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putty-source/windows/plink.c
Simon Tatham a2ff884512 Richer data type for interactive prompt results. 
All the seat functions that request an interactive prompt of some kind
to the user - both the main seat_get_userpass_input and the various
confirmation dialogs for things like host keys - were using a simple
int return value, with the general semantics of 0 = "fail", 1 =
"proceed" (and in the case of seat_get_userpass_input, answers to the
prompts were provided), and -1 = "request in progress, wait for a
callback".

In this commit I change all those functions' return types to a new
struct called SeatPromptResult, whose primary field is an enum
replacing those simple integer values.

The main purpose is that the enum has not three but _four_ values: the
"fail" result has been split into 'user abort' and 'software abort'.
The distinction is that a user abort occurs as a result of an
interactive UI action, such as the user clicking 'cancel' in a dialog
box or hitting ^D or ^C at a terminal password prompt - and therefore,
there's no need to display an error message telling the user that the
interactive operation has failed, because the user already knows,
because they _did_ it. 'Software abort' is from any other cause, where
PuTTY is the first to know there was a problem, and has to tell the
user.

We already had this 'user abort' vs 'software abort' distinction in
other parts of the code - the SSH backend has separate termination
functions which protocol layers can call. But we assumed that any
failure from an interactive prompt request fell into the 'user abort'
category, which is not true. A couple of examples: if you configure a
host key fingerprint in your saved session via the SSH > Host keys
pane, and the server presents a host key that doesn't match it, then
verify_ssh_host_key would report that the user had aborted the
connection, and feel no need to tell the user what had gone wrong!
Similarly, if a password provided on the command line was not
accepted, then (after I fixed the semantics of that in the previous
commit) the same wrong handling would occur.

So now, those Seat prompt functions too can communicate whether the
user or the software originated a connection abort. And in the latter
case, we also provide an error message to present to the user. Result:
in those two example cases (and others), error messages should no
longer go missing.

Implementation note: to avoid the hassle of having the error message
in a SeatPromptResult being a dynamically allocated string (and hence,
every recipient of one must always check whether it's non-NULL and
free it on every exit path, plus being careful about copying the
struct around), I've instead arranged that the structure contains a
function pointer and a couple of parameters, so that the string form
of the message can be constructed on demand. That way, the only users
who need to free it are the ones who actually _asked_ for it in the
first place, which is a much smaller set.

(This is one of the rare occasions that I regret not having C++'s
extra features available in this code base - a unique_ptr or
shared_ptr to a string would have been just the thing here, and the
compiler would have done all the hard work for me of remembering where
to insert the frees!)
2021-12-28 18:08:31 +00:00

550 lines
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/*
* PLink - a Windows command-line (stdin/stdout) variant of PuTTY.
*/
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdarg.h>
#include "putty.h"
#include "storage.h"
#include "tree234.h"
#include "security-api.h"
void cmdline_error(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
console_print_error_msg_fmt_v("plink", fmt, ap);
va_end(ap);
exit(1);
}
static HANDLE inhandle, outhandle, errhandle;
static struct handle *stdin_handle, *stdout_handle, *stderr_handle;
static handle_sink stdout_hs, stderr_hs;
static StripCtrlChars *stdout_scc, *stderr_scc;
static BinarySink *stdout_bs, *stderr_bs;
static DWORD orig_console_mode;
static Backend *backend;
static LogContext *logctx;
