readpass.c revision 146998 
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"
26RCSID("$OpenBSD: readpass.c,v 1.31 2004/10/29 22:53:56 djm Exp $");
27
28#include "xmalloc.h"
29#include "misc.h"
30#include "pathnames.h"
31#include "log.h"
32#include "ssh.h"
33
34static char *
35ssh_askpass(char *askpass, const char *msg)
36{
37	pid_t pid;
38	size_t len;
39	char *pass;
40	int p[2], status, ret;
41	char buf[1024];
42
43	if (fflush(stdout) != 0)
44		error("ssh_askpass: fflush: %s", strerror(errno));
45	if (askpass == NULL)
46		fatal("internal error: askpass undefined");
47	if (pipe(p) < 0) {
48		error("ssh_askpass: pipe: %s", strerror(errno));
49		return NULL;
50	}
51	if ((pid = fork()) < 0) {
52		error("ssh_askpass: fork: %s", strerror(errno));
53		return NULL;
54	}
55	if (pid == 0) {
56		seteuid(getuid());
57		setuid(getuid());
58		close(p[0]);
59		if (dup2(p[1], STDOUT_FILENO) < 0)
60			fatal("ssh_askpass: dup2: %s", strerror(errno));
61		execlp(askpass, askpass, msg, (char *) 0);
62		fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno));
63	}
64	close(p[1]);
65
66	len = ret = 0;
67	do {
68		ret = read(p[0], buf + len, sizeof(buf) - 1 - len);
69		if (ret == -1 && errno == EINTR)
70			continue;
71		if (ret <= 0)
72			break;
73		len += ret;
74	} while (sizeof(buf) - 1 - len > 0);
75	buf[len] = '\0';
76
77	close(p[0]);
78	while (waitpid(pid, &status, 0) < 0)
79		if (errno != EINTR)
80			break;
81
82	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
83		memset(buf, 0, sizeof(buf));
84		return NULL;
85	}
86
87	buf[strcspn(buf, "\r\n")] = '\0';
88	pass = xstrdup(buf);
89	memset(buf, 0, sizeof(buf));
90	return pass;
91}
92
93/*
94 * Reads a passphrase from /dev/tty with echo turned off/on.  Returns the
95 * passphrase (allocated with xmalloc).  Exits if EOF is encountered. If
96 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no
97 * tty is available
98 */
99char *
100read_passphrase(const char *prompt, int flags)
101{
102	char *askpass = NULL, *ret, buf[1024];
103	int rppflags, use_askpass = 0, ttyfd;
104
105	rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
106	if (flags & RP_USE_ASKPASS)
107		use_askpass = 1;
108	else if (flags & RP_ALLOW_STDIN) {
109		if (!isatty(STDIN_FILENO))
110			use_askpass = 1;
111	} else {
112		rppflags |= RPP_REQUIRE_TTY;
113		ttyfd = open(_PATH_TTY, O_RDWR);
114		if (ttyfd >= 0)
115			close(ttyfd);
116		else
117			use_askpass = 1;
118	}
119
120	if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL)
121		return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");
122
123	if (use_askpass && getenv("DISPLAY")) {
124		if (getenv(SSH_ASKPASS_ENV))
125			askpass = getenv(SSH_ASKPASS_ENV);
126		else
127			askpass = _PATH_SSH_ASKPASS_DEFAULT;
128		if ((ret = ssh_askpass(askpass, prompt)) == NULL)
129			if (!(flags & RP_ALLOW_EOF))
130				return xstrdup("");
131		return ret;
132	}
133
134	if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
135		if (flags & RP_ALLOW_EOF)
136			return NULL;
137		return xstrdup("");
138	}
139
140	ret = xstrdup(buf);
141	memset(buf, 'x', sizeof buf);
142	return ret;
143}
144
145int
146ask_permission(const char *fmt, ...)
147{
148	va_list args;
149	char *p, prompt[1024];
150	int allowed = 0;
151
152	va_start(args, fmt);
153	vsnprintf(prompt, sizeof(prompt), fmt, args);
154	va_end(args);
155
156	p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF);
157	if (p != NULL) {
158		/*
159		 * Accept empty responses and responses consisting
160		 * of the word "yes" as affirmative.
161		 */
162		if (*p == '\0' || *p == '\n' ||
163		    strcasecmp(p, "yes") == 0)
164			allowed = 1;
165		xfree(p);
166	}
167
168	return (allowed);
169}
170