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putty-source/unix/uxserver.c
Simon Tatham 3214563d8e Convert a lot of 'int' variables to 'bool'. 
My normal habit these days, in new code, is to treat int and bool as
_almost_ completely separate types. I'm still willing to use C's
implicit test for zero on an integer (e.g. 'if (!blob.len)' is fine,
no need to spell it out as blob.len != 0), but generally, if a
variable is going to be conceptually a boolean, I like to declare it
bool and assign to it using 'true' or 'false' rather than 0 or 1.

PuTTY is an exception, because it predates the C99 bool, and I've
stuck to its existing coding style even when adding new code to it.
But it's been annoying me more and more, so now that I've decided C99
bool is an acceptable thing to require from our toolchain in the first
place, here's a quite thorough trawl through the source doing
'boolification'. Many variables and function parameters are now typed
as bool rather than int; many assignments of 0 or 1 to those variables
are now spelled 'true' or 'false'.

I managed this thorough conversion with the help of a custom clang
plugin that I wrote to trawl the AST and apply heuristics to point out
where things might want changing. So I've even managed to do a decent
job on parts of the code I haven't looked at in years!

To make the plugin's work easier, I pushed platform front ends
generally in the direction of using standard 'bool' in preference to
platform-specific boolean types like Windows BOOL or GTK's gboolean;
I've left the platform booleans in places they _have_ to be for the
platform APIs to work right, but variables only used by my own code
have been converted wherever I found them.

In a few places there are int values that look very like booleans in
_most_ of the places they're used, but have a rarely-used third value,
or a distinction between different nonzero values that most users
don't care about. In these cases, I've _removed_ uses of 'true' and
'false' for the return values, to emphasise that there's something
more subtle going on than a simple boolean answer:
 - the 'multisel' field in dialog.h's list box structure, for which
   the GTK front end in particular recognises a difference between 1
   and 2 but nearly everything else treats as boolean
 - the 'urgent' parameter to plug_receive, where 1 vs 2 tells you
   something about the specific location of the urgent pointer, but
   most clients only care about 0 vs 'something nonzero'
 - the return value of wc_match, where -1 indicates a syntax error in
   the wildcard.
 - the return values from SSH-1 RSA-key loading functions, which use
   -1 for 'wrong passphrase' and 0 for all other failures (so any
   caller which already knows it's not loading an _encrypted private_
   key can treat them as boolean)
 - term->esc_query, and the 'query' parameter in toggle_mode in
   terminal.c, which _usually_ hold 0 for ESC[123h or 1 for ESC[?123h,
   but can also hold -1 for some other intervening character that we
   don't support.

In a few places there's an integer that I haven't turned into a bool
even though it really _can_ only take values 0 or 1 (and, as above,
tried to make the call sites consistent in not calling those values
true and false), on the grounds that I thought it would make it more
confusing to imply that the 0 value was in some sense 'negative' or
bad and the 1 positive or good:
 - the return value of plug_accepting uses the POSIXish convention of
   0=success and nonzero=error; I think if I made it bool then I'd
   also want to reverse its sense, and that's a job for a separate
   piece of work.
 - the 'screen' parameter to lineptr() in terminal.c, where 0 and 1
   represent the default and alternate screens. There's no obvious
   reason why one of those should be considered 'true' or 'positive'
   or 'success' - they're just indices - so I've left it as int.

ssh_scp_recv had particularly confusing semantics for its previous int
return value: its call sites used '<= 0' to check for error, but it
never actually returned a negative number, just 0 or 1. Now the
function and its call sites agree that it's a bool.

In a couple of places I've renamed variables called 'ret', because I
don't like that name any more - it's unclear whether it means the
return value (in preparation) for the _containing_ function or the
return value received from a subroutine call, and occasionally I've
accidentally used the same variable for both and introduced a bug. So
where one of those got in my way, I've renamed it to 'toret' or 'retd'
(the latter short for 'returned') in line with my usual modern
practice, but I haven't done a thorough job of finding all of them.