static Conf *conf;
static void plink_echoedit_update(Seat *seat, bool echo, bool edit)
{
/* Update stdin read mode to reflect changes in line discipline. */
DWORD mode;
mode = ENABLE_PROCESSED_INPUT;
if (echo)
mode = mode | ENABLE_ECHO_INPUT;
else
mode = mode & ~ENABLE_ECHO_INPUT;
if (edit)
mode = mode | ENABLE_LINE_INPUT;
else
mode = mode & ~ENABLE_LINE_INPUT;
SetConsoleMode(inhandle, mode);
}
static size_t plink_output(
Seat *seat, SeatOutputType type, const void *data, size_t len)
{
bool is_stderr = type != SEAT_OUTPUT_STDOUT;
BinarySink *bs = is_stderr ? stderr_bs : stdout_bs;
put_data(bs, data, len);
return handle_backlog(stdout_handle) + handle_backlog(stderr_handle);
}
static bool plink_eof(Seat *seat)
{
handle_write_eof(stdout_handle);
return false; /* do not respond to incoming EOF with outgoing */
}
static SeatPromptResult plink_get_userpass_input(Seat *seat, prompts_t *p)
{
SeatPromptResult spr;
spr = cmdline_get_passwd_input(p);
if (spr.kind == SPRK_INCOMPLETE)
spr = console_get_userpass_input(p);
return spr;
}
static bool plink_seat_interactive(Seat *seat)
{
return (!*conf_get_str(conf, CONF_remote_cmd) &&
!*conf_get_str(conf, CONF_remote_cmd2) &&
!*conf_get_str(conf, CONF_ssh_nc_host));
}
static const SeatVtable plink_seat_vt = {
.output = plink_output,
.eof = plink_eof,
.sent = nullseat_sent,
.banner = nullseat_banner_to_stderr,
.get_userpass_input = plink_get_userpass_input,
.notify_session_started = nullseat_notify_session_started,
.notify_remote_exit = nullseat_notify_remote_exit,
.notify_remote_disconnect = nullseat_notify_remote_disconnect,
.connection_fatal = console_connection_fatal,
.update_specials_menu = nullseat_update_specials_menu,
.get_ttymode = nullseat_get_ttymode,
.set_busy_status = nullseat_set_busy_status,
.confirm_ssh_host_key = console_confirm_ssh_host_key,
.confirm_weak_crypto_primitive = console_confirm_weak_crypto_primitive,
.confirm_weak_cached_hostkey = console_confirm_weak_cached_hostkey,
.is_utf8 = nullseat_is_never_utf8,
.echoedit_update = plink_echoedit_update,
.get_x_display = nullseat_get_x_display,
.get_windowid = nullseat_get_windowid,
.get_window_pixel_size = nullseat_get_window_pixel_size,
.stripctrl_new = console_stripctrl_new,
.set_trust_status = console_set_trust_status,
.can_set_trust_status = console_can_set_trust_status,
.has_mixed_input_stream = console_has_mixed_input_stream,
.verbose = cmdline_seat_verbose,
.interactive = plink_seat_interactive,
.get_cursor_position = nullseat_get_cursor_position,
};
static Seat plink_seat[1] = {{ &plink_seat_vt }};
static DWORD main_thread_id;
/*
* Short description of parameters.
*/
static void usage(void)
{
printf("Plink: command-line connection utility\n");
printf("%s\n", ver);
printf("Usage: plink [options] [user@]host [command]\n");
printf(" (\"host\" can also be a PuTTY saved session name)\n");
printf("Options:\n");
printf(" -V print version information and exit\n");
printf(" -pgpfp print PGP key fingerprints and exit\n");
printf(" -v show verbose messages\n");
printf(" -load sessname Load settings from saved session\n");
printf(" -ssh -telnet -rlogin -raw -serial\n");
printf(" force use of a particular protocol\n");
printf(" -ssh-connection\n");
printf(" force use of the bare ssh-connection protocol\n");
printf(" -P port connect to specified port\n");
printf(" -l user connect with specified username\n");
printf(" -batch disable all interactive prompts\n");
printf(" -proxycmd command\n");
printf(" use 'command' as local proxy\n");
printf(" -sercfg configuration-string (e.g. 19200,8,n,1,X)\n");
printf(" Specify the serial configuration (serial only)\n");
printf("The following options only apply to SSH connections:\n");
printf(" -pwfile file login with password read from specified file\n");
printf(" -D [listen-IP:]listen-port\n");
printf(" Dynamic SOCKS-based port forwarding\n");
printf(" -L [listen-IP:]listen-port:host:port\n");
printf(" Forward local port to remote address\n");
printf(" -R [listen-IP:]listen-port:host:port\n");
printf(" Forward remote port to local address\n");
printf(" -X -x enable / disable X11 forwarding\n");
