Cleanups of the GSSAPI support. On Windows, standard GSS libraries

are now loaded from standard locations (system32 for SSPI, the
registry-stored MIT KfW install location for KfW) rather than using
the risky default DLL search path; I've therefore also added an
option to manually specify a GSS DLL we haven't heard of (which
should in principle Just Work provided it supports proper GSS-API as
specified in the RFC). The same option exists on Unix too, because
it seemed like too useful an idea to reserve to Windows. In
addition, GSSAPI is now documented, and also (unfortunately) its GUI
configuration has been moved out into a sub-subpanel on the grounds
that it was too big to fit in Auth.

[originally from svn r9003]

windows/wingss.c

@@ -12,18 +12,16 @@
 
 /* Windows code to set up the GSSAPI library list. */
 
-struct ssh_gss_library ssh_gss_libraries[2];
-int n_ssh_gss_libraries = 0;
-static int initialised = FALSE;
-
-const int ngsslibs = 2;
-const char *const gsslibnames[2] = {
-    "GSSAPI32.DLL (MIT Kerberos)",
-    "SECUR32.DLL (Microsoft SSPI)",
+const int ngsslibs = 3;
+const char *const gsslibnames[3] = {
+    "MIT Kerberos GSSAPI32.DLL",
+    "Microsoft SSPI SECUR32.DLL",
+    "User-specified GSSAPI DLL",
 };
 const struct keyval gsslibkeywords[] = {
     { "gssapi32", 0 },
     { "sspi", 1 },
+    { "custom", 2 },
 };
 
 DECL_WINDOWS_FUNCTION(static, SECURITY_STATUS,
@@ -67,22 +65,46 @@ const char *gsslogmsg = NULL;
 
 static void ssh_sspi_bind_fns(struct ssh_gss_library *lib);
 
-void ssh_gss_init(void)
+struct ssh_gss_liblist *ssh_gss_setup(const Config *cfg)
 {
     HMODULE module;
+    HKEY regkey;
+    struct ssh_gss_liblist *list = snew(struct ssh_gss_liblist);
 
-    if (initialised) return;
-    initialised = TRUE;
+    list->libraries = snewn(3, struct ssh_gss_library);
+    list->nlibraries = 0;
 
     /* MIT Kerberos GSSAPI implementation */
     /* TODO: For 64-bit builds, check for gssapi64.dll */
-    module = LoadLibrary("gssapi32.dll");
+    module = NULL;
+    if (RegOpenKey(HKEY_LOCAL_MACHINE, "SOFTWARE\\MIT\\Kerberos", &regkey)
+	== ERROR_SUCCESS) {
+	DWORD type, size;
+	LONG ret;
+	char *buffer;
+
+	/* Find out the string length */
+        ret = RegQueryValueEx(regkey, "InstallDir", NULL, &type, NULL, &size);
+
+	if (ret == ERROR_SUCCESS && type == REG_SZ) {
+	    buffer = snewn(size + 20, char);
+	    ret = RegQueryValueEx(regkey, "InstallDir", NULL,
+				  &type, buffer, &size);
+	    if (ret == ERROR_SUCCESS && type == REG_SZ) {
+		strcat(buffer, "\\bin\\gssapi32.dll");
+		module = LoadLibrary(buffer);
+	    }
+	    sfree(buffer);
+	}
+	RegCloseKey(regkey);
+    }
     if (module) {
 	struct ssh_gss_library *lib =
-	    &ssh_gss_libraries[n_ssh_gss_libraries++];
+	    &list->libraries[list->nlibraries++];
 
 	lib->id = 0;
 	lib->gsslogmsg = "Using GSSAPI from GSSAPI32.DLL";
+	lib->handle = (void *)module;
 
 #define BIND_GSS_FN(name) \
     lib->u.gssapi.name = (t_gss_##name) GetProcAddress(module, "gss_" #name)
@@ -105,10 +127,11 @@ void ssh_gss_init(void)
     module = load_system32_dll("secur32.dll");
     if (module) {
 	struct ssh_gss_library *lib =
-	    &ssh_gss_libraries[n_ssh_gss_libraries++];
+	    &list->libraries[list->nlibraries++];
 
 	lib->id = 1;
 	lib->gsslogmsg = "Using SSPI from SECUR32.DLL";
+	lib->handle = (void *)module;
 
