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55cea187e9
putty-source/unix/uxserver.c
Simon Tatham b54147de4b Remove some redundant variables and assignments. 
This fixes a batch of clang-analyzer warnings of the form 'you
declared / assigned this variable and then never use it'. It doesn't
fix _all_ of them - some are there so that when I add code in the
future _it_ can use the variable without me having to remember to
start setting it - but these are the ones I thought it would make the
code better instead of worse to fix.
2018-12-01 17:00:01 +00:00

651 lines
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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;
}
int main(int argc, char **argv)
{
int *fdlist;
int fd;
int i, 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;
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.
*/
int 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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