printf(" -A -a enable / disable agent forwarding\n");
printf(" -t -T enable / disable pty allocation\n");
printf(" -1 -2 force use of particular SSH protocol version\n");
printf(" -4 -6 force use of IPv4 or IPv6\n");
printf(" -C enable compression\n");
printf(" -i key private key file for user authentication\n");
printf(" -noagent disable use of Pageant\n");
printf(" -agent enable use of Pageant\n");
printf(" -no-trivial-auth\n");
printf(" disconnect if SSH authentication succeeds trivially\n");
printf(" -noshare disable use of connection sharing\n");
printf(" -share enable use of connection sharing\n");
printf(" -hostkey keyid\n");
printf(" manually specify a host key (may be repeated)\n");
printf(" -sanitise-stderr, -sanitise-stdout, "
"-no-sanitise-stderr, -no-sanitise-stdout\n");
printf(" do/don't strip control chars from standard "
"output/error\n");
printf(" -no-antispoof omit anti-spoofing prompt after "
"authentication\n");
printf(" -m file read remote command(s) from file\n");
printf(" -s remote command is an SSH subsystem (SSH-2 only)\n");
printf(" -N don't start a shell/command (SSH-2 only)\n");
printf(" -nc host:port\n");
printf(" open tunnel in place of session (SSH-2 only)\n");
printf(" -sshlog file\n");
printf(" -sshrawlog file\n");
printf(" log protocol details to a file\n");
printf(" -logoverwrite\n");
printf(" -logappend\n");
printf(" control what happens when a log file already exists\n");
printf(" -shareexists\n");
printf(" test whether a connection-sharing upstream exists\n");
exit(1);
}
static void version(void)
{
char *buildinfo_text = buildinfo("\n");
printf("plink: %s\n%s\n", ver, buildinfo_text);
sfree(buildinfo_text);
exit(0);
}
size_t stdin_gotdata(struct handle *h, const void *data, size_t len, int err)
{
if (err) {
char buf[4096];
FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, err, 0,
buf, lenof(buf), NULL);
buf[lenof(buf)-1] = '\0';
if (buf[strlen(buf)-1] == '\n')
buf[strlen(buf)-1] = '\0';
fprintf(stderr, "Unable to read from standard input: %s\n", buf);
cleanup_exit(0);
}
noise_ultralight(NOISE_SOURCE_IOLEN, len);
if (backend_connected(backend)) {
if (len > 0) {
backend_send(backend, data, len);
return backend_sendbuffer(backend);
} else {
backend_special(backend, SS_EOF, 0);
return 0;
}
} else
return 0;
}
void stdouterr_sent(struct handle *h, size_t new_backlog, int err, bool close)
{
if (close) {
CloseHandle(outhandle);
CloseHandle(errhandle);
outhandle = errhandle = INVALID_HANDLE_VALUE;
}
if (err) {
char buf[4096];
FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, err, 0,
buf, lenof(buf), NULL);
buf[lenof(buf)-1] = '\0';
if (buf[strlen(buf)-1] == '\n')
buf[strlen(buf)-1] = '\0';
fprintf(stderr, "Unable to write to standard %s: %s\n",
(h == stdout_handle ? "output" : "error"), buf);
cleanup_exit(0);
}
if (backend_connected(backend)) {
backend_unthrottle(backend, (handle_backlog(stdout_handle) +
handle_backlog(stderr_handle)));
}
}
const bool share_can_be_downstream = true;
const bool share_can_be_upstream = true;
const unsigned cmdline_tooltype =
TOOLTYPE_HOST_ARG |
TOOLTYPE_HOST_ARG_CAN_BE_SESSION |
TOOLTYPE_HOST_ARG_PROTOCOL_PREFIX |
TOOLTYPE_HOST_ARG_FROM_LAUNCHABLE_LOAD;
static bool sending;
static bool plink_mainloop_pre(void *vctx, const HANDLE **extra_handles,
size_t *n_extra_handles)
{
if (!sending && backend_sendok(backend)) {
stdin_handle = handle_input_new(inhandle, stdin_gotdata, NULL,
0);
sending = true;
}
return true;
}
static bool plink_mainloop_post(void *vctx, size_t extra_handle_index)
{
if (sending)
handle_unthrottle(stdin_handle, backend_sendbuffer(backend));
if (!backend_connected(backend) &&
handle_backlog(stdout_handle) + handle_backlog(stderr_handle) == 0)
return false; /* we closed the connection */
return true;
}
int main(int argc, char **argv)
{
int exitcode;
bool errors;
bool use_subsystem = false;
bool just_test_share_exists = false;
enum TriState sanitise_stdout = AUTO, sanitise_stderr = AUTO;
const struct BackendVtable *vt;
dll_hijacking_protection();
/*
* Initialise port and protocol to sensible defaults. (These
* will be overridden by more or less anything.)
