7 +49,7 @@ char *get_username(void)
        static int tried_usernameex = FALSE;
        if (!tried_usernameex) {
            /* Not available on Win9x, so load dynamically */
-           HMODULE secur32 = LoadLibrary("SECUR32.DLL");
+           HMODULE secur32 = load_system32_dll("secur32.dll");
            GET_WINDOWS_FUNCTION(secur32, GetUserNameExA);
            tried_usernameex = TRUE;
        }
@@ -105,6 +105,33 @@ BOOL init_winver(void)
     return GetVersionEx ( (OSVERSIONINFO *) &osVersion);
 }
 
+HMODULE load_system32_dll(const char *libname)
+{
+    /*
+     * Wrapper function to load a DLL out of c:\windows\system32
+     * without going through the full DLL search path. (Hence no
+     * attack is possible by placing a substitute DLL earlier on that
+     * path.)
+     */
+    static char *sysdir = NULL;
+    char *fullpath;
+    HMODULE ret;
+
+    if (!sysdir) {
+       int size = 0, len;
+       do {
+           size = 3*size/2 + 512;
+           sysdir = sresize(sysdir, size, char);
+           len = GetSystemDirectory(sysdir, size);
+       } while (len >= size);
+    }
+
+    fullpath = dupcat(sysdir, "\\", libname, NULL);
+    ret = LoadLibrary(fullpath);
+    sfree(fullpath);
+    return ret;
+}
+
 #ifdef DEBUG
 static FILE *debug_fp = NULL;
 static HANDLE debug_hdl = INVALID_HANDLE_VALUE;

diff --git a/windows/winnet.c b/windows/winnet.c
index 2740072..da291c3 100644 (file)
--- a/windows/winnet.c
+++ b/windows/winnet.c
@@ -227,9 +227,9 @@ void sk_init(void)
 #ifndef NO_IPV6
     winsock2_module =
 #endif
-        winsock_module = LoadLibrary("WS2_32.DLL");
+        winsock_module = load_system32_dll("ws2_32.dll");
     if (!winsock_module) {
-       winsock_module = LoadLibrary("WSOCK32.DLL");
+       winsock_module = load_system32_dll("wsock32.dll");
     }
     if (!winsock_module)
        fatalbox("Unable to load any WinSock library");
@@ -246,7 +246,7 @@ void sk_init(void)
        GET_WINDOWS_FUNCTION(winsock_module, gai_strerror);
     } else {
        /* Fall back to wship6.dll for Windows 2000 */
-       wship6_module = LoadLibrary("wship6.dll");
+       wship6_module = load_system32_dll("wship6.dll");
        if (wship6_module) {
 #ifdef NET_SETUP_DIAGNOSTICS
            logevent(NULL, "WSH IPv6 support detected");

diff --git a/windows/winpgnt.c b/windows/winpgnt.c
index 825c360..d592a5e 100644 (file)
--- a/windows/winpgnt.c
+++ b/windows/winpgnt.c
@@ -1972,7 +1972,7 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
        /*
         * Attempt to get the security API we need.
         */
-       advapi = LoadLibrary("ADVAPI32.DLL");
+       advapi = load_system32_dll("advapi32.dll");
        GET_WINDOWS_FUNCTION(advapi, GetSecurityInfo);
        if (!p_GetSecurityInfo) {
            MessageBox(NULL,

diff --git a/windows/winstore.c b/windows/winstore.c
index d011dbf..6e80434 100644 (file)
--- a/windows/winstore.c
+++ b/windows/winstore.c
@@ -497,7 +497,7 @@ static HANDLE access_random_seed(int action)
         * on older versions of Windows if we cared enough.
         * However, the invocation below requires IE5+ anyway,
         * so stuff that. */
-       shell32_module = LoadLibrary("SHELL32.DLL");
+       shell32_module = load_system32_dll("shell32.dll");
        GET_WINDOWS_FUNCTION(shell32_module, SHGetFolderPathA);
        tried_shgetfolderpath = TRUE;
     }

diff --git a/windows/winstuff.h b/windows/winstuff.h
index 99bda10..2317748 100644 (file)
--- a/windows/winstuff.h
+++ b/windows/winstuff.h
@@ -446,6 +446,7 @@ void show_help(HWND hwnd);
  */
 extern OSVERSIONINFO osVersion;
 BOOL init_winver(void);
+HMODULE load_system32_dll(const char *libname);
 
 /*
  * Exports from sizetip.c.