Finally, one amusing side effect of doing this is that I've had to
separate quite a few chained assignments. It used to be perfectly fine
to write 'a = b = c = TRUE' when a,b,c were int and TRUE was just a
the 'true' defined by stdbool.h, that idiom provokes a warning from
gcc: 'suggest parentheses around assignment used as truth value'!
2018-11-03 13:45:00 +00:00

653 lines
19 KiB
C
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/*
* SSH server for Unix: main program.
*
* ======================================================================
*
* This server is NOT SECURE!
*
* DO NOT DEPLOY IT IN A HOSTILE-FACING ENVIRONMENT!
*
* Its purpose is to speak the server end of everything PuTTY speaks
* on the client side, so that I can test that I haven't broken PuTTY
* when I reorganise its code, even things like RSA key exchange or
* chained auth methods which it's hard to find a server that speaks
* at all.
*
* It has no interaction with the OS's authentication system: the
* authentications it will accept are configurable by command-line
* option, and once you authenticate, it will run the connection
* protocol - including all subprocesses and shells - under the same
* Unix user id you started it under.
*
* It really is only suitable for testing the actual SSH protocol.
* Don't use it for anything more serious!
*
* ======================================================================
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <stdarg.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <pwd.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#ifndef HAVE_NO_SYS_SELECT_H
#include <sys/select.h>
#endif
#define PUTTY_DO_GLOBALS /* actually _define_ globals */
#include "putty.h"
#include "ssh.h"
#include "sshserver.h"
const char *const appname = "uppity";
void modalfatalbox(const char *p, ...)
{
va_list ap;
fprintf(stderr, "FATAL ERROR: ");
va_start(ap, p);
vfprintf(stderr, p, ap);
va_end(ap);
fputc('\n', stderr);
exit(1);
}
void nonfatal(const char *p, ...)
{
va_list ap;
fprintf(stderr, "ERROR: ");
va_start(ap, p);
vfprintf(stderr, p, ap);
va_end(ap);
fputc('\n', stderr);
}
char *platform_default_s(const char *name)
{
return NULL;
}
bool platform_default_b(const char *name, bool def)
{
return def;
}
int platform_default_i(const char *name, int def)
{
return def;
}
FontSpec *platform_default_fontspec(const char *name)
{
return fontspec_new("");
}
Filename *platform_default_filename(const char *name)
{
return filename_from_str("");
}
char *x_get_default(const char *key)
{
return NULL; /* this is a stub */
}
/*
* Our selects are synchronous, so these functions are empty stubs.
*/
uxsel_id *uxsel_input_add(int fd, int rwx) { return NULL; }
void uxsel_input_remove(uxsel_id *id) { }
void old_keyfile_warning(void) { }
void timer_change_notify(unsigned long next)
{
}
char *platform_get_x_display(void) { return NULL; }
static bool verbose;
static void log_to_stderr(const char *msg)
{
/*
* FIXME: in multi-connection proper-socket mode, prefix this with
* a connection id of some kind. We'll surely pass this in to
* sshserver.c by way of constructing a distinct LogPolicy per
* instance and making its containing structure contain the id -
* but we'll also have to arrange for those LogPolicy structs to
* be freed when the server instance terminates.
*
* For now, though, we only have one server instance, so no need.