 	GET_WINDOWS_FUNCTION(module, AcquireCredentialsHandleA);
 	GET_WINDOWS_FUNCTION(module, InitializeSecurityContextA);
@@ -120,6 +143,67 @@ void ssh_gss_init(void)
 
 	ssh_sspi_bind_fns(lib);
     }
+
+    /*
+     * Custom GSSAPI DLL.
+     */
+    module = NULL;
+    if (cfg->ssh_gss_custom.path[0]) {
+	module = LoadLibrary(cfg->ssh_gss_custom.path);
+    }
+    if (module) {
+	struct ssh_gss_library *lib =
+	    &list->libraries[list->nlibraries++];
+
+	lib->id = 2;
+	lib->gsslogmsg = dupprintf("Using GSSAPI from user-specified"
+				   " library '%s'", cfg->ssh_gss_custom.path);
+	lib->handle = (void *)module;
+
+#define BIND_GSS_FN(name) \
+    lib->u.gssapi.name = (t_gss_##name) GetProcAddress(module, "gss_" #name)
+
+        BIND_GSS_FN(delete_sec_context);
+        BIND_GSS_FN(display_status);
+        BIND_GSS_FN(get_mic);
+        BIND_GSS_FN(import_name);
+        BIND_GSS_FN(init_sec_context);
+        BIND_GSS_FN(release_buffer);
+        BIND_GSS_FN(release_cred);
+        BIND_GSS_FN(release_name);
+
+#undef BIND_GSS_FN
+
+        ssh_gssapi_bind_fns(lib);
+    }
+
+
+    return list;
+}
+
+void ssh_gss_cleanup(struct ssh_gss_liblist *list)
+{
+    int i;
+
+    /*
+     * LoadLibrary and FreeLibrary are defined to employ reference
+     * counting in the case where the same library is repeatedly
+     * loaded, so even in a multiple-sessions-per-process context
+     * (not that we currently expect ever to have such a thing on
+     * Windows) it's safe to naively FreeLibrary everything here
+     * without worrying about destroying it under the feet of
+     * another SSH instance still using it.
+     */
+    for (i = 0; i < list->nlibraries; i++) {
+	FreeLibrary((HMODULE)list->libraries[i].handle);
+	if (list->libraries[i].id == 2) {
+	    /* The 'custom' id involves a dynamically allocated message.
+	     * Note that we must cast away the 'const' to free it. */
+	    sfree((char *)list->libraries[i].gsslogmsg);
+	}
+    }
+    sfree(list->libraries);
+    sfree(list);
 }
 
 static Ssh_gss_stat ssh_sspi_indicate_mech(struct ssh_gss_library *lib,

windows/winhelp.h

@@ -108,6 +108,9 @@
 #define WINHELP_CTX_ssh_auth_pageant "ssh.auth.pageant:config-ssh-tryagent"
 #define WINHELP_CTX_ssh_auth_tis "ssh.auth.tis:config-ssh-tis"
 #define WINHELP_CTX_ssh_auth_ki "ssh.auth.ki:config-ssh-ki"
+#define WINHELP_CTX_ssh_gssapi "ssh.auth.gssapi:config-ssh-auth-gssapi"
+#define WINHELP_CTX_ssh_gssapi_delegation "ssh.auth.gssapi.delegation:config-ssh-auth-gssapi-delegation"
+#define WINHELP_CTX_ssh_gssapi_libraries "ssh.auth.gssapi.libraries:config-ssh-auth-gssapi-libraries"
 #define WINHELP_CTX_selection_buttons "selection.buttons:config-mouse"
 #define WINHELP_CTX_selection_shiftdrag "selection.shiftdrag:config-mouseshift"
 #define WINHELP_CTX_selection_rect "selection.rect:config-rectselect"

windows/winstuff.h

@@ -222,6 +222,8 @@ GLOBAL void *logctx;
 			      "All Files (*.*)\0*\0\0\0")
 #define FILTER_WAVE_FILES ("Wave Files (*.wav)\0*.WAV\0" \
 			       "All Files (*.*)\0*\0\0\0")
+#define FILTER_DYNLIB_FILES ("Dynamic Library Files (*.dll)\0*.dll\0" \
+				 "All Files (*.*)\0*\0\0\0")
 
 /*
  * On some versions of Windows, it has been known for WM_TIMER to