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      1 /*
      2  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     23  */
     24 
     25 #include "includes.h"
     26 RCSID("$OpenBSD: readpass.c,v 1.27 2002/03/26 15:58:46 markus Exp $");
     27 
     28 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     29 
     30 #include "xmalloc.h"
     31 #include "readpass.h"
     32 #include "pathnames.h"
     33 #include "log.h"
     34 #include "ssh.h"
     35 
     36 static char *
     37 ssh_askpass(char *askpass, const char *msg)
     38 {
     39 	pid_t pid;
     40 	size_t len;
     41 	char *pass;
     42 	int p[2], status, ret;
     43 	char buf[1024];
     44 
     45 	if (fflush(stdout) != 0)
     46 		error("ssh_askpass: fflush: %s", strerror(errno));
     47 	if (askpass == NULL)
     48 		fatal("internal error: askpass undefined");
     49 	if (pipe(p) < 0) {
     50 		error("ssh_askpass: pipe: %s", strerror(errno));
     51 		return xstrdup("");
     52 	}
     53 	if ((pid = fork()) < 0) {
     54 		error("ssh_askpass: fork: %s", strerror(errno));
     55 		return xstrdup("");
     56 	}
     57 	if (pid == 0) {
     58 		seteuid(getuid());
     59 		setuid(getuid());
     60 		close(p[0]);
     61 		if (dup2(p[1], STDOUT_FILENO) < 0)
     62 			fatal("ssh_askpass: dup2: %s", strerror(errno));
     63 		execlp(askpass, askpass, msg, (char *) 0);
     64 		fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno));
     65 	}
     66 	close(p[1]);
     67 
     68 	len = ret = 0;
     69 	do {
     70 		ret = read(p[0], buf + len, sizeof(buf) - 1 - len);
     71 		if (ret == -1 && errno == EINTR)
     72 			continue;
     73 		if (ret <= 0)
     74 			break;
     75 		len += ret;
     76 	} while (sizeof(buf) - 1 - len > 0);
     77 	buf[len] = '\0';
     78 
     79 	close(p[0]);
     80 	while (waitpid(pid, &status, 0) < 0)
     81 		if (errno != EINTR)
     82 			break;
     83 
     84 	buf[strcspn(buf, "\r\n")] = '\0';
     85 	pass = xstrdup(buf);
     86 	memset(buf, 0, sizeof(buf));
     87 	return pass;
     88 }
     89 
     90 /*
     91  * Reads a passphrase from /dev/tty with echo turned off/on.  Returns the
     92  * passphrase (allocated with xmalloc).  Exits if EOF is encountered. If
     93  * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no
     94  * tty is available
     95  */
     96 char *
     97 read_passphrase(const char *prompt, int flags)
     98 {
     99 	char *askpass = NULL, *ret, buf[1024];
    100 	int rppflags, use_askpass = 0, ttyfd;
    101 
    102 	rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
    103 	if (flags & RP_ALLOW_STDIN) {
    104 		if (!isatty(STDIN_FILENO))
    105 			use_askpass = 1;
    106 	} else {
    107 		rppflags |= RPP_REQUIRE_TTY;
    108 		ttyfd = open(_PATH_TTY, O_RDWR);
    109 		if (ttyfd >= 0)
    110 			close(ttyfd);
    111 		else
    112 			use_askpass = 1;
    113 	}
    114 
    115 	if (use_askpass && getenv("DISPLAY")) {
    116 		if (getenv(SSH_ASKPASS_ENV))
    117 			askpass = getenv(SSH_ASKPASS_ENV);
    118 		else
    119 			askpass = _PATH_SSH_ASKPASS_DEFAULT;
    120 		return ssh_askpass(askpass, prompt);
    121 	}
    122 
    123 	if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
    124 		if (flags & RP_ALLOW_EOF)
    125 			return NULL;
    126 		return xstrdup("");
    127 	}
    128 
    129 	ret = xstrdup(buf);
    130 	memset(buf, 'x', sizeof buf);
    131 	return ret;
    132 }
    133