*/
fputs(msg, stderr);
fputc('\n', stderr);
fflush(stderr);
}
static void server_eventlog(LogPolicy *lp, const char *event)
{
if (verbose)
log_to_stderr(event);
}
static void server_logging_error(LogPolicy *lp, const char *event)
{
log_to_stderr(event); /* unconditional */
}
static int server_askappend(
LogPolicy *lp, Filename *filename,
void (*callback)(void *ctx, int result), void *ctx)
{
return 2; /* always overwrite (FIXME: could make this a cmdline option) */
}
static const LogPolicyVtable server_logpolicy_vt = {
server_eventlog,
server_askappend,
server_logging_error,
};
LogPolicy server_logpolicy[1] = {{ &server_logpolicy_vt }};
struct AuthPolicy_ssh1_pubkey {
struct RSAKey key;
struct AuthPolicy_ssh1_pubkey *next;
};
struct AuthPolicy_ssh2_pubkey {
ptrlen public_blob;
struct AuthPolicy_ssh2_pubkey *next;
};
struct AuthPolicy {
struct AuthPolicy_ssh1_pubkey *ssh1keys;
struct AuthPolicy_ssh2_pubkey *ssh2keys;
int kbdint_state;
};
unsigned auth_methods(AuthPolicy *ap)
{
return (AUTHMETHOD_PUBLICKEY | AUTHMETHOD_PASSWORD | AUTHMETHOD_KBDINT |
AUTHMETHOD_TIS | AUTHMETHOD_CRYPTOCARD);
}
bool auth_none(AuthPolicy *ap, ptrlen username)
{
return false;
}
int auth_password(AuthPolicy *ap, ptrlen username, ptrlen password,
ptrlen *new_password_opt)
{
const char *PHONY_GOOD_PASSWORD = "weasel";
const char *PHONY_BAD_PASSWORD = "ferret";
if (!new_password_opt) {
/* Accept login with our preconfigured good password */
if (ptrlen_eq_string(password, PHONY_GOOD_PASSWORD))
return 1;
/* Don't outright reject the bad password, but insist on a change */
if (ptrlen_eq_string(password, PHONY_BAD_PASSWORD))
return 2;
/* Reject anything else */
return 0;
} else {
/* In a password-change request, expect the bad password as input */
if (!ptrlen_eq_string(password, PHONY_BAD_PASSWORD))
return 0;
/* Accept a request to change it to the good password */
if (ptrlen_eq_string(*new_password_opt, PHONY_GOOD_PASSWORD))
return 1;
/* Outright reject a request to change it to the same password
* as it already 'was' */
if (ptrlen_eq_string(*new_password_opt, PHONY_BAD_PASSWORD))
return 0;
/* Anything else, pretend the new pw wasn't good enough, and
* re-request a change */
return 2;
}
}
bool auth_publickey(AuthPolicy *ap, ptrlen username, ptrlen public_blob)
{
struct AuthPolicy_ssh2_pubkey *iter;
for (iter = ap->ssh2keys; iter; iter = iter->next) {
if (ptrlen_eq_ptrlen(public_blob, iter->public_blob))
return true;
}
return false;
}
struct RSAKey *auth_publickey_ssh1(
AuthPolicy *ap, ptrlen username, Bignum rsa_modulus)
{
struct AuthPolicy_ssh1_pubkey *iter;
for (iter = ap->ssh1keys; iter; iter = iter->next) {
if (!bignum_cmp(rsa_modulus, iter->key.modulus))
return &iter->key;
}
return NULL;
}
AuthKbdInt *auth_kbdint_prompts(AuthPolicy *ap, ptrlen username)
{
AuthKbdInt *aki = snew(AuthKbdInt);
switch (ap->kbdint_state) {
case 0:
aki->title = dupstr("Initial double prompt");
aki->instruction =
dupstr("First prompt should echo, second should not");
aki->nprompts = 2;
aki->prompts = snewn(aki->nprompts, AuthKbdIntPrompt);
aki->prompts[0].prompt = dupstr("Echoey prompt: ");
aki->prompts[0].echo = true;
aki->prompts[1].prompt = dupstr("Silent prompt: ");
aki->prompts[1].echo = false;
return aki;
case 1:
