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example-sshpass.c
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example-sshpass.c
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/* miniexpect example.
* Copyright (C) 2014-2022 Red Hat Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/* There is a program called 'sshpass' which does roughly the same
* as this simplified example. We run ssh as a subprocess, and log
* in using the given password from the command line.
*
* The first argument is the password to send at the password prompt.
* The remaining arguments are passed to the ssh subprocess.
*
* For example:
* sshpass [-d] 123456 ssh remote.example.com
* sshpass [-d] 123456 ssh -l root remote.example.com
*
* Use the -d flag to enable debugging to stderr.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <assert.h>
#define PCRE2_CODE_UNIT_WIDTH 8
#include <pcre2.h>
#include "miniexpect.h"
static pcre2_code *compile_re (const char *rex);
static void
usage (void)
{
fprintf (stderr, "usage: sshpass [-d] PASSWORD ssh [SSH-ARGS...] HOST\n");
exit (EXIT_FAILURE);
}
int
main (int argc, char *argv[])
{
int opt;
int debug = 0;
mexp_h *h;
const char *password;
int status;
pcre2_code *password_re, *prompt_re, *hello_re;
pcre2_match_data *match_data;
match_data = pcre2_match_data_create (4, NULL);
while ((opt = getopt (argc, argv, "d")) != -1) {
switch (opt) {
case 'd':
debug = 1;
break;
default:
usage ();
}
}
if (argc-optind <= 2)
usage ();
password = argv[optind];
optind++;
printf ("starting ssh command ...\n");
h = mexp_spawnv (argv[optind], &argv[optind]);
if (h == NULL) {
perror ("mexp_spawnv: ssh");
exit (EXIT_FAILURE);
}
if (debug)
mexp_set_debug_file (h, stderr);
/* Wait for the password prompt. */
password_re = compile_re ("assword");
switch (mexp_expect (h,
(mexp_regexp[]) {
{ 100, .re = password_re },
{ 0 }
},
match_data)) {
case 100:
break;
case MEXP_EOF:
fprintf (stderr, "error: ssh closed the connection unexpectedly\n");
goto error;
case MEXP_TIMEOUT:
fprintf (stderr, "error: timeout before reaching the password prompt\n");
goto error;
case MEXP_ERROR:
perror ("mexp_expect");
goto error;
case MEXP_PCRE_ERROR:
fprintf (stderr, "error: PCRE error: %d\n", mexp_get_pcre_error (h));
goto error;
}
/* Got the password prompt, so send a password.
*
* Note use of mexp_printf_password here which is identical to
* mexp_printf except that it hides the password in debugging
* output.
*/
printf ("sending the password ...\n");
if (mexp_printf_password (h, "%s", password) == -1 ||
mexp_printf (h, "\n") == -1) {
perror ("mexp_printf");
goto error;
}
/* We have to wait for the prompt before we can send commands
* (because the ssh connection may not be fully established). If we
* get "password" again, then probably the password was wrong. This
* expect checks all these possibilities. Unfortunately since all
* prompts are a little bit different, we have to guess here.
*/
prompt_re = compile_re ("[#$]");
switch (mexp_expect (h,
(mexp_regexp[]) {
{ 100, .re = password_re },
{ 101, .re = prompt_re },
{ 0 },
},
match_data)) {
case 100: /* Password. */
fprintf (stderr, "error: ssh asked for password again, probably the password supplied is wrong\n");
goto error;
case 101: /* Prompt. */
break;
case MEXP_EOF:
fprintf (stderr, "error: ssh closed the connection unexpectedly\n");
goto error;
case MEXP_TIMEOUT:
fprintf (stderr, "error: timeout before reaching the prompt\n");
goto error;
case MEXP_ERROR:
perror ("mexp_expect");
goto error;
case MEXP_PCRE_ERROR:
fprintf (stderr, "error: PCRE error: %d\n", mexp_get_pcre_error (h));
goto error;
}
/* Send a command which will have expected output. */
printf ("sending a test command ...\n");
if (mexp_printf (h, "echo h''ello\n") == -1) {
perror ("mexp_printf");
goto error;
}
/* Wait for expected output from echo hello command. */
hello_re = compile_re ("hello");
switch (mexp_expect (h,
(mexp_regexp[]) {
{ 100, .re = hello_re },
{ 0 },
},
match_data)) {
case 100:
break;
case MEXP_EOF:
fprintf (stderr, "error: ssh closed the connection unexpectedly\n");
goto error;
case MEXP_TIMEOUT:
fprintf (stderr, "error: timeout before reading command output\n");
goto error;
case MEXP_ERROR:
perror ("mexp_expect");
goto error;
case MEXP_PCRE_ERROR:
fprintf (stderr, "error: PCRE error: %d\n", mexp_get_pcre_error (h));
goto error;
}
/* Send exit command and wait for ssh to exit. */
printf ("sending the exit command ...\n");
if (mexp_printf (h, "exit\n") == -1) {
perror ("mexp_printf");
goto error;
}
switch (mexp_expect (h, NULL, NULL)) {
case MEXP_EOF:
/* This is what we're expecting: ssh will close the connection. */
break;
case MEXP_TIMEOUT:
fprintf (stderr, "error: timeout before ssh closed the connection\n");
goto error;
case MEXP_ERROR:
perror ("mexp_expect");
goto error;
case MEXP_PCRE_ERROR:
fprintf (stderr, "error: unexpected return value from mexp_expect\n");
goto error;
}
/* Close the ssh connection. */
status = mexp_close (h);
if (status != 0) {
fprintf (stderr, "error: bad exit status from ssh subprocess (status=%d)\n",
status);
exit (EXIT_FAILURE);
}
printf ("test was successful\n");
pcre2_match_data_free (match_data);
exit (EXIT_SUCCESS);
error:
mexp_close (h);
exit (EXIT_FAILURE);
}
/* Helper function to compile a PCRE regexp. */
static pcre2_code *
compile_re (const char *rex)
{
int errorcode;
PCRE2_SIZE erroroffset;
char errormsg[256];
pcre2_code *ret;
ret = pcre2_compile ((PCRE2_SPTR) rex, PCRE2_ZERO_TERMINATED,
0, &errorcode, &erroroffset, NULL);
if (ret == NULL) {
pcre2_get_error_message (errorcode,
(PCRE2_UCHAR *) errormsg, sizeof errormsg);
fprintf (stderr, "error: "
"failed to compile regular expression '%s': "
"%s at offset %zu\n",
rex, errormsg, erroroffset);
exit (EXIT_FAILURE);
}
return ret;
}