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      1 /*
      2  * Dropbear SSH
      3  *
      4  * Copyright (c) 2002,2003 Matt Johnston
      5  * All rights reserved.
      6  *
      7  * Permission is hereby granted, free of charge, to any person obtaining a copy
      8  * of this software and associated documentation files (the "Software"), to deal
      9  * in the Software without restriction, including without limitation the rights
     10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     11  * copies of the Software, and to permit persons to whom the Software is
     12  * furnished to do so, subject to the following conditions:
     13  *
     14  * The above copyright notice and this permission notice shall be included in
     15  * all copies or substantial portions of the Software.
     16  *
     17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     23  * SOFTWARE. */
     24 
     25 #include "includes.h"
     26 #include "buffer.h"
     27 #include "dbutil.h"
     28 #include "session.h"
     29 #include "ssh.h"
     30 #include "runopts.h"
     31 
     32 #ifdef ENABLE_CLI_PASSWORD_AUTH
     33 
     34 #ifdef ENABLE_CLI_ASKPASS_HELPER
     35 /* Returns 1 if we want to use the askpass program, 0 otherwise */
     36 static int want_askpass()
     37 {
     38 	char* askpass_prog = NULL;
     39 
     40 	askpass_prog = getenv("SSH_ASKPASS");
     41 	return askpass_prog && !isatty(STDIN_FILENO) && getenv("DISPLAY");
     42 }
     43 
     44 /* returns a statically allocated password from a helper app, or NULL
     45  * on failure */
     46 static char *gui_getpass(const char *prompt) {
     47 
     48 	pid_t pid;
     49 	int p[2], maxlen, len, status;
     50 	static char buf[DROPBEAR_MAX_CLI_PASS + 1];
     51 	char* helper = NULL;
     52 
     53 	TRACE(("enter gui_getpass"))
     54 
     55 	helper = getenv("SSH_ASKPASS");
     56 	if (!helper)
     57 	{
     58 		TRACE(("leave gui_getpass: no askpass program"))
     59 		return NULL;
     60 	}
     61 
     62 	if (pipe(p) < 0) {
     63 		TRACE(("error creating child pipe"))
     64 		return NULL;
     65 	}
     66 
     67 	pid = fork();
     68 
     69 	if (pid < 0) {
     70 		TRACE(("fork error"))
     71 		return NULL;
     72 	}
     73 
     74 	if (!pid) {
     75 		/* child */
     76 		close(p[0]);
     77 		if (dup2(p[1], STDOUT_FILENO) < 0) {
     78 			TRACE(("error redirecting stdout"))
     79 			exit(1);
     80 		}
     81 		close(p[1]);
     82 		execlp(helper, helper, prompt, (char *)0);
     83 		TRACE(("execlp error"))
     84 		exit(1);
     85 	}
     86 
     87 	close(p[1]);
     88 	maxlen = sizeof(buf);
     89 	while (maxlen > 0) {
     90 		len = read(p[0], buf + sizeof(buf) - maxlen, maxlen);
     91 		if (len > 0) {
     92 			maxlen -= len;
     93 		} else {
     94 			if (errno != EINTR)
     95 				break;
     96 		}
     97 	}
     98 
     99 	close(p[0]);
    100 
    101 	while (waitpid(pid, &status, 0) < 0 && errno == EINTR)
    102 		;
    103 	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
    104 		return(NULL);
    105 
    106 	len = sizeof(buf) - maxlen;
    107 	buf[len] = '\0';
    108 	if (len > 0 && buf[len - 1] == '\n')
    109 		buf[len - 1] = '\0';
    110 
    111 	TRACE(("leave gui_getpass"))
    112 	return(buf);
    113 }
    114 #endif /* ENABLE_CLI_ASKPASS_HELPER */
    115 
    116 void cli_auth_password() {
    117 
    118 	char* password = NULL;
    119 	char prompt[80];
    120 
    121 	TRACE(("enter cli_auth_password"))
    122 	CHECKCLEARTOWRITE();
    123 
    124 	snprintf(prompt, sizeof(prompt), "%s@%s's password: ",
    125 				cli_opts.username, cli_opts.remotehost);
    126 #ifdef ENABLE_CLI_ASKPASS_HELPER
    127 	if (want_askpass())
    128 		password = gui_getpass(prompt);
    129 	else
    130 #endif
    131 		password = getpass_or_cancel(prompt);
    132 
    133 	buf_putbyte(ses.writepayload, SSH_MSG_USERAUTH_REQUEST);
    134 
    135 	buf_putstring(ses.writepayload, cli_opts.username,
    136 			strlen(cli_opts.username));
    137 
    138 	buf_putstring(ses.writepayload, SSH_SERVICE_CONNECTION,
    139 			SSH_SERVICE_CONNECTION_LEN);
    140 
    141 	buf_putstring(ses.writepayload, AUTH_METHOD_PASSWORD,
    142 			AUTH_METHOD_PASSWORD_LEN);
    143 
    144 	buf_putbyte(ses.writepayload, 0); /* FALSE - so says the spec */
    145 
    146 	buf_putstring(ses.writepayload, password, strlen(password));
    147 
    148 	encrypt_packet();
    149 	m_burn(password, strlen(password));
    150 
    151 	TRACE(("leave cli_auth_password"))
    152 }
    153 #endif	/* ENABLE_CLI_PASSWORD_AUTH */
    154