aki->title = dupstr("Zero-prompt step");
aki->instruction = dupstr("Shouldn't see any prompts this time");
aki->nprompts = 0;
aki->prompts = NULL;
return aki;
default:
ap->kbdint_state = 0;
return NULL;
}
}
int auth_kbdint_responses(AuthPolicy *ap, const ptrlen *responses)
{
switch (ap->kbdint_state) {
case 0:
if (ptrlen_eq_string(responses[0], "stoat") &&
ptrlen_eq_string(responses[1], "weasel")) {
ap->kbdint_state++;
return 0; /* those are the expected responses */
} else {
ap->kbdint_state = 0;
return -1;
}
break;
case 1:
return +1; /* succeed after the zero-prompt step */
default:
ap->kbdint_state = 0;
return -1;
}
}
char *auth_ssh1int_challenge(AuthPolicy *ap, unsigned method, ptrlen username)
{
/* FIXME: test returning a challenge string without \n, and ensure
* it gets printed as a prompt in its own right, without PuTTY
* making up a "Response: " prompt to follow it */
return dupprintf("This is a dummy %s challenge!\n",
(method == AUTHMETHOD_TIS ? "TIS" : "CryptoCard"));
}
bool auth_ssh1int_response(AuthPolicy *ap, ptrlen response)
{
return ptrlen_eq_string(response, "otter");
}
bool auth_successful(AuthPolicy *ap, ptrlen username, unsigned method)
{
return true;
}
static void safety_warning(FILE *fp)
{
fputs(" =================================================\n"
" THIS SSH SERVER IS NOT WRITTEN TO BE SECURE!\n"
" DO NOT DEPLOY IT IN A HOSTILE-FACING ENVIRONMENT!\n"
" =================================================\n", fp);
}
static void show_help(FILE *fp)
{
safety_warning(fp);
fputs("\n"
"usage: uppity [options]\n"
"options: --hostkey KEY SSH host key (need at least one)\n"
" --userkey KEY public key"
" acceptable for user authentication\n"
"also: uppity --help show this text\n"
" uppity --version show version information\n"
"\n", fp);
safety_warning(fp);
}
static void show_version_and_exit(void)
{
char *buildinfo_text = buildinfo("\n");
printf("%s: %s\n%s\n", appname, ver, buildinfo_text);
sfree(buildinfo_text);
exit(0);
}
const bool buildinfo_gtk_relevant = false;
static bool finished = false;
void server_instance_terminated(void)
{
/* FIXME: change policy here if we're running in a listening loop */
finished = true;
}
static bool longoptarg(const char *arg, const char *expected,
const char **val, int *argcp, char ***argvp)
{
int len = strlen(expected);
if (memcmp(arg, expected, len))
return false;
if (arg[len] == '=') {
*val = arg + len + 1;
return true;
} else if (arg[len] == '\0') {
if (--*argcp > 0) {
*val = *++*argvp;
return true;
} else {
fprintf(stderr, "%s: option %s expects an argument\n",
appname, expected);
exit(1);
}
}
return false;
}
extern const SftpServerVtable unix_live_sftpserver_vt;
int main(int argc, char **argv)
{
int *fdlist;
int fd;
int i, fdcount, fdsize, fdstate;
unsigned long now;
ssh_key **hostkeys = NULL;
int nhostkeys = 0, hostkeysize = 0;
struct RSAKey *hostkey1 = NULL;
AuthPolicy ap;
Conf *conf = conf_new();
load_open_settings(NULL, conf);
ap.kbdint_state = 0;
ap.ssh1keys = NULL;
ap.ssh2keys = NULL;
if (argc <= 1) {
/*
* We're going to terminate with an error message below,
* because there are no host keys. But we'll display the help
* as additional standard-error output, if nothing else so
* that people see the giant safety warning.