*/
settings_set_default_protocol(PROT_SSH);
settings_set_default_port(22);
/*
* Process the command line.
*/
conf = conf_new();
do_defaults(NULL, conf);
settings_set_default_protocol(conf_get_int(conf, CONF_protocol));
settings_set_default_port(conf_get_int(conf, CONF_port));
errors = false;
{
/*
* Override the default protocol if PLINK_PROTOCOL is set.
*/
char *p = getenv("PLINK_PROTOCOL");
if (p) {
const struct BackendVtable *vt = backend_vt_from_name(p);
if (vt) {
settings_set_default_protocol(vt->protocol);
settings_set_default_port(vt->default_port);
conf_set_int(conf, CONF_protocol, vt->protocol);
conf_set_int(conf, CONF_port, vt->default_port);
}
}
}
while (--argc) {
char *p = *++argv;
int ret = cmdline_process_param(p, (argc > 1 ? argv[1] : NULL),
1, conf);
if (ret == -2) {
fprintf(stderr,
"plink: option \"%s\" requires an argument\n", p);
errors = true;
} else if (ret == 2) {
--argc, ++argv;
} else if (ret == 1) {
continue;
} else if (!strcmp(p, "-batch")) {
console_batch_mode = true;
} else if (!strcmp(p, "-s")) {
/* Save status to write to conf later. */
use_subsystem = true;
} else if (!strcmp(p, "-V") || !strcmp(p, "--version")) {
version();
} else if (!strcmp(p, "--help")) {
usage();
} else if (!strcmp(p, "-pgpfp")) {
pgp_fingerprints();
exit(1);
} else if (!strcmp(p, "-shareexists")) {
just_test_share_exists = true;
} else if (!strcmp(p, "-sanitise-stdout") ||
!strcmp(p, "-sanitize-stdout")) {
sanitise_stdout = FORCE_ON;
} else if (!strcmp(p, "-no-sanitise-stdout") ||
!strcmp(p, "-no-sanitize-stdout")) {
sanitise_stdout = FORCE_OFF;
} else if (!strcmp(p, "-sanitise-stderr") ||
!strcmp(p, "-sanitize-stderr")) {
sanitise_stderr = FORCE_ON;
} else if (!strcmp(p, "-no-sanitise-stderr") ||
!strcmp(p, "-no-sanitize-stderr")) {
sanitise_stderr = FORCE_OFF;
} else if (!strcmp(p, "-no-antispoof")) {
console_antispoof_prompt = false;
} else if (*p != '-') {
strbuf *cmdbuf = strbuf_new();
while (argc > 0) {
if (cmdbuf->len > 0)
put_byte(cmdbuf, ' '); /* add space separator */
put_dataz(cmdbuf, p);
if (--argc > 0)
p = *++argv;
}
conf_set_str(conf, CONF_remote_cmd, cmdbuf->s);
conf_set_str(conf, CONF_remote_cmd2, "");
conf_set_bool(conf, CONF_nopty, true); /* command => no tty */
strbuf_free(cmdbuf);
break; /* done with cmdline */
} else {
fprintf(stderr, "plink: unknown option \"%s\"\n", p);
errors = true;
}
}
if (errors)
return 1;
if (!cmdline_host_ok(conf)) {
usage();
}
prepare_session(conf);
/*
* Perform command-line overrides on session configuration.
*/
cmdline_run_saved(conf);
/*
* Apply subsystem status.
*/
if (use_subsystem)
conf_set_bool(conf, CONF_ssh_subsys, true);
/*
* Select protocol. This is farmed out into a table in a
* separate file to enable an ssh-free variant.
*/
vt = backend_vt_from_proto(conf_get_int(conf, CONF_protocol));
if (vt == NULL) {
fprintf(stderr,
"Internal fault: Unsupported protocol found\n");
return 1;
}
if (vt->flags & BACKEND_NEEDS_TERMINAL) {
fprintf(stderr,
"Plink doesn't support %s, which needs terminal emulation\n",
vt->displayname_lc);
return 1;
}
sk_init();
if (p_WSAEventSelect == NULL) {
fprintf(stderr, "Plink requires WinSock 2\n");
return 1;
}
/*
* Plink doesn't provide any way to add forwardings after the
* connection is set up, so if there are none now, we can safely set
* the "simple" flag.
