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Rewrite some manual char-buffer-handling code.

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In the course of recent refactorings I noticed a couple of cases where
we were doing old-fashioned preallocation of a char array with some
conservative maximum size, then writing into it via *p++ or similar
and hoping we got the calculation right.

Now we have strbuf and dupcat, so we shouldn't ever have to do that.
Fixed as many cases as I could find by searching for allocations of
the form 'snewn(foo, char)'.

Particularly worth a mention was the Windows GSSAPI setup code, which
was directly using the Win32 Registry API, and looks much more legible
using the windows/utils/registry.c wrappers. (But that was why I had
to enhance them in the previous commit so as to be able to open
registry keys read-only: without that, the open operation would
actually fail on this key, which is not user-writable.)

Also unix/askpass.c, which was doing a careful reallocation of its
buffer to avoid secrets being left behind in the vacated memory -
which is now just a matter of ensuring we called strbuf_new_nm().
This commit is contained in:
Simon Tatham
2022-09-13 15:00:26 +01:00
parent 7339e00f4a
commit 6cf6682c54
13 changed files with 174 additions and 291 deletions
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87
windows/gss.c
View File

@ -118,7 +118,6 @@ static void add_library_to_never_unload_tree(HMODULE module)
struct ssh_gss_liblist *ssh_gss_setup(Conf *conf)
{
HMODULE module;
HKEY regkey;
struct ssh_gss_liblist *list = snew(struct ssh_gss_liblist);
char *path;
static HMODULE kernel32_module;
@ -137,55 +136,47 @@ struct ssh_gss_liblist *ssh_gss_setup(Conf *conf)
/* MIT Kerberos GSSAPI implementation */
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, (LPBYTE)buffer, &size);
if (ret == ERROR_SUCCESS && type == REG_SZ) {
strcat (buffer, "\\bin");
if(p_AddDllDirectory) {
/* Add MIT Kerberos' path to the DLL search path,
* it loads its own DLLs further down the road */
wchar_t *dllPath =
dup_mb_to_wc(DEFAULT_CODEPAGE, 0, buffer);
p_AddDllDirectory(dllPath);
sfree(dllPath);
}
strcat (buffer, "\\gssapi"MIT_KERB_SUFFIX".dll");
module = LoadLibraryEx (buffer, NULL,
LOAD_LIBRARY_SEARCH_SYSTEM32 |
LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR |
LOAD_LIBRARY_SEARCH_USER_DIRS);
/*
* The MIT Kerberos DLL suffers an internal segfault
* for some reason if you unload and reload one within
* the same process. So, make sure that after we load
* this library, we never free it.
*
* Or rather: after we've loaded it once, if any
* _further_ load returns the same module handle, we
* immediately free it again (to prevent the Windows
* API's internal reference count growing without
* bound). But on the other hand we never free it in
* ssh_gss_cleanup.
*/
if (library_is_in_never_unload_tree(module))
FreeLibrary(module);
add_library_to_never_unload_tree(module);
HKEY regkey = open_regkey_ro(HKEY_LOCAL_MACHINE,
"SOFTWARE\\MIT\\Kerberos");
if (regkey) {
char *installdir = get_reg_sz(regkey, "InstallDir");
if (installdir) {
char *bindir = dupcat(installdir, "\\bin");
if(p_AddDllDirectory) {
/* Add MIT Kerberos' path to the DLL search path,
* it loads its own DLLs further down the road */
wchar_t *dllPath = dup_mb_to_wc(DEFAULT_CODEPAGE, 0, bindir);
p_AddDllDirectory(dllPath);
sfree(dllPath);
}
sfree(buffer);
char *dllfile = dupcat(bindir, "\\gssapi"MIT_KERB_SUFFIX".dll");
module = LoadLibraryEx(dllfile, NULL,
LOAD_LIBRARY_SEARCH_SYSTEM32 |
LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR |
LOAD_LIBRARY_SEARCH_USER_DIRS);
/*
* The MIT Kerberos DLL suffers an internal segfault for
* some reason if you unload and reload one within the
* same process. So, make sure that after we load this
* library, we never free it.
*
* Or rather: after we've loaded it once, if any _further_
* load returns the same module handle, we immediately
* free it again (to prevent the Windows API's internal
* reference count growing without bound). But on the
* other hand we never free it in ssh_gss_cleanup.
*/
if (library_is_in_never_unload_tree(module))
FreeLibrary(module);
add_library_to_never_unload_tree(module);
sfree(dllfile);
sfree(bindir);
sfree(installdir);
}
RegCloseKey(regkey);
close_regkey(regkey);
}
if (module) {
struct ssh_gss_library *lib =