*/
show_help(stderr);
fputc('\n', stderr);
}
while (--argc > 0) {
const char *arg = *++argv;
const char *val;
if (!strcmp(arg, "--help")) {
show_help(stdout);
exit(0);
} else if (!strcmp(arg, "--version")) {
show_version_and_exit();
} else if (!strcmp(arg, "--verbose") || !strcmp(arg, "-v")) {
verbose = true;
} else if (longoptarg(arg, "--hostkey", &val, &argc, &argv)) {
Filename *keyfile;
int keytype;
const char *error;
keyfile = filename_from_str(val);
keytype = key_type(keyfile);
if (keytype == SSH_KEYTYPE_SSH2) {
struct ssh2_userkey *uk;
ssh_key *key;
uk = ssh2_load_userkey(keyfile, NULL, &error);
filename_free(keyfile);
if (!uk || !uk->key) {
fprintf(stderr, "%s: unable to load host key '%s': "
"%s\n", appname, val, error);
exit(1);
}
key = uk->key;
sfree(uk->comment);
sfree(uk);
for (i = 0; i < nhostkeys; i++)
if (ssh_key_alg(hostkeys[i]) == ssh_key_alg(key)) {
fprintf(stderr, "%s: host key '%s' duplicates key "
"type %s\n", appname, val,
ssh_key_alg(key)->ssh_id);
exit(1);
}
if (nhostkeys >= hostkeysize) {
hostkeysize = nhostkeys * 5 / 4 + 16;
hostkeys = sresize(hostkeys, hostkeysize, ssh_key *);
}
hostkeys[nhostkeys++] = key;
} else if (keytype == SSH_KEYTYPE_SSH1) {
if (hostkey1) {
fprintf(stderr, "%s: host key '%s' is a redundant "
"SSH-1 host key\n", appname, val);
exit(1);
}
hostkey1 = snew(struct RSAKey);
if (!rsa_ssh1_loadkey(keyfile, hostkey1, NULL, &error)) {
fprintf(stderr, "%s: unable to load host key '%s': "
"%s\n", appname, val, error);
exit(1);
}
} else {
fprintf(stderr, "%s: '%s' is not loadable as a "
"private key (%s)", appname, val,
key_type_to_str(keytype));
exit(1);
}
} else if (longoptarg(arg, "--userkey", &val, &argc, &argv)) {
Filename *keyfile;
int keytype;
const char *error;
keyfile = filename_from_str(val);
keytype = key_type(keyfile);
if (keytype == SSH_KEYTYPE_SSH2_PUBLIC_RFC4716 ||
keytype == SSH_KEYTYPE_SSH2_PUBLIC_OPENSSH) {
strbuf *sb = strbuf_new();
struct AuthPolicy_ssh2_pubkey *node;
void *blob;
if (!ssh2_userkey_loadpub(keyfile, NULL, BinarySink_UPCAST(sb),
NULL, &error)) {
fprintf(stderr, "%s: unable to load user key '%s': "
"%s\n", appname, val, error);
exit(1);
}
node = snew_plus(struct AuthPolicy_ssh2_pubkey, sb->len);
blob = snew_plus_get_aux(node);
memcpy(blob, sb->u, sb->len);
node->public_blob = make_ptrlen(blob, sb->len);
node->next = ap.ssh2keys;
ap.ssh2keys = node;
strbuf_free(sb);
} else if (keytype == SSH_KEYTYPE_SSH1_PUBLIC) {
strbuf *sb = strbuf_new();
BinarySource src[1];
struct AuthPolicy_ssh1_pubkey *node;
if (!rsa_ssh1_loadpub(keyfile, BinarySink_UPCAST(sb),
NULL, &error)) {
fprintf(stderr, "%s: unable to load user key '%s': "
"%s\n", appname, val, error);
exit(1);
}
node = snew(struct AuthPolicy_ssh1_pubkey);
BinarySource_BARE_INIT(src, sb->u, sb->len);
get_rsa_ssh1_pub(src, &node->key, RSA_SSH1_EXPONENT_FIRST);
node->next = ap.ssh1keys;
ap.ssh1keys = node;
strbuf_free(sb);
} else {
fprintf(stderr, "%s: '%s' is not loadable as a public key "
"(%s)\n", appname, val, key_type_to_str(keytype));
exit(1);
}
} else if (longoptarg(arg, "--sshlog", &val, &argc, &argv) ||
longoptarg(arg, "-sshlog", &val, &argc, &argv)) {
Filename *logfile = filename_from_str(val);
conf_set_filename(conf, CONF_logfilename, logfile);
filename_free(logfile);
conf_set_int(conf, CONF_logtype, LGTYP_PACKETS);
conf_set_int(conf, CONF_logxfovr, LGXF_OVR);
} else if (longoptarg(arg, "--sshrawlog", &val, &argc, &argv) ||
longoptarg(arg, "-sshrawlog", &val, &argc, &argv)) {
Filename *logfile = filename_from_str(val);
conf_set_filename(conf, CONF_logfilename, logfile);
filename_free(logfile);
conf_set_int(conf, CONF_logtype, LGTYP_SSHRAW);
conf_set_int(conf, CONF_logxfovr, LGXF_OVR);
} else {
fprintf(stderr, "%s: unrecognised option '%s'\n", appname, arg);
exit(1);
}
}
if (nhostkeys == 0 && !hostkey1) {
fprintf(stderr, "%s: specify at least one host key\n", appname);
exit(1);
}
fdlist = NULL;
fdcount = fdsize = 0;
random_ref();
/*
* Block SIGPIPE, so that we'll get EPIPE individually on
* particular network connections that go wrong.