*/
if (conf_get_int(conf, CONF_protocol) == PROT_SSH &&
!conf_get_bool(conf, CONF_x11_forward) &&
!conf_get_bool(conf, CONF_agentfwd) &&
!conf_get_str_nthstrkey(conf, CONF_portfwd, 0))
conf_set_bool(conf, CONF_ssh_simple, true);
logctx = log_init(console_cli_logpolicy, conf);
if (just_test_share_exists) {
if (!vt->test_for_upstream) {
fprintf(stderr, "Connection sharing not supported for this "
"connection type (%s)'\n", vt->displayname_lc);
return 1;
}
if (vt->test_for_upstream(conf_get_str(conf, CONF_host),
conf_get_int(conf, CONF_port), conf))
return 0;
else
return 1;
}
if (restricted_acl()) {
lp_eventlog(console_cli_logpolicy,
"Running with restricted process ACL");
}
inhandle = GetStdHandle(STD_INPUT_HANDLE);
outhandle = GetStdHandle(STD_OUTPUT_HANDLE);
errhandle = GetStdHandle(STD_ERROR_HANDLE);
/*
* Turn off ECHO and LINE input modes. We don't care if this
* call fails, because we know we aren't necessarily running in
* a console.
*/
GetConsoleMode(inhandle, &orig_console_mode);
SetConsoleMode(inhandle, ENABLE_PROCESSED_INPUT);
/*
* Pass the output handles to the handle-handling subsystem.
* (The input one we leave until we're through the
* authentication process.)
*/
stdout_handle = handle_output_new(outhandle, stdouterr_sent, NULL, 0);
stderr_handle = handle_output_new(errhandle, stdouterr_sent, NULL, 0);
handle_sink_init(&stdout_hs, stdout_handle);
handle_sink_init(&stderr_hs, stderr_handle);
stdout_bs = BinarySink_UPCAST(&stdout_hs);
stderr_bs = BinarySink_UPCAST(&stderr_hs);
/*
* Decide whether to sanitise control sequences out of standard
* output and standard error.
*
* If we weren't given a command-line override, we do this if (a)
* the fd in question is pointing at a console, and (b) we aren't
* trying to allocate a terminal as part of the session.
*
* (Rationale: the risk of control sequences is that they cause
* confusion when sent to a local console, so if there isn't one,
* no problem. Also, if we allocate a remote terminal, then we
* sent a terminal type, i.e. we told it what kind of escape
* sequences we _like_, i.e. we were expecting to receive some.)
*/
if (sanitise_stdout == FORCE_ON ||
(sanitise_stdout == AUTO && is_console_handle(outhandle) &&
conf_get_bool(conf, CONF_nopty))) {
stdout_scc = stripctrl_new(stdout_bs, true, L'\0');
stdout_bs = BinarySink_UPCAST(stdout_scc);
}
if (sanitise_stderr == FORCE_ON ||
(sanitise_stderr == AUTO && is_console_handle(errhandle) &&
conf_get_bool(conf, CONF_nopty))) {
stderr_scc = stripctrl_new(stderr_bs, true, L'\0');
stderr_bs = BinarySink_UPCAST(stderr_scc);
}
/*
* Start up the connection.
*/
winselcli_setup(); /* ensure event object exists */
{
char *error, *realhost;
/* nodelay is only useful if stdin is a character device (console) */
bool nodelay = conf_get_bool(conf, CONF_tcp_nodelay) &&
(GetFileType(GetStdHandle(STD_INPUT_HANDLE)) == FILE_TYPE_CHAR);
error = backend_init(vt, plink_seat, &backend, logctx, conf,
conf_get_str(conf, CONF_host),
conf_get_int(conf, CONF_port),
&realhost, nodelay,
conf_get_bool(conf, CONF_tcp_keepalives));
if (error) {
fprintf(stderr, "Unable to open connection:\n%s", error);
sfree(error);
return 1;
}
ldisc_create(conf, NULL, backend, plink_seat);
sfree(realhost);
}
main_thread_id = GetCurrentThreadId();
sending = false;
cli_main_loop(plink_mainloop_pre, plink_mainloop_post, NULL);
exitcode = backend_exitcode(backend);
if (exitcode < 0) {
fprintf(stderr, "Remote process exit code unavailable\n");
exitcode = 1; /* this is an error condition */
}
cleanup_exit(exitcode);
return 0; /* placate compiler warning */
}
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