*/
putty_signal(SIGPIPE, SIG_IGN);
sk_init();
uxsel_init();
{
Plug *plug = ssh_server_plug(
conf, hostkeys, nhostkeys, hostkey1, &ap, server_logpolicy,
&unix_live_sftpserver_vt);
ssh_server_start(plug, make_fd_socket(0, 1, -1, plug));
}
now = GETTICKCOUNT();
while (!finished) {
fd_set rset, wset, xset;
int maxfd;
int rwx;
int ret;
unsigned long next;
FD_ZERO(&rset);
FD_ZERO(&wset);
FD_ZERO(&xset);
maxfd = 0;
/* Count the currently active fds. */
i = 0;
for (fd = first_fd(&fdstate, &rwx); fd >= 0;
fd = next_fd(&fdstate, &rwx)) i++;
/* Expand the fdlist buffer if necessary. */
if (i > fdsize) {
fdsize = i + 16;
fdlist = sresize(fdlist, fdsize, int);
}
/*
* Add all currently open fds to the select sets, and store
* them in fdlist as well.
*/
fdcount = 0;
for (fd = first_fd(&fdstate, &rwx); fd >= 0;
fd = next_fd(&fdstate, &rwx)) {
fdlist[fdcount++] = fd;
if (rwx & 1)
FD_SET_MAX(fd, maxfd, rset);
if (rwx & 2)
FD_SET_MAX(fd, maxfd, wset);
if (rwx & 4)
FD_SET_MAX(fd, maxfd, xset);
}
if (toplevel_callback_pending()) {
struct timeval tv;
tv.tv_sec = 0;
tv.tv_usec = 0;
ret = select(maxfd, &rset, &wset, &xset, &tv);
} else if (run_timers(now, &next)) {
do {
unsigned long then;
long ticks;
struct timeval tv;
then = now;
now = GETTICKCOUNT();
if (now - then > next - then)
ticks = 0;
else
ticks = next - now;
tv.tv_sec = ticks / 1000;
tv.tv_usec = ticks % 1000 * 1000;
ret = select(maxfd, &rset, &wset, &xset, &tv);
if (ret == 0)
now = next;
else
now = GETTICKCOUNT();
} while (ret < 0 && errno == EINTR);
} else {
ret = select(maxfd, &rset, &wset, &xset, NULL);
}
if (ret < 0 && errno == EINTR)
continue;
if (ret < 0) {
perror("select");
exit(1);
}
for (i = 0; i < fdcount; i++) {
fd = fdlist[i];
/*
* We must process exceptional notifications before
* ordinary readability ones, or we may go straight
* past the urgent marker.
*/
if (FD_ISSET(fd, &xset))
select_result(fd, 4);
if (FD_ISSET(fd, &rset))
select_result(fd, 1);
if (FD_ISSET(fd, &wset))
select_result(fd, 2);
}
run_toplevel_callbacks();
}
exit(